Study On Electrical Signals And Weld Appearance Of Underwater Dry Flux-cored Wire Pulsed Welding Of Duplex Stainless Steel

Underwater welding is a special welding method which is carried out in the underwater environment. It is one of the important technology of unclear power and marine resources exploration, and is of great importance to the installation and maintenance of the underwater engineering facilities. Duplex stainless steel has been widely used in petroleum, chemical, paper and other fields. In recent years, it plays an important role in the application of nuclear power facilities and deep sea oil projects. Since underwater dry welding gets the best quality among the variety of underwater welding methods, it has been widely used in the installation and maintenance of the nuclear spent fuel pool and marine engineering facilities.In the process of welding, electrical signals can reflect the characteristics of weld quality in a certain extent. It can provide theoretical basis for improving the effect of underwater welding by researching the characteristic of the electrical signal which is got from duplex stainless steel underwater welding test. Moreover, the weld geometry is one of the important factors affecting the mechanical properties of the welding joints, and it is an important research content of the duplex stainless steel under water welding technology. In this paper, underwater dry flux-cored welding test of duplex stainless steel is conducted in hyperbaric chamber, and the electric signal of the test is got and analyzed. The average current, base current, duty ratio and pulse frequency are as the four independent variables, a four factors and five levels testing program, which is based on respond surface method, is designed. Combined with the weld appearance, an evaluating indicator, current stability coefficient, which can evaluate the stability of the electric signal and welding quality, is designed. The current stability coefficient, weld reinforcement, weld width, penetration depth are as the responses, the mathematical models between the welding parameters and them are established. Finally, the influence of a single welding parameter and interactions between them on electric signals and the weld geometry size is analyzed. It results show that:With the increase of average current, base current and pulse frequency, the signal stability increased, then it is reducing. With the increase of duty ratio, signal stability is improving. When the average current is 220 A, the signal gets most stable in 45 Hz. But as the increase of the average current, the best pulse frequency is reducing.The influence of the average current on weld geometry size is the largest, followed by the duty cycle, and the influence of pulse frequency and base current are relatively weak. The penetration depth increases with the average current, but reduces with the increasing base current and duty ratio, and with the pulse frequency increased, it is reducing. The weld reinforcement increases with the increasing average current, base current and duty ratio, but reduces with the increasing pulse frequency. The weld width increases with the increasing average current and pulse frequency but as the base current and duty ratio increased, it reduced.