To provide a piercing method in the manufacture of a seamless steel tube having no flaw on the inner and outer surfaces.
In the piercing method of the seamless steel tube in a manufacturing method of the seamless steel tube, the generation of the flaws on the inner surface is prevented by preventing biting failure by arranging skew rollers and pinch rollers on a table in front of a piercer, advancing a raw material while rotating it and supplying the raw material while supporting its rotational force with piercing rolls. In the piercing method of the seamless steel tube in the above manufacturing method of the seamless steel tube, the generation of flaws on the outer surface generated by the difference between the advancing speed of the raw material and the speed of the rollers in piercing is prevented by detecting the load of the piercing rolls after a piercer is bitten and releasing the skew rollers and the pinch rollers.
NAKAMURA HIROSHI
MATSUI TOSHIKI