Research On The Coupling Arc Electrode GPCA-TIG Weld Method

Gas Pool Coupled Activating TIG Welding is a new type of double layer shielding gas welding method which particularity lies in that its inner gas employs inert gas protecting the molten pool and tungsten electrode, and its outer gas employs activating gas or nitrogen or mixture gas of them importing nitrogen and activating elements to the molten pool in order to increase welding penetration significently and improve welding property. The welding formation and the welding property can be controlled accrrately by changing coupling degree. In this paper, quenching method is employed to preserve the distribution regularity and existing form of the high temperature molten pool, then AES, nitrogen oxygen analysis, XPS and EDS were employed to analyse this. The single transition behavior of nitrogen and oxygen are studied by the distribution regularity and existing form of the high temperature molten pool when the element transit by itself. The joint transition of nitrogen and oxygen was studied by the distribution regularity and existing form of the high temperature molten pool when the element transit jointly and the single transition behavior of nitrogen and oxygen.Specific to GPCA-TIG welding using oxygen as the outer shielding gas, AES is employed to analyze the oxygen distribution of the molten pool of metal, and its results indicate that there is a rich oxygen layer on the surface of the molten pool, that the oxygen was introduced in front of the molten pool and separates out in middle and back of the molten pool, that the oxygen distribution varies with the modification of coupling degree. Oxygen content of the molten pool of metal is higher analyzed by the nitrogen-oxygen analysis when the coupling degree is+2. XPS is employed to analyze oxygen existence form on the surface of the molten pool of metal, and its results show that oxygen on the surface of molten pool of metal mainly exists in the form of oxide. The same result was proved by EDS analysis of welding line. The transition behavior of oxygen was studied by the oxygen distribution regularity and existing form of the high temperature molten pool, conclusively, the transition process can be simplified as direct oxidation process and indirect oxidation process.Specific to GPCA-TIG welding using nitrogen as the outer shielding gas, AES is employed to analyze the nitrogen distribution of the molten pool of metal, and its results indicate that the distribution of nitrogen is uniform distribution as a whole and more nitrogen was absorbed in low temperature region. Nitrogen content of the molten pool of metal unchanged analyzed by the nitrogen-oxygen analysis when the coupling degree changed. XPS is employed to analyze Nitrogen existence form on the surface of the molten pool of metal, and its results show that nitrogen on the surface of molten pool of metal mainly exists in the form of atoms. EDS was employed to analyze Nitrogen existence form of the welding line, and its results indicate that the nitrogen content is below0.1%, so we can infer that nitrogen mainly exists in the form of atoms. The transition behavior of nitrogen was studied by the nitrogen distribution regularity and existing form of the high temperature molten pool, conclusively, nitrogen is introduced in molten pool in the form of atoms.Specific to GPCA-TIG welding using oxygen and nitrogen as the outer shielding gas, AES is employed to analyze the oxygen and nitrogen distribution of the molten pool of metal, and its results indicate that the rich oxygen layer on the surface of the molten pool of metal is thinner, and the distribution of nitrogen is uniform distribution as a whole. Oxygen and nitrogen content of the molten pool of metal is analyzed by the nitrogen-oxygen analysis, and its results show that the nitrogen content is higher and oxygen content is lower when the coupling degree is+2than the degree is0. XPS was employed to analyze oxygen and nitrogen existence form on the surface of the molten pool of metal, and its results show that oxygen on the surface of molten pool of metal mainly exists in the form of oxide, and nitrogen on the surface of molten pool of metal mainly exists in the form of atoms.The same result was proved by EDS analysis of welding line. The joint transition behavior of oxygen and nitrogen was studied by the oxygen and nitrogen distribution regularity and existing form of the high temperature molten pool and the single transition behavior of nitrogen and oxygen, conclusively, the joint transition process can be simplified as enter process and precipitation process. The joint transition process is interactional process, because the adsorption of nitrogen in the front of the molten pool was hidered by oxide, the separating of nitrogen in the back of the molten pool was hidered by oxide, the adsorption of oxygen in the molten pool surface was influenced by nitrogen.In this paper, the formation and the distribution of nitrogen and oxygen in the surface and centre of the molten pool were studied. It is very important to study sigle and joint transition behivor of nitrogen and oxygen in the surface of the molten, control the welding formation and welding quality during GPCA-TIG welding process, and promote the development of this welding method.