Effects Of Solution Treatment On Mechanical And Corrosion Resistant Properties Of S31803 Duplex Stainless Steel

The thesis was mainly studied the solution temperature and holding time on the mechanical properties and corrosion resistance of duplex stainless steel S31803, which had been used in bridge sockets. The samples after different heat treatment were investigated by optical microscope, scanning electron microscopy,x-ray diffraction, universal testing machine, electrochemical workstation and other experimental methods for sample structure, crystal structure, mechanical properties, and corrosion resistance. The results show that:X-ray diffraction analysis results show that with increasing solution treatment temperature, the austenite content reduced, while ferrite content increase. Solution treatment in1050 o C, the ratio of austenite to ferrite was close to 1:1. At this point, the austenite(γ) grain achieved minimum, and closed to 10μm. Its tensile strength is 760 MPa,yield strength is 582 MPa, elongation is 36.5%, shrinkage is 78%. Fixed the second solution temperature in 1050℃, holding 2 hours, tensile strength will be776 MPa, yield strength will be 592 MPa, elongation is 38%, shrinkage is79%.The strength grow up a little. Comparing different solution temperature between 1000 ℃, 1050 ℃ and 1100 ℃(holding time fixed at 2 hours),the electrochemical corrosion tests under the conditions found in acidic conditions, its potential and corrosion current order: 1050 ℃ >1110 ℃ >1000 ℃.While in neutral,the result is 1100℃> 1000℃>1050℃. While in alkaline conditions, the result is 1000℃>1050℃> 1100℃. For comparing corrosion resistance, salt spray testing was conducted on S31803 duplex stainless steel, 304 austenitic stainless steel, 1Cr17 ferrite stainless steel and 2Cr13 martensitic stainless steel. Test compared the S31803 duplex stainless steel and the other three kinds of stainless steel in the test of salt fog corrosion. Result of salt fog corrosion ressitance is S31803 > 304> 1Cr17> 3Cr13.With the heat treatment process of duplex stainless on 1050 ℃ solution temperature 2 hours, we didn’t found fracture and surface crack in the 100% breaking tests. In the fatigue tests, we didn’t found fracture and surface crack in the 2.02.0×106 fatigue test.This technique has been applied in sling tiger is apart from the bridge, the bridge is now open to traffic operation results of this article with the materialselection of anchorage of the bridge and S31803 duplex stainless steel solid solution treatment process to provide some advice and help.