Research On Toughness Of Austenitic Stainless Steel Welded Joints For Ultra-Low Temperature Hydrogen Storage Vessel

GB150-2011 has extended the material design temperature limit to-253 ?(liquid hydrogen temperature),which presents new challenges with the material properties of ultra-low temperature cryogenic vessels.For the forming process of the stainless steel ultra-low temperature cryogenic vessel,welding after cold-formed plastic deformation,subject to the current test equipment and test technology,the research on the anti-brittle fracture of the material is still insufficient in the-253 ?,relevant design,manufacturing and safety assessment is still lacking data support.This paper choses S30408 and S30403 austenitic stainless steel as the research subject,which is used in the cryogenic vessel,carried out research on the ultra-low temperature toughness of the base metal and welded joints after plastic deformation.The major research works and academic achievements are as follows:Carried out instrumented impact tests of S30408 austenitic stainless steel at-253 ? and-100 ? environment and quasi-static fracture toughness test at-100 ? environment,access to the material quasi-static and dynamic fracture toughness data.The results show that S30408 austenitic stainless steel does not show ductile brittle transition at-253 ?.Based on the proportional relationship between the dynamic and static loading resistance curves of austenitic stainless steel,establishing the relationship between dynamic and static crack growth resistance curves of S30408 austenitic stainless steel,estimating material quasi-static fracture toughness at-253 ? environment.Carried out instrumented impact tests of the austenitic stainless steel base material and welded joint of different plastic deformation rate at-253 ? environment,researching on the impact toughness of the material,analyzing the structural changes and fracture morphology during the forming process,and discussing the relationship between the impact absorbed energy and the lateral expansion.The results show that the ultra-low temperature toughness of the austenitic stainless steel base material does not decrease significantly by 15% plastic deformation;the ultra-low temperature toughness of the welded joint is obviously decreased due to the reduction of plastic energy and crack growth energy.S30408 and S30403 austenitic stainless steel by 15% plastic deformation does not appear tough transform into brittle phenomenon at-253 ? environment,which is still tough fracture,impact absorbed energy and lateral expansion can be a decision index to judge the ultra-low temperature vessels qualified.This paper systematically carried out the research on the ultra-low temperature toughness of S30408 and S30403 austenitic stainless steel base metal and welded joints in the cold forming plastic deformation,and analyzed the material impact toughness changes and fracture characteristics,and obtained-253 ? material quasi-static fracture toughness data,evaluated the possibility of brittle fracture of austenitic stainless steel after cold forming plastic deformation,the research results fill gaps in related fields in China and provide the basis for the exploration and standard improvement of the design,manufacture and safety evaluation methods of ultra-low temperature vessels.