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本文研究了几种典型的低碳马氏体高强度钢的微观结构和强度、韧度、裂纹扩张阻力曲线特性随回火温度的变化以及相互之间的关系。研究结果表明:随回火温度提高,低碳马氏体位错亚结构由均匀、弥散分布变化为位错缠结,形成位错胞壁继而趋于逐渐消夫;碳化物按魏氏分布析出,由细小、均匀、弥散的针状转变为球状;板条束间存在的残余奥氏体膜在中温回火发生分解,形成碳化物膜。低碳马氏体具有高的强度和抗启裂韧度,但抵抗裂纹继续扩张的能力较弱。在J_R阻力曲线中,J_j表征材料抵抗启裂能力的大小,斜率dJ/da表征在给定试样几何条件下材料抵抗裂纹继续扩张的能力。当材料的强度级别较高时,dJ/da是由dJ_e/da和dJ_p/da二部分构成;当材料级别较低时,dJ/da主要由dJ_p/da构成,无量纲参数c有可能用来判别材料抵抗裂纹扩张的能力。
In this paper, the microstructure and strength, toughness, crack growth resistance curves of several typical low-carbon martensitic high-strength steels with the tempering temperature changes and the relationship between them. The results show that with the increase of tempering temperature, the low-carbon martensite dislocation sub-structure changes from uniform to diffuse to dislocation entanglement, and then the dislocation cell wall tends to gradually disappear. The carbides are precipitated by Weisner distribution, From the small, uniform, dispersed acicular into globular; residual austenite film exists between the slab beam tempering at room temperature decomposition, the formation of carbide film. Low-carbon martensite has high strength and cracking resistance, but its ability to resist crack expansion is weak. In the J_R resistance curve, J_j characterizes the material’s resistance to cracking and the slope dJ / da characterizes the ability of the material to resist the continued crack propagation under the given sample geometry. DJ / da is composed of two parts, dJ_e / da and dJ_p / da. When the material level is low, dJ / da mainly consists of dJ_p / da, and the dimensionless parameter c is likely to be used Identify the ability of the material to resist crack expansion.