Study On The Effect Of Mn On The High Temperature Thermal Deformation Behavior Of 23% Cr-section Ni Duplex Stainless Steel

As a kind of high performance material,duplex stainless steel is widely used in petrochemical,chemical,seawater and papermaking industries because of its characteristics of two phases structure.Low-Nickel duplex stainless steel stabilizes austenite by replacing Ni with Mn.Due to the different mechanisms of Mn and Ni stabilizing austenite,the effect of stacking fault energy is different,resulting in different Mn-Ni contents affecting the thermal deformation behavior of high temperature.Therefore,by controlling the change of Mn content and comparing 2304commercial duplex stainless steel,the effect of Mn addition on compression deformation behavior and high temperature tensile mechanical properties of 23%Cr Low-Nickel duplex stainless steel at elevated temperature was studied.The purpose is to improve the heat processing performance of Low-Nickel duplex stainless steel,and provide the necessary theoretical basis for the forging process optimization,plate rolling and hot extrusion,and provide guidance for the actual production.Hot compression tests in the temperature ranging from 1073 to 1423 K and strain rate ranging from 0.01 to 10 s^-1were carried out on a Gleeble-3800 thermal simulator for 23%Cr Low-Nickel duplex stainless steel with different Mn content.Through the analysis of organization and thermodynamics,it is known that:Under the same strain rate conditions,the increase of deformation temperature will make the austenite transition from fine grain to uniform equiaxial crystal,and the more easily the austenite dynamic recrystallization?DRX?occurs.Under the same deformation temperature,excessive strain rate will affect the test steel DRX.The high strain rate will make DRX incomplete.The increase of the content of Mn can make the austenite deformation temperature and strain rate occurred earlier in smaller DRX.Under the deformation condition of 1323 K/1 s^-1,the 6.26¹4.13%Mn content in the experimental steel has a continuous DRX,and the austenite phase DRX is more fully,and the proportion of the LAGB in the 6.26%Mn experimental steel is low,which can promote the occurrence of DRX more.The Arrhenius type hyperbolic sinusoidal constitutive model is used to obtain the peak stress thermal deformation equation of four kinds of steel with different Mn content,and the peak stress constitutive equation with Z parameters is constructed.With the increase of Mn content,the thermal activation energy will slightly increase and fall to a lower value,and the low Z value corresponds to the DRX region,which moves to a wider higher deformation temperature?1323¹423 K?and a lower strain rate(0.01,0.1,1 s^-1).Four different Mn content test steel thermal processing maps and their corresponding optimum heat processing range are obtained.With the same Mn content,with the increase of strain,the area of the unstable region gradually decreases.When the strain is 0.4 and 0.6,the area of the instability area increases first and then decreases with the increase of Mn content.The thermal deformation activation energy and Z value of the commercial low Mn high Ni 2304 stainless steel are higher than that of the 6.26-14.13%Mn test steel,and the area of the unstable zone in the hot working diagram is also higher than that of the high Mn test steel,indicating that the higher Mn content is beneficial to the compression deformation of the high temperature.Hot tensile tests in the temperature ranging from 573 to 1323 K and strain rate ranging from 0.01 to 10 s^-11 were carried out on a Gleeble-3800 thermal simulator for23%Cr Low-Nickel duplex stainless steel with different Mn content,the influence of Mn content on thermoplastic behavior is compared and analyzed.The following conclusions are obtained:With the increase of deformation temperature,the peak flow stress and peak strain of experimental steels decrease.As the tensile temperature rises from 573K to 1073K,the load bearing phase of the test steel is reduced by the change of Mn content.When the content of Mn increases,the shrinkage of the section decreases and the plasticity decreases with the increase of the content of the 573 K.When the deformation of 823,1073 and 1323K increases,the shrinkage of the section increases with the increase of the Mn content,and the plasticity increases.With the same Mn content,the ultimate tensile strength decreases with the increase of deformation temperature.With the increase of Mn content,the ultimate tensile strength decreases at 573 K deformation.The increase of Mn content makes the particle size of the secondary inclusions in the secondary phase larger in the tensile deformation of the test steel?2⁵?m increases to 5¹2?m?,which is an important reason for the plastic deterioration of the material at high temperature.Compared to commercial 2304 stainless steel,the increase of Mn content can effectively increase the ultimate tensile strength at low deformation temperature,while the increase of Mn content has little effect on the ultimate tensile strength at high temperature deformation.The shrinkage of commercial 2304 stainless steel at different deformation temperatures is higher than that of high Mn content test steel,and all of them are ductile fracture.