Manufacturing methods and seamless steel pipe of excellent seamless steel pipe to the inner surface smoothness

摘要

PROBLEM TO BE SOLVED: To manufacture a cold finished seamless steel tube excellent in tube internal smoothness at single cold drawing work. ;SOLUTION: A method for manufacturing a seamless steel tube excellent in internal smoothness is characterized in that the ratio between wall thickness and outside diameter (T/D) of the cold-finished steel tube is 20% or more and a lubricated tube stock is drawn subject to the following formula to be satisfied: Y≥A+5.5.exp(0.036.X) Here, Y shows wall thickness degree of processing (%), X die angle(°) and A constant number.;COPYRIGHT: (C)2003,JPO