| 摘要 |
PURPOSE:To prevent generation of cracks, and to enable the titled steel pipe to be mass produced at a low cost, by heating the round billet of the blank material and then by piercing it with the Mannesmann piercer whose roll gap and plug's forward slip are respectively set at a specified point. CONSTITUTION:The round billet comprising the sulfur free cutting steel is heated up to 1,200-1,300 deg.C; then, this billet is pierced with the Mannesmann piercer; in which, the roll gap Dg is set at a point by that the draft percentage represented by the formula I becomes <=10%, and the plug's forward slip (lead) l is set at a poit permitting the contact length X to be <=1/2 fraction of the diameter DB of the round billet. Next, the billet is processed in the following stretching and rolling gasses, and the seamless steel pipe of sulfur-free cutting steel is obtained. |
