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采用中频感应加热炉对建筑用Q550D钢进行了不同工艺的回火处理。采用光学显微镜对显微组织进行了观察,对冲击功、硬度进行了检测,研究了回火时间和温度对组织和性能的影响。结果表明,当回火温度为200℃时,感应回火组织为回火马氏体,随着保温时间的增加,碳化物析出增多,马氏体逐渐分解,冲击功逐渐升高,硬度则逐渐降低;在200℃回火保温时间为10 min时,组织由低温感应回火时的回火马氏体逐渐向中温感应回火时的回火托氏体转变,随着回火温度升高,碳化物从马氏体板条中析出并长大,马氏体充分分解,组织趋于均匀化,冲击功则先提高,当回火温度超过350℃后稍有下降,硬度逐渐下降。
Using intermediate frequency induction heating furnace for construction Q550D steel were tempered by different processes. The microstructure was observed by light microscopy. The impact energy and hardness were measured. The effects of tempering time and temperature on microstructure and properties were studied. The results show that when the tempering temperature is 200 ℃, the microstructure of the tempered martensite is tempered martensite. With the increase of holding time, the precipitation of carbides increases, the martensite gradually decomposes, the impact energy gradually increases, and the hardness gradually increases Decreased; When the tempering holding time at 200 ℃ was 10 min, the microstructure of tempering martensites changed from tempered martensite at low temperature induction tempering to tempered martensite at intermediate temperature induction tempering. With the increase of tempering temperature, Carbide precipitation and growth from the martensite lath, martensite decomposition, the organization tends to be uniform, the impact of the first increase, when the tempering temperature exceeds 350 ℃ after a slight decline, the hardness decreased.