Study on the effect of solid solution treatment on the microstructure evolution and properties of 304 stainless steel bellows

• The research object is 304 stainless steel bellows (thin-walled small tube), explore and summarize the solid solution treatment on the bellows microstructure and properties of the law. • Rotational molding of 304 austenitic stainless steel bellows after solution treatment, stainless steel bellows molding process strain-induced reversal of martensitic microstructure into austenitic microstructure, austenitic organization recrystallization and grain coarsening, while a high density of dislocations and small-angle grain boundaries subside. • Solid solution treatment of 304 austenitic stainless steel bellows after rotational molding can improve the hardening of bellows brought about by the molding process, the service life of stainless steel bellows and the stress corrosion resistance of the bellows. The spin-formed 304 austenitic stainless steel metal bellows are selected as the research object to investigate the influence mechanism of solid solution treatment on the microstructure and properties of stainless steel bellows. Metallographic optical microscope, XRD diffractometer, tungsten filament scanning electron microscope, electron backscattering diffractometer, digital microscopic Vickers microhardness tester, X-ray stress tester, and other test methods are employed to explore the evolution of stainless steel bellows microstructure and properties before and after solid solution treatment to obtain the microstructure and mechanical properties of the stainless steel bellows. The experimental results showed that the strain-induced martensitic microstructure produced during the molding process is reversed to an austenitic microstructure through solid solution treatment, with changes in grain orientation and grain size. The microhardness of the stainless steel bellows after solid solution treatment decreases from 379.52 to 65.68 HV; residual stresses transition from positive tensile stresses to compressive stresses, and resistance to stress corrosion is significantly improved. These results indicated that the solid solution treatment of 304 austenitic stainless steel bellows has a substantial impact on microstructure evolution and mechanical properties, confirming that solid solution treatment is an effective method to improve the microhardness and resistance to stress corrosion rupture of 304 austenitic stainless steel bellows.