JPS55122601A - Blooming method for raw steel shape - Google Patents

Abstract

PURPOSE: To make possible maximum breadth-reduction without causing distortion of the material to be rolled, by determining the relation between the as-roll length and the reduction ratio quantitatively in breadth-reduction rolling after thickness- reduction rolling in the latter term of steel ingot rolling, then by rolling the material to be rolled at a reduction ratio of limited distortion.

CONSTITUTION: In the latter term of the pass schedule of a raw steel shape (material to be rolled) 3, strong breadth-reduction is completed by two passes through grooves II of rolls 1, 2 and when over fillings 4, 4 and spread are developed, the material is treated as follows: In giving breadth reduction by passing through the groove I of the rolls 1, 2 a standard signal for screw down position is fed to a screw-down-position-control unit 8 so that a control unit 16 may reach the maximum reduction ratio of a distortion limit curve, and a screw down device 7 is automatically operated by the unit 8 in order to set a reduction ratio. Then a necked volume signal of pulses 9, and the unit 16 gives the screw down position standard signal for increasing the degree of the roll opening to the unit 8 so as to give limit distortion in terms of computed as-roll length. The unit 8 operates the unit 7 to increase the degree of opening so as to give a reduction ratio for the limited distortion, thereby preventing the occurrence of the distortion.

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