Study On Key Technology Of Cryogenic Stretch Forming On Austenitic Stainless Steel

The object of study is cryogenic stretch technology of austenitic stainless steel. The material strength, plasticity and toughness at different cryogenic stretch stress are studied and material performance at cryogenic stretch stress α k and cold-stretch stress410MPa are compared based on experiments of austenitic stainless steel S30408made in China in this paper. In addition, FEA is used to study stress distribution of pressure vessel in the cryogenic stretch process. These conclusions are as follows:(1) The material behavior of austenitic stainless steel S30408respectively cryogenically stretched to640MPa、960MPa and1280MPa was researched by means of charpy impact、bend and metallographic experiment, which makes clear that the suitable cryogenic stretch stress of austenitic stainless steel S30408is between640MPa and960MPa.(2) Austenitic stainless steel S30408was pre-stretched to800MPa in liquid nitrogen. Meanwhile, the material strength、plasticity and toughness was tested by means of tensile and impact at-196centigrade、bend at room temperature and metallographic experiment, which indicate austenitic stainless steel S30408cryogenically stretched to800MPa have a sharp enhancement about yield strength and meet the plastic standard of pressure vessel.(3) Cryogenic stretch technology and cold-stretch technology of austenitic stainless steel S30408are compared. The performance of material treated with cryogenic stretch stress α k and cold-stretch stress410MPa are researched. Contrast to cold-stretched technology, the yield strength and tensile strength of S30408cryogenically stretched to800MPa increase significantly, while the plasticity decline.(4) An austenitic stainless steel inner vessel was designed with three different modes, that is conventional design, cold-stretched technology and cryogenic stretch forming technology. This researches show that cryogenic stretch forming technology can apparently reduces the vessel wall. Additionally, cryogenic stretch forming pressure vessel was simulated with ANSYS,So the distribution of stress、strain and deformation in cryogenic stretch process and normal working condition are obtained, which verify the safety of cryogenic stretch forming pressure vessel.