JPS56131006A - Manufacture of seamless steel pipe - Google Patents

Abstract

PURPOSE: To reduce the number of sizes of the bloom as the blank material, and to efficiently manufacture the seamless metallic pipe in small diameter, by feeding a round blank pipe prepared through a piercing pass to the skew rolling mill, and by specifying the rolling reduction for the outer diameter by means of keeping the mandrel out of work at the early stage of the rolling work.

CONSTITUTION: A blank pipe P prepared through a piercing pass is fed to the skew rolling mill; a mandrel 12 is inserted into the blank pipe P which is thereup on rolled by a rolling roll couple 14. A disk roll couple 15 is arranged in the direction of the roll gap of the rolling roll couple 14. At performing this rolling work, the first roll couple group is set so as to give a rolling reduction ΔD₁≥35mm per one roll couple for outer diameter by means of keeping the mandrel 12 out of work; thereupon, when the feed of the blank pipe P to the first roll couple stagnates, the pusher is operated to trail the tail end of the blank pipe P so as to thereby start the rolling work. Hereupon, the rolling reduction for the outer diameter is designated by the equation ΔD₁=D_1-2-D₁.

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