JPH04100614A - Composite roll - Google Patents

Abstract

PURPOSE:To improve the breakage resistance of a roll by arranging a cylindrical outer layer member of high alloy cast iron excellent in wear resistance on the outer peripheral surface of a steel shaft member and performing solid phase diffusion joining of both members. CONSTITUTION:The cylindrical outer layer member 1 is formed by high alloy cast iron excellent in wear resistance. This outer layer member 1 is arranged on the outer peripheral surface of a shaft member 2 formed by steel excellent in toughness. Both members 1, 2 are put by not isostatic pressure in solid phase diffusion joining. The outer layer member is formed by high chrome cast iron, graphite crystallized high chrome cast iron, adamite material or grain material. In this way, the outer layer member of expensive high alloy material can be utilized effectively.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a composite roll for hot rolling of steel materials.

(Prior art) In order to ensure the wear resistance of the rolling layer and the toughness of the shaft, rolling rolls are usually made of a strong cast iron material such as high-grade cast iron or spheroidal graphite cast iron. An outer layer made of high-alloy cast iron material with excellent wear resistance is welded to the surface to create a composite. In this case, a cylindrical shaft is generally used as the shaft, but a cylindrical shaft may be used for rolling shaped steel.

A composite roll for rolling is manufactured by casting an outer layer by centrifugal force casting, casting a shaft portion with its inner surface in a semi-solidified state, and welding and integrating the two.

(Problems to be Solved by the Invention) However, since the shaft portion has conventionally been formed of cast iron, it is difficult to obtain sufficient strength as the tensile strength is less than about 50 kg/mm2, and it is difficult to obtain sufficient strength when welding the outer layer. Alloy components mix into the molten metal of the shaft and deteriorate the material. For this reason, there have been problems such as the shaft portion breaking due to residual stress in the outer layer during manufacturing, and breakage accidents occurring during rolling due to recent harsher rolling conditions.

In order to solve this problem, it would be possible to form the shaft part from graphite steel or cast steel, but these steel materials have a higher solidification temperature than the outer layer material, and when welding the outer layer and the shaft part, Since the solidification of the inner surface of the outer layer lags behind the solidification of the shaft portion, it is difficult to obtain sound welding, and there is a problem that the strength at the welded portion is insufficient.

The present invention was made in view of this problem, and an object of the present invention is to provide a composite roll whose shaft portion is made of steel without impairing the integrity of welding between the outer layer and the shaft portion.

(Means for Solving the Problems) In order to achieve the above object, the composite roll of the present invention has a cylindrical outer layer member cast from a high-alloy cast iron material with excellent wear resistance, and a cylindrical outer layer member made of a steel material with excellent toughness. The structure of the invention is that the shaft member is disposed on the outer peripheral surface of the formed shaft member, and both members are solid phase diffusion bonded by hot isostatic pressing, and the outer layer member is made of high chromium cast iron, high chromium cast iron, Graphite crystallized high chromium cast iron, adamite material or grain material can be used.

(Function) Since the outer layer member and the shaft member can each be manufactured independently, manufacturing is easy. In addition, since the outer layer member and the shaft member are solid phase diffusion bonded by hot isostatic pressing (hereinafter referred to as HIP), the inner surface of the outer layer member does not melt during bonding, and the solidification time is delayed. There will be no bonding defects caused by this. In addition, the thickness of the diffusion layer at the junction is within 5 mm, even for C, a light element that is easily diffused.
It is extremely thin compared to a mixed layer (a layer having an intermediate component in which the components of the outer layer and the shaft portion are mixed) produced in the case of welding, and the outer layer member can be effectively used up to the vicinity of the boundary.

(Example) FIG. 1 shows the structure of a composite roll of the present invention, in which an outer layer member 1 forming a rolling layer is arranged on the outer peripheral surface of a shaft member 2 and solid phase diffusion bonded by HIP.

The outer layer member 1 is a cylindrical body, and is cast by centrifugal force casting (horizontal type, inclined type, vertical type) or static casting.

Since it is made of a single material, there is no risk of cracking due to excessive residual stress as long as you pay attention to the cooling rate after casting. As the material of the outer layer member 1, various high alloy roll materials for hot rolling, such as high chromium cast iron material, graphite crystallized high chromium cast iron material, adamite material, grain material, ductile material, etc., are used. Examples of suitable compositions are shown in Table 1 below.

In addition to the alloy components shown in the same table, the following may be included in place of a part of Fe as an element for improving the material quality. N is effective in degassing, and by containing 0.1% or less, it is possible to effectively eliminate casting defects during casting of the outer layer member. Further, although Nb is effective in refining the casting structure and also contributes to precipitation hardening, it is easy to cause segregation, so the content is preferably kept at 1.0% or less. (2) also has the same material quality improvement effect as Nb, but it tends to cause segregation and deteriorates toughness, so it should be kept at 1.0% or less. Note that the impurities P and S both make the material brittle, so it is desirable to keep them in small amounts, and it is best to limit both to 0.1% or less).

The shaft member 2 is a cylindrical body, and is manufactured by static casting or G-forging after casting. In addition, if the shaft member is cylindrical, centrifugal force casting can also be applied.

As the material, steel materials such as low alloy cast steel, high alloy cast steel, SCM material specified by JIS, and SNCM material can be used. As a result, the tensile strength of the shaft member can be increased to 60 kg/m'' or more, and sufficient strength and toughness can be ensured.

In order to solid phase diffusion bond the outer layer member l and the shaft member 2,
This is carried out by fitting the outer layer member 1 to the shaft member 2, removing air present in the gap between the fitting parts 1 and 2, and performing HIP processing. To remove the air in the fitting part gap, as shown in FIG.
This is done by providing a cover 5 made of a mild steel plate so as to cover the other metal part 4, and evacuating the air inside the cover 5.

6 is a degassing pipe, which is closed by caulking or welding after vacuum degassing. Alternatively, as shown in FIG. 3, both fitting ends may be welded and air may be evacuated through a degassing pipe 6 attached so as to communicate with the fitting gap. Note that by dividing the metal parts 3 and 4 and subjecting them to HIP processing, the HIP processing furnace can be downsized and equipment costs can be reduced. Since the shaft member 2 is made of steel, the divided metal parts can be easily joined and integrated by welding after HIP treatment. FIG. 4 shows a case of a sleeve roll for H-beam steel in which the shaft member is a cylindrical body, and the cover 5 is formed so as to enclose a composite roll material in which the outer layer member 1 is fitted to the shaft member 2.

Next, specific examples are listed.

(1) As an outer layer member, outer diameter is 340cm, inner diameter is 290.0~
A cylindrical body with a length of 290.2 m and a length of 1250 em was manufactured by centrifugal casting, and the outer diameter was 289.8 to 290. Ot
rm and a shaft member with a length of 1450 mm, and after deaerating the gap between the fitting parts, HIP treatment was performed. The HIP processing conditions were a pressure of 200 kg/all and a temperature of 1080°C.

Chemical composition of outer layer member and shaft member (wt%, remaining substantial Fe)
are shown in Tables 2 and 3 below.

Next Leaf second surface outer layer reduction (2) After HIP treatment, it was heated to the austenitizing temperature shown in Table 4 below, rapidly cooled, tempered at the temperature shown below, and subjected to strain relief heat treatment.

Table 4 Table 3 Yurinshujojiha (3) After heat treatment, surface hardness, boundary 45° compressive strength (compressive strength measured with a test piece with the joint boundary surface placed at 45° with respect to the loading direction) ) etc. were measured. The results are shown in Table 5 below.

Table 5 (4) From Table 5, the composite roll of the present invention has a shaft member of 60 mm.
It has a high strength of more than kg/mm2, and the boundary 45° compressive strength is approximately 200 kg/mm or more, and a large compressive stress remains on the surface of the outer layer, which affects the integrity of the joint boundary.
It was confirmed that it has excellent breakage resistance.

(Effects of the Invention) As explained above, in the composite roll of the present invention, the outer layer member, which is the rolling layer, is solid phase diffusion bonded by HIP to the outer peripheral surface of the shaft member made of steel material with excellent toughness. When joining both parts, the inner surface of the outer layer does not melt, so the joint is sound and does not deteriorate in strength, and the material properties of the shaft member can be utilized as is, ensuring high strength and breakage resistance. It is possible to improve sexual performance. Also,
Since the diffusion layers of both members are extremely thin, about 5 mm or less, it is possible to effectively utilize the outer layer member made of an expensive high-alloy material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the composite roll of the present invention, and FIGS. 2 to 4 are cross-sectional views showing the steps for degassing the joints of the composite roll material. Figure 4

Claims (2)

[Claims] (1) A cylindrical outer layer member cast from a high-alloy cast iron material with excellent wear resistance is placed on the outer peripheral surface of a shaft member made from a steel material with excellent toughness, and both members are subjected to hot isostatic pressing. A composite roll characterized by solid-phase diffusion bonding using pressure. (2) A claim in which the outer layer member is made of high chromium cast iron, graphite crystallized high chromium cast iron, adamite material or grain material (
The composite roll described in 1).