JPH04214837A - Composite roll - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite roll for hot rolling steel materials.

0002

[Prior Art] In order to ensure the wear resistance of the rolling layer and the toughness of the shaft, rolling rolls are usually made of a strong cast iron material such as high-grade cast iron or spheroidal graphite cast iron. An outer layer made of high-alloy cast iron material with excellent wear resistance is welded to the surface to create a composite. In this case, a cylindrical shaft is generally used as the shaft, but a cylindrical shaft may be used for rolling shaped steel.

[0003] Composite rolling rolls are manufactured by casting an outer layer by centrifugal force casting, casting a shaft portion with its inner surface in a semi-solidified state, and welding and integrating the two. Also,
High chromium cast iron is used as the outer layer material of steel rolling rolls, which particularly require wear resistance.

0004

[Problem to be solved by the invention] However, conventionally,
Since the shaft part is made of cast iron, it is difficult to obtain sufficient strength as the tensile strength is less than about 50 kg/mm2.
Also, during welding, the high alloy components of the outer layer mix into the molten metal of the shaft.
Degrades the material. For this reason, there have been problems such as the shaft portion breaking due to residual stress in the outer layer during manufacturing, and breakage accidents occurring during rolling as rolling conditions have become more severe in recent years.

[0005] In order to solve this problem, it may be possible to form the shaft part from graphite steel or cast steel, but these steel materials have a higher solidification temperature than the outer layer material, making it difficult to weld the outer layer and the shaft part. In this case, since the inner surface of the outer layer solidifies later than the solidification of the shaft portion, it is difficult to obtain a sound weld, and there is a problem that the strength of the welded portion is insufficient. In addition, high chromium roll material has C: 2.0
~3.2 wt%, Cr: 10 to 30 wt%,
A large amount of highly hard M7 C3 type chromium carbide is generated in the structure, and it has relatively good wear resistance, but it is relatively brittle and has high hardness due to the high carbon content in the base structure. The drawback is that the chromium carbide tends to chip off from the base. When chipping wear occurs, the chipped parts are transferred to the steel plate, deteriorating the surface quality and causing defective products. In addition, in recent years, there have been strict demands on the cross-sectional shape and dimensional accuracy of hot rolled steel sheets, and in order to meet these demands, there has been a strong demand for improved wear resistance of the rolls.

The present invention was made in view of the above problems, and the outer layer roll material has superior wear resistance compared to high chromium cast iron roll material, and it can be used without impairing the joint integrity of the outer layer and the shaft portion. The object of the present invention is to provide a composite roll whose shaft portion is made of steel.

[0007]

[Means for Solving the Problems] The composite roll of the present invention, which has been made to achieve the above object, comprises a cylindrical outer layer member cast from a high-alloy cast iron material having a specific composition excellent in wear resistance, or A cylindrical outer layer/intermediate layer member, in which an intermediate layer made of a cast steel material with a specific composition is welded to the inner surface of an outer layer made of a cast iron material, is attached to the outer peripheral surface of a shaft member made of a steel material with excellent toughness. Once placed, both members are solid phase diffusion bonded by hot isostatic pressing.

The chemical composition of the high alloy cast iron material is as follows in weight percent: C: 1.5 to 2.5%, Si: 0.2%.
~1.0%, Mn: 1.5% or less, Cr: 3-10%, Mo: 1-9%,
W: 2 to 9%, V: 2 to 10%, the balance being Fe and unavoidable impurities. At this time, in order to improve the material quality, Ni can be contained in an amount of 2% or less in place of a part of Fe.

[0009] Furthermore, the chemical composition of the cast steel material is as follows in weight%: C: 0.1 to 1.5%, Si: 0
．． 2 to 1.0%, Mn: 0.1 to 1.0%
, Cr: 0.1 to 3.0%, Mo: 0
．． 1 to 2.0%, the balance being Fe and unavoidable impurities.

0010

[Function] The outer layer member or the outer layer/intermediate layer member can each be manufactured independently, so manufacturing is easy. Since the outer layer member and the shaft member are solid-phase diffusion bonded by hot isostatic pressing (hereinafter referred to as HIP), the inner surface of the outer layer member does not melt during bonding, resulting in a delay in solidification time. No bonding defects will occur. In addition, the thickness of the diffusion layer at the joint is within 5 mm even when looking at carbon, which is a light element that diffuses easily. The outer layer member can be effectively used up to the vicinity of the boundary.

In addition, in the case of outer layer/intermediate layer members in which the intermediate layer is formed on the inner surface of the outer layer, machining of the inner circumferential surface (fitting surface) of the member is easy, and solid phase diffusion bonding with the shaft member is extremely easy. It can be done easily. Moreover, during cooling or heat treatment after the HIP process, the transformation temperature difference due to the difference in material between the outer layer and the shaft member can be changed in stages by the intermediate layer, and residual stress can be reduced.

The chemical composition (unit weight %) of the outer layer member or the high alloy cast iron material forming the outer layer is limited for the following reasons. C: 1.5 to 2.5% C combines with Cr, Mo, W, and V to form various carbides with high hardness and improve wear resistance. 1.5%
If it is less than that, the amount of carbide will be too small and the wear resistance will be insufficient. If it exceeds 2.5%, a large amount of primary carbide crystallizes directly from the molten state, resulting in a decrease in crack resistance.

Si: 0.2 to 1.0% Si is an element necessary for deoxidizing the molten metal, and also improves the flow of the molten metal, so it is added in an amount of 0.2% or more. on the other hand,
If it exceeds 1.0%, the material becomes brittle. Mn: 1.5
% or less Mn is added to deoxidize and desulfurize the molten metal. It also improves hardenability and wear resistance, but
If it exceeds 1.5%, the austenite crystal grains will become coarser and cause cracking during quenching, which is not preferable.

Cr: 3 to 10% Cr partially forms a solid solution in the base structure to improve the hardenability of the base and improve wear resistance. Further, it combines with C to form a highly hard carbide, further improving wear resistance. If it is less than 3%, the amount of carbide is small and the wear resistance is poor, and if it exceeds 10%, the amount of carbide is excessive and the toughness is reduced.

Mo: 1 to 9% Mo improves the hardenability of the base structure and combines with C to form fine Mo2C type carbides, thereby improving wear resistance. If it is less than 1%, the effect of improving hardenability will not be noticeable and the amount of carbide produced will be small, resulting in poor wear resistance, and if it exceeds 9%, the amount of carbide will be saturated, resulting in a cost disadvantage. Furthermore, Mo dissolved in a supersaturated state stabilizes the retained austenite in the base, making it difficult to obtain sufficient hardness.

W: 2 to 9% W is a strong carbide-forming element, and upon tempering, it precipitates finely as MC type carbide, resulting in significant secondary hardening. Although 2% or more is required to obtain this effect, if it exceeds 9%, crystallized carbides increase and crack resistance deteriorates. V: 2-10% V makes the casting structure fine and dense and toughens the base. Further, it combines with C to form highly hard V carbide. Since the carbide is formed in a finely dispersed manner in the structure, it improves wear resistance. The range of C content of the present invention (1.5 to 2
．． In order to obtain the above effect of V at 5%), it is desirable to add 2% or more of V. On the other hand, if it exceeds 10%, the effect is saturated and the material becomes brittle.

In addition to the above-mentioned components, the outer layer material of the present invention is made essentially of Fe. Incidentally, since both P and S make the material brittle, the smaller the amount, the more desirable. It is preferable to keep P: less than 0.05% and S: less than 0.05%. In addition to the above-mentioned alloy components, one or more of the following elements may be included as alloying elements for improving the high chromium cast iron material in place of a part of Fe. Although Ni cannot be expected to cause secondary hardening during tempering, it improves hardenability. If it exceeds 2%, austenite becomes stabilized, which is not good. A
l has a large effect on degassing, and when casting the outer layer material, 0.
When the content is 1% or less, casting defects can be effectively removed. Nb is effective in refining the casting structure, and Nb
Although it also contributes to precipitation hardening, it is an element that tends to segregate, so its content is preferably 1.0% or less.

The outer layer material of the present invention improves the hardenability of the base structure while keeping the C content low, and has wear resistance by actively adding Mo, Cr, V, and W, which form highly hard carbides. It is a high-alloy cast iron material with excellent properties. Therefore, this outer layer roll material has a lower C content than conventional high chromium roll materials, but while conventional rolls have a structure mainly composed of Cr carbide, this roll material has a structure mainly composed of Cr, Mo, V, Wear resistance is improved by producing various types of high hardness double carbides in the matrix structure using W. on the other hand,
The above matrix structure also has a low C content, so the toughness is improved,
Coupled with the formation of the double carbide, the occurrence of chipping of the structure described above is prevented, and as a result, the life of the roll can be significantly improved.

Further, the chemical composition (unit weight %) of the cast steel material forming the intermediate layer of the outer layer/intermediate layer member is limited for the following reasons. C: 0.1 - 1.5% If it is less than 0.1%, castability will deteriorate, while if it exceeds 1.5%, carbides mainly consisting of cementite will increase, making it brittle and causing poor weldability. be.

Si: 0.2 to 1.0% If it is less than 0.2%, the deoxidizing effect is not sufficient;
%, mechanical properties deteriorate. Mn: 0.1 to 1.0% Mn is added to remove the adverse effects of S and as an auxiliary deoxidizer for Si. If it is less than 0.1%, its effect will be insufficient, while if it exceeds 1.0%, it will make the material hard and brittle.

Cr: 0.1 to 3.0% Cr improves the hardenability of the matrix and contributes to improved strength. If it is less than 0.1%, its effect is insufficient, while if it is 3.0%
If it is added in excess of %, carbides will increase and it will become brittle. Mo: 0.1 to 2.0% It has the same effect as Cr, and a content of 0.1 to 2.0% is appropriate.

In addition to the above-mentioned components, the intermediate layer material according to the present invention is made essentially of Fe. In addition, both P and S deteriorate the toughness of the material, so the smaller the better, 0.1
It is best to keep it below %.

[0023]

[Example] Fig. 1 shows the structure of a composite roll of the present invention, in which an outer layer member 1 forming a rolling layer (outer layer) is arranged on the outer circumferential surface of a shaft member 2, and is solid-phase diffusion bonded by HIP. There is. The outer layer member 1 is a cylindrical body, and is cast by centrifugal force casting (horizontal type, inclined type, vertical type) or static casting. Since it is made of a single material, there is no risk of cracking due to excessive residual stress as long as you pay attention to the cooling rate after casting. As the material of the outer layer member 1, the above-mentioned high alloy cast iron material is used.

The shaft member 2 is a cylindrical body, and is manufactured by static casting or forging after casting. In addition, if the shaft member is cylindrical, centrifugal force casting can also be applied. Materials include low-alloy cast steel, high-alloy cast steel, and SCM specified by JIS.
Steel materials such as steel, SNCM material, etc. can be used. As a result, the tensile strength of the shaft member can be increased to 60 kg/mm2 or more, and sufficient strength and toughness can be ensured.

In order to solid phase diffusion bond the outer layer member 1 and the shaft member 2, the outer layer member 1 is fitted onto the shaft member 2, and both members 1
, 2 by removing the air in the gap between the fitting parts and performing HIP processing. In order to remove the air in the fitting part gap, as shown in FIG. , is done by degassing the air inside it. 6 is a degassing pipe, which is closed by caulking or welding after vacuum degassing.

Alternatively, as shown in FIG. 4, both fitting ends may be welded and air may be evacuated through a degassing pipe 6 attached so as to communicate with the fitting gap. Incidentally, by dividing the metal parts 3 and 4 and subjecting them to HIP processing, it is possible to downsize the HIP processing furnace and reduce equipment costs. Since the shaft member 2 is made of steel, the divided metal parts can be easily joined and integrated by welding after HIP treatment.

FIG. 5 shows the case of a sleeve roll for H-beam steel whose shaft member is a cylindrical body, and the cover 5 is formed to enclose a composite roll material in which the outer layer member 1 is fitted to the shaft member 2. . On the other hand, as shown in FIG. 2, the outer layer member 1
By using an outer layer/intermediate layer member 11 in which the intermediate layer 13 is integrally welded to the inner surface of the outer layer 12 instead of the outer layer 12,
and the intermediate layer 13 are welded together to obtain a three-layer composite roll in which the intermediate layer 13 and the shaft member 2 are solid phase diffusion bonded. The outer layer/intermediate layer member 11 is easily cast by centrifugally casting the outer layer 12 and then centrifugally casting a molten intermediate layer material onto the inner surface thereof. Note that the thickness of the intermediate layer 13 is as thin as about 10 to 30 mm, and the amount of molten metal in the intermediate layer material is smaller than that in the shaft member, so poor welding due to reversal of solidification temperature does not pose a problem.

After the HIP treatment, the composite roll material is rough-processed and then held at 950 to 1200°C to austenite to harden the outer layer member, then rapidly cooled by spray water cooling etc. and quenched, and then heated to 500 to 650°C. 2 to 20
Several time-hold temperings are carried out. In addition, if the material is small, it is possible to harden it simply by cooling it in air. The composite roll of the present invention can be applied to a wide range of rolling rolls, from small steel rolling rolls to large rolls with body diameters of φ400 to φ900 mm, such as wide strip steel rolling rolls, and sleeve rolls for H-shaped steel rolling. It is.

Next, specific examples will be given. (1) Outer layer member and outer layer/middle layer member: outer diameter 340 mm, inner diameter 290.0 to 290.2 mm, length 1250 mm
A cylindrical body was manufactured by centrifugal casting. Note that the thickness of the intermediate layer of the outer layer/intermediate layer member was 20 mm. These members have an outer diameter of 289.8 to 290.0 mm and a length of 1450 m.
After fitting into the shaft member of No. m and deaerating the gap between the fitting parts, HIP treatment was performed. HIP processing conditions are pressure 200kg/c
m2, and the temperature is 1080°C. The chemical compositions (wt%, remainder substantial Fe) of the outer layer members and outer layer/intermediate layer members are shown in Table 1 below.
Shown below. Note that the outer layer member of the comparative example is a high chromium cast iron material.

[0030]

[Table 1]

(2) After HIP treatment, heated to the austenitizing temperature shown in Table 2 below, rapidly cooled, and tempered at the temperature shown below.
Heat treated to remove distortion.

[0032]

[Table 2]

(3) After heat treatment, surface hardness, boundary 45° compressive strength (compressive strength measured using a test piece with the joint interface between the outer layer member and the shaft member placed at 45° with respect to the loading direction), etc. was measured. The results are shown in Table 3 below.

[0034]

[Table 3]

(4) From Table 3, the composite roll of the present invention has a high strength of about 80 kg/mm2 or more in the shaft member, a boundary 45° compressive strength of about 250 kg/mm2 or more, and a large strength on the surface of the outer layer member. It was confirmed that compressive stress remained and the joint boundary had excellent soundness and breakage resistance. Furthermore, the surface strength was also higher than that of the comparative example, and it is presumed that the abrasion resistance was excellent.

[0036]

[Effects of the Invention] As explained above, in the composite roll of the present invention, the outer layer member serving as the rolling layer (outer layer) is solid phase diffusion bonded by HIP to the outer peripheral surface of the shaft member made of steel material with excellent toughness. This prevents the inner surface of the outer layer from melting when joining both parts, resulting in a healthy joint with no deterioration in strength, and the material properties of the shaft member can be utilized as is, ensuring high strength. As a result, breakage resistance can be improved. Further, since the diffusion layers of both members are extremely thin, approximately 5 mm or less, it is possible to effectively utilize the outer layer member formed of an expensive high-alloy material.

Furthermore, by using an outer layer/intermediate layer member in which an intermediate layer of a specific component is welded to the inner surface of the outer layer, processing of the fitting surface is easy, and solid phase diffusion bonding with the shaft member is extremely easy. Since the transformation temperature difference can be changed in stages, it is also effective in reducing residual stress. In addition, the outer layer material of the present invention suppresses C, improves the hardenability of the base structure, and forms high-hardness carbides, and uses Mo, Cr, etc.
, V, and W are actively added to it, so Mo, Cr, and V are contained in a strong base with low C content.
, W, and various forms of high-hardness double carbides, the occurrence of chipping of carbides is prevented, and it has extremely superior wear resistance compared to conventional high chromium cast iron roll materials.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a composite roll of the present invention.

FIG. 2 is a sectional view of another composite roll of the present invention.

FIG. 3 is a sectional view showing a method of degassing the joint of the composite roll material.

FIG. 4 is a sectional view showing another method of degassing the joint of the composite roll material.

FIG. 5 is a sectional view showing another method of degassing the joint of the composite roll material.

[Explanation of symbols]

1 Outer layer member 2 Shaft member 11 Outer layer/middle layer members 12 Outer layer 13. Middle class

Claims (3)

[Claims] [Claim 1] The chemical composition is in weight %, and C
:1.5-2.5%, Si:0.2-1.0%
, Mn: 1.5% or less, Cr: 3-10
%, Mo: 1-9%, W: 2-9%,
V: 2 to 10% A cylindrical outer layer member cast from a high-alloy cast iron material with the balance being Fe and unavoidable impurities is placed on the outer peripheral surface of a shaft member made of a steel material with excellent toughness, and both members are heated. A composite roll characterized by being solid phase diffusion bonded by isostatic pressure. [Claim 2] The chemical composition is in weight %, and C
:1.5-2.5%, Si:0.2-1.0%
, Mn: 1.5% or less, Ni: 2% or less, Cr: 3-10%, Mo: 1-9%,
W: 2 to 9%, V: 2 to 10% A cylindrical outer layer member cast from a high-alloy cast iron material consisting of Fe and unavoidable impurities is placed on the outer peripheral surface of a shaft member formed from a steel material with excellent toughness. A composite roll characterized in that both members are solid phase diffusion bonded by hot isostatic pressing. [Claim 3] The chemical composition is in weight %, and C
:1.5-2.5%, Si:0.2-1.0%
, Mn: 1.5% or less, Cr: 3-10
%, Mo: 1-9%, W: 2-9%,
V: 2 to 10%, C: 0.1 to 1.5%, Si: 0 on the inner surface of the outer layer cast from high alloy cast iron material consisting of the balance Fe and unavoidable impurities.
．． 2 to 1.0%, Mn: 0.1 to 1.0%
, Cr: 0.1 to 3.0%, Mo: 0
．． A cylindrical outer layer/intermediate layer member, in which an intermediate layer is cast from cast steel with a balance of 1 to 2.0% Fe and unavoidable impurities, is welded to the outer peripheral surface of a shaft member made of a steel material with excellent toughness. A composite roll characterized in that both members are arranged and solid phase diffusion bonded by hot isostatic pressing.