| 摘要 |
PURPOSE:To produce a clad steel plate having a high fatigue limit ratio and excellent formability by pouring molten steels having respectively different compsns. from two nozzles into a continuous casting mold to form a billet having a three-layered structure and rolling the billet into a plate shape. CONSTITUTION:A molten steel 3 having the compsn. contg. 0.0015-0.25% C, 0.003-2.0% Si, 0.1-2.0% Mn, 0.0001-0.1% Al, <0.015% S and 0.001-0.03% REM or 0.001-0.15% Zr and contg. 1.3-5.0 REM/S and 2.0-10.0% Zr/S is poured into a tundish 2 having a gate 1. The molten steel is poured downward 9 through a long immersion nozzle 4 into a continuous casting mold 5. An additive 14 is added to a molten steel 6 overflowing from the gate 1 and a molten steel 6 incorporated therein with 0.03-0.25% C and one or >=2 kinds among 0.005- 0.05% Nb, 0.02-0.2% V and 0.005-0.20% Ti is poured upward 8 through an immersion nozzle 7 into the mold. A three-layer clad continuous casting billet 10 in which the molten steel 3 forms an inside layer 13 and the molten steel 6 forms an outside layer 12 is manufactured and is rolled to a clad steel plate. |
