JP2002301505A - Composite rolling roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roll with which the problem of controllability of a plate shape due to the high Young's modulus of the sintered hard alloy is resolved by imparting the optimal distribution of residual stress so as to prevent the breakage of the roll due to an accident or the like in rolling. SOLUTION: In a composite rolling roll in which the outer layer excellent in wear resistance is formed on the outer periphery of a shaft material made of a ferrous material excellent in toughness, a hole is provided in the center part of the shaft material in accordance with at least part of the barrel part of the roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll for rolling a steel material such as a thin strip, a plate, a wire, a bar, etc. The present invention relates to a composite roll for hard metal alloy rolling having an outer layer formed of a hard alloy.

[0002]

2. Description of the Related Art Tungsten carbide (WC) having excellent abrasion resistance, rough surface resistance, etc., in order to meet the demands for high quality rolled materials, such as improved dimensional accuracy, reduced surface defects, and improved surface glossiness. Cemented carbides are applied to rolls for rolling rods, bars and flat bars. As is well known, a WC-based cemented carbide is a sintered alloy in which WC is bonded with a metal element such as Co, Ni, and Fe, and often contains carbides such as Ti, Ta, and Nb in addition to WC.

For example, Japanese Patent Publication No. 58-39906 discloses that
A roll for rolling a wire composed of a WC-based cemented carbide of WC-Co-Ni-Cr is described. This wire rod roll is a small-sized sleeve roll obtained by sintering a cemented carbide alone, and is 0.1 / 100 to a steel roll shaft excellent in toughness.
The sleeve roll is fitted with a shrink fit of about 0, and the side surface of the sleeve roll is pressed and fixed with a fixing ring, spacer ring, or the like, and mechanically assembled.

Japanese Patent Application Laid-Open No. Hei 10-263628 discloses that
In order to obtain an intermediate Young's modulus between steel and cemented carbide, a composite roll in which the outer layer is a cemented carbide and the core material is a steel-based material is described. JP-A-8-71603 describes that excellent surface gloss can be obtained by using a WC cemented carbide in a cold rolled stainless steel strip.

[0005]

Problems to be Solved by the Invention Japanese Patent Publication No. 58-3990
In the case of a roll in which a cemented carbide sleeve is fitted to a roll shaft as in No. 6, a large number of members such as fixing rings and spacer rings are required, the assembly structure is complicated, and high assembly accuracy is required. Therefore, there is a problem that man-hours and costs related to assembly are required. Further, since the fixing is performed from the side, an accident such as the sleeve slipping in the rotation direction during rolling may occur. Furthermore, there is a problem that the portion occupied by the cemented carbide, that is, the portion that can be used for rolling is less than half of the roll body length, which is inefficient.

Further, when a stainless steel strip is cold-rolled as disclosed in JP-A-10-263628, the Young's modulus of the steel is about 2.1 × 10 ⁵ MPa, while the carbide Young's modulus is about 2.1 × 10 ⁵ MPa. The modulus is about 5.0 × 10 ⁵ MPa, about twice as high as steel. For this reason, the amount of deflection of the roll becomes extremely small,
There is a problem that it is difficult to control the shape in the width direction of a rolled material, particularly a thin strip or a sheet material, as compared with a steel roll. further,
In the case of a solid structure roll with an outer layer formed on the outer periphery of the shaft,
Although it is possible to apply compressive residual stress to the roll surface, there is a problem that it is difficult to appropriately control the internal residual stress distribution.

Accordingly, an object of the present invention is to provide an outer layer integrally with a shaft material so as not to cause a sliding accident during rolling, while taking advantage of abrasion resistance and surface glossiness, which are characteristics of cemented carbide. In order to prevent roll breakage caused by accidents during rolling, etc.
An object of the present invention is to provide a roll that can provide an optimum residual stress distribution. Another object of the present invention is to provide a roll capable of solving the problem of plate shape controllability caused by a high Young's modulus of a cemented carbide.

[0008]

SUMMARY OF THE INVENTION A rolling composite roll according to the present invention is a rolling composite roll comprising a shaft made of an iron-based material having excellent toughness and an outer layer having excellent wear resistance formed on the outer periphery of the shaft. A hole is provided in the center of the shaft member corresponding to at least a part of the shaft member.

In the present invention, the circumferential residual compressive stress at the center of the roll surface in the rotation axis direction is preferably 90 to 600 MPa at room temperature. Then, in order to obtain the compressive residual stress in the circumferential direction, in a section perpendicular to the rotation axis of the roll, a ratio d / a of the cross-sectional area d of the hole provided in the center of the shaft to the cross-sectional area S of the entire roll is given. S is 0.05
It is preferably about 0.35. Further, the present invention is desirably applied to a cemented carbide alloy whose outer layer is made of a cemented carbide, but can also be applied to a composite roll made of a sintered alloy such as powdered high-speed steel.

[0010]

In order to prevent the roll from being damaged due to an accident during rolling, there is a method of applying a compressive residual stress to the roll surface. By compressing the shaft material having a different coefficient of thermal expansion to the outer layer of the cemented carbide as in the present invention, a compressive residual stress can be applied to the outer layer surface. As a result, it is possible to suppress the progress of heat cracks generated at the time of rolling, as compared with a single roll made of cemented carbide, and to reduce the amount of roll modification. Also,
Even when a large crack of, for example, about 1 mm occurs during rolling, it is possible to prevent the crack from developing into the interior due to the residual compressive stress on the surface.

As described above, the cemented carbide composite roll in which the outer layer of the cemented carbide is metal-joined to the outer periphery of the shaft material has many advantages. Radial tensile residual stress occurs. For this reason, it is necessary to further increase the joining reliability between the shaft member and the outer layer of the cemented carbide to counter this. These compressions,
The distribution of the tensile residual stress changes depending on the cross-sectional shape of the roll.

Therefore, by providing a hole in the center of the shaft at a position corresponding to the roll body, that is, by reducing the ratio of the area occupied by the shaft, which is a material having relatively excellent toughness, This tensile residual stress in the radial direction can be reduced. Furthermore, by providing a hole in the center of the shaft, the radial stress at the center of the roll and the roll surface is reduced to zero, and the peak-shaped stress distribution has a maximum value of stress between the surface and the hole at the center. Further, the absolute value of the tensile residual stress in the circumferential direction can be suppressed to be smaller than that in the case of a solid having no holes.

[0013] The roll strength due to the residual stress distribution inside the roll is the stress due to the reaction force from the rolled material during rolling (rolling stress).
Affected by Therefore, it is desirable that the hole provided in the center portion of the shaft is formed in a rolled portion, preferably in a range of not less than 1/2 of the rolled portion.

[0014]

FIG. 1 is a schematic sectional view of a rolling composite roll according to an embodiment of the present invention. In FIG. 1, a composite roll 1 for rolling according to the present invention comprises a shaft 2 made of SNCM439 steel.
An outer layer 3 made of a cemented carbide is formed on the outer periphery of the shaft member 2, and a small-diameter hole 4 penetrates through the center of the shaft 2. In the body, R represents a rolled portion through which the rolled material passes, and L represents a non-rolled portion.

The cemented carbide forming the outer layer 3 is composed of WC powder having an average particle diameter of 6 μm, Co powder having an average particle diameter of 1 μm, and N powder having an average particle diameter of 1 μm.
i powder, 1 μm Cr powder were prepared, and WC85
%, 9.3% of Co, 4.7% of Ni, and 1% of Cr, were wet-mixed with a ball mill for 20 hours, and then dried and then mixed powder was sintered.

In the area where the hole 4 is provided in the center of the shaft 3, it is most convenient to manufacture the roll 1 over the entire length of the roll 1. . For this reason, after opening the hole 4, it is desirable to close the openings at both ends of the shaft member 3 with a plug or the like in order to prevent intrusion of water or the like. The plug is fixed by a known method such as screwing or welding. Further, a rust preventive may be simply applied to the inner surface of the hole 4.

FIG. 2 is a schematic sectional view of a composite roll for rolling according to another embodiment of the present invention. As shown in FIG. 2, the hole 4 may be opened from one end surface of the shaft member 2 and closed halfway. The hole 4 only needs to be opened at least in the central portion of the shaft member 3 at a portion corresponding to the rolling portion R in the body length portion of the roll 1. That is,
Since the purpose is to alleviate the internal stress of the roll, a load is applied to the roll material by both the residual stress inside the roll and the stress caused by rolling. You can do without it.

Here, the roll of the present invention having a hole (hole diameter of 25 mm) in the center of the shaft material and the comparative example roll having no hole were evaluated for rolls having an outer diameter of 110 mm of the body. When the thickness of the outer layer of both rolls is 10 mm and the distribution of the internal stress is calculated, the stress at the boundary between the outer layer material and the inner layer material is 90 MPa in the comparative example, whereas the stress in the present invention is 80 MPa.
MPa, and the effect of the present invention was confirmed.

As described above, by providing the hole at the center of the shaft member, the stress at the boundary between the shaft member and the outer layer, which is the weakest portion in terms of strength, is reduced, and a stronger (higher safety factor) roll is obtained. was gotten.

[0020]

According to the present invention, there is provided a cemented carbide composite roll which can enhance the reliability of joining between the shaft material and the outer layer of the cemented carbide, and can be applied to severe rolling applications. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a rolling composite roll according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a rolling composite roll according to another embodiment of the present invention.

[Explanation of symbols]

1 roll, 2 shafts, 3 outer layer, 4 holes, R
Rolling part, L non-rolling part

Claims (4)

[Claims] 1. A rolling composite roll having an outer layer excellent in abrasion resistance formed on an outer periphery of a shaft material made of an iron-based material excellent in toughness, wherein a central portion of the shaft material corresponding to at least a part of a roll body is provided. A composite roll for rolling, characterized by having holes. 2. The compressive residual stress in the circumferential direction at the center of the roll surface in the rotation axis direction is 90 to 600 M at room temperature.
The composite roll for rolling according to claim 1, wherein the pressure is Pa. 3. In a cross section perpendicular to the rotation axis of the roll,
The ratio d / S of the cross-sectional area d of the hole provided in the center part of the shaft to the cross-sectional area S of the entire roll is 0.05 to 0.35, for rolling according to claim 1 or 2. Composite roll. 4. The composite roll for rolling according to claim 1, wherein the outer layer is made of a cemented carbide.