| Reactor pressure vessel(RPV)is one of the most critical equipments in nuclear power reactor.In the manufacturing process of RPV,large area of corrosion resistant layer of stainless steel is required to be deposited on its surface.Due to the irregularity of the surfacing surface of the R zone of the inlet-outlet joint and the saddle surface of RPV,manual arc welding is still widely used at present.The efficiency of manual arc welding is relative low and the welding quality is deficient in stability.A set of robot hot wire TIG surfacing experiment system is built based on the traditional robot TIG welding in this paper,which can not only conduct efficient surfacing but also monitor the surfacing process by visual sensor and infrared camera.Scheme of the surfacing of stainless corrosion-resistant layer is finally formulated after studying the regularity of robot hot wire TIG deposition as well as the molten pool morphology and temperature state of deposited layer in the process of robot hot wire TIG surfacing,and conducting the performance testing for corrosion resistance layer.First,in order to improve the efficiency and stability of the welding process,a set of robot resistance-heating hot wire TIG experiment system is built based on traditional TIG experiment system,and efficient hot wire TIG surfacing can be achieve on the experimental system.Also,the monitoring of the welding process and the temperature field of the deposited layer can be realized through vision sensor and infrared camera.The peak current,wire-feeding speed and pulse frequency were selected as the main welding parameters through factorial design to study the regularity of hot wire TIG.Then,the influence law of welding process parameters on bead width,bead height and bead forming quality was clarified by means of response surface design.In the process of surfacing,visual sensor and infrared camera are used to collect and analyze the molten pool images and temperature images in the welding process under different welding parameters,so as to monitor the melting state of the molten pool and the temperature distribution of the welding passes in real time.The shape of molten pool can be directly reflected by contour extraction of molten pool image,and the depth of molten pool can be qualitatively reflected by boundary measurement of weld pass temperature image.After experiment analysis based on four groups of welding parameters,it can be found that when the peak current was set to 300 A,pulse frequency was set to 2HZ,and wire feeding speed was set to 3.5 m/min,the spreading areas of pool is small and the remelting effect on the previous layer is weak.After the characteristics of single-layer single-pass and multi-layer multi-pass surfacing were studied based on the rule of single-pass welding,four groups of welding parameters was designated with I=300A under DC constant current mode and I_p=300A,320A,350A under DC pulse current mode,then five specimen of corrosion resistant layer were made with these four groups of welding parameters.All of the five corrosion-resistant layer samples were evaluated through flaw and crack detection,microstructure observation and a series of physical and chemical properties testing according to relevant standards.The specimen made with I_p=350A can achieve high efficient surfacing,and meet the surface quality and performance requirements at the same time.Therefore,the final robot hot wire TIG surfacing scheme of stainless steel corrosion resistant layer robot is determined as I_p=350A,f=2HZ,V_f=3.5m/min. |
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