【摘要】 本文研究了Ｃ－Ｓｉ－Ｍｎ－Ｂ贝氏体钢的疲劳裂纹扩展特性．结果表明，在强度相近的情况下，含１．８％Ｓｉ钢的门槛值△Ｋｔｈ较 ０．６％Ｓｉ钢的低，而且钢中的残余奥氏体对提高△Ｋｔｈ值并非有利．１．８％Ｓｉ钢的△Ｋｔｈ值随钢的屈服强度降低而提高，然而４５０℃回火后，虽然△Ｋｔｈ提高，但裂纹扩展速率也显著提高，这表明４５０℃回火贝氏体脆性促进了疲劳裂纹的扩展。在应力强度因子较高的范围内，疲劳裂纹扩展速率受钢的断裂韧性影响，断裂韧性高，裂纹扩展速率低．更多还原

【Abstract】 Character of fatigue crack propagation in C-Si-Mn-B bainitic steel has been inves- tigated in this paper. The results show that the threshold value △Kth of steel with 1.8%Si content is lower than that of steel containing 0.6%Si while both of them have the little deference in strength and the retained austenite in steel with higher Si has no benefit for raising the △Kth.The △Kth of steel with 1.8%Si has a increase with decrease in yield strength. Although the threshold value △Kth is higher after tempering at 450℃,the rate of crack propagation will be increased evidently. It is demonstrated that the temper embrittlement at 450 ℃ accelerates fatigue crack propagation rates. In the higher △ K range, the fatigue crack propagation rate will be affected by the fracture toughness in steel. The higher fracttire toughness in steel is helpful for decreasing the fatigue crack propagation rate.更多还原