The Rolling Process Study and mechanical property of 460MPa Class Steel Plate used for Hull Structure

摘要

Targeted on grain refinement, the effects of different rolling processconditions on mechanical property of 460MPa class steel plate, in termsof tensile and yield strength, low-temperature toughness, arrestabilityand microstructure, are studied. The rolling process conditions aresurface-layer with ultrafine grains process (SUF) and traditional thermomechanical control process (TMCP). As for SUF process, better surfacestrength and toughness can be achieved. Yield strength is generallyhigher than 540MPa. -60°C impact value of SUF2 is higher than 280J.The surface nil-ductility transition temperature (NDTT) of SUFcondition have reached less than -80°C. The fine grain microstructureformed at the surface layer, which is about 4mm thick, contributes tobetter mechanical property than that in other layers. The microstructurevaries gradually from the surface to the centre. There are proeutectoidferrite and bainite at 1~4mm thickness of surface layer. Themicrostructure in the 4~10mm thickness layer consists of polygonalferrite and a considerable amount of bainite. As for the TMCP process,relatively homogenous strength and toughness can be achieved acrossthickness direction, featuring with higher strength and lower toughnessat the surface layer, and lower strength and higher toughness at centrelayer, when compared to that of SUF process. The microstructure of theTMCP sample varies gradually from the surface to the centre.