| 摘要 |
PURPOSE:To obtain the titled steel plate as rolled and to determine rationally a min. required alloy component system by controlling the specific parameter to decide a low yield ratio in material design of a high-tensile steel contg. component elements increasing the hardenability at the specific compsn. CONSTITUTION:A steel contg. 0.01-0.20% C, 0.07-2.0% Si, 0.8-2.5% Mn and 0.005-0.08% SolAl, contg. further 1 kinds among 0.10-0.50% Cu, 0.10-5.0% Ni, 0.05-2.0% Cr, 0.01-0.20% V, Nb, Ti, 0.0005-0.0030% B and 0.05-1.0% Mo if necessary, having the parameter P by the formula II satisfying the formula I and consisting of the balance Fe is prepd. Such steel is heated to 850-1,200 deg.C and is rolled down at >=50% cumulative draft in at least the unrecrystallized austenite region and is further rolled down at >=15% in the two-phase region of austenite + ferrite if necessary and thereafter the steel is air-cooled. |
