JP2002282909A - Abrasion-resistant centrifugal casting roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasion-resistant centrifugal casting roll for hot rolling which is excellent in abrasion resistance, cracking resistance and surface roughening resistance. SOLUTION: In the roll having an internal layer material of iron-base alloy and an external layer material formed by centrifugal casting, the metal base of the external layer material contains 50 to 80% tungsten carbide particles by volume ratio and 100 MPa or more compressive residual stress is given to the surface of the external layer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wear-resistant centrifugally cast roll or roller in which a wear-resistant outer layer material is welded to the outer periphery of a tough inner layer material.

[0002]

2. Description of the Related Art A hot-rolling roll or a roller for transporting a high-temperature steel material comes into contact with a material to be rolled, so that the surface thereof wears very quickly. In addition, these rolls or rollers (hereinafter, referred to as rolls) are required to have high toughness and strength because the material to be rolled needs to be rolled and transported with a high load. In response to the above requirements, a cemented carbide composite roll having an outer layer material formed by sintering a cemented carbide powder containing tungsten carbide, or an outer layer material containing cemented carbide particles such as tungsten carbide is cast. And a method of manufacturing the same.

[0003] For example, Japanese Patent Application Laid-Open No.
No. 0-5823 discloses that at least one or two or more hard particles of carbides, nitrides and carbonitrides of elements of the periodic table IVa to VIa are applied to the outer periphery of an inner layer material made of a steel material. There is disclosed a cemented carbide composite roll having a cemented carbide outer layer material obtained by sintering a metal powder containing 〜90% by weight.

Japanese Patent Application Laid-Open No. 61-27165 discloses that
A method for producing a composite casting excellent in wear resistance as a rolling roll is disclosed. The same publication discloses that fine tungsten carbide particles having a particle size of 15 μm or less are kneaded with a binder metal powder, pre-sintered, and granulated powder having a particle size of 44 μm or more is converted to an iron-based metal (such as ductile cast iron or glen cast iron). )), A method of producing a wear-resistant composite casting in which the granulated powder is broken in the molten metal, and the original fine tungsten carbide particles are dispersed in the molten metal by centrifugal casting. Furthermore, the same publication discloses that a cylindrical space extending in the longitudinal direction is provided in the mold, and while the mold is rotated in the horizontal direction, molten metal and granulated powder of tungsten carbide are added to the cylindrical space of the mold to form fine tungsten. It describes a method for producing a wear-resistant composite casting required for surface roughening resistance, such as a rolling roll in which carbides are dispersed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No. 23, the cemented carbide composite roll disclosed in
It has already been put into practical use as a roll with improved wear resistance. However, this type of cemented carbide roll needs to produce an outer layer material by hot isostatic pressing (HIP) or the like after forming cemented carbide powder containing tungsten carbide into a desired shape and temporarily sintering it. is there. Further, it is necessary to join a steel shaft to the inner space of the outer layer by shrink fitting. Such a composite roll made of cemented carbide can provide a roll that is extremely excellent in wear resistance and the like. However, since the manufacturing process of the cemented carbide composite roll is multi-step and complicated, the manufacturing cost is high, and sintering by the HIP method or the like is performed. There was a problem that it was difficult to lengthen.

Japanese Unexamined Patent Publication (Kokai) No. 61-27165 discloses a centrifugal casting method, that is, a method in which a molten metal mixed with tungsten carbide particles (a metal base is an iron-based metal) is injected while rotating a vertically disposed mold horizontally. Thus, a method of forming an outer layer having wear resistance is disclosed, but does not describe the material of the inner layer material or the compressive residual stress to be applied to the outer layer material. In a wear-resistant roll used in hot rolling, it is important that the outer layer material has abrasion resistance and that the occurrence of cracks during use is suppressed by increasing the compressive residual stress on the surface of the outer layer material. .

[0007] The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a metal matrix formed by centrifugal casting on the outer periphery of an inner layer material made of an iron-based alloy having high toughness. An object of the present invention is to provide a wear-resistant centrifugal casting roll for hot rolling that is excellent in wear resistance, crack resistance, and surface roughness resistance by welding a dense outer layer material.

[0008]

According to the present invention, there is provided a roll having an inner layer material made of an iron-based alloy and an outer layer material formed by centrifugal casting, wherein the outer layer material contains tungsten carbide particles in a metal matrix in a volume ratio. % Of the outer layer material, and a compressive residual stress of 100 MPa or more is applied to the surface of the outer layer material.

In the present invention, the tungsten carbide particles are characterized by using simple particles of tungsten carbide or granulated powder obtained by granulating tungsten carbide particles and making them spherical. Further, a material having a higher melting point than the metal matrix of the outer layer material is interposed in at least a part of the surface of the tungsten carbide particles or the granulated powder thereof.
Furthermore, the metal matrix of the outer layer material of the present invention is characterized in that it is made of a nickel-cobalt based alloy.

In the present invention, the reason why the volume ratio of the tungsten carbide particles contained in the outer layer material is limited to 50 to 80% is as follows. If it is less than 50%, the abrasion resistance of the outer layer material will be insufficient, and the surface roughening resistance will decrease. If it exceeds 80%, the fracture toughness will decrease. Therefore, in order to obtain a hot-rolling roll excellent in wear resistance, crack resistance and surface roughening resistance, the volume ratio of tungsten carbide particles contained in the outer layer material needs to be 50 to 80%.

The present invention also provides a method for injecting a melt of an inner layer material made of an iron-based alloy material such as ductile cast iron or cast steel into a hollow portion of an outer layer material manufactured by a centrifugal casting method to weld the outer layer material and the inner layer material. Thus, a compressive residual stress of 100 MPa or more is applied to the surface of the outer layer material. 100MP
The reason for giving a compressive residual stress of a or more is as follows. That is, if the pressure is less than 100 MPa, fine cracks generated during hot rolling are likely to progress, so that it is necessary that the outer layer material has a residual compressive stress of 100 MPa or more.

Further, in the present invention, it is preferable that the tungsten carbide particles dispersed in the metal matrix of the outer layer material in a concentrated state have a particle diameter of less than 200 μm. When the particle size of the tungsten carbide particles exceeds 200 μm, the spherical tungsten carbide particles are larger than the metal matrix structure, and the rough surface resistance is reduced. Desirably, the particle size of the tungsten carbide particles contained in the metal matrix of the outer layer material is preferably 50 to 150 μm.

It is preferable that the tungsten carbide particles have a spherical shape because the surface roughness of the material to be rolled is improved.

In addition, when centrifugally casting the outer layer material, when the granulated powder of tungsten carbide granulated and spheroidized in the molten metal of the metal matrix is added, the granulated powder of tungsten carbide is converted into the original fine powder. May decompose. Therefore, when granulating the tungsten carbide fine powder, the surface of the tungsten carbide fine powder is coated with a material higher than the melting temperature of the metal matrix, for example, a nickel-cobalt alloy by electroless plating or the like. It is preferable to use granulated powder obtained by granulating particles and further using cobalt as a binder.

Further, in the present invention, as the base metal of the outer layer material, any of a cobalt-based alloy, a nickel-based alloy, and a nickel-cobalt-based alloy may be employed. The reason is that these alloys have a lower specific gravity than the tungsten carbide particles, so that the tungsten carbide particles can be uniformly dispersed in a concentrated state in the metal matrix by centrifugal casting. In particular, a nickel-cobalt-based alloy is suitable as the metal matrix of the outer layer material. Nickel-cobalt-based alloys are most suitable as the metal matrix of the outer layer material because they have better wettability with tungsten carbide than Fe-based alloys. In addition, when an Fe-based alloy is used as the base metal of the outer layer material, metal carbides other than tungsten carbide (WC) are easily crystallized, which tends to cause a reduction in wear resistance and toughness.

In order to apply a compressive residual stress of 100 MPa or more to the surface of the outer layer material, the diameters of the inner layer material and the outer layer material are appropriately set, and the inner layer material is welded to the core of the outer layer material. Can be controlled.

[0017]

Embodiments of the present invention will be described below. The wear-resistant centrifugal casting roll of the present invention can be manufactured by the following procedure.

1) First, a molten metal composed of a nickel-cobalt-based alloy serving as a metal matrix of an outer layer material is prepared. As a molten metal composed of this nickel-cobalt-based alloy, C: 0.01%, Ni: 32.4%, Co: 66.3% by weight.
%, Cr: 0.66%, Fe: 0.36%, W: 0.2
A melt containing 4% was prepared.

2) The molten metal of the above 1) is transferred to a ladle to granulate tungsten carbide particles, and the average particle diameter thereof is 50 to 150.
About 1/5 to 2/5 of the weight of the molten metal is added with a granulated powder of μm and stirred. The temperature of the molten metal before adding the tungsten carbide particles is preferably 1550 to 1650 ° C. Further, in order to prevent the temperature of the molten metal from dropping abruptly when the tungsten carbide particles are added, it is preferable to previously heat the tungsten carbide particles to 500 to 600 ° C.

3) The molten metal to which the tungsten carbide particles are added according to the above item 2 is cast into a horizontal centrifugal casting apparatus 1 as shown in FIG. 1 at a casting temperature of 1650 ° C., and the horizontal centrifugal casting apparatus 1 is rotated about the horizontal axis AA. Rotation was performed and centrifugal casting was performed for a predetermined time. By this centrifugal casting method, the tungsten carbide particles having a specific gravity larger than that of the base metal of the molten metal are centrifuged to be in a state close to the outer peripheral wall of the mold of the horizontal centrifugal casting apparatus 1.

4) When the mold is cooled after centrifugal casting for a predetermined time, as shown in FIG. 1, the outer layer material 4 of the wear-resistant centrifugal casting roll of the present invention can be obtained. As shown in FIGS. 1 and 2A, the outer layer material 4 is an outer layer material portion 5 in which tungsten carbide particles are densely packed.
And a metal base portion 6 made of a nickel-cobalt-based alloy
And a separate layer. The metal base portion 6 made of the nickel-cobalt-based alloy has an outer layer material portion 5.
Since it is softer, it can be easily removed by honing or the like. Then, the metal base portion 6 is partially removed by the honing process to obtain an outer layer material 7 as shown in FIG. 2B.

5) Further, when a molten iron-based alloy serving as an inner layer material is injected into the hollow portion 8 of the outer layer material 7 shown in FIG.
As shown in FIG. 2C, a wear-resistant centrifugal casting roll in which an inner layer material 9 made of an iron-based alloy is welded to an outer layer material 7 can be manufactured. Then, the wear resistant centrifugal casting roll of the present invention can be completed by subjecting the inner layer material 9 serving as the roll shaft core to finishing processing and, if necessary, heat treatment. As the material of the inner layer material 9, for example, a metal having high toughness such as ductile cast iron, glen cast iron, cast steel, or the like is used.

In the above description of the method of manufacturing the wear-resistant centrifugal casting roll of the present invention, an example in which tungsten carbide particles are added to the molten metal of the outer layer material placed in the ladle has been described. After the tungsten carbide particles are supplied at a uniform height to the bottom of the mold, a method of injecting a molten metal serving as a metal matrix of the outer layer material into the mold while rotating the mold about the horizontal axis AA as a rotation axis. May be adopted. Also, an example in which the inner layer material is formed by casting a molten metal made of an iron-based alloy in the hollow portion of the outer layer material has been described, A method in which the inner layer material and the outer layer material are integrated by shrink fitting can also be adopted.

[0024]

The present invention described above has the following effects. 1) Compared with a sintered cemented carbide composite roll manufactured by using HIP or the like, the wear-resistant centrifugal casting roll of the present invention is:
Since it can be manufactured using a conventionally used centrifugal casting apparatus as it is and the manufacturing process is simple, it is possible to provide a wear-resistant hot rolling roll with reduced manufacturing costs. 2) Since the outer layer material can be manufactured by centrifugal casting, a roll having a longer body can be manufactured as compared with the sintered cemented carbide roll.

[Brief description of the drawings]

FIG. 1 is a view showing a method for producing a wear-resistant centrifugal casting roll of the present invention.

2A is a cross-sectional view showing a shape of a material of an outer layer material shown in FIG. 1, FIG. 2B is a cross-sectional view showing a state where a metal base portion shown in FIG. 2A is partially removed, c) is a cross-sectional view showing the shape of the wear-resistant centrifugal casting roll of the present invention.

[Explanation of symbols]

1: Horizontal centrifugal casting machine, 4: Outer layer material, 5: Outer layer portion, 6: Metal base portion, 7: Outer layer material, 8: Hollow portion, 9: Inner layer material

Claims (4)

[Claims] 1. A roll having an inner layer material made of an iron-based alloy and an outer layer material formed by centrifugal casting, wherein the outer layer material contains 50 to 80% by volume of tungsten carbide particles in a metal matrix, 100MP on the surface of the outer layer material
A wear-resistant centrifugal casting roll, characterized in that a compressive residual stress of at least a is applied. 2. The wear-resistant centrifugal casting roll according to claim 1, wherein the tungsten carbide particles are granulated powder obtained by granulating tungsten carbide particles to form a spheroid. 3. The wear resistance according to claim 1, wherein a material having a melting point higher than a metal matrix of the outer layer material is interposed on at least a part of the surface of the tungsten carbide particles. Centrifugal casting roll. 4. The wear-resistant centrifugal casting roll according to claim 1, wherein the metal matrix of the outer layer material is made of a nickel-cobalt base alloy.