论文部分内容阅读
本文对45Cr钢两种热处理状态及20Cr钢低碳马氏体从室温到液氮温度范围内的断裂韧性与电子显微断口特征的关系进行了研究。应用扫描电镜观察了裂纹扩展的机制,发现结构钢低温韧脆转变现象的发生与裂纹塑性钝化的程度有直接关系,表现在延伸带的宽度发生很大的变化。本文测定了延伸带宽度并进行了分析讨论。同时对裂纹的扩展机制归纳出三种主要类型:D型、DB型和B型,并与材料参量K_(Ic)/σ_(y.s)值建立了联系。在此基础上提出了初步的结构钢低温断裂机制图,可能对低温结构钢的选材及失效分析有一定价值。
In this paper, the relationship between the fracture toughness and the electron microscopic fracture characteristics of 45Cr steel in two heat treatment conditions and 20Cr low carbon martensite from room temperature to liquid nitrogen temperature range was studied. The mechanism of crack propagation was observed by scanning electron microscopy. It was found that the occurrence of ductile-brittle transition at low temperature has a direct relationship with the degree of plastic ductility, which shows that the width of the ribbon changes greatly. This article measured the extension of the width and analysis of the discussion. At the same time, three main types of crack propagation mechanisms are classified as D type, DB type and B type, and the relations with material parameters K Ic / σ ys are established. On the basis of this, a preliminary mechanism diagram of low temperature fracture of structural steel is proposed, which may have some value for material selection and failure analysis of low temperature structural steel.