JPS5741809A - Manufacture of upset pipe - Google Patents

Abstract

PURPOSE: To apply an upsetting process during a rolling process, to simplify the constitution of an upset pipe manufacturing apparatus, and to improve the production efficiency, by installing a rolling-reduction changeable rolling apparatus in the line following a rolling mill of a seamless steel pipe rolling apparatus.

CONSTITUTION: At rolling a blank pipe 11 on a mandrel bar 12 with a roll 5 of a rolling mill into a prescribed wall thickness, the rolling work is performed at first by a roll position and a rolling reduction so as to give a large wall thickness to a length of a prescribed upset zone 14 from the pipe end 13; hereby, an upset zone 14 in a prescribed length with a large wall thickness is formed. Then, the roll position and rolling reduction in each stand are changed so as to give an aimed wall thickness at a point of time wherein the preset length position arrives and the roll is rotated at a relatively higher speed; then, the roll 5 is pressed in a direction for reducing the roll gap; these actions are controlled under a combination with an AGC system based on a gaugemeter. The conditions are next changed so as to open the roll gap of the roll 5, and the similar upset zone is formed in the rear end of the pipe.

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