Wear-resistant compound roll

Details Wear-resistant compound roll Wear-resistant compound roll

1988-11-22

1990-09-25

Eley, Timothy V.

Metal working

Means to assemble or disassemble

Puller or pusher means, contained force multiplying operator

29132, 164 98, B21B 3108

Patent

active

049584227

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a wear-resistant compound roll for hot or cold rolling and a method of producing it.


BACKGROUND OF THE INVENTION

Widely used a rolls for rolling mills are compound rolls produced from cast iron by a centrifugal casting method. These compound rolls are those having a structure consisting of an outer layer made of a cast iron material in which a lot of highly wear-resistant carbides are precipitated, and an inner layer made of gray cast iron or ductile cast iron having large toughness. In this production method, however, only limited types of materials can be used for outer layers and inner layers.
Carbides of such elements as W, V, Nb, Ti, Ta, Zr, Hf, etc. have as high a Vickers hardness Hv as 2000 or more, and the inclusion of these carbides in outer layers is highly effective to increase the wear resistance of rolls. However, it is practically impossible to produce a compound roll comprising an outer layer precipitated with the above carbides and an inner layer strongly bonded thereto by a centrifugal casting method.
The reason for it is that since carbides formed from these elements have different specific gravities from that of a melt, they tend to be segregated due to a centrifugal action in the casting process. In addition, some of these elements are vulnerable to oxidation, making it extremely difficult to conduct melting, casting and bonding to the inner layer in the air. Further, in the centrifugal casting method in which gray cast iron or ductile cast iron containing graphite precipitates is used for the inner layer to provide it with sufficient toughness, when the outer layer contains a large amount of elements likely to form white cast iron, the formation of graphite in the inner layer is suppressed because of some components dissolved from the outer layer into the inner layer, making the inner layer brittle. In particular, since the carbides tend to be concentrated in a boundary between the inner layer and the outer layer, the boundary becomes brittle, making it likely that the outer layer peels off from the boundary.
In addition, when gray cast iron or ductile cast iron is used for the inner layer, the inner layer's tensile strength is at most 55 kg/mm.sup.2 or so, and its elongation is less than 1%. If higher tensile strength and elongation are to be obtained, the inner layer should be made of steel materials. However, this is difficult in the centrifugal casting method. This is due to the fact that since the inner layer has a higher melting point than the outer layer when steel is used for the inner layer, the outer layer is melted during the casting of the inner layer, thereby providing, as a final solidification phase, a boundary portion made of a mixture of both layers, this boundary portion being a site likely to generate cast defects.
Accordingly, the centrifugal casting method has been unable to provide a compound roll comprising an outer layer containing a large amount of carbides of the above-described elements and an inner layer having a tensile strength of 55 kg/mm.sup.2 or more and an elongation of 1.0% or more, both layers being strongly bonded to each other.
On the other hand, to increase the efficiency of rolling by increasing an amount of rolled products produced in a single roll repair cycle and to improve the size precision of rolled products, it has become necessary to drastically increase the wear resistance of rolls. At the same time, the improvement of size precision of rolled products makes it necessary to exert a bending force to both extending portions of a roll shaft in an opposite direction to the direction of deflection of the rolls caused by a rolling force, and the reduction of number of roll stands necessary to complete rolling makes it necessary to increase pressure applied to the rolls in a roll stand. This inevitably increases a bending force applied to both extending portions of the roll shaft, which in turn requires that the roll shaft has higher strength. However, in a roll in which an outer layer

REFERENCES:
patent: 3455372 (1969-07-01), Yamamoto
patent: 3968551 (1976-07-01), Miyashita
patent: 3997370 (1976-12-01), Horvath, Jr. et al.
patent: 4165407 (1979-08-01), Endoh et al.
patent: 4484959 (1984-11-01), Boucher et al.
patent: 4547470 (1985-10-01), Tanase et al.
patent: 4618540 (1986-10-01), von Holst et al.
patent: 4721153 (1988-01-01), Sano et al.
patent: 4726417 (1988-02-01), Sano
patent: 4839949 (1989-06-01), Sobue et al.

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