| Because A286 austenitic precipitation hardening stainless steel has high yield strength and creep rupture strength at 650 ℃,as well as excellent corrosion resistance and processing plasticity,it is often used to process fasteners in aviation,automobile engines and structural parts.With the rapid development of industrial construction in China,the demand for the performance of all kinds of equipment is increasing,which requires materials to take into account high strength,high toughness and good corrosion resistance and high temperature resistance.However,due to the constraint of economic cost,the popularization and use of A286 stainless steel is limited to a certain extent.In order to better select suitable materials according to practical application,take into account a variety of differential needs,and promote its popularization and use,it is necessary to compare the microstructure and properties of materials prepared by different smelting processes.In this paper,A286 stainless steel prepared by electric steelmaking + secondary refining + electroslag remelting(EAF+LF+ESR)and vacuum induction + vacuum consumable(VIM+VAR)smelting process was taken as the research object,the differences and characteristics of microstructure,impurity composition and non-metallic inclusions of the two kinds of test steel were compared and studied,and the mechanical properties and corrosion properties of the two kinds of test steel were comprehensively compared and analyzed.The results show that:(1)There is little difference in the main alloy elements between the two test steels,which meet the requirements of the national standard,but there are some differences in the contents of impurity elements P,S,Si and Mn,gas elements [N].After standard heat treatment,the microstructure of the two sample steels is equiaxed grain,and the grain size grade is 7 grade.(2)According to the results of Aspex inclusion detection equipment,it is found that the type,quantity,size and distribution of inclusions in VIM+VAR test steel are better than those in EAF+LF+ESR test steel.The main inclusion in VIM+VAR test steel is Ti(C,N),while EAF+LF+ESR test steel contains a certain amount of oxide and very few other inclusions in addition to Ti(C,N).The difference of inclusions is mainly due to the poor control of impurity elements in the smelting process.(3)When the high temperature endurance test temperature is 600 ℃ ～ 700 ℃,0.014 wt.% P element shows beneficial effect,phosphide hinders dislocation movement and grain boundary migration,and increases rupture life;with the increase of temperature and the decrease of stress,the difference of stress rupture life of the two test steels decreases.When the test temperature is 750 ℃,0.014 wt.% P element increases the grain boundary diffusion activation energy,inhibits grain boundary diffusion,promotes the precipitation of harmful phase η,promotes the transformation of η phase from lamellar to Widmanstatten structure,and reduces the high temperature endurance strength.(4)The corrosion properties of two kinds of test steels were compared comprehensively.The electrochemical test results,salt spray corrosion and stress corrosion properties of VIM+VAR test steel were better than those of EAF+LF+ESR test steel.This is due to the existence of more kinds and quantities and larger size of non-metallic inclusions in EAF+LF+ESR test steel than in VIM+VAR test steel,which destroys the continuity and stability of passivation film,increases the corrosion sensitivity of EAF+LF+ESR test steel and promotes the initiation of pitting corrosion. |
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