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本文通过六炉试验钢研究了铬对钢的持久强度、显微组织、组织稳定性及抗氧化性能等的影响。钢经过正火和高温回火后,在650℃下进行了持久强度和长期时效试验。应用光学显微镜和透射电镜观察钢的显微组织和贝氏体回火组织的精细结构。并对电解沉淀相进行X射线衍射相分析和化学定量相分析。试验结果表明,含4.5～5.5％Cr钢经过正火热处理后,获贝氏体组织。但是,随铬含量的提高,马氏体出现并逐渐增多,当铬量增至8.96％时,钢的组织为马氏体加少量δ-铁素体。由于δ相中没有碳化物析出和由于随着钢中铬量的增加,碳化物在回火和时效过程中聚集粗化较明显,使热稳定性降低,从而导致热强性的降低。然而,随着铬含量的提高,钢的抗氧化性和耐腐蚀能力亦随之提高。
In this paper, the effect of chromium on the long-term strength, microstructure, tissue stability and oxidation resistance of steel was studied by six furnace test steels. After normalizing and tempering of steel, the steel was tested for long-term strength and long-term aging at 650 ° C. The microstructure of the steel and the microstructure of the bainite tempered microstructure were observed by optical microscope and transmission electron microscope. The precipitated phase was analyzed by X-ray diffraction and chemical quantitative phase analysis. Test results show that, with 4.5 ~ 5.5% Cr steel after normalizing heat treatment, by bainite. However, with the increase of chromium content, the martensite appeared and gradually increased. When the chromium content increased to 8.96%, the microstructure of the steel was martensite plus a small amount of δ-ferrite. Due to the absence of carbide precipitation in the δ phase and due to the increased amount of chromium in the steel, the coarsening and coarsening of the carbide during tempering and aging are more pronounced, lowering the thermal stability, resulting in a decrease in the thermal strength. However, with the increase of chromium content, the oxidation resistance and corrosion resistance of steel also increase.