Microstructure And Properties Of 2205 Duplex Stainless Steel Submerged Arc Welding Joints

Duplex stainless steel 2205 has high yield strength and good corrosion resistance,which is widely used in the field of ship and ocean.As a traditional process,welding is an important part of 2205 duplex stainless steel processing.Studies have shown that when the austenite phase content is 30vol%-70vol%,the weld performance is excellent.Therefore,the key to welding 2205 duplex stainless steel is to control the content of austenite phase and ferrite phase in the heat affected zone.The welding thermal cycle affects the weld structure,and the welding line energy directly determines the size of the welding thermal cycle.Therefore,in this paper,three kinds of welding processes with different welding line energy were used to weld 20 mm thick 2205 duplex stainless steel.The effect of welding line energy on the content and properties of austenite phase in each region of welded joints was studied.The post-weld heat treatment of welded joints was carried out to obtain the effect of post-weld heat treatment on the microstructure and properties of welded joints.The microstructure of the welded joint was analyzed by metallographic observation,EDS energy spectrum analysis and scanning electron microscopy.It is found that the austenite content of the weld and heat affected zone of the submerged arc welding sample is in the range of 30%-70%,which meets the classification society standard.When the welding speed decreases and the welding line energy increases,the austenite content increases.When the welding line energy increases to about 1350J/mm,the austenite content begins to decrease as the welding line energy continues to increase.In the range of welding line energy and welding speed involved in the test,the content of austenite element nickel in the weld did not decrease with the increase of welding line energy.The mechanical properties of welded joints were tested by microhardness,tensile,bending and impact tests.It is found that the welding speed and welding line energy range of20 mm thick duplex stainless steel submerged arc welding joints meet the requirements of the specification are 12.1-14.6mm/s and 1345-1547J/mm.In the optimized welding process interval,the transverse tensile strength of the welded joint is about 886 MPa.In the bending test,there are only two cracks 1.5mm in the bending test.The impact energy is about 35J,and the hardness value is about 292HV_0.2.Its mechanical properties meet the requirements of the classification society.With the increase of austenite content,the impact toughness of welded joints increases,so the impact toughness of welded joints increases first and then decreases with the increase of welding heat input.Comparing the two welded joints with or without post-weld heat treatment,it was found that the inclusions in the impact fracture of the welded joints after post-weld heat treatment were significantly reduced,and the impact toughness was improved.The corrosion resistance of welded joints was studied by pitting corrosion test and polarization curve test.It was found that the chromium content in the post-weld heat treatment sample increased,the difference between the chromium element and the molybdenum element content affecting the Pitting Resistance Equivalent Number（PREN）decreased,and the content of poor chromium inclusions also decreased.The corrosion resistance of the post-weld heat treatment welded joint was improved because of the potential potential difference and the reduction and reduction of poor chromium inclusions.