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采用电子光学等分析手段和机械性能试验方法,测定了不同热处理状态下65Cr4W3Mo2VNb(简称65Nb)钢的各种显微组织参量和机械性能。根据试验结果,从合金化、热处理和冶金质量的角度,探讨了影响强度、韧性和疲劳性能的组织因素。得出如下主要结果:(1)Nb的作用在于既能生成稳定的NbC,又可溶入其它碳化物中,从而影响相变过程和相变组织,提高钢的强韧性和工艺性能。(2)韧性第二相和基体的塑性对K_((?))、α_k值起有利影响,而强度主要受碳比物弥散强化所控制,细化晶粒则对两者均有益。工艺——性能曲线上的峰值或谷值,是由于在相变过程中不同强韧化机制。(3)冶炼方法对拉伸性能无甚影响。但电渣钢的韧性和抗疲劳性能比电弧钢高。(4)△K_(th)对微观组织比较敏感.而中速区的(da)/(dN)则主要取决于基体的韧性。
The microstructure parameters and mechanical properties of 65Cr4W3Mo2VNb (65Nb) steel under different heat treatment conditions were determined by means of electronic optics and mechanical properties test. According to the experimental results, the organizational factors affecting the strength, toughness and fatigue properties were discussed from the aspects of alloying, heat treatment and metallurgy quality. The main results are as follows: (1) The role of Nb is to produce stable NbC and other carbides, which will affect the phase transformation process and phase transformation and improve the toughness and workability of the steel. (2) Toughness The plasticity of the second phase and the matrix have an effect on K _ ((?)) And α_k values, while the strength is mainly controlled by the diffusion strengthening of the carbonaceous material. Grain refinement is beneficial to both. The peak-to-valley value on the process-performance curve is due to the different toughening mechanisms during the phase change. (3) smelting method has no effect on the tensile properties. But the electroslag steel toughness and fatigue resistance than arc steel. (4) △ K_ (th) is more sensitive to the microstructure, while (da) / (dN) in the medium speed area depends mainly on the toughness of the matrix.