Study On Effects Of Q&P Treatment Processes On Microstructure And Properties Of 30Cr13Si Martensitic Stainless Steel

Cr13 martensitic stainless steel is a kind of martensitic stainless steel,has a broad application prospect for its good corrosion resistance in the atmosphere,water vapor and organic acid.The traditional heat treatment process for this kind of martensitic stainless steel is quenching-tempering,which brings the steel very high strength and hardness but low plasticity and toughness.Quenching-partitioning(Q&P)process is a new heat treatment process for martensitic steel that can obtain martensite and carbon-rich austenite multiphase microstructure to improve the plasticity and toughness of the steel.With the improving heat treatment process,combining with the method of alloying will make the plasticity and toughness of martensitic stainless steel much better.Based on 30Cr13Si as tested steel,the influence of different Q&P heat treatment regimes on microstructure and mechanical properties were investigated by using laser scanning confocal microscope(LSCM),X-ray diffraction(XRD),transmission electron microscope(TEM)and tensile testing machine.The Conclusion was obtained as follows:1.The Q&P microstructure of 30Cr13Si is mixture of martensite and residual austenite,which also has a little of carbide.The addition of Si can inhibit the precipitation of carbide.By examined under TEM,both martensite and residual austenite exist in two forms in the Q&P microstructure.Martensite is composed of lath and twined structure,while residual austenite is in forms of film and bulk.2.Treated with same parameters of Q&P process except raised austenitized temperature,the degree of solid solution raised,and Ms and Mf reduced,so martensitic transformation reduced when quenched to a same temperature between Ms and Mf.When preserved at 1100?,carbide in this steel could ensure complete solid solution,and reduce martensite point to room temperature which could conducive to the operation of industrial production and improve production efficiency.3.When the steel partitioned at 450? for 20min after austenitizing at 1100? for 60min and quenching to 20 ? to 50?,with the increase of quenching temperature,residual austenite content and impact energy increased gradually,yield strength and hardness decreased,and the elongation increased at first and then decreased and reached its peak at 30?.4.When the steel partitioned after austenitizing and quenching to 20?,primary martensite transformed more,and residual austenite existed less.With partitioning temperature increasing from 450 ? to 480 ?,or with the partitioning time extending from 20min to 40min,the residual austenite content in Q&P microstructure of the steel improved,the product of strength and plasticity increased.However,when the steel partitioned after austenitizing and quenching to 30? primary martensite transformed less,and residual austenite existed more.With partitioning temperature increasing from 450? to 480?,or with the partitioning time extending from 20min to 40min,the residual austenite content in Q&P microstructure of the steel decreased,but carbon content of later martensite decreased.As a result,the product of strength and plasticity increased,too.5.When austenitized at 1100? for 30min and quenched to 30? and partitioned at 450? for 40min,the experimental steel 30Cr13Si could obtain the best combination of strength and plasticity:Rp0.2=1050MPa,Rm=1650MPa,A=26%,Akv=40J,Rmx A=43000MPa·%.