E550海洋平台用钢二次裂纹扩展机理研究

摘要

利用光学显微镜和背散射电子衍射技术对E550海洋平台用钢二次裂纹扩展机理进行了研究,同时对二次裂纹周边的晶粒取向进行了分析.结果表明:钢中的二次裂纹扩展方式与相邻晶粒滑移面的夹角密切相关,其中40％左右的小角度夹角对裂纹扩展影响较小,另外40％左右的相邻晶粒滑移面的夹角为50～62°的大角度夹角,此类夹角的相邻晶粒会在晶界处导致裂纹偏转或起到止裂效果.%An analysis of secondary cracks in the E550 offshore platform steel has been carried out using optical microscope (OM) and electron backscattering diffraction (EBSD).The crystallographic orientation in the vicinity of the secondary cracks was studied.The results showed that the misorientation between the neighboring grains in the steel had an important influence on the propagation behavior of the secondary crack:40％ of misorientations between neighboring grains were low-angle ones,and these misorientations had a slight influence on crystallographic propagation orientations of the secondary cracks so that the types of cracks propagation were mainly transcrystalline.However,high-angle misorientations made much difference,40％ of misorientations were ultra high-angle ranging from 50° to 62°,these misorientations led to cracks deviation or arrest.