The Effect Of Pulse Current To The Microstructure And Performance Of HHD Welded Joint

Since China’s accession to the WTO, global machining industry began to transfer tothe mainland of China, China is becoming the heart of the world’s manufacturing industry.In order to reduce the share of imports of high-grade die, in the development andproduction of the mold material to make a breakthrough and steadily improve the quality ofdomestic mold. In industrial production, the mold for a long time in alternating hot andcold environment, performance therefore be greatly affected, so the mold will often fatiguecrack even partial peeling. Order to reduce the die failure brought about by the increasedproduction costs, mold welding repair has become an important manufacturing techniques.In this paper, the new hot die steel (HHD) for the study, the use of flux cored wiretungsten inert gas welding the HHD steel welding test, respectively, to study the process ofheat treatment process and electrical pulse influence of the HHD steel welded joints andperformanceexplore the pulse current under HHD steel weld crack healing of law andhealing mechanism.In HHD steel flux cored wire Tungsten Inert Gas (TIG) welded joints, the organizationof the regional difference of form and uneven tissue distribution. Each surfacing layer weldsignificant difference between the first layer is the most coarse, the second, three, fourrelatively small organizations; the organization of the fusion zone of thick white ferrite, theferrite grain boundaries. a large number of needle-like carbide precipitation, resulting in thefusion zone as a weak zone of welded joints; the organization of the heat-affected zone ofgranular bainite and a small amount of martensite; the base metal in the welding process bythermal effect is smaller for the iron mixed microstructure of ferrite and pearlite.Quenching and tempering treatment, of HHD steel welded joint the HHD steel afterquenching and tempering treatment of welded joints of the regional organizations withvarying degrees of refinement. Carbides within the ferrite in the weld proliferation, dispersed in the ferrite matrix; the fusion zone of coarse ferrite disappears; the heat affectedzone of martensite into cementite; the organization of the base metal only morphologicalchanges occurred. Compared with welded the HHD steel when welded joints hardness afterquenching and tempering, the hardness of the weld and fusion zone of lower base metalhardness increased, no significant change in the heat affected zone hardness.Welded joint of the HHD steel swap quality processing imposed by the pulse currentin the weld zone, heat affected zone and base metal discovery refinement organization, andwith the increase of pulse duration, microstructure refinement results are obvious. Theeffect of pulse current, the HHD is steel welded joint tensile strength and elongationincreased, the hardness of the welded joints of the regional line. Weld cracks with varyingdegrees of healing signs within a certain range, the longer the pulse duration, the effect ismore obvious. Voltage of5V, pulse duration of460ms (23cycles), HHD steel welded jointmechanical properties.Pulse current to the new type of hot work die steel TIG welded joint to complete theprocess of heating to cooling in an instant, a large number of austenite grain growth beinhibited, for refining structures, the hardness and tensile strength of welded jointsaresignificantly improved, and the pulsed current weld cracks to some extent, to promotehealing. This means of disposing of applications in industry, can improve the mechanicalproperties of welding mold, the mold to have a longer life cycle.