| 摘要 |
PURPOSE:To obtain a titled steel having good low temp. toughness down to the central part of the plate thickness while maintaining a low C equiv. by limiting a heating temp., rolling conditions and method, and force cooling conditions in the stage of subjecting a specifically composed steel to heating, rolling, force cooling, and tempering. CONSTITUTION:A steel contg., by weight, 0.03-0.20 C, 0.05-0.60 Si, 0.50-2.5 Mn, 0.005-0.10 Nb, and 0.005-0.1 Al, contg., if necessary, >=1 kind among <=1.0 Cr, <=2.0 Ni, <=1.0 Mo, <=0.1 V, <=0.15 Ti, <=0.5 Cu, and <=0.01 Ca and consisting of the balance Fe is heated to AC3-1,150 deg.C and is then subjected to rolling including >=2 passes of >=50% cumulative draft and >=0.50 rolling shape ratio expressed by the equation (R: radius of rolling roll, h1, h2: the plate thicknesses on the rolling inlet and outlet sides, DELTAh: h1-h2) between 850-730 deg.C rolling temp. The rolled plate is subjected to force cooling at >=0.5m<3>/m<2>.min water flow density until the center of the plate thickness attains <=250 deg.C right after rolling and is then tempered in the ferrite region. |
