JP3172483B2 - Composite roll for metal strip rolling and method of manufacturing the same - 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 suitable for use as a large-sized work roll for cold rolling of a metal strip, and more particularly to a composite roll which is susceptible to breakage of the roll and occurrence of flaws or the like on the rolled metal strip. The present invention relates to a composite roll for rolling a metal strip and a method for producing the same.

[0002]

2. Description of the Related Art In the rolling of steel sheets, wire rods, steel bars, etc., rolls for preventing scratches and dirt during rolling to improve the surface quality and to prevent roll wear during rolling are disclosed in, for example, Rolls having a material with high hardness and a high Young's modulus as described in JP-A-60-261609 and JP-A-63-195243 have been developed and applied. Conventionally, these rolls are rolls in which an integral body or a small sleeve is fixed to steel, and are mainly rolls having a relatively small roll diameter and a short length. For example, in a roll for a Sendzimir rolling mill used for rolling steel sheets, an integrated material is used and the diameter of the roll is 20 mm.
mm to 90 mm, the length is about 300 mm to 1300 mm, and
In rolls for wire rod rolling mills, a high-hardness sleeve is incorporated into a steel arbor and fixed by circumferential stress using a wedge-shaped ring.The diameter of the roll is 50 mm to 200 mm, and the length of each sleeve is 100 to 100 mm. Most of them were small rolls of about 200mm.

In recent years, high-speed rolling using large rolls, such as a fully continuous cold tandem rolling mill, has been aimed at in order to greatly improve the production efficiency of steel sheets. In addition, there has been a strong demand for improved quality of the rolled steel sheet surface. For this reason, it has high hardness and high Young's modulus characteristics that are advantageous for preventing scratches on the steel sheet surface, preventing roll wear, improving gloss, etc., and large rolls with a roll diameter of 150 mm or more and a roll length of 1000 mm or more. Is desired.

[0004]

As a measure to cope with such a demand, it is conceivable to apply a conventional technique and arrange a plurality of small rolls in the axial direction. However, in such a method, although the roll barrel can be lengthened, when a steel sheet is rolled using this roll, there is a problem that the roll is easily broken at a corner of an adjacent small roll due to a load. In this case, there is a problem that a load distribution is generated, a step is generated on the contact surface of the adjacent small rolls, and a linear flaw is generated on the surface of the steel sheet, which causes a reduction in product yield. On the other hand, when manufacturing a large roll in which all the rolls are formed integrally, there is a problem that the manufacturing cost is increased even by the sintering method, and in addition to the powder filling for roll molding to the cold isostatic pressing (CIP). In the process of handling in embossing or the like, there is a problem that the molded body is easily collapsed, and distortion due to shrinkage due to sintering is added, so that it is difficult to obtain desired dimensions and the yield is significantly reduced. In addition, in the case of large rolls, it is common to use a chock attached to the neck of the roll during rolling. In this case, since the neck is also made of a hard material, the bearings inside the steel chock are worn. There is a problem that it cannot withstand use.

[0005] Therefore, an object of the present invention is to provide a roll for rolling to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide an inexpensive roll for rolling a metal strip. Another object of the present invention is to provide an inexpensive roll for rolling a metal strip, which uses a high-strength, high-Young's modulus material for the barrel while suppressing bearing wear inside the chock. Still another object of the present invention is to provide a manufacturing method for providing the above-mentioned roll to a large-sized roll of a desired size at low cost.

[0006]

SUMMARY OF THE INVENTION The present invention is a composite roll in which a roll barrel and a roll neck are made of different materials, wherein the roll barrel is a sintered body in which two or more cylindrical bodies are connected in the axial direction. And a fitting hole for fitting the other shaft end in the axial direction of one of the joining ends of the roll barrel and the roll neck. It is a composite roll for rolling.

[0007] As a constituent material of the roll of the invention, WC (tungsten carbide) is added to the roll barrel.
It is preferable to use a system alloy material, and it is preferable to use a steel material for the roll neck.

The present invention also relates to a method of molding an alloy powder into a cylindrical body, stacking two or more of the cylindrical bodies substantially coaxially and subjecting them to a sintering treatment and / or a hot isostatic pressing treatment. In the axial direction of one of the joining ends of the roll barrel and the roll neck, a fitting hole for fitting the other shaft end is formed, and a fitting process is performed. This is a method for producing a composite roll for rolling a metal strip.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In cold rolling of steel strip, conventionally,
Using a steel work roll, a high load of several hundred tons to several thousand tons is applied to roll to a desired thickness. In such cold rolling, the rolls are liable to wear, and during the rolling, filings at the ends of the steel strip and foreign substances in the supplied rolling oil are liable to bite between the rolls and the strip to generate flaws. I was always having problems.

In order to solve these problems, it is effective to increase the hardness and Young's modulus of the roll barrel in contact with the steel sheet to be higher than that of steel. Then, the inventors studied variously about the structure of a roll provided with a roll barrel having such high hardness and high Young's modulus characteristics.

[0011] For the above-mentioned reason, a roll barrel cannot be used in combination with a roll barrel portion that comes into contact with the strip, so that the roll barrel needs to be an integral body. However, in this case, if the roll neck portion is integrated, the high hardness roll neck portion is incorporated into the steel bearing and mounted on the chock, and the bearing is worn and cannot be used. Therefore, the inventors have made a number of studies and have adopted a composite roll structure in which the roll neck portion is made of steel and the steel neck portion is fitted with a roll barrel portion made of a material having high hardness and a high Young's modulus. Have concluded that this problem can be solved effectively. By adopting such a roll structure, not only can the bearing life of the chock be maintained, but also the effect of reducing the roll manufacturing cost can be obtained. The material of the roll barrel is Hv hardness.
It was also confirmed that 880 to Hv 1500 and Young's modulus in the range of 30,000 to 60,000 kg / mm ² were preferable.

Now, when manufacturing a large roll barrel unit integrally, the manufacturing cost is significantly increased by the usual manufacturing method. When this is manufactured by powder molding, in addition to the high raw material cost, it is difficult to perform embossing uniformly due to its large size, the molded body is easily broken, and the sintering process is also difficult. Extreme shrinkage distortion occurs at the time. For this reason, it becomes extremely difficult to manufacture a roll barrel of a desired size, which leads to a reduction in product yield and an increase in manufacturing cost. In addition, small voids are likely to remain inside the roll barrel after manufacture,
This also leads to a reduction in roll strength.

Therefore, the present inventors divided the roll barrel portion in the axial direction, that is, molded a plurality of columnar members in advance, and connected these molded members in the axial direction to sinter or The idea was to integrate by hot isostatic pressing. With such a small molded member, the compact is hard to collapse because of its denseness, and the shrinkage strain in the subsequent sintering process can be reduced, so that it is easy to take a roll barrel of high quality and desired dimensions. As a result, an improvement in product yield and a reduction in manufacturing cost can be achieved. In this way, the roll manufactured in the step of sintering two or more molded members in the axial direction after molding the columnar member,
Since the rolls are integrated, breakage of the rolls can be prevented, and scratches on the surface of the rolled cold-rolled steel plate can also be prevented.

The above-described roll structure will be described with reference to a specific example of FIG. In FIG. 1, a fitting hole 3 for fitting the roll barrel 1 is provided in the axial direction of the joining end 2 a of the roll neck 2, and the fitting hole 3 protrudes from the shaft end of the roll barrel 1. The joining projections 4 are fitted and fitted at the joining surfaces 5. The roll barrel 1 is made of a sintered body in which a plurality of cylindrical bodies (four in FIG. 1) are sintered and joined at the joint 6. As for the method of fitting the roll neck portion and the roll barrel, as shown in FIG. 1, the roll neck may be fitted with a fitting hole, or the roll barrel may be fitted with a fitting hole. The choice of which of these mating methods to use is
It may be determined in consideration of the use conditions such as the stress applied to the roll and the temperature. As the fitting method, a joining method such as a method utilizing a difference in thermal expansion coefficient between materials, a method of pressing in by pushing in an axial direction, and a method of combining these can be used.

The inventors also studied a method for obtaining a high joining strength of such a roll barrel portion without breaking even under high load rolling. As a result, for example, in manufacturing processes such as powder filling, embossing (CIP etc.), sintering, hot isostatic pressing (HIP), etc.
It is difficult to maintain the shape of the roll even after joining. On the other hand, if one or both of the sintering process and the hot isostatic pressing process are performed in a state where the columnar molded bodies are superimposed substantially coaxially, very good properties are obtained. Was obtained. If the material powder is treated at a high temperature in accordance with the latter method, the powder and the binder contained therein are firmly bonded, the shape of the roll is easily maintained, and the strength at the joint surface is increased.

The inventors have also studied the roll material. Conventionally, it has been known that by increasing the hardness of the roll, it is possible to suppress flaws and roll abrasion during rolling.However, according to studies by the inventors, if only the hardness of the roll is excessively increased, the breakage of the roll may occur. It has been found that it is easy to occur and cannot be put to practical use. Therefore, as a result of examining the material itself of the roll, a roll made of an oxide, a carbide, a nitride or the like also gives good results. In particular, a WC-based alloy made of WC (tungsten carbide) has a high hardness and a low Young's strength. The rate was large, and the roll strength was almost the same as that of steel. In addition, as a WC-based alloy, in addition to WC, Co, Ni,
It was also found that an alloy containing at least one of Cr, Ti and the like in an amount of 8 to 25% by weight was suitable.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a steel strip is cold-rolled using a composite roll will be described below. A powder obtained by mixing WC with 20% of Co is cold isostatically pressed (CIP) into a columnar shape, and 1120 ° C. × 2
After temporary sintering at hr, the workpiece was machined to smooth the peripheral surface and the joint surface, thereby producing six cylindrical bodies. These cylinders have an outer diameter of 450 mm for the barrel center (1b in FIG. 1).
× 4 pieces of 420mm length, outer diameter 280mm for barrel end ×
It consists of two 390mm long ones. These cylinders are stacked vertically (vertically) with their center axes aligned, and 1230 ° C x 2
hr sintering process and sinter bonding
Hot isostatic pressing was performed under the condition of 1000 kgf / cm ² . After that, the outer periphery is finished by grinding stone, the center part of the barrel is outer diameter 400 mm × length 1500 mm, the fitting part at both axial ends is outer diameter 250 m
A WC alloy roll barrel having dimensions of m × 350 mm in length, a Young's modulus of 48000 kgf / mm ² and a Vickers hardness of 980 was produced. On the other hand, the outer diameter is 350 mm x the inner diameter is 250 mm,
A neck made of cold die steel with a 351 mm fitting hole was made. By joining the joining projections at both ends of the roll barrel to the fitting holes of the neck with a fitting allowance of 0.1 mm and joining, the composite work roll for rolling shown in FIG. 1 was manufactured.

The obtained roll is assembled into the final stand of a five-stand cold tandem mill, and a load of 1000 to 1200 tonf is applied.
Under the above high load conditions, a low carbon pickled hot-rolled steel strip with a material thickness of 2.0 mm was rolled to a sheet thickness of 0.8 mm, and the mill exit speed was 1500 mpm.
Rolled a 13 ton steel strip. As a result, the roll was not damaged at all, and the surface of the steel sheet after rolling showed a good surface without any flaws.

For comparison, a powder obtained by mixing WC with 20% Co was cold isostatically pressed into a columnar shape, and four molded members having an outer diameter of 470 mm and a length of 440 mm were used for the center of the barrel. Two molded members having an outer diameter of 290 mm and a length of 410 mm were manufactured for the ends. After that, it was machined and sintered to try to hot isostatically pressurize, but in the process of arranging the compacted members after cold isostatic pressing, the corners of the compacted members were distorted. The roll had a shape, and had to be cut by half or more of the roll diameter by machining after the preliminary sintering, so that a roll having a desired size could not be manufactured.

As another comparative example, a sleeve having an outer diameter of 400 mm and a length of 375 mm was manufactured from a WC-based alloy obtained by adding 20% of Co to WC, and these four sleeves were arranged side by side on a steel arbor and mounted with a wedge-shaped ring. Rolls fixed by circumferential stress were produced. Using this roll, similarly, when the rolled steel strip was assembled into a tandem mill and cold rolled, streaks appeared on the entire surface of the steel strip corresponding to the mating surface of the sleeve. could not. In addition, the roll was damaged at the corner of the sleeve, and rolling was abandoned halfway.

As another comparative example, Young's modulus of silicon nitride is 29,000 kgf / mm ² , Vickers hardness is 1600, and outer diameter is
A sleeve having a length of 400 mm and a length of 375 mm was manufactured. Four sleeves were mounted side by side on a steel arbor, and a roll was fixed by applying compressive force from the side. Using this roll, similarly, when cold rolled by incorporating in a tandem mill,
The roll was damaged at the corner of the sleeve, and rolling was abandoned halfway.

[0022]

As described above, according to the present invention,
By effectively combining the integration by sintering and the compounding by fitting, it becomes possible to provide a large-sized roll applicable to cold tandem rolling of a metal strip at low cost. Further, according to the present invention, by using a WC-based alloy having a high hardness and a high Young's modulus for the barrel portion, it is possible to effectively prevent flaws on the surface of the strip after rolling, and further, to form a steel on the neck portion. By using this, it is possible to provide an inexpensive roll for metal strip rolling that does not cause roll breakage during rolling.

[Brief description of the drawings]

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

[Explanation of symbols]

 Reference Signs List 1 roll barrel 1a barrel end 1b barrel center 2 roll neck 2a neck end 3 fitting hole 4 joining protrusion 5 joining surface 6 sintered joint

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Yarida 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (56) References JP-A-4-361803 (JP, A) JP-A Heisei JP-A-63-288821 (JP, A) JP-A-55-144369 (JP, A) JP-A-63-195243 (JP, A) JP-A-51-30513 (JP, A) A) JP-A-50-120410 (JP, A) JP-A-8-73964 (JP, A) JP-A-60-261609 (JP, A) JP-A-11-147117 (JP, A) JP-A-11 -47807 (JP, A) JP-A-10-263627 (JP, A) JP-A-63-52703 (JP, A) JP-A-5-169114 (JP, A) Japanese Patent Publication No. 58-39906 (JP, B2) Japanese Patent Publication No. 60-1384 (JP, B2) (58) t.Cl. ⁷ , DB name) B21B 27/00 B21B 27/02 B22F 7/06

Claims (4)

(57) [Claims] 1. A composite roll in which a roll barrel and a roll neck are made of different materials, wherein the roll barrel is made of a sintered body in which two or more cylindrical bodies are connected in the axial direction. A composite roll for metal strip rolling, wherein a fitting hole for fitting the other shaft end is provided in the axial direction of one of the joining ends of the roll neck. 2. The composite roll according to claim 1, wherein a WC (tungsten carbide) alloy material is used for the roll barrel. 3. The composite roll for rolling a metal strip according to claim 1, wherein a steel material is used for the roll neck. 4. An alloy powder is formed into a cylindrical body, and two or more of the cylindrical bodies are superimposed substantially coaxially, and are sintered and / or sintered.
Alternatively, hot isostatic pressing is performed to form a roll barrel, and a fitting hole for fitting the other shaft end in the axial direction of one of the joining ends of the roll barrel and the roll neck is formed. And producing a composite roll for rolling a metal strip.