JPH01252703A - Roll for rolling shaped steel and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a roll for rolling having excellent wear resistance, seizure resistance, surface roughening resistance by forming sintered layer of high alloy steel having the specific composition on base material surface in each rolling roll having recessed part and projected part on surface for rolling shaped steel such as angle, etc. CONSTITUTION:At the time of manufacturing the recessed roll A having V-shaped groove (a) on the surface for using to rolling of the shaped steel such as the angle, etc., and the projected roll B having projection (b) corresponding to the V-shaped groove (a), each cylindrical metal capsule C1, C2 is fitted to low alloy steel-made cylindrical body 11, 12 at barrel part 10, 20 of each roll A, B. Fine powder P of the high alloy steel composing of 2-3.5wt.% C, <0.4wt.% Si, 3-6wt.% Cr, 6-12wt.% V, 5-14wt.% W, 7-14wt.% Co and 3-9wt.% Mo is packed into gap between the base material 11, 12 and the capsule C1, C2 and after sealing and degassing, it is sintered with not isostatic pressing method and after quenching from 1,050-1,250 deg.C, temper is executed at 500-600 deg.C. By the above method, the roll for rolling the shaped steel having 3-25mm thickness of the sintered layer and excellent wear resistance, seizure resistance and surface roughening resistance is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a long steel rolling roll and a manufacturing method thereof.

[Conventional technology]

BACKGROUND ART Cast iron materials such as chilled cast iron, ductile cast iron, and adamite cast iron have been widely used as body materials for rolls used for rolling long steel bars such as angles. In addition, with the aim of improving its wear resistance, by making cast iron highly alloyed,
Materials with increased hardness made by crystallizing cementite, double carbides, and other special carbides are also used. In addition, alloy powder (C: 1.3-3%,
It has also been proposed to use sintered crystals of Cr: 15-21%, W+2Mo: 8% or less) as a roll body member (Japanese Patent Laid-Open No. 58-213856).

[Problem to be solved by the invention]

The body of a cast iron roll has a coarse cast structure in which carbides crystallize in a net shape, so it does not have sufficient mechanical properties such as toughness. A long steel rolling roll with a complicated shape is likely to have cracks or the like on its body surface.

In particular, in angle rolling finishing rolls that are composed of a concave roll with a V-shaped groove on the body surface and a convex roll with a chevron-shaped protrusion, the bottom of the V-shaped groove of the concave roll and the peak of the convex roll are There is a strong tendency for heat cracks to occur at the ridges of mold protrusions. Furthermore, the wear resistance is not sufficient, and in the case of a convex roll, the ridges of the chevron-shaped protrusions tend to wear out easily. On the other hand,
The alloys and powder sintered materials have a dense and fine structure, and have excellent mechanical properties as well as wear resistance and roughness resistance that exceed those of cast iron rolls. There is a problem that seizure is likely to occur.

In particular, in recent years, in the field of long steel rolling, new rolling technologies have been developed in response to demands for product diversification and higher quality. ,
There is a growing demand for improved surface roughness resistance, heat crack resistance, etc., and it is becoming difficult to meet these demands with conventional rolls.

The present invention provides an improved long steel rolling roll and a manufacturing method thereof to solve the above problems.

[Means and effects for solving the problems] The long steel rolling roll of the present invention has a body portion coated with C: 2 to 3.5%, Si at key points on the surface of a metal base material having a required uneven surface. :0.
4% or less, Mn: 0.4% or less, Cr: 3-6%, V
: 6-12%, W: 5-14%, Conea-14%,
Mo: 3 to 9%, remainder substantially Fe layer thickness 3 to 2
It is characterized by being a composite body consisting of five sintered alloy layers.

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

C+2 to 3.5% C increases the hardness of the sintered alloy by forming a solid solution in the matrix and partially combining with V and W to form carbides. The reason why we set the lower limit for the amount of C to 2% is that if it is less than that, the balance of the amount of C necessary for the formation of carbides of V and W will be poor (
, the effect of high-alloying the sintered alloy cannot be sufficiently obtained, and on the other hand, if it exceeds 3.5%, the toughness decreases due to 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.

C: 3-6% Cr is an element that dissolves in the matrix of the sintered alloy to greatly improve hardenability and exhibits temper softening resistance.To obtain this effect, addition of 3% or more is required. However, increasing the amount of C 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%.

■: 6 to 12% ■ 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, but tempering treatment precipitates a sufficient amount of MC type carbide to achieve high hardness and high hardness. 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, vl was set to 6 to 12%.

W: 5 to 14% W is an important element along with V mentioned above. That is, W is a strong carbide-forming element, and is dissolved in the matrix, and upon tempering and treatment, finely precipitates as MC-type carbide, 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 defined as ~14%.

Conea ~ 14% Co promotes precipitation of carbides by tempering treatment and 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 pair of upper roll (A) and lower roll (B) constituting an angle rolling finishing roll as an example of the long steel rolling roll of the present invention. (1
0) (20) is the body of each roll (A) (B), (30
, 30) are arbor fitted and fixed to the bodies (10) and (20) of each roll. The upper roll (10) is a concave roll having a V-shaped groove (a) that goes around the circumference of the body, and the lower roll (B) has a V-shaped groove (a) that extends around the circumference of the body. It is a convex roll having a chevron-shaped protrusion (b) that goes around it, and each body (10) (20) is a metal cylindrical body (m) (
21) is used as a body base material, and has a composite structure in which sintered alloy layers (12) and (22) having the above specified composition are laminated on the surface thereof. The body base material (11) of the upper roll (A) has a V-shaped circumferential groove (ao), and the body base material (21) of the lower roll CB) has a chevron-shaped circumferential protrusion (bo). )
are formed in advance, and the sintered alloy layers (12) and (22) are formed with a substantially constant layer thickness along the uneven surfaces of the base materials (11) and (1, 2).

In Figure 1, the upper roll (A) has one figure-7 groove (a) in the body (10), and the lower roll (B) has a corresponding chevron-shaped projection (b). Although an example is shown, the upper roll (A) may have a plurality of 7-shaped grooves (a, a) if desired.
,...), and the lower roll (B) has a plurality of chevron-shaped protrusions (b, b,...) corresponding to the number and position of the plurality of 7-shaped grooves (a, a,...). ) will be provided.

In addition, in FIG. 1, the upper roll (A) and the lower roll (B
) shows an example in which the sintered alloy layer (12) (22) is formed over the entire surface of the body base material (11) (21). , Seizure resistance is a problem in the hole part that comes into direct contact with the rolled material,
In other words, since these are the surfaces of the 7-shaped groove (a) and the chevron-shaped projection (b), as shown in FIG. sintered alloy layer (
12) (22) is provided, and the other parts are the base material (11) (
It goes without saying that a partially composite structure in which the surface of 21) remains exposed may be used.

The layer thickness of the sintered alloy layer on the surface of the roll body is approximately 3111111.
It is preferable that it is above. This is because if the layer thickness is thinner than that, the sintered alloy layer is likely to peel off due to the action of shear stress generated within the sintered alloy layer due to the rolling load during rolling, resulting in a problem in durability. The thicker the layer thickness, 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. preferable.

The material of the body base material may be any material as long as it has the mechanical strength and toughness necessary for a rolling roll, and various strong steels such as SCM steel and SNCM steel may be used depending on the intended rolling conditions. You can use it selectively.

The body of the long steel rolling roll of the present invention is made of a hollow or solid metal body (casting product, etc.) with a circular cross section on the surface of which is formed a concavo-convex shape serving as a hole, and the body has the above-mentioned components on its surface. It is manufactured by forming a sintered alloy layer having a certain composition, and then performing quenching and tempering treatments to refine the sintered alloy layer.

The formation of the sintered alloy layer is preferably performed by hot isostatic pressing sintering. That is, a packed layer of metal powder, which is a sintered material, is formed on the surface of a metal base material using an appropriate encapsulant, the inside of the powder packed layer is deaerated, sealed, and hot isostatically pressed. Sintering, preferably 900-12
00°cx500~1500kgf/cr! A sintered alloy layer is formed under conditions of r. The particle size of the sintered material powder is approximately 3.5 mm, from the viewpoint of homogeneity and refinement of the metal structure of the obtained sintered alloy layer.
It is preferably 0 to 250 μm. If the metal powder has a relatively large amount of oxide film, the oxide film may be reduced and removed 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.

The quenching temperature in the quenching process of the sintered alloy layer is 1050
~1250°C1 Preferably 1100~1200'C, and cooling from that temperature is performed by gas cooling using approximately normal pressure gas as a refrigerant or pressurized gas ( For example, it is preferable to carry out forced gas cooling using 3 to 7 kg f/c++1) as a refrigerant.

The tempering treatment following the above quenching treatment has a temperature of 500 to 600
After heating and maintaining the temperature at 0°C 1 or more preferably 520 to 580'C, the operation of slowly cooling the temperature is carried out once or multiple times (e.g. 2 to 4
This is preferably achieved by repeating the process (times).

Through 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 carbides, M, and C type carbides. The grain size of the precipitated carbides is extremely fine, approximately 10 μm or less (roughly several μm or less), and the amount of precipitated carbide is approximately 25 to 25 μm in area ratio.
35%, and the amount of carbide in general melted wood (usually about 1
(0 to 15%) and has uniform dispersibility.

The body surface of the long steel rolling roll of the present invention has a high degree of wear resistance and roughening resistance due to the dense and fine structure of the sintered alloy layer, its alloy composition, and the heat treatment effects of quenching and tempering. Since it has a composite structure with a metal base material, it also has mechanical properties such as strength and toughness necessary for a rolling roll.

〔Example〕

As shown in FIG. 3 (1) (n), a cylindrical metal capsule material (C+) (
c, > are fitted and welded together, the space inside the capsule member is filled with metal powder (P), which is a sintered material, and after degassing at room temperature, it is sealed, and hot isostatic pressure is applied. Subject to pressure sintering.

After completion of sintering, each capsule material is removed by mechanical processing, and rough processing is performed, leaving the excess thickness of 1 (g). Then, quenching and tempering treatments are performed to refine the sintered alloy layer. Through the above steps, F sections (10) and (20) of an upper roll (A) and a lower roll (B) having the composite structure shown in FIG. 1 were manufactured as finishing rolls for angle rolling. Outer diameter:
400mm, inner diameter: 200 body, length: 270mm,
Sintered alloy layer thickness: 15m+a0 [1] Metal base material: SCM440 steel (0,4%C-0,35%5i-
0,75%Mn-1%Cr-0,2%Mo) (II)
Sintered material (metal powder) Gas atomized powder (particle size: 50-150 pm)
Component composition (wt%): C2,2, S i O,
3, MnO, 3, Cr 4.4. V6.2. W
7.1. Co 10.8°Mo 7.2. Fe
BaI! ,. Oxygen concentration 150 ppm.

(III) Sintering conditions 1150℃XX100O) c f /cfflX 3
Heat treatment of Hr(IV) sintered alloy layer (1) Quenching treatment After holding at 1200°C for 1 hour in a vacuum quenching chamber,
Introducing gas (Ar gas at normal temperature and pressure) and quenching by gas cooling.

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

(V) Quality of the sintered alloy layer (a) Soundness Check 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) Compared to microstructured cast iron rolls, homogeneous and fine carbides (MC type, M,
Type C) has a dense and dispersed structure. FIG. 5 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 Figure 4 shows the hardness distribution in the depth direction of the sintered alloy layer. The measurement position is the slope of the chevron-shaped protrusion (b) of the lower roll (convex roll). As shown in the figure, the hardness is high at HRC65-67.
The variation is small and homogeneous, ±IH*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 Farex type seizure test (pressing load: 150 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. (C2, 8%.

SiO, 4%, Mn 0.4%, Ni 1.2%, Cr2O
%, Mo1%, Fe Ban, and the sintering conditions were the same as above). In the test, both the chilled cast iron and the comparative sintered alloy showed abnormal fluctuations in torque values soon after the test started, and in particular, the comparative sintered alloy showed a sharp peak in torque value as the load increased. In the sintered alloy layer of the invention example, it was observed that 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 Arbors were fitted into the hollow holes of the roll bodies (10) and (20) by shrink fitting, and finishing processing necessary for the roll was performed, and the roll was used in the actual machine as an angle finish rolling roll. Compared to high-hardness ductile cast iron rolls, which are typical conventional casting rolls, wear and surface roughness were extremely slight, and there was no seizure with the rolled steel material.

[Effects of the Invention] The long steel rolling roll of the present invention has excellent abrasion resistance, roughening resistance, and seizure resistance on the body surface, as well as strength, toughness, etc., so it has a stable service life that exceeds that of conventional rolls. obtained, and the surface condition of the body is stable,
Great effects can also be obtained in improving the quality of rolled materials.

[Brief explanation of the drawing]

FIG. 1 is an axial half-cut sectional view showing an embodiment of the present invention, and FIG.
The figure is a cross-sectional view of the main part in the axial direction showing another embodiment of the present invention.
Figures (I) and (II) are partial axial cross-sectional views showing an example in which the outer peripheral surface of the roll body base material is filled with sintered alloy powder, Figure 4 is a graph showing the hardness of the sintered alloy layer, and Figure 5. is a photomicrograph substituted for a drawing showing the metal structure of a sintered alloy layer. 10.20: Roll body, 11, 21: Body base material, 12
゜22: Sintered alloy layer, C,, C2: Capsule material, P: Sintered alloy powder.

Claims (1)

[Claims] 1. A metal base material having a desired uneven surface, and formed on the surface of the metal base material, C: 2 to 3.5%, Si: 0.4% or less, Mn: 0 .4
% or less, Cr: 3-6%, V: 6-12%, W: 5-1
4%, Co: 7 to 14%, Mo: 3 to 9%, and a sintered alloy layer with a thickness of 3 to 25 mm, the remainder being substantially Fe. A roll for rolling long steel with excellent surface roughness resistance. 2.C:2 on the surface of the metal base material having the required uneven surface
~3.5%, Si: 0.4% or less, Mn: 0.4% or less, Cr: 3-6%, V: 6-12%, W: 5-14%,
Co: 7-14%, Mo: 3-9%, remainder substantially Fe
A sintered alloy layer is formed by hot isostatic pressing sintering using a metal powder of 1050 to 1250 as a sintering material.
The method for manufacturing a long steel rolling roll according to claim 1, characterized in that quenching at a temperature of 500°C and tempering treatment at 500 to 600°C are performed.