JP2006297427A - Method for manufacturing forged sleeve roll for rolling wide flange shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a forged sleeve roll for rolling a wide flange shape which is excellent in wear resistance, heat-crack resistance, fouling resistance, surface-roughening resistance, tenacity, etc., for example, inexpensively and easily. <P>SOLUTION: At first, a cylindrical hollow base stock is cast by using the molten steel consisting of high-speed steel series components by a centrifugal casting method. Next, the surface-layer forging of only the outer peripheral portion in the radial direction which is the using surface of the sleeve roll is performed to the cylindrical hollow base stock in the axial direction of the cylindrical hollow base stock. Further, the die forging of only the outer peripheral portion in the radial direction which is the using surface of the sleeve roll is performed to the cylindrical hollow base stock after forging the surface layer. In this way, by intensively imparting forging effect to the using surface of the sleeve roll, hard carbides and dendrites are sufficiently destroyed and micronization and homogenization are made possible. Then, the sleeve roll for rolling excellent in the mechanical property is provided inexpensively and easily. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a forged sleeve roll for rolling H-shaped steel used for rolling a material to be rolled such as H-shaped steel.

  As the sleeve roll for H-type steel rolling, there are one manufactured by a centrifugal casting method or one formed by forging from a steel ingot. Both of these H-shaped steel rolling sleeve rolls have a problem that their wear period is limited due to insufficient wear resistance or seizure. As a countermeasure to this problem, wear resistance has been improved by applying a high-speed steel (HSS) material to the roll use surface, but heat crack resistance and seizure resistance have been improved. It did not lead to improvement of sex.

  Therefore, a high-speed forged sleeve roll is applied as such an improvement measure, which is disclosed in Patent Document 1. The technical content described in Patent Document 1 is that a single-layer sleeve material or a composite sleeve material molded by a centrifugal casting method using a molten metal composed of a high-speed component is radial from the outer and inner surfaces, and further from the axial direction. Also, forging is performed to form a sleeve roll.

JP 2000-288708 A

  However, for example, a sleeve roll for rolling H-shaped steel, particularly a small-sized sleeve roll for rolling H-shaped steel, has a flange 34 that is equal to or larger than the width of the rolled portion 32 as shown in FIG. In order to manufacture the rolled sleeve roll 30 for H-shaped steel having such a flange 34 with the technical contents disclosed in the above-mentioned Patent Document 1, as shown in FIG. 4, forging in the radial direction y and the axial direction z In order to form the flange portion 32 of the sleeve roll 30 from the cylindrical hollow material 150 formed by the above process, it is necessary to remove the surplus portions 152 (portions with dot hatching) on both shoulders by machining. It is. However, the removed surplus portion 152 is a portion where the forging effect with a lot of plastic deformation is large due to the forging. Accordingly, if the surplus portion 152 having such a high forging effect is removed by machining, the mechanical properties (for example, wear resistance, Heat crack resistance, seizure resistance, rough skin resistance, toughness, etc.) are low.

  As another method for manufacturing the rolled sleeve roll 30 for H-shaped steel, there is a method of forging and forming a centrifugally cast cylindrical hollow material at once by die forging. However, this method has a problem that a large-capacity press facility is required and the molding and processing costs increase.

  Accordingly, the present invention has been made in view of the above problems, and the object of the present invention is to provide mechanical properties such as wear resistance, heat crack resistance, seizure resistance, rough skin resistance, toughness. It is an object of the present invention to provide a new and improved method for producing a forged sleeve roll for rolling H-shaped steel, which can easily produce a forged sleeve roll for rolling H-shaped steel having excellent properties and the like at low cost.

  In order to solve the above problems, according to one aspect of the present invention, a method for producing a forged sleeve roll for H-shaped steel rolling is provided. The manufacturing method includes a casting process in which a cylindrical hollow material is cast by a centrifugal casting method using a molten metal composed of a high-speed component; and a radially outer peripheral portion that serves as a use surface of the sleeve roll with respect to the cylindrical hollow material. A surface layer forging step in which the cylindrical hollow material is surface-forged in the axial direction; only the outer peripheral portion in the radial direction serving as the use surface of the sleeve roll is formed in the cylindrical shape with respect to the cylindrical hollow material after the surface layer forging. A die forging step of die forging in the axial direction of the hollow material.

  Thus, by partially forging the cylindrical hollow material cast from the high-speed component, the hard carbides and dendrites can be sufficiently destroyed and made fine and uniform. For this reason, for example, a high-speed forged sleeve roll having improved mechanical properties such as wear resistance, heat crack resistance, seizure resistance, rough skin resistance, and toughness can be provided. Furthermore, by introducing the surface layer partial forging and the die forging process, the forging effect can be imparted to the use surface of the sleeve roll. In addition, compared with the method of forging a cylindrical hollow material that has been centrifugally cast by die forging at a time, the press equipment can be of a small capacity, and the molding and processing costs can be reduced.

  In the casting step, a composite cylindrical hollow material is made by centrifugally casting a molten metal made of graphite cast steel or ductile cast iron on the inner peripheral surface of a cylindrical hollow material cast with the molten metal made of the high-speed component. You may make it include the process of forming. Thereby, the composite sleeve roll excellent in the mechanical characteristics can be manufactured easily and inexpensively.

  Further, after the casting step, the surface layer forging further includes a cutting step in which the cast cylindrical hollow material is cut in a direction perpendicular to the axis of the cylindrical hollow material to have a predetermined length in the axial direction. In the process, the cut cylindrical hollow material may be surface forged. Thereby, the cylindrical hollow raw material according to the shape of a desired sleeve roll can be easily shape | molded from the cast cylindrical hollow raw material, and it can use for a forge process.

  Further, in the surface layer forging step, the radial outer peripheral portion of the cylindrical hollow material may be partially surface-forged sequentially and partially overlapping along the circumferential direction. Thereby, only the outer peripheral part equivalent to the use surface of a sleeve roll among cylindrical hollow materials can be suitably light forged.

  Moreover, the molten metal which consists of the said high speed system component is the mass%, C: 1.0-3.5%, Si: 0.2-2.4%, Mn: 0.2-2.0%, Cr: It contains 3.0 to 10.0%, V: 4.5 to 10.0%, and one or more of Mo and W: 0.2 to 10.0%, with the balance being Fe. Also good.

  Moreover, in order to solve the said subject, according to another viewpoint of this invention, the forged sleeve roll for H-shaped steel rolling manufactured by the manufacturing method of the forged sleeve roll for H-shaped steel rolling mentioned above is provided.

  As described above, according to the present invention, a high-performance forged sleeve roll for rolling H-shaped steel excellent in physical properties such as wear resistance, heat crack resistance, seizure resistance, rough skin resistance, and toughness, It can be easily provided at low cost.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
First, chemical components of the forged sleeve roll for rolling H-shaped steel according to the first embodiment of the present invention will be described. The forged sleeve roll for rolling H-shaped steel according to the present embodiment (hereinafter sometimes simply referred to as “sleeve roll” or “roll”) is, for example, a composite rolled sleeve roll having a two-layer structure composed of an outer layer material and an inner layer material. It can be. The outer layer material of the forged sleeve roll for rolling H-shaped steel is made of a high-speed component as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-81918. This high-speed component is a component that becomes a material of high-speed steel (white cast iron or the like) containing a large amount of V, Cr, Mo, W, or the like. Below, the component content and the reason for component limitation are demonstrated about each typical component. In addition, the content ratio of the following each component is the mass%.

C: 1.0 to 3.5%
Carbon C is an important element for obtaining roll hardness that directly affects roll performance. When the C content is less than 1.0%, there is little crystallization of hard carbides effective for improving wear resistance and rough skin resistance, and the amount of C dissolved in the matrix is insufficient. However, not only cannot a sufficient base hardness be obtained, but also an effect as an alloy additive cannot be exhibited.

  On the other hand, if the C content exceeds 3.5%, the hard but brittle carbides become coarse, and the amount of crystallization becomes excessive, and the strength of the roll is impaired. For this reason, breakage or surface peeling occurs during use of the roll, and it cannot be used. Therefore, 3.5% was made the upper limit of the C content.

Si: 0.2-2.4%
Silicon Si is added for the purpose of deoxidation. If the Si content is less than 0.2%, the deoxidation effect is insufficient. On the other hand, if it exceeds 2%, the toughness is lowered. Moreover, in order to ensure the fluidity at the time of casting, the range of Si content shall be 0.2 to 2.4%.

Mn: 0.2 to 2.0%
Manganese Mn is added for the purpose of deoxidation and desulfurization. If the Mn content is less than 0.2%, the deoxidation and desulfurization effects are insufficient, while if it exceeds 2.0%, the toughness is lowered. For this reason, the range of Mn content shall be 0.2 to 2.4%.

Cr: 3.0 to 10.0%
Chromium Cr combines with C to crystallize and generate hard carbides such as M ₇ C ₃ type mainly at the grain boundaries, thereby improving wear resistance. M ₇ C ₃ carbides are relatively difficult to segregate even during centrifugal casting, but are largely agglomerated and crystallized in a network. If the amount of Cr added is small, the effect of the carbide is small and the effect cannot be sufficiently secured. On the other hand, if the amount of Cr added is too large, the amount of crystallized carbide becomes excessive and the strength is impaired as described above.

  The carbides that crystallize are destroyed and refined during forging, thereby reducing the adverse effects. However, the amount of carbide in the structure does not change, and excessive crystallization still has an adverse effect, so the appropriate range of Cr content was set to 3.0% to 10.0%.

V: 4.5 to 10.0%
Vanadium V is an extremely useful element for preferentially combining with C to form an extremely hard and granular MC type carbide, that is, VC carbide, and improving wear resistance. However, if the V content is less than 4.5%, the amount of carbide is insufficient and wear resistance cannot be ensured. On the other hand, if it exceeds 10.0%, the VC carbide has a low specific gravity, so it is not suitable for centrifugal casting. It becomes easy to segregate weight on the inner surface side. For this reason, V content was made into 4.5 to 10.0% as a range which does not impair suppression and intensity | strength of segregation.

Mo, W: more than 1 type 0.2 ~ 10.0%
Molybdenum Mo and tungsten W are solid-solved in the matrix and strengthen the matrix, and combine with C to form carbides, similarly to Cr. In order to strengthen the base, it is necessary to contain at least 0.2%, but if it exceeds 10.0%, coarse carbides are formed and the toughness is lowered. Moreover, when it exceeds 10.0% by the centrifugal casting method, layered segregation occurs. Therefore, the Mo and / or W content is set to 0.2 to 10.0%.

  The basic components of the outer layer material of the sleeve roll according to the present embodiment are as described above. In addition to the chemical components described above, the following components may be used depending on the size of the roll to be applied and the required usage characteristics of the roll. Ni, Co, and Nb may be added as appropriate.

Ni: 0.1 to 3.0%
Nickel Ni has the effect of improving the hardenability of the base and increasing the hardness. In order to improve the hardenability, a Ni content of 0.1% or more is necessary. However, if the Ni content exceeds 3.0%, the retained austenite increases and the hardness decreases, so the upper limit was made 3.0%.

Co: 0.5-10.0%
Cobalt Co has the effect of improving hardness and strength at high temperatures. This is effective when manufacturing rolls used under rolling conditions that require high temperature wear resistance and thermal cracking. Although it is effective to add 0.5% or more of Co, the upper limit of the content is set to 10.0% or less from the viewpoint of economy.

Nb: 0.1-3.0%
Niobium Nb, like V, combines with C to produce hard MC carbides and improves wear resistance. Nb is added together with the above V, so if the content is not more than 0.1%, there is no effect. On the other hand, if it exceeds 3.0%, MC carbide increases and the base hardness decreases. End up.

  Further, the balance other than each component of the outer layer material is composed of Fe and inevitable impurities. On the other hand, the inner layer material of the sleeve roll is made of, for example, graphite cast steel or ductile cast iron.

  Next, the manufacturing method of the forged sleeve roll for H-shaped steel rolling concerning this embodiment is demonstrated. The feature of the manufacturing method of the forged sleeve roll for rolling H-shaped steel according to the present embodiment is that the cylindrical hollow material cast using the molten metal composed of the above-described high-speed component is only partially in the portion that becomes the roll use surface. In this point, surface forging and die forging are performed.

  First, the reason why such forging is performed will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a rolled state of the H-shaped steel 10 using the forged sleeve roll 30 for rolling H-shaped steel according to the present embodiment.

  As shown in FIG. 1, a forged sleeve roll 30 for rolling H-shaped steel is inserted into and fixed to a roll shaft 20 and is integrated into a rolling mill (not shown). At this time, the roll shaft 20 inserted into the sleeve roll 30 is disposed so as to be horizontal, for example. A pair of the forged sleeve roll 30 and the roll shaft 20 for rolling the H-shaped steel are disposed so as to face, for example, the vertical direction (the rolling direction y). In FIG. 1, a sleeve roll 30 that is a lower horizontal roll is indicated by a solid line, and a sleeve roll 30 that is an upper horizontal roll is indicated by a one-dot chain line, and both sleeve rolls 30 have, for example, the same shape and the same size.

  The forged sleeve roll 30 for rolling H-shaped steel is composed of a rolling part 32 positioned on the outer periphery side of the roll and a flange part 34 positioned on the inner peripheral side of the roll. The width of the rolling part 32 in the roll axis direction z is narrower than the width of the flange part 34 in the roll axis direction z. For this reason, on both side surfaces of the sleeve roll 30, a step is generated between the rolled portion 32 and the flange portion 34.

  With such a pair of forged sleeve rolls 30 for rolling H-shaped steel, the H-shaped steel 10 is rolled with the vertical direction as the rolling direction y. In this rolled state, the H-shaped steel 10 to be rolled and the forged sleeve roll 30 for rolling the H-shaped steel, which is the lower horizontal roll, are in contact with each other at the following points (1) and (2). The shape steel 10 is rolled and conveyed.

(1) A surface which is a contact portion between both inner side surfaces 14a of the flange 14 of the H-shaped steel 10 and both side surfaces 32a of the rolled portion 32 of the sleeve roll 30 (2) The lower surface 12a of the web 12 of the H-shaped steel 10 and the B surface which is a contact part with the outer peripheral surface 32b of the rolling part 32 of the sleeve roll 30

  The sleeve roll 30 which is an upper horizontal roll is also in contact with the H-shaped steel 10 in the same manner as the lower horizontal roll.

  When the H-shaped steel 10 is rolled using such a forged sleeve roll 30 for rolling H-shaped steel, the conveyance force required for rolling the H-shaped steel 10 is largely due to the following frictional forces (a) and (b).

(A) Friction force on the B surface which is a contact portion between the H-shaped steel 10 and the outer peripheral surface 32b of the sleeve roll 30 (b) In rolling the H-shaped steel 10, it is normally disposed on both the left and right sides of the H-shaped steel 10. Frictional force at the contact portion between a pair of scissors rolls (not shown) and the flange outer surface 14b of the H-shaped steel 10 At the contact portion that exerts such a conveying force, the rolled H-shaped steel 10 and the sleeve roll 30 Slip is unlikely to occur.

  On the other hand, the A surface of the forged sleeve roll 30 for rolling H-shaped steel shown in FIG. 1 has a smaller distance from the axis of the roll shaft 20 than the B surface. For this reason, even if the angular velocities on both sides A and B are the same, a difference occurs in the speed of the H-shaped steel 10 in the rolling / conveying direction. Accordingly, wear, heat cracking, seizure, and roughening of the surface of the sleeve roll 30 are larger than those of the B surface at the A surface of the sleeve roll 30 (i.e., both side surfaces 32a of the rolled portion 32), particularly at a location close to the foot portion 14b of the H-shaped steel 10. There is a problem that occurs. Therefore, in order to solve this problem, the present invention provides a main portion to be solved in the forged sleeve roll 30 for rolling H-shaped steel, that is, a use surface, as shown in FIG. 1 (hereinafter referred to as “use surface A”). It is going to measure the forging effect of.

  Next, based on FIG. 2, the process flow of the manufacturing method of the forged sleeve roll for H-shaped steel rolling concerning this embodiment is demonstrated in detail.

  The method for producing a forged sleeve roll for rolling H-shaped steel according to the present embodiment includes (1) a casting process in which a cylindrical hollow material is cast by centrifugal casting using a molten metal composed of the above-described high-speed steel component, and (2) the casting A cutting step of cutting the cylindrical hollow material having a predetermined length in the axial direction, and (3) only a radially outer peripheral portion corresponding to the use surface A of the sleeve roll 30 among the cut cylindrical hollow material, A surface forging step of partially forging the surface layer, (4) a die forging step of die forging only the outer peripheral portion in the radial direction corresponding to the use surface A of the surface hollow forged cylindrical hollow material, and (5) a finishing step. And. Hereinafter, each of these steps will be described in detail.

(Casting process)
First, the casting process will be described. In the casting process, first, a cylindrical hollow material 50 as shown in FIG. 2A is cast by a centrifugal casting method using the above-described molten metal composed of a high-speed component. By such centrifugal casting, the sleeve-shaped cylindrical hollow material 50 can be manufactured relatively inexpensively and easily.

  Next, in the present embodiment, in order to manufacture a composite sleeve roll, a molten metal such as graphite cast steel or ductile cast iron is centrifugally cast and welded to the inner peripheral surface of the cylindrical hollow material 50 cast as described above. A composite cylindrical hollow material 50 is formed. Thereby, the cylindrical hollow material 50 has a two-layer structure of the outer layer material made of the high-speed component and the inner layer material made of the graphite cast steel or the ductile cast iron. In addition, when manufacturing the single layer sleeve roll which consists of the said high-speed type | system | group component, the 2nd step centrifugal casting process for welding the said graphite cast steel etc. can be skipped.

  Further, the cylindrical hollow material 50 thus cast is subjected to a sinter heat treatment.

(Cutting process)
Next, in the cutting step, the cylindrical hollow material 50 cast in the casting step is perpendicular to the axis (roll radial direction xy) so as to have a predetermined length L in the axial direction z as shown in FIG. 2B. Disconnect. That is, the length (height) in the axial direction z of the cylindrical hollow material 50 cast as described above is longer than the length in the axial direction z of the forged sleeve roll 30 for rolling H-shaped steel as the final product. Therefore, in this cutting step, the cylindrical hollow material 50 is cut to form cylindrical hollow materials 50-1, 2,... Having a predetermined length L corresponding to the length of the forged sleeve roll 30 for rolling H-shaped steel. To do. Here, the “predetermined length L” is an extra length of, for example, about 20 to 30 mm as a finishing allowance by machining from the axial length of the forged sleeve roll 30 for rolling H-shaped steel as the final product.

  In this way, by cutting the cylindrical hollow material 50 and forming a plurality of cylindrical hollow materials 50-1, 2,... Since the cylindrical hollow materials 50-1, 2,... Can be molded, the production efficiency can be increased and the production cost can be reduced.

  However, the present invention is not limited to this example. In the cutting step, the cast cylindrical hollow material 50 is cut to adjust the length, and the cylindrical hollow material 50-1 having the predetermined length L is cut into one. Only one may be molded. Further, the cylindrical hollow material 50 having the predetermined length L may be cast in advance in the casting process, and in this case, the cutting process can be omitted. In the following description, the cylindrical hollow materials 50-1, 2,... Having a predetermined length L manufactured by the above-described cutting will be described as a cylindrical hollow material 50.

(Surface forging process)
In the surface layer forging step (light forging step), for example, by a large-sized free forging machine (not shown), as shown in FIG. 2C, the radial direction serving as the use surface A of the sleeve roll 30 in the cylindrical hollow material 50. Partial surface forging is performed in which only the outer peripheral portion 52 is reduced in the axial direction z (sleeve width direction) of the cylindrical hollow material 50. "Surface forging" is a forging method in which only the surface layer portion in the forging direction of the material to be forged is partially crushed using an anvil or the like to cause plastic deformation.

  Specifically, first, the cylindrical hollow material 50 after the cutting is placed and fixed on the base 62 of the large-sized free forging machine so that the axial direction is the vertical direction. A concave portion 64 having a circular planar shape is formed on the upper surface of the pedestal 62. The diameter of the concave portion 64 is smaller than the outer diameter of the cylindrical hollow material 50, and the flange portion 34 of the sleeve roll 30 of FIG. Is substantially the same as the outer diameter.

  Next, for example, using the surface forging anvil 66, only the radially outer peripheral portion 52 that becomes the use surface A of the sleeve roll 30 among the placed cylindrical hollow material 50 is removed from the cylindrical hollow material 50. Surface forging is partially performed so as to reduce in the axial direction. At this time, the indentation amount is selected so as to obtain a predetermined surface plastic deformation amount. Furthermore, in the surface layer forging, the outer peripheral portion 52 of the cylindrical hollow material 50 that becomes the use surface A of the sleeve roll 30 is partially surface-forged sequentially overlapping the entire circumferential direction. More specifically, an anvil 66 for surface layer forging is partially overlapped along the circumferential direction as shown by P, Q,... Shown in FIG. Sequentially forging the surface layer with partial action.

  Further, as shown in FIG. 2C (b), after the cylindrical hollow material 50 is turned upside down, only the outer peripheral portion 52 of the cylindrical hollow material 50 that becomes the use surface A of the sleeve roll 30 is the same as described above. Is partially forged along the circumferential direction.

  By surface forging as described above, the carbides and dendrites crystallized by centrifugal casting in the casting process are broken down and refined, and in the axial direction z with respect to the outer peripheral portion 52 of the cylindrical hollow material 50, for example. Plastic working can be performed to a depth of 20 to 50 mm. Thereby, the strength, heat crack resistance, and seizure resistance of the cylindrical hollow material 50 can be improved.

(Die forging process)
Thereafter, in the die forging step, the sleeve roll 30 is formed by die forging the cylindrical hollow material 50 that has been surface-forged using a die, for example, by a press machine (not shown). Specifically, as shown in FIG. 2D, only the outer peripheral portion 52 of the cylindrical hollow material 50 is removed from the cylindrical hollow material 50 by using a mold 70 having a shape corresponding to the sleeve shape of the sleeve roll 30 as the final product. The material 50 is pressed down in the axial direction z and is partially upset and forged at once. Thereby, the cylindrical hollow material 50 is die-forged, and the sleeve roll 30 having the shape shown in FIG. 1 is formed.

  A concave portion 74 having a circular planar shape is formed at the center of the mold 70 used in the die forging process, and the diameter of the concave portion 74 is set to be equal to the outer diameter of the flange portion 34 of the sleeve roll 30 shown in FIG. Equivalent to. By using such a mold 70, as shown in FIG. 2D, only the outer peripheral portion 52 of the cylindrical hollow material 50 is die-forged, and the sleeve roll 30 having the flange portion 34 can be formed. Through the die forging process as described above, the forging effect of the cylindrical hollow material 50 can be obtained by near net shape molding close to the product shape.

  Here, in order to sufficiently destroy the carbides and segregation and improve the material strength by imparting a forging effect to the porous structure, the forging ratio (cross-sectional area ratio) in the die forging of the cylindrical hollow material 50 is used. Needs to be 1.5 or more. On the other hand, when the training ratio exceeds 3, the strength improvement rate due to the training effect decreases, and increasing the training ratio greatly affects the cost. Therefore, it is preferable to set the upper limit of the training ratio to 3.

(Finishing process)
Finally, the cylindrical hollow material 50 die-forged as described above is subjected to forging black skin and finishing, and finally a forged sleeve roll 30 for rolling H-shaped steel as shown in FIG. 1 is manufactured. Is done. More specifically, the die-forged cylindrical hollow material 50 has a black skin that is an oxide film formed on the surface of the material by heating by die forging. Contains meat. Therefore, in the final finishing step, for example, the entire surface (inner peripheral surface, outer peripheral surface, both end surfaces) of the cylindrical hollow material 50 that has been die-forged is cut by machining to be finished to a predetermined roll size.

  Examples of the present invention will be described below. In order to confirm the operations and effects of the examples and comparative examples of the present invention, as shown in Tables 1 and 2, the test materials according to the three examples of the present invention and the six comparative examples were prepared. Various tests were conducted to measure the mechanical properties of each test material. Table 1 shows the chemical composition, presence / absence of forging, and forging ratio of each test material, and Table 2 shows the test results of the tensile test, wear test, heat crack test, and seizure test for each test material.

  In Table 1 and Table 2 above, the test No. 1, 4 and 7 represent test materials according to examples of the present invention. 2, 5 and 8 represent test materials according to Comparative Example 1, and test Nos. 3, 6 and 9 represent test materials according to Comparative Example 2.

<< Test Material Manufacturing Method >>
First, the manufacturing method of each said test materials 1-9 is demonstrated.

<Examples of the present invention> Test Nos. 1, 4, 7
While rotating a cylindrical mold having an outer diameter of 550 mm, an inner diameter of 480 mm, and a length of 600 mm at a high speed with a centrifugal casting tester, a molten metal obtained by melting each chemical component material described in Table 1 above in a frequency induction furnace, A sleeve material (corresponding to the cylindrical hollow material 50 of the above embodiment) having an outer diameter of 450 mm, a wall thickness of 100 mm, and a length of 300 mm was manufactured by injecting into the mold. Thereafter, the sleeve material was cut in a direction perpendicular to the axis to produce a sleeve material having a length of 250 mm. Further, after the in-furnace annealing is performed on the cut sleeve material, surface forging (the above-mentioned surface forging process) and die forging with the upsetting forging ratio (the above-mentioned forging process) using a 300-ton press. ). Thereafter, the sleeve material after forging was heat-treated by quenching at 1000 ° C. and tempering at 560 ° C., and the hardness was cured to around Hs75 to finally produce a test material. Thus, the Example of this invention implements both the said surface layer forging and die forging.

<Comparative Example 1> Test No. 1 in Table 1 and Table 2. 2, 5, 8
The sleeve material of the same size was manufactured by the manufacturing method similar to the Example of the said invention using the molten metal of each chemical component described in the said Table 1. FIG. Thereafter, in order to form the flange portion 34 of the sleeve roll 30 shown in FIGS. 1 and 3, the surplus portion 152 of the sleeve material 150 was removed by machining as shown in FIG. Furthermore, the same heat treatment as that of the embodiment of the present invention was applied to the sleeve material from which the surplus portion 152 was removed, and the test material according to Comparative Example 1 was manufactured. In this comparative example 1, no forging is performed.

<Comparative Example 2> Test No. 1 in Table 1 and Table 2. 3, 6, 9
The sleeve material of the same size was manufactured by the manufacturing method similar to the Example of the said invention using the molten metal of each chemical component described in the said Table 1. FIG. Thereafter, full upsetting forging (pressing the entire surface once) was performed on the sleeve material. Further, the test material according to Comparative Example 2 was manufactured by subjecting the sleeve material after forging to the same heat treatment as that of the example of the present invention. Thus, the comparative example 2 implements only die forging without performing surface layer forging.

<< Specimen sampling position >>
Next, the test piece collection position in the test material of the various sleeve rolls 30 manufactured as described above will be described. As shown in FIG. 3, the test piece collection position is a portion corresponding to the roll use surface A (circumferential direction) that is both side surfaces of the rolled portion 32 of the sleeve roll 30. From this point, various test pieces in the tensile test, wear test, and seizure test described later were sampled, and each test was performed.

<< Test method >>
Hereinafter, various test methods for the above-described test materials will be described.

<Tensile test>
A JIS No. 4 test piece was collected and subjected to a tensile test, and the tensile strength of the test piece was measured.

<Abrasion test>
The amount of wear of the test piece was measured using a hot rolling wear tester. The test conditions in this wear test are as shown in Table 3 below.

<Heat crack test>
The roll use surface A (that is, the side surface 32a of the rolling part 32 of the sleeve roll 30) including a surface forging surface is heated and maintained at 200 ° C. in a cylindrical shape of φ80 × 10 mm long, and then “the surface is 400 ° C. by induction heating. Next, the process of “heating to 200 ° C. by water cooling” was repeated 10 times, and the presence or absence of heat cracks was observed. Furthermore, if no heat crack occurs in the 10 repetitions, the heating temperature is increased by 50 ° C. in the same repeating pattern (the heating holding temperature of 200 ° C. and the cooling temperature of 200 ° C. by water cooling are , Constant), the temperature and number of occurrences of heat cracks were measured.

<Burnability test>
Mild steel was mechanically pressed against a 30 × 20 × 10 t (mm) plate of the test piece, and the degree of seizure was visually observed. The observation results are as follows.
“No seizure”: Temper color due to frictional heat is seen, but the friction surface is smooth.
“Good”: Temper color is seen and fine scratches are present on the friction surface.
“Good”: Mild steel, which is the mating material, adheres to a part of the temper collar.
“Bad”: Mild steel adheres to the entire surface of the temper collar.

<< Evaluation of test results >>
Below, the test result regarding the test material of the Example of the present invention and Comparative Examples 1 and 2 will be described.

<Comparative example 1> Test No. of Table 1 and Table 2. 2, 5, 8
None of the test materials of Comparative Example 1 was subjected to forging after centrifugal casting. Therefore, since the crystal grains of the test material of Comparative Example 1 are coarse, the tensile strength is low (average tensile strength: 809 MPa) and the wear amount is large (average wear amount: 46 mg). In the heat crack test, cracks are generated at a low temperature (400 to 450 ° C.), and in the seizure test, the test results are inferior in seizure resistance (defective or good).

<Comparative example 2> Test No. of Table 1 and Table 2. 3, 6, 9
The test materials of Comparative Example 2 were all subjected to full upsetting forging (pressing once over the entire surface) as forging after centrifugal casting. The test material of Comparative Example 2 was superior in comparison with Comparative Example 1 in which the forging was not performed at all, particularly in terms of tensile strength and wear resistance (average tensile strength; about 1128 MPa, average wear amount; About 42.7 mg).

  However, in the heat crack test, cracks are generated at a low temperature (450 to 500 ° C.), and the test results are inferior in heat crack resistance. Also, in the seizure test, there were cases where the test results (poor) were inferior in seizure resistance. The reason for this is that the test material of Comparative Example 2 was only subjected to full upsetting forging (pressing once over the entire surface) and was not subjected to surface forging as in the example of the present invention. It is judged that the carbides and dendrites crystallized by centrifugal casting, which is a process, are not sufficiently destroyed by forging.

<Examples of the present invention> Test Nos. 1, 4, 7
The test materials of the examples of the present invention all have excellent tensile strength, wear resistance, heat crack resistance, and seizure resistance as compared with Comparative Examples 1 and 2 described above.

  More specifically, first, with respect to the tensile strength, the average tensile strength of the test material of this example is 1168 MPa for homes, which is about 1.44 times that of Comparative Example 1 and about that of Comparative Example 2. The strength is 1.04 times higher. Thus, it can be seen that the test material of this example is superior in tensile strength to the test materials of Comparative Examples 1 and 2.

  Regarding the wear resistance, the average wear amount of the test material of this example is about 41.7 mg, about 90.7% compared to Comparative Example 1, and about 97.7% compared to Comparative Example 2. The amount of wear is low. Thus, it can be seen that the test material of this example is superior in wear resistance as compared with the test materials of Comparative Examples 1 and 2.

  Further, regarding the heat crack resistance, the test material of this example did not crack up to a high temperature of 600 to 650 ° C. Therefore, it can be said that the heat crack resistance is greatly improved as compared with Comparative Examples 1 and 2 in which cracks occurred at 400 to 500 ° C.

  In addition, with respect to seizure resistance, no seizure was observed in any of the test materials of this example. Thus, it can be said that the test material of this example has improved seizure resistance as compared with the test materials of Comparative Examples 1 and 2 in which poor seizure was observed.

(Practical forged sleeve roll for rolling H-shaped steel)
Next, as an embodiment of the present invention, the characteristics of a forged sleeve roll 30 for rolling H-shaped steel provided for practical use will be described.

  Test No. 1 in Table 1 was dissolved in a high frequency induction furnace. A molten metal having a chemical composition consisting of 4 was injected into a cylindrical mold rotated at high speed by a centrifugal casting tester, and a sleeve material (cylindrical hollow material 50) was produced by centrifugal casting. Further, the sleeve material was annealed in the furnace, then subjected to surface layer forging of 30 mm using a 300-ton press, and further, die forging was performed at an upsetting forging ratio of 2. Thereafter, the sleeve roll 30 formed by the forging was tempered at 1000 ° C. and tempered at 560 ° C. twice, and then finished. Thereby, the sleeve roll 30 was hardened until the hardness became around Hs75. As shown in FIG. 3, the size of the sleeve roll 30 in this case is as follows: outer diameter D = 1200 mm, height H (width of flange 34) = 400, height h (width of rolled part 32) = 200 mm. It was. After that, ultrasonic deep wounds were performed, and it was confirmed that the rolls were healthy without defects.

  The forged sleeve roll 30 for rolling H-shaped steel produced in this way was incorporated into a rolling mill for H-shaped steel and actually used for rolling the H-shaped steel 10. At present, it is continuously used for the rolling work for 4 months after the assembly, but it is used well for the rolling work without cutting the roll surfaces A and B of the sleeve roll 30.

  The forged sleeve roll 30 for rolling H-shaped steel that has been put to practical use in this way is not disclosed to the outside and is managed in a secret state, and is a known technique that denies the novelty and inventive step of the present invention. It will not be.

  In the above, the manufacturing method of the forged sleeve roll for H-shaped steel rolling concerning Embodiment and the Example of this invention, and the forged sleeve roll 30 for H-shaped steel rolling manufactured by this were demonstrated in detail.

As described above, the cylindrical hollow material made of the above-mentioned high-speed component is partially forged to produce a forged sleeve roll for rolling H-shaped steel, and by mechanically refining hard MC carbide, for example, A high-speed forged sleeve roll with improved wear resistance, heat crack resistance, seizure resistance, rough skin resistance, and toughness can be provided. Further, by subjecting only the outer peripheral portion of the cylindrical hollow material to the surface layer partial forging and die forging processes, the forging effect can be given to the use surface of the sleeve roll in a focused manner. Also,
Further, in order to form the flange portion 34 of the sleeve roll 30 shown in FIG. 1, the surplus portion 152 having a high forging effect is not mechanically removed as in the conventional method shown in FIG. In this way, the rolling part 32 was formed by partial forging, and a part having a high forging effect was left to form a roll use surface A. For this reason, roll quality can be improved significantly.

  Furthermore, unlike conventional methods in which centrifugally cast cylindrical hollow materials are forged and molded at once by die forging, a large-capacity press facility is not required, so that molding and processing costs can be reduced. Therefore, even if mold production is added, if a predetermined number of rolls are manufactured, a further cost reduction effect can be expected.

  As described above, according to the manufacturing method according to this embodiment, a high-performance roll having excellent wear resistance, heat crack resistance, seizure resistance, rough skin resistance, toughness, etc. can be easily and inexpensively obtained. Can be supplied. In addition, the improvement in roll performance also has the effect of greatly contributing to the quality improvement of rolled products such as H-shaped steel 10 and the like.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, an example of manufacturing a composite sleeve roll including an outer layer and an inner layer has been described. However, the present invention is not limited to such an example, and the present invention is not limited to this case. Is also applicable.

  The present invention is applicable to a method of manufacturing a rolling sleeve roll used for rolling a material to be rolled such as H-shaped steel.

It is sectional drawing which shows the rolling state of H-shaped steel using the forged sleeve roll for H-shaped steel rolling concerning the 1st Embodiment of this invention. It is process drawing which shows the casting process of the manufacturing method of the forged sleeve roll for H-shaped steel rolling concerning the embodiment. It is process drawing which shows the cutting process of the manufacturing method of the forged sleeve roll for H-shaped steel rolling concerning the embodiment. It is process drawing which shows the surface layer forging process of the manufacturing method of the forging sleeve roll for H-shaped steel rolling concerning the embodiment. It is process drawing which shows the die forging process of the manufacturing method of the forging sleeve roll for H-shaped steel rolling concerning the embodiment. It is the top view (a) and sectional drawing (b) which show the forge sleeve roll for H-shaped steel rolling concerning the Example of this invention. It is sectional drawing which shows the aspect which removes the surplus part of the sleeve roll for rolling in the manufacturing method of the conventional sleeve roll for rolling.

Explanation of symbols

10 H-shaped steel 12 Web 14 Flange 14a Flange inner surface 14b Flange outer surface 20 Roll shaft 30 Forged sleeve roll for H-shaped steel rolling 32 Rolled part 32a Rolled part side surface 32b Rolled part outer peripheral surface 34 buttock 50 Cylindrical hollow material 52 Cylindrical shape Peripheral portion of hollow material 62 Base 64 Base recess 66 Surface forging anvil 70 Mold 74 Mold recess A A working surface of forged sleeve roll for H-type steel rolling

Claims (5)

A method for producing a forged sleeve roll for rolling H-shaped steel, comprising:
A casting process in which a cylindrical hollow material is cast by a centrifugal casting method using a molten metal composed of a high-speed component;
A surface layer forging step of surface forging only the radially outer peripheral portion serving as the use surface of the sleeve roll in the axial direction of the cylindrical hollow material;
A die forging step of die forging only the radially outer peripheral portion serving as the use surface of the sleeve roll in the axial direction of the cylindrical hollow material after the surface layer forging;
A method for producing a forged sleeve roll for rolling H-shaped steel, comprising: The casting process includes:
Including a step of forming a composite cylindrical hollow material by centrifugally casting a molten metal made of graphite cast steel or ductile cast iron to an inner peripheral surface of a cylindrical hollow material cast with a molten metal made of the high-speed component. The manufacturing method of the forging sleeve roll for H-shaped steel rolling of Claim 1 characterized by the above-mentioned. After the casting step, the method further includes a cutting step of cutting the cast cylindrical hollow material in a direction perpendicular to the axis of the cylindrical hollow material to have a predetermined length in the axial direction,
The method for producing a forged sleeve roll for H-shaped steel rolling according to claim 1 or 2, wherein in the surface layer forging step, the cut cylindrical hollow material is surface-forged. In the surface forging process,
The H-section steel according to any one of claims 1 to 3, wherein the outer circumferential portion in the radial direction of the cylindrical hollow material is partially surface-forged in order while partially overlapping along the circumferential direction. A method for producing a forged sleeve roll for rolling. The molten metal composed of the high-speed component is mass%,
C: 1.0 to 3.5%,
Si: 0.2 to 2.4%,
Mn: 0.2 to 2.0%,
Cr: 3.0 to 10.0%,
V: 4.5 to 10.0%, and
One or more of Mo and W: 0.2 to 10.0%
Containing
The method for producing a forged sleeve roll for rolling H-shaped steel according to any one of claims 1 to 4, wherein the balance is made of Fe.

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