| Austenitic stainless steel is widely used in cryogenic vessels due to its high strength and plasticity,good corrosion resistance,welding and cold working properties.The application of strain strengthening technology in austenitic stainless steel pressure vessel can make the low-temperature pressure vessel of austenitic stainless steel have smaller quality and less material than the pressure vessel of traditional design under the same working strength.In this paper,SAW welding,MAG welding and PAW/TIG welding were used to weld the 06Cr19Ni10 austenitic stainless steel plates,and the welding joints of one set of plates were subjected to low temperature pre-stretching strain strengthening treatment.Then,the austenite stainless steel welded joint before and after strain strengthening was studied through mechanical property test and metallographic microstructure test.The following conclusions are obtained:(1)Strain strengthening austenite stainless steel can make its microstructure change and deformation can induce martensite phase transition,that is,process hardening and phase transition strengthening can be generated,so as to improve its yield strength and tensile strength.(2)Theoretically,the solidification mode of 06Cr19Ni10 austenite stainless steel welding seam was analyzed to be FA mode,and the metallographic test in this paper also obtained the same result.However,due to the influence of welding heat source,welding material and supercooling degree,ferrite with different content and shape will be obtained during welding.(3)For the MAG and PAW/TIG welding of 06Cr19Ni10 austenite stainless steel,the toughness of the welding seam of PAW/TIG is better than that of MAG welding before strain-hardening.However,after the strain-hardening,the toughness of the PAW/TIG welding seam decreased significantly,and the toughness of the MAG welding seam was improved.As a result,the toughness of the MAG welding seam was higher than that of the PAW/TIG welding.SAW had the worst weld toughness compared with the previous two welding methods.(4)For the MAG welding and PAW/TIG welding joints of austenitic stainless steel,the microhardness values of the two welded joints were improved compared with that of the parent material after the pretensile strain strengthening treatment with the deformation amount of 8%.In particular,the microhardness of the PAW/TIG welding joint increased significantly.The hardness of welding joints strengthened by SAW welding strain is lower than that of MAG welding and PAW/TIG welding.(5)The welding joints of 06Cr19Ni10 under MAG welding and PAW/TIG composite welding were well formed in this paper,and the mechanical properties of the welded joints before and after strain hardening were in accordance with the standard specification of cryogenic pressure vessel and the performance was excellent.But SAW welding is not suitable for stainless steel welding.(6)Using the finite element method(fem)of austenitic stainless steel GTAW welding process to simulate the temperature field and residual stress field before and after the strain-hardening analysis found that under the welding linear energy of 400 j/mm,obtained the agreement with the experiment of welding and heat affected zone size and depth of molten instructions after welding strain strengthening technology cannot completely eliminate the welding residual stress,but can improve the joint distribution of residual stress. |
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