| 摘要 |
PURPOSE:To obtain a steel pipe which effectively suppresses the occurrence of hydrogen type defects by disposing a hardening water tank and a tempering furnace in series between a run-out table provided to a finish rolling mill and a transfer table provided in parallel in the side surface part thereof. CONSTITUTION:A steel pipe rolled by a finish rolling mill 1 is received on a runout table 2. A hardening water tank 3 and a tempering furnace 4 are connected to the side face part in the position just before the table 2 in the direction intersecting orthogonally with the longitudinal direction of the table 2, and a rolling material cooling bed 5 is provided in parallel with these and is connected to a transfer table 6 in parallel with the table 2. Then, in spite of setting the direct hardening stop temp. at about above 200 deg.C, it is possible to perform directly tempering without lowering the steel pipe temp. down to about below 150 deg.C in the air cooling process after this, thus the improvement in treatment performance and the suppression of hydrogen type ultrasonic defects are made possible. |
