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利用金相显微镜、扫描电镜和透射电镜等研究了1Cr12Ni3Mo2VN耐热钢的回火工艺,结果指出试验钢产生第一类回火脆性的主要原因是马氏体板条界存在聚集长大的Fe_3C及M_3C脆性相,导致冲击韧性显著下降。Mo_2C与基体处于共格状态,使基体周围晶格产生很大的静畸变是次要原因;产生第二类回火脆性的原因,一是由于碳化物M_(23)C_6沿原奥氏体晶界和马氏体板条界迅速聚集并粗化,二是板条间残余奥氏体膜因碳贫化而发生热失稳分解。结合技术协议要求,为了有利于组织的稳定性,本试验钢的最佳回火工艺为580℃×2h空冷。
The tempering process of 1Cr12Ni3Mo2VN heat-resistant steel was studied by metallographic microscope, scanning electron microscope and transmission electron microscope. The results show that the main reason for the first type of temper brittleness is the presence of aggregated Fe3C in martensite lath and M_3C brittle phase, resulting in a significant decrease in impact toughness. Mo_2C and the matrix are in a coherent state, so that the crystal lattice around the substrate produces a large static distortion is the secondary reason; produce the second type of temper brittleness reasons, first, as the carbide M_ (23) C_6 along the original austenite Boundaries and martensite lamellae rapidly gather and coarsening, and secondly, the residual austenite film between the laths undergoes thermal destabilization due to carbon depletion. Combined with the requirements of the technical agreement, in order to facilitate the stability of the organization, the optimal tempering process of this test steel is air cooling at 580 ℃ × 2h.