PRODUCTION OF PIPE WITH TWO FINS ON OUTSIDE SURFACE

摘要

PURPOSE:To economically produce the high-quality pipe with two fins by inserting an inside surface regulating tool into a circular shock pipe of the bore smaller than the diameter of a roll caliber, inserting the stock pipe into the caliber and bulging a part of the pipe wall into the gap between the roll flanges. CONSTITUTION:Two pieces of caliber rolls 10a, 10b are disposed to face each other by aligning the caliber center to a pass line so as to form a gap G between the flanges 11a and 11b thereof. The stock pipe which is circular in section and has the bore smaller than the diameter d0 of the caliber is inserted therein with the inside surface regulating tool 30 and is then inserted into the caliber to decrease the thickness thereof. A part of the pipe 21 decreased in the thickness is bulged into the gap G between the flanges 11a and 11b of the rolls 10a and 10b. The fins extending in the axial direction are formed in the two positions symmetrical in the circumferential direction. The large fin height is assured in this way by one pass and the formation of overlaps and inside surface piping defects is suppressed.