Study Of Microstructure And Property For Q460Heavy Plate With TMCP Process

High strength low alloy steel plates are mainly used in machinery and equipmentmanufacturing industry, a amount of prime high strength extra-thick plates are needed urgentlyin order to improve the overall level and the market competitiveness of China’s machinerymanufacturing industry and meet the engineering machinery development needs aboutlargeness and light weight. The traditional high strength extra-thick steel plates are producedmainly by moulded casting-rolling-quenching and tempering process, the deficiencies lie in thehuge energy consumption, high alloy cost, long production cycle, cracks and surface defectsshowed easily etc. The research of this paper is aimed at perfecting the basic theory research ofa new technology on high strength extra-thick steel plates based on development andapplication of this technology, combining the high strength and low alloy structure steelresearch task of Wuhan Iron and Steel (Group)Corpo..According to the characteristics of TMCP process, the chemical composition of Q460extra-thick steel plates is designed, taking obtaining ferrite/bainite as the main line andconsidering the mechanical and useness properties synthetically; the phase transformation rulein continuous cooling process of Q460steel plates is researched by numerical simulationcalculation method, austenite grain growth behavior, solid solution and precipitation behavior ofmicro alloy elements and high temperature thermo-plasticity in Q460steel plates are researchedthrough this experiment in order to guide the follow-up experiments; the impact of controlledrolling process and cooling process after rolling on the structure properties is researched byindustry experiment. Industrial test and process parameters are designed optimumly in theguidance of experimental test data.The steel plates have good uniformity of mechanical properties, the yield strength, tensilestrength, elongation after breaking and impact toughness in the width direction do not changebasically, those properties of the central part in the thickness direction decrease, the yieldstrength decreases30MPa, the tensile strength40MPa and the elongation5%, but a amount of surplus has produced as standards requirement, the structures of steel plates including ferrite andbainite are homogeneous. A little of band bainite and pearlite structures close to the central partof thickness direction present because of precipitation, the number of precipitation shape ismore, the shape spheric and the distribution more homogeneous. The structures and propertiesof Q460extra-thick steel plates all meet the design requirements, can replace traditionalquenching and tempering process and have theoretical and practical value.