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本文初步讨论的问题:通过光学显微镜、X 射线衍射、电子显微镜(透射和扫描电镜)、紧凑拉伸等试验方法研究了55 SiMnMo 钢在正火状态下的上贝氏体形态,以及回火转变对其机械性能的影响。根据试验,在中碳合金钢中经900℃0.5小时奥氏体化后空冷所出现的上贝氏体由铁素体和30～35%富碳奥氏体片层相间组成。经简易膨胀仪测定,析出碳化物的回火转变温度约为400℃,此时金相组织变为由铁素体、碳化物和5%奥氏体组成,作者称这种形态为回火贝氏体。在发生回火转变时,裂纹扩展速率(da/dN)随回火温度增加而增加,在400℃时达最大值;断口的扫描电子金相从准解理型过渡到解理型。
The problems discussed in this paper are as follows: The upper bainite morphology of 55 SiMnMo steel under normalizing conditions was studied by optical microscope, X-ray diffraction, electron microscopy (transmission and scanning electron microscopy), compact tensile test and so on. Impact on its mechanical properties. According to the test, the upper bainite, which appears after air-cooling austenitizing at 900 ° C for 0.5 hours in medium-carbon alloy steel, consists of ferrite and 30-35% carbon-rich austenite sheets. Measured by a simple dilatometer, precipitation of carbide tempering transition temperature of about 400 ℃, then the microstructure becomes ferrite, carbide and 5% austenite, the author said the morphology of tempered shell Body. The crack growth rate (da / dN) increases with the increase of tempering temperature and reaches the maximum at 400 ℃. The scanning electron microstructure of the fracture transitions from quasi-cleavage to cleavage.