Alloy Elements And The Effect Of Solution Treatment On CD3MN Duplex Stainless Steels Microstructure And Performance

Tidal power is currently one of the most widely application prospect in theuse of clean energy. The materials of tidal power devices corrosion is serious,which have long time immersed and impact in seawater, then limiting theapplication of tidal power devices. Duplex stainless steel CD3MN have bothaustenitic stainless steel with excellent toughness and weldability, and ferriticstainless steel high strength, resistance to sea water corrosion excellent.Therefore it is suitable for tidal power devices materials. This paper studise theeffects of alloying elements Mn, RE, N and the solution treatment on the duplexstainless steel CD3MN on the miscrostructure, mechanical properties andcorrosion resistance.The study found that addition of Mn, tensile strength changed little, theelongation is first weakened then enhancement, pitting corrosion resistance firstincreased and then decreased. When the content of Mn was1.5%, the overallperformance is best. The addition of N improves the tensile strength, elongationand corrosion resistance. The highest tensile strength can reach705MPa. Theaddition of RE makes the miscrostructure uniform. With the increasing of RE,the tensile strength first increased and then decreased, the elongation increasedgradually, pitting corrosion resistance decreased first and then increased. Whenthe RE content is0.4%, the duplex stainless steel of tensile strength, elongation,impact toughness and corrosion resistance performance is best. The optimumduplex stainless steel CD3MN of the tensile strength is750MP, yield strength is558MPa, elongation is34%, shrinkage rate is61%, the impact energy is147J,Brinell hardness is217.Using the method of contrast test, the research shows that duplex stainless steel after different solution temperatures (950℃,1020℃,1070℃,1120℃,1170℃) for4h, with the increase of solution temperature, microstructure ofaustenite phase gradually decreased, tensile strength and elongation firstincreased and then decreased, pitting corrosion resistance first weakening andthen enhancement, stress corrosion resistant performance first increased and thendecreased; When the solution temperature is1120℃for (2h,3h,4h,5h), theaustenite phase gradually reduced, the elongation is first increased and thendecreased, the corrosion resistance decreased first and then increased, the stresscorrosion performance over time have slow enhancement with the holding timeextension. The optimum solution treatment is1070℃for4h and water treatmentprocess, the phase ratio close to1:1, the comprehensive properties is best.