JP2003275809A - Composite roll for rolling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite roll for rolling which is made of a sintered hard alloy having a high-strength boundary joined part. <P>SOLUTION: This roll is the composite roll for rolling in which an outer layer material consisting of WC-containing sintered hard alloy is metallically bonded substantially and directly to the outer periphery of an inner layer material consisting of an iron-containing alloy containing ≥0.5 wt.% C and, in a traverse test in conformity to JIS R1601, the traverse rupture strength of a traverse test piece including the boundary joined part between the outer peripheral material and the inner peripheral material is ≥600 MPa. Further, the inner layer material contains any one or more kinds of Cr, Ni, Mo, V, W, Ti and Nb of ≥1.5 wt.% in total. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling roll used for rolling a metal material such as a steel material such as a strip material, a plate material, a wire material and a bar material, and an inner layer material made of a material having excellent toughness. The present invention relates to a cemented carbide rolling roll having an outer layer material made of cemented carbide on the outer circumference of the inner layer material.

[0002]

2. Description of the Related Art In order to meet the demand for higher quality of rolled materials such as improved dimensional accuracy, and improved productivity by reducing the number of man-hours required to change rolls, tungsten carbide (WC) -based alloys excellent in wear resistance and surface roughness are used. Hard alloys are applied to rolling rolls such as wire rods, steel bars, flat steels, and strip steels. As is well known, the WC-based cemented carbide is a sintered alloy in which WC is bonded with a metal element such as Co, Ni or Cr.

Since a cemented carbide is used as a rolling roll, a composite roll which is metal-bonded to an inner layer material having excellent toughness has been developed. For example, Japanese Patent Application Laid-Open No. 2001-47111 discloses a composite roll having an intermediate layer between an outer layer material and an inner layer material made of cemented carbide and a metal layer interposed between the inner layer material and the intermediate layer. It is disclosed.

[0004]

The above-mentioned conventional composite roll has excellent performance, but since the outer layer material made of cemented carbide and the inner layer material such as steel are joined together, a graded layer or metal is formed between them. It is necessary to interpose an intermediate layer. This is because when the outer layer material made of cemented carbide and the inner layer material made of iron-based material are directly metal-bonded, carbon diffuses from the outer layer material with high carbon activity to the inner layer material, and the carbon in the outer layer material near the boundary joint decreases. Therefore, carbon is reduced from the stoichiometric composition in the WC—Co 2 layer region, the η phase is generated, and the material becomes brittle. Even if the intermediate layer is provided, if the thickness is not sufficient, carbon diffuses and migrates over the intermediate layer during sinter joining, so that the η phase appears at the boundary joining part of the outer layer material. By providing the intermediate layer having a certain thickness or more as described above, the boundary bonding portion of the rolling roll can obtain sufficient strength, but a step of forming the intermediate layer is required in manufacturing.

It is widely known to use a hot isostatic pressing (HIP) method when manufacturing a powder alloy type composite roll such as cemented carbide. When a powder alloy is sintered and manufactured by a hot isostatic press, the alloy powder as a raw material is filled in a container called a steel HIP can and sealed by welding, and then the inside of the HIP can is deaerated. HIP processing is generally performed. When manufacturing a composite roll using this method, a hollow cylindrical sleeve or a solid shaft material to be an inner layer material is previously installed in a HIP can, and an outer layer material is placed in a space between the inner layer material and the HIP can. HIP
After the can is welded and hermetically sealed, HIP treatment is performed to sinter the outer layer material and at the same time join the inner layer material to manufacture the can.

However, when an intermediate layer is required between the outer layer material and the inner layer material, it is necessary to fill the HIP can with two types of powders, the outer layer material powder and the intermediate layer powder, in two layers. . With such a filling method, it is very difficult to stabilize the powder composition and thickness uniformly in the roll axial direction. In JP-A-2001-47111, in that example, a partition material is provided between the portion where the outer layer material is formed and the portion where the intermediate layer is formed, when filling the HIP can, and the powder for the outer layer material is provided. A technique for filling the powder for the intermediate layer is disclosed. However, even with such a method, it is difficult and time-consuming to completely prevent the two kinds of powders from being mixed.

An object of the present invention is to provide a composite roll for rolling which does not require an intermediate layer which is difficult to construct in manufacturing a composite roll for cemented carbide rolling and which can obtain a boundary joint portion having sufficiently high strength. It is to be.

[0008]

In the composite roll for rolling of the present invention, an outer layer material made of WC type cemented carbide is substantially provided on the outer periphery of an inner layer material made of an iron type alloy containing C: 0.5% by weight or more. A composite roll for direct metallurgical joining, comprising:
In a bending test according to IS R1601, a bending strength of a bending test piece including a boundary joint between an outer layer material and an inner layer material is 600 MPa or more. The term “substantially directly metal-bonding” as used in the present invention means that the outer-layer material and the inner-layer material are metal-bonded without an intermediate layer being interposed between the outer-layer material and the inner-layer material.

The second rolling composite roll of the present invention is
C: An outer layer material made of WC-based cemented carbide has a thickness of 1 mm on the outer circumference of the inner layer material made of an iron-based alloy containing 0.5% by weight or more.
A rolling composite roll, which is metal-bonded by interposing the following intermediate layer between an outer layer material and an inner layer material, and comprising JIS R16
In the bending test based on 01, the bending strength of the bending test piece including the boundary joint portion between the outer layer material and the inner layer material is 600 MPa.
The above is characterized. In addition, in these inventions, Cr, Ni, Mo, V, W and T are added to the inner layer material.
It is characterized by containing at least 1.5% by weight of one or more of i and Nb in total.

[0010]

When the outer layer material of the cemented carbide and the inner layer material of the iron-based alloy such as steel are joined, the carbon diffuses and moves at the joining interface during the sinter joining due to the difference in the carbon activities of the two. When the carbon activity of the cemented carbide is higher, carbon diffuses from the cemented carbide near the bonding interface to the inner layer material side, so that the carbon in the cemented carbide decreases. As a result, the η phase, which is a carbide having a low carbon composition, appears in this portion. Therefore, if the carbon activity of the steel is equal to or higher than that of the cemented carbide, the diffusion of carbon from the cemented carbide is eliminated and the generation of the η phase can be prevented.

The inventor conducted a joining experiment between cemented carbide and various iron-based alloys, and if the carbon content of the iron-based alloy exceeds 0.5% by weight, there is almost no diffusion of carbon from the cemented carbide, It was confirmed that the generation of the η phase can be prevented and a composite roll having sufficient bonding strength can be obtained. That is, when the carbon content of the iron-based alloy is 0.5% by weight or more, the carbon activity of the iron-based alloy becomes equal to or higher than that of the cemented carbide, and the carbon diffusion does not occur even when joining by HIP. Almost no η phase can be prevented from occurring. Therefore, if such an inner layer material is used, it is possible to obtain a sound joining interface without η phase without the construction of the intermediate layer. Also, by applying a brush or a spray coating, which makes it easy to apply the intermediate layer, it is possible to obtain a sound bonding interface without η phase even if the intermediate layer having a thickness of 1 mm or less is formed.

By such means, it is possible to obtain a rolling roll having a sufficient bonding strength between the outer layer material and the inner layer material.
The joining strength in the present invention is determined by cutting a bending test piece including a boundary joining portion between an outer layer material and an inner layer material from a roll, and measuring the JIS
It is evaluated by the bending strength measured by the bending test according to R1601. Generally, it is evaluated by a measuring method according to JIS R1601. The composite roll of the present invention preferably has a bending strength of 600 MPa or more as measured by this evaluation method.

Further, the iron-based alloy used as the inner layer material contains Cr,
It is preferable to contain at least 1.5% by weight in total of one or more of Ni, Mo, V, W, Ti and Nb. The inner layer material of such a composite roll is required to have transformation expansion characteristics for relaxing the strain generated by the large heat shrinkage of the inner layer material, as compared with the cemented carbide outer layer material having a smaller heat shrinkage. When this transformation is pearlite transformation, due to relaxation due to plastic deformation at high temperature after transformation, due to thermal shrinkage difference in the cooling process to normal temperature,
Large distortion occurs and causes roll breakage. For this reason, such transformation must occur at a certain low temperature, such as bainite transformation or martensite transformation. Therefore, in order to cause bainite transformation or martensite transformation in the cooling process after sintering, the inner layer material contains one or more of Cr, Ni, Mo, V, W, Ti and Nb in a total amount of 1.5% by weight. It is necessary to include the above.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a schematic sectional view for explaining a HIP method used for producing a composite roll for rolling. 1, inner diameter φ350 mm, length 90
In the center of the 0 mm HIP can 2, a hollow cylindrical inner layer material 1 made of an iron-based alloy having the composition shown in Table 1 of the present invention is arranged, and between the outer surface of the inner layer material 1 and the inner surface of the HIP can 2. Cemented carbide powder 3 was filled in the voids formed in 1. The composition of the cemented carbide powder 3 is WC 80% and Co 20% by weight. In this example, the intermediate layer was not constructed. In FIG. 1, the right half part is omitted because it is symmetrical.

[0015] Table 1 Iron-based alloy for inner layer material (% by weight)               C      Si      Mn    Ni    Cr      Mo      V Invention Example 1 0.62 0.22 0.65 1.70 0.73 0.20 0.1 5 Invention Example 2 0.58 0.31 0.68 1.17 0.75 0.20 0.1 Four Comparative Example 11 0.37 0.20 0.63 1.68 0.81 0.20 0.1 5 Comparative Example 12 0.46 0.22 0.40 0.13 0.85 0.12 0.0 Three

The HIP can 2 is hermetically sealed by welding, degassed by a vacuum pump, and then heated at 1300 ° C. and 1000 by a HIP device.
HIP treatment was performed at atmospheric pressure. After cooling, the HIP can 2 was removed by machining. The composite roll of the present invention having the outer layer material of the cemented carbide obtained by this, color check, it is confirmed that there is no cracks on the end face of the roll, by the ultrasonic flaw detector, the outer layer material and the inner layer material sound It was confirmed that they were joined. In addition, a bending test piece including the boundary joint between the outer layer material and the inner layer material was cut out from the center of the roll, and the JIS
The bending strength was measured by a bending test according to R1601, and the bending strength was 1100 MPa. In addition, it was confirmed by structure observation that there was no η phase near the boundary joint. In addition, not only the hollow cylindrical shape but also a solid shaft material can be used as the inner layer material.

(Embodiment 2) FIG. 2 is a schematic sectional view for explaining a HIP method used for manufacturing a composite roll for rolling. In Fig. 2, inner diameter φ350mm, length 900mm
In the center of the HIP can 2, a hollow cylindrical inner layer material 1 made of an iron-based alloy having the composition shown in Table 1 of the present invention was placed. Then, in order to form the intermediate layer 4, the weight ratio WC50
%, Co 50% mixed powder made into a slurry,
A brush was applied to the outer surface of the inner layer material 1 so as to have a thickness of 0.2 to 0.5 mm. Then, the outer surface of the inner layer material 1 and the HIP can 2
The cemented carbide powder 3 was filled in the void formed between the inner surface of the and. The composition of the cemented carbide powder 3 is WC80 in weight ratio.
% And Co 20%. In FIG. 2, the right half portion is omitted because it is not a target.

The HIP can 2 is welded and hermetically sealed, degassed by a vacuum pump, and then heated at 1300 ° C. and 1000 by a HIP device.
HIP treatment was performed at atmospheric pressure. After cooling, the HIP can 2 was removed by machining. The composite roll of the present invention having the outer layer material of the cemented carbide obtained in this manner, when inspected by color check and ultrasonic flaw detection, the outer layer material and the inner layer material are soundly joined with the intermediate layer sandwiched therebetween. It was confirmed.
Further, a bending test piece including a boundary joint portion between the outer layer material and the inner layer material was cut out from the center part of the roll, and the bending strength was measured by a bending test according to JIS R1601, and the bending strength was 1100 MPa. there were. In addition, it was confirmed by structure observation that there was no η phase near the boundary joint.

(Comparative Example 1) A composite roll having an outer layer material of cemented carbide was produced in the same manner as in Example 1 except that the hollow cylindrical inner layer material having the composition shown in Comparative Example 11 in Table 1 was used. did. As a result, it was confirmed by color check that there was no crack on the end face of the roll, and it was confirmed by an ultrasonic flaw detector that the outer layer material and the inner layer material were properly joined. However, a bending test piece including a boundary joint portion between the outer layer material and the inner layer material was cut out from the center of the roll, and the bending strength was measured by a bending test according to JIS R1601. As a result, the bending strength was 450 MPa. It was When the structure was observed by Murakami reagent etching, it was found that the η phase was present in the outer layer material in the vicinity of the boundary joint, and this was the cause of the bending strength deterioration.

(Comparative Example 2) A composite roll having an outer layer material of cemented carbide was produced in the same manner as in Example 1 except that the hollow cylindrical inner layer material having the composition shown in Comparative Example 12 in Table 1 was used. did. When the HIP can was processed and removed, and a color check was performed on the end surface of the roll, a circumferential crack was found at the joint between the outer layer material and the inner layer material. In addition, an inspection by ultrasonic flaw detection confirmed that cracks had developed on the entire surface of the roll.

[0021]

EFFECTS OF THE INVENTION According to the present invention, a composite for rolling made of cemented carbide having a highly reliable boundary joint without the need for a conventional intermediate layer construction and having a weak η phase at the boundary joint. You can get a roll.

[Brief description of drawings]

FIG. 1 HIP used to manufacture a composite roll for rolling
The schematic sectional drawing explaining a method is shown.

FIG. 2 HIP used to manufacture a composite roll for rolling
The schematic sectional drawing explaining a method is shown.

[Explanation of symbols]

1 inner layer material, 2 HIP can, 3 cemented carbide powder,
4 Middle class

Claims (3)

[Claims] 1. A rolling composite roll in which an outer layer material made of a WC-based cemented carbide is substantially directly metal-bonded to the outer periphery of an inner layer material made of an iron-based alloy containing C: 0.5% by weight or more. Then, in a bending test according to JIS R1601, a bending strength of a bending test piece including a boundary joint portion between an outer layer material and an inner layer material is 600 MPa or more, a rolling composite roll. 2. An outer layer material made of a WC-based cemented carbide and an intermediate layer having a thickness of 1 mm or less on the outer periphery of an inner layer material made of an iron-based alloy containing C: 0.5% by weight or more and an outer layer material and an inner layer material. A composite roll for rolling which is metal-bonded by being interposed between
In a bending test according to JIS R1601, a bending strength of a bending test piece including a boundary joint between an outer layer material and an inner layer material is 600 MPa or more, a rolling composite roll. 3. The inner layer material comprises Cr, Ni, Mo, V,
The composite roll for rolling according to claim 1 or 2, which contains 1.5% by weight or more in total of one or more of W, Ti, and Nb.