JPH07115051B2 - Method for manufacturing composite sleeve for rolling roll - Google Patents

Description

The present invention relates to a sleeve for a composite roll for a rolling mill, in particular,
The present invention relates to a method of manufacturing a composite sleeve having good wear resistance and spall resistance.

[Prior Art] In recent years, rolling mills have tended to be rolled under an even higher pressure in accordance with the demand for extremely thin and uniform thickness and high gloss in rolling production. Therefore, the roll is required to have a small diameter and less flat deformation, and
There is a demand for spall resistance and wear resistance for the roll body and high strength and toughness for the roll shaft. In order to obtain a rolling roll having such contradictory properties at the same time, it has been considered to make the roll highly alloyed or compound.

For rolling rolls, whether hot or cold, the amount and distribution of carbides in the matrix are one of the important factors that influence roll properties.

In a high-alloyed rolling roll made of conventional ingot material, huge carbides and coarse dendrites are generated in the matrix,
There is a problem that spall resistance and wear resistance, especially uneven wear become problems during rolling, and heat treatment and forgeability are extremely difficult during manufacturing. This is a fatal drawback for ingots and is a limiting factor for the manufacturing method and components. Even in the composite roll in which the sleeve of the ingot material is joined to the core material, the sleeve is subjected to the melting-solidification process in the production of the sleeve,
In addition to the same problems as the conventional roll made of ingot, it is difficult to forge and it is difficult to improve strength and toughness, and the phenomena of spalling and peeling often occur.

Therefore, as a solution to this problem, a sleeve is formed from the metal powder produced by the rapid solidification method by the HIP method (hot isostatic pressure method), and at the time of forming, the inner canning material and powder HIP are used.
There is a method (Japanese Patent Laid-Open No. 61-1404) in which the materials are diffusion-bonded and the canning material of the sleeve is metallurgically melt-bonded to the arbor material at the center to form a composite roll. However, this technique is used for homogenizing the structure of the HIP layer and for arbor material (core material).
-Canning material-HIP material No consideration was given to strengthening the bonding of each boundary layer due to the difference in coefficient of thermal expansion or elastic coefficient between layers, and cracks were induced, causing problems as a rolling roll. It was That is, the deformation resistance of the composite roll manufactured by this method is outer layer (HIP material)> intermediate layer (canning material)> core material (build-up arbor material) from the viewpoint of its performance. When this is integrally heated as shown in FIGS. 2A to 2D and then tapped or press forged, a meat layer (core material) and an intermediate layer (canning material) are obtained.
Is preferentially stretched, and the homogenization of the structure of the outermost layer of the core and the joint strength with the intermediate layer material are insufficient, and the roundness and concentricity of the intermediate layer material and the core material are unsatisfactory. However, it has a problem that it is bent, twisted and sometimes cracked during use. Further, since the HIP and ESR (electroslag remelting) methods are adopted, it is difficult to reuse the arbor material (it is difficult to extract the arbor material from the sleeve) and the cost becomes high.

Further, a composite roll (Japanese Patent Publication No. 61-266106) in which two kinds of metal powders are sintered to form a sleeve and joined to an arbor material has been proposed. However, since this composite roll does not consider the influence of the difference in material properties between the two kinds of metal powder layers, it often causes problems such as crack generation and misalignment between the two layers.

Further, there is known a composite roll in which the surface of an arbor material is spray-coated (Japanese Patent Laid-Open Nos. 55-149710 and 52-88526.
No.), the required amount of thermal spray is large, and moreover, the constraint between the arbor and the thermal spray layer is large, so the residual stress after heat treatment is large,
Cracks are likely to occur during manufacturing or use, and reuse of arbor material is not easy.

[Problems to be Solved by the Invention] As described above, the conventional composite roll for a rolling mill has insufficient bonding strength in the boundary layer portion, large residual stress, and is likely to be cracked or peeled. However, there is a problem that it is difficult to homogenize the structure because it is difficult to forge only the sleeve portion, or it is difficult to reuse the arbor material.

The object of the invention of the present invention is that the homogenization and densification of the structure are good, the residual stress is small, the bonding strength of the boundary layer part is good, cracks and peeling hardly occur, and the arbor material can be reused. Another object of the present invention is to provide a method for manufacturing a composite sleeve for a rolling mill roll, which is excellent in spall resistance and wear resistance.

[Means for Solving the Problems] The above-mentioned object is to achieve a thickness of the outer sprayed layer after spraying a high alloy steel powder having wear resistance and spall resistance on the outer peripheral portion of a cylinder having high strength and high toughness. And, it is achieved by performing the gradient forging so that the temperature of the portion extending to a slight depth from the outer peripheral portion of the cylinder is set to a temperature suitable for the constraint forging and the temperature of the other portions is lower than that, and then performing the constraint forging.

[Example] As shown in FIG. 4, the outer periphery of a high-strength / high-toughness cylinder 6 (preferably made of the same material as the arbor) has a spall resistance and a spall resistance that can cope with a reduction in roll diameter and rolling under high pressure. A high alloy steel powder having wear resistance and higher deformation resistance and elastic modulus than the cylindrical material 6 is sprayed under reduced pressure to form a sprayed layer 5,
If necessary, diffusion sintering for strengthening the bond between the cylinder 6 and the sprayed layer 5 is performed to produce a composite sleeve material as shown in FIG. As shown in FIG. 1, this composite sleeve material is subjected to gradient heating and constrained forging to effectively forge only the sprayed layer 5 without substantially plastically deforming the cylinder 6, and then machined. To form a composite sleeve. The composite sleeve thus produced is joined to the arbor material by a shrink fit method or the like to obtain a rolling machine-melted composite roll.

FIG. 3 is a schematic view of an apparatus used for the above gradient heating and constraint forging, 7 is a cooling and forging jig whose inside is cooled with water through a cooling water supply port 12 and a drain port 13, and 8 is pressure rotation. A joint, 9 is a rotating disk. Reference numeral 10 is an induction heating device, and 11 is a restraint forging machine, which can move up and down and left and right as shown by arrows.
15 is a sleeve pedestal. As shown in FIG. 3, the composite sleeve material is fitted into a cooling / forging jig 7 and supported by a sleeve pedestal, and heating / cooling / forging jig 7 by an induction heating device 10 is carried out.
By controlling the inner surface cooling by
As shown in the partially enlarged view in the figure, a portion over the thickness D ₁ of the sprayed layer 5 and a slight depth t of the outer peripheral portion of the cylinder 6 has a temperature suitable for constrained forging, and other portions have a temperature lower than that. The temperature distribution 4 is set so as to obtain the lowered temperature (this is the gradient heating). In this way, the constrained forging machine 11 performs constrained forging from the surroundings on the gradient-heated composite sleeve material (note that the gradient-heated and constrained forging are performed while rotating the composite sleeve material). Thereby, only the sprayed layer 5 is effectively forged without substantially plastic deformation of the cylinder 6.

Using the above device, it is easy to create a temperature gradient during heating,
Only the sprayed layer 5 and the joint between the sprayed layer 5 and the cylinder 6 can be efficiently forged, and the residual stress can be reduced.

By performing the gradient heating and the constrained forging as described above, the pores in the sprayed layer 5 are pressure-bonded, and at the same time, the structure is homogenized, and the bonding between the cylinder 6 and the sprayed layer 5 is strengthened. The performance of high alloy steel powder can be exhibited sufficiently compared with the composite roll. The conventional composite roll with thermal spray overlay on the arbor not only increases the amount of thermal spray, but also has a large residual stress after heat treatment due to the large constraint between the arbor and the thermal spray layer, causing cracking during manufacture or use. On the other hand, in the composite roll obtained by the present invention, the residual stress can be divided by the sleeve, the reliability is improved accordingly, and the arbor can be reused.

Examples of the present invention will be specifically described below. 1% C-3%
Cr-0.3% Mo-remaining Fe composition composition 400 mm outer diameter, inner diameter
3.0% C on the outer circumference of a cylinder (forged material) with a length of 340 mm and a length of 1400 mm
Powder of high carbon-high chromium steel having a composition of -20% Cr-3% Mo-remaining Fe is sprayed to a thickness of 25 mm under reduced pressure (current 800
After applying A, voltage 70 V, and decompression degree 200 Torr), it was heated in a vacuum of 10 ⁻³ Torr for 10 hours at 1050 ° C. to perform diffusion bonding between the cylindrical material and the sprayed layer. The above-mentioned thermal spraying is described in JP-A-60-158906 (Japanese Patent Application No.
-14846), the composition of the thermal spray powder is gradually changed so as to gradually change from the composition near the cylinder on the surface of the cylinder to the hard composition in the surface layer, and the surface layer 20 mm Was sprayed to the above high carbon-high chromium steel. Regarding the composite sleeve material (FIG. 4) consisting of the cylinder 6 and the sprayed layer 5 thus produced,
Gradient heating-restraint forging was performed as shown in Fig. 1 using the device of Fig. 3, and then machined to give an inner diameter of 340 mm and an outer diameter of 4
I made a composite sleeve with a length of 40 mm and a length of 1400 mm. In the above gradient heating, the temperature of the part (D ₁ + t) shown in FIG. 3 is heated to 1150 ° C. Further, the constrained forging is performed by rotating the composite sleeve material with a four-sided tap forging machine. I did. The composite sleeve thus produced was joined to an arbor material (forged material) by a spring method and subjected to a predetermined treatment to produce a composite roll. This composite roll and a composite roll of the same material produced by a conventional method (Japanese Patent Publication No. 61-1404) were used for comparison in an actual machine for rolling a stainless steel plate.

As a result, cracking and peeling from the cylindrical side, which were often seen in the composite rolls made by the conventional method, were hardly seen in the composite rolls of the above-mentioned examples of the present invention. This can be explained from the measurement results of the residual stress measured by the Zachs method shown in FIG. That is, it was found that in the conventional method, residual stress is concentrated near the boundary between the outer layer and the inner layer (canning material) in the sleeve, which induces the generation of cracks. On the other hand, in the examples of the present invention, the residual stress was alleviated by sequentially changing the composition of the sprayed components as described above.

Further, the composite roll of the present invention example has a remarkable effect of forging, and compared with the composite roll made by the conventional method, the spall resistance is improved by 1.5 to 2.0 times and the surface accuracy and properties of the material to be rolled are improved. It was confirmed. Furthermore, the problem of the bondability with the arbor, which has been a problem in the past, disappears.

The optimum value of the ratio of the thickness of the sprayed layer 5 and (D ₁₎ and the thickness of the cylinder _{6 (D 2) (D 1} / D 2) was confirmed to be 0.25 to 1.5 experimentally. That is, if D ₁ / D ₂ is large, the forgeability of the sprayed layer is poor, and if D ₁ / D ₂ is 1.5 or more, the cylinder 6 will also be plastically deformed despite the above-mentioned gradient heating. Within the above displacement, the forging effect of the sprayed layer 5 also decreases, and the number of holes due to non-welding increases as shown in FIG. Therefore D ₁ / D
₂ must be 1.5 or less, preferably 1.2 or less. Also, if D ₁ / D ₂ is small, the forging effect improves, but not only the required sprayed layer cannot be obtained, but also the gradient of residual stress in the sprayed layer becomes steep and macro cracks occur in the sprayed layer. Cause. Moreover, there is a risk of delamination at the boundary between the sprayed layer and the cylinder, and the experimental results show that the lower limit of D ₁ / D ₂ is 0.25.

The composite roll according to the present invention can be used for both hot and cold, work and reinforcing rolls, and has a long life.

FIG. 7 to FIG. 10 show another example of the composite roll obtained by the present invention, which is used for hole rolling of wire rod, diamond box, die steel and the like. Each has a life of 1.2 to
It is similar in that it extends about 2.5 times, is easy to install, can reuse the arbor many times, and has the various effects described above.

[Advantages of the Invention] Since only the sprayed layer and the joint portion between the sprayed layer and the cylinder can be forged, and the forging effect of the sprayed layer can be enhanced, compression of pores in the sprayed layer, densification of the structure, and homogenization are achieved, The spall resistance and wear resistance are improved, the joint between the sprayed layer and the cylinder is strengthened, the residual stress is reduced, and cracks and peeling are hardly generated. The arbor can be reused.

[Brief description of drawings]

1 (a), (b), (c) and (d) are views showing a manufacturing process of a composite sleeve according to the present invention, and FIG. 2 (a),
(B), (c) and (d) are views showing a manufacturing process of a composite roll by a conventional method, FIG. 3 is an illustration of an apparatus used for performing gradient heating and restraint forging, and FIG. 4 is a view showing the present invention. FIG. 5 is a perspective view of the composite sleeve material, FIG. 5 is a view showing the result of measurement of residual stress, FIG. 6 is a view showing the relationship between the ratio of the thickness of the sprayed layer to the thickness of the cylinder and the porosity, FIGS. FIG. 10 is a cross-sectional view exemplifying the compound roll for groove rolling obtained by the present invention. 1 …… HIP material layer, 2 …… Canning material 3 …… Core material, 4,4 ′ …… Temperature distribution curve 5 …… Sprayed layer, 6 …… Cylinder 7 …… Cooling and forging jig, 9 …… Rotation Disk 10 …… Induction heating device, 11 …… Constrained forging machine 12 …… Cooling water supply port, 13 …… Drain port 15 …… Sleeve pedestal, 16 …… Arbor

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A 64-5611 (JP, A) JP-A 60-158906 (JP, A) JP-A 58-204170 (JP, A) JP-A 58- 167007 (JP, A) JP 61-1404 (JP, A) JP 55-149710 (JP, A) JP 52-88526 (JP, A) JP 61-266106 (JP, B2)

Claims (1)

[Claims] 1. A high alloy steel powder having wear resistance and spall resistance is sprayed on the outer peripheral portion of a cylinder having high strength and high toughness, and then the thickness of the sprayed layer and slightly inside the outer peripheral portion of the cylinder. Method for producing a composite sleeve for a rolling roll, which comprises performing constraint forging after performing gradient heating so that a portion up to a depth of up to .