温卷成形对2.25Cr1Mo0.25V钢圆柱壳组织和性能的影响

Effect of warm forming on microstructure and mechanical properties of 2.25Cr1Mo0.25V steel cylindrical shell

为了揭示2.25Cr1Mo0.25V钢制加氢反应器圆筒成形后的真实状态,采用高温拉伸试验、SEM、TEM和EDS对按照真实制造工艺温卷成形的圆筒厚向力学性能和显微组织分布情况进行了研究。结果表明,温成形后圆筒内显微组织和力学性能分布不均匀,圆筒表面碳化物密度高于心部碳化物密度,表面强度低于心部强度,屈服强度和拉伸强度分别降低3.9%～17.0%和4.8%～11.7%,断后伸长率变化幅度为-2.3%～8.7%,圆筒内最低伸长率为17.6%。温成形圆筒内组织分布不均匀主要是由于成形过程中的不均匀塑性变形对碳化物粗化和析出的促进作用的结果。不均匀软化是高温回火导致的M/A相分解以及不均匀碳化物演化对组织的沉淀强化和固溶强化削弱的结果。

High temperature tensile test and microstructure analysis based on SEM,TEM and EDS were conducted to investigate the realistic microstructure and mechanical properties distributions of 2.25 Cr1 Mo0.25 V steel cylinder in thickness direction.The results show that the microstructure and mechanical properties are inhomogeneous in the cylinder.The carbide density on the surface of cylinder is higher than that in the center,and the surface strength is lower than that in the center.The yield strength and tensile strength are reduced by 3.9%-17.0% and4.8%-11.7% respectively.The change range of the elongation after breaking is-2.3%-8.7%,and the minimum elongation in cylinder is17.6%.The inhomogeneous microstructure in cylinder after forming is induced by the synergistic action of high temperature tempering and plastic deformation.The inhomogeneous softening is caused by the decomposition of M/A phase during tempering,and the inhomogeneous reduction of both the precipitation and solution strengthening is resulted from the inhomogeneous carbide evolution during forming.