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研究海洋石油平台专用H型钢(55C钢)轧后快冷产生的显微组织特征及其对力学性能的影响,探索实际生产中提高大尺寸厚壁H型钢强韧性的有效途径。测定了55C钢的动态CCT曲线;结合生产现场实际,通过优化控轧控冷工艺参数,特别采用比空冷和风冷快的轧后冷却,对试验钢进行了试轧;对轧后试样进行了力学性能测试、显微组织观察以及晶粒大小的测定。试验结果表明,轧制工艺参数特别是轧后冷却工艺对55C钢的显微组织和力学性能具有重要影响。采用适宜的终轧温度、道次变形量以及提高轧后冷速可以获得铁素体、珠光体和粒状贝氏体混合组织,使55C钢的强度得以大幅提升,获得良好的强韧性配合。通过轧后快冷获得高强韧性的贝氏体组织和细化晶粒都是大尺寸厚壁H型钢中重要的强韧化机制。55C钢的TMCP工艺(Thermo MechanicalControlled Processing)具有较宽的终轧温度和道次变形量范围,可根据不同的使用性能要求选择轧制工艺参数。
The microstructure characteristics and its effect on the mechanical properties of H-shaped steel (55C steel) after offshore rolling are studied. The effective ways to improve the toughness of large-size thick-wall H-section steel in actual production are explored. The dynamic CCT curve of 55C steel was measured. According to the actual production site, the test steel was tested by optimizing the process parameters of controlled rolling and controlled cooling, especially after the cooling after rolling, Mechanical properties testing, microstructure observation and determination of grain size. The test results show that the rolling process parameters, especially after rolling cooling process 55C steel microstructure and mechanical properties have a significant impact. Adopting appropriate finishing temperature, pass deformation and cooling speed after rolling can obtain mixed structure of ferrite, pearlite and granular bainite, so that the strength of 55C steel can be greatly improved and good toughness is obtained. Obtaining high strength and toughness bainite structure and grain refinement through rapid cooling after rolling are all important toughening mechanisms in large-size thick-wall H-section steel. The 55CP steel TMCP process (Thermo Mechanical Controlled Processing) has a wide range of finish rolling temperature and pass deformation, according to the different performance requirements of the choice of rolling process parameters.