KR20190029876A - Equipment and method for endless hot strip rolling of difficult-to-joining steel - Google Patents

Abstract

A method for continuously hot rolling a nonjoining-material high grade steel is disclosed. A method for continuously hot rolling a nonjoining-material, according to one embodiment of the present invention, comprises the steps of: melting surface scales by coating a boron-based flux or a mixture of a fluorine-based flux and a boron-based flux on a joining region at which a plurality of rolling materials to be joined overlap; and overlapping both ends of a plurality of rolling materials so as to perform shear deformation.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a continuous hot-

The present invention relates to an apparatus and a method for continuous hot rolling of an unbonded material which are difficult to be bonded to each other.

In recent years, various continuous continuous rolling techniques have been developed to enable continuous rolling of the finish rolling by joining a line and a trailing plate between a rough rolling mill and a finishing rolling mill. Among them, a technique of overlapping the rear end portion of the leading metal plate with the front end portion of the trailing metal plate and vertically overlapping the overlapped portions of the metal sheet to simultaneously bond the front surfaces of the metal sheets produced in the shearing process.

The technique of joining by direct contact described above has many merits as a continuous continuous rolling technique such as simple joining by shearing, joining in a short time, small space required, and low temperature drop during rolling I have.

However, in the case of joining high-grade steel using the above-mentioned conventional joining technique, there is a problem that it is difficult to secure the ductability of the high-grade steel due to the lowered bonding strength ratio. Generally, in order to ensure the ductility of high-grade steel during continuous continuous rolling, the bonding strength ratio should be 70% or more. In the case of high-grade steel, a large scale is generated on the surface due to the alloy component, It is not. For example, Si-based scale or Cr-based scale is produced on the surface of high carbon steel, electric steel plate and stainless steel, which is one kind of high-grade steel. Particularly, Si-based scale and Cr-based scale are difficult to remove.

Korean Patent Publication No. 10-2012-0075308 (published Jul. 6, 2012)

It is an object of the present invention to provide an apparatus and method for continuous hot rolling an unbonded material capable of improving the rate of rolling of a joint of an unbonded material.

According to one aspect of the present invention, there is provided a reheating furnace for regulating the temperature of a rolled material; A roughing mill for rolling the rolled material passing through the reheating furnace; A joining device for joining the preceding rolling material and the succeeding rolling material passed through the rough rolling mill to each other; A finishing mill to produce a rolled material having passed through the joining apparatus to a required thickness; And a first coating device disposed in front of the reheating furnace or between the roughing mill and the joining device to form a surface coating layer on the rolled material.

And a second application device disposed at the other side of the reheating furnace or between the roughing mill and the joining device.

The surface coating layer may be composed of a boron-based flux or a mixture of a boron-based and a fluorine-based mixed flux.

According to another aspect of the present invention, there is provided a method of manufacturing a steel sheet, comprising: a coating step of forming a surface coating layer on at least one of a preceding rolling material or a following rolling material and melting a scale; A superimposing step of overlapping the preceding rolled material and the subsequent rolled material including the portion where the surface coating layer is formed; And a joining step of shearing the superimposed rolled material by shear deformation.

The rolling material may be a high-grade steel slab or a metal bar containing a large amount of at least one selected from the group consisting of Si and Cr.

The high grade steel slab or metal bar may be Si steel or high alloy steel of electrical steel sheet material.

The surface coating layer may have a width of 50 mm or more in the rolling direction.

The surface coating layer may be formed over the entire width of the rolled material perpendicular to the rolling direction.

The surface coating layer may be spatially formed at a predetermined interval perpendicular to the rolling direction.

The flux forming the surface coating layer may be composed of a boron-based flux or a mixed flux of boron-based and fluorine-based fluxes.

The flux may be in the form of a liquid or gaseous form of solid or liquid form in the form of a powder or a mixture of the forms.

The flux can be applied to the joint by spraying or by gravity.

The method may further include reheating and rough rolling the rolled material having the surface coating layer formed thereon at a temperature of 1,100 to 1,300 for 1 to 5 hours between the applying step and the superposing step.

The apparatus and method for continuous hot rolling an unbonded material according to the present invention are characterized in that an oxide removing flux is applied to the surface of a bonding target portion of a rolled material before or after hot rolling to remove a surface scale, It is possible to increase the strength of the joint at the time of joining and to secure the joining strength ratio of 70% or more, thereby improving the joining rolling stock rate.

1 is a conceptual diagram of an unbonded material continuous hot rolling apparatus according to an embodiment of the present invention.
2 is an adapter according to an embodiment of the present invention.
3 is a perspective view for explaining a conventional advanced steel continuous hot rolling method.
4 is a perspective view for explaining a high-strength steel continuous hot rolling method according to an embodiment of the present invention.
5 is a perspective view for explaining a flux application surface according to an embodiment of the present invention.
FIGS. 6 to 8 are graphs for explaining the bond strength ratios according to the continuous annealing method for unbonded materials according to the embodiments of the present invention.
9 is a graph for explaining the cracking rate of a joint according to a continuous hot rolling method of an unbonded material according to a thirteenth embodiment of the present invention.
10 is a graph for explaining the bonding strength ratio of the high alloy steel according to the continuous hot rolling method of the unbonded material according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a continuous hot rolling apparatus for continuous joining quaternaries according to an embodiment of the present invention; FIG. 2 is a view for explaining an adapter according to an embodiment of the present invention. Hereinafter, an unbonded material continuous hot rolling apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

1, the continuous joining material hot rolling apparatus according to the present invention comprises a reheating furnace 10 for heating a material from an upstream side, a rough rolling mill 20 composed of a plurality of rolling mills, a coil box 30, A joining device 40, a finishing mill 50 composed of a plurality of rolling mills, and a down coiler 60. Hereinafter, the non-bonded material will be described by taking as an example a high-grade steel which is difficult to be joined due to scale generation.

The rough rolling mill 20 rolls a high-grade steel slab, which is an unbonded material, to produce a high-grade steel metal bar, and the produced metal bar is wound in a coil state in a coil of the coil box 30. At this time, the coil box 30 also plays a role of adjusting the speed difference of the metal bars running in the roughing mill 20 and the finishing mill 50.

After the tip of the trailing rolled material 2 unwound from the coil box 30 is cut by the crumb shear, the surface of the portion to be joined of the metal bar to be joined is descaled by the partial descaling device 70, 40 are superposed on the rear end of the preceding rolling material 1 in the superposition device 41. [

The front end of the following rolled material 2 and the rear end of the preceding rolled material 1 are joined at the joinder 100 of the joining apparatus 40 and the cropping of the joining portion is cut by the crop processing apparatus 80. The metal bar 200 joined at the joining device 40 is conveyed to the finishing mill 50.

Here, the joining apparatus 40 is a facility for joining the rear end of the preceding rolled material 1 and the front end of the following rolled material 2 in a running state, and can be a short-time joining apparatus capable of shear joining in a short time. In order to perform the front end joining of the rolled materials 1 and 2 in the running state, the joinder 40 can move according to the running of the metal bar, and a facility for the joinder 40 to rock according to the running of the metal bar Can be added.

For example, the joining device 100 of the joining device 40 clamps a portion where the rear end of the preceding rolled material 1 and the front end of the following rolled material 2 are clamped, And a pair of shearing blades for press-fitting and shear-joining while being sheared.

The metal bar 200 transferred to the finishing mill 50 is hot-rolled sequentially through a plurality of rolling mills to have a required thickness and then wound on the down coiler 60.

Levels 90 and 91 may be provided with a first level 90 and a second level 91 on the outlet side of the coil box 30 and the joining device 40, And can be selectively disposed according to the hot rolling condition.

The application device includes a first application device (not shown) installed in front of the reheating furnace 10 and a second application device 300 disposed between the roughing mill 20 and the joining device 40, The surface coating layer 3 can be formed on the rolled material to be bonded.

The rolled material 1, 2 may be a high-grade steel slab or a metal bar containing a large amount of at least one selected from the group consisting of Si and Cr. For example, the rolled material (1, 2) may be high carbon steel, high alloy steel, silicon steel for electric steel sheet or stainless steel.

The surface coating layer 3 may be formed in a slab state by using a pre-reheating flux applying apparatus using a reheating furnace 10, or may be formed by rough rolling in a roughing mill 20 and finishing rolling in a finish rolling mill 50 The flux applying device 300 can be formed on the metal bar. Furthermore, the surface coating layer 3 may be formed on the metal bar in the step between the pre-reheating slab and the rough rolling and finishing rolling. At this time, the width of the surface coating layer 3 may be formed on the entire width of the rolled material 1, 2 at a width of 50 mm at both ends in the rolling direction of the rolled materials 1, 2. That is, the surface coating layer 3 may be formed to have a width of 50 mm wide by the width of the rolled material 1, 2.

2, an adapter 100 according to an embodiment of the present invention mainly includes an upper blade assembly 120, a lower blade assembly 130, and a housing 110 for movably supporting the upper blade assembly 120 and the lower blade assembly 130. [

The upper blade assembly 120 comprises an upper blade 121, an upper clamp 122 and an upper support device 123, all of which may be integrally constructed. The lower blade assembly 130 disposed at the lower portion of the upper blade assembly 120 includes a lower blade 131, a lower clamp 132, and a lower support device 133, .

The upper blade aggregate 120 and the lower blade aggregate 130 are guided by the housing 110 and can be movably supported in the thickness direction of the preceding rolling material 1 and the trailing rolling material 2. [ Further, the upper blade aggregate 120 and the lower blade aggregate 130 may be configured to approach each other or away from each other by a link mechanism (not shown).

The operation of the adapter 100 will be briefly described. The leading end 2 'of the trailing rolled material 2 is guided to the inside of the adapter 100 in a superposed state on the trailing end 1' of the advanced rolled material 1 of the advanced steel. The portion where the leading edge 2 'and the trailing edge 1' are overlapped is interposed between the protrusions 124 and 134 of the upper blade 121 and the lower blade 131. That is, the projections 124 and 134 of the upper blade and the lower blade come into contact with the surfaces of the tip 2 'and the rear end 1'.

The upper clamp 122 and the lower clamp 132 are brought into contact with each other at a position where the rear end 1 'of the preceding rolled material 1 and the front end 2' of the following rolled material 2 overlap each other. Here, the upper clamp 122 is supported by the upper support device 123 by hydraulic pressure, and the lower clamp 132 is supported by the lower support device 133 by hydraulic pressure.

When the upper blade 121 and the lower blade 131 shear the preceding rolling material 1 and the succeeding rolling material 2 in this state, the front rolling material 1 and the succeeding rolling material 2, And the end faces are shear-jointed to each other by the plastic flow deformation, thereby forming the metal bar 200 integrally joined continuously.

When the end portion of the advanced steel is completed, the upper end of the trailing rolled material 2 is cut off and the rear end of the preceding rolled material 1 is positioned on the joined portion of the continuous metal bar 200 1 ') is cut. When the metal bars 200 are connected to each other, the upper blade 121 and the lower blade 131 are retracted until they have a predetermined distance from each other.

The upper and lower cuts cut according to the shear joining of the metal bar are removed by the crop processor 80 shown in FIG. 1, and the continuous metal bar 200 is fed to the finishing mill 50. Here, when the joining portion of the metal bar passes through the finishing mill 50, since the strong compressive stress and bending at the time of finishing rolling and the external force such as bending or tensile acts between the stands of the finishing mill, . At this time, it is necessary to maintain the bonding strength to such an extent that the joint of the high-grade steel metal bar can pass through the finishing mill 50 without breaking.

FIG. 3 is a perspective view for explaining a conventional advanced steel continuous hot rolling method, and FIG. 4 is a perspective view for explaining an advanced steel continuous hot rolling method according to an embodiment of the present invention.

Referring to FIG. 3, in the case of high-grade steel, when reheating is performed before hot rolling by an alloy component, a large amount of scale is generated on the surface, and they are difficult to be removed by descaling work. Especially, It is formed on the surface of the base material with an inner scale, and removal thereof is difficult, so that a large amount remains on the surface.

In the case of high-grade steels containing a large amount of Si or Cr, such as high carbon steel, electric steel or stainless steel, a Si-based scale or a Cr-based scale is formed on the surface. However, such scale is difficult to be removed even by descaling work, Remains. In addition, in the case of Si-based scale, Si is penetrated into the base material and fayalite (Fe ₂ SiO ₄ ) is formed, and descaling is further lowered. At this time, fayalite (Fe ₂ SiO ₄ ) increases as the content of Si increases do.

The inner scale or fayalite (Fe ₂ SiO ₄ ) formed on the surface of the reheated slab is concentrated between the interface of the base material and the outer scale through rough rolling. Therefore, when a steel slab having such a scale is subjected to the shear joining as shown in Fig. 3, there is a problem that a large amount of scale is mixed into the joining surface to lower the joining strength ratio of the joining portion.

On the other hand, an unbonded material continuous hot rolling method in which both ends of a plurality of rolled materials 1 and 2 according to the embodiment of the present invention disclosed in FIG. 4 are overlapped and subjected to shear deformation and joining are formed by forming a surface coated layer on the rolled material An overlapping step of superimposing the preceding rolled material and a subsequent rolled material including a portion where the surface coated layer is formed, and a bonding step of shear deformation of the overlapped rolled material can be sequentially performed.

Therefore, in the present invention, the surface coating layer 3 is formed by using a boron-based or fluorine-based boron-based flux at a joint portion of any one of both ends where the rolled materials 1 and 2 are overlapped in the application step, It is possible to increase the strength of the joining portion in the front end joining of the continuous hot rolled material by removing the scale on the surface of the joining planned portion of the material. At this time, the scale may be generated by including a large amount of at least one selected from the group consisting of Si and Cr in the rolled material (1, 2).

The surface coating layer 3 may be formed in a slab state using a first coating device (not shown) before reheating using the reheating furnace 10 of Fig. 1, or may be formed in a second coating device 300 may be used to form the metal bar. Furthermore, the surface coating layer 3 may be formed on the metal bar in the step between the pre-reheating slab and the rough rolling and finishing rolling. At this time, the width of the surface coating layer 3 may be formed to be 50 mm wide from both ends in the rolling direction of the rolling material 1, 2.

On the other hand, when the width of the surface coating layer 3 is less than 50 mm, there may occur a problem that the strength of the joining portion between the preceding rolled material 1 and the succeeding rolled material 2 is not sufficient. May be formed to be 100 to 500 mm.

5 (a), 5 (b) and 5 (c) are perspective views for explaining a surface coating layer according to an embodiment of the present invention. First, referring to FIG. 5A, the surface coating layer 3A may be formed over the entire rolling direction of the rolled material 1, 2. For example, the surface coating layer 3A may be formed over the entire width direction of the rolled material 1, 2.

5 (b) and 5 (c), the surface coating layers 3B and 3C may be provided so as to have a predetermined interval perpendicular to the rolling direction of the rolling materials 1 and 2. For example, the surface coating layers 3B and 3C may have a specific pattern in the width direction of the rolled materials 1 and 2. For example, the surface coating layer 3B may be formed only at both edge portions (end portions) in the width direction of the rolled materials 1 and 2 as shown in Fig. 5 (b) It is possible to further reduce the cost. 5 (c), the surface coating layer 3C may be formed at a predetermined interval in two or more areas in the width direction of the rolled materials 1 and 2, It is possible to further reduce the cost.

Further, the flux of the surface coating layer 3 may be in the form of a gas or a mixed form of liquid or gas in solid or liquid form in powder form. The method of forming the surface coating layer 3 of the method of shearing the advanced steel continuous hot rolled material may include a spraying method or a dropping method by gravity at the joining portion.

Meanwhile, the embodiment of the present invention may include the first to fourteenth embodiments according to the method and time of formation of the surface coating layer 3, and the like. For example, according to the method of forming the surface coating layer 3 according to the first embodiment, the surface coating layer 3 can be formed at the bonding site before the reheating furnace 10. Then, the rolled material 1 having the surface coating layer 3 formed thereon can be subjected to reheating and rough rolling at a temperature of 1,100 to 1,300 for 1 to 5 hours.

According to the method of forming the surface coating layer 3 according to the second embodiment, a surface coating layer is formed at the joint portion between rough rolling and finishing rolling. According to the method of forming the surface coating layer 3 according to the third embodiment, the step of forming the surface coating layer 3 at the joint site before the reheating furnace, and the step of forming the surface coating layer 3 at the joint portion between the rough rolling and finishing rolling, .

Hereinafter, the present invention will be described in more detail through Examples 1 to 14.

Example 1 (3.4 % Si electric steel plate: flux applied to reheat slab)

Borax, a boron-based flux, was applied to a shear bond portion of a 3.4% Si electrical steel slab having a thickness of 250 mm, a width of 1,200 mm and a length of 10,000 mm to a coverage area of 500 mm in the longitudinal direction and 1000 mm in the width direction. The coating amount per unit area was 0.6 kg / m ² . The slab was reheated at a temperature of 1,200 DEG C for 3 hours and subjected to rough rolling. Shear bond was then performed and the bond strength was evaluated.

Example 2 (3.4 % Si electrical steel sheet: flux applied to metal bar after rough rolling)

A boron-based flux, borax, was applied to the shear bond of a 3.4% Si electrical steel sheet metal bar, which had been rolled, to a coverage area of 2000 mm in the lengthwise direction and 1200 mm in the widthwise direction. The coating amount per unit area was 0.6 kg / m ² . Shear bond was then performed and the bond strength was evaluated.

Example 3 (3.4 % Si electrical steel plate: flux applied to reheat slab + flux applied to metal bar after rough rolling)

Borax, a boron-based flux, was applied to a shear bond portion of a 3.4% Si electrical steel slab having a thickness of 250 mm, a width of 1,200 mm and a length of 10,000 mm to a coverage area of 500 mm in the longitudinal direction and 1000 mm in the width direction. The coating amount per unit area was 0.6 kg / m ² . The slab was reheated at a temperature of 1,200 DEG C for 3 hours and subjected to rough rolling. 3.4 Boron-based flux, borax, was applied to the shear bond of the metal bar of 3.4 Si electric steel sheet after the rough rolling to a coverage area of 2000 mm in lengthwise direction and 1200 mm in widthwise direction. The coating amount per unit area was 0.6 kg / m ² . Shear bond was then performed and the bond strength was evaluated.

Examples 4 to 6 (3.4 % Si electric steel plate: fluorine-based 40% + boron-based 60% mixed flux)

Shear bonding was carried out in the same manner as in Examples 1 to 3 except that the fluorine-based 40% + boron-based 60% mixed flux was used instead of the boron-based flux, borax.

Example 7 (3.2% Si electric steel sheet: Borax-based flux borax applied)

Shear bonding was performed in the same manner as in Example 2 except that an electric steel sheet containing 3.2% Si was used instead of the electric steel sheet containing 3.4% Si, and the strength of the joint was evaluated.

Example 8 (3.2% Si electric steel plate: fluorine-based 40% + boron-based 60% mixed flux)

Shear bonding was carried out in the same manner as in Example 7 except that the fluorine-based 40% + boron-based 60% mixed flux was used instead of the boron-based flux, borax, and the strength of the joint was evaluated.

Example 9 (3.2% Si electric steel plate: fluorine-based 20% + boron-based 80% mixed flux)

Shear bonding was carried out in the same manner as in Example 7 except that a fluorine-based 20% + boron-based 80% mixed flux was used instead of the boron-based flux, borax, and the strength of the joint was evaluated.

Example 10 (Application amount per unit area: 1.2 kg / m ² )

And it is in the same manner as Example 2 except for applying the coating amount per unit area 0.6kg / m ² instead of the coating amount per unit area 1.2kg / m ² was carried out in the shear joint and evaluate the joint strength.

Example 11 (application amount per unit area: 0.3 kg / m ² )

Shear bonding was carried out in the same manner as in Example 2 except that the application amount per unit area of 0.3 kg / m ² was applied instead of the application amount per unit area of 0.6 kg / m ² , and the strength of the joint was evaluated.

Example 12 (application amount per unit area: 0.15 kg / m ² )

Shearing was performed in the same manner as in Example 2 except that the application amount per unit area was 0.15 kg / m ² instead of the application amount per unit area of 0.6 kg / m ² , and the strength of the joint was evaluated.

Example 13 (Evaluation of Joint Cracking Rate)

After the shear joint was performed in the same manner as in Example 2, the joint portion was subjected to rolling to evaluate the joint cracking rate.

Example 14 (Evaluation with high alloy steel)

Comparative Example 1

An electric steel slab containing 3.4% of Si having a thickness of 250 mm, a width of 1,000 mm and a length of 10,000 mm was subjected to reheating and rough rolling at a temperature of 1,200 for 3 hours. Shear bond was then performed and the bond strength was evaluated.

Comparative Example 2

An electric steel slab containing 3.2% of Si having a thickness of 250 mm, a width of 1,000 mm and a length of 10,000 mm was subjected to reheating and rough rolling at a temperature of 1,200 for 3 hours. Shear bond was then performed and the bond strength was evaluated.

Comparative Example 3

After performing shear bonding in the same manner as in Comparative Example 1, the joint portion was subjected to hot rolling to evaluate the cracking ratio at the joint portion. It can be seen that the fracture occurs at the joint immediately after the bonding due to the Si-based scale of the surface layer during the high-strength steel shear bonding.

Comparative Example 4

Evaluated with high alloy steel

Steel grade Example
/ Comparative Example Application method (position) Flux
Kinds Flux
Application amount
(kg / m ² ) join
Intensity ratio
(%) copula
Crack rate
(%) 3.4% Si
Electric steel sheet Example 1 Ash heat slab borax 0.6 85.4 - Example 2 Metal bar after rough rolling borax 0.6 88.2 - Example 3 Ash heat slab
+ Metal bar after rough rolling borax 0.6 97.4 - Example 4 Ash heat slab Fluorine 40%
+ Boron-based 60% 0.6 75.0 - Example 5 Metal bar after rough rolling Fluorine 40%
+ Boron-based 60% 0.6 82.4 - Example 6 Ash heat slab
+ Metal bar after rough rolling Fluorine 40%
+ Boron-based 60% 0.6 90.1 - 3.2% Si
Electric steel sheet Example 7 Metal bar after rough rolling borax 0.6 99.4 - Example 8 Metal bar after rough rolling Fluorine 40%
+ Boron-based 60% 0.6 95.9 - Example 9 Metal bar after rough rolling Fluorine 20%
+ Boron based 80% 0.6 91.1 - 3.4% Si
Electric steel sheet Example 10 Metal bar after rough rolling borax 1.2 88.6 - Example 11 Metal bar after rough rolling borax 0.3 87.4 - Example 12 Metal bar after rough rolling borax 0.15 80.9 - Example 13 Metal bar after rough rolling borax 0.6 - 23.7 High alloy steel Example 14 Metal bar after rough rolling borax 0.6 87.6 - 3.4% Si
Electric steel sheet Comparative Example 1 - - - 0 - 3.2% Si
Electric steel sheet Comparative Example 2 - - - 0 - 3.4% Si
Electric steel sheet Comparative Example 3 - - - - 100 High alloy steel Comparative Example 4 - - - 63.4 -

Here, the bonding strength ratio represents a value obtained by dividing the bonding strength by the base metal strength as a result of a tensile test. The cracking rate of the joint represents the crack size of the joint divided by the total width of the work.

6 to 8 are graphs for explaining the bonding strength ratios of high-grade steel according to the advanced steel continuous hot-rolling method according to an embodiment of the present invention.

Fig. 6 is a graph comparing the bonding strength ratios of the electric steel sheets containing 3.4% or more of Si in Examples 1, 2 and 3 and Comparative Example 1. Fig. These are the bond strength ratios of the materials which were shear-bonded using a coating layer coated with a boron-based flux on the rolled material. Accordingly, the bonding strength ratio of the shear bonded material is improved compared to the shear bonding method according to Comparative Example 1, that is, without applying the flux, and exhibits an average bonding strength ratio of 90% or more.

Both when applied to the surface of the slab before reheating or when it is applied to the surface of the metal bar after rough rolling or when it is applied to the surface of the slab before reheating and subjected to second rolling on the surface of the metal bar after rough rolling. In particular, the highest bond strength ratio is obtained when the composition is applied to the surface of the slab before reheating, followed by second application to the surface of the metal bar after rough rolling.

Fig. 7 is a graph comparing the bonding strength ratios of the electric steel sheets containing 3.4% or more of Si in the above-described Example 2 and Example 5 and Comparative Example 1. Fig. These are the bond strength ratios of the materials which were shear-bonded using a coating layer formed by applying a boron-based flux or a fluorine-based and boron-based mixed flux to the rolled material in a metal bar state after rough rolling. As a result, a relatively high bonding strength ratio is obtained when a single boron flux is applied than when a fluorine-based and boron-based mixed flux is applied.

8 is a graph comparing bonding strength ratios of the electric steel sheets containing 3.2% or more of Si in Examples 7, 8, and 9 and Comparative Example 2. Fig. These are the bond strength ratios of the materials which were shear-bonded using a coating layer formed by applying a boron-based flux or a fluorine-based and boron-based mixed flux to the rolled material in a metal bar state after rough rolling. The highest bond strength ratio is obtained when a single boron-based flux is applied than when a fluorine-based and boron-based mixed flux is applied.

9 is a graph comparing the cracking ratios of the joints of Example 13 and Comparative Example 3 of an electrical steel sheet containing 3.4% or more of Si. These are the cracking ratios of the joints after shearing and the cracks of the joints when the flux is not used, by using a coating layer coated with a boron-based flux on the rolled material. It can be seen that the cracking rate of the joint is 100% due to the fracture at the joint immediately after the joint due to the Si scale of the surface layer in the conventional high strength steel shear joint.

10 is a graph comparing the bonding strength ratios of the high alloy steel containing Si of 0.2% or more and Cr of 0.3% or more in Example 14 and Comparative Example 4. These are the bond strength ratios of the material sheared beforehand using a coated layer coated with a boron-based flux on the rolled material in a metal bar state after rough rolling. The bonding strength ratio when flux is applied shows the high bonding strength ratio compared with the conventional one. Referring to this, it can be seen that the flux affects not only the Si-based scale but also the Cr-based scale.

Therefore, according to each of the above-described embodiments, in the continuous hot rolling method for unbonded materials according to the present invention, the oxide removal flux is applied to the surface of the rolled material to be joined before or during the hot rolling, It is possible to increase the strength of the joint portion in the front end joining of the continuous hot rolled material and to secure the joining strength ratio of 70% or more, thereby improving the joining portion rolling stock rate.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited thereto. Those skilled in the art will readily obviate modifications and variations within the spirit and scope of the appended claims. It will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

1: leading metal bar 2: trailing metal bar
3: surface coating layer 10: reheating furnace
20: rough rolling mill 30: coil box
40: joining device 41: superposition device
50: finishing mill 60: down coiler
70: descaling device 80: crop processing device
90: Level 1, Level 91: Level 2
100: adapter 110: housing
120: upper blade aggregate 121: upper blade
122: upper clamp 123: upper support device
124: first projection 130: lower blade aggregate
131: lower blade 132: lower clamp
133: lower support device 134: second projection
200: metal bar 300: dispensing device

Claims (13)

A reheating furnace for regulating the temperature of the rolled material;
A roughing mill for rough rolling the rolled material having passed through the reheating furnace;
A joining device for joining the preceding rolling material and the succeeding rolling material passed through the rough rolling mill to each other;
A finishing mill to produce a rolled material having passed through the joining apparatus to a required thickness; And
And a first coating device disposed in front of the reheating furnace or between the roughing mill and the joining device to form a surface coating layer on the rolled material to be bonded to the joining material continuous hot rolling device. The method according to claim 1,
And a second coating device disposed on the other side of the reheating furnace or between the roughing mill and the joining device to form a surface coating layer on the rolled material to be joined. 3. The method according to any one of claims 1 to 3,
Wherein the surface coating layer comprises a boron-based flux or a mixed flux of boron-based and fluorine-based materials. A continuous hot rolling method in which rolling materials are joined to continuously perform rolling,
A coating step of forming a surface coating layer on the rolled material and melting the scale;
A superimposing step of overlapping the preceding rolled material and the subsequent rolled material including the portion where the surface coating layer is formed; And
And a joining step of shearing the overlapped rolled material by shear deformation. 5. The method of claim 4,
Wherein the rolling material comprises a large amount of at least one selected from the group consisting of Si and Cr. 6. The method of claim 5,
Wherein the high-grade steel slab or the metal bar is a Si steel or a high alloy steel of an electric steel sheet material. 5. The method of claim 4,
Wherein the surface coating layer is formed to a width of 50 mm or more in the rolling direction. 5. The method of claim 4,
Wherein the surface coating layer is formed over the entire width perpendicular to the rolling direction. 5. The method of claim 4,
Wherein the surface coating layer is spatially formed at a predetermined interval perpendicular to the rolling direction. 5. The method of claim 4,
Wherein the flux forming the surface coating layer is composed of a boron-based flux or a mixed flux of a boron-based and a fluorine-based alloy. 11. The method of claim 10,
Wherein the flux is a liquid in the form of a liquid or a liquid in the form of a powder or a gas in the form of a liquid, or a mixture of the forms. 11. The method of claim 10,
Wherein the flux is applied to the joint by spraying or by gravity. 5. The method of claim 4,
Further comprising a step of reheating and rough rolling the rolled material having the surface coating layer formed thereon at a temperature of 1,100 to 1,300 for 1 to 5 hours between the application step and the superposition step.

Images