PURPOSE: To correct the thickness deviation of a tube stock after rolling by making the outside surface on the backside of a plug into a reeling part which is composed of a concave hyperboloid of revolution and making the distribution in the direction of pass line of a gap which is formed between the reeling part and a rolling roll uniform.
CONSTITUTION: Conical rolling rolls 31A, 31B are arranged inclining to the pass line and crossing their axes at a crossed axes angle γ. The plug 34 is arranged between the rolling rolls 31A, 31B, the skew rolling of a hollow tube stock 32A is executed by the roll gap E between gorge parts and, after expanding and rolling, the hollow tube stock 32B is obtained. The outside surface on the side of the front end of the plug 34 is taken as a working part 34A. The outside surface on the side of the rear end is made into the reeling part 34B which is composed of the concave hyperboloid of revolution and the distribution in the direction of pass line of the gap which is formed between the rolling rolls 31A, 31B and the reeling part 34B is made uniform. Since the parallel part is formed by the reeling regions, thickness deviation is corrected.
SHIMIZU TETSUO
TOYOOKA TAKAAKI
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