【摘要】 以一种Q690工程机械用钢为对象,研究不同终轧温度和待温厚度对实验钢低温冲击功的影响,利用光学显微镜、扫描电镜及透射电镜对组织进行观察与分析。结果表明,随着终轧温度的降低或待温厚度的增加,实验钢的低温冲击功明显升高,当终轧温度低于850℃,待温厚度45 mm时,实验钢在-20℃时的冲击功达到200 J以上。冲击功较高的实验钢组织为针状铁素体及少量粒状贝氏体,而冲击功较低的实验钢组织为板条贝氏体及少量粒状贝氏体,组织中有效晶粒尺寸增加,大角度晶界比例降低及M/A岛尺寸变大均减弱对裂纹扩展的阻碍作用,导致实验钢低温冲击功降低。更多还原

【Abstract】 Influence of finishing rolling temperature and holding thickness on low temperature impact energy of a Q690 construction machinery steel was investigated,and the microstructure of the steel was observed by optical microscopy,scanning electron microscopy and transmission electron microscopy.The results show that the low temperature impact energy of the experimental steel increases significantly with decreasing finishing rolling temperature or increasing holding thickness.The impact energy for the steel at-20 ℃ is higher than 200 J when the finishing rolling temperature and holding thickness are lower than 850 ℃ and 45 mm,respectively.The microstructure is mainly acicular ferrite plus a small amount of granular bainite for the high impact energy steel,and the microstructure consists of mainly lath bainite and a small amount of granular bainite for the low impact energy steel.The resistance of crack propagation is weakened as the effective grain size increases,proportion of high angle grain boundaries is reduced and the size of M / A island becomes larger and therefore the impact energy decreases.更多还原