PURPOSE: To produce rough billets for shapes at high efficiency and stabke quality, by setting up and down in the widthwise direction of flat billet, and passing several times the box caliber by means of two-stage caliber rough rolling mill.
CONSTITUTION: A flat billet 1 measuring 2.0≤ width W/thickness t≤6 is preliminarily heated uniformly, and is set up and down in the widthwise direction to be processed by edging-rolling by passing 5W7 times with rough rolling mill. In this case, as a rolling mill, a two-stage caliber rolling mill having upper and lower rollers having approximately trapezoidal shape satisfying the relations of formulas IWIII. The billet 1 is rolled at draft satisfying the relation of formula IV. AS a result, the sectional middle part of the billet is hardly deformed owing to local deformation of the billet 1 or local metal flow, and the upper and lower ends are deformed along the roll caliber, so that a desired dog-bone shape rough billet 3 is obtained. Since this method can be use continuous cast slag and bloomed slag as material, beam blanks of varied kinds and small qunatity each may be produced without largely changing the production schedule of steel works.
KOSHIDA OSAMU
NAKAYAMA SHIYOUICHI
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