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采用1 kW横流CO2激光器对工业用半钢、无限冷硬铸铁及高速钢3种轧辊试样进行表面激光处理。用金相显微镜、扫描电子显微镜、能谱仪及显微维氏硬度计等对激光处理表面进行观察和测试。结果表明,3种试样的横截面组织由熔凝区、相变区、热影响区和原始组织4部分组成,激光扫描后的熔凝区硬度低而相变区的硬度高;试样经540℃×1 h回火后由于残留奥氏体转变使熔凝区的硬度有不同程度的上升,而相变区的硬度由于马氏体过饱和度的下降硬度反而下降;熔凝区内有大量的细点状FeS及MnS夹杂物;与含碳量较低的半钢和高速钢不同,无限冷硬铸铁轧辊的熔凝区内及其周围产生了热裂纹。
A 1 kW cross-flow CO2 laser was used to laser surface treat three kinds of roll samples of industrial semi-steel, infinite chilled cast iron and high-speed steel. The laser-treated surfaces were observed and tested with a metallographic microscope, a scanning electron microscope, an energy dispersive spectrometer and a micro-Vickers hardness tester. The results show that the cross-sectional structure of the three samples consists of four parts: the melting zone, the phase transition zone, the heat-affected zone and the primary structure. The hardness of the laser melting zone is low and the phase transition zone is high. After the tempering at 540 ℃ for 1 h, the hardness of the melting zone increases due to the residual austenite transformation, while the hardness of the phase transition zone decreases due to the decrease of the supersaturation degree of martensite. In the melting zone, A large number of fine FeS and MnS inclusions; unlike semi-steel and high-speed steels with lower carbon contents, hot cracks are generated in and around the melting zone of an infinite chilled cast iron roll.