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以高、中、低3种铌含量的S31042耐热钢作为试验钢,研究了铌含量对S31042钢中析出相及持久性能的影响。结果表明:S31042钢时效处理后,钢中主要含有M_(23)C_6相、Z相和MX相;当时效时间达到10 000 h时,钢中发现了σ相的存在。铌含量对S31042钢中析出相的种类和M_(23)C_6相的含量影响不大,对含铌相含量的影响显著,随着铌含量的升高,Z相+MX相含量明显增多。700℃持久寿命并未随铌含量的升高而单调增加,而在中限铌含量出现最大值,高铌钢中未固溶的粗大一次析出相是造成持久寿命降低的主要原因。
S31042 heat-resisting steel with high, medium and low niobium content was used as the test steel to study the effect of niobium content on the precipitated phase and the permanent property of S31042 steel. The results show that the steel contains mainly M_ (23) C_6 phase, Z phase and MX phase after S31042 steel aging treatment. When the aging time reaches 10 000 h, the existence of σ phase is found in the steel. The content of niobium has little effect on the type of phase precipitated in S31042 steel and the content of M_ (23) C_6 phase, but affects the content of niobium phase significantly. With the increase of niobium content, the content of Z phase and MX phase increases obviously. The long life at 700 ℃ did not increase monotonically with the increase of niobium content. However, the maximum primary niobium content appears, and the primary undissolved phase in high Nb steel is the main reason for the decrease of long-term life.