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S31042钢是一种重要的超临界和超超临界锅炉用钢。针对该钢持久塑性差的问题,采用扫描电镜和透射电镜研究了S31042钢在650℃持久前后的微观组织,主要探讨了析出相对持久塑性的影响。结果表明:持久1 608 h,S31042钢的塑性快速下降。而后塑性缓慢下降,并逐渐趋于稳定。S31042钢持久过程中主要的析出相为二次NbCrN和M23C6,长期持久会导致少量σ相和Cr3Ni2Si C的析出。S31042钢持久塑性显著下降的主要原因是由于M23C6在晶界上的析出。此外,链状M23C6、立方形M23C6以及未溶的Nb Cr N对S31042钢的持久塑性也有害。
S31042 steel is an important supercritical and ultra-supercritical boiler steel. In view of the poor ductility of the steel, the microstructure of S31042 steel at 650 ℃ was investigated by scanning electron microscopy and transmission electron microscopy. The effects of relative ductility on the ductility were discussed. The results show that the ductility of S31042 steels decreases rapidly for 1 608 h. The plasticity then slowly decreased and gradually stabilized. The main precipitated phase of S31042 steel is secondary NbCrN and M23C6 in the long-term process, and long-term persistence will lead to the precipitation of a small amount of σ phase and Cr3Ni2SiC. The main reason for the significant plasticity reduction of S31042 steel is due to the precipitation of M23C6 on the grain boundaries. In addition, chain M23C6, cubic M23C6, and undissolved NbCrN are also detrimental to the ductile plasticity of S31042 steel.