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采用四点弯曲试样(FPB),对轴承钢GCr15在不同热处理制度下的滑移型(Ⅱ型)断裂韧性(K_(Ⅱc))进行了测定。试验结果表明,Ⅱ型断裂参数在如下范围内变化:K_(Ⅲc)=17～35MPa2~(1/m),裂纹扩展开裂角θ_o=55°～62°,K_(Ⅱc)/K_(Ⅰc)=1.1～1.6;下贝氏体(B下)含量在31％时的下贝氏体和马氏体(M)的复合显微组织(B下/M)有最佳的强韧性匹配,较高的断裂韧性值。在此基础上,对Ⅱ型断裂特征、不同热处理条件下材料强韧化机制和Ⅱ型断裂韧性试验方法进行了分析讨论。试验结果与线弹性复合型断裂理论的预测值进行了比较,对其差异和矛盾进行了分析讨论。
The sliding type (Ⅱ) fracture toughness (K Ⅱ (Ⅱc)) of bearing steel GCr15 under different heat treatment conditions was measured by four-point bending test specimen (FPB). The experimental results show that the type Ⅱ fracture parameters change within the range of K_ (Ⅲc) = 17 ~ 35MPa2 ~ (1 / m), crack propagation crack angle θ_o = 55 ° ~ 62 ° and K_ (Ⅱc) / K_ = 1.1-1.6; the composite microstructure of lower bainite and martensite (M) under the condition of lower bainite (B lower) content is 31% High fracture toughness value. On this basis, the type Ⅱ fracture characteristics, the toughening mechanism of the materials under different heat treatment conditions and the Ⅱ fracture toughness test methods were analyzed and discussed. The experimental results are compared with those of linear elastic fracture theory, and the differences and contradictions are analyzed and discussed.