PURPOSE: To provide a method for rolling a seamless steel tube of a high Cr ferritic steel pipe containing Mo, W and having high creep strength.
CONSTITUTION: In rolling of a seamless steel tube made of high Cr ferritic steel contg. Mo, W, as necessary, one or more kinds of Nb, V, B, Ni, the base stock is heated to 1000-1250°C, at the time of drawing it by skew rolling after piercing, rolling starting temp. is defined 1000-1200°C, the working ratio of drawing/rolling is controlled ≤0.5 in terms of strain that is expressed by the equation by using thicknesses and lengths before and after rolling. In this way, even when delta ferrite remains in the base stock, the generation of crack during rolling is prevented. Consequently, as for the high Cr ferritic steel contg. Mo, W, the seamless steel tube is rolled without generating the crack due to the delta ferrite.
NARASAKI KOJI
OGAMI MASAHIRO
