JPH0220686B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a composite ring for rolling a plate-shaped rolled material such as flat steel, and a method for manufacturing the same. (Prior art) In steel rolling rolls, the outer layer (rolling layer) that contacts and processes the rolled material is required to have wear resistance, while the shaft core, bearings, and wobbler parts must have toughness. Due to the requirements, a composite roll is used in which an outer layer and a shaft core made of a tough material are integrally welded together.
This composite roll is mainly integrated into a composite roll at the casting stage using a centrifugal casting method. On the other hand, in the finishing row of wire rod rolling, cemented carbide rings are almost always used these days. For example, in block mills, as shown in Figure 7, rings are formed of WC-based cemented carbide material that is sintered with WC and Co. carbide ring
21 are used. In addition to being used alone as described above, the ring 21 is often fixed to a shaft by mechanical means such as shrink fitting and used as an assembly roll. (Problems to be Solved by the Invention) When a carbide ring is shaft-fitted and used as an assembly roll, the entire ring is made of carbide, which is not only uneconomical but also requires a complicated assembly structure as shown in Figure 8. There is a need to. That is, when assembling and fixing the carbide ring 21' to the shaft, it is necessary to firmly fix it to the shaft using the fixing ring 22, spacer ring 23, etc., and also to prevent thermal expansion of the steel shaft and the carbide ring material. This is because it is necessary to alleviate large differences in coefficients. As a result, such assembled rolls are very costly. On the other hand, the above-mentioned cemented carbide exhibits excellent wear resistance when the rolling speed is very high;
When the rolling speed is low, such as 3 m/sec or less, there is a problem with crack resistance, and WC-based cemented carbide has few advantages in use despite its high cost. Furthermore, conventionally, there is a method of imparting wear resistance only to the portion of the roll that comes into contact with the rolled material. In other words, there are methods of overlaying the roll surface with wear-resistant materials by welding or thermal spraying, and methods of hardening through surface treatments such as surface hardening, but these methods may cause the overlay part to peel off due to rolling pressure or make the hardened layer thicker. It was difficult and short-lived. Furthermore, since it is necessary to select a material with good weldability, there is a problem in the application of materials with excellent wear resistance such as high carbon materials and high alloy materials. The present invention has been made in view of the above problems, and the present invention provides a composite ring that is low cost, easy to fit, has a long rolling life, and has excellent crack resistance even during low speed rolling, and its manufacture. The purpose is to provide a method. (Means for Solving the Problems) The composite ring of the present invention for achieving the above object is characterized by being formed by sintering high alloy powder with excellent wear resistance and crack resistance. It consists of an outer layer, which is a rolled layer, and an inner layer made of a steel material with excellent toughness.The outer layer is formed over the entire width of the outer surface of the inner layer, and the outer layer and the inner layer are diffusion bonded by hot isostatic pressing. It is at the point where it becomes. Furthermore, in the manufacturing method of the present invention, a high alloy powder with excellent wear resistance and crack resistance is applied over the entire outer surface width of the inner ring made of a steel material with excellent toughness by hot isostatic pressing. The method is characterized in that the powder is sintered to form an outer layer, which is a rolling layer, and the outer layer and the inner ring are diffusion bonded. (Example) Next, the composite ring of the present invention will be described together with its manufacturing method with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a composite ring 1 of the present invention. The outer layer 2 and the inner layer 3 are diffusion bonded by hot isostatic pressing (hereinafter referred to as HIP), and the inner layer 3 is made of a steel material with excellent properties. An outer layer 2 is formed thereon. The outer layer 2 is a rolling layer that comes into contact with the rolled material and roll-forms it, and the high alloy material forming this outer layer 2 is made of high alloy steel such as the high speed steel material listed in Table 1, or high alloy steel such as the high speed steel material listed in Table 2. Examples include high-alloy cast iron and Ni-Cr-based self-fluxing alloys shown in Table 3.

【table】

【table】

[Table] Note, unit weight%
On the other hand, the steel material forming the inner layer 3 of the composite ring is
An appropriate material can be selected from materials with excellent toughness such as carbon steel for machine structures and alloy steel for structures. This composite ring 1 is made by sintering the powder of the high alloy material (100 mesh or less) by HIP treatment over the entire width of the outer surface of an inner ring formed in a cylindrical shape to form an outer layer which is a layer used for rolling. is integrally formed by diffusion bonding to the outer surface of the inner ring. That is, as shown in FIG. 2, the radially outer side of the inner ring 3' is covered with a can plate 4, the space formed between the can plate 4 and the outer circumferential surface of the inner layer is filled with the metal powder, and then the degassing holes are filled. After exhausting the remaining gas in the space and sealing it from 5, it is subjected to HIP treatment to sinter the outer layer and diffusion bond the outer layer to the inner ring 3'. After the HIP treatment, the can plate 4 is removed and processed into a predetermined shape to obtain the composite ring 1. HIP processing is suitable because the high alloy components of the outer layer 2 do not mix into the inner layer 3 and deteriorate the toughness of the inner layer 3, and the outer layer 2 can be sintered at the same time, which improves productivity. Also excellent. By the way, the metal powder for forming the outer layer 2 by sintering is not limited to one type of high alloy powder, but it is also possible to use a high alloy powder mixed with WC powder having high hardness and high wear resistance. . However, if the WC content increases, the crack resistance of the outer layer will be impaired, so the WC content must be kept at 50% by weight or less based on the total amount. In addition, when the outer layer 2 is formed of high alloy steel, in order to impart wear resistance to the composite ring 1,
Usually quenching and tempering heat treatment is performed. As explained above, outer layer 2 and inner layer 3 are HIP
The composite ring 1 is integrally joined by processing, and in some cases, the composite ring 1 is subjected to quenching and tempering heat treatment. However, in contrast to these treatments, using a low carbon, low alloy steel consisting of a ferrite base for the inner layer 3 has various disadvantages. Extremely advantageous. In other words, the material made of such a ferrite base has a small coefficient of thermal expansion, so HIP
Deformation is small even with temperature changes during heating and cooling during processing, making it difficult for cracks and peeling to occur at the diffusion bonded surface.
Furthermore, during heat treatment of the composite ring 1, even if the entire ring is quenched, the quenching effect does not reach the inner layer 3.
No deterioration of toughness occurs. If the inner layer 3 has a hardening effect, it is undesirable because breakage tends to occur when the composite ring 1 is fitted into an assembled roll.
It is also possible to subject only the outer layer 2 of the composite ring 1 to the quenching heat treatment, but this is more complicated and less productive than heat treating the entire ring. As shown in Fig. 3, the composite ring of the present invention is a rolled ring having a hole 6 for rolling wire rods and steel bars, and only the periphery of the hole 6 being sintered with a material having excellent wear resistance. It is different from a composite ring in which a body 7 is embedded in a base 8 made of a tough metal and the two are diffusion bonded in terms of rolling purpose and use. When the composite ring 1 described above is used in a block mill or the like, it is used as it is without being assembled on a shaft, but as shown in FIGS. 4 to 6, it is often assembled on a shaft and used as an assembly roll. That is, as shown in FIG. 4, two composite rings 1 are shrink-fitted onto a shaft 11 having an annular protrusion 10 integrally formed on the outer periphery of the central portion, with the annular protrusion 10 in between, and a steel material or the like is fitted on the outside thereof. Fixing rings 12, 12 made of a strong material are fixed to the shaft 11 by shrink fitting, welding, screwing, or the like. The annular convex portion 10 does not necessarily need to be integrally formed with the shaft, and the shaft may be formed into a straight shape and a spacer ring 13 may be provided in the center, as shown in FIG. Figures 4 and 5 show examples in which auxiliary rings are provided at both ends of the roll body, but if you want to effectively use the length of the roll body, a composite ring is installed on the shaft 11 as shown in Figure 6. Of course, one piece or a plurality of pieces may be assembled as necessary. In FIG. 5, an appropriate number of two or more composite rings 1 may be fixed as required. In the composite ring 1 of the present invention, the outer layer 2 in contact with the rolled material is made of a high alloy material with excellent wear resistance or 50% by weight
Although the following WC powder is formed of a sintered body embedded in a high alloy material, the inner layer 3 is made of steel, so it has good workability and weldability, and is strong. Therefore, as shown in FIGS. 4 to 6, when fixing the composite ring 1 to the shaft (steel material or cast iron material),
It can be fixed to the shaft by conventionally used easy assembly methods such as shrink fitting, welding, or tight fitting by providing a keyway. In addition, even when a large rolling load is applied, it is possible to reliably prevent flying accidents caused by ring breakage that occur with conventional WC sintered rings. Furthermore, due to its excellent crack resistance, It can also be effectively used for low speed rolling. Next, a composite ring for flat steel rolling (φ320×500
An example of manufacturing the product (mm) will be described. (1) An inner ring with an inner diameter of 150 mm, an outer diameter of 230 mm, and a width of 150 mm was prepared. The inner ring contains C: 0.25%,
It is a low C steel with Si: 0.13% and Mn: 0.41%. (2) Cover the radially outer side of the inner ring with a can plate as shown in Figure 2, covering the entire width of the outer surface of the ring,
After filling the high alloy powder shown in Table 4 (100 mesh or less) and a mixed powder in which WC powder was added thereto, it was degassed. WC powder was added in Example 2.
30% of the total amount was added.

[Table] (3) Then, at a pressure of 200Kg/cm ² and a temperature of 1180℃
A HIP process was performed to sinter the powder to obtain an outer layer and to diffusion bond the outer layer and the inner ring.
After the HIP process was completed, the can plate was removed to obtain a composite ring. (4) For Example 1, after rough machining the HIP-treated composite ring to product dimensions, it was machined in a vacuum.
After heating at 1180℃ for 30 minutes and oil quenching, 530℃
A tempering heat treatment was performed. Regarding Example 2, no heat treatment is required and HIP
A composite ring was obtained which could be subjected to rolling by just processing. (5) The results of investigating the mechanical properties of the composite ring are presented in the fifth section.
Shown in the table.

[Table] From Table 5, the composite ring of Example 1 has a high hardness outer layer, excellent wear resistance, and high bending strength.
It can be seen that it is much superior to the WC sintered body (280Kg/mm ² ). In addition, the inner layers of both had no high alloy components mixed in and were strong, and no breakage was observed in the bending test. That is, it can be seen that the composite ring of the present invention has both excellent wear resistance and accident resistance. (6) The inner diameter of the above composite ring was processed with a grinder to improve accuracy, and as shown in FIG. 5, it was fixed by shrink fitting to obtain an assembled roll for flat steel rolling. (Effects of the Invention) As explained above, in the composite ring according to the present invention, only the part in contact with the rolled material is made of a high alloy material with excellent wear resistance and crack resistance, and this is made of a steel material with excellent toughness. Because it is integrally joined with the formed inner layer, it is low cost and has a long life as a sleeve for assembly rolls for rolling flat steel and plate materials, and it is also highly safe because it will not scatter even if it breaks. . Furthermore, since the outer layer and the inner layer are diffusion bonded by HIP processing, it is possible to prevent the high alloy component from entering the inner layer from the outer layer made of a high alloy material, and the toughness of the inner layer is not deteriorated. Therefore, if the composite ring of the present invention whose inner layer is made of a tough material is applied to an assembly roll, it can be assembled to the shaft at low cost using a simple shrink fit method, welding, screws, bolts, etc. Furthermore, the shaft can be reused. Furthermore, according to the manufacturing method of the present invention, it is possible to add and mix high-hardness, high-wear resistant WC powder to a single high-alloy powder serving as the outer layer, and to sinter these high-alloy powders and form the inner layer ring. and diffusion bonding can be performed at the same time, the desired composite ring can be produced extremely easily, and productivity is excellent as an industrial manufacturing method.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the composite ring according to the present invention, Fig. 2 is a cross-sectional view of the inner layer ring before HIP treatment, and Fig. 3 is a comparative example in which only the periphery of the hole is made of a material with excellent wear resistance. Cross-sectional views of composite rings, Figures 4 to 6
The figure shows a partial sectional view of an assembly roll to which the composite ring according to the present invention is applied, FIG. 7 shows a sectional view of a conventional carbide ring, and FIG. 8 shows a sectional view of a conventional assembly roll. 1...Composite ring, 2...Outer layer, 3...Inner layer.

Claims (1)

[Claims] 1. Consisting of an outer layer which is a rolling layer formed by sintering high alloy powder with excellent wear resistance and crack resistance, and an inner layer formed of a steel material with excellent toughness, A composite ring characterized in that the outer layer is formed over the entire width of the outer surface of the inner layer, and the outer layer and the inner layer are diffusion bonded by hot isostatic pressing. 2. The composite ring according to claim 1, wherein the inner layer is made of low carbon, low alloy steel comprising a ferrite base. 3. High alloy powder with excellent wear resistance and crack resistance is applied over the entire width of the outer surface of the inner ring made of steel with excellent toughness by hot isostatic pressing.
A method for manufacturing a composite ring, comprising: sintering the powder to form an outer layer that is a rolling layer, and diffusion bonding the outer layer and the inner ring.