通过夏比冲击试验研究了回火温度对高强度低碳结构钢冲击韧性的影响,并采用扫描电镜、透射电镜分析了产生回火脆性的机理。结果表明,该高强度钢在580℃、610℃较高温度回火时产生回火脆性,-20℃夏比冲击功由238 J(550℃时)降低至19 J(580℃时),冲击断口由韧性断裂转变为脆性断裂,这主要是由于晶界上析出大量较大尺寸的含钼M23C6脆性相,在晶界上起到了裂纹源的作用。 The impact of tempering temperature on the impact toughness of high strength low carbon structural steels was studied by Charpy impact test. The mechanism of temper embrittlement was analyzed by SEM and TEM. The results show that the high strength steel temper brittleness when tempering at 580 ℃ and 610 ℃, the Charpy impact energy at -20 ℃ decreases from 238 J (550 ℃) to 19 J (580 ℃) Fracture changes from ductile fracture to brittle fracture, which is mainly due to the precipitation of a large number of larger size molybdenum M23C6 brittle phase on the grain boundary, which plays a role of source of cracks in the grain boundary.