The Effect Of Electric Pulse Treatment To H13Steel Welded Joint On Microstructure And Performance

With the development of times, the advancement of science and technology and theimprovement of industrial level, mechanical manufacturing industry relys increasingly on mouldmanufacturing, the level of mould manufacturing has become the main measuring standard andrestriction factor of the national industrial level. Hot work mould occupies half of the moldproduct. Hot work mould works under complicated conditions, it needs to bear high temperatureand high pressure and impact load, In addition to this, it also works under complex stress, suchas bending and torsion, so it is easy to produce failure such as fracture, deformation, wear andfatigue. In the past, failure in the mould is usually irreversible. Once failure, just be scrapped.Changing to new mould will be faced with high cost and long cycle, which will bring big loss toenterprise.As a traditional thermal processing method, welding is called “sewing of steel”. With thedevelopment of welding technique, using welding to repair the damaged mould is attractingpeople’s attention. It has the advantages of low cost、short cycle and flexible operation, with heattreatment or other surface strengthening method it can improve the performance of the mouldmaterial, and then effectively improve the service life of mould. In recent years, as a transienthigh-energy treatment means, electric pulse treatment technology gradually stepped into people’shorizons. Studies have found that, electric pulse treatment can effectively refine microstructure、promote the healing of defects such as cracks、improve the mechanical properties of materials,and then improve the service life of hot-work mould.In this paper, the object of study is hot work die steel H13, which is widely used at homeand abroad. H13steel is welded with TIG welding, and then the specimen are treated withquenched and tempered for group one, the other group is treated with electric pulse, analyzingthe changes both in microstructure and in mechanical properties producing in H13steel weldjoint before and after electric pulse treatment. Combined with the resistance test、X raydiffraction to explore the mode of action that electric pulse treatment improve the properties of H13steel weld joint. It is important to those moulds repaired by welding to optimize theproperties.It changes from thick lath martensite to fine tempered martensite after quenched andtempered, during the process it is accompanied by carbide precipitation. It changes to uniformhardness distribution after quenched and tempered, the hardening and softening of welded H13steel is eliminated, the gradient of hardness is no longer apparent. The strength of extension forH13steel weld joint increased from1473MPa to1571MPa after quenched and tempered, andthe elongation decreased.We found the length of martensite is shortened, the grains are refined, the orientation fadeout gradually after electric pulse treatment, which improve the uniform of specimen; the increaseon half width of X ray diffraction peak means the size of grains or subgrains decrease. Themicrohardness is improved after electric pulse treatment, especially in weld zone. The strength ofextension for H13steel weld joint increased from1473MPa to1572MPa after electric pulsetreatment, and the elongation decreased. The pulse current time is not in direct proportion to thedegree of grain refined, the microstructure gradually refined increase over pulse time, but whenthe time passed some critical value(or range), the effect for refining is not apparent.Electric pulse treatment can eliminate the defects in material, according to the resistancetests, the resistance value of welded H13steel decreased after electric pulse treatment, whichevidenced the defects or edge dislocations are weakened, even to be eliminated. Changingdifferent pulse current time to do the resistance test, it is found that the more decrease inresistance, the more increase over pulse time, but when the time passed some critical value(orrange), the range for decrease in resistance come to reduce.As a kind of new and green processing technology, electric pulse treatment is very valuable,a lot of studies have confirmed that it can refine the grains and heal the damages, neverthelessnow the mechanism for refining has not been definitely pointed out, it still needs more studies. Ibelieve that every step for researching will make electric pulse treatment more realizable appliedto actual production.