| 摘要 |
PURPOSE:To obtain rolled and refined steel of a low alloy having less internal defect caused by hydrogen by casting the molten low alloy steel of a specific compsn. continuously with a limited amt. of hydrogen therein then subjecting the steel to slow cooling, heating, rolling, quick cooling and tempering under limited conditions. CONSTITUTION:The steel contg. <=0.3% C, <=0.7% Si, <=2.5% Mn, <=0.025% P, <=0.020% S, <=10% Ni, respectively <=2.5% >=1 kind among Cr, Mo, Cu, W and <=1 kind among B, V, Nb, Ta, Ti, rare earths, Al, Ca is cast continuously with the amt. of water in the molten steel controlled to <=5ppm. Such ingot is held and cooled slowly for >=5 hours below the Ar1 point and is cooled down to <=300 deg.C. The ingot is heated above the Ac3 point and is rolled at >=5% draft in an unrecrystallization temp. region down to the Ar3 point below 900 deg.C. The rolled steel is cooled quickly down to 400 deg.C at >=1 deg.C/sec and is tempered in an early time. According to this method, the continuously cast, rolled and refined steel material having less internal defects is obtained without dehydrogenation annealing. |
