JPH05311334A - Hardened roll for rolling and its manufacture - Google Patents

Abstract

PURPOSE:To provide a hardened roll for rolling having high hardness and excellent in toughness, wear resistance and dimple resistance. CONSTITUTION:The objective hardened roll for rolling is formed by subjecting allay steel (the material in this invention) contg. at least one kind among, by weight, 1.6 to 2.5% C, 2 to 3% Si, 0.8 to 3% Mn, 0.5 to 3% Ni, 13 to 18% Cr, 1 to 4% Mo, 0.5 to 2.5% W, 0.9 to 3.5% V, 2 to 5% Co, <=1% Zr, 0.5 to 3% Ti, <=0.1% B, <=1% Al and <=1% Cu, and the balance Fe with inevitable impurities as well as satisfying the range of 2.4<=Mo+W+V<=10 to hardening. This roll has >=64.5 HRC hardness, and in which the hardness is increased by 5 degrees in HRC, wear resistance by 1.2 times, deflective strength showing toughness by 1.5 times and dimple resistance by >=1.2 times as well compared with a one constituted of the conventional material SKD 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quenching roll for rolling having high hardness and excellent wear resistance, and in particular, it is characterized by the precipitation of carbides in the matrix and the strengthening of the matrix by the heat treatment of high temperature tempering.
The present invention relates to a quenching roll for rolling which has a high hardness of C64.5 or more and is excellent in dent and scratch resistance.

[0002]

2. Description of the Related Art Conventionally, many quenching rolls for rolling are manufactured from SKD11 specified in JIS. This S
As a heat treatment method for the quenching roll for rolling made of KD11, after quenching from 1000 to 1050 ° C., 150 to 200
Low temperature tempering is performed at ℃. Hardness is generally about HRC61. Since SKD11 has a low composition of Si, Mn, Mo and V, an increase in hardness due to high temperature tempering cannot be expected. In addition, the hardness obtained by adding Si to SKD11 to obtain high Si has an hardness of HRC.
The limit was about 63.5 (known example, JP-A-53-1).
No. 08021). That is, the quenching temperature 1030 to 1
After quenching from 060 ° C., high temperature tempering was performed at a temperature of 500 to 550 ° C., and a method of increasing hardness by secondary curing was tried (known example, JP-A-1-201443). However, the increase in hardness due to this secondary hardening is small, and HRC6
It was about 3.5, which was insufficient to prevent dent and scratch resistance. In the above high temperature tempering, SKD11
The material to which i is added is improved in toughness but inferior in hardness and wear resistance. Scratches are formed, and rolls have a bad influence such as rough skin, and scratches are transferred to the material to be rolled, which also has a bad influence on the quality of the plate.

[0003]

Since the materials for rolling rolls according to the above-mentioned prior art cannot obtain high hardness (HRC 64.5 or more) and wear resistance, debris of the material to be rolled is caught during rolling and the surface of the roll is rolled. However, there is a problem that dents are formed on the sheet, which shortens the roll life, and there is a problem that the dents are transferred to the material to be rolled and the accuracy of the plate is deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a quenching roll for rolling which has high hardness and excellent abrasion resistance and dent and scratch resistance by high temperature tempering.

[0005]

In order to solve the problems of obtaining high hardness, wear resistance and dent and flaw resistance in a quenching roll for rolling, the present inventors have formed a carbide in addition to C. The elements Cr, Mo, W, V, Zr, and Ti were added within a range that does not adversely affect various properties of the roll. Also, in order to strengthen the base, Mn, Ni, C
Further, Si, B were added to o, Al, and Cu in order to increase hardness by secondary strengthening by high temperature tempering.

In order to obtain high hardness by high-temperature tempering, after quenching, high-temperature tempering decomposes residual austenite and precipitates solid solution carbides in the matrix by a secondary hardening phenomenon.
It was possible to increase the hardness of RC 64.5 or more. Further, immediately after quenching, high temperature tempering may be performed after holding for a certain time in a refrigerant of 0 to -176 ° C. The increase in hardness improves wear resistance and dent and scratch resistance, thus completing the present invention.

That is, the quenching roll for rolling of the present invention is
C: 1.6 to 2.5%, Si: 2 to 3%, Mn:
0.8-3%, Ni: 0.5-3%, Cr: 13-18
%, Mo: 1 to 4%, W: 0.5 to 2.5%, V: 0.9
~ 3.5%, Co: 2-5% included, Z as necessary
r: 1% or less, Ti: 0.5 to 3%, B: 0.1% or less,
Al: 1% or less, Cu: 1% or less, at least one kind or more, and the balance of Fe and inevitable impurities, and the composition is characterized by quenching.

In this quenching roll composition for rolling, it is preferable that the ratio Cr / C of the contents of Cr and C is in the range of 6-9. Further, in the composition of this quenching roll for rolling, it is preferable that the total amount of Mo, W, and V is 2.4% or more and 10% or less.

Another quenching roll for rolling of the present invention has a weight percentage of
C: 1.6 to 2.5%, Si: 2 to 3%, Mn: 0.8
~ 3%, Ni: 0.5-3%, Cr: 13-18%, M
o: 1-4%, W: 0.5-2.5%, V: 0.9-3.5
%, Co: 2 to 5%, Zr: 1% or less, Ti: 0.5
~ 3%, B: 0.1% or less, Al: 1% or less and Cu:
1% or less of at least one or more, the balance being Fe and unavoidable impurities, and Mo, W, V
It is characterized in that alloy steel having a total amount of 2.4% or more and 10% or less is welded and formed as an outer layer material on the peripheral surface of the steel core material, and is quenched. It is a so-called composite roll.

In each of the quenching rolls for rolling of the present invention, the portion of the alloy steel having the above composition has a matrix structure of martensite by heat treatment, and M ₆ C is contained in the martensite.
Type, MC type, M ₇ C ₃ type and M ₂₃ C ₆ type carbides,
In addition, it preferably has a bainite structure and a retained austenite structure and a surface hardness of HRC 64.5 or more.

The manufacturing method of the quenching roll for rolling of the present invention comprises:
C: 1.6 to 2.5%, Si: 2 to 3%, Mn:
0.8-3%, Ni: 0.5-3%, Cr: 13-18
%, Mo: 1 to 4%, W: 0.5 to 2.5%, V: 0.9
~ 3.5%, Co: 2-5%, Zr: 1% or less, T
i: 0.5 to 3%, B: 0.1% or less, Al: 1% or less, and Cu: 1% or less and at least one or more types of alloys, and the balance is Fe and inevitable impurities. Steel ingot is diffusion annealed at 1100 to 1250 ° C., 900 to 12
Hot forging is performed at 00 ° C., the hot forged steel ingot is machined into a roll material having a predetermined shape, and the roll material is 950 to 1
It is characterized by quenching at 200 ° C and high temperature tempering at 475 to 600 ° C.

Another method of manufacturing the quenching roll for rolling of the present invention is to provide C: 1.6-2.% By weight% on the outer periphery of the steel core material.
5%, Si: 2-3%, Mn: 0.8-3%, Ni: 0.0.
5 to 3%, Cr: 13 to 18%, Mo: 1 to 4%, W:
0.5-2.5%, V: 0.9-3.5%, Co: 2-5%
And Zr: 1% or less, Ti: 0.5 to 3%, B: 0.1%
Hereinafter, at least one of Al: 1% or less and Cu: 1% or less is contained, the balance is Fe and inevitable impurities, and the total amount of Mo, W, and V is 2.4% or more. In a method for manufacturing a quenching roll for rolling, in which an outer layer material having a composition of 10% or less is formed and a quenching treatment is performed, a consumable electrode made of the material having the composition is melted by an electroslag remelting method to form an outer layer portion on a core material. To prepare a roll material, and the roll material is diffusion annealed at 1100 to 1250 ° C. and machined into a predetermined shape.
It is characterized by quenching at ℃ and high temperature tempering at 475 to 600 degrees.

In each of the methods for producing a quenching roll for rolling of the present invention, a step of subjecting the quenched roll material to a subzero treatment at 0 to -176 ° C. is added,
High-temperature tempering may be performed on the sub-zero treated roll material.

As described above, after quenching from 950 to 1200 ° C. and high temperature tempering of 475 to 600 ° C., M
Since it becomes a C, M ₆ C, M ₇ C ₃ , M ₂₃ C ₆ type carbide, residual austenite and bainite metallographic structure, HR
High hardness of C64.5 or higher, wear resistance, and residual stress due to the composite mold further increase hardness, and excellent dent and scratch resistance can be obtained.

[0015]

The quenching roll for rolling of the present invention has a C:% by weight.
1.6-2.5%, Si: 2-3%, Mn: 0.8-3
%, Ni: 0.5-3%, Cr: 13-18%, Mo:
1 to 4%, W: 0.5 to 2.5%, V: 0.9 to 3.5%,
Co: 2 to 5% and, if necessary, Zr: 1% or less, T
i: 0.5-3%, B: 0.1% or less, Al: 1% or less,
Cu: 1% or less and at least one kind or more, and the balance is formed of an alloy steel having a composition of Fe and inevitable impurities. When the composition of this alloy steel was compared with that of SKD11 which has been conventionally used, the C content was increased by 0.2 to 0.3%. The amount of Cr, which is a carbide forming element, is 2 to 3
%, Mo content of 0.2-3.8%, W content of 0.5-2.5%,
The amount of V was increased to 0.7 to 2.5%. In addition, the grain size is refined and Zr that forms carbide is 1% or less, Ti: 0.5
~ 3% addition was made.

On the other hand, in order to strengthen the base, Si, M
n, Ni, Co, Al and Cu are effective, and Si improves the toughness and accident resistance because it shifts the secondary strengthening temperature to the high temperature side. B, Mn and Ni are elements that contribute to hardenability. Co is an element that contributes to softening resistance. All of the above elements work effectively by increasing hardness by secondary hardening by high temperature tempering, and further greatly improving wear resistance and toughness (heat shock resistance) and dent and flaw resistance. To do.

Further, C which is a carbide forming element is contained in the matrix.
r, Mo, W, V, Zr dissolved in M ₆ by high temperature tempering
C and MC type carbides are precipitated to increase hardness. Further, the preferable range of Mo, W, V is 2.4 ≦ Mo + W +
When V≤10, a high hardness of HRC 64.5 or more can be obtained. In addition to the MC, M ₆ C, M ₇ C ₃ type carbides, the metal structure of martensite and retained austenite improves high hardness, wear resistance and dent and scratch resistance, and its action becomes more effective. ..

Next, the reasons for limiting the components of the alloy steel according to the present invention are as follows.

C is partially dissolved in the matrix in the quenched state, and the other is combined with Mo, W, V, Zr, Cr, etc. to form a composite carbide. C is an element most sensitively affecting the properties of the quenching roll for rolling. If the amount of C is small, the hardness does not increase due to the secondary hardening. On the other hand, if the amount of C is too high, cementite is crystallized in the matrix to lower the toughness and thermal shock resistance. From the detailed study this time, when the C content is 1.6% or less, the increase in hardness is small, and when the C content is 2.5% or more, the toughness and thermal shock resistance deteriorate and it is unsuitable for rolls. The optimum range was 1.6 to 2.5%, and it was clarified that it worked sufficiently.

Si is a component that is classified as an ordinary element in steel refining and is unavoidably contained in steel to some extent. Usually, it is added only for the purpose of deoxidation, and the content is 0.4% or less. However, in high-speed tool steel, addition of Si promotes secondary hardening by tempering and improves hardness, wear resistance and toughness. Therefore, 2-3%
Is a desirable range. If it is less than 2%, the contribution of the secondary hardening is small, and if it exceeds 3%, the M ₆ C carbide becomes lumpy. Therefore, 2-3% is the optimum range.

Mn is an element that is always contained, and it is not necessary to specify it, but the amount usually added is 0.4% or less. In this study, the amount of Mn was 0.8 to 3%.
The reason is that it is an element that contributes to the improvement of hardenability and thermal shock resistance, and if it is less than 0.8%, the effect is small, and if it is more than 3%, the amount of retained austenite increases. I can't. 0.8-3% works well.

Ni is an element which makes the metal structure fine and strengthens the matrix. Further, it is an element that coexists with Cr and Mo to increase hardenability and strengthen the matrix. Also, C
Coexists with r and Mo to increase hardenability, strengthen the matrix, and improve toughness and thermal shock resistance. If it is less than 0.5%, the above properties are not exhibited, and if it exceeds 3%, austenite remains and the hardness disappears, so 0.5 to 3% is sufficient.

Cr is an element that combines with C to crystallize an M ₇ C ₃ type carbide to contribute to hardenability and wear resistance. In the composition range of the alloy steel according to the present invention, Cr / C of 6 to 9 improves the hardness and wear resistance of the steel. If Cr is 13 to 18%, it works sufficiently, but if it is less than 13%, the improvement in hardness and wear resistance is small, and if it is 18% or more, Cr becomes a huge carbide and the toughness deteriorates. Also, forging becomes difficult. The optimum range is 13-18%.

Mo partially combines with C to form an M ₆ C type carbide, and the rest forms a solid solution in the matrix to increase the hardness due to a secondary hardening phenomenon. Further, by high temperature tempering, MC type and M ₆ C type carbides are precipitated to improve hardness and wear resistance. If it is less than 1%, the hardness, wear resistance and dent and scratch resistance are poor. If it is 4% or more, Mo carbides are crystallized in a reticulated form and the toughness is lowered. The effect is exhibited when the amount is 1 to 4%. Particularly, the preferable amount is 1.6 to 4%.

Similar to Mo, W partially bonds to form an M ₆ C-type carbide, and the rest forms a solid solution in the matrix to form a dense martensite structure. Due to the secondary hardening phenomenon, M ₆ C, MC
Precipitates carbide to increase hardness and 0.5-2.5%
Works well. 2.4 ≦ Mo between Mo, W and V
There is a relationship of + W + V ≦ 10, and high hardness and wear resistance are exhibited in this range.

Ti partially forms a TiC by combining with carbon, and when used in combination with V and Cr, wear resistance and toughness are further improved. 0.5 to 3% is sufficient, and if it exceeds 3%, TiC becomes angular and deteriorates toughness. 0.5
% Or less, the effect is small.

V combines with C to form an extremely hard carbide, which increases wear resistance. If it exceeds 3.5%, grindability and melting become difficult. If it is less than 0.9%, the improvement in wear resistance will be small. The optimum range is 0.9 to 3.5% is sufficient.

Zr is a carbide- and ferrite-forming element and has a strong cleaning action and a fine grain effect. It also forms stable ZrC carbides. The optimum range is 1%. If it exceeds 1%, ZrC becomes angular and mechanical properties are deteriorated.

Co does not form a carbide and almost forms a solid solution in the matrix. Co enhances the solubility of C in Fe, increases the amount of solid solution of the carbide forming element in the matrix, and increases the hardness by high temperature tempering due to secondary hardening. However, the drawbacks tend to promote segregation of carbides and make them brittle. Further, there is a tendency that the decarburizing property is increased and the amount of retained austenite is increased. The amount of 2 to 5% works well.

Al is an element used as a deoxidizer and is a grain refining element of crystal grains, and if its amount is 1% or less, it works sufficiently. If it exceeds 1%, the castability is deteriorated.

Cu is an element that contributes to the refinement of the structure, but it causes cracks during forging. If it is 1% or less, there are few cracks.

B is an element that contributes to hardenability, and is 0.1
% Or less is sufficient. If it exceeds 0.1%, quench cracking occurs.

In addition, P and N which are inevitably contained impurities will be described. P is an element that segregates even in a small amount and causes quenching cracks and the like. Since brittleness increases remarkably, there is no particular problem if it is 0.1% or less. N
Is similar to C in that it strongly stabilizes the austenite structure. If the amount is 0.1%, there is little harm.

In the method for manufacturing a quenching roll for rolling of the present invention, a steel having sufficient strength and toughness is used as a core material, and a consumable electrode having the structure of the present invention is arranged outside the core material, and an electroslag regrind is used. By the melting method, the outer peripheral part of the core material and the consumable electrode are melted and solidified one after another to form the outer layer member, so that a healthy joint can be obtained at the boundary without defects such as non-welded parts and microcavities. Be done. Therefore, in the present invention, it becomes possible to perform heat treatment (quenching-subzero treatment-tempering) on the composite roll in which the outer layer member of the steel core material is integrated, and due to residual stress, high hardness and wear resistance,
The toughness, thermal shock resistance, and dent and scratch resistance are improved, and it is possible to manufacture a composite roll having an appropriate metal structure.

Then, a quadruple rolling mill supported by a pair of work rolls and a reinforcing roll, and a six-fold rolling mill provided with a pair of upper and lower work rolls and a reinforcing roll so that the intermediate roll can move, The quenching roll for rolling of the present invention can be used as each roll of a multi-stage rolling mill having a pair of work rolls, an intermediate roll and a reinforcing roll.

[0036]

Embodiments of the present invention will be specifically described below with reference to FIGS. [Example 1] Table 1 shows the chemical composition of alloy steel (referred to as the material of the present invention) forming the quenching roll for rolling according to the embodiment of the present invention, together with the chemical compositions of the comparative material and the conventional material.

In Table 1, the conventional material 11 is the cold die steel SKD11, which has a composition of C, Si, Mn,
Low content of Cr, Mo and V, Ni, Co, W,
Zr, Ti, B, Al and Cu are not added.

The compositions of comparative materials 8 to 10 are as follows in comparison with that of the material of the present invention. Comparative material 8 is S more
The amount of i, Mn, Mo and Co is low. The comparative material 9 has a higher C content and a lower Mn, V, and Co content than the inventive material. Comparative material 1
0 is lower in the amount of C, Ni, Cr and Co than the material of the present invention, and S
The composition has a high amount of i, Mn, W, and V and further contains Zr.

One of the characteristics of the materials 1 to 7 of the present invention is one of Cr and C.
Is in the range of 6 to 9, and in order to increase the hardness by secondary hardening in high temperature tempering, M
The total amount of o, W and V was set in the range of 2.4 ≦ Mo + W + V ≦ 10. Furthermore, the amount of Si was set to 2 to 3% to increase hardness by high temperature tempering.

The samples of the present invention material, comparative material and conventional material are
It was melted in a high-frequency melting furnace and cast into a mold to produce a steel ingot.
After casting, the steel ingot is held at 880 ° C for 10 hours, then 70
After holding at 0 ° C. for 5 hours, annealing was performed by furnace cooling, and test pieces were taken from the steel ingot to examine heat treatment hardness, wear resistance, bending resistance, thermal shock resistance and dent flaw resistance. ..

[0041]

[Table 1]

FIG. 1 shows the relationship between the number of tempers and the hardness of one of the present invention materials and a conventional material. Heat treatment hardness is 15mm
It measured with the Rockwell hardness tester (HRC) using the corner test piece. Conventional material 11 was heated at 1050 ° C. for 1 h and oil-cooled (hereinafter, such heat treatment is described as 1050 ° C. × 1 h → oil-cooled), then 500 ° C. × 1 h → air-cooled tempering was repeated 5 times, and then hardness was increased. Was measured. The hardness shows the value of HRC60.8. Inventive material 2 was subjected to tempering of 1075 ° C. × 1 h → oil cooling, 500 ° C. × 1 h → air cooling five times, and then the hardness was measured. The hardness was HRC66.2. Further, the present invention material 2 was subjected to sub-zero treatment of 1075 ° C. × 0.5 h → air cooling, and then immediately to −70 ° C. × 30 min → air cooling, and then 5
High temperature tempering of 00 ° C. × 1 h → air cooling was performed 5 times. As a result, a hardness of HRC64.5 or higher was obtained, and the conventional material 11
It is clear that it shows higher hardness than.

FIG. 2 is a graph showing the relationship between the total amount of Mo, W and V and hardness in each sample. Heat treatment hardness is 15m
It measured with the Rockwell hardness tester (HRC) using the square test piece. Regarding heat treatment, conventional material 11 is 1050 ° C
× 1h → Oil cooling, 500 ℃ × 1h → Air-cooled tempering 5
The present invention materials 1 to 7 and the comparative material 8 are repeated.
10 to 1075 ℃ x 1h → after oil cooling, 500 ℃
The tempering of × 1 h → air cooling was repeated 5 times, and the hardness of each sample was measured. Conventional material 11 shows a value of HRC60.8, and comparative materials 8-10 are all HRC61-61.4.
Only the hardness of can be obtained. On the other hand, it was revealed that the materials 1 to 7 according to the present invention can obtain a high hardness of HRC 65.0 to 66.5.

FIG. 3 is a graph showing the relationship between the total amount of Mo, W and V and the anti-segregation force in each sample. The toughness indicated by the segregation force was evaluated by a static bending test. The test piece had a thickness of 4 mm, a width of 5 mm, and a length of 55 mm, and a center single point load bending jig was used as an inter-fulcrum distance of 40 mm for testing. In the heat treatment of the test piece, similarly to the above, the conventional material 11 was tempered by 1050 ° C. × 1 h → oil cooling and 500 ° C. × 1 h → air cooling five times. Inventive materials 1 to 7 and comparative materials 8 to 10 are 1075 ° C. × 1 h → after oil cooling, 500 ° C. ×
The tempering of 1 h → air cooling was repeated 5 times. As is clear from FIG. 3, all of the present invention materials 1 to 7 have high toughness values and are toughness 1.5 times or more that of the conventional material.

FIG. 4 is a graph showing the relationship between the total amount of Mo, W and V and the thermal shock resistance of each sample. In the thermal shock resistance test, the test piece was allowed to move up and down in an electric furnace, heated in an electric furnace at 500 ° C. for 3 minutes, immersed in a water tank installed below it, cooled for 2 minutes, and then subjected to a heating / cooling cycle. 200
Repeated several times. Test piece size is 20mmφ × 20mm
The heat treatment of the test piece was performed using the conventional material 11 and the invention materials 1 to 7
And the comparative materials 8 to 10 are the same as those in the hardness test and the bending test, respectively.

Conventional material 11 has a total crack length of 29.8 m
m, and the comparative materials 8 to 10 are 25.8 to 27.8 mm. On the other hand, the total crack length of the present invention materials 1 to 7 is 22 to 23.8 mm and the total crack length is short, and the thermal shock resistance is excellent. It has been clarified that is strengthened and has excellent toughness.

FIG. 5 is a graph showing the relationship between the total amount of Mo, W and V and the wear resistance of each sample. In the abrasion test, an emery paper was put on a turntable with a diameter of 200 mm and rotating at a rotation speed of 600 rpm, and a diameter of 18 m was placed on it.
This is a test method in which a test piece of mφ is pressed with a load of 800 g and is worn for 2 minutes and 20 seconds. The difference in weight of the test pieces before and after the test was used as the amount of wear, and the wear resistance of each sample was compared. The heat treatment of the test piece was performed using the conventional material 11 and the invention materials 1 to 1.
7 and the comparative materials 8 to 10 were the same as those in the hardness test and the bending test.

As is apparent from FIG. 5, the wear amount of the conventional material 11 shows a value of 178 mg, and that of the comparative materials 8 to 10 is 1.
A value of 55 to 158 mg is shown. On the other hand, the materials 1 to 7 of the present invention have a small wear loss of 132 to 137 mg, and it is clear that they all have excellent wear resistance.

FIG. 6 is a graph showing the relationship between the total amount of Mo, W and V and the resistance to dents and scratches in each sample. The Brennel hardness tester was used to evaluate the dent and scratch resistance, and the load was 3000 kg.
It was carried out by pressing for 30 seconds and measuring the diameter of the depression. The size of the test piece used was 20 mmφ × 20 mml. The heat treatment of the test piece was performed on the conventional material 11, the present invention materials 1 to 7 and the comparative materials 8 to 10 in the same manner as in the hardness test and the bending test.

As shown in FIG. 6, the diameter of the dent shows a large value of 2.55 mm in the conventional material 11 and the comparative material 8 to
10 is 2.43 to 2.55 mm, but the present invention materials 1 to 7
Clearly has a small recess diameter of 2.0 to 2.35 mm and exhibits excellent dent resistance.

[Example 2] Using the present invention material 6 and the conventional material 11, work rolls of a multi-stage rolling mill were produced. Table 2 shows the compositions of the present material 3 and the conventional material 11.

[0052]

[Table 2]

FIG. 7 shows the roll structure of the multi-stage rolling mill. In the figure, 5 is a rolled material, 1 and 1'are work rolls for rolling the rolled material 5, 2 and 2'are first intermediate rolls in contact with the work rolls, and 3 and 3'are first intermediate rolls. 2,
2'is a second intermediate roll, 4'is a backup bearing roll which is in contact with the second intermediate roll 3, 3 ', and 6'is a roll housing for supporting the various rolls.

The work roll is produced by the following steps: 880 ° C. × 10 h → 770 ° C. × 5 h → furnace-cooled two-stage annealing of a steel ingot melted in a high-frequency melting furnace, then 1150 ° C. × 15 h → furnace-cooled diffusion annealing. Was done. After the diffusion annealing, hot forging was performed. 1
80mm diameter x length 1 in the temperature range of 000 to 1150 ° C
Forged to 200 mm. After forging, it was annealed and machined to a diameter of 70 mm and a length of 1000 mm. As a result of inspection by magnetic flaw detection and dyeing test, it was found to be defect-free.

In the heat treatment, the conventional material 11 was quenched from 1050 ° C. and then tempered at 500 ° C. Inventive material 3 is 1
After quenching from 075 ° C, high temperature tempering at 500 ° C was repeated 5 times. As a result, the strength of the roll surface is Hs92 (H
A high strength of RC65.9) was obtained.

Example 3 Working rolls of a quadruple rolling mill were produced using the present invention material 2 and the conventional material 11. Table 3 shows the compositions of the present material 2 and the conventional material 11.

[0057]

[Table 3]

FIG. 8 shows the roll configuration of the quadruple rolling mill. In the figure, a rolled material 5 is sandwiched and directly rolled, and a pair of lower work rolls 1 and 1'is backed up by reinforcing rolls 7 and 7 '.

Steel ingots for work rolls 1 and 1'were produced using an electroslag remelting apparatus. That is, diameter 320
mm inside, water-cooled mold with height 730mm, diameter 200m
A steel core material (bearing steel) having a height of 1300 mm and a height of 1300 mm was installed on the start board, and a cylindrical consumable electrode having an inner diameter of 235 mm and an outer diameter of 280 mm made of the material 2 of the present invention was used as an outer layer material welded to the outer periphery of the core material. A flux was inserted and melted to produce a steel ingot. In order to investigate the weldability of the molten steel ingot, the soundness of the joint boundary portion between the core material and the outer layer material was checked by an ultrasonic flaw detection test. As a result, it was confirmed that the outer layer portion was completely welded and integrated with the core material. Further, the steel ingot after melting was cut into a cross-sectional shape, and the appearance by a macrostructure was observed. From the macrostructure, it was confirmed that internal defects such as microcavities did not occur at the joint. Therefore, it is clear that peeling from the joint boundary portion does not occur even if high speed rolling, high pressure rolling and high load rolling are performed.

The steel ingot after melting was subjected to diffusion annealing of 1150 ° C. × 15 h → furnace cooling, and then 300 mm in diameter as a roll material.
Machining was carried out to mm x length 700 mm. A roll material using the conventional material 11 as the outer layer material was produced in the same manner as in the case of the present invention material 2. Then, each roll material was heat-treated. Roll material having an outer layer of conventional material 11 is 1050 ° C.
After quenching, tempering was performed 5 times at 500 ° C. × 1 h → air cooling. The roll material used as the outer layer material of the material 2 of the present invention is 10
After quenching from 75 ° C., tempering of 500 ° C. × 1 h → air cooling was repeated 5 times.

After quenching and tempering, the roll material having the outer layer of the conventional material 11 has a roll surface hardness of Hs82 (HRC6).
It was 0.8). On the other hand, the roll material having the outer layer of the present invention material 2 has a roll surface hardness of Hs93 (HRC66.
It was confirmed in 2) that the work roll had a sufficiently high hardness, no cracking occurred during heat treatment, and that the work roll was an excellent material for the quadruple rolling mill.

[0062]

According to the present invention, the quenching roll for rolling is
C: 1.6-2.5%, Si: 2-3%, Mn:
0.8-3%, Ni: 0.5-3%, Cr: 13-18
%, Mo: 1 to 4%, W: 0.5 to 2.5%, V: 0.9
~ 3.5%, Co: 2-5%, Zr1% or less, Ti0.
5-3%, B 0.1% or less, Al 1% or less and Cu 1%
Formed from an alloy steel containing at least one of the following:
Especially, the hardness is HRC 64. by quenching and tempering within the range of 2.4≤Mo + W + V≤10.
With a hardness of 5 or more, hardness is increased by 5 degrees in HRC, wear resistance is improved 1.2 times or more, and toughness is also improved 1.5 times as high as that of the conventional material SKD11. The dent and scratch resistance was also improved 1.2 times or more.

Therefore, by using the quenching roll for rolling of the present invention as a work roll of a quadruple type or multi-stage rolling mill,
There is an effect that the roll life can be extended from the viewpoint of wear resistance, and the surface accuracy and dimensional accuracy of the rolled plate can be improved from the viewpoint of dent and flaw resistance.

The manufacturing method of the quenching roll for rolling is the electroslag remelting method. If the alloy steel having the above composition is welded and integrated as the outer layer material of the steel core material, the core material and the outer layer material are joined together. Micro-gaviness does not occur in the portion, defects such as cracking due to heat treatment can be prevented, material costs can be reduced, and a rolling roll excellent in wear resistance and dent and flaw resistance can be manufactured.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of tempers and the hardness of one of the materials of the present invention used for a quenching roll for rolling and a conventional material.

FIG. 2 is a graph showing the relationship between the total amount of Mo, W and V and hardness of the material of the present invention.

FIG. 3 is a graph showing the relationship between the total amount of Mo, W and V and the anti-segregation force of the material of the present invention.

FIG. 4 is a graph showing the relationship between the total amount of Mo, W and V and the thermal shock resistance of the material of the present invention.

FIG. 5 is a graph showing the relationship between the total amount of Mo, W and V and the wear resistance of the material of the present invention.

FIG. 6 is a graph showing the relationship between the total amount of Mo, W, and V of the material of the present invention and the dent defect resistance.

FIG. 7 is a schematic sectional view showing a roll configuration of a multi-stage rolling mill.

FIG. 8 is a schematic sectional view showing a roll configuration of a quadruple rolling mill.

[Explanation of symbols]

 1, 1'Work roll 2, 2'Intermediate roll 3, 3'Intermediate roll 4, 4'Backup bearing 5 Rolled material 6, 6'Housing 7, 7'Backup roll

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C22C 38/52 38/58 (72) Inventor Ken Yasuda 4026 Kuji Town, Hitachi City, Ibaraki Japan Hitachi Research Laboratory (72) Inventor Hideyo Kodama 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Institute Ltd. (72) Inventor Osamu Shitamura 832, Horiguchi, Katsuta City, Ibaraki Hitachi Co., Ltd. Within the Material Processing Division (72) Inventor Rokugo Sagawa 2-832, Horiguchi, Katsuta City, Ibaraki Prefecture Hitachi Material Processing Division

Claims (14)

[Claims] 1. C: 1.6 to 2.5% by weight, Si: 2
~ 3%, Mn: 0.8-3%, Ni: 0.5-3%, C
r: 13-18%, Mo: 1-4%, W: 0.5-2.5
%, V: 0.9 to 3.5%, Co: 2 to 5%, and Zr: 1
% Or less, Ti: 0.5 to 3%, B: 0.1% or less, Al:
A quenching roll for rolling, characterized by containing 1% or less and at least one or more of Cu: 1% or less, the balance being formed from an alloy steel composed of Fe and unavoidable impurities and quenching. 2. C: 1.6 to 2.5% by weight, Si: 2
~ 3%, Mn: 0.8-3%, Ni: 0.5-3%, C
r: 13-18%, Mo: 1-4%, W: 0.5-2.5
%, V: 0.9 to 3.5%, Co: 2 to 5%, and Zr: 1
% Or less, Ti: 0.5 to 3%, B: 0.1% or less, Al:
1% or less and Cu: at least one or more of 1% or less, the balance consisting of Fe and unavoidable impurities, and the Cr / C content ratio Cr / C is in the range of 6 to 9. A quenching roll for rolling, which is formed from a certain alloy steel and is quenched. 3. C: 1.6 to 2.5% by weight, Si: 2
~ 3%, Mn: 0.8-3%, Ni: 0.5-3%, C
r: 13-18%, Mo: 1-4%, W: 0.5-2.5
%, V: 0.9 to 3.5%, Co: 2 to 5%, and Zr: 1
% Or less, Ti: 0.5 to 3%, B: 0.1% or less, Al:
1% or less and Cu: at least one or more of 1% or less, the balance consisting of Fe and inevitable impurities, and the total amount of Mo, W, V is 2.4% or more and 10% or less. A quenching roll for rolling, which is formed from a certain alloy steel and is quenched. 4. The martensite is used as the matrix structure, and M ₆ C type, MC type, M ₇ C ₃ type and M ₂₃ C _{6 are} contained in the martensite.
The quenching roll for rolling according to claim 1, wherein the quenching roll contains a type carbide, and further contains a bainite structure and a retained austenite structure. 5. The quenching roll for rolling according to claim 4, wherein the surface hardness is HRC 64.5 or more. 6. C: 1.6 to 2.5% by weight, Si: 2
~ 3%, Mn: 0.8-3%, Ni: 0.5-3%, C
r: 13-18%, Mo: 1-4%, W: 0.5-2.5
%, V: 0.9 to 3.5%, Co: 2 to 5%, and Zr: 1
% Or less, Ti: 0.5 to 3%, B: 0.1% or less, Al:
1% or less and Cu: at least one or more of 1% or less, the balance consisting of Fe and unavoidable impurities, and 10% if the total amount of Mo, W, and V is 2.4% or more.
A quenching roll for rolling, characterized in that the following alloy steel is welded and formed as an outer layer material on the peripheral surface of a steel core material, and then quenched. 7. A matrix structure of the outer layer material is martensite, and the martensite contains M ₆ C type, MC type, M ₇ C ₃ type and M ₂₃ C ₆ type carbides, and other bainite structure remains. The quenching roll for rolling according to claim 6, further comprising an austenite structure. 8. The quenching for rolling according to claim 6 or 7, wherein the surface hardness of the outer layer material is HRC 64.5 or more and the strength of the core material is 80 kg / mm ^2. roll. 9. A quadruple rolling mill comprising the quenching roll for rolling according to claim 1 as a work roll. 10. A six-fold rolling mill comprising the quenching roll for rolling according to any one of claims 1 to 8 as a work roll and an intermediate roll. 11. A multi-stage rolling mill comprising the quenching roll for rolling according to claim 1 as a work roll and an intermediate roll. 12. C: 1.6 to 2.5% by weight, Si:
2-3%, Mn: 0.8-3%, Ni: 0.5-3%, C
r: 13-18%, Mo: 1-4%, W: 0.5-2.5
%, V: 0.9 to 3.5%, Co: 2 to 5%, and Zr: 1
% Or less, Ti: 0.5 to 3%, B: 0.1% or less, Al:
1% or less and Cu: at least one or more of 1% or less, the balance consisting of Fe and inevitable impurities, and the total amount of Mo, W, V is 2.4% or more and 10% or less. A steel ingot of a certain alloy steel is diffusion annealed at 1100 to 1250 ° C., hot forged at 900 to 1200 ° C., machined into a roll material having a predetermined shape, and the machined roll material is
A method for producing a quenching roll for rolling, comprising quenching at 50 to 1200 ° C. and high temperature tempering at 475 to 600 degrees. 13. A steel core material having a C: weight% on the outer periphery thereof.
1.6-2.5%, Si: 2-3%, Mn: 0.8-3
%, Ni: 0.5-3%, Cr: 13-18%, Mo:
1 to 4%, W: 0.5 to 2.5%, V: 0.9 to 3.5%,
Co: 2-5%, Zr: 1% or less, Ti: 0.5-3
%, B: 0.1% or less, Al: 1% or less and Cu: 1%
And at least one of the following, with the balance being F
In the method for producing a quenching roll for rolling, which comprises an outer layer material having a composition in which the total amount of Mo, W, and V is 2.4% or more and 10% or less, and which is formed by quenching treatment, A consumable electrode made of the material having the above composition is melted by an electroslag remelting method, and a roll material is manufactured by overlaying the core material as an outer layer portion, and the manufactured roll material is diffusion annealed at 1100 to 1250 ° C. , Machined into a predetermined shape, and machined the roll material 950-12
A method for manufacturing a quenching roll for rolling, comprising quenching at 00 ° C. and high-temperature tempering at 475 to 600 degrees. 14. The method for manufacturing a quenching roll for rolling according to claim 13 or 14, wherein the temperature is from 950 to 1200 ° C.
0 between quenching and high temperature tempering at 475-600 degrees
~ A method for manufacturing a quenching roll for rolling, characterized by adding a step of sub-zero treatment at -176C.