优化了海洋平台用D36钢的化学成分,设计了三种轧制工艺以及两种轧后热处理工艺,研究了不同轧制态和热处理态下该钢的显微组织和力学性能并确定了最佳的轧制工艺及后续热处理工艺,从而实现了生产工艺的优化.结果表明:该钢的优化成分 为0.11~0.12C,0.30~0.40Si,1.55~1.60Mn,≤0.020P,0.005S,0.03~0.06Al,0.045~0.048Nb,0.012~0.018Ti,0.13~0.20Cu, 0.18~0.25Ni,0.055~0.060V,优化轧制及后续热处理工艺为控轧+加速控制冷却轧制后,进行890℃×140 min正火(快速冷却至返红温度650℃)热处理;该工艺下生产的60 mm厚D36钢表面组织以铁素体+马氏体+贝氏体为主,心部组织以细小的铁素体+珠光体为主;其屈服强度为375 MPa,抗拉强度为530 MPa,-20℃冲击功为200 J左右.
The chemical composition of D36 offshore platform steel was optimized and the three kinds of rolling processes and two kinds of heat-treatments were designed.The microstructures and mechanical properties of the steel in different rolling states and heat-treatment states were studied.The optimal rolling process and subsequent heat-treatment process were determined,realizing the optimization of the production process.The results show that the optimal chemical composition of D36 steel was as follows:0.11-0.12C,0.30-0.40Si,1.55-1.60Mn,≤0.020P,0.005S,0.03-0.06Al,0.045-0.048Nb,0.012-0.018Ti, 0.13-0.20Cu,0.18-0.25Ni,0.055-0.060V.The rolling and heat-treatment process was that rolling with the controlled rolling and accelerating controlled cooling process followed by the normalization at 890 ℃ for 140 min then fast cooling to the re-reddening temperature of 650 ℃.With this process,the surface microstructure of D36 steel with 60 mm thickness was mainly consisted of ferrite,martensite and bainite and the core microstructure was of fine ferrite and pearlite;the yield strength and tensile strength of the steel were 375,530 MPa respectively,and the impact energy at -20 ℃ was around 200 J.
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