PURPOSE: To prevent faulty biting and to obtain a seamless steel pipe excellent in quality, by rolling the end part of the pipe in tapered shape so that the thickness of the end part becomes thinner toward the pipe end, in the rolling stage by a piercing mill or elongator of Mannessmann type.
CONSTITUTION: As to the blank pipe whose end part is rolled in the tapered shape, in case of subjecting to elongation rolling successively, a reduction ratio of a sectional area of the pipe end is smaller than that of the central part of the pipe. Therefore, when the pipe end part is elongation rolled in tapered shape, the rolling load is managed with small load, so wears of tools are reduced and flows of the pipe is not generated. Further, the faulty biting and failing to roll caused by deteriorating the shape of flange parts are not taken place. Furthermore, at the time of rolling of the pipe end part in the tapered shape by the piercing mill or the elongator of Mannessmann type, with respect to the elongation rolling, as the material temp. is high and the rolling speed is slow, the control of the rolling to make the pipe end in the tapered shape is facilitated, the faulty biting and the faulty shape of the pipe end part are not generated.
MURAYAMA MASATOSHI
ITO KATSUYOSHI
| JPS59209414A | 1984-11-28 | |||
| JPS6116528A | 1986-01-24 |