| Due to the favorable mechanical and corrosion properties, duplex stainless steels (DSS) are widely used in a variety of industry fields such as petroleum, chemical industry, ocean engineering as a substitute of the ordinary stainless steel. In practical application, the growing availability of saving the duplex stainless steel with relatively high price and improving economic efficiency creates a great needs for joining of dissimilar metals between duplex stainless steel and low alloy high strength steel, etc., so as to take full advantages of different materials and greatly decrease the production cost. However, the joining of dissimilar metals is generally more challenging because of great difference in chemical compositions, the physical and chemical properties of the base metals to be joined. If the welding technology is not well carried out, the dilution of weld metal and weld defects such as gas holes and micro crack, etc. will be produced in the welded joints during welding, and thus the application properties of joints will be greatly decreased. Consequently, the welding technology and weldability between 2205 DSS and 16MnR high alloy low strength steel are investigated in this paper. Three combinations of different welding processes associated with different filler metals are employed in the welding technology experiments, namely: (1) welding performed by GTAW with ER2209 wire; (2) welding performed by GTAW with ER309 wire; (3) welding performed by SMAW with E2209 electrode, respectively. In order to optimize the welding technology and get the most suitable joint, mechanical properties, microstructure and corrosion resistance of the welded joints were evaluated. In addition, the welding mechanism of dissimilar metals joint was also discussed, so as to provide theoretical and technological guidance for welding DSS dissimilar metals structure in practice application.The analyses of microstructural characterizations, chemical compositions and phase constitution of the dissimilar joints were conducted by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), together with X-ray diffraction (XRD) respectively. Results show that in the 16MnR-WM (weld metal) interface, a decarburized layer close to the fusion line at the side of 16MnR is formed as a result of the migration of carbon element, and there is a solidification transition region of about 20-50μm at the WM side. The analysis of solidification transition layer indicates that the variations of Cr, Ni contents decrease gradually and present the obvious characteristic of gradient distribution, and no deteriorative phases such as chromium carbide or martensite, etc. are produced in that region. However, in the DSS-WM interface, no great interface variation is generated, and the volume fraction of austenite phase content in DSS HAZ (heat-affected zone) is well controlled under the required range from 35% to 65%, which is advantageous to mechanical properties and corrosion resistance of welded joints. Moreover, the microstructure of weld metal consists of a certain percentage of austenite and ferrite, and all the three welded joints are determined by a large amounts of austenite content, which are beneficial for the mechanical and corrosion properties of joints.Results of mechanical properties tests of welded joints indicate that the fracture of the joints welded by GTAW occurred in the side of base metal 16MnR, while the fracture position of the joint welded by SMAW in 16MnR HAZ. The average tensile strength of three different welded joints are 582.4MPa, 579.7MPa and 564.6MPa respectively, all of which are higer than that of the 16MnR base metal with relatively low tensile strength and they can meet the tensile strength requirements of engineering structure. The impact toughness tests show that the impact toughness of weld metal is lower than that of DSS base metal, but it is higher than that of 16MnR HAZ and 16MnR base metal. What's more, the joint performed by GTAW with ER309 wire has the best impact toughness at experiment condition.Chemical immersion method and electrochemical test were used to evaluate the corrosion resistance of joints. Results showed that the resistance to intergranular corrosion is excellent of the three welded joints obtained by different welding processes. Pitting corrosion is the main way for weld metal, and the joint performed by GTAW with ER2209 wire has the better capability of pitting corrosion resistance under the experiment condition.As described above, the joint performed by GTAW with ER309 wire can get the best mechanical properties, so this welding technology is the most suitable for less demanding for corrosion resistance engineering structure. While the joint performed by GTAW with ER2209 has good mechanical properties associated with the best corrosion resistance, consequently this welding technology is the most suitable for the engineering structure of which demans for corrosive environment.
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