Material factors analysis of the cracking in 0Cr12Mn5Ni4Mo3Al stainless steel pipe sleeve on aircraft flare-less pipe joints

It is shown that the discreteness of the chemical compositions of 0Cr12Mn5Ni4Mo3Al steel is large and the range of the Cr/Ni equivalent ratio is wide, which has big impact on the content and morphology of ferrite and easy to occur cracking phenomenon when bearing, based on the chemical compositions analysis of pipe sleeve on aircraft flare-less pipe joints. It can be found that the chemical compositions of cracked pipe sleeve are almost meeting the requirements, but the Cr/Ni equivalent ratio is on the high side. So it can be concluded that the fracture failure of pipe sleeve is closely related to the content, shape and distribution of δ-ferrite. Thus, the available solution of the cracking in 0Cr12Mn5Ni4Mo3Al stainless steel pipe sleeve is to reduce the Cr/Ni equivalent ratio within the permissive of nominal chemical compositions and adjust the hot working process to form the reasonable morphology and distribution of δ-ferrite.