高碳高铬模具钢的开裂与强韧化

本文以Cr12MoV钢为例研究了高碳高铬模具钢的静弯断裂和含裂纹体条件下的开裂行为;探索了钢的强化和韧化机理。研究发现,此类钢裂纹的萌生一般起始于粗大碳化物的解理,而完成于解理裂纹向钢基体中的延伸。粗大碳化物的解理开裂发生于钢的弹性应变极限状态。基体塑性对其无明显影响,但是却强烈影响碳化物解理开裂后裂纹向钢基体中的延伸。钢中裂纹的扩展属于复杂准解理类型,它不仅与钢基体的塑性程度有关,而且还与钢中碳化物的分布、大小和间距以及裂纹面附近残余奥氏体的应变诱发相变有关。研究认为,此类钢的强化受控于裂纹萌生的阻力,而钢的韧化则取决于裂纹的扩展特征。

Fracture Behaviours andStrengthening and Toughening of the High-Carbon and High-Chromium Die Steel

The fracture behaviours and the strengthening and toughening mechanism of the high-carbon, high-chromium die steel have been investigated. The experimental results showed that the nucleation of failure of the high-carbon, high chromium die steel usually started with cleavage cracking of the coars carbides, then the crack extended into the matrixes of the steel up to a subcritical size, and the cleavage cracking of the coarse carbides formed, when the clastic strain came up to the limit standard of the steel. So, the cleavage cracking of coarse carbides depends on their sizes and distribution, but the plasticity of the steel does not have remarkable effect on it. Although, the plasticity of the steel has an important effect on the crack growth into the matrixes of the steel after the cleavage cracking of the coarse carbides. The crack subcritical propagation was a kind of complex quasi-cleavage fracture. It not only concerned the degree of plasticity of the matrixes of the steel, but also concerned the distribution size and interparticle spacing of the carbides in the steel, and the strain inducing transformation of the residual austenite near the crack tip. So, the strengthening of the steel is controled by the resistance to the formation of nucleation of failure, but the toughening of the steel depends on the crack subcritical propagation behaviour, and, the strengthening and toughening of the high-carbon, high-chromium die steel is different from other many steels.