Structure And Properties Of Magnetic Controlling On Plasma Arc Surfacing Layer

With the rapid development of industry technology and continued increase of the degree of mechanization and automation, people pay more attention to hazard of parts wearing. It has a great economic significance that decrease grinding abrasion and increase mechanical wearing.Electromagnetic is applied to welding as a new welding technology in recent years. The applied longitudinal magnetic field promotes arc revolution, changes plasma jet of arc column and radial distribution of density of arc, affects the heating and melting of base metal and formation of weld. Experience shows that the introduced magnetic field can give an effective intervention to the transition of droplet, flowing of molten bath metal, crystalline and nucleation of molten bath and the process of crystalline growth. The magnetic field promotes the refining degree of primary crystallization structure, decreases the chemistry non-homogeneity, So it can strengthen hardness and wearing resistance of weld metal overlay and improve quality of surfacing deposit.This paper talks about plasma arc surfacing Fe-based alloy on low carbon steel with applied longitudinal magnetic field. The effect of the longitudinal intermittent reversible magnetic field on the surfacing deposit solidification structure and mechanical properties is studied and the relationship of different magnetic field types and material wearing resistance has been examined systematically. The mechanism for overlay welding metal during solidification by applied longitudinal magnetic field has been discussed intentionally. It shows the shape and distribution of hard phase in overlay welding, and makes theoretical analysis and preliminary discussion. Following are the main results:1 , The optimum parameters can greatly influence grain structure refinement in weld metal overlay;Under AC magnetic field of weld metal overlay is obtained better effect of electromagnetism stirring than DC magnetic field.2, The hard phase in weld metal overlay is distributed randomly without magnetic field;Regardless of DC or AC magnetic field, the hard phase in weld metal overlay is fine and distributed "the hexagon" in optimum parameters, then hardness and wear extent in weld metal overlay are higher.3, The result indicated: with the effect of DC longitudinal magnetic field, when the optimum magnetic field electric current is 3A, hardness in weld metal overlay is HRC66, wearing capacity AG=0.0417g;with the effect of AC longitudinal intermittent reversible magnetic field, when the optimum magnetic field electric current is 3A and magnetic field frequency islOHz, hardness in weld metal overlay is HRC68, wearing capacity AG=0.0318g.