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利用Formastor-D全自动热膨胀记录仪测定了三种改进型 9%Cr- 1%Mo耐热钢焊缝金属的连续冷却组织转变相图 ,并用光学显微镜和透射电镜分析了各种冷却条件下的组织转变特点。结果表明 ,在很大的冷却范围内 ,三种焊缝金属的奥氏体均只发生马氏体转变 ,只有当冷速足够慢时才发生先共析铁素体转变和共析转变。其中 ,含合金元素较少的 2号焊缝金属具有最快的先共析铁素体形成冷速。研究发现 ,三种焊缝金属的奥氏体均形成板条马氏体并具有高位错密度的亚结构 ,马氏体中含有自回火产生的Fe3 C沉淀相 ,马氏体板条间有残余奥氏体的存在。先共析铁素体沿原始奥氏体晶粒边界生长 ,形成网状结构。珠光体中的碳化物为粗大的颗粒状M2 3 C6沉淀物。
The phase transition diagram of the continuous cooling of three kinds of improved 9% Cr-1% Mo heat-resistant steels was measured by Formastor-D automatic thermal expansion recorder. The microstructure of the weld metal was analyzed by optical microscope and transmission electron microscope. Organizational change characteristics. The results show that austenite of all three weld metals undergoes martensitic transformation only within a wide range of cooling and pro-eutectoid ferrite transformation and eutectoid transformation occur only when the cooling rate is slow enough. Among them, No. 2 weld metal with less alloying elements has the fastest cooling rate of pro-eutectoid ferrite. It is found that the austenite of the three kinds of weld metal forms the lath martensite and has the sub-structure of high dislocation density. The martensite contains the Fe3 C precipitated phase produced by self-tempering. The martensite lath has Presence of retained austenite. First proeutectoid ferrite along the original austenite grain boundary growth, the formation of network structure. Carbides in the pearlite are coarse, granular M2 3 C6 precipitates.