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本文采用模拟焊接热循环试验方法,测定了不同峰值温度下Cr-Al钢冲击韧性的变化,并对各峰温下的断口形貌、金相组织、晶粒度及析出物等进行了观察和鉴定。结果表明,随着峰值温度的提高,冲击韧性下降,断口形貌由韧窝状变成解理或准解理状。模拟热循环的峰温高于Ac_3时,随着峰温的提高,奥氏体晶粒明显长大,马氏体板条尺寸也相应增大,因此冲击韧性相应下降。模拟热循环的峰温低于Ac_3时,高温下马氏体板条内的碳进一步析出,基体软化,塑性提高;马氏体板条变得弯曲,碳化物聚集成球状,致使冲击韧性明显提高。
In this paper, the simulation welding thermal cycling test method was used to measure the impact toughness of Cr-Al steels at different peak temperatures. The fracture morphology, microstructure, grain size and precipitates at different peak temperature were observed and Identification. The results show that with the increase of the peak temperature, the impact toughness decreases and the fracture morphology changes from dimple to cleavage or quasi-cleavage. When the peak temperature of the simulated thermal cycle is higher than that of Ac_3, the austenite grain grows obviously with the increase of the peak temperature and the martensite lath size increases correspondingly, so the impact toughness decreases accordingly. When the peak temperature of the simulated thermal cycle is lower than Ac_3, the carbon in the martensite lath further precipitates at high temperature, the matrix softens and the ductility increases; the martensite lath becomes curved and the carbide aggregates into a sphere, resulting in a marked increase in impact toughness.