Metal working – Method of mechanical manufacture – Roller making
Reexamination Certificate
1998-11-13
2002-04-23
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Roller making
C029S895213, C492S003000, C492S058000
Reexamination Certificate
active
06374494
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a composite sleeve roll constituted by hard alloys having high hardness, high Young's modulus and high rigidity and its fabrication method. Further, the present invention relates to a roll for cold-rolling a cold-rolled steel strip such as a stainless steel strip, a silicon steel strip, a bright finish steel strip or the like and to a rolling roll capable of producing a cold-rolled steel strip having a small amount of edge drop, a cold-rolled stainless steel strip and a bright finish steel strip having excellent surface brightness and a silicon steel strip having excellent magnetic properties with high advantage.
BACKGROUND ART
In the production of steel strip, steel wire or rod steel, for example, Sendzimir mill roll, wire mill roll and the like are used and with requests for high grade formation of steel material to be handled, energy conservation and so on, rolls with a material of hard alloys having high hardness and high Young's modulus and excellent in wear resistance have been developed and used. These hard alloys rolls are mainly small-sized rolls having a comparatively small diameter, for example, a roll diameter of about 20 through 80 mm, or a roll diameter of 50 through 150 mm and a roll length of about 100 through 200 mm in accordance with a shape of material to be handled. In recent years, large size formation of hard alloys rolls has been requested in view of quality improvement of steel material and a necessity for long time period continuous operation for reducing production cost.
Generally, a monolithic body of hard alloys is used in a Sendzimir mill roll mentioned above and a wire mill roll or the like is fabricated by exerting compressive force in an axial direction to a shaft portion and a sleeve having an inner diameter substantially equivalent to a diameter of the shaft portion and surrounding the shaft portion as a central axis or exerting compressive force in a circumferential direction by a wedge type ring or the like to thereby fixing the sleeve onto the shaft portion and carrying out surface-finish treatment thereon.
However, according to the conventional method of fabricating a composite roll in which such a sleeve made of hard alloys is fitted to the shaft portion, in fabricating a large-sized roll (normally referring to a roll having a diameter of 150 mm or more and a length of 500 mm or more), the sleeve is fabricated by subjecting metal powder of hard alloys to rubber molding, sintering the metal powder as one piece hollow member having a hollow central shaft portion (with a diameter equivalent to the diameter of the shaft portion), subjecting the sintered body to hot isostatic press (HIP treatment) and thereafter machining the pressed body. Although the fabricated sleeve is fixed to the shaft portion, the hollow member is large-sized and is particularly made of the material of hard alloys and therefore, there cause frequently cases where large strain is generated in the material in subjecting the material to a heat treatment such as sintering or the like which makes difficult succeeding fabrication. Further, although in forming the hollow member by rubber molding, metal powder of hard alloys is packed sufficiently densely around a core rod having a diameter equivalent to that of the shaft portion and thereafter the core rod is drawn out to thereby form a mold body, when the hollow member is large-sized, the core rod is difficult to draw out and there pose frequently problems where the shape of the mold body is significantly deteriorated, a force more than necessary is needed and the like thereby causing difficulty in operational performance.
Next, an explanation will be given of a method of fabricating a cold-rolled stainless steel strip and a description will be given of problems in a method of fabricating stainless steel strip when large-sized rolls are used. Conventionally, a cold-rolled steel strip of stainless steel has been fabricated by the steps of annealing and pickling a hot-rolled strip, cold-rolling the hot-rolled strip by a Sendzimir mill or the like using a work roll made of a steel series alloy having a work roll diameter of 150 mmø or smaller, subjecting the cold-rolled material to finish annealing and pickling or finish bright annealing and rolling the annealed material by finish temper rolling with a reduction ratio of 1.2% or less. The cold-rolled stainless steel strip fabricated through these steps is frequently used with a surface thereof as fabricated in the case of a ferritic stainless steel represented by, for example, SUS 430 and excellent surface brightness is requested in a product after having been subjected to the finish temper rolling. Meanwhile, in the case of an austenitic stainless steel represented by SUS 304, buffing is frequently carried out after the finish temper rolling and excellent surface brightness needs to be shown after the buffing. In the meantime, in recent years, in order to efficiently fabricate the cold-rolled stainless steel strip, a method of continuous cold rolling in one direction by a tandem cold mill using large-sized work rolls of 150 mmØ or larger is being adopted. For example, Japanese Unexamined Patent Publication No. 8-39103 discloses a technology in which work rolls of WC series hard alloys are used in at least one stand in a tandem cold mill by which production efficiency is promoted and surface brightness of cold-rolled stainless steel strip is promoted. However, according to the method, there pose problems in which not only the surface brightness of the cold-rolled stainless steel strip has yet to reach a sufficient level but also the surface brightness is deteriorated with rolling time period or a work roll may be broken under certain circumstances. Further, there poses also a problem in which the cost per se of the roll is high.
Next, an explanation will be given of a method of producing a grain-oriented silicon steel strip and a description will be given of problems when the grain-oriented silicon steel strip is produced by using large-sized rolls. Conventionally, a cold-rolled steel strip of grain-oriented silicon steel has been fabricated by the steps of annealing and pickling a hot-rolled steel strip, successively cold-rolling the pickled strip by a tandem mill using high alloy steel work rolls by twice or more interposing intermediate annealings and thereafter subjecting the rolled strip to decarburization annealing and finish annealing. It is known that when the silicon steel strip fabricated through these steps is cold-rolled without removing scale after the intermediary annealings, the surface roughness of the steel strip is enlarged and adverse influence is effected on magnetic properties. Therefore, grinding is carried out by using a grinding belt after the intermediary annealing and before the successive cold-rolling. Further, the grain-oriented silicon steel strip is provided with extremely high deformation resistance since 2.5 through 4.0 wt % of Si is normally added and when the rolling is carried out under high load and high surface pressure, there pose problems in which the rolls are made eccentric, the cylindrical shape cannot be maintained, in respect of the shape of the steel strip, edge drop is particularly enlarged, trimming margins on both ends of strip are increased and the yield is deteriorated. Further, according to the conventional rolls, there pose problems in which not only the surface roughness of the grain-oriented silicon steel strip after cold-rolling has yet to reach a sufficient level but also the surface roughness is deteriorated with the rolling time period or the work roll may be destructed under certain circumstances. Further, there poses also a problem in which the cost per se of the roll is high.
Firstly, it is an object of the present invention to provide a method of fabricating a composite sleeve roll having no strain of material mentioned above with excellent operational performance when a composite sleeve roll having high hardness and high Young's modulus and excellent in
Fukuhara Akihiko
Gamo Nobuaki
Kano Hirotaka
Kenmochi Kazuhito
Sonobe Osamu
Cuda Rosenbaum I
Kawasaki Steel Corporation
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