The welding with active agent has developed as a new joint technology in last decade because activate agent supplies a means
of significantly improving weld
penetration, performance and increasing the productivity of the welding process. The agent was employed mainly in TIG firstly, and has been applied successfully in welding of carbon steel, stainless steel, nickel based alloy and titanium alloy. Now the research on welding of aluminum and magnesium alloy with agent is ongoing. About the mechanism that activate agent can increase weld penetration, it was thought that arc visibly constricts in the presence of an activating agent, which improve arc energy density and arc force to pool,or that agent makes the pool to form a positive gradient and deeper weld penetration. Or both of them are playing role in increasing of weld penetration. With the development of ATIG, it will become a tendency that active agent will be used in other welding methods, such as MIG/MAG, PAW, and
laser welding. There are some elementary research results for penetration increasement and weld shape modification.