KR20190035834A - Rolled roll outer material and rolled composite roll - Google Patents

Abstract

A roll outer layer material and a rolled composite roll having remarkably improved abrasion resistance are provided. W: 25 to 70% by weight, Co: 5 to 45% by weight in the surface of the outer layer material at a position corresponding to the maximum diameter at the time of rolling, and the W content is an inclined composition falling in the radial direction from the outer peripheral side toward the inner peripheral side. Co-based alloy which contains 0.6 to 3.5% of C, 0.05 to 3% of Si, 0.05 to 3% of Mn and 1 to 15% of Mo and the balance of inevitable impurities And a roll outer layer material having a composition. The roll outer layer material is preferably a centrifugal casting agent.

Description

Rolled roll outer material and rolled composite roll

The present invention relates to a rolled outer layer material for rolling and suitable for hot rolling or cold rolling as a first embodiment, and to a composite roll for rolling using the roll outer layer material, particularly to improvement of abrasion resistance.

Further, the present invention relates to a rolled outer layer material for rolling and suitable for hot rolling or cold rolling, and a composite roll for rolling using the roll outer layer material, and particularly relates to improvement of abrasion resistance and reduction of rolling load .

[First Embodiment]

First, in the first embodiment, in recent years, the progress of the rolling technology of the steel sheet is remarkable, and accordingly, the use environment of the rolling roll becomes more severe. Especially in recent years, the production amount of steel sheets, such as high-strength steel sheets and thin-walled products, which require a large rolling load and require excellent surface quality, is increasing.

For this reason, in a work roll for cold rolling, excellent abrasion resistance and high hardness to cope with it are required. The improvement in abrasion resistance is generally achieved by high alloying of the roll material. However, there is a case in which high alloying results in deterioration of grindability or increase in damage at the time of a roll accident (deterioration in resistance to accidents) Therefore, it is necessary to use a material having both grinding ability and internal resistance. Further, in order to produce a steel sheet having excellent surface quality, it is necessary to make the surface properties of the rolls in direct contact with the steel sheet to be homogeneous and fine. Specifically, as the roll material, cast iron having a high degree of cleanliness and a fine microstructure, It is required to use cast steel.

Further, in the work roll for hot rolling, the occurrence of abrasion and surface roughness of the rolls impairs rolling schedule restrictions on the material and dimensions of the product, and it is also difficult to reduce the frequency of the roll exchange. The use of durability of rolls is one of the problems of productivity improvement and cost reduction. For this reason, in hot rolling work rolls, it is required to suppress the occurrence of abrasion and surface roughening, and to improve the roll content.

From this point of view, it is strongly desired to improve the properties of the rolling roll used, in particular to improve the abrasion resistance. The improvement of the wear resistance in rolling rolls is an important issue directly related to the improvement of steel sheet quality and the improvement of productivity in the production of steel sheet.

As described in Non-Patent Document 1 and Non-Patent Document 2, for example, the outer layer composition is made to have a composition similar to that of a high-speed tool steel, and a large amount of hard carbide is dispersed High-speed tool steel rolls have been developed which have significantly improved abrasion resistance. Further, for example, Patent Document 1 discloses a composite roll for hot rolling, in which an outer layer is formed around a steel core core by a continuous casting method. In the composite roll for hot rolling as described in Patent Document 1, the outer layer material contains 1.0 to 4.0% of C, 3.0% or less of Si, 1.5% or less of Mn, 2 to 10% of Cr, 9% , W: not more than 20%, V: 2 to 15%, P: not more than 0.08%, S: not more than 0.06%, B: not more than 0.0500%, and the balance Fe and inevitable impurities , And a structure containing 5 to 30% of granular carbide and 6% or more of non-particulate carbide, and the hardness of the base phase has a Vickers hardness (Hv) of 550 or more. It is also stated that the outer layer material may further contain 5.0% or less of Ni, 5.0% or less of Co, and 5.0% or less of Nb. Thus, the presence of the non-particulate carbide at a predetermined amount or more suppresses the growth to the deep portion of the roll even when cracks occur, improves the heat cracking resistance, It is said that the abrasion resistance is good in that carbide is contained.

Such a high speed tool steel roll outer layer material needs to disperse a large amount of light carbide in the matrix in order to improve abrasion resistance. However, the light carbide produced by the high speed tool steel composition generally has a smaller specific gravity than the base, and is liable to cause segregation during casting. Particularly, in the centrifugal casting method, which is a typical casting method of roll outer layer material, since a product having excellent productivity and economical efficiency is used, a lightweight phase is liable to be accumulated and segregated inside by centrifugal force. Therefore, Has been considered to be difficult.

However, Patent Document 2 discloses a rolling roll outer layer material which is excellent in abrasion resistance and crack resistance without occurrence of segregation even when a centrifugal casting method is applied. , Ni: not more than 5.5%, Cr: 5.5 to 12.0%, Mo: 2.0 to 8.0%, V: 3.0 to 10.0%, Nb: 0.5 to 7.0% And V are contained so that the content of Nb, V and C satisfy a specific relationship, and the ratio of Nb and V falls within a specific range.

Patent Document 3 discloses a ferritic stainless steel which comprises 1.5 to 3.5% of C, 1.5% or less of Si, 1.2% or less of Mn, 5.5 to 12.0% of Cr, 2.0 to 8.0% of Mo, 3.0 to 10.0% , And Nb: 0.5 to 7.0%, and Nb and V satisfy the specific relationship in the content of Nb, V and C, and further the ratio of Nb and V falls within a specific range . With such a composition, segregation in the rolled outer layer material is suppressed even when the centrifugal casting method is applied, and wear resistance and crack resistance are improved, thereby contributing to improvement of productivity of hot rolling.

Further, Patent Document 4 describes a centrifugal casting composite roll. The centrifugal casting composite roll described in Patent Document 4 is composed of an outer layer and an inner layer of cast iron or cast steel and the outer layer contains 1.0 to 3.0% of C, 0.1 to 3.0% of Si, 0.1 to 2.0% of Mn, An alloy component containing 2.0 to 10.0% of Cr, 0.1 to 10.0% of Mo, 1.0 to 10.0% of V, 0.1 to 10.0% of W and satisfying Mo + W of 10.0% or less and the balance of Fe and inevitable impurities As shown in Fig. In the technique described in Patent Document 4, the crystallization of the M ₆ C -type carbide, which easily causes aggregation and segregation, is suppressed, so that the outer layer can be obtained in which only the MC-type + M ₇ C ₃ -type carbide is precipitated, It is said that it can do.

Further, for example, Patent Document 5 describes a centrifugal cast outer layer material for a rolling roll. The centrifugal cast outer layer material for rolling roll described in Patent Document 5 has a composition containing 4.5 to 9% of C, 0.1 to 3.5% of Si, 0.1 to 3.5% of Mn and 18 to 40% of V in terms of mass% Has a structure in which the MC carbide is dispersed in an area ratio of 20 to 60% in an area ratio on a base having a Vickers hardness of HV550 to 900. In the technique described in Patent Document 5, when the centrifugal casting segregation, in which the MC carbide having a small specific gravity is concentrated on the inner surface side, is positively used and is cut so as to leave only the layer in which the MC carbide is concentrated after centrifugal casting, Can be reliably formed at a low cost.

As a material having excellent abrasion resistance, a cemented carbide has been known for a long time. As the cemented carbide, for example, tungsten carbide (WC) is usually molded and sintered together with Co as a binder as described in Non-Patent Document 3.

As a technique of applying such a cemented carbide to a rolling roll, there are disclosed in Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9, Patent Document 10 and the like.

Patent Document 6 discloses a tungsten carbide-based cemented carbide for a hot rolling roll and a hot rolling guide roll. The technique described in Patent Document 6 is characterized in that the weight ratio of chromium to the sum of cobalt and nickel is 1/1 to 1/99, the weight ratio of cobalt to nickel is 9/1 to 1/9, the tungsten carbide is 88 wt% Cobalt and a tungsten carbide based alloy in which the total sum of nickel and chromium is 12 to 65 wt%. Patent Document 6 describes an example in which such a cemented carbide is applied to a roll for hot rolling of a normal steel material (wire rod).

Patent Document 7 describes a hot rolled wire roll made of a cemented carbide. In the technique described in Patent Document 7, the cemented carbide to be used is made of a WC having an average particle diameter of 1 탆 to 5 탆, or a hard carbide phase in which a part of WC is replaced by 10% or less by weight of at least one of TiC, TaC and NbC And a ternary alloy-bonded phase, wherein Cr in the bonded phase is 0.30 or less with respect to the sum of Ni and Co, 0.05 or more with respect to the total bonded phase, and further Ni is a sum of Ni and Co Of 0.33 to 0.90, and the polarization potential is 0.3V or more with respect to the cooling industrial water. Such a cemented carbide alloy makes it possible to provide a hot rolled wire rod having excellent surface roughness.

Patent Document 8 discloses a cemented carbide formed by using a WC raw material powder having an average particle diameter of 3 占 퐉 or less and an intermediate layer made of an outer layer made of a cemented carbide bonded to the outer periphery of an inner layer made of a steel or iron- Rolled composite roll made of an alloy is disclosed. It is said that the content of the WC particles in the intermediate layer is preferably 70% or less by weight. As a result, it is possible to obtain a roll for rolling a cemented carbide alloy having excellent abrasion resistance and high reliability in terms of strength.

Patent Document 9 discloses a roll for rolling a cemented carbide alloy having an outer layer formed of a cemented carbide excellent in abrasion resistance and an intermediate layer made of a cemented carbide containing WC and Ni and having high strength and reliability have.

Further, Patent Document 10 discloses a method of producing a steel sheet having an inner layer made of a steel-based material or an iron-based material with R = σc (1-ν) / Eα (where σc: flexural strength, v: Poisson's ratio, And the outer layer made of a cemented carbide satisfying a thermal impact coefficient R of not less than 400, which is expressed by E: Young's modulus, alpha: coefficient of thermal expansion), are bonded to each other. As a result, the abrasion resistance and the surface roughness of the roll are improved, and occurrence and progress of thermal cracking at the time of rolling accident are suppressed.

[Second embodiment]

Further, in the second embodiment, in recent years, the progress of the rolling technology of the steel sheet is remarkable, and accordingly, the use environment of the rolling roll is markedly severer. Especially in recent years, the production amount of steel sheets, such as high-strength steel sheets and thin-walled products, which require a large rolling load and require excellent surface quality, is increasing.

Therefore, in cold rolling work rolls, excellent wear resistance and high hardness to cope with it are required. Improvement of abrasion resistance is generally achieved by high alloying of the roll material. However, due to high alloying, there are cases where the grinding property is worsened or the damage is increased in the case of a roll accident (lowering of internal resistance) It is necessary to make with material which combines. Further, in order to produce a steel sheet having excellent surface quality, it is necessary to make the surface properties of the rolls in direct contact with the steel sheet to be homogeneous and fine. Specifically, as the roll material, cast iron having a high degree of cleanliness and a fine microstructure, It is required to use cast steel.

Further, in the work roll for hot rolling, the occurrence of abrasion and surface roughness of the rolls impairs rolling schedule restrictions on the material and dimensions of the product, and it is also difficult to reduce the frequency of the roll exchange. Is one of the problems of productivity improvement and cost reduction. For this reason, in hot rolling work rolls, it is required to suppress the occurrence of abrasion and surface roughening, and to improve the roll content.

From this point of view, it is strongly desired to improve the properties of the rolling roll used, in particular to improve the abrasion resistance. Improvement of wear resistance in a rolling roll has become an important issue directly related to improvement of steel sheet quality and productivity in the production of steel sheet.

Further, in the automobile field in recent years, from the viewpoint of improving the fuel economy, the weight of the vehicle body is being improved by the application of the high-strength material, and it is thought that the application of the high-strength material is further advanced in the future. When the high strength material is rolled, the surface layer portion of the rolling work roll contacting with the rolled material is elastically deformed to increase the contact area (or contact arc length) between the surface layer of the rolling work roll and the rolled material, The rolling pressure acting on the rolling work roll from the pressurized steel strip increases. When the rolling load becomes excessive, there is a problem that the precision of the dimension of the rolled material is lowered, and the minimum rolling thickness is limited. Therefore, there is a demand for a rolled roll outer material having a high Young's modulus which is hardly elastically deformed .

Regarding the demand for improvement of the abrasion resistance of the rolling roll, for example, as described in Non-Patent Document 1 and Non-Patent Document 2, the composition of the outer layer is made similar to the composition of the high speed tool steel and the hard carbide is dispersed in a large amount, A remarkably improved high speed tool steel roll has been developed. Further, for example, Patent Document 1 discloses a composite roll for hot rolling, in which an outer layer is formed around a forcible core material by a continuous casting method. In the composite roll for hot rolling as described in Patent Document 1, the outer layer material contains 1.0 to 4.0% of C, 3.0% or less of Si, 1.5% or less of Mn, 2 to 10% of Cr, 9% , W: not more than 20%, V: 2 to 15%, P: not more than 0.08%, S: not more than 0.06%, B: not more than 0.0500%, and the balance Fe and inevitable impurities 5 to 30% of granular carbide and 6% or more of non-particulate carbide, and has a known hardness of Vickers hardness (HV) of 550 or more. It is also stated that the outer layer material may further contain 5.0% or less of Ni, 5.0% or less of Co, and 5.0% or less of Nb. As a result, even when cracks are generated due to the presence of a predetermined amount or more of the non-particulate carbide, it is suppressed from advancing to the core of the roll, the heat crack resistance is improved, and since the VC carbide is included, have.

Such a high-speed tool steel roll outer layer material needs to disperse a large amount of light carbide in the matrix for improving abrasion resistance. However, the light carbide produced by the high-speed tool steel composition generally has a specific gravity smaller than that of the base and tends to cause segregation during casting. Particularly, in the centrifugal casting method, which is a typical casting method for roll outer layer material, since the productivity and the economical efficiency are excellent, the lightweight phase is easy to accumulate and segregate inside by centrifugal force. Therefore, the centrifugal casting method of high- It has been considered difficult.

However, Patent Document 2 discloses a rolling roll outer layer material which is excellent in abrasion resistance and crack resistance without occurrence of segregation even when a centrifugal casting method is applied. , Ni: not more than 5.5%, Cr: 5.5 to 12.0%, Mo: 2.0 to 8.0%, V: 3.0 to 10.0%, Nb: 0.5 to 7.0% And V satisfy the specific relationship between the contents of Nb, V and C, and further the ratio of Nb and V falls within a specific range.

Patent Document 3 discloses a ferritic stainless steel which comprises 1.5 to 3.5% of C, 1.5% or less of Si, 1.2% or less of Mn, 5.5 to 12.0% of Cr, 2.0 to 8.0% of Mo, 3.0 to 10.0% , And Nb: 0.5 to 7.0%, and Nb and V satisfy the specific relationship in the content of Nb, V and C, and further the ratio of Nb and V falls within a specific range . With such a composition, segregation in the roll outer layer material is suppressed even when the centrifugal casting method is applied, and wear resistance and crack resistance are improved, contributing greatly to productivity improvement of hot rolling.

Further, Patent Document 4 describes a centrifugal casting composite roll. The centrifugal casting composite roll described in Patent Document 4 is composed of an outer layer and an inner layer of cast iron or cast steel and the outer layer contains 1.0 to 3.0% of C, 0.1 to 3.0% of Si, 0.1 to 2.0% of Mn, An alloy component containing 2.0 to 10.0% of Cr, 0.1 to 10.0% of Mo, 1.0 to 10.0% of V, 0.1 to 10.0% of W and satisfying Mo + W of 10.0% or less and the balance of Fe and inevitable impurities As shown in Fig. According to the technique described in Patent Document 4, the crystallization of the M ₆ C type carbide, which easily causes aggregation and segregation, is suppressed, and the outer layer can be formed only of the MC type + M ₇ C ₃ type carbide and can be produced by the centrifugal casting method .

Further, for example, Patent Document 5 describes a centrifugal cast outer layer material for a rolling roll. The centrifugal cast outer layer material for rolling roll described in Patent Document 5 has a composition containing 4.5 to 9% of C, 0.1 to 3.5% of Si, 0.1 to 3.5% of Mn and 18 to 40% of V in terms of mass% , It is supposed that the MC carbide has a structure in which 20 to 60% of the MC ratio is dispersed on a base having a Vickers hardness of HV550 to 900. In the technique described in Patent Document 5, when the centrifugal casting segregation, in which the MC carbide having a small specific gravity is concentrated on the inner surface side, is positively used and is cut so as to leave only the layer in which the MC carbide is concentrated after centrifugal casting, Can be reliably formed at a low cost.

As a material having a very excellent wear resistance and a high Young's modulus, a cemented carbide has been known for a long time. As the cemented carbide, for example, tungsten carbide (WC) is generally molded and sintered together with Co as a binder as described in Non-Patent Document 3.

As a technique of applying such a cemented carbide to a rolling roll, there are disclosed in Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9, Patent Document 10 and the like.

Patent Document 6 discloses a tungsten carbide-based cemented carbide for a hot rolling roll and a hot rolling guide roll. The technique described in Patent Document 6 is characterized in that the weight ratio of chromium to the sum of cobalt and nickel is 1/1 to 1/99, the weight ratio of cobalt to nickel is 9/1 to 1/9, the tungsten carbide is 88 wt% Cobalt and a tungsten carbide based alloy in which the total sum of nickel and chromium is 12 to 65 wt%. Patent Document 6 describes an example in which such a cemented carbide is applied to a roll for hot rolling of ordinary steel (wire).

Further, Patent Document 7 describes a hot rolled material rolling roll made of a cemented carbide. In the technique described in Patent Document 7, the cemented carbide to be used is made of a WC having an average particle diameter of 1 탆 to 5 탆, or a hard carbide phase in which a part of WC is replaced by 10% or less by weight of at least one of TiC, TaC and NbC And a ternary alloy-bonded phase, wherein Cr in the bonded phase is 0.30 or less with respect to the sum of Ni and Co, 0.05 or more with respect to the total bonded phase, and further Ni is a sum of Ni and Co Of 0.33 to 0.90, and the polarization potential is 0.3V or more with respect to the cooling general industrial water. By using such a cemented carbide alloy, it is said that the hot rolled wire rod is excellent in inner surface roughness.

Further, Patent Document 8 discloses that an outer layer made of a cemented carbide is bonded to the outer periphery of an inner layer made of a steel or ferrous material with an intermediate layer interposed therebetween, and the intermediate layer is made of a WC raw material powder having an average particle size of 3 m or less Rolled composite roll comprising a cemented carbide is disclosed. It is said that the content of the WC particles in the intermediate layer is preferably 70% or less by weight. As a result, it is possible to obtain a roll for rolling a cemented carbide alloy having excellent abrasion resistance and high reliability in terms of strength.

Patent Document 9 discloses a roll for rolling a cemented carbide alloy having an outer layer made of a cemented carbide excellent in abrasion resistance and having an intermediate layer made of a cemented carbide containing WC and Ni and having high strength and reliability have.

Patent Document 10 discloses a method of producing a steel sheet having a structure in which R = σc (1-ν) / Eα (where σc is the transverse strength, ν is the Poisson's ratio, E is the Young's modulus, And the outer layer made of a cemented carbide satisfying a thermal impact coefficient R of 400 or more. As a result, the abrasion resistance and the surface roughness of the roll are improved, and occurrence and progress of thermal cracking at the time of rolling accident are suppressed.

Japanese Laid-Open Patent Publication No. 04-141553 Japanese Laid-Open Patent Publication No. 04-365836 Japanese Laid-Open Patent Publication No. 05-1350 Japanese Patent Application Laid-Open No. 08-60289 International Application WO2006 / 030795 Japanese Patent Publication No. 57-6502 Japanese Patent Publication No. 58-39906 Japanese Patent Application Laid-Open No. 2004-243341 Japanese Laid-Open Patent Publication No. 2006-175456 Japanese Patent Application Laid-Open No. 2004-268140

 Kamata and others: Hitachi Criticism Vol. 72, No. 5 (1990), p69  Hashimoto et al .: Iron and Steel Research No. 338 (1990), p62  MONMA Kaizo Journal of the Steel and Materials Society (1981), p368  Matsunaga, et al.: Analysis technology for roll length (1999), p11  Hashimoto et al., Shinnetsu Tetsugibo 355 (1995), p76

[First Embodiment]

However, in the first embodiment, in the technique described in Patent Document 1, there is a problem that productivity is low and cost is high because an outer layer is formed by a continuous growth method around a forced core. Further, in the technologies described in Patent Documents 2 and 3, the content of Nb, V and C is limited to a specific range and the MC type carbide is uniformly dispersed to improve abrasion resistance and crack resistance. However, in reality, since M ₇ C ₃ type carbides or M ₆ C type carbides containing a large amount of Cr or Mo exist in a considerable amount, further improvement of the characteristics is considered to be sufficient from the viewpoint of uniformly dispersing the MC type carbide I can not. Further, in the technique described in Patent Document 4, the Mo + W content is limited to 10.0% or less in order to suppress the crystallization of the M ₆ C type carbide likely to cause aggregation or segregation, and thereby, the roll outer layer material can be produced by the centrifugal casting method . However, restricting the Mo and W contents poses a problem with respect to the demand for further improvement of wear resistance in recent years.

Further, in the production of the roll for rolling using the centrifugal casting method, since the amount of carbide forming elements such as Mo, V, and W is increased, the formed carbide is lighter, so that the formed carbide is accumulated on the inner surface side and agglomerates at the boundary with the inner layer , There is a concern that the bonding strength of the boundary is lowered.

In the technique described in Patent Document 5, although the abrasion resistance of the roll is improved, it is necessary to work to remove the outer surface side region where the MC type carbide is less, but the yield is very low and the advantage of the centrifugal casting method of high productivity and low cost Is lost.

The technology described in Patent Document 6 and Patent Document 7 which use cemented carbide targets a small roll for wire rolling and this technology is applied to the production of a large roll such as a roll for cold rolling or a roll for hot rolling It is difficult to apply it directly to. In addition, since HIP treatment, which is an expensive process, is required in comparison with a centrifugal casting product, there is a problem that a manufacturing cost is high even if it is a small product.

The techniques described in Patent Document 8, Patent Document 9 and Patent Document 10 which use a cemented carbide as an outer layer material of a roll for plate rolling all assume the sintering-HIP method for forming the outer layer material, Problems remain. In addition, these techniques use soft Co or Ni as the binder, and there is a problem that punch flaws (concave portions) are likely to be generated at the time of rolling, so that these techniques have not been put to practical use.

The present invention solves the above problems of the prior art in the first embodiment and aims to provide a rolled outer layer material which is remarkably improved in abrasion resistance and is superior in abrasion resistance and a composite roll for rolling using the same, .

[Second embodiment]

Further, in the second embodiment, in the technique described in Patent Document 1, since the outer layer is formed around the forcible core material by the continuous growth method, there is a problem that the productivity is low and the cost is high. Further, in the technologies described in Patent Documents 2 and 3, the content of Nb, V and C is limited to a specific range and the MC type carbide is uniformly dispersed to improve abrasion resistance and crack resistance. However, in reality, since there are also a considerable amount of M ₇ C ₃ type carbides or M ₆ C type carbides containing a large amount of Cr or Mo, further improvement of the characteristics is sufficient only in view of uniformly dispersing the MC type carbide Can not. Further, in the technique described in Patent Document 4, the Mo + W content is limited to 10.0% or less in order to suppress the crystallization of the M ₆ C type carbide likely to cause aggregation or segregation, and thereby, the roll outer layer material can be produced by the centrifugal casting method . However, restricting the Mo and W contents poses a problem with respect to the demand for further improvement of wear resistance in recent years.

Further, in the production of the roll for rolling using the centrifugal casting method, the increment of the carbide forming element such as Mo, V, W or the like is smaller than that of the molten metal which forms the base because the specific gravity of the generated VC- The light carbides of the system aggregate on the inner surface side and flocculate at the boundary with the inner layer, and there is a possibility that the bonding strength of the boundary is lowered.

In the technique described in Patent Document 5, although the abrasion resistance of the roll is improved, it is necessary to work to remove the outer surface side region where the MC type carbide is less, but the yield is very low and the advantage of the centrifugal casting method of high productivity and low cost Is lost.

The technology described in Patent Document 6 and Patent Document 7 which use cemented carbide targets a small roll for wire rolling and this technology is applied to the production of a large roll such as a roll for cold rolling or a roll for hot rolling It is difficult to apply it directly to. In addition, since HIP treatment, which is an expensive process, is required in comparison with a centrifugal casting product, there is a problem that a manufacturing cost is high even if it is a small product.

The techniques described in Patent Document 8, Patent Document 9 and Patent Document 10 which use a cemented carbide as an outer layer material of a roll for plate rolling all assume the sintering-HIP method for forming the outer layer material, Problems remain. In addition, these techniques use soft Co or Ni as the binder, and there is a problem that punch flaws (concave portions) are likely to be generated at the time of rolling, so that these techniques have not been put to practical use.

A second aspect of the present invention is to solve the problems of the prior art in the second embodiment and to provide a rolled outer material excellent in abrasion resistance and reduction in rolling load and remarkably improved in abrasion resistance and Young's modulus compared with the prior art, At low cost.

[First Embodiment]

In the first embodiment, in order to achieve the above object, the inventors of the present invention have found that a rolling roll having a very high abrasion resistance equivalent to that of a cemented carbide can be manufactured by a centrifugal casting method having excellent productivity and economy The conditions were studied carefully. As a result, if the hard carbide can be densified and concentrated on the outer surface side of the roll using the molten metal and the centrifugal force acting on the crystalized phase during centrifugal casting, the abrasion resistance of the roll for centrifugal casting- I thought of something that could be improved significantly. Further, in order to densify and concentrate the hard carbide on the outer surface side of the roll at the time of centrifugal casting by the further examination, a carbide having a specific gravity higher than that of the liquid phase is removed from the liquid phase in which centrifugal force acts, I came to the idea that I could find a condition that I could express myself as.

That is, when a carbide having a specific gravity larger than that of the liquid phase is poured out in the liquid phase in which the centrifugal force acts, centrifugal force in the peripheral direction acts on the carbide. At this time, if the carbide and its surrounding γ phase do not undergo eutectic solidification and the carbide can be crystallized directly from the liquid phase as a crystal phase, since the periphery of the carbide is still liquid, the carbide can easily move to the outer side, .

As a carbide forming element satisfying such a condition, attention has been paid to W having a large specific gravity, and it has been thought that a large amount of W is contained. By repeating various casting experiments,

(1) When a W-Co based alloy containing a large amount of W with a large specific gravity is a melt containing 0.6% by mass or more of C, the M ₆ C type carbide in which W is concentrated appears as a crystal phase,

(2) By centrifugally casting such a W-Co-base alloy melt, it is possible to obtain a structure in which the M ₆ C type carbide crystallized as a primary crystal segregates at a high concentration on the outer surface side of the outer layer material

.

Further, when the Fe-based alloy is used as the alloy to be used, it is recognized that the formation of the W-based process carbide is promoted, and the appearance of the M ₆ C-type carbide as the crystal phase is inhibited. Further, by using a W-Co based alloy which increases the carbon content of the alloy to be used, formation of a W-based process carbide is suppressed and a large amount of M ₆ C-type carbide in which W is concentrated in the molten metal appears as a primary crystal , And when the C content is less than 0.6 mass%, the superfine M ₆ C type carbide does not appear. On the other hand, if the C content exceeds 3 mass%, the liquidus temperature becomes excessively high and melting and casting become difficult, The MC type carbide and the M ₂ C type carbide, which are liable to be very fragile, grow and coarsen, thereby easily causing roll breakage.

The present invention has been completed based on such recognition by further reviewing the present invention. That is, the gist of the present invention is as follows.

(1) A W-Co based alloy rolled outer material having an inclined composition in which the W content decreases in the radial direction from the outer peripheral side to the inner peripheral side of the roll and the surface of the outer peripheral material at the position corresponding to the maximum diameter at the time of rolling is Co: 5 to 45%, C: 0.6 to 3.5%, Si: 0.05 to 3%, Mn: 0.05 to 3% and Mo: 1 to 15% And the remainder is inevitable impurities.

(2) In addition to the above composition, at least one selected from the group consisting of Fe: 5 to 40%, Cr: 0.1 to 10%, V: 0.1 to 6% and Nb: 0.1 to 3% (1). ≪ / RTI >

(3) The rolled roll outer material according to (1) or (2), further comprising, in mass%, Ni: 0.05 to 3% in addition to the above composition.

(4) The rolled roll outer layer material according to any one of (1) to (3), wherein the roll outer layer material is a centrifugal casting agent.

(5) A composite roll for rolling comprising an outer layer and an inner layer welded and integrated with the outer layer, wherein the outer layer is the rolling roll outer layer material according to any one of (1) to (3).

(6) A composite roll for rolling comprising an outer layer, an intermediate layer welded and integrated with the outer layer, and an inner layer welded and integrated with the intermediate layer, wherein the outer layer is the rolling roll outer layer material described in any one of (1) Composite roll for rolling.

(7) The composite roll for rolling as described in (5) or (6), wherein the outer layer is a centrifugal casting agent.

[Second embodiment]

In the second embodiment, in order to achieve the above-mentioned object, the inventors of the present invention have found that a rolling roll having a very high wear resistance and a high Young's modulus equivalent to those of a cemented carbide is manufactured by a centrifugal casting method having excellent productivity and economy We have studied the conditions to make it possible. As a result, when the hard carbide can be densified and concentrated on the outer surface side of the roll by using the molten metal and the centrifugal force acting on the crystallization phase during centrifugal casting, the abrasion resistance of the centrifugal casting roll is remarkably improved I was thinking about what I could do. Further, in order to densify and concentrate the hard carbide on the outer surface side of the roll at the time of centrifugal casting by the further examination, a carbide having a specific gravity higher than that of the liquid phase can be crystallized as a primary crystal I came to the thought that I should find the condition. Further, in order to improve the Young's modulus, it has been found that it is preferable to increase the amount of W and Mo employed in the base, in addition to densifying and thickening the hard carbide on the outer surface side of the roll.

That is, when a carbide having a specific gravity larger than that of the liquid phase is poured out in the liquid phase in which the centrifugal force acts, centrifugal force in the peripheral direction acts on the carbide. At this time, if the carbide and its surrounding gamma phase do not solidify and the carbide can be crystallized directly from the liquid phase as a superpowder, since the periphery of the carbide is still liquid, the carbide can be easily moved and accumulated on the outer circumferential side .

As a carbide forming element satisfying such a condition, attention has been paid to W having a large specific gravity, and it has been thought that a large amount of W is contained. By repeating various casting experiments,

(1) When a W-Co based alloy containing a large amount of W with a large specific gravity is a melt containing 0.6% by mass or more of C, the M ₆ C type carbide in which W is concentrated appears as a crystal phase,

(2) By centrifugally casting such a W-Co-base alloy melt, it is possible to obtain a structure in which the M ₆ C type carbide crystallized as a primary crystal segregates at a high concentration on the outer surface side of the outer layer material

.

Further, when the Fe-based alloy is used as the alloy to be used, it is recognized that the formation of the W-based process carbide is promoted, and the appearance of the M ₆ C-type carbide as the crystal phase is inhibited. Further, by using a W-Co based alloy which increases the carbon content of the alloy to be used, formation of a W-based process carbide is suppressed and a large amount of M ₆ C-type carbide in which W is concentrated in the molten metal appears as a primary crystal , And when the C content is less than 0.6 mass%, the superfine M ₆ C type carbide does not appear. On the other hand, if the C content exceeds 3 mass%, the liquidus temperature becomes excessively high and melting and casting become difficult, It is recognized that the MC type carbide and M ₂ C type carbide, which are liable to be very fragile, grow and coarsen and thus easily cause roll breakage.

The present invention has been completed based on such recognition, with further examination being added. That is, the gist of the present invention is as follows.

(1) An outer layer material for rolling a W-Co based alloy roll, which has an inclined composition in which the W content decreases in the radial direction from the outer peripheral side to the inner peripheral side of the roll and is a surface layer at the position corresponding to the maximum diameter at the time of rolling The steel sheet according to any one of claims 1 to 5, wherein the ash content includes 25 to 70% of W, 5 to 45% of Co, 0.6 to 3.5% of C, 0.05 to 3% of Si, 0.05 to 3% of Mn, and 1 to 15% , And the content of W, Co, Mo and Fe satisfies the following formula [1], and the remainder is inevitable impurities.

(% W +% Mo) / (% Co +% Fe)? 9.0 [1]

Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element.

(2) The rolling outer layer material as set forth in (1), wherein the Young's modulus of the outer layer material to be the surface layer at the position corresponding to the maximum diameter at the time of rolling is 270 ㎬ to 500..

(3) A ferritic stainless steel according to (1) or (2), further comprising, in mass%, 5 to 40% of Fe, 0.1 to 10% of Cr, 0.1 to 6% of V, % Of at least one member selected from the group consisting of iron and iron.

(4) The rolling outer layer material according to any one of (1) to (3), further comprising, in mass%, Ni: 0.05 to 3% in addition to the above composition.

(5) The roll outer material as set forth in any one of (1) to (4), wherein the rolling roll outer material is a centrifugal casting.

(6) an outer layer and an inner layer welded and integrated with the outer layer, wherein the outer layer is made of a W-Co based alloy and has a W content decreasing in the radial direction from the outer peripheral side to the inner peripheral side of the roll And the outer layer material serving as a surface layer at a position corresponding to the maximum diameter at the time of rolling is used in an amount of 25 to 70% of W, 5 to 45% of Co, 0.6 to 3.5% of C, 0.05 to 3% of Si, , Mn: 0.05 to 3%, and Mo: 1 to 15%, and the content of W, Co, Mo and Fe satisfies the following formula [1] and the remainder is inevitable impurities Compound roll.

(% W +% Mo) / (% Co +% Fe)? 9.0 [1]

Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element.

(7) The composite roll for rolling according to (6), wherein the Young's modulus of the outer layer material which becomes the surface layer at the position corresponding to the maximum diameter at the time of rolling is not less than 270 ㎬ and not more than 500..

(8) The steel according to (6) or (7), further comprising, in mass%, 5 to 40% of Fe, 0.1 to 10% of Cr, 0.1 to 6% of V, % Of the total weight of the composite roll for rolling.

(9) The composite roll for rolling according to any one of (6) to (8), further comprising, in mass%, Ni: 0.05 to 3% in addition to the above composition.

(10) outer layer, an intermediate layer welded and integrated with the outer layer, and an inner layer welded integrally with the intermediate layer, wherein the outer layer is made of a W-Co based alloy and has a W content from the outer peripheral side to the inner peripheral side And the outer layer material serving as a surface layer at a position corresponding to the maximum diameter at the time of rolling is composed of 25 to 70% of W, 5 to 45% of Co, 0.6 to 3.5% of C, Wherein the content of W, Co, Mo and Fe is in the range of 0.05 to 3%, Si: 0.05 to 3%, Mn: 0.05 to 3%, Mo: 1 to 15% And the remainder is inevitable impurities.

group

(% W +% Mo) / (% Co +% Fe)? 9.0 [1]

Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element.

(11) The composite roll for rolling according to (10), wherein the Young's modulus of the outer layer material as the surface layer at the position corresponding to the maximum diameter at the time of rolling is 270 占 ㎬ to 500 占 ㎬.

(12) The steel according to the above (10) or (11), further comprising, in mass%, 5 to 40% of Fe, 0.1 to 10% of Cr, 0.1 to 6% of V, % Of the total weight of the composite roll for rolling.

(13) The composite roll for rolling according to any one of (10) to (12), further comprising, in mass%, Ni: 0.05 to 3% in addition to the above composition.

(14) The composite roll for rolling according to any one of (6) to (13), wherein the outer layer is a centrifugal casting.

In the first embodiment, according to the present invention, it is possible to produce a rolling roll, particularly a centrifugal casting roll rolling roll, which is suitable as a roll for hot rolling or cold rolling, and which is remarkably excellent in abrasion resistance, And it has a remarkable effect in the industry.

In the second embodiment, according to the present invention, a rolling roll, particularly a centrifugal casting roll rolling roll, which is suitable as a roll for hot rolling or cold rolling and which is remarkably excellent in abrasion resistance and rolling load reducing effect, In addition, it can be easily produced and exhibits remarkable effects in the industry.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a photograph showing the structure of a scanning electron microscope in Example 1. Fig. (a) is Sleeve No. 13 (test material No. 13), and (b) is Sleeve No. 5 (test material No. 5).
2 is an explanatory diagram schematically showing an outline of a wear test in the first embodiment.
3 is a schematic view for explaining an example of a composite roll in the present invention.
4 is a schematic view of a composite roll section for explaining an example of a composite roll for rolling comprising an outer layer according to the present invention and an inner layer welded and integrated with the outer layer according to the present invention.
5 is a schematic view of a composite roll section for explaining an example of a composite roll for rolling comprising an outer layer according to the present invention, an intermediate layer welded and integrated with the outer layer, and an inner layer welded and integrated with the intermediate layer.
6 is a photograph of a tissue showing a scanning electron microscopic structure in Example 2. Fig. (a) is the sleeve No. 13, and (b) is the sleeve No. 5.
7 is an explanatory diagram schematically showing the outline of the wear test in the second embodiment.
8 is a schematic view of a composite roll for rolling load evaluation in Example 2. Fig.

Hereinafter, the first embodiment and the second embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]

The rolled roll outer layer material of the present invention is a centrifugal casting agent. The " rolled outer layer material for rolling casting master batch " as used herein means a rolled outer layer material in a state of being manufactured using a centrifugal casting method which has been conventionally used as a method for producing rolling rolls. The roll outer material (rolled outer layer material for rolling the "centrifugal casting agent") produced by the centrifugal casting method has been conventionally used as a "water" as the roll for rolling produced by other manufacturing methods It is difficult to distinguish the roll outer layer material for rolling and the roll outer layer material for the "centrifugal casting roll" by structure or characteristics, and it is impractical.

The roll outer layer material of the present invention is made of a W-Co based alloy and has an inclined composition in which the W content decreases in the radial direction from the outer peripheral side to the inner peripheral side of the roll, Wherein the steel contains 25 to 70% of W and 5 to 45% of Co in terms of% by mass and further contains 0.6 to 3.5% of C, 0.05 to 3% of Si, 0.05 to 3% of Mn, 15%, and the balance of inevitable impurities. It is also preferable that the above composition is satisfied at a radial position corresponding to a volume of at least 20% of the outer surface side with respect to the total volume of the outer layer material. For example, it is preferable that a sleeve having an outer diameter of 250 mm and an inner diameter of 140 mm is satisfied at a position of at least 9 mm in the radial direction from the position corresponding to the maximum diameter at the time of rolling to the inner peripheral side.

The term " outer layer material surface at a position corresponding to the maximum diameter at the time of rolling use " as used herein means a layer formed on the outer surface of the outer layer material while being cast (a region where the melt is quenched by contact with the mold and solidified) Refers to the surface of the outer layer material at a position corresponding to the maximum diameter of the roll diameter of the product provided for rolling use, that is, the surface of the outer layer material at a position corresponding to the maximum diameter that can be used as a product (roll outer layer material) It says. Specifically, "the surface of the outer layer material at the position corresponding to the maximum diameter at the time of rolling" means that the layer formed on the outer surface of the outer layer material while being cast is grinded and removed to obtain the maximum diameter of the product roll diameter Is a position corresponding to a range of 20% volume of at least the outer surface side relative to the total volume of the outer layer material in the radial direction from the surface of the outer layer material at the corresponding position to the inner radius side.

The compositional analysis of the surface of the outer layer material may be performed by instrumental analysis such as fluorescence X-ray analysis or emission spectral analysis, or may be a destructive inspection. However, from the position including the surface of the outer layer material, Is less than 10 mm, and the sample is subjected to chemical analysis.

First, the reasons for limiting the composition of the rolled outer layer material of the present invention will be described. Hereinafter, the mass% with respect to the composition is simply expressed in%.

C: 0.6 to 3.5%

C is an element that combines with W and a carbide forming element such as Mo, Cr, V, or Nb to form a light carbide and has an action to improve abrasion resistance. Depending on the amount of C, the shape, crystallization amount and crystallization temperature of the carbide change. When the content of C is 0.6% or more, the M ₆ C type carbide is crystallized as a super crystal phase, and a structure shape segregated on the outer surface side during centrifugal casting is obtained, and wear resistance is improved. When the content of C is less than 0.6%, the amount of M ₆ C-type carbide crystallized as a primary crystal is insufficient and wear resistance is lowered. On the other hand, when C is contained in a large amount exceeding 3.5%, production of the outer layer material becomes difficult, and M ₂ C carbide or MC carbide, which is liable to be split, is generated and coarsened, It becomes easier to do. In this respect, C is limited to a range of 0.6 to 3.5%. Further, C is preferably 1.0 to 3.0%. More preferably, C is 1.2 to 2.8%.

Si: 0.05 to 3%

Si is an element that acts as a deoxidizing agent and also has a known strengthening action. In order to obtain such an effect, the Si content is required to be 0.05% or more. On the other hand, even if the content of Si exceeds 3%, the effect saturates, and graphite flakes appear and the toughness lowers. For this reason, Si is limited to a range of 0.05 to 3%. In addition, Si is preferably 0.1 to 2%. More preferably, Si is 0.2 to 1.8%.

Mn: 0.05 to 3%

Mn is an element having an action of fixing S as MnS and detoxifying S which adversely affects the material. In addition, Mn is employed at the base and contributes to improvement of hardenability. In order to obtain such an effect, it is necessary to contain Mn of 0.05% or more. On the other hand, even when Mn is contained in an amount exceeding 3%, the above-mentioned effect is saturated, which causes material deterioration. For this reason, Mn is limited to the range of 0.05 to 3%. Further, Mn is preferably 0.1 to 1%. More preferably, Mn is 0.2 to 0.8%.

Mo: 1 to 15%

Mo is a carbide-forming element that forms a carbide by binding with C. In the present invention, in particular, the Mo is strengthened in the hard M ₆ C type carbide, which is a superabsorbent hardened by W, to increase the fracture resistance of the roll outer layer material . Further, Mo improves the quenching property at the time of heat treatment and contributes to increase the hardness of the roll outer layer material. Further, Mo is an element heavier than Co, and has the effect of preventing or promoting centrifugal separation of the super-pure carbide on the outer surface side. In order to obtain these effects, Mo content of 1% or more is required. On the other hand, when Mo is contained in an amount exceeding 15% in a large amount, hard and brittle carbides of the Mo main body appear and wear resistance is lowered. For this reason, Mo is limited to a range of 1 to 15%. Further, Mo is preferably 2 to 10%. More preferably, Mo is 4 to 10%.

W: 25 to 70%

W is the most important element in the present invention, and has an alloy composition containing a large amount of 25% or more. As a result, a hard M ₆ C type carbide, in which W is concentrated, can be made to appear in a large amount as a primary crystal, and a rolled outer layer material having remarkably improved abrasion resistance can be obtained. In addition, when the content of W is less than 25%, it becomes difficult to obtain a roll outer layer material having excellent abrasion resistance for the purpose of the present invention. On the other hand, in the case of W content exceeding 70%, the M ₆ C type carbide is coarsened and becomes brittle, and the melting point of the molten metal rises, making melting, casting, etc. difficult. For this reason, W is limited to a range of 25 to 70%. Further, W is preferably 30 to 65%. More preferably, W is 35 to 55%.

Co: 5 to 45%

Co, together with W, is an important element in the present invention. By containing a large amount of Co together with W, the activity of C is increased, and the occurrence of a large amount of hard carbide (M ₆ C type, M ₂ C type, MC type or the like) in which W is concentrated is promoted , Which contributes to improvement of wear resistance of the rolling roll outer layer material. In order to obtain such an effect, it is necessary to contain Co at 5% or more. On the other hand, when Co is contained in an amount exceeding 45% in a large amount, the γ phase is stabilized and the base becomes soft. When Co is used as a rolling roll, a large number of cracks (indentations) . For this reason, Co is limited to a range of 5 to 45%. Further, Co is preferably 10 to 40%. More preferably, Co is 15 to 35%.

The above-mentioned component is a basic component. However, in addition to the basic composition, one or two or more selected from the group consisting of 5 to 40% of Fe, 0.1 to 10% of Cr, 0.1 to 6% of V and 0.1 to 3% of Nb, And / or Ni: 0.05 to 3%, if necessary.

At least one selected from the group consisting of Fe: 5 to 40%, Cr: 0.1 to 10%, V: 0.1 to 6%, Nb: 0.1 to 3%

Fe, Cr, V, and Nb are carbide-forming elements, which are elements that have an effect of solidifying carbides by solidifying into carbides, and may contain one or two or more kinds of them if necessary.

Fe solidifies on the carbide and solidifies on the base, contributing to strengthening of the matrix, and has the function of preventing generation of dent scratches (recesses) when used as a rolling roll. In order to obtain such an effect, it is preferable that Fe is contained at 5% or more. On the other hand, when Fe is contained in an amount exceeding 40%, the amount of hard M ₆ C-type carbide that appears as a superfine phase decreases, and the fragile M ₃ C-type carbide increases and wear resistance decreases. Therefore, in the case of containing Fe, the content of Fe is preferably limited to a range of 5 to 40%. More preferably, Fe is 10 to 35%. More preferably, Fe is 12 to 30%.

Although the mechanism for strengthening the base of the W-Co based alloy by containing Fe in the matrix is not clarified at this time, the phase stabilizing action by Fe is offset by the phase stabilizing action by Fe, The strength is increased, or the α-phase stabilizing action of Fe is large, so that the base becomes hard martensite or bainite structure, or a structure in which further fine carbide precipitates further appears in such a base, etc. It is thought that the reinforcement phenomenon of the base occurred.

Cr is a strong carbide-forming element, and has an effect of mainly forming a process carbide and improving the strength of the formed carbide. Since the process carbide is purged to the gap of the M ₆ C type carbide as a result, it acts to strengthen the gap of the M ₆ C type carbide. Cr also has an action of suppressing the appearance of graphite. Since the W-Co based alloy has a high activity coefficient of C, graphite tends to appear, and toughness deteriorates when graphite appears. In order to suppress the appearance of graphite and use it stably as a roll for rolling, it is preferable that Cr is contained in the present invention as required. In order to obtain such an effect, Cr is preferably contained in an amount of 0.1% or more. On the other hand, if Cr is contained in an amount exceeding 10%, a large amount of Cr-based process carbides emerge and the toughness decreases. For this reason, when contained, Cr is preferably limited to a range of 0.1 to 10%. More preferably, Cr is 1 to 8%. More preferably, Cr is 1.5 to 7%.

V is an element which forms a rigid VC (MC type carbide including Mo, Nb, Cr, W and the like) in combination with C, in which the formed MC type carbide is crystallized as a primary crystal, and M ₆ C type carbide is a nucleus of the crystallization, to promote the emergence of the M ₆ C type carbide has a function of dispersing the finer M ₆ C type carbide at a high density. In order to obtain such an effect, it is preferable that V is contained at 0.1% or more. On the other hand, when V is contained in a large amount exceeding 6%, V-type MC-type carbides having a low specific gravity are increased and coarsened even if W is contained in a large amount, and centrifugal casting is performed on the inner surface side of the roll outer- do. Therefore, the amount of hard M ₆ C type carbide on the outer surface side is insufficient, and the abrasion resistance upon use of the roll outer layer material is lowered. Further, when a large amount of V-series MC type carbide is centrifugally separated on the inner surface side, the boundary strength with the in-roll layer and the intermediate layer decreases. Therefore, when contained, V is preferably limited to a range of 0.1 to 6%. More preferably, V is 1 to 5%. More preferably, V is 1.5 to 4%.

Nb has a very strong bonding force with C, and as a strong carbide forming element, it is easy to form a complex carbide with V or W. Such a composite carbide of Nb and V and W are, is the crystallization nuclei of M ₆ C type carbide han W is a thickening, which crystallized as the Primary, it promotes the appearance of M ₆ C type carbide, finer M ₆ C type carbide At high density. In order to obtain such an effect, Nb content is required to be 0.1% or more. On the other hand, in the case of a large amount of Nb exceeding 3%, the Nb-based MC type carbide of low density is formed and coarsened, and the carbide is easily centrifuged on the inner surface side of the roll outer layer material during centrifugal casting, The amount of MC type carbide on the inner side increases. Further, when the amount of the MC-type carbide centrifuged on the inner surface side of the outer layer material is increased, the strength of the boundary between the inner layer and the intermediate layer is lowered. Therefore, when contained, Nb is preferably limited to a range of 0.1 to 3%. More preferably, Nb is 0.5 to 2%. More preferably, Nb is 0.6 to 1.8%.

Ni: 0.05 to 3%

Ni is an element having an action to improve the quenching property, and may be contained as needed, for example, in order to overcome the lack of quenching in a large roll. In order to obtain such an effect, it is preferable that Ni is contained by 0.05% or more. If the impurity level is less than 0.05%, the effect is not recognized. On the other hand, if the content of Ni exceeds 3%, the? -Phase is stabilized and the desired quenching can not be ensured. Therefore, when contained, it is preferable to limit the Ni to the range of 0.05 to 3%. More preferably, Ni is 0.1 to 2.5%.

The remainder other than the above-mentioned components are made of inevitable impurities. As the inevitable impurities, P, S, N, and B can be exemplified. P is segregated at grain boundaries and adversely affects such as embrittlement of the material. Therefore, it is preferable to reduce P as much as possible as impurities, but it is acceptable if P is 0.05% or less. S is segregated in the grain boundaries as well as in the grain boundaries and has an influence such as embrittlement. Therefore, it is preferable to reduce the impurity as much as possible, but if it is 0.05% or less, a part of the impurities is combined with Mn to form sulfide inclusions It is harmless and can be tolerated. Further, N is mixed in an amount of 0.01 to 0.1% as an impurity in the case of ordinary dissolution. However, the content of this amount does not affect the effect of the present invention. However, since N may generate gas defects at the boundary between the outer layer of the composite roll and the intermediate layer or the inner layer, N is preferably limited to less than 0.07%. In addition, B may be mixed from scraps or a casting flux of the molten raw material and may be contained as an inevitable impurity element. B may be employed in carbide or base to change the properties of the carbide, or it may be employed in the base to affect the quality of the base and to improve the quality deviation. Therefore, B is preferably reduced as much as possible, but if it is 0.1% or less, the effect of the present invention is not adversely affected. Here, it is preferable that the inevitable impurity element is adjusted to less than 1% in total.

Next, a preferable manufacturing method of the rolled outer layer material of the present invention will be described.

In the present invention, from the viewpoints of productivity and production cost, the roll outer layer material is manufactured by using a centrifugal casting method of rotating the casting mold. As a result, it is possible to produce an outer roll material for rolling which is inexpensive and excellent in abrasion resistance.

First, the above-mentioned molten metal of the roll outer layer composition is poured into a rotating mold so as to have a predetermined thickness, and centrifugal casting is performed to obtain a rolling roll outer material. Generally, in order to protect the mold, it is general that the inner surface is coated with a refractory material based on zircon or the like. In the present invention, it is preferable to perform centrifugal casting by adjusting the number of revolutions so that the centrifugal force becomes 120 to 250G. By imparting a high centrifugal force, the dispersion density of the hard carbide having a high density on the outer surface side can be increased.

In the present invention, the rolled roll outer layer material obtained may be a single sleeve, and may be rolled by fitting a shaft member thereto. For example, as shown in Fig. 3, the rolled outer layer material may be heat-shrunk fitted to a shaft of a carbon steel forged carbon steel to form a composite roll. The rolling roll outer layer material obtained may be a rolling roll formed by forming an intermediate layer welded and integrated inside thereof and a sleeve having an intermediate layer and fitting a shaft material therebetween. It is preferable that the intermediate layer is formed by centrifugal casting during the solidification of the roll outer layer material or after solidifying completely and then pouring the melt of the intermediate layer composition while rotating the casting mold. Graphite steel, 1 to 2% by mass of high carbon steel, hypoeutectic cast iron and the like can be given as an intermediate layer material. The shafts of the rolling rolls are not particularly limited, but they are preferably made of separately manufactured forged steel products (shafts), cast steel products (shafts) and cast iron products (shafts).

Further, in the present invention, a composite roll (for example, a schematic cross-sectional view of a composite roll shown in Fig. 4) made of an outer layer of rolling roll outer layer material and an inner layer welded and integrated with the outer layer may be used, (For example, a schematic view of the cross section of the composite roll shown in Fig. 5) composed of a rolling roll outer layer material as an outer layer, an intermediate layer welded and integrated with the outer layer, and an inner layer welded and integrated with the intermediate layer .

In the case of forming the intermediate layer, it is preferable to perform the centrifugal casting by pouring the molten metal of the intermediate layer composition while the mold is solidified or completely solidified after rotating the outer layer material. It is preferable to use graphite steel, high carbon steel of 1 to 2 mass% C, sub-step cast iron and the like as the intermediate layer material. The intermediate layer and the outer layer are integrally welded, and the outer layer component is mixed in the range of about 10 to 90% as an intermediate layer. From the viewpoint of suppressing the mixing amount of the outer layer component into the inner layer, it is preferable to reduce the mixing amount of the outer layer component into the intermediate layer as much as possible.

Generally, the inner layer is formed by static casting after the outer layer or the intermediate layer is completely solidified, the rotation of the mold is stopped to form the mold, and the inner layer material is then cast. Here, nodular graphite cast iron and vermicular graphite cast iron (CV cast iron), which are excellent in castability and mechanical properties, are preferably used as the inner layer material to be subjected to political casting. Further, in a composite roll in which the intermediate layer is not present and the outer layer and the inner layer are integrally welded, the components of the outer layer material are often mixed into the inner layer by about 1 to 10%. W, Cr, V and the like contained in the outer layer material are strong carbide forming elements. When these elements are incorporated into the inner layer, the inner layer is weakened. Therefore, in the present invention, it is preferable to suppress the mixing ratio of the outer layer component into the inner layer to less than 5%.

It is preferable that the rolling roll outer layer material and the rolling composite roll are subjected to heat treatment after casting. The heat treatment may be carried out by heating at 1000 to 1200 占 폚 and holding for 5 to 40 hours, cooling in a furnace, air cooling or air blast cooling, and further heating and holding at 400 to 600 占 폚 It is preferable to perform the cooling process at least once. It is preferable that the hardness of the rolled outer material and rolling composite roll according to the present invention is adjusted within the range of 79 SIMILAR 100 HS, depending on the application. In order to secure such hardness stably, it is recommended to adjust the post-casting heat treatment.

[Second embodiment]

The rolled roll outer layer material of the present invention is a centrifugal casting agent. The " rolled outer layer material for rolling casting master batch " as used herein means a rolled outer layer material in a state of being manufactured using a centrifugal casting method which has been conventionally used as a method for producing rolling rolls. The roll outer material (rolled outer layer material for "centrifugal casting") produced by the centrifugal casting method has been conventionally distinguished from the roll for rolling produced by other manufacturing methods as "water" In addition, specifying the roll outer layer material for rolling the "centrifugal casting agent" by structure and characteristics requires a lot of effort and is impractical.

The roll outer layer material of the present invention is made of a W-Co based alloy and has an inclined composition in which the W content decreases in the radial direction from the outer peripheral side to the inner peripheral side of the roll and becomes a surface layer at a position corresponding to the maximum diameter at the time of rolling Wherein the outer layer material contains 25 to 70% of W, 5 to 45% of Co, and further contains 0.6 to 3.5% of C, 0.05 to 3% of Si, 0.05 to 3% of Mn, To 15%, and the content of W, Co, Mo, and Fe satisfies the following formula [1], and the remainder is inevitable impurities. It is also preferable that the above composition is satisfied at a radial position corresponding to a volume of at least 20% of the outer surface side with respect to the total volume of the outer layer material. For example, it is preferable that a sleeve having an outer diameter of 250 mm and an inner diameter of 140 mm is satisfied at a position of at least 9 mm in the radial direction from the position corresponding to the maximum diameter at the time of rolling to the inner peripheral side.

(% W +% Mo) / (% Co +% Fe)? 9.0 [1]

Here,% W,% Mo,% Co, and% Fe are content (mass%) of each element, and are set to 0 when they are not contained.

Here, the " outer layer material serving as a surface layer at a position corresponding to the maximum diameter at the time of rolling use " as used herein means a layer formed on the outer surface of the outer layer material while being cast (a region where the molten metal is quenched by contact with the mold and solidified ) Of the outer diameter of the roll, and is the surface layer of the surface layer corresponding to the maximum diameter of the product roll diameter provided for the rolling use. That is, the term "outer layer material" refers to an outer layer material having a thickness of at least 9 mm in the radial direction serving as a surface layer at a position corresponding to the maximum diameter that can be used as a product (roll outer layer material).

The composition of the outer layer material to be the surface layer may be analyzed by instrumental analysis such as fluorescent X-ray analysis or emission spectral analysis or may be a destructive inspection. However, from the position including the outer layer material serving as the surface layer, Shaped sample having a thickness of less than 10 mm may be sampled, and the sample may be subjected to chemical analysis.

First, the reasons for limiting the composition of the rolled outer layer material of the present invention will be described. Hereinafter, the mass% with respect to the composition is simply expressed in%.

C: 0.6 to 3.5%

C is an element that combines with W and a carbide forming element such as Mo, Cr, V, or Nb to form a light carbide and has an action to improve abrasion resistance. Depending on the amount of C, the shape, crystallization amount and crystallization temperature of the carbide change. When C is 0.6% or more, the M ₆ C type carbide is crystallized as a super crystal phase, and a structure shape segregated on the outer surface side during centrifugal casting is obtained, and wear resistance is improved. When C is less than 0.6%, the amount of M ₆ C type carbide to be crystallized as a preliminary crystal is insufficient and wear resistance is lowered. On the other hand, when C is contained in a large amount exceeding 3.5%, it becomes difficult to produce the outer layer material and M ₂ C carbide or MC carbide, which is liable to be very easily split, is generated and coarsened, It becomes easier to do. In this respect, C is limited to a range of 0.6 to 3.5%. Further, C is preferably 1.0 to 3.0%. More preferably, C is 1.2 to 2.8%.

Si: 0.05 to 3%

Si is an element that acts as a deoxidizing agent and also has a known strengthening action. In order to obtain such an effect, the content of Si needs to be 0.05% or more. On the other hand, even if Si is contained in an amount exceeding 3%, the effect is saturated, but the graphite appears and the toughness lowers. For this reason, Si is limited to a range of 0.05 to 3%. Further, Si is preferably 0.05 to 2%. More preferably, Si is 0.2 to 1.8%.

Mn: 0.05 to 3%

Mn is an element having an action of fixing S as MnS and detoxifying S which adversely affects the material. In addition, Mn is employed at the base, contributing to the improvement of quenching. In order to obtain such an effect, Mn should be contained in an amount of 0.05% or more. On the other hand, even when Mn is contained in an amount exceeding 3%, the above-mentioned effect is saturated, which causes material deterioration. For this reason, Mn is limited to the range of 0.05 to 3%. Further, Mn is preferably 0.1 to 1%. More preferably, Mn is 0.2 to 0.8%.

Mo: 1 to 15%

Mo is a carbide-forming element that forms a carbide by binding with C. In the present invention, in particular, the Mo is strengthened in the hard M ₆ C type carbide, which is a superabsorbent hardened by W, to increase the fracture resistance of the roll outer layer material . Further, Mo improves the quenching at the time of heat treatment and contributes to increase the hardness of the roll outer layer material. Further, Mo is an element heavier than Co, and has the effect of preventing or promoting centrifugal separation of the super-pure carbide on the outer surface side. In order to obtain these effects, Mo must be contained in an amount of 1% or more. On the other hand, when Mo is contained in an amount exceeding 15% in a large amount, hard carbide of the Mo main body appears and wear resistance is lowered. For this reason, Mo is limited to a range of 1 to 15%. Further, Mo is preferably 2 to 10%. More preferably, Mo is 4 to 10%.

W: 25 to 70%

W is the most important element in the present invention, and has an alloy composition containing a large amount of 25% or more. As a result, a hard M ₆ C type carbide, in which W is concentrated, can be made to appear in a large amount as a primary crystal, and a rolled outer layer material having remarkably improved abrasion resistance can be obtained. On the other hand, when the content of W exceeds 70%, the M ₆ C type carbide tends to be coarse and fragile, and the melting point of the molten metal rises, making melting and casting difficult. For this reason, W is limited to a range of 25 to 70%. Further, W is preferably 30 to 65%. More preferably, W is 35 to 55%.

Co: 5 to 45%

Co, together with W, is an important element in the present invention. By containing a large amount of Co together with W, the activity of C is increased, and the occurrence of a large amount of hard carbide (M ₆ C type, M ₂ C type, MC type or the like) in which W is concentrated is promoted , Which contributes to improvement of wear resistance of the rolling roll outer layer material. In order to obtain such an effect, it is necessary to contain Co at 5% or more. On the other hand, when Co is contained in an amount exceeding 45% in a large amount, the γ phase is stabilized and the matrix becomes soft, and when used as a rolling roll, a bundle of dent scratches (recesses) do. For this reason, Co is limited to a range of 5 to 45%. Further, Co is preferably 10 to 40%. More preferably, Co is from 12 to 35%.

The above-mentioned component is a basic component. However, in addition to the basic composition, one or two or more selected from the group consisting of 5 to 40% of Fe, 0.1 to 10% of Cr, 0.1 to 6% of V and 0.1 to 3% of Nb, And / or Ni: 0.05 to 3%, if necessary.

At least one selected from the group consisting of Fe: 5 to 40%, Cr: 0.1 to 10%, V: 0.1 to 6%, Nb: 0.1 to 3%

Fe, Cr, V, and Nb are all carbide-forming elements, and are elements which have an action to solidify carbides by solidification in carbides, and may contain one or more kinds as needed.

Fe solidifies on the carbide and solidifies on the base, contributing to strengthening of the matrix, and has the function of preventing generation of dent scratches (recesses) when used as a rolling roll. In order to obtain such an effect, Fe is preferably contained in an amount of 5% or more. On the other hand, when Fe is contained in an amount exceeding 40%, the amount of hard M ₆ C-type carbide that appears as a superfine phase decreases, and the fragile M ₃ C-type carbide increases and wear resistance decreases. Therefore, in the case of containing Fe, the content of Fe is preferably limited to a range of 5 to 40%. More preferably, Fe is 10 to 35%. More preferably, Fe is 12 to 30%.

Although the mechanism by which the base of the W-Co based alloy is strengthened by containing Fe in the matrix is not clarified at present, the phase stabilizing action by Fe is offset by the phase stabilizing action by Fe, and as a result, It is because the strength is increased or the α phase stabilizing action of Fe is large and the martensite or bainite structure having a hard base is formed or a structure in which a fine carbide is further precipitated further in such a base appears Is thought to have occurred.

Cr is a strong carbide-forming element, and has an effect of mainly forming a process carbide and improving the strength of the formed carbide. Since the process carbide is purged to the gap of the M ₆ C type carbide as a result, it acts to strengthen the gap of the M ₆ C type carbide. Cr also has an action of suppressing the appearance of graphite. Since the W-Co based alloy has a high activity coefficient of C, graphite tends to appear, and toughness deteriorates when graphite appears. In order to suppress the appearance of graphite and use it stably as a roll for rolling, it is preferable that Cr is contained in the present invention as required. In order to obtain such an effect, Cr is preferably contained in an amount of 0.1% or more. On the other hand, if Cr is contained in an amount exceeding 10%, a large amount of Cr-based process carbides emerge and the toughness decreases. For this reason, when contained, Cr is preferably limited to a range of 0.1 to 10%. More preferably, Cr is 1 to 8%. More preferably, Cr is 1.5 to 7%.

V is an element which forms a rigid VC (MC type carbide including Mo, Nb, Cr, W and the like) in combination with C, in which the formed MC type carbide is crystallized as a primary crystal, and M ₆ C type carbide and the extrusion of the core, facilitating the occurrence of the M ₆ C type carbide has a function of dispersing the finer M ₆ C type carbide at a high density. In order to obtain such an effect, V is preferably contained in an amount of 0.1% or more. On the other hand, when V is contained in a large amount exceeding 6%, V-type MC-type carbides having a low specific gravity are increased and coarsened and centrifuged on the inner surface side of the roll outer layer material during centrifugal casting . Therefore, the amount of hard M ₆ C type carbide on the outer surface side is insufficient, and the abrasion resistance upon use of the roll outer layer material is lowered. Further, when a large amount of V-series MC type carbide is centrifugally separated on the inner surface side, the boundary strength with the in-roll layer and the intermediate layer decreases. Therefore, when contained, V is preferably limited to a range of 0.1 to 6%. More preferably, V is 1 to 5%. More preferably, V is 1.5 to 4%.

Nb has a very strong bonding force with C, and as a strong carbide forming element, it is easy to form a complex carbide with V or W. This is the crystallization nucleation of W One M ₆ C type carbide thickening, which crystallized as the Nb and V and W the complex carbide is invited of, promotes the appearance of the M ₆ C type carbide, finer M ₆ C type carbide At high density. In order to obtain such an effect, Nb content is required to be 0.1% or more. On the other hand, when Nb is contained in a large amount exceeding 3%, Nb-based MC type carbide having a low specific gravity is formed and coarsened, so that carbide is easily centrifuged on the inner surface side of the roll outer layer material during centrifugal casting, The amount of MC type carbide on the inner surface side increases. Further, when the amount of the MC-type carbide centrifuged on the inner surface side of the outer layer material is increased, the strength of the boundary between the inner layer and the intermediate layer is lowered. Therefore, when contained, Nb is preferably limited to a range of 0.1 to 3%. More preferably, Nb is 0.5 to 2%. More preferably, Nb is 0.6 to 1.8%.

Ni: 0.05 to 3%

Ni is an element having an action to improve the quenching property and may be contained as needed, for example, in order to solve the problem of insufficient quenching in a large roll. In order to obtain such an effect, Ni is preferably contained in an amount of 0.05% or more. Further, the effect of Ni is not recognized when the impurity level is less than 0.05%. On the other hand, when the content of Ni exceeds 3%, the? Phase is stabilized and the desired quasimeter can not be secured. Therefore, when contained, it is preferable to limit the Ni to the range of 0.05 to 3%. More preferably, Ni is 0.1 to 2.5%.

The remainder other than the above-mentioned components are made of inevitable impurities. As the inevitable impurities, P, S, N, and B can be exemplified. P is segregated at grain boundaries and adversely affects such as embrittlement of the material. Therefore, it is preferable to reduce P as much as possible as impurities. However, if P is 0.05% or less, it is acceptable. S is segregated at the grain boundaries as well as S, and influences such as embrittlement of the material. Therefore, it is preferable that S is as low as possible as impurities. When S is 0.05% or less, It is allowed to exist because it exists as a system inclusion and becomes harmless. Further, N is mixed in an amount of 0.01 to 0.1% as an impurity in the case of ordinary dissolution. However, the content of this amount does not affect the effect of the present invention. Note that N may generate gas defects at the boundary between the outer layer of the composite roll and the intermediate layer or the inner layer, so N is preferably limited to less than 0.07%. In addition, B may be mixed as an inevitable impurity element by mixing from the scrap of the raw material for dissolution and the flux for casting. B may be employed in carbide or base to change the properties of the carbide, or it may be employed in the base to affect the quality of the base and to improve the quality deviation. Therefore, B is preferably reduced as much as possible, but if B is less than 0.1%, the effect of the present invention is not adversely affected. Here, it is preferable that the inevitable impurity element is adjusted to less than 1% in total.

The outer layer material to be the surface layer at the position corresponding to the maximum diameter at the time of rolling in the present invention contains the above composition and the content of W, Co, Mo and Fe satisfies the following formula (1).

(% W +% Mo) / (% Co +% Fe)? 9.0 [1]

Here,% W,% Mo,% Co, and% Fe are content (mass%) of each element, and are set to 0 when they are not contained.

(% W +% Mo) / (% Co +% Fe) is not less than 1.2, a large amount of light carbides are accumulated and the amount of W and Mo incorporated in the matrix increases, The Young's modulus is more than 270.. Conventional high-speed tool steel rolls have a Young's modulus of the surface layer contacting the pressurized steel sheet of about 220 to 235 ° C (see, for example, Non-Patent Documents 4 and 5) An effect of reducing the rolling load by suppressing deformation is obtained. (% W +% Mo) / (% Co +% Fe) is less than 1.2, satisfactory abrasion resistance can be obtained when the composition is satisfied. However, since the Young's modulus is less than 270,, It does not. On the other hand, it is economically disadvantageous to add a large amount of expensive W and Mo in order to make (% W +% Mo) / (% Co +% Fe) (% Co +% Fe) had an upper limit of 9.0. As a result of examining the examples of the present inventors, it has been found that the sum of the high-dose amounts of W and Mo in the matrix becomes 3.5% or more when (% W +% Mo) / (% Co +% Fe) It is confirmed that a Young's modulus of ㎬ or more is obtained. (% W +% Mo) / (% Co +% Fe) may be controlled by the molten metal composition, the casting temperature during centrifugal casting, and the centrifugal force. Preferably, (% W +% Mo) / (% Co +% Fe) is not less than 4.8 and not more than 7.8.

In order to exhibit an excellent rolling load reducing effect, the roll outer layer material of the present invention preferably has a Young's modulus of 270 to 500 kPa as the outer layer material to be a surface layer at a position corresponding to the maximum diameter at the time of rolling. As described above, the roll of the conventional high-speed tool steel system has a Young's modulus of the surface layer in contact with the pressurized steel sheet of about 220 to 235 ° C. (see, for example, Non-Patent Documents 4 and 5) , An effect of reducing the rolling load by suppressing the elastic deformation of the surface layer of the roll can be obtained. However, in order to make the Young's modulus larger than 500 GPa, it is necessary to contain a large amount of an alloy element, which is economically disadvantageous. Therefore, the Young's modulus is preferably 270 GPa or more and 500 GPa or less.

The Young's modulus can be measured by taking a compression test piece or a tensile test piece from the outer layer material at a position corresponding to the maximum diameter at the time of rolling and calculating the gradient from the elastic deformation in the compression test or the tensile test, .

Next, a preferable manufacturing method of the rolled outer layer material of the present invention will be described.

In the present invention, from the viewpoints of productivity and production cost, the roll outer layer material is manufactured by using a centrifugal casting method of rotating the casting mold. As a result, it is possible to produce an outer roll material for rolling which is inexpensive and excellent in abrasion resistance.

First, the above-mentioned molten metal of the roll outer layer composition is poured into a rotating mold so as to have a predetermined thickness, and centrifugal casting is performed to obtain a rolling roll outer material. Generally, in order to protect the mold, it is general that the inner surface is coated with a refractory material based on zircon or the like. In the present invention, it is preferable to perform centrifugal casting by adjusting the number of revolutions so that the centrifugal force at a position corresponding to the maximum diameter at the time of rolling is 120 to 250G. By imparting a high centrifugal force, the dispersion density of the light carbide having a large specific gravity on the outer surface side can be increased.

In the present invention, the rolled roll outer layer material obtained may be rolled as a single sleeve by fitting a shaft material therebetween (for example, see Fig. 8). Further, the rolled roll outer layer material obtained may be a rolled roll, in which an intermediate layer welded and integrated in the inside thereof is formed and a sleeve having an intermediate layer is fitted therebetween. The intermediate layer is preferably formed by coagulating or completely solidifying the rolled outer layer material, and then pouring the molten intermediate layer composition while rotating the casting mold, followed by centrifugal casting. Examples of the intermediate layer material include graphite steel, high carbon steel of 1 to 2% by mass, sub-step cast iron, and the like. The shafts of the rolling rolls are not particularly limited, but they are preferably made of separately manufactured forged steel products (shafts), cast steel products (shafts) and cast iron products (shafts).

Further, in the present invention, it is also possible to use a composite roll composed of the rolling roll outer layer material as an outer layer and an inner layer welded and integrated with the outer roll layer as described above, or an outer layer of the rolling roll outer layer material as the outer layer, , And an inner layer welded and integrated with the intermediate layer.

In the case of forming the intermediate layer, it is preferable to perform the centrifugal casting by pouring the molten metal of the intermediate layer composition while the mold is solidified or completely solidified after rotating the outer layer material. It is preferable to use graphite steel, high carbon steel of 1 to 2 mass% C, sub-step cast iron and the like as the intermediate layer material. The intermediate layer and the outer layer are integrally welded, and the outer layer component is incorporated into the intermediate layer in a range of about 10 to 90%. From the viewpoint of suppressing the mixing amount of the outer layer component into the inner layer, it is preferable to reduce the mixing amount of the outer layer component into the intermediate layer as much as possible.

Generally, the inner layer is formed by completely solidifying the outer layer or the intermediate layer, stopping the rotation of the mold to stand the mold, and then casting the inner layer material. Here, it is preferable to use spherical graphite cast iron and larch type graphite cast iron (CV cast iron) excellent in castability and mechanical properties as the inner layer material to be subjected to the political casting. Further, in a composite roll in which the intermediate layer is not present and the outer layer and the inner layer are integrally welded, the components of the outer layer material are often mixed into the inner layer by about 1 to 10%. W, Cr, and V contained in the outer layer material are strong carbide forming elements. When these elements are incorporated into the inner layer, the inner layer becomes weak. Therefore, in the present invention, it is preferable to suppress the mixing ratio of the outer layer component into the inner layer to less than 5%.

It is preferable that the above rolling roll outer layer material and rolling composite roll be subjected to heat treatment after casting. The heat treatment is carried out at a temperature of 1000 to 1200 캜 and maintained for 5 to 40 hours, followed by cooling in a furnace, air cooling or forced air cooling, and further cooling and holding at 400 to 600 캜 for one or more times . It is preferable that the hardness of the rolling roll material for rolling and rolling composite rolls of the present invention is adjusted within the range of 79 SIMILAR 100 HS, depending on the application. In order to secure such hardness stably, it is recommended to adjust the post-casting heat treatment.

Example

[Example 1]

First, an embodiment of the first embodiment described above will be described.

The molten metal having the composition shown in Table 1 was dissolved in a high frequency induction furnace, and a roll-shaped outer layer material (outer diameter: 250 mm phi, radial thickness: 55 mm) was cast as a test material by a centrifugal casting method. The casting temperature was 1450 to 1550 占 폚, and the centrifugal force was 140 to 220G as gravity multiple. In some of test materials (molten metal No.S), since significant carbide segregation occurred on the inner surface, 60 G was set for the purpose of reducing segregation. After the casting, the casting was reheated to 1050 to 1200 占 폚, held for 10 hours, and then cooled to 100 占 폚 or lower and tempered at 400 to 560 占 폚 to be cooled and heated once or twice . Thus, the hardness at a position of 5 mm in the thickness direction from the outer surface of the test material was adjusted to approximately 85 to 100 HZ. In addition, a commercially available centrifugal casting outer layer composition (high speed tool steel roll composition: 2.2% C-0.4% Si-0.4% Mn-5.3% Cr-5.2% Mo- 5.6% V -1.1% Nb) was melted and a rolled outer layer material in the form of a sleeve was cast in the same manner and subjected to heat treatment after casting to obtain a test sample (hardness 85 HS) No.22).

From the test material subjected to the heat treatment, a test piece for composition analysis and a test piece for abrasion test were collected. In addition, the test material No. 19 was very easy to crack, and it was very difficult to collect the test material.

The test specimen for composition analysis was prepared by grinding 5 mm in the radial direction from the outer surface of the test material after the heat treatment as described above and measuring 5 mm in the radial direction from the outer surface after grinding and 10 mm 10 mm in the plane parallel to the outer surface Size specimens were taken. The obtained test pieces were used to analyze each component element. Mn, Cr, and Mo were measured by atomic absorption spectrometry, Co was measured by the capacity method, and Fe was measured by the dosing method or the atomic absorption method.

The obtained results are shown in Table 2.

The abrasion test piece (60 mm in outer diameter x 10 mm in width) was sampled from the test piece after the heat treatment so that the center position of the width of the abrasion test piece was 10 mm in the radial direction from the outer surface of the test piece. As shown in Fig. 2, the abrasion test was carried out by a two-disc sliding transfer method of a test piece (abrasion test piece) and a counter material (material: S45C, outer diameter 190 mm? X width 15 mm).

In the abrasion test, a test piece rotated at 700 rpm (peripheral speed: 2.1 m / s) while rotating the test piece with water was pressed against a counterpart heated at 850 캜 with a load of 980 N, 14.2%. The electric power of the test piece was updated every 21,000 times, and the electric motor was rotated until the cumulative number of revolutions reached 168,000 times. After the end of the test, the wear loss of the wear test piece was examined. The ratio of abrasion loss of each test material to the standard (abrasion loss ratio = (abrasion loss amount in the conventional example) / ((abrasion loss amount in the conventional example)) was calculated with respect to the obtained abrasion loss, Wear loss amount of the test material)) was calculated, and the abrasion resistance was evaluated. , The case where the abrasion resistance ratio is 3 or more is represented by the symbol " ", the case where the abrasion resistance ratio is 2 or more and less than 3 is represented by the symbol & Good " and " symbol X "

The obtained results are shown in Table 3.

In the first embodiment, the abrasion resistance is remarkably improved in comparison with the conventional example (high speed tool steel roll) because the abrasion resistance ratio is 2.1 or more in all of the examples of the present invention. On the other hand, in the comparative example deviating from the scope of the present invention, cracks were generated during the test, or the abrasion resistance ratio was less than 2, so that the wear resistance was less improved as compared with the conventional example.

Further, the structure was observed with respect to Inventive Examples (No. 13 and No. 5) and is shown in FIG. A specimen for tissue observation was taken from the outer surface of the test material after the heat treatment so that the position of 5 mm in the diameter direction was the observation surface, and observed with a scanning electron microscope (magnification: 250x) to obtain a reflection electron image. It is confirmed that the white region is the super-pure carbide (M ₆ C type carbide in which W is concentrated). In the present invention, it can be seen that the super-pure carbide is dispersed at high density on the outer surface side of the test material (sleeve-shaped roll outer layer material).

For reference, the test material No. 11 (the present invention) was subjected to a heat treatment at a position (18 mm position) and a position (38 mm position) of 18 mm in the radial direction from the outer surface of the test material (sleeve- 38 mm), a specimen for composition analysis having a size of 5 mm in the radial direction and 10 mm x 10 mm in a plane parallel to the outer surface was taken from the position. Then, the composition at each position was analyzed by chemical analysis. The obtained results are shown in Table 2.

Further, with respect to the test piece No. 11 (the test piece), the test surface of the wear test piece was located at a position (18 mm position) in the radial direction from the outer surface of the test material after the heat treatment (18 mm position) (38 mm position). A wear test was conducted in the same manner as the above-mentioned conditions to measure the wear loss. The obtained results are shown in Table 3.

From the results shown in Table 2, on the outer surface of the test material (sleeve-shaped roll outer layer material), mainly W was concentrated, and a position 18 mm away from the outer surface by 18 mm, a position 38 mm away from the outer surface in the radial direction (At a position of 38 mm), the ratio of W decreases, and the proportion of Co, Fe, and the like increases, and it is apparent that the composition has an oblique composition. Therefore, as can be seen from Table 3, at a position (18 mm position) of 18 mm in diameter and a position (38 mm position) of 38 mm away from the outer surface, The abrasion resistance is lowered.

[Example 2]

Next, an embodiment of the above-described second embodiment will be described.

The molten metal having the composition shown in Table 4 was dissolved in a high frequency induction furnace, and a roll-shaped outer layer material (outer diameter: 250 mm phi, radial thickness: 55 mm) was cast as a test material by a centrifugal casting method. The casting temperature was 1450 to 1550 占 폚, and the centrifugal force was 140 to 220G as gravity multiple. In some of test materials (molten metal No.S), since significant carbide segregation occurred on the inner surface, 60 G was set for the purpose of reducing segregation. After the casting, the casting was reheated to 1050 to 1200 占 폚, held for 10 hours, and then cooled to 100 占 폚 or lower and tempered at 400 to 560 占 폚 to be cooled and heated once or twice . Thus, the hardness at a position of 5 mm in the thickness direction from the outer surface of the test material was adjusted to approximately 85 to 100 HZ. In addition, a commercially available centrifugal casting outer layer composition (high speed tool steel roll composition: 2.2% C-0.4% Si-0.4% Mn-5.3% Cr-5.2% Mo- 5.6% V -1.1% Nb) was melted in the same manner as in Example 1, and similarly, a roll outer layer material in the form of a sleeve was cast and subjected to heat treatment after casting to obtain a test sample (hardness 85 HS) .22).

A test piece for composition analysis, a test piece for abrasion test, a test piece for Young's modulus measurement, and a roll test piece for rolling load evaluation were collected from the heat treated test pieces. In addition, the test material No. 19 was very easy to crack, and it was very difficult to collect the test material.

The test specimen for composition analysis was prepared by grinding 5 mm in the radial direction from the outer surface of the test material after the heat treatment as described above and measuring 5 mm in the radial direction from the outer surface after grinding and 10 mm 10 mm in the plane parallel to the outer surface Size specimens were taken. The obtained test pieces were used to analyze each component element. Mn, Cr, and Mo were measured by atomic absorption spectrometry, Co was measured by the capacity method, and Fe was measured by the dosing method or the atomic absorption method.

The obtained results are shown in Table 5.

The abrasion test piece (60 mm in outer diameter x 10 mm in width) was sampled from the test piece after the heat treatment so that the center position of the width of the abrasion test piece was 10 mm in the radial direction from the outer surface of the test piece. As shown in Fig. 7, the abrasion test was carried out by a two-disc sliding transfer method of a test piece (abrasion test piece) and a counter material (material: S45C, outer diameter 190 mm? X width 15 mm).

In the abrasion test, a specimen rotated at 700 rpm (peripheral speed: 2.1 m / s) at a rotation speed of 700 rpm while rotating the test piece was rolled at a slide ratio of 14.2% while pressing a counterpart heated at 850 캜 with a load of 980 N. The electric power of the test piece was updated every 21,000 times, and the electric motor was rotated until the cumulative number of revolutions reached 168,000 times. After the end of the test, the wear loss of the wear test piece was examined. The ratio of the abrasion loss of each test piece to the standard (abrasion loss ratio = (abrasion loss amount of the conventional example) / ((abrasion loss amount of the conventional example) / Wear loss amount of the test material)) was calculated, and the abrasion resistance was evaluated. , &Quot;? &Quot;, "? &Quot;, and " x ", respectively, when the abrasion resistance ratio was 3 or more. Symbols " & cir & indicate very good, symbols " good ", and symbol " x "

The test piece for measuring the Young's modulus (φ16 × 5 mm thickness) was ground 5 mm in the radial direction from the outer surface of the test material after the above-mentioned heat treatment, and 5 mm in the radial direction from the outer surface after grinding, Mm. ≪ / RTI > Using the obtained test piece, the Young's modulus was measured by the ultrasonic method.

Further, a test specimen after the above-mentioned heat treatment was ground 10 mm in the radial direction from the outer surface, and a roll test piece (outer diameter 230 mm? Width 40 mm) having the surface after grinding as the outer surface was sampled, The composite roll was placed in a 4Hi thin plate cold rolling mill (back-up roll: external diameter 500 mm? X body length 40 mm), and a tensile force The rolling load was measured when a cold-rolled steel sheet having a strength of 590 MPa (plate width of 20 mm, plate thickness of 1.5 mm, length of 20 m) was subjected to cold rolling with a plate thickness reduction ratio of 20%. Based on the results, the reduction amount (= 100-the rolling load of the test material / the rolling load of the conventional example × 100) of the rolling load of each roll test piece relative to the reference was calculated on the basis of the rolling load of the test material No. 22 of the conventional example, The reduction effect of the rolling load is recognized when the rolling load is reduced by 10% or more.

The obtained results are shown in Table 6.

In Example 2, all of the examples according to the present invention had a wear resistance ratio of 2.1 or more, which markedly improved abrasion resistance as compared with the conventional example (high speed tool steel roll), and the rolled load was reduced by 10% or more as compared with the conventional example, Exhibits excellent rolling load reducing effect. On the other hand, in the comparative example deviating from the scope of the present invention, cracking occurred during the test, the wear resistance ratio was less than 2, the improvement of wear resistance was less than that of the conventional example, or the Young's modulus was less than 270 때문에, .

Further, the structure was observed with respect to Inventive Examples (No. 13 and No. 5) and is shown in FIG. A specimen for tissue observation was taken from the outer surface of the test material after the heat treatment so that the position of 5 mm in the diameter direction was the observation surface, and observed with a scanning electron microscope (magnification: 250x) to obtain a reflection electron image. It is confirmed that the white region is the super-pure carbide (M ₆ C type carbide in which W is concentrated). In the present invention, it can be seen that the super-pure carbide is dispersed at high density on the outer surface side of the test material (sleeve-shaped roll outer layer material).

For reference, the test material No. 11 (the present invention) was subjected to a heat treatment at a position (18 mm position) and a position (38 mm position) of 18 mm in the radial direction from the outer surface of the test material (sleeve- 38 mm), a specimen for composition analysis having a size of 5 mm in the radial direction and 10 mm x 10 mm in a plane parallel to the outer surface was taken from the position. Then, the composition at each position was analyzed by chemical analysis. The obtained results are shown in Table 5.

Further, with respect to the test piece No. 11 (the test piece), the test surface of the wear test piece was located at a position (18 mm position) in the radial direction from the outer surface of the test material after the heat treatment (18 mm position) (38 mm position), and the abrasion test was carried out in the same manner as in the above-mentioned conditions to measure the abrasion loss. The obtained results are shown in Table 6.

From Table 5, it can be seen that the outer surface of the test material (sleeve-shaped roll outer layer material) is mainly concentrated in W and is located at a position 18 mm away from the outer surface by 18 mm in diameter and 38 mm away from the outer surface in the radial direction (At a position of 38 mm), the ratio of W decreases, and the proportion of Co, Fe, and the like increases, and it is apparent that the composition has an oblique composition. Therefore, as can be seen from Table 6, at a position (18 mm position) of 18 mm in diameter and a position (38 mm position) of 38 mm away from the outer surface, The abrasion resistance is lowered.

Claims (21)

As a rolled roll material for W-Co based alloy rolling,
Wherein the W content is an inclined composition which decreases in the radial direction from the outer peripheral side of the roll toward the inner peripheral side and the surface of the outer rim at a position corresponding to the maximum diameter at the time of rolling is expressed by mass%
W: 25 to 70%
Co: 5 to 45%
C: 0.6 to 3.5%
Si: 0.05 to 3%
Mn: 0.05 to 3%
Mo: 1 to 15%
And the remainder is composed of unavoidable impurities. The method according to claim 1,
In addition to the above composition, in addition, by mass%
Fe: 5 to 40%
Cr: 0.1 to 10%
V: 0.1 to 6%
Nb: 0.1 to 3%
And at least one selected from the group consisting of iron oxide and iron oxide. 3. The method according to claim 1 or 2,
In addition to the above composition, in addition, by mass%
Ni: 0.05 to 3%
By weight based on the total weight of the roll. 4. The method according to any one of claims 1 to 3,
Wherein the rolled roll outer layer material is a centrifugal casting roll. A composite roll for rolling comprising an outer layer and an inner layer welded and integrated with the outer layer,
Wherein the outer layer is the rolling roll outer layer material according to any one of claims 1 to 3. An intermediate composite roll for rolling comprising an outer layer, an intermediate layer welded and integrated with the outer layer, and an inner layer welded and integrated with the intermediate layer,
Wherein the outer layer is the rolling roll outer layer material according to any one of claims 1 to 3. The method according to claim 5 or 6,
Wherein the outer layer is a centrifugal casting agent. An outer layer material which is a surface layer of a W-Co alloy rolling roll outer layer material having an inclined composition in which the W content decreases in the radial direction from the outer peripheral side of the roll toward the inner peripheral side and which corresponds to the maximum diameter at the time of rolling, %in,
W: 25 to 70%
Co: 5 to 45%
C: 0.6 to 3.5%
Si: 0.05 to 3%
Mn: 0.05 to 3%
Mo: 1 to 15%
And has a composition in which the content of W, Co, Mo and Fe satisfies the following formula (1) and the remainder is inevitable impurities.
group
(% W +% Mo) / (% Co +% Fe)? 9.0 [1]
Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element. 9. The method of claim 8,
Wherein a Young's modulus of the outer layer material to be a surface layer at a position corresponding to the maximum diameter at the time of rolling is not less than 270 占 and not more than 500 占.. 10. The method according to claim 8 or 9,
In addition to the above composition, in addition, by mass%
Fe: 5 to 40%
Cr: 0.1 to 10%
V: 0.1 to 6%
Nb: 0.1 to 3%
And at least one selected from the group consisting of iron oxide and iron oxide. 11. The method according to any one of claims 8 to 10,
In addition to the above composition, in addition, by mass%
Ni: 0.05 to 3%
By weight based on the total weight of the roll. The method according to any one of claims 8 to 11,
Wherein the rolled roll outer layer material is a centrifugal casting roll. A composite roll for rolling comprising an outer layer and an inner layer welded and integrated with the outer layer,
Wherein the outer layer is made of a W-Co based alloy and has an inclined composition in which the W content decreases in the radial direction from the outer peripheral side of the roll toward the inner peripheral side and the outer layer material serving as the surface layer at the position corresponding to the maximum diameter at the time of rolling is in a mass% in,
W: 25 to 70%
Co: 5 to 45%
C: 0.6 to 3.5%
Si: 0.05 to 3%
Mn: 0.05 to 3%
Mo: 1 to 15%
And the content of W, Co, Mo, and Fe satisfies the following formula (1) and the remainder is inevitable impurities.
group
(% W +% Mo) / (% Co +% Fe)? 9.0 [1]
Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element. 14. The method of claim 13,
Wherein the Young's modulus of the outer layer material to be the surface layer at the position corresponding to the maximum diameter at the time of rolling is 270 占 ㎬ to 500 占 ㎬. The method according to claim 13 or 14,
In addition to the above composition, in addition, by mass%
Fe: 5 to 40%
Cr: 0.1 to 10%
V: 0.1 to 6%
Nb: 0.1 to 3%
Or a combination thereof. 16. The method according to any one of claims 13 to 15,
In addition to the above composition, in addition, by mass%
Ni: 0.05 to 3%
By weight. An intermediate composite roll for rolling comprising an outer layer, an intermediate layer welded and integrated with the outer layer, and an inner layer welded and integrated with the intermediate layer,
Wherein the outer layer is made of a W-Co based alloy and has an inclined composition in which the W content decreases in the radial direction from the outer peripheral side of the roll toward the inner peripheral side and the outer layer material serving as the surface layer at the position corresponding to the maximum diameter at the time of rolling is in a mass% in,
W: 25 to 70%
Co: 5 to 45%
C: 0.6 to 3.5%
Si: 0.05 to 3%
Mn: 0.05 to 3%
Mo: 1 to 15%
Fe: 5 to 40%
Further, the composite roll for rolling has a composition in which the content of W, Co, Mo, and Fe satisfies the following formula (1) and the remainder is inevitable impurities.
group
(% W +% Mo) / (% Co +% Fe)? 9.0 [1]
Here,% W,% Mo,% Co, and% Fe are the content (mass%) of each element. 18. The method of claim 17,
Wherein the Young's modulus of the outer layer material to be the surface layer at the position corresponding to the maximum diameter at the time of rolling is 270 占 ㎬ to 500 占 ㎬. The method according to claim 17 or 18,
In addition to the above composition, in addition, by mass%
Fe: 5 to 40%
Cr: 0.1 to 10%
V: 0.1 to 6%
Nb: 0.1 to 3%
Or a combination thereof. 20. The method according to any one of claims 17 to 19,
In addition to the above composition, in addition, by mass%
Ni: 0.05 to 3%
By weight. 21. The method according to any one of claims 13 to 20,
Wherein the outer layer is a centrifugal casting agent.

Images