The Effect Of Deformation On Microstructure And Properties Of 304 Austenitic Stainless Steel

Intergranular corrosion of 304 austenitic stainless steel could happen under some conditions and could result in some serious consequences. The traditional processing methods have many problems, and grain boundary engineering technique is an effective way to completely solve the sensitization problem of austenite stainless steel and to improve the intergranular corrosion resistance.Cold rolling and cold rolling combined with annealing treatment were used to modify microstructure of austenite stainless steel,OM, SEM, XRD, and EBSD were used to investigate the microstructure evolution, electrochemical potentiokinetic reactivation (EPR) test and a ferric sulfate-sulfuric acid test were carried out to assess the susceptibility to intergranular attack, and the corrosion resistant mechanisms were analyzed as well.The main conclusions are as follows.(1)Cold rolling deformation of 304 austenitic stainless steel could lead to formation of martensite, and with the increase of deformation level,the amount of the precipitated carbide and martensite increased, which resulted in decrease of the intergranular corrosion resistance.(2) Cold rolling combined with annealing treatment could modify microstructure and corrosion resistance of 304 austenite stainless steel, and a small strain benefit for improvement of the intergranular corrosion resistance. The specimen with an optimum pre-strain of 5% and annealed at 947℃for 24h showed excellent corrosion resistance compared with the based materials under the same sensitization condition, which could be attributed to optimum of the grain boundary character distribution. And the results of EBSD test, showed that under low strain (5%)followed by long-time annealing (24h) the special boundaries could reach up to 70.7%, which was higher than that of the based materials (57.3%),and the fraction ofΣ3 boundaries was 41.2%, and the sum proportion ofΣ9 andΣ27 reached 6.9%. The annealed temperature of 947℃was more beneficial to improve intergranular corrosion resistance than 927℃,967℃,987℃.(3) The cold rolling reduction of 5% and annealing at 947℃or 927℃for 24h could improve the tensile strength accompanied by a decrease of elongation at room temperature, however, the effect was not remarkable.