摘要
采用淬火膨胀仪模拟了9Ni钢的快速加热回火工艺,并结合显微组织观察、淬火后残留奥氏体含量的计算以及回火过程中热膨胀曲线的分析,研究了9Ni钢快速加热回火过程中组织的演变行为。结果表明:淬火终冷温度略高于M_f点时,淬火组织中存在少量的残留奥氏体,经快速加热后能够促进回火过程中逆转变奥氏体的生成;但当终冷温度过高时,残留奥氏体量大幅增加,反而会抑制逆转变奥氏体的形成;快速加热有利于马氏体的逆转变及碳原子在奥氏体中的富集,但这两种机制存在竞争关系,快速加热回火后组织中的奥氏体较少时,碳原子的富集会使其稳定性上升,反之则导致碳原子在奥氏体中的富集程度减弱,稳定性变差。
The rapid heating and tempering process of 9 Ni steel was simulated by means of quenching dilatometer, and the microstructure evolution behavior of the 9 Ni steel during rapid heating and tempering was studied by microstructure observation, the calculation of residual austenite content after quenching and the analysis of thermal expansion curve during tempering. The results show that a small amount of residual austenite exists in the quenched microstructure of the steel when the quenching end cooling temperature is slightly higher than the M_f point, which can promote the formation of reversed austenite during tempering after heating at a high rate. However, when the final cooling temperature is too high, the amount of residual austenite increases significantly, which will inhibit the formation of reversed austenite. Rapid heating is beneficial to the reverse transformation of martensite and the enrichment of carbon atoms in austenite. However, there is a competitive relationship between these two mechanisms. If the content of austenite in the microstructure after rapid heating and tempering is less, the stability of the martensite increases due to the enrichment of carbon. Conversely, the enrichment of carbon atoms in austenite decreases and the stability becomes worse.
引文
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