高强韧性海洋平台用E550钢板生产工艺研究

Research on production process of high strength and toughness E550 steel plate for offshore platforms

介绍了E550钢板的主要生产工艺和技术难点,通过理论分析设计了E550的成分体系,采用Thermal-Calc和经验公式,获得了其热力学相图和相变点温度等热力学数据。根据E550的热力学特性,设计了两阶段轧制工艺,精轧的终轧温度控制在再结晶温度附近,利用奥氏体再结晶充分细化晶粒。淬火奥氏体化温度选择为920℃,回火温度设计为630℃,利用碳化物的析出强化效果和缺陷密度变化的位错强化获得良好的强韧性匹配。50 mm厚钢板的淬火态1/4厚度处的微观组织为马氏体,中心的组织为马氏体和少量贝氏体的混合物。回火热处理后,马氏体板条界面减少,碳化物在马氏体板条界面析出,钢板1/4到中心的组织均匀化。30和50 mm厚E550钢板的力学性能达到了船级社标准要求,并有较大的富裕量。热输入能量为15和50 kJ/cm焊接后,钢板具有良好的强度性能,熔合线和热影响区的冲击功较高。

The main processes and technical difficulties in production of the E550 plate were introduced.The E550 composition system was designed through theoretical analysis.Some thermodynamics data,such as the thermodynamic phase diagram and the temperature at the phase transformation point were worked out by the Thermal-Calc and experiential formula.Based on the E550＇s thermodynamic properties,a two-stage rolling process was designed.In order to fully refine grains by austenite recrystallization,the final finishing rolling temperature was controlled to be close to the recrystallization temperature.The austenitizing and quenching temperature was selected to be 920℃ and the tempering temperature to be 630℃.A good match of strength and toughness has been gained through making use of the carbide precipitation and the defect density of dislocation.The microstructure is martensite at 1/4 of the thickness and martensite mixed with a small amount of bainite at the center of the 50 mm quenched steel plate.After tempering,the martensite lath interface was reduced,the carbide precipitated at the martensite lath interface,and the structure of the plate was homogenized in the area from the place at 1/4 of the thickness to the center.The mechanical properties of the E550 steel plates（30 and 50 mm thick） reached the classification society standards and had a certain amount of surplus capacity.Welded with 15 or 50 kJ/cm heat input,the steel has higher strength and higher impact energy in weld lines and the heat affected zone.