Method of width control in hot strip mill

Details Method of width control in hot strip mill Method of width control in hot strip mill

1980-09-08

1982-08-31

Larson, Lowell A.

Metal deforming

With use of control means energized in response to activator...

Including plural sensors or sensor responsive to comparison...

72234, B21B 1316, B21B 3712, B21B 3710

Patent

active

043465757

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to width control of a rolled metal product produced by a hot strip mill and more particularly to a method for reducing or eliminating variation in width resulting from the hot rolling.


BACKGROUND OF THE INVENTION

A hot rolling operation is carried out through a train of roughing rolls in which a plurality of vertical roll stands and a plurality of horizontal roll stands are arranged in series and alternately one after another. It has been the general practice in a rolling operation to set the roll gaps or the degrees of opening of the vertical roll stands at a desired roll opening prior to the feeding of the slab or material into the roll-stands, and such predetermined roll gaps are usually kept unchanged throughout the rolling operation for that material. Due to uneven distribution of temperatures or so-called skid marks in the slabs generated in the furnace, there is inevitably a possibility of variation in width of the rolled product such as strip and the like if such roll gaps are kept unchanged during the rolling operation. Because of this, in order to avoid the possibility of insufficient width in the rolled products, it has been the practice to intentionally add a substantial surplus width which would subsequently be trimmed to get a product having the desired dimensions. This procedure, however, results in substantial waste and reduction in yield.
In an attempt to eliminate or reduce variation in width of the rolled products due to such skid marks in the slab fed from the furnace, there has been proposed and disclosed the method for controlling the widths of materials to be rolled in the Japanese Patent Publication No. 26,503/1977 specification which comprises the steps of measuring temperature changes in a longitudinal direction of a material to be rolled upstream of the vertical roll stands, determining the deviation between a minimum temperature and a temperature at respective points of the rolled material, estimating variation in the material widths from the thus-obtained temperature deviation, determining a schedule for changing the roll gap or degree of opening of the vertical roll stands which is enough to compensate for the estimated variation in the material width, and controlling the roll openings of the vertical roll stands in accordance with the predetermined schedule for changing the roll opening during the rolling operation. This method is premised on the assumption that the cause of the width variation in a material is as follows.
That is, in a hot slab fed from the furnace, there would appear areas of a relatively high temperature and of a relatively low temperature alternately one after another in the longitudinal direction thereof under the effect of heat shielding due to the skid arrangement in the furnace. And, the relatively low temperature areas of the material or slab would have more resistance against the deformation than the relatively high temperature areas, with the result that a greater edging force is required in the relatively low temperature areas. On the other hand, since rigidity of the vertical rolls is relatively small, there would occur an effect of the large or small edging forces for these areas mentioned above, and therefore, it has been believed that the degree of width reduction by the vertical roll stands in the relatively low temperature areas would become smaller than that for the relatively high temperature areas, whereupon such variation might occur in the widths of the rolled bar or products.
The method of controlling the rolled product width according to the Japanese Patent Publication No. 26,503/1977 specification was on the assumption that such width variation would occur from the cause of uneven temperature distribution in the longitudinal direction of a slab to be rolled, and this led to adjusting the roll gap of the vertical rolls in accordance with the temperature variation existing in the longitudinal direction of the slabs or materials.
The well known prior methods of controlling the rol

REFERENCES:
patent: 3543548 (1970-12-01), Smith, Jr.
patent: 4063076 (1977-12-01), Morooka et al.

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