JPH01252704A - Complex member and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a complex member of rolling roll, etc., having excellent wear resistance, surface roughening resistance, seizure resistance and high toughness by forming high alloy steel sintered layer composing of martensite or bainite dispersing and precipitating metallic carbide as the matrix on surface of steel-made base material. CONSTITUTION:At the time of manufacturing the hot rolling roll and cold rolling roll, cylindrical metal capsule material C is inserted to the cylindrical steel material 10 as the roll base material and joined by welding. Powder P of the high alloy steel containing 2-3.5wt.% C, <0.4wt.% Si, <0.4wt.% Mn, 3-6wt.% Cr, 6-12wt.% V, 5-14wt.% W, 7-14wt.% Co and 3-9wt.% Mo is packed into gap between the capsule material C and the roll base material 10 and after degassing, it is sintered with hot isostatic pressing sintering method and quenched from 1,050-1,250 deg.C and tempered at 500-600 deg.C. The complex member of rolling roll, etc., providing the sintered metal layer having structure, in which hard MC type or M6C type metallic carbide having <=10mum grain size is uniformly dispersed and precipitated under extremely fine state in the martensite or bainite matrix, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a composite member having a laminated structure of a metal base material and a sintered alloy layer, and a method for manufacturing the same.

[Conventional technology]

The surface of the body of a roll for hot rolling or cold rolling has low wear, is less prone to roughness (cracks, unevenness, chips, etc.), and is less likely to seize with the rolled material. is necessary. Traditionally, cast iron rolls with bodies made of cast iron have been used as rolls for hot rolling, and forged steel rolls with bodies made of forged steel have been used as rolls for cold rolling. In order to improve the properties, the body of cast iron rolls is made of high alloy, cementite,
Hardness is increased by crystallizing double carbides, double carbides, and other special carbides.On the other hand, in forged steel rolls, high alloying of the body and heat treatment of quenching and tempering result in martensitic transformation, bainitic transformation, and secondary hardening. etc., in order to increase the hardness. In addition to the above, the cold rolling roll may also contain alloy powder (C:l, 3-3%, C
It has also been proposed to use a sintered crystal made of sintered materials (r: 15-21%, W+2Mo: 8% or less) (Japanese Patent Laid-Open No. 58-213856).

[Problem to be solved by the invention]

The body of both cast iron rolls and forged steel rolls is
Manufactured using cast material. These cast products generally have coarse fibers, and the carbide exhibits a coarse net-like crystallization form. The body of a cast iron roll has this coarse cast structure almost as it is, while forged steel rolls undergo structure changes due to processing and heat treatment, but are influenced by the original cast structure, so the structure changes. It is relatively coarse.

Therefore, although these rolls have relatively good wear resistance, they have a problem of being inferior in mechanical properties such as toughness and ductility. On the other hand, the sintered material of the alloy powder has a dense and fine structure, and has excellent mechanical properties as well as wear resistance and roughness resistance that exceed those of cast iron rolls and forged steel rolls. It has the disadvantage that it tends to seize with the material.

In view of the above, the present invention provides a composite member having surface properties such as abrasion resistance, roughening resistance, and seizure resistance suitable for use as rolling rolls, etc., as well as good mechanical properties, particularly toughness, and a method for manufacturing the same. This is what we are trying to provide.

[Means and effects for solving the problems] The composite member of the present invention is composed of a metal base material and a sintered alloy layer laminated at key points on the surface of the metal base material, and the sintered alloy layer has a C:2 to 3.5
%, Si: 0.4% or less, Mn: 0.4% or less, Cr:
3-6%, V: 6-12%, W: 5-14%, Conia ~14%, Mo: 3-9%, the remainder consists essentially of Fe, with a grain size of 10% on the martensite or bainite base.
It is characterized by having a metal structure in which MC type and/or M6C type carbides of μm or less are dispersed and precipitated.

Hereinafter, regarding the present invention, the reason for limiting the components of the sintered alloy layer will be explained first. % is by weight.

C: 2-3.5% C increases the hardness of the sintered alloy by forming a solid solution in the matrix and also combining with ■ and W to form carbides. The reason why the lower limit of cl is set to 2% is that if it is less than that, the balance of cl necessary for the formation of carbides of V and W will be poor, and the effect of highly alloying the sintered alloy will not be sufficiently obtained. On the other hand, if it exceeds 3.5%, the toughness decreases due to the coarsening of the carbides of ■ and W. Therefore, it was set at 2 to 3.5%.

Si: 0.4% or less Si improves the hardenability of sintered alloys, but since it has little involvement in secondary hardening through tempering, the effect of improving high-temperature hardness is small. Addition is sufficient.

Mn: 0.4% or less Mn is an element that improves the hardenability of sintered alloys, but secondary hardening cannot be expected through tempering treatment, so the effect of improving high-temperature hardness is small, and therefore up to 0.4%. The addition of is sufficient.

Cr: 3 to 6% Cr is an element that is dissolved in the matrix of the sintered alloy to greatly improve hardenability and exhibits temper softening resistance. To obtain this effect, it is necessary to add 3% or more. However, increasing the amount of Cr leads to a decrease in the seizure resistance of the sintered alloy.
Particularly in applications such as hot rolling rolls, if it exceeds 6%, problems of seizure will occur in practice. Therefore, the amount of Cr is 3
~6%.

V: 6-12% (1) is one of the most important elements characterizing the composition of the sintered alloy in the present invention. That is, ■ is dissolved in the matrix of the sintered alloy, and when tempered after quenching, it precipitates as fine MC-type carbides, causing a remarkable secondary hardening phenomenon, and also shows resistance to tempering softening. . Also,
It contributes to the refinement of the sintered alloy structure and the improvement of mechanical properties such as toughness. Even if the amount added is small (less than 6%), the effect of improving mechanical properties by refining the structure can be obtained. Additions of at least 6% are required to obtain wear resistance.

The effect increases as the amount added increases, but if it exceeds 12%, the precipitated carbides become coarse, mechanical properties such as toughness deteriorate, and machinability deteriorates.

Therefore, VjJ was set to 6 to 12%.

W: 5 to 14% W is an important element along with the above-mentioned (2). That is, W is a strong carbide-forming element, solidly dissolved in the matrix, and finely precipitated as MC type carbide by tempering treatment, causing remarkable secondary hardening. It also shows resistance to temper softening. The lower limit of the amount added is set to 5% because if it is less than that, the amount of MC type carbide precipitated will be insufficient and sufficient secondary hardening will not be achieved. The effect increases as the amount added increases, but when it exceeds 14%, mechanical properties such as toughness deteriorate due to coarsening of precipitated carbides. Therefore, 5~
It was set at 14%.

Co: 7 to 14% Co promotes the precipitation of carbides during tempering treatment and the strengthening of the sintered alloy by making the matrix into secondary martensite, and is effective in improving high-temperature hardness. To achieve this effect, an addition of at least 7% is required, but 14
%, the effect is almost saturated. Therefore, 7-1
It was set at 4%.

Mo: 3 to 9% Mo not only improves hardenability but also forms fine carbides during tempering treatment to cause significant secondary hardening, and is effective in maintaining high-temperature hardness. If the amount added is less than 3%, the effect is not sufficient, while if it exceeds 9%, the effect is almost saturated. Therefore, it was set at 3 to 9%.

FIG. 1 schematically shows the cross-sectional structure of a cylindrical body, as an example of the composite member of the present invention, in which a sintered alloy layer (20) having the above-mentioned composition is formed on the outer peripheral surface of a metal base material (10) having a cylindrical shape. It is shown in This composite body is used as a rolling roll, for example, by fitting arbors (30, 30) into its hollow holes. In the example shown, the sintered alloy layer (
20) is formed over the entire outer circumferential surface of the base material (10), but it does not necessarily have to be so, and it can be selectively provided only in the necessary parts according to the application and usage conditions. It goes without saying that the portion may have a partial composite structure in which the surface of the base material remains exposed.

The composite member of the present invention uses a metal powder having the above-mentioned composition as a sintered material, and forms a sintered alloy layer on the surface of a metal base material (cast material, etc.) by a hot isostatic pressure sintering method, The sintered alloy layer is then subjected to quenching and tempering treatments for refining the sintered alloy layer. That is, a filled layer of metal powder, which is a sintered material, is formed on the surface of a metal base material using an appropriate encapsulant, and the inside of the powder filled layer is degassed.
sealed and subjected to hot isostatic pressing sintering, preferably at 900
~1200℃X500~1500kg r/crA
A sintered alloy layer is formed under these conditions. The metal powder used preferably has a particle size of about 30 to 250 μm in order to make the structure of the sintered alloy layer formed homogeneous and fine. If the powder has a relatively large amount of oxide film, the oxide film may be reduced by introducing a reducing gas under heating before deaerating and sealing the powder-filled bed. After sintering is complete, machining is performed to remove the encapsulant and make any necessary shape modifications. In addition, the material of the metal base material is
It is arbitrarily selected depending on the intended use and usage conditions of the composite member. For example, in the case of a product that requires strength and toughness, such as a rolling roll, various types of high-strength steel, such as , it is sufficient to use SCM steel, SNCM steel, etc.

The quenching temperature in the quenching process of the sintered alloy layer is 1050
~1250℃1 Preferably, the temperature is 1100~1200℃, and cooling from that temperature is performed by gas cooling using substantially normal pressure gas as a refrigerant, or pressurized gas (e.g. The tempering treatment following the above-mentioned quenching treatment, which is preferably carried out by forced gas cooling using a refrigerant of 3 to 7 kgf/cffl), is carried out at 500 to 600°C1.
More preferably, this is suitably achieved by repeating the operation of heating and maintaining the temperature at 520 to 580°C and then gradually cooling it once or multiple times (for example, 2 to 4 times). By this tempering treatment, the sintered alloy layer undergoes phase transformation from austenite in its matrix to martensite or bainite, and secondary hardening due to precipitation of MC type and/or M, C type carbides. The particle size of the precipitated carbide is approximately 10μ
It is extremely fine, measuring less than 1.0 m (roughly several μm or less), and the amount of precipitation is about 25 to 35% in terms of area ratio, compared to the amount of carbide in general ingot material (usually about 10 to 15%). It is abundant and has uniform dispersibility.

The thickness of the sintered alloy layer is not particularly limited, but if it is used as a rolling roll or the like, if the layer is thinner than about 3 mm, the shear stress generated in the sintered alloy layer due to the rolling load during rolling will be reduced. Since peeling tends to occur in the sintered alloy layer due to the effect of The thicker the layer, the better the durability, but if it is too thick, the density of the sintered alloy layer will decrease and the tendency for cracks to occur due to thermal stress will increase, so the upper limit should be about 25 mm. is appropriate.

The composite member of the present invention has a high degree of durability due to the combination of the dense and fine structure of the sintered alloy layer formed by hot isostatic pressure sintering, the alloy composition, and the heat treatment effects of quenching and tempering. It has abrasion resistance, surface roughness resistance, and seizure resistance, and because it has a composite structure with metal parts, it has the mechanical properties such as strength and toughness that are necessary when using it as a body member of a rolling roll, for example. In addition, when combining it with other members such as an arbor, it can be assembled into a desired structural member by simple operations such as shrink fitting.

(Example) As shown in Figure 2, a cylindrical metal capsule material (C) is fitted onto a cylindrical metal base material (10) and welded together, and the inner side of the capsule member (C) is The space is filled with metal powder (P), which is a sintering material, and after being degassed at room temperature, it is sealed and subjected to hot isostatic pressure sintering.After sintering is completed, the capsule material (C
) is removed by machining, and rough machining is performed leaving an excess thickness of Inn.

Then, quenching and tempering treatments are performed to refine the sintered alloy layer. Through the above steps, the first layer has a concentric two-layer laminated structure consisting of an outer layer that is a sintered alloy layer and an inner layer that is a metal base material.
A cylindrical composite member as shown in the figure was obtained. Outer diameter: 36
4 cylinders, inner diameter: 220mm, length: 100mm, sintered alloy layer thickness near value.

(1) Metal base material: S CM 440114 (0.4%C-0,
35%S i -0,75%Mn-1%Cr -0,2
%Mo) (IF) Sintered material (metal powder) Gas atomized powder (50-150μm) Component composition (-
(%): C2,2,S i O,3,MnO,
3, Cr 4.4. V6.2. W 7.1.
Co 10.8°Mo 7.2. F e Baf
. Oxygen concentration 150 ppm.

(m) Sintering conditions: 1150°C x 1000kg f/CTAX 3 Hr
(IV) Heat treatment of sintered alloy layer (1) Quenching treatment After holding at 1200° C. for 1 hour in a vacuum quenching chamber, gas (room temperature and normal pressure Ar gas) is introduced to perform quenching by gas cooling.

(2) Tempering treatment A process of heating and holding at 540° C. for 5 hours and allowing to cool is repeated three times.

(V) Quality of the sintered alloy layer (a) Soundness inspection and ultrasonic flaw detection revealed that there were no defects either within the sintered alloy layer or at the interface with the metal base material, and the interface was found to be visible over the entire circumference and entire length. It was confirmed that the bond was completely fused.

(b) Microstructure Microscopic observation reveals that the roll has a dense structure in which homogeneous fine carbides (MC type, M, C type) are analyzed and dispersed, compared to cast iron rolls. Fig. 3 shows its microscopic structure (magnification: 4000). The carbide particle size is about 5 μm or less, and the area ratio is about 30%.

(c) Hardness The surface hardness of the sintered alloy layer of the obtained composite member is as high as 5 to 67 in the surface direction and in the depth direction, and the variation is small and homogeneous as less than ±LH++c.

(d) Seizure resistance test A mating material (SO5304) is pressed against the surface of a rotating test piece and the rotational torque is measured, and the presence or absence of abnormal fluctuations in torque determines the presence or absence of seizing between the sliding surfaces of the test piece and the mating material. A flex-type seizure test (pressing load: 1.50 kg) was conducted to determine the properties of the above sample material (test surface: sintered alloy layer), chilled cast iron, which is a typical example of conventional casting roll material, and conventional sintered alloy. Gold (C2, 8%.

Si0.4%, Mn0.4%, Ni1.2%, Cr2O
%, Mo1%, Fe Bad, and the sintering conditions were the same as above). In the test, both the chilled cast iron and the comparative sintered alloy experienced abnormal fluctuations in torque values shortly after the start of the test, and in particular, the comparative sintered alloy showed a sharp peak in torque value as the load increased. It was observed that in the sintered alloy layer of the invention example, the torque value was stable and there was no occurrence of seizure between the sliding surfaces with the mating material.

(e) Actual machine use test The aper was fitted into the hollow hole of the cylindrical composite member of this example by shrink fitting, and after performing the necessary finishing processing as a rolling roll, the actual machine was used as a roll for flat steel finishing rolling. As a result of use, the wear rate was less than a fraction of that of high-hardness ductile cast iron rolls, which are typical conventional casting rolls, and wear and surface roughness were extremely slight, and there was no seizure with rolled steel materials. Met.

〔Effect of the invention〕

The composite member of the present invention has excellent surface abrasion resistance, roughness resistance, and seizure resistance, and has the toughness necessary as a structural member, and can be easily assembled with other members. By using the composite member of the present invention in combination with an arbor or the like as a material for the body of a rolling roll, for example, a stable service life that exceeds that of conventional rolls can be obtained, and the surface condition of the body is stable. As a result, a great effect can be obtained in improving the quality of the rolled material. The composite member of the present invention is also useful as other structural members such as bearings and cylinders.

[Brief explanation of the drawing]

Fig. 1 is a radial half-cut cross-sectional view showing an example of the cross-sectional structure of the composite member of the present invention, and Fig. 2 is a radial half-cut cross-sectional view showing an example in which the outer peripheral surface of a metal base material is filled with sintered material (metal powder). Figures 3 and 3 are micrographs in place of drawings showing the metal structure of the sintered alloy layer. 10: Metal base material, 20: Sintered alloy layer, C: Capsule material. P: Sintered alloy powder.

Claims (1)

[Claims] 1. C: 2 to 3.5%, Si:
0.4% or less, Mn: 0.4% or less, Cr: 3 to 6%,
V: 6-12%, W: 5-14%, Co: 7-14%,
Mo: 3 to 9%, the balance substantially consisting of Fe, and a sintered alloy layer is formed on a martensite or bainite base with a metal structure in which MC type and/or M_6C type carbides with a grain size of 10 μm or less are dispersed and precipitated. A composite member characterized by: 2. C: 2-3.5%, Si: at key points on the surface of the metal base material
0.4% or less, Mn: 0.4% or less, Cr: 3 to 6%,
V: 6-12%, W: 5-14%, Co: 7-14%,
Mo: 3-9%, remainder substantially Fe Particle size: 30-9%
Using 250 μm metal powder as a sintering material, a sintered alloy layer is formed by hot isostatic pressing sintering method, and then 1050 μm ~
The method for manufacturing a composite member according to claim 1, characterized in that quenching from 1250°C and tempering treatment at 500 to 600°C are performed.