Effect Of Welding Process On The Properties Of Joint Of 2205 Duplex Stainless Steel

Eighty percent of gas for the West-east gas transfer project is provided by Kera-2 gas field and it is playing a very important role in the project. The welding process of the SAF 2205duplex stainless steel pipes is studied by Yaiyuan Iron and Steel Group and our research group according to SAF 2205duplex stainless steel technical requirement of the project and API5LC,ASTM S32205 criteria.The key point of the welding process is the microstructure and properties of the welded joint, such as toughness and corrosion resistance, which will be influenced by the thermal cycling greatly. So it is necessary and academic to improve the mechanical properties and corrosion resistance of the joint by investigating the welding process of SAF2205duplex stainless steel.Two different welding process of plasma arc welding (PAW) +tungsten arc inert-gas welding (TIG welding) and plasma arc welding (PAW)+ metal inertia gas welding (MIG welding) with E2209 arc wire were applied to study the effect of welded process on SAF2205 duplex stainless steel. The optimum welding parameters are given according to the microstructures, the mechanical properties and the corrosion resistance of the joints welded by the two different methods. The effect of heat input, processes and the heat treatment after weld and etc. On the microstructure, the mechanical properties and the corrosion resistance of the welded joint were also studied.Both PAW + TIG welding and PAW+ MIG welding can reach the requirements of the West-east gas transfer project, and compared with TIG welding, the grains of the joint welded by MIG with less heat input is much finer. Through the tests of mechanical properties, both joints of SAF 2205 duplex stainless steel welded by MIG or TIG can reach the requirement of hardness. The fracture took place in the base metal during the tensile test, which indicated that the tensile strength of the joint is qualified; no cracks was observed through the bend test, which indicated that the bend strength is high enough; it has been improved that the impact toughness of both welding seam, fusion zone and HAZ can reach the ASTM A923 criteria through the Charpy-type test.The solution heat treatment make the grains of the weld seam and HAZ fine and promote the austenite mostly separate out at ferrite grain boundary with only a little austenite precipitated at the grain boundary of ferrite, but it has little effect on the base metal. The impact toughness became better after the solution heat treatment. Compared with that welded by TIG welding, impact toughness of the joint welded by MIG with less heat input is better. Both the pit corrosion resistance of the weld metal and HAZ of 2205 duplex stainless steel produced by two different welding methods can reach the ASTM G48 criteria. And that of the welded joint with solution heat treatment is better than that without solution heat treatment.The impact toughness of the pipe joints of 2205 welded by PAW+ TIG can reach the ASTM A923 criteria, and the tension strength can reach the API SPEC 5LC LC65-2205criteria and the bend strength of the welded joint is enough.