| 摘要 |
PURPOSE:To manufacture a projected bead removing type electric welded steel pipe with superior toughness at low temp. by heating and holding a continuously cast steel billet contg. specified percentages of C, Si, Mn, P and S as essential components under specified conditions. CONSTITUTION:A continuously cast steel billet consisting of, by weight, 0.01- 0.08% C, <=0.5% Si, <=1.6% Mn, <=0.008% P, <=0.008% S and the balance Fe with inevitable impurities or further contg. one or more among <=0.050% Nb, <=0.050% V, <=0.040% Ti, 0.001-0.0060% Ca and <=0.050% Al is formed. The billet is heated to >=1,250 deg.C and held at the temp. for >10hr. By the treatment, segregation is reduced to improve remarkably the toughness at low temp. |
