Super Duplex Stainless Steel Two Phase Organization Control And Electrochemical Performance Study

Combining ferrite stainless steel and austenitic stainless steel,duplex stainless steel has excellent corrosion resistance and good comprehensive mechanical properties,this make it get more extensive application in the field of oil and gas.However,caused by bipolar organization to coordinate,duplex stainless steel seamless pipe easily has cracking problems in the manufacturing process.In this paper,dynamic and static recrystallization process of S32750 super duplex stainless steel were studied in the thermal deformation,and includingthe impact on two phase control and corrosion resistance.The study found that in S32750 super duplex stainless steel,Ni?Mn element enrich in austenite,and Cr,Si,Mo favoring distribution in the ferrite.By 1000-1250? high temperature annealing,ferrite proportion of S32750 with the annealing temperature is reducing at first and then increasing.Corresponding to this,S32750 super duplex stainless steel corrosion resistance as the annealing temperature increased firstly and then descend.When annealing temperature is 1050 ?,the two phase proportion is closest,and S32750 has best corrosion resistance.Researching the rheological curve of S32750 duplex stainless steel thermal deformation,the dynamic recrystallization activation is Q=552 kJ/mol,stress index is n=4,and the hot deformation equation is ? = 3.37×1017[sinh(??p-)]4exp(-552000/RT).When Deformation temperature is 1050 ?,under the condition of deformation rate is 0.1-1s-1,two phase grain size is the most uniform and tiny,about 15 microns;Under the condition of the same deformation rate,when deformation temperature is 950 ?,the average grain size of ferrite and austenite in distribution or numerical are the closest,about 12.5 microns.In low deformation rate(0.01s-1-1s-1)in the process of hot deformation,ferrite of S32750 super duplex stainless steel first occur dynamic recrystallization,but austenite does not occur dynamic recrystallization occurs,just store large amounts of deformation and prompt austenite to transform to ferrite.At high deformation rate(1s-1-10s-1),two phases occur dynamic recrystallization,and finding no obvious phase transformation.After hot deformation,deformation structure of S32750 super duplex stainless steel will occur recovery and static recrystallization in the short time soaking time,recovery and static recrystallization was almost completed within 20s,soaking time increased to 100s,structure change is not big.