JP2001294985A - Method for producing high-speed steel sleeve poll for polling and sleeve roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-speed steel sleeve roll for rolling in which production cost is kept in low without damaging the performances of wear resistance and toughness keeping those in the conventional method, and to provide a sleeve roll. SOLUTION: This method for producing a high-speed steel sleeve roll for rolling by a centrifugal casting method is composed of the first stage in which a cylindrical, hollow stock is cast in a high-speed steel molten metal, the second stage in which the cylindrical, hollow stock is cut in the direction vertical to the axis and the third stage in which the cylindrical, hollow stock after the cutting is subjected to upsetting hot forging, and the sleeve roll is produced thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-speed steel work roll for rolling used in steel rolling, for example, a high-speed sleeve roll for mold steel rolling and a sleeve roll.

[0002]

2. Description of the Related Art In recent years, as a method of manufacturing a high-speed sleeve roll, a method of manufacturing by cutting a cast material and a method of manufacturing a high-speed sleeve roll have been proposed.
Various methods have been tried, such as casting from powder by processing and manufacturing from ingots by electroslag remelting, but all are very expensive, and many steps are required in the subsequent manufacturing process. It could not be manufactured until after. On the other hand, the high-speed sleeve roll is relatively inexpensive as compared with the above various methods,
As a simple manufacturing method, a technology of manufacturing by a centrifugal casting method is disclosed in Japanese Patent Application Laid-Open No. 5-306426. The content disclosed in the above publication is to optimize the alloy components of the outer layer and to limit the carbide composition, so that the outer layer material has uniform wear resistance and crack resistance that does not cause the center of gravity segregation even under the action of centrifugal force. In addition, the present invention provides a high-speed sleeve roll in which a tough graphite steel is used for the inner layer material and the outer layer and the graphite steel are completely welded and integrated by metallurgy.

[0003] However, this technique still has the following problems unique to the centrifugal casting method. That is,
In the solidification process during centrifugal casting, the cooling rate of the outer surface in contact with the mold is higher than the cooling rate of the inner surface, so that the final solidification zone exists in the circumferential direction near the inner surface. The structure of this final solidification zone is a porous coarse structure zone known in casting. Leaving these in the product not only impairs toughness, but also during shrink fit, which is an assembling process to the shaft after manufacture, there is a risk of breakage of the sleeve, so that the inner surface has a coarse porous tissue band and It is necessary to remove the segregation zone on the outer surface by machining, so that the yield is lowered and many steps are required. As a result, the production cost of the sleeve roll becomes expensive.

Japanese Patent Application Laid-Open No. Hei 8-158018 discloses a technique for producing a high-speed steel roll by centrifugal casting and then reducing the porous coarse texture band by forging. However, the contents disclosed in the above publication are:
It is forging an integral roll by centrifugal casting, and in order to manufacture a sleeve roll targeted by the present invention, after forging, the forged material is drilled, for example, drilling, cutting of thick inner and outer surfaces, etc. A process requires a process, and therefore has many problems as a practical technique from the viewpoint of the process and the manufacturing cost.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art in a sleeve roll for rolling without impairing the wear resistance and toughness functions of the conventional method. Therefore, single or multiple layers of material are forged by centrifugal casting, the manufacturing process is shortened as much as possible by approximating the product shape, and further, the yield is greatly improved by eliminating the inner and outer surface processing, and the manufacturing cost is reduced. To provide a high-speed forged sleeve roll.

[0006]

In order to solve the above problems, the present invention has the following means. (1) In a method of manufacturing a high-speed sleeve roll for rolling by centrifugal casting, a first step of casting a cylindrical hollow material with a high-speed molten metal and a second step of cutting the cylindrical hollow material in a direction perpendicular to the axis. And the cylindrical hollow material after the cutting,
A method for producing a high-speed steel roll for rolling, comprising a third step of performing upsetting hot forging. (2) The method for manufacturing a high-speed steel sleeve roll for rolling according to the above (1), wherein in the third step, the hot forging is performed together with the upsetting hot forging.

(3) The high-speed steel sleeve for rolling according to the above (2), wherein hot forging of the expansion in the third step is performed using a round bar having irregularities formed on the surface in the circumferential direction as a core metal. Roll manufacturing method. (4) The method for producing a high-speed sleeve roll for rolling according to (1) or (2), wherein the forging ratio in the upsetting hot forging is set to 1.5 to 5.0. (5) The method according to (2) or (3), wherein the forging ratio in hot forging of the expanded tube is set to 1.1 to 3.0.

(6) A high-speed steel sleeve roll for rolling manufactured by a centrifugal casting method, wherein the high-speed steel sleeve roll for rolling is formed by upsetting hot forging into a cast cylindrical hollow material. Is a chemical component of 1.0 to 3.5% by mass, Si: 0.2 to
2.0%, Mn: 0.2-2.0%, Cr: 3.0-1
0.0%, V: 4.5 to 10.0%, Mo: 2.0 to 1
A high-speed sleeve roll for rolling, characterized by comprising 5.0%, W: 2.0 to 15.0%, the balance being Fe and unavoidable impurities.

(7) A high-speed stainless steel sleeve roll for rolling manufactured by centrifugal casting, which is formed by hot upsetting and expanded hot forging on a cast cylindrical hollow material. The chemical composition of the sleeve roll is, in mass%, C: 1.0 to 3.5%, S
i: 0.2 to 2.0%, Mn: 0.2 to 2.0%, C
r: 3.0 to 10.0%, V: 4.5 to 10.0%, M
o: 2.0 to 15.0%, W: 2.0 to 15.0%, a high-speed sleeve roll for rolling, comprising the balance of Fe and inevitable impurities. (8) The chemical composition of the sleeve roll is represented by mass%, and Ni: 0.2 to 5.0%, Co: 0.5 to 10.0.
%, Nb: 0.5 to 10.0%, one or more of them are added, and the high-speed sleeve roll for rolling according to claim 6 or 7 is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the respective chemical components of a high-speed forged sleeve roll for rolling according to the present invention will be described below. C: 1.0 to 3.5% C is an important element for obtaining hardness that directly affects the performance of the roll, and if the C content is less than 1.0%, abrasion resistance and rough skin resistance are obtained. There is little crystallization of hard carbide which is effective for improving the resilience, and the amount of C dissolved in the matrix is insufficient, so that sufficient matrix hardness cannot be obtained even by quenching and the effect of alloy additives is exhibited. Can not. On the other hand, 3.5
%, The hard but brittle carbides are coarsened, and the crystallization amount is also excessive, the strength is impaired, and cracking and surface layer peeling occur during use.

Si: 0.2-2.0% Si is added for the purpose of deoxidizing. However, 0.2
%, The effect is insufficient, and if it exceeds 2.0%, the toughness is reduced. Further, in order to ensure fluidity during casting, the range is set to 0.2 to 2.0%. Mn: 0.2 to 2.0% Mn is added for the purpose of deoxidation and desulfurization. But,
If it is less than 0.2%, the effect is insufficient, and 2.0%
%, The toughness is reduced.
To 2.0%.

Cr: 3.0 to 10.0% Cr combines with C to form mainly M ₇ C ₃ hard carbide at crystal grain boundaries, thereby improving wear resistance. M ₇ C ₃ carbides are relatively unlikely to segregate during centrifugal casting, but crystallize largely in the form of a network. If the amount is small, the amount of carbides is small and the effect cannot be sufficiently secured. On the other hand, if the amount is too large, the crystallization amount of carbides becomes excessive and the strength is impaired as described above. This crystallized carbide is destroyed by forging in the subsequent process, and the adverse effect can be reduced by refining.However, the amount of carbide in the structure does not change. 2. As an appropriate range to apply
0% or more and 10.0% or less.

V: 4.5 to 10.0% V is bonded to C preferentially to form an extremely hard and granular MC type carbide, that is, an extremely advantageous element for forming a VC carbide and improving wear resistance. It is. However, if it is less than 4.5%, the amount of VC carbide is insufficient and wear resistance cannot be ensured. If it exceeds 10%, VC carbide has low specific gravity and tends to segregate on the inner surface side during centrifugal casting, so that segregation occurs. Was set to 4.5 to 10.0% as a range that does not impair the suppression and the strength. Mo: 2.0 to 15.0%, W: 2.0 to 15.0% Mo and W are dissolved in a matrix in the same manner as Cr and strengthen the matrix, and combine with C to form a carbide. Form. For strengthening the matrix, the content must be at least 2.0% or more. However, if it exceeds 15.0%, coarse carbides are formed and the toughness is reduced. In addition, 15.
If it exceeds 0%, laminar segregation occurs. Therefore, M
The range of both o and W is set to 2.0 to 15.0%.

The basic components of the material of the present invention are as described above. However, depending on the size of the roll to which the material is applied, required characteristics of the roll used, and the like, the above-mentioned chemical component of the present invention may be used as other chemical components In addition to the above, the following components can be appropriately added. Ni: 0.2 to 5.0% Ni has an effect of improving hardenability when added at 0.2% or more. When a large curing depth is required such as a sleeve roll having a large diameter, it is added as required. However, if a large amount is added, the residual austenite becomes excessive and high hardness cannot be obtained.
Use in the range of 0% or less.

Co: 0.5-10.0% Most of Co forms a solid solution in the matrix and strengthens the matrix. Therefore, it has the effect of improving the hardness and strength at high temperatures. If the content is less than 0.5%, the effect is insufficient, and if the content exceeds 10.0%, the effect is saturated. Therefore, from the viewpoint of economy, 10.0% or less is desirable. C
Whether or not to add o may be determined appropriately, for example, in consideration of the high-temperature hardness and the reduction of the friction coefficient in use characteristics, and the necessity of the addition is appropriately determined.

Nb: 0.5 to 10.0% Nb combines with C like V to form MC carbide having high hardness. In the case of manufacturing by a centrifugal casting method, it has an effect of reducing segregation of VC carbide. But,
If it is less than 0.5%, the effect is insufficient, and 10.0%
If it is contained in excess, the MC carbides become too coarse, leading to a decrease in toughness. Regarding the selection of Nb addition,
For example, the necessity of the addition may be appropriately determined in consideration of reduction of inner surface segregation according to the amount of V added at the time of centrifugal casting.

Next, the features of the manufacturing method of the present invention will be described below. In the present invention, first, a cylindrical hollow material is manufactured by a centrifugal casting method. Thus, the hollow material can be formed into a sleeve shape at relatively low cost. next,
This is subjected to an annealing heat treatment, cut into a predetermined sleeve shape, and then forged. In the forging method, the cut sleeve is laid down, and upsetting forging is performed in a height direction (sleeve width direction). Here, the forging ratio is selected so as to have a predetermined strength. By this upsetting forging, the crystallized carbides and the weight segregation existing in the outer circumferential direction are destroyed, the strength is improved by miniaturization, and the porous solid existing in the inner circumferential direction, which is the final solidification zone after centrifugal casting. A sufficient forging effect is obtained without breaking the structure, and a predetermined high strength and uniform structure is obtained.

Here, in order to sufficiently destroy carbides and segregation and improve the material strength by imparting a forging effect to a porous structure, the forging ratio (cross-sectional area ratio) is set to 1.5.
It is necessary to do above. When the forging ratio of the material exceeds 5, the strength improvement rate due to the forging effect decreases, and increasing the forging ratio greatly affects the cost. As described above, the porous structure on the inner surface is improved by the upsetting forging, and a predetermined strength is obtained.For example, when the shape of the sleeve roll to be manufactured is large, the rolling stress is large and the sleeve roll and the like are used. In the case of, after the sleeve roll is manufactured, it is necessary to greatly increase the shrink fit stress when shrink fitting with the shaft material.
There is a risk of the sleeve roll breaking. Therefore, in this case, the following method may be added to further lightly forge only the inner peripheral surface portion and further increase the strength of the inner peripheral surface portion.

This is because, by applying a strong stress to the inner surface of a normal pipe forging within a certain temperature and performing forging, the inner peripheral surface portion is sufficiently plastically deformed with almost no plastic change in the outer layer. By densifying the inner peripheral surface structure, it is possible to manufacture a roll that can withstand a larger shrink fit stress. In the case of forging only the inner peripheral surface portion, for making the structure denser and increasing the strength, there is an effect at a forging ratio of 1.1 or more,
A forging ratio of 3 is sufficient to exert a forging effect on the entire thickness of the sleeve roll. Excessive forging not only increases the cost of the sleeve roll, but also induces cracks at both ends of the inner surface of the sleeve during forging, which is not preferable.

[0020] A support shaft (core bar) used for the above-described pipe expansion forging.
About, the usually used diameter is about 200 to 50
Instead of a round bar of about 0 mm, as shown in Fig. 1, change the shaft of the round bar with irregularities on the surface, reduce the contact area of the inner circumferential surface, apply a large stress, and actively apply the inner circumferential surface To train. In this case, the convex R dimension is preferably 20% to 70% of the commonly used round bar R. 20
%, The forging area of one forging becomes small, and the number of times of forging increases, thereby lowering the productivity. In addition, since the plastically deformed surfaces of the surfaces overlap with each other, a forging defect may occur, which is not preferable. If it exceeds 70%, the contact area, which is the above-mentioned effect, is reduced by applying a large stress to reduce the contact area.

In addition, the round bar having this unevenness reduces the contact area with the forged material, and has a sufficient axial strength to reduce the cooling effect of the round bar, thereby preventing forging cracks caused by cooling at the end of the ring. Not only does it have the effect of smoothing the sleeve rotation by the manipulator. Also,
By using the round bar and the round bar surface with the unevenness partially in the round bar, it is possible to perform surface layer forging and finish leveling forging without changing the jig. Hereinafter, examples of the present invention will be described together with conventional materials and comparative examples.

[0022]

EXAMPLES (Example 1) In order to confirm the function and effect of the sleeve roll of the present invention, the following test materials were prepared by centrifugal casting, and after a predetermined heat treatment, cut in a direction perpendicular to the axis.
Various tests were performed. Table 1 shows the forging method, forging ratio, and chemical composition of the test material at this time. No. 1 in Table 1. A ~
10 of J are test materials of the present invention, which are obtained by variously changing the forging ratio by upset casting after centrifugal casting and predetermined heat treatment. In addition, No. The four specimens K to N are also the test materials of the present invention, in which the forging ratio by the pipe expansion forging after the upsetting forging is variously changed. In addition, No. 4 of OR
The test piece is a conventional test material, the chemical composition of which is almost the same as that of the present invention, but subjected to the same predetermined heat treatment as the test material of the present invention after centrifugal casting. No upset forging, which is the configuration of the above, is performed. No.
Four specimens S to V are comparative test specimens, which are obtained by subjecting a test specimen having a chemical composition different from that of the present invention to upsetting forging and expanding forging in the same manner as in the present invention.

[0023]

[Table 1]

Next, a method of manufacturing the test material will be described. The molten metal of each of the chemical components shown in Table 1 melted in the high frequency induction furnace was poured into a cylindrical mold rotating at high speed in a centrifugal casting tester, and had an outer diameter of 174 mm and a wall thickness of 35 m.
m, a sleeve material having a length of 300 mm was produced. Thereafter, the material was cut at a plurality of points in the direction perpendicular to the axis, and the length was 60 mm.
A test material in the form of a sleeve was manufactured. After that, the test material was subjected to in-furnace annealing, and then upsetting forging with various forging ratios was performed using a 300t press. In addition, 1000 ° C
Was subjected to a quenching treatment at 550 ° C., and a microstructure test piece 3, a rotational wear test piece 2, and a tensile test piece 4 were collected from each of the test materials as shown in FIG.

Hereinafter, the test results of the test materials will be described. FIG. 3 shows a comparison of the microstructure at a depth of 10 mm from the sleeve surface between the material of the present invention (No. G as a representative material) and the conventional material (No. P as a representative material). That is, FIG. G
FIG. 3B is a photomicrograph showing the microstructure of the material, and FIG. 3 shows a micrograph showing the microstructure of the P material. From FIG. 3, in the case of the conventional material P, since only the centrifugal casting was performed and the upsetting forging was not performed, coarse carbide was crystallized in the microstructure, and overall uniformity was not achieved. On the other hand, in the case of No. 2 of the present invention. It is clear that in the case of G, the carbide was destroyed by the action and effect of the upsetting forging performed after the centrifugal casting, and changed to fine carbide. The tensile strength shown in Table 1 for evaluating toughness was 790 N / m for the conventional material P.
m ² ; For G, 110
The operation and effect of the upsetting forging performed after centrifugal casting are apparent from this point, which is as high as 8 N / mm ² .

Next, the material No. 1 of the present invention was used. 14 of A to N
No., conventional material No. Nos. O to R, Comparative material Nos. Using all four test materials S to V, a comparative test for abrasion resistance was carried out using a rotary wear tester shown in FIG.
In the comparative test, a mating material: SUS304 Test temperature: normal temperature Linear load: 60 N / mm Slip rate: 10% A test was performed under the same conditions of 5 × 10 ⁴ rotations, and the wear loss before and after the test was measured. FIG. 5 shows the measurement results of the loss on wear.

Conventional material No. As shown in Table 1, the four O-Rs have substantially the same chemical composition as the material of the present invention, but the upsetting forging after centrifugal casting, or the upsetting forging and centrifugal forging after centrifugal casting. It is presumed that, as a result of the microstructure test (representative P of the conventional material), coarse carbides were crystallized in any of the microstructures, and overall uniformity was not achieved. As a result, the wear loss in FIG. 5 is high. On the other hand, the material No. All 14 of A to N are subjected to upsetting forging after centrifugal casting, or upsetting forging and expansion forging after centrifugal casting, and the abrasion loss is significantly reduced due to the forging effect. Since the four comparative materials S to V had different chemical components from the material of the present invention, even if the same forging was performed, the wear loss could not be significantly improved. This is because there is a difference in the method of dispersing the high-hardness carbide due to the chemical component, the amount is smaller than in the case of the material of the present invention, and it is considered that the fineness of the carbide due to the destruction of the net-like carbide and the uniformizing effect are not small. .

Further, as shown in Table 1, a predetermined heat treatment was applied to each material, and a JIS No. 4 test piece 4 shown in FIG. 2 was collected and subjected to a tensile test at room temperature. As shown in Table 1, the tensile strength of the materials A to N of the present invention is dramatically increased by forging. This is because the material No. A ~
N, which is a material having substantially the same chemical composition as that of the conventional material No. N O ~
This is clear from comparison with R (without forging). In addition, the comparative material No. Nos. S to V are the materials of the present invention. Forged at the same forging ratio as L, but all have only about 80% strength. This clearly shows that the effect of the combination by the limitation of the chemical component system of the present invention and the implementation of forging is remarkable. As a result of the above test, the operation and effect of the present invention were clearly confirmed, and the following actual rolls for rolling were manufactured.

(Example 2) A hollow cylindrical material having an outer diameter of 1010 mm, an inner diameter of 450 mm, and a length of 2100 mm was cast by a centrifugal casting method using a high-speed molten steel.
Both ends and the middle were cut to produce four hollow materials having a length of 500 mm, and then forging upsetting with a forging ratio of 1.5 (height ratio) was performed. Further, the inner surface was deformed by pipe forging (forging ratio 1.1 / diameter). This is subjected to a curing heat treatment, and the outer surface is 30 mm on one side (conventionally, about 60 mm) and the inner surface is 40 mm on one side (conventionally, about 120 mm).
Finish machining), and then shrink-fitted to a roll shaft and used for actual H-section rolling. As a result, although it is light forging, the carbide structure is refined, the tensile strength is increased, and the porous defect that appears in the final solidification zone on the inner surface that has occurred unless the conventional heavy cutting is performed is UST
There was no test result. Also, no breakage of the roll occurred at the time of shrink fitting.

[0030]

As described above, the use of the high-speed forged sleeve roll for rolling formed by forging the material having the composition of the present invention makes it possible to significantly reduce the abrasion resistance due to the fine uniformity of the hard MC carbide. Thus, the life of the rolling roll can be prolonged. Further, there is an effect that the quality of a rolled product is significantly improved by improving the roll performance.
As described above, the present invention has an excellent effect that a high-performance roll having both wear resistance and toughness can be supplied at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing the shape of a core rod used for pipe forging,

FIG. 2 is a diagram showing a test material sampling position;

FIG. 3 is a micrograph (× 100) showing microstructures of a material of the present invention and a comparative material,

FIG. 4 is a view showing a rotating wear tester;

FIG. 5 is a diagram showing the results of a rotational wear test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sleeve 2 Rotation wear test piece 3 Microstructure test piece 4 Tensile test piece 5 Counterpart material (SUS304) 6 Rotation wear tester

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B22D 13/02 502 B22D 13/02 502T 502H C22C 38/38 C22C 38/38 38/58 38/58 (72 ) Inventor Osamu Kubo 46-59 Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Engineering Business Unit F-term (reference) 4E016 EA22 EA26 FA02 FA18 4E087 AA10 BA02 BA18 BA24 CA31 CB01 DA05 GA20 HA18 HB02

Claims (8)

[Claims] 1. A method for manufacturing a high-speed sleeve roll for rolling by centrifugal casting, comprising: a first step of casting a cylindrical hollow material with a high-speed molten metal; and a step of cutting the cylindrical hollow material in a direction perpendicular to an axis. A method for manufacturing a high-speed sleeve roll for rolling, comprising two steps and a third step of performing upsetting hot forging on the cylindrical hollow material after the cutting. 2. The method according to claim 1, wherein, in the third step, hot expanding forging is performed together with upsetting hot forging. 3. The high-speed steel sleeve roll for rolling according to claim 2, wherein the forging of the tube expansion in the third step is performed by using a round bar having irregularities on the surface in the circumferential direction as a core metal. Production method. 4. A forging ratio in upsetting hot forging of 1.5 to 1.5.
3. The method for producing a high-speed steel sleeve roll for rolling according to claim 1, wherein the value is 5.0. 5. The forging ratio in hot forging of an expanded pipe is from 1.1 to 1.1.
4. The method for producing a high-speed steel roll for rolling according to claim 2 or 3, wherein the value is 3.0. 6. A high-speed steel sleeve roll for rolling manufactured by centrifugal casting, comprising a rolled high-speed steel sleeve roll formed by upsetting hot forging in a cast cylindrical hollow material. Chemical components in mass%, C: 1.0 to 3.5%, Si: 0.2 to 2.0%, Mn: 0.2 to 2.0%, Cr: 3.0 to 10.0 %, V: 4.5 to 10.0%, Mo: 2.0 to 15.0%, W: 2.0 to 15.0% Rolling high-speed steel characterized by being composed of a balance of Fe and inevitable impurities. System sleeve roll. 7. A high-speed steel sleeve roll for rolling manufactured by a centrifugal casting method, which is formed by upsetting hot forging and expanding hot forging into a cast cylindrical hollow material. The chemical composition of the sleeve roll is, in mass%, C: 1.0-3.5%, Si: 0.2-2.0%, Mn: 0.2-2.0%, Cr: 3. 0 to 10.0%, V: 4.5 to 10.0%, Mo: 2.0 to 15.0%, W: 2.0 to 15.0% The balance consists of Fe and unavoidable impurities. High-speed sleeve roll for rolling. 8. The chemical composition of the sleeve roll is represented by mass%.
And one or more of Ni: 0.2 to 5.0%, Co: 0.5 to 10.0%, and Nb: 0.5 to 10.0%. The high-speed steel sleeve roll for rolling according to claim 6 or 7, wherein