Study On Forging And Solid Solution Treatment Of S32750 Duplex Stainless Steel

S32750 duplex stainless steel with two phases structure of ferrite and austenite has excellent corrosion resistance and mechanical properties.It is widely used in high-end manufacturing fields such as nuclear power,petroleum and petrochemical,pressure vessel and ocean engineering.Yet,hot working process remains a technical challenge.Because it involves high technologies and production difficulties,the high-end market has long been occupied by few foreign companies.This paper mainly covers the study of the forging and heat treatment process of S32750 duplex stainless steel in order to provide guidelines for the mass production of the steel of this grade.Specifically,the proper forging temperature range is determined by modeling the phase transformation during heating and cooling of the steel;Suitable forging equipment and processes are selected by comparing quality of forging produced using different equipment and deformation of each pass;The solution temperature is determined by evaluating the influence of solution process on its corrosion performance and mechanical properties.The conclusion is as follows:1.With the combination of induction furnace(ferro-alloy melt down),AOD and ESR furnaces,ESR ingots(2.5 tons)conforming to the ASTM A276 were produced.Base on modeling results of the phase transformation during heating and cooling of the steel S32750 duplex stainless steel,considering the good plasticity,heating temperature of 1180?and end forging temperature of 1010?or above is determined.2.Comparing to the combined process of press and radial forging,the sole radial forging process has dominate advantages in forging time,and surface and internal quality.By using solely radial forging machine and increasing deformation 20%-35%of each heat,the work piece shows good surface quality.Besides,UT,microstructure,and grain size meet the requirement of GB/T6402-2008,GB/T 1220-2007and GB/T6394-2017 respectively.3.When the solution temperature is?1025?,the?phase is generated and the ferrite content is low,which resulted in low plasticity and low elongation.When the solution temperature is higher than 1150?,the increased ferrite content leads to good mechanical properties,but reduced pitting resistance.4.In order to achieve mechanical properties of S32750(R_P0.2?550 MPa,R_m?800MPa,A?15%,HRC?32)required by ASME-SA790/790M and better resistance to pitting corrosion,solution heat treatment of S32750 duplex stainless steel The temperature should be 1100-1150?.