JPH11244914A - Roll for rolling hot strip and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roll for hot-rolling strip without necessitating so large HIP furnace at the time of executing hot isobaric pressurization(HIP) treatment and also the reliability of the shaft material of a finished roll of which is higher and to provide the manufacturing method therefor. SOLUTION: This invention relates to the roll for hot-rolling strip which has supporting parts 12, 13 which become bearing parts at both ends of a solid shaft material 1 and has an outer layer 2 consisting of high-speed steel system powder which is sintered on the outer periphery in the middle part of the solid shaft material 1 by hot isobaric pressurization and also diffusely joined on the outer periphery in the middle part and its manufacturing method. In its manufacture, a metallic capsule is fixed around the shaft material, the supporting part 12 on the driving side of which is integral with the middle part of the solid shaft material 1, the high-speed steel system powder is filled up into the annual space between the shaft material and the metallic capsule and hot isobaric pressurization treatment is executed to them under a high-temp., high-pressure gas atmosphere. In this way, after sintering the high-speed steel system powder and also diffusely joining it to the solid shaft material 1, the supporting part 13 on the driven side is joined to the solid shaft material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolling roll having an outer layer made of a powdered high-speed steel material sintered by a hot isostatic pressing method (HIP) on the outer periphery of a solid shaft material, and its production. About the method.

[0002]

2. Description of the Related Art Conventionally, as a work roll for hot plate rolling, there is, for example, a continuous casting build-up roll whose outer layer is made of a high-speed steel material (W088 / 07594). Since the roll of the high-speed material has excellent wear resistance, it significantly contributes to the improvement of rolling productivity and quality. In the case of a casting roll, there is a problem that the coarsening of the structure due to solidification during casting and segregation of carbide due to uneven solidification are apt to occur, so that the surface roughening resistance is deteriorated. On the other hand, in the powdered high-speed material, the hard carbide for improving the wear resistance is uniformly and finely dispersed, so that it is excellent in the wear resistance and the rough surface resistance.

When making a roll using such an excellent powdered high-speed material for the outer layer, a metal capsule is attached around the shaft of the roll, and a predetermined high-speed steel is placed in an annular space between the shaft and the metal capsule. System powder and fill the entire roll with HI
It is necessary to charge the P furnace and perform HIP processing. In order to load the entire roll into the HIP furnace, it is necessary to use a correspondingly large HIP furnace in the case of a large roll, so that the energy cost and the atmosphere cost are extremely high.

Therefore, as proposed in Japanese Patent Application Laid-Open No. 56-69304, a shaft material having a length corresponding to the body of a roll is used, and a metal powder is HIP-processed around the shaft material.
After the processing, there is a method of attaching the support portions at both ends of the shaft member by welding or the like. According to this method, the size of the furnace at the time of the HIP processing only needs to be large enough to accommodate the body of the roll, and therefore, there is an advantage that a HIP furnace large enough to accommodate the entire roll is not required. There is.

[0005] However, since one of the support portions of the shaft member normally receives a driving force, a large torque acts. When a large load is applied to the roll at the time of rolling due to the bite of the cold material or the like, the load is applied 2 to 4 times that of the normal rolling. When the supporting portion of the shaft is joined to the body by welding or the like, if there is any defect or poor joining at that location, the material strength becomes extremely small and the reliability is poor.

[0006] Therefore, using a shorter shaft material, H
It has been proposed in Japanese Patent Publication No. 7-17930 to form an outer layer of a powdered high-speed material sintered by IP processing and then forge the end of the shaft to form bearing portions at both ends of the shaft. ing. As described above, by using the shaft material slightly shorter than the final roll length, a slightly smaller HI is used as compared with the case where the HIP processing is performed using the shaft material having the final roll length.
It can be appreciated that a P furnace can be used. But,
Thereafter, a shaft having a predetermined length is formed by forging, so that a shaft that is too short cannot be used. Also,
Since the volume and weight of the shaft are not different from those of the finished product, extra energy is required to heat the HIP furnace. Further, in order to form a predetermined bearing by forging the shaft after the HIP treatment, it is necessary to heat the powdered HSS-based material together with the HIP treatment,
There was also a fear of such crystal growth.

[0007]

Therefore, according to the present invention, the HIP process does not require a large HIP furnace, and the rolled roll for the hot plate rolling has a highly reliable shaft material. And a method for producing the same.

[0008]

According to the present invention, there is provided a hot-rolling roll comprising a solid shaft having support portions serving as bearing portions at both ends thereof.
The solid shaft material has an outer layer made of a high-speed steel powder which is sintered by hot isostatic pressing on the outer periphery of a central portion thereof and is diffusion-bonded to the outer periphery of the central portion. The central portion of the first member and the supporting portion on the driving side are integrally formed, and the supporting portion on the driven side is characterized by being joined to a solid shaft.

Here, the central portion of the solid shaft and the supporting portion on the driving side are formed by integrally casting, and then, if necessary, by machining or plastic working. It is made of cast steel, forged steel or graphite cast steel containing% carbon. The connection of the driven-side support to the center of the solid shaft is performed by welding, casting, or the like, and the material of the driven-side support is almost the same as that of the solid shaft.

Further, the method for producing a hot plate rolling roll according to the present invention has a support portion serving as a bearing portion at both ends of a solid shaft, and a hot or the like is provided on an outer periphery of a central portion of the solid shaft. In the production of a hot-rolling roll having an outer layer made of a high-speed steel powder that is sintered by a direct pressure and is diffusion-bonded to the outer periphery of the central portion, the supporting portion on the driving side is formed of the solid shaft material. Attach a metal capsule around the shaft that is integral with the center of the tube, fill the annular space between the shaft and the metal capsule with high-speed powder, and heat it under a high-temperature, high-pressure gas atmosphere. By subjecting the high-speed steel powder to sintering by performing isotropic pressure pressing treatment, and performing diffusion bonding to the solid shaft material, a driven side support portion of the solid shaft material is bonded. It is assumed that.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The hot plate rolling roll of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a hot-rolling roll in the rotation axis direction, and FIG. 2 is a cross-sectional view of a case where a supporting portion on a driven side is cast.

In FIG. 1, reference numeral 1 denotes a solid shaft, and a driving-side support portion 12 is formed integrally with the solid shaft 1 at one end. The outer layer 2 obtained by sintering the powdered high-speed material is diffusion-bonded around a central portion (a portion corresponding to a body portion) of the solid shaft 1. The supporting portion 13 on the driven side of the shaft is joined to the shaft by welding 14.

The shaft 1 used here is 0.1 to
It is preferably any of cast steel, forged steel and graphite cast steel containing 2% by weight of carbon. If the amount of carbon exceeds 2%, the amount of carbide or graphite becomes excessive, so that the necessary tensile strength, toughness and the like are not secured. If the amount of carbon is less than 0.1%, the required strength cannot be secured.

The outer layer 2 is made of a sintered alloy of a high-speed powder, and the composition of the high-speed steel is C: 1 to 4% by weight,
Si: 0.2-3%, Mn: 0.1-1.5%, Cr:
2 to 14%, Mo: 9% or less, V: 3 to 15%, W: 2
Preferably, it has a chemical component of not more than 0% and the balance substantially consisting of Fe and unavoidable impurities. Further, Ni: 5% or less, Co: 10% or less, Nb:
Any one or more of 5% or less, Ti: 5% or less, and Zr: 5% or less may be contained. In order to produce a high-speed powder, the mixture of the above components is preferably melted and powdered by a gas atomizing method or a water atomizing method. The average particle size of the alloy powder obtained by such a method is 20 to 1
Desirably, it is 50 μm. Further, this high-speed powder may further contain 20% by weight or less of any one or more hard particles of carbide powder such as V, W, Mo, Ti, etc., carbonitride powder and boride powder.

At the time of the HIP processing, a cylindrical metal capsule is attached around a shaft having a driving-side supporting portion integrated with a central portion (a shaft portion of a body portion) of a solid shaft. A capsule bottom lid is welded between the lower end of the metal capsule and the shaft material, and the capsule is filled with a high-speed powder so as to have the above composition. A capsule upper lid is welded to the other end of the capsule, and the inside of the capsule is degassed and released through a degassing hole provided in the upper lid, and an inert gas is filled in the capsule as necessary. Thereafter, the deaeration hole is sealed.

The shaft material (with the supporting portion serving as the driving side shaft) having the metal capsule filled with the high-speed powder as described above is charged into a HIP processing furnace and the high-speed high-pressure gas atmosphere is used. The powder is sintered and diffusion bonded to the solid shaft. The sintering process in the HIP processing furnace is performed under the following conditions. In an argon atmosphere, at a temperature of 1250 ° C. or less, particularly at a temperature of 1000 to 1250 ° C., and 50 to 2
Sinter at a pressure of 00 MPa. HIP sintering pressure is 50
If it is less than MPa, the porosity of the obtained material is large, such being undesirable. A more preferred HIP sintering pressure is 100
１５０150 MPa. The HIP sintering time under the above conditions is preferably 2 to 10 hours. The metal capsule on the surface of the sintered material thus obtained is removed by machining, and the surface of the HIP-sintered powdered high-speed material is polished.

The heat treatment of the roughened powdered high-speed steel consists of quenching and tempering.
The temperature is preferably set to 50 ° C. or lower. Maximum quenching temperature is 1
If the temperature exceeds 250 ° C., carbides grow and become excessive, which is not preferable. Further, it is preferable that the maximum temperature of the tempering is set to 600 ° C. or lower and the minimum temperature is set to 150 ° C. or higher. If the minimum temperature is lower than 150 ° C., a martensite phase appears in the HSS structure and expands, and stress is generated in the diffusion bonding portion, which is not preferable. The quenching time is preferably from 1 to 10 hours. The tempering is preferably performed in two or more stages, and the temperature conditions may be the same, but the tempering time is preferably 1 to 10 hours.

Using a roll material that has been subjected to disassembly and heat treatment, the supporting portion 13 on the driven side is welded 14 as shown in FIG.
To the solid shaft 1. Instead of this welding, FIG.
, A mold material 21 is mounted on the shaft material, and a shaft material end portion 22 serving as a support portion on the driven side can be cast in the mold material. SCM4 as shaft material
When a forged steel such as 40 is used, it is preferable to join the supporting portions on the driven side by welding, and when the material of the shaft material is cast steel, graphite cast steel, or the like, it is preferable to cast the shaft material.

The above-described removal processing and heat treatment of the metal capsule are easier to handle before joining the driven-side support portion, but may be performed after the support portion is joined. As described above, in the hot-rolling roll of the present invention, the drive-side supporting portion at one end of the solid shaft is formed integrally with the shaft, and the driven portion at the other end is driven. The supporting part on the side is joined by welding or the like after HIP processing. For this reason, the length of the roll at the time of the HIP processing is a length in which one support portion is attached to the body, and therefore, the length of the roll is shorter than the final length without one support portion. is there. That is, the body dimension is 680mm in diameter
In the case of a hot-rolling roll having a length of 2050 mm, the length of the supporting portion on the driving side is 1565 mm and the length of the supporting portion on the driven side is 2195 mm, so that the total length is 5810 mm. For this reason, HIP which can accommodate this total length of 5810mm when made as before
Although a processing furnace was necessary, in the present invention, it is only necessary to be able to accommodate the one having a length of 3615 mm which is the sum of the length of the body portion and the length of the supporting portion on the driving side. When heat treatment is performed with this size, the heat treatment furnace may be small.

In the present invention, since the driving-side support portion on which the driving force is applied is integrated with the shaft member of the body portion, even when a large load is momentarily applied, it can sufficiently withstand the stress. .

[0021]

EXAMPLES Rolls for hot strip rolling having the dimensions shown in Table 1 were prepared. Here, what is shown as Examples 1 and 2 uses a shaft having a body size + the length of a driving side support portion as a solid shaft, and is shown as Comparative Examples 1 and 2. A HSS-based sintered layer having a composition shown as an outer layer in Table 2 was formed on the outer periphery thereof by HIP using a shaft having a length only at the body portion. This HIP treatment is performed in an argon atmosphere at a temperature of 1150 ° C. and a pressure of 120M.
Pa was performed for 2 hours, followed by quenching at 1150 ° C. for 15 minutes, followed by tempering at 580 ° C. for 3 hours three times.

[0022]

[Table 1]

The shafts used in the examples and comparative examples have the compositions shown in Table 2 as shaft materials. Examples 1 and comparative examples 1 are SCM440 materials, and examples 2 and comparative examples 2 are ductile cast iron materials. is there. In Example 1, after the heat treatment, only the supporting portion on the driven side was joined by welding. In Comparative Example 1, the supporting portions on the driving side and the driven side were joined by welding. In Example 2, only the support portion on the driven side was spliced with ductile iron as shown in FIG. In Comparative Example 2, the supporting portions on the driving side and the driven side were jointed with ductile cast iron.

[0024]

[Table 2]

The maximum shear stress acting on the driving side of the rolling roll is expressed by the following equation. That is, the maximum shear stress τ generated in the shaft is τ = 16T / πd ³ . Here, T is the emergency maximum torque, π is the pi, and d is the shaft diameter. Therefore, the above-described examples 1 and 2 and comparative examples 1 and 2 were manufactured.
Table 3 shows the maximum shear stress acting on the drive side of the hot-rolling roll. As compared with the material strengths of SCM440 and ductile cast iron shown in the same table, the maximum shear stress is sufficiently large even when the safety factor is calculated to be 2.5 to 4 times.

[0026]

[Table 3]

As described above, when the driving-side support portion is integrated with the shaft member, a sufficiently reliable strength is exhibited. However, as shown in Comparative Examples 1 and 2, when the drive portion is joined or produced by welding or casting, there is a possibility that the drive portion may be broken if the weld portion is defective or the joining is insufficient. In the case of casting, the cast material is originally weak in material strength and marginal when a safety factor is applied. In addition, if the surface is notched or defective, it may be broken.

On the other hand, even if the supporting portion on the driven side is joined, no shear stress is generated on the driven side, so that joining or casting is sufficient.

[0029]

As described above, according to the hot-rolling roll and the method of manufacturing the same of the present invention, a large HIP furnace is not required when performing the HIP treatment,
The shaft material of the finished roll is highly reliable.

[Brief description of the drawings]

FIG. 1 is an example of a hot-rolling roll of the present invention, and is a cross-sectional view in a rotation axis direction.

FIG. 2 is a cross-sectional view in a case where a hot-rolling roll of the present invention is used to cast a supporting portion on a driven side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid shaft material 2 Outer layer 12 Support part of drive side 13 Support part of driven side 14 Welding 20 Roll material 21 Mold 22 Shaft material end

Claims (2)

[Claims] 1. A solid shaft having support portions at both ends, which serve as bearings, and which is sintered by hot isostatic pressing on the outer periphery of the center of the solid shaft. In a hot-rolling roll having an outer layer made of a high-speed powder that is diffusion-bonded to the outer periphery, a center portion of the solid shaft and a supporting portion on a driving side are integrally formed, and a supporting portion on a driven side is provided. The part is joined to a solid shaft material, the roll for hot plate rolling. 2. A solid shaft having a support portion serving as a bearing at both ends thereof, wherein the solid shaft is sintered by hot isostatic pressing on the outer periphery of a central portion thereof. A method for manufacturing a hot-rolling roll having an outer layer made of a high-speed powder that is diffusion-bonded to the outer periphery, wherein a support portion on a driving side is formed around a shaft integrated with a central portion of the solid shaft. Attach a metal capsule, fill the annular space between the shaft material and the metal capsule with high-speed powder,
This is subjected to hot isostatic pressing under a high-temperature and high-pressure gas atmosphere, thereby sintering the Heiss powder and, after diffusion bonding to the solid shaft, to the solid shaft. A method for manufacturing a hot-rolling roll, comprising joining a support portion on a driven side.