Welding Procedure And Performance Analysis Of Incoloy825 Fe-ni Alloy Composite Pipe

As one of alloy Ni-Fe-Cr based alloys,with good resistance to stress corrosion cracking and excellent point corrosion properties, Incoloy825 iron-nickel alloy are mainly used in the heating pipe of sulfuric acid pickling plant, vessel, acid gas environment pipelines, the air heat exchangers of oil refining, water cooled heat exchangers and piping systems. However, due to higher prices, the application of Incoloy825 iron-nickel alloy tube is relatively small. Currently, in order to solve the contradiction between cost and performance in engineering, Incoloy825 iron-nickel alloy composite pipe(the lining material is Incoloy825 iron-nickel alloy, the primary material is a low alloy steel) is developed and applied. According to the manufacturing method, this pipe can be divided into mechanical pipe and metallurgical complex pipe. The application of Incoloy825 iron-nickel alloy composite pipe solves the problem of large-scale applications for Incoloy825 iron-nickel alloy in engineering, and the pipeline service life improves significantly. But as a new material, the welding process and the joint microstructure of the pipe has a significant impact on its performance.In this paper, a variety of welding process tests and feasibility studies on the Incoloy825 iron nickel alloy composite pipe used in the onshore natural gas recovery project are carried out, Some physical and chemical experiments have been carried out on the joint performance of some of these processes, and the results have a guiding role for the engineering construction.We mainly detected the joint of Incoloy825 iron nickel alloy composite tube in this paper, including the back filled with argon and nitrogen gas protection; tested and analyzed the joint of low alloy steel wire protecting cover filling process under the condition of self protection; and studied on the feasibility of our GMAW welding backing down technology.The argon welding union welding process was carried out in two kinds of welding materials at home and abroad, and the process performance was compared, and a variety of performance tests including stress corrosion, intergranular corrosion and pitting corrosion are also carried out for the two kinds of joints. Test showed that the imported material is superior to the domestic welding materials in operating performance.The main purpose of the technology of self-protective low alloy steel is to verify the welding of low alloy steel welding wire on nickel base and its effect on the microstructure and properties. The experimental results are consistent with the theoretical analysis. It shows that the filling of the low alloy steel wire is not feasible in the welding of Incoloy825 iron nickel alloy composite pipe.In order to improve the welding efficiency and reduce the cost, this paper also studied the feasibility of the downward welding process of Incoloy825 iron nickel alloy composite pipe, the results show that the downward welding process can meet the need of the welding process from the aspect of the welding operation.