Hot Deformation Behavior And Microstructure Transformation Of 2507 Duplex Stainless Steel

There are ferrite and austenite two phases in duplex stainless steel solid solution structure at the same time,either phase proportion is generally 45%-55%Duplex stainless steel because of excellent corrosion resistance mechanical properties and weldability,is widely used in petroleum,chemical industry,ocean and construction and other important fields.However,due to the high alloying element content of duplex stainless steel,complex phase transformation will occur at high temperature,and the austenite and ferrite in the thermal deformation behavior and other aspects of the difference,the thermal deformation behavior of duplex stainless steel is very complex.In particular,due to the difference in the thermal deformation behavior of the two phases of 2507 duplex stainless steel,there will be cracking phenomenon in the middle and the edge in the hot working process,which seriously affects the mass production and application of 2507 duplex stainless steel.In this paper,the 2507 duplex stainless steel produced by Shandong Taishan Iron and Steel Group is taken as the research object.OM,SEM,XRD,EBSD and other microscopic characterization methods were used to study the precipitation behavior of microstructure changes under different solution aging conditions,and the thermal deformation behavior under different deformation conditions during single pass hot compression process was studied by Geeble3500 thermal simulation testing machine.The main conclusions are as follows:1.When the solution temperature is between 1050?-1100?,the microstructure distribution of the two phases is more uniform after holding for 30min.Compared with the hot-rolled state,the strength and plasticity of the two phases are greatly improved.On the basis of the existence of internal defects(micro-cracks),The tensile strength is greater than 750Mpa;In addition,combined with the electrochemical performance test,at 1050?,the tendency of pitting is the lowest(the pitting potential Eb is the highest),which is conducive to the formation of stable passivation film and reduce the occurrence of pitting corrosion.2.Within the temperature range of 850?-950?,the aging temperature increases and the content of ? phase decreases.As a kind of hard and brittle phase,? phase does great harm to the mechanical properties of duplex stainless steel.The precipitation of? phase will form a chrome-poor zone,which will lead to the deterioration of corrosion resistance of the alloy.3.At higher strain rate and low temperature,bear the softening effect is mainly composed of ferrite.On the contrary,in the lower strain rate and high temperatures,softening action of austenitic began to take on more,ferrite and austenite recrystallization degree is higher,two-phase deformation is uniform.By hot working diagram analysis,the deformation temperature is 1050?-1150?.The strain rate of 0.01s-1-0.1 s-1 is a more suitable hot working process parameter.