The Effect Of Si Content And Heat Treatment On Microsture And Properities Of Cast High Silicon Stainless Steel

High silicion austenitic stainless steel has been widely used in sulfurc acid equipment for its excellent resistance to high temperature and strong oxidizing medium.But for its chemical compositions and heat treatment on the microstructure,properties?mechanical properties and corrosion resistance?systematic research rare now.This issue,XDS-2 added with Si element whose mass fraction being4.0%,4.5%,5.0%,5.5%,6.0%,6.5%.Samples were melted by Vacuum medium frequency induction furnace,and reveals the influence of Si content on Microstructure,mechanical properties and corrosion resistance of Cast high-silicion stainless steel.Choosing a group of matirials with good comprehensive properties for solution treatment,and explore the influence of heat treatment parameters on microstructure and properties of the alloy steel.Theas-castmicrostures,mechanicalproperties,corrosionresistance,and electrochemical corrosion of different content Si of stainless steel are studied.The results show that containting Si 4.0%⁶.0%,the basic crystal structure of alloy is face-centered cubic austenite,in Si 6.5%,alloy is given priority to?,also contains a small amount of?with body centered cubic structure.With increasing Si content,ferrite content increasing in as-cast microstructure,the morphology of ferrite gradually changes from point-like,dendritic to thin strips,half mesh.Containing Si4.0%⁵.0%,the tensile strength change little,the yield strength decrease at first then increase;when Si content more than 5%,the tensile strength and yield strength increase,and the tensile strength increase from 464Mpa to 628Mpa,and yield strength has minimum(?_0.2=289Mpa)when Si content is 4.5%.With increasing Si content,the elongation steady decrease and the Vickers hardness increases constantly.With the increase of Si content of the alloy,its uniform corrosion rate is falling in 93%H₂SO₄and 98%H₂SO₄.Compared with 93%H₂SO₄,alloy steel is more resistance to corrosion in 98%H₂SO₄.In the process of corrosion,the surface of alloy steel form the passivation film riched in Si O₂,With increasing Si content,the passivation film increase and more dense,increasing corrosion resistance.With increasing Si content,alloy's E_corr increase,I_corr decrease,I_pass increase and Passivation Region increase,increasing the stability of passive state of stainless steel and corrosion resistant.The microstures,mechanical properties,corrosion resistance of stainless steel with 5.5%Si of solid solution were respectively studied.The results show that with the extension of holding time,the content of ferritic decreasing in solid solution microstructure,ferrite's morphology gradually changes from thin strips,half mesh to a granular,short strip.After 1050 or 1100?solution treatment,the tensile strength of alloy steel increases first and then decreases instantly,and higher than that of as-cast,whiletheyieldstrengthhasbeendecreased,havingmaximum value?415Mpa?when as-cast.With the extension of holding time of solution treatment,the elongation of alloy increase with different amplitude,while holding time more than one hour,the elongation has little change,but it is siginificantly higher the as-cast.Under certain holding time,alloy steel's strength after 1100?solution treatment less than 1050?solid solution treatment.When the holding time is from0.5 hour to one hour,with the holding time,the alloy corrosion rate is significantly reduced,while the holding time more than one hour,the alloy corrosion rate has little change.After 1100?solution treatment,the alloy corrosion rate is lower,having better corrosion resistance.With the extension of holding time,Si O₂ passivation film increased in the number and more dense.When Si content is 5.5%,the stainless steel has better overall performance,and on the composition of the stainless steel,after heated at 1100?and kept one hour,its mechanical properities and corrosion resistance relative to the best.