护环钢50Mn18Cr4沿晶断裂分析及其对晶界损伤本质的探讨

在对护环钢50Mn18Cr4失效分析的基础上,研究了沿晶碳化物析出对晶界的损伤.研究指出,晶界碳化物析出是由于护环运行过程中加热操作不当引起的;沿晶碳化物析出对钢的有害作用主要表现为对晶界区变形能力和形变强化潜力的损伤.还提出了等强应变的概念,认为晶界受损的多晶体材料,在其应变量超过等强应变之后,晶界区的剪切变形成为较主要的变形方式,这时,在三重晶界或晶界弯折处等有应力集中的地方按微孔型机制形成裂纹并沿晶界扩展,导致微孔型沿晶断裂.等强应变的大小,取决于晶界受损程度.

Intergranular failure analysis of retaining ring steel 50Mn18Cr4 and explore for the essence of grain boundary damage

In this paper,based on the failure analysis of retaining ring steel 50Mn18Cr4,the precipitation of carbides on grain boundary lead to the damage of grain boundary was studied.The research point out that the precipitation of carbides on grain boundary is attributed to the unsuitable heat operation during running;The precipitation of carbides on grain boundary is bad for deformation potential and deformation strengthening in grain boundary area.This article also presents the concept of identical stress deformation.When the real deformation exceeds the identical stress deformation,the shear strain will become the main mode of deformation.So the stress concentration may lead to the formation of crack according to the microvoid mechanism at triplicate grain boundary or twist boundary,then the microvoid will grow along the grain boundary till complete intergranular failure.The value of identical strain is determined by the damage level of grain boundary.