JP3105274B2 - Composite roll - Google Patents

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 steel rolling.

[0002]

2. Description of the Related Art Generally, a composite roll is formed by integrally welding an inner layer formed of a tough cast iron material to an inner surface of an outer layer which is a rolling use layer formed of a high alloy roll material having excellent wear resistance. It has both wear resistance and toughness. The form of the composite roll is generally solid, but there is also a hollow roll (called a sleeve roll) for rolling a shaped steel. However, when the outer layer and the inner layer are welded, a high alloy component of the outer layer material is mixed into the molten inner layer material, thereby deteriorating the toughness of the inner layer material. For this reason, in recent years, the outer layer and the inner layer have been separately manufactured,
2. Description of the Related Art Composite rolls that have been diffusion bonded by hot isostatic pressing (HIP) have been manufactured. In this case, since it is not necessary to consider the weldability and castability, a tough steel material is generally used as the inner layer material.

[0003]

After the composite roll is manufactured, usually, the entire roll is subjected to quenching and tempering heat treatment in order to increase the hardness of the outer layer and impart abrasion resistance. At this time, the outer layer expands due to the transformation, and compressive stress remains. On the other hand, a tensile stress is applied to the inner layer due to the expansion of the outer layer. When the outer layer and the inner layer are combined by HIP, there is no need to consider the welding allowance, and the outer layer thickness tends to be thin. Therefore, the outer layer is likely to be damaged by the residual stress described above, and quality defects (for example, generation of pinholes) at the bonding interface are likely to occur. In the process of cooling from the HIP process, the outer layer is transformed, and the same problem occurs.

[0004] The present invention has been made in view of the above-mentioned problems, and is intended to be an HIP which is hardly damaged in the manufacturing process even if the outer layer has a small thickness, and has good soundness at the boundary between the outer and inner layers.
It is an object to provide a composite roll joined by the following.

[0005]

According to the present invention, there is provided a composite roll comprising:
The outer cylindrical body made of high alloy roll material
Inner-layer cylindrical material or cylindrical material made of cast iron
The outer layer and the inner layer are both hot-isostatically pressed.
It is formed by more diffusion bonding. Inner layer cylindrical material
Has the chemical composition of ductile cast iron as a columnar material.
C: 2.8 to 3.8%, Si: 1.5 to 3.2%, M by weight%
n: 0.1 to 1.0% Ni : 0.1 to 4.0%, Mg: 0.02 to 0.10% What uses the balance Fe and inevitable impurities
Is preferred.

[0006] Hot isostatic pressing of both the outer and inner layer materials
Are diffusion bonded at a temperature of 800 to 1100 ° C.

[0007]

The ductile cast iron material has a slightly lower room temperature strength than the steel material conventionally used as the inner layer material, but has a sufficient axial strength unless a high alloy component in the outer layer is mixed. On the other hand, at the time of cooling from the HIP treatment or at the time of heat treatment, the strength in the high temperature range is about 20 kg / mm ^2, which is significantly lower than that of steel. Therefore, plastic deformation follows the expansion caused by the transformation of the outer layer, so that residual stress in the outer layer and the inner layer can be reduced, and joint defects at the boundary can be prevented.

[0008]

1 and 2 show a composite roll according to the present invention. FIG. 1 is a solid roll of a cylindrical body , and FIG. 2 is a cylindrical body.
The outer layer material 1 and the inner layer material 2 are HI
P is diffusion bonded. As shown in FIGS. 3 and 4, these rolls are fitted (clear fit) with the inner layer member 2A on the inner surface of the separately cast outer layer member 1A and wrapped by the mild steel plate capsule 3, as shown in FIGS. After vacuum degassing the interior (preferably 0.1 Torr or less), the two members are diffusion bonded by performing HIP processing. After joining, the capsule 3 is removed, and after roughing, quenching and tempering heat treatment is performed, and finishing is performed. In FIG. 3, 4
Is a spacer made of mild steel (SS material), which is cut and removed at the same time as the capsule 3 is removed. HIP processing conditions are 800-
1,100 ° C. and 500 kgf / cm ² or more are suitable. still,
Between the outer layer member and the inner layer member, for example, JIS standard BNi
-3 by adding a Ni-based brazing material such as
The IP temperature must be between 980 and 1050C, but the pressure can be reduced.

As the high alloy roll material for forming the outer layer material 1 , various materials such as a high-speed tool steel material, a high chromium cast iron roll material, a high chromium roll material with graphite crystallization and the like can be used. The composition example of the high alloy cast iron roll material excellent in wear resistance and the reason for limitation are shown below. The unit is wt%. C: 1.8 to 3.4%, Si: 0.3 to 2.0%, Mn:
0.1 to 1.0%, Cr: 3 to 12%, Mo: 3 to 12%, V:
If the content is 1 to 8%, W: 10% or less, and the balance is substantially FeC: 1.8 to 3.4% and less than 1.8%, the amount of carbides becomes small, and the wear resistance deteriorates. In addition, castability also deteriorates. If it exceeds 3.4%, the toughness decreases. Si: 0.3 to 2.0% Add 0.3% or more to prevent oxidation of the molten metal and impart castability. In addition, it has the effect of increasing the amount of carbides by forming a solid solution in carbides other than Cr carbides (double carbides containing a large amount of Cr), but if it exceeds 2.0%, the material becomes brittle. Mn: 0.1-1.0% In order to fix S mixed as an impurity as MnS.
Add 0.1% or more. On the other hand, if it exceeds 1.0%, austenite grains become coarse and embrittle at high temperatures. Cr: 3 to 12% Usually added to increase hardenability and oxidation resistance, but less than 3% has little effect. On the other hand, if it exceeds 12%, the amount of double carbide containing a large amount of Cr increases. Since the complex carbide containing a large amount of Cr is not as hard as the complex carbide such as W, V, and Mo, the relative proportion to the total carbide amount is preferably small. Mo: 3 to 12% Mo forms carbide with high hardness. In addition, it dissolves in a part of the matrix to improve tempering stability. Below 3%, the effect is too small. Further, it forms a double carbide with V and has an effect of suppressing the separation of specific gravity of V. However, if it exceeds 12%, eutectic carbide increases, leading to a decrease in strength. V: 1 to 8% An MC type carbide having a high hardness is formed to increase wear resistance. However, from the viewpoint of preventing specific gravity separation, the addition of 8% or less is preferable. On the other hand, the effect is small at less than 1%. W: 10% or less W has the effect of increasing the high-temperature softening resistance of the base. Mo has the same effect as Mo and can be replaced with Mo at a ratio of Mo: W = 1: 2. However, since the molecular weight (and therefore the specific gravity) is extremely high as compared with Mo, the addition of more than 10% of , The difference in specific gravity between V and the double carbide increases, and V segregation is likely to occur.

The present roll material is substantially composed of Fe in addition to the above alloy components.
-12%. Co forms a solid solution in the matrix and improves the high-temperature hardness and abrasion resistance. If less than 1%, the effect is small, while if more than 12%, the effect is saturated. The inner layer 2 is formed of a ductile cast iron material. Preferable examples of the composition and reasons for limitation are shown below. The unit is wt%. C: 2.8 to 3.8%, Si: 1.5 to 3.2%, Mn:
0.1 to 1.0%, Ni: 0.1 to 4.0%, Mg: 0.02 to 0.10% Remaining Fe and unavoidable impurities C: 2.8 to 3.8% If C is less than 2.8%, chilling of the material proceeds and toughness is reduced. On the other hand, if it exceeds 3.8%, the graphitization becomes excessive and the strength becomes insufficient. Si: 1.5 to 3.2% Si is contained mainly for the purpose of controlling graphitization.
%, The graphitization becomes insufficient, while if it exceeds 3.2%, the graphitization becomes excessive and Si dissolved in the ferrite weakens the material. Mn: 0.1 to 1.0% Mn is generally effective for bonding with S to remove the adverse effect of S. However, when it is less than 0.1%, the effect is hardly obtained, and when it exceeds 1.0%, the material becomes hard and brittle. Ni: 0.1-4.0% Ni works effectively for graphitization and strengthening of the matrix, but 0.1%
If it is less than 4%, the effect is small, and if it is added in excess of 4%, casting cracks tend to occur (especially in large castings). Mg: 0.02-0.1% Mg is added to cause spheroidization of graphite.
Less than 0.02% has little effect, while 0.1%
If it is added in excess of the above, it is not preferable because the chilling action of Mg and casting defects such as dross are likely to occur.

It is preferable that P and S, which are impurities, be kept at P: 0.1% or less and S: 0.03% or less. P enhances the fluidity of the molten metal, but makes the material brittle. On the other hand, since S inhibits spheroidization of graphite, it is preferably set to 0.03% or less. When casting the inner layer member, inoculation is preferably performed. It is known that inoculation is generally successful for promoting graphitization and for microstructuring. Also for this material, it is more effective to improve the toughness if an inoculant such as CaSi or FeSi is added in an amount of 1.0% or less as a Si content immediately before casting using the inoculation technique. This is because even if the inoculation amount exceeds 1.0%, no further effect can be obtained. In addition, S after inoculation
The i content is adjusted so that it remains within the above range of 1.5 to 3.2%.

Next, specific embodiments will be described. (1) The outer layer member and the inner layer member were formed by casting. Table 1 shows the composition (wt%, balance substantially Fe) of each member.

[0013]

[Table 1]

(2) After casting, it was processed into the following dimensions, and both members were clearance-fitted, and degassed and sealed in a mild steel capsule at a degree of vacuum of 0.07 to 0.08 Torr. Example 1 Outer layer member: outer diameter φ330 × inner diameter φ270 × length 560 (mm), cylindrical body Inner layer member: φ270 × length 1450 (mm), solid body Example 2 Outer layer member: outer diameter φ590 × inner diameter φ530 × length Length 210 (mm), cylindrical body Inner layer member: outer diameter φ530 × inner diameter φ270 × length 210 (mm), cylindrical body (3) The capsule was prepared at a temperature of 1050 ° C and a pressure of 1200 kgf / c.
HIP processing was performed under the conditions of m ² and processing time of 3 Hr. After the processing, capsules and the like were removed and rough processing was performed. (4) The temperature of the composite roll material was raised to 1100 ° C., and after holding for 3 hours, quenching was performed at a cooling rate of about 250 ° C./Hr in Example 1 and about 400 ° C./Hr in Example 2. Next, in both examples, 550 ° C.
Tempering. Each of the outer layers of Examples 1 and 2 was as thin as 30 mm, but no damage occurred during the HIP treatment and the heat treatment. (5) Measurement of the collected Hardness Hardness test piece from the outer layer in Example 1 and 2 both had a H _R C63 (in Hs corresponding to 85/90).

Further, when a tensile test piece was taken from the inner layer and tested, both Examples 1 and 2 showed a tensile strength of 63 kgf / mm.
^{2. The} growth was 2.4%. Further, the test piece was sampled from the boundary between the outer layer member and the inner layer member such that the boundary was substantially at the center of the test piece and perpendicular to the tensile direction (the sample axis direction). Observation of the joint boundary indicated that there was no pinhole and the structure was sound. Further, when subjected to a tensile test, it was broken not at the boundary but at the inner layer material portion.

[0016]

As described above, the composite roll of the present invention comprises an inner layer material (cylindrical material or cylindrical material) formed of ductile cast iron, and an outer layer material formed of a high alloy roll material.
Since diffusion bonded by (cylindrical body) and HIP, can prevent mixing of high alloy elements in the outer layer material or <br/> et lining material, prevents toughness degradation of the inner layer material, yet when the heat treatment, the outer layer member is accompanied to the transformation expansion, since the inner layer material is plastically deformed, reduce the residual stress of the outer layer member-inner layer material, it is possible to ensure the soundness of the thus prevented and joint damage of the outer layer material in the production.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a cylindrical sleeve-shaped composite roll of the present invention.

FIG. 3 is a cross-sectional view showing an encapsulated state of a cylindrical solid composite roll material for HIP processing.

FIG. 4 is a cross-sectional view showing a state in which a cylindrical sleeve-shaped composite roll material is encapsulated for HIP processing.

[Explanation of symbols]

1 Outer layer material 1A Outer layer member 2 Inner layer material 2A Inner layer member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-182306 (JP, A) JP-A-58-221661 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 27/00 B23K 20/00 B23K 20/00 310 C22C 37/10

Claims (2)

(57) [Claims] An outer cylinder formed of a high alloy roll material.
The inner cylindrical member made of ductile cast iron
Or the cylindrical material is fitted, and both the outer layer and the inner layer material are heated.
Diffusion bonded by isostatic pressing
Roll. 2. An outer cylindrical member made of a high alloy material,
Chemical composition is% by weight, C: 2.8-3.8%, Si:
1.5-3.2%, Mn: 0.1-1.0%, Ni:
0.1-4.0%, Mg: 0.02-0.10%, balance
Ductile iron made of Fe and unavoidable impurities
The formed inner layer cylindrical material or cylindrical material is fitted
The outer layer and the inner layer material are both heated to a temperature of 800 to 1100 ° C.
That it is diffusion bonded by hot isostatic pressing
Features composite rolls.