JP3230899B2 - Heat treatment of graphite-containing high-speed cast iron and composite rolls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed cast iron material having graphite and a heat treatment method for a composite roll having an outer layer formed of the cast iron material.

[0002]

2. Description of the Related Art As a high wear-resistant cast iron material for casting, a high-speed cast iron material having the following chemical composition (wt%) is known as disclosed in Japanese Patent Application Laid-Open No. 4-176840. C: 1.0 to 3.0%, Si: 0.1 to 2.0%, Mn:
0.1 to 2.0%, Cr: 3.0 to 10.0%, Mo: 0.1 to 6.
0%, W: 1.5 to 10.0%, total of one or two of V and Nb: 3.0 to 10.0%, balance substantially Fe The high-speed cast iron material containing Mo, W, and V has high-temperature properties. Excellent wear resistance and skin resistance as a roll material for hot rolling as it has excellent hardness and carbides such as VC, M ₂ C and M ₆ C in the structure. are doing. Therefore, it is used as an outer layer and an inner layer made of a tough material welded to the inner surface thereof, or as an outer layer material of a composite roll having an intermediate layer welded therebetween.

[0003]

However, the conventional high-speed steel cast iron material has a large coefficient of friction, and as a result, there are problems such as an increase in rolling load, an imbalance in sheet passing property, and heat generation. Further, when an excessive load is applied to the roll during rolling, there is a problem that microcracks generated on the roll surface easily propagate into the outer layer thereafter, and in severe cases, the outer layer is broken. In addition, the threadability refers to the ease with which the rolled sheet separates from the roll surface.If it is poor, the rolled sheet adheres to the roll surface, hinders smooth running and meanders. Surface damage such as wrinkles and wrinkles occurs.

[0004] Accordingly, the applicant has filed Japanese Patent Application No. 5-45426.
In No. 2, a high-speed cast iron material having a low coefficient of friction and hardly causing cracks to develop, and a composite roll having the cast iron material in the outer layer have been proposed. An object of the present invention is to provide a suitable heat treatment method for the above-mentioned high-speed cast iron material and a composite roll having the cast iron material in an outer layer.

[0005]

According to the heat treatment method of the present invention, the chemical composition is represented by wt%, C: 1.8 to 3.6%, Si: 1.0 to 1.0%.
3.5%, Mn: 0.1 to 2.0%, Ni: 0.5 to 10.0%,
Cr: 2.0 to 10%, Mo: 0.1 to 10%, W: 0.
1 to 10%, V, Nb: 1.0 to 1 or 2 kinds in total
An outer layer is formed of a high-speed cast iron material essentially containing 10%, and the balance is substantially graphite made of Fe, or an outer layer is formed by the high-speed cast iron material, and an inner layer of a steel material is provided inside the outer layer. 950 to the outer layer of the composite roll
After austenitizing heat treatment at ~ 1150 ° C, 600
After quenching and heat-treating at a cooling rate of 200 ° C./hr or more up to ℃, tempering heat treatment is performed at a temperature of 460-590 ° C.

[0006]

The high-speed cast iron material of the present invention is made of Cr, Mo, W,
Due to the presence of a high-hardness composite carbide in which Nb, V, Fe and C are bonded to each other in the matrix, and by strengthening the matrix with Co, the hardness at room temperature and high temperature is improved, and the wear resistance is dramatically improved. I do. More particularly, C, Si, Ni
Is defined in a specific range, so that about 0.1 to 7.0% of the area ratio of graphite crystallizes and precipitates in the structure during the solidification process, and by the action of this graphite, the impact load can be alleviated and cracks can be propagated. Is prevented, and the friction coefficient is reduced and seizure resistance is improved.

By using a high-speed cast iron material having the above graphite as an outer layer material of a composite roll, it is possible to exhibit the excellent properties of the material during rolling, to reduce rolling load and frictional heat, and to improve sheet passability. And a roll for rolling that can suppress the progress of cracks can be provided. Since the rolling roll has good seizure resistance due to the action of graphite, it is also suitable as a roll for cold rolling.

The austenitizing heat treatment at 950 to 1150 ° C. is applied to the high-speed cast iron material or the outer layer formed of the cast iron material.
After quenching heat treatment at a cooling rate of at least
By performing a tempering heat treatment at a temperature of up to 590 ° C., fine graphite can be positively precipitated in the structure even in a composition having a small amount of graphite generated in the solidification process, and the action of the graphite is strengthened and promoted. can do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the chemical composition of the graphite-containing high-speed cast iron material of the present invention will be described. Hereinafter, all the units of the components are wt%. C: 1.8 to 3.6% C mainly combines with Fe and Cr to form an M ₇ C ₃ type high-hardness composite carbide, and Cr, Mo, V, N
Combined with b and W, it also forms high hardness composite carbides such as MC type, M ₆ C type and M ₂ C type. Further, by the action of Si, which is a graphitization promoting element to be described later, and by heat treatment, fine graphite is crystallized and precipitated in the structure. If it is less than 1.8%, the amount of carbides decreases and graphite almost disappears.
If the content exceeds 3.6%, the amounts of carbide and graphite become excessive and the material becomes brittle.

Si: 2.29 to 3.5% Si is an element necessary for ensuring the fluidity of the molten metal and crystallizing and precipitating graphite. If the content is less than 1.0%, such an effect is insufficient , but the lower limit is 2.29%. Limited. Meanwhile, 3.
If it exceeds 5%, the graphite becomes excessive so that the area ratio exceeds 7%, the friction starting from graphite becomes remarkable, and the wear resistance deteriorates. In order to promote the crystallization of graphite, it is preferable that the amount of Si before casting is set to be lower than the above component range, inoculation is performed at the time of casting, and the content is adjusted within the above range with the components of the final product.

Mn: 0.1 to 2.0% Mn is an element that increases the hardening ability and combines with S to form MnS and prevent embrittlement due to S. At the same time, about 0.1% is inevitably contained from the raw materials used. Is done. But 2.0
%, It is not preferable because toughness is reduced. Ni: 0.5 to 10.0% Ni is added for the purpose of improving the base structure and crystallizing and precipitating graphite. If it is less than 0.5%, the amount of graphite is too small.
If it exceeds 0.0%, graphite becomes excessive as in the case of Si,
In addition, retained austenite increases, and it becomes difficult to form a tough structure even by a subsequent heat treatment, and wear resistance deteriorates.

Cr: 2.0-10% Cr combines with C together with Fe, Mo, V, Nb, and W,
It forms high hardness composite carbides and contributes to improvement of wear resistance at high temperatures. In addition, a part of the alloy dissolves in the matrix to improve quenchability and wear resistance. If the content is less than 2.0%, these effects are small. On the other hand, if the content exceeds 10%, the toughness is deteriorated, which is not preferable.

Mo: 0.1-10% Mo is easily bonded to C together with Fe, Cr, V, Nb and W.
And mainly M₇C _ThreeType M₆C type, M_TwoC-type composite coal
Forms a carbide and increases the hardness at normal and high temperatures to improve wear resistance
Contribute to improvement. Mo is less effective than W
Demonstrate the fruits. At this time, the effect will be excessive if it is less than 0.1%.
If it exceeds 10%, the toughness will decrease.
I don't.

W: 0.1 to 10% W is also easily combined with C together with Fe, Cr, Mo, V, and Nb to form a composite carbide, and contributes to an increase in hardness at normal and high temperatures to improve wear resistance. I do. If it is less than 0.1%, the desired wear resistance cannot be obtained, while if it exceeds 10.0%, the toughness decreases and the heat crack resistance deteriorates. In addition, at the time of centrifugal casting, macro segregation is easily generated. Therefore, the content is set to 10.0% or less.

V, Nb: 1.0 to 10 in total of one or two kinds
% V easily bonds to C together with Fe, Cr, Mo, and W like Nb, and mainly forms an MC-type composite carbide, and contributes to improving the wear resistance by increasing the normal temperature and high temperature hardness.
Further, since the MC-type composite carbide is formed in a branch shape in the thickness direction, it suppresses plastic deformation of the matrix and contributes to improvement of mechanical properties and crack resistance. Such effects are unlikely to appear unless one or more of the two are added and 1.0% or more is added. However, if the addition amount exceeds 10%, the toughness is reduced, and macrosegregation is easily generated during centrifugal casting.

[0016] The high-speed cast iron material according to the present invention essentially contains the above alloy components, and the balance is formed of Fe and unavoidable impurities. Although P and S are inevitably mixed in from the raw material, it is desirable that the P and S contents be small because they make the material brittle. It is better to keep P: 0.2% or less and S: 0.1% or less. The cast iron material of the present invention essentially contains the alloy component.Here, `` essentially '' refers to a content of an element capable of improving properties without impairing the action and effect of the high-speed cast iron. For example, if necessary, Co: 0.5 to 10.0%, or / and one or more of Al, Ti, and Zr in the following composition range, or / and B: 0.01 0.50.50%.

Co: 0.5-10.0% Co has a great effect in improving the base. Co is C
It has a special action of suppressing the diffusion of carbides, has the effect of increasing the toughness by forming a solid solution in the matrix irrespective of the formation of carbides, and improving the high-temperature hardness and wear resistance. Further, Co increases the solid solution amount of the carbide-forming element in austenite, so that the hardness of the matrix and the tempering resistance increase. In order to expect these effects, the content must be 0.5% or more.
%, The effect is saturated and it is an expensive element. Therefore, the content is set to 0.5 to 10.0%. When casting a high alloy cast iron material by centrifugal casting to produce a composite roll, the distribution of carbides is likely to be non-uniform, and it is necessary to optimize the casting conditions. In the case of such a high alloy material, Co is dissolved in the matrix irrespective of the formation of carbide as described above, so that the above-mentioned excellent effects can be expected without increasing the non-uniformity of carbide.

Al, Ti, Zr: 0.01 to 0.50% each Al, Ti, and Zr form oxides in the molten metal, reduce the oxygen content in the molten metal, improve the soundness of products, and form Since the formed oxide acts as a crystal nucleus, it is effective in refining the solidification structure. If it is less than 0.01%, this effect is not sufficient. On the other hand, if it exceeds 0.50%, it remains as inclusions and is not preferable. In addition, Al, Ti,
In the present invention, Zr is mainly added for the purpose of improving wear resistance by making the casting structure finer, and is not simply added for the purpose of degassing.

B: 0.01 to 0.50% B combines with oxygen in the molten metal to exhibit a deoxidizing effect. In addition, the effect of refining the solidification structure with the generated oxide as the nucleus,
And the effect of increasing the hardenability by B dissolved in the matrix. In the case of a casting having a large mass such as a rolling roll, it may be difficult to increase the cooling temperature, but it is easy to obtain a quenched structure due to an increase in hardenability. If it is less than 0.01, such an effect is not sufficient, while if it exceeds 0.50%, the material becomes brittle, which is not preferable.

The cast iron material of the present invention is used as an outer layer material of a two-layer composite roll in which an outer layer and a solid inner layer or a cylindrical inner layer are welded, or a three-layer composite roll in which an intermediate layer is cast between the outer layer and the inner layer. It is preferably used. As the inner layer material, a steel material for casting having high toughness such as high-grade cast iron, ductile cast iron, graphite steel, cast steel or the like is used. In particular, the former three which are graphite crystallization materials are preferred. This is because, in combination with the presence of graphite in the outer layer, the heat conductivity and thus the heat dissipation are excellent, and thermal deformation of the roll during rolling can be prevented. Preferred composition examples (wt%) of high-grade cast iron, ductile cast iron, and graphite steel are shown. The composition of the molten metal before casting is determined so as to have the above composition after welding. (1) High-grade cast iron C: 2.5 to 4.0%, Si: 0.8 to 2.5%, Mn:
0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less,
Mo: 2.0% or less, W, V, Nb: 4% or less in total, Remainder: Co and substantially Fe mixed from an outer layer or an intermediate layer described below. When the outer layer contains Al, Ti, Zr, The element is also mixed into the inner layer from the outer layer or through the intermediate layer. (2) Ductile cast iron C: 2.5 to 4.0%, Si: 1.3 to 3.5%, Mn:
0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less,
Mo: 2.0% or less, W, V, Nb: 4% or less in total,
Mg: 0.02 to 0.1%, balance: Co and substantially Fe (3) graphite steel mixed from the outer layer or intermediate layer C: 1.0 to 2.3%, Si: 0.5 to 3.0%, Mn:
0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less,
Mo: 2.0% or less, W, V, Nb: 4.0% or less in total, Remainder: Co and substantially Fe mixed from the outer layer or the intermediate layer The intermediate layer reduces the alloy component of the outer layer from mixing into the inner layer. It is formed as one of the purposes, but it itself needs to have a strength of about 30 kg / mm ² or more. If the strength is insufficient, the boundary between the outer layer and the intermediate layer breaks, and the outer layer peels off. Therefore, the intermediate layer needs to be made of a material having high strength even if a large amount of alloy components are mixed in from the outer layer. For this reason, an adamite material is suitable as the intermediate layer material. A preferred composition example (wt%) of the adamite material is shown below. The composition of the molten metal before casting is determined so as to have the above composition after welding. The structure of the adamite material does not usually include graphite, but in the present invention, a structure in which graphite is crystallized and precipitated may be used.

C: 1.0 to 2.5% Si: 0.2 to 3.0% Mn: 0.2 to 1.5% Ni: 4.0% or less Cr, Mo: 4.0% or less W, V, Nb, Al, Ti, Zr, B: Total 12% or less In addition to the above, the components of the intermediate layer material are substantially formed of Fe. When Co is contained in the outer layer, Co is inevitably mixed in from the outer layer, but is not particularly limited because it does not deteriorate the material of the intermediate layer.

1.0 to 2.5 between the outer layer and the inner layer (axial portion)
When the intermediate layer of% C is provided, the harmful alloy element in the inner layer can be greatly suppressed from being directly mixed into the inner layer from the outer layer during welding. Even if heated to over ℃, the heat transfer to the inner layer is performed through the intermediate layer, so the temperature of the inner layer can be easily suppressed to 1100 ℃ or less, even when using a cast iron type as the inner layer material, Melting of the inner layer can be prevented.

As a method of casting a composite roll, as is well known, an outer layer and, if necessary, an intermediate layer are cast by a centrifugal die casting method, and then a solid inner layer is statically cast therein.
When a sleeve-shaped roll is cast, it is a matter of course that the inner layer may be cast by centrifugal force. In the centrifugal casting method, the rotation axis of the cylindrical mold is horizontal horizontal type, diagonal inclined type,
Various vertical vertical methods can be applied.

The high-speed cast iron material having graphite of the present invention comprises:
After casting the cast iron material alone or as an outer layer of a composite roll, the outer layer is subjected to austenitizing heat treatment at 950 to 1150 ° C., and then quenched to 600 ° C. at a cooling rate of 200 ° C./hr or more, and then 460 to 590. Tempering heat treatment at a temperature of ° C. The reasons for limiting the heat treatment conditions are as follows.

Austenitizing temperature: 950 to 1150
℃ In order to precipitate graphite by tempering heat treatment described below,
It is necessary to previously dissolve a large amount of C in the matrix. 95
If it is lower than 0 ° C., the amount of solid solution of C is too small, while if it exceeds 1150 ° C., it is deformed by softening or partially melted locally. Cooling rate: 200 ° C./hr or more up to 600 ° C. When pearlite is formed by eutectoid transformation, it becomes difficult to precipitate graphite by tempering heat treatment described below. For this reason, up to 600 ° C. where there is no possibility that eutectoid transformation occurs,
Cool at 200 ° C / hr or more. If the temperature is lower than 200 ° C./hr, pearlite will be generated partially or in a large amount.

Tempering temperature: 460-590 ° C. To precipitate graphite, C in the quenched structure is diffused,
It is necessary to be assembled. If the temperature is lower than 460 ° C., sufficient diffusion cannot be obtained, and the form of graphite cannot be obtained. On the other hand, 59
If the temperature exceeds 0 ° C., the material is softened, and the wear resistance is impaired. Further, by tempering in the above temperature range, Mo, W, V, Nb, and the like dissolved in the matrix at the time of the austenitizing heat treatment precipitate as fine carbides by the tempering heat treatment.
Because of the secondary curing phenomenon, it has excellent high-temperature hardness. The tempering heat treatment may be performed at least once, but is preferably performed at least twice in order to obtain sufficient graphite precipitation.

As a method of heating the outer layer of the composite roll, a method of heating the entire roll in a heating furnace, or disposing an induction heating coil and a number of gas burners around the outer peripheral surface of the outer layer, thereby rapidly heating only the outer layer. There is a method of heating. In the former case, it takes time to raise the temperature, a thick oxide film is formed on the outer layer surface, and the yield of the outer layer decreases. Furthermore, to avoid melting of the inner layer of cast iron material and heat it, 1100 ° C (preferably 10
(00 ° C.) or less, which makes it difficult to sufficiently form a solid solution of the carbide in the matrix, and it is difficult to obtain sufficient hardness by the subsequent heat treatment. On the other hand, according to the heating method of only the outer layer, coupled with the formation of the intermediate layer, the outer layer can be reliably stopped at 1100 ° C or higher, and the inner layer can be reliably stopped at less than 1100 ° C.
It is possible to prevent a decrease in strength due to coarsening of crystal grains. In addition, since the temperature decreases toward the center of the inner layer (axial core), the heat of the outer layer can be released to the inside after heating to the austenitizing temperature, and the cooling rate of the outer layer deeper can be increased during quenching. it can.

The high-speed cast iron material having graphite of the present invention is:
Rolls requiring abrasion resistance, such as rolls for transporting rolled material in pinch rolls or auxiliary equipment for rolling, as well as rolls for hot rolling or rolling for cold rolling,
Although it is suitable as an outer layer material of a cylindrical member such as a roller, it is needless to say that it can be used not only for such applications but also for various mechanical parts and the like that require wear resistance.

Next, specific examples of the present invention will be described. Example A (1) A mold having an inner diameter of 240 mm was rotated, and a wear-resistant cast iron material shown in Table 1 was centrifugally cast with GNo. The casting temperature is 1430 ° C. The examples are samples Nos. 1 to 4 and are No. 5 conventional high-speed roll materials. The composition unit in the table is% by weight, and the balance is substantially Fe.

[0030]

[Table 1]

(2) After casting, each sample was kept at 1100 ° C. for 30 minutes, and then forcedly cooled at 400 ° C./hr at a cooling rate of 400 ° C./hr.
After cooling to 00 ° C., it was allowed to cool to room temperature (20 ° C.) and quenched. Thereafter, a tempering heat treatment at 530 ° C. for 15 hours was repeated three times. Table 2 shows the measurement results of the graphite area ratio (%) and the surface hardness ( _HRC ) of each sample. According to the table, the amount of graphite increases as the number of times of tempering increases.
Although a large amount of graphite was present in an amount of 1.7 to 5.4% by tempering a number of times, no crystallization of graphite occurred in the conventional high-speed wear-resistant material.

[0032]

[Table 2]

(3) Friction test pieces were taken from each of the samples after tempering three times, and the friction coefficient was measured by a Falex test. What is the Falex test? A pair of V-blocks (stainless steel SUS430) while rotating the test piece
And the friction coefficient and seizure are examined by the magnitude and fluctuation of the rotational torque. The material of the block used this time is S45C. The results are also shown in Table 2. According to the table, the wear resistant material of the embodiment is 2
A reduction effect of 0% or more is observed. Example B (1) The melt of the outer layer material shown in Table 3 was centrifugally cast into a centrifugal casting mold having an inner diameter of φ810 mm, and in Samples Nos. 13 and 14, the outer layer was completely solidified. The molten metal was centrifugally cast to weld the outer layer and the intermediate layer. No. 11 and 12 were 95 mm in outer layer, No. 13 and 14 were 70 mm in outer layer, and 25 mm in middle layer.

Sample Nos. 11 to 14 are all examples. (2) Wait until the outer or middle layer has completely solidified,
The rotation of the mold was stopped, the mold having the outer layer alone or the outer layer and the intermediate layer was set up vertically, and the upper mold and the lower mold were continuously installed at both ends, and the inside was also shown in the same table. Inner layer material (shaft core material) Molten metal was cast.

[0035]

[Table 3]

(3) After roughly casting the composite roll, after preheating uniformly at 600 ° C., the roll is placed between gas burners which are horizontally opposed and arranged in parallel at a pitch of 250 mm along the roll axis direction. Was rotatably supported, and the surface of the outer layer was heated while rotating the roll. The heating was stopped when the surface temperature of the outer layer reached 1125 ° C and the temperature at the center of the inner layer reached 900 ° C. The time required for heating was 180 minutes. From the thermal conductivity data, in the case of the present example, the temperature near the outer peripheral surface of the inner layer was estimated to be 1030 ° C. (4) After the heating was stopped, spray water cooling was immediately performed, the roll surface temperature was rapidly cooled to 500 ° C., and then cooled to room temperature. Thereafter, a tempering heat treatment maintained at 550 ° C. for 20 hours was repeated twice. The results of measuring the graphite area ratio and the surface hardness of the outer layer after the heat treatment were as shown in Table 4 below. From the table, it can be seen that a large amount of graphite is generated in the outer layer of the example, the outer layer has high hardness, and is excellent in abrasion resistance.

[0037]

[Table 4]

(5) After finishing the body surface, the welding condition was confirmed by an ultrasonic flaw detection test. As a result, the welding was good for all rolls. Table 5 shows the results of analyzing components at the center of the thickness of the intermediate layer and at the center of the inner layer (axial core). From the table, it can be seen that in the example in which the intermediate layer was provided, the mixing amount of the outer layer high alloy component in the inner layer was very small.

[0039]

[Table 5]

(6) From the above results, when the roll of the present embodiment is used in the finishing stage of the hot strip mill, it is expected that the abrasion resistance is excellent, the sheet passing property is good, and the temperature rise of the roll can be suppressed. Be expected.

[0041]

According to the heat treatment of the graphite-containing high-speed cast iron material of the present invention and the multi-layer roll having the cast iron material in the outer layer, specific Cr, Mo, W, Nb, V, Fe and C are mutually exchanged. Bonded high hardness composite carbide and specific Si
In the matrix where the crystallized and precipitated graphite exists during solidification by
Precipitated graphite can be sufficiently generated by the prescribed heat treatment, the hardness at room temperature and high temperature is improved, the wear resistance is dramatically improved, and the graphite generated in the solidification process in the structure and the graphite deposited by the heat treatment are improved. In combination, the impact load can be alleviated, crack propagation is prevented, and the friction coefficient is reduced and seizure resistance is improved.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Katayama 2-47, Shikitsu Higashi 1-chome, Namiwa-ku, Osaka-shi, Osaka (72) Inventor Hiroyuki Kimura Hiroyuki Kimura, Higashi-ichi Shikitsu, Naniwa-ku, Osaka, Osaka JP-A-4-176841 (JP, A) JP-A-63-195245 (JP, A) JP-A-3-53042 (JP, A) 5-271855 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 5/00-5/16 B21B 27/00 C21D 9/38 C22C 37/00-37/10

Claims (3)

(57) [Claims] 1. A chemical composition having a wt% of C: 1.8 to 3.6.
%, Si: 2.29 to 3.5%, Mn: 0.1 to 2.0%, N
i: 0.5-10.0%, Cr: 2.0-10%, Mo: 0.
HSS-based cast iron material essentially containing 1 to 10%, W: 0.1 to 10%, V, Nb: 1.0 to 10% in total of one or two kinds, and the balance substantially consisting of Fe On the other hand, it has graphite characterized by being subjected to an austenitizing heat treatment at 950 to 1150 ° C., a quenching heat treatment up to 600 ° C. at a cooling rate of 200 ° C./hr or more, and then a tempering heat treatment at a temperature of 460 to 590 ° C. Heat treatment method for high-speed cast iron. 2. The alloy according to claim 1, further comprising Co: 0.5.
A heat treatment method for a high-speed cast iron material having graphite containing up to 10.0 wt%. 3. A composite roll having an inner layer made of a steel material inside an outer layer formed of a high-speed cast iron material having graphite according to claim 1 or 2, wherein the outer layer is made of 95%.
After austenitizing heat treatment at 0 to 1150 ° C, 60
A heat treatment method for a composite roll, comprising: performing quenching heat treatment at a cooling rate of 200 ° C./hr or more to 0 ° C., and then performing tempering heat treatment at a temperature of 460 to 590 ° C.