Research On Microstructure And Property Of Flux-cored Welding Wire Surfacing

Mould technique is not only a important symbol of national product manufacture level,but also decide the country's product quality,the benefit and the ability of developing new product to some extent.As the development of the industry,the requirement of the performance of moulds becomes higher and higher,the life question is prominent day by day.Surface strengthening technique plays a very important role in the mould industry,and draws extensive attentions.Metal powder-cored wire is the new tendency of the international development in recent years,being considered a welding material instead of solid wire.This welding wire not only has the inherent properties of metal powder-cored wire such as with better welding quality,no-slag,highly efficiency and conveniently adjusting the alloying elements etc.,but also has the advantage of low hardness in as-welded good machinability,high hardness in as-aged and better wear resistance with customary working procedure on making or repairing equipments such as rollers when reasonable designing the alloys content.The author adequately makes use of the high-tempering in the required stress relieving working procedure.During this working procedure,the hardness of overlaying metal increases by the reason of austenite changing into tempered martensite and more chiefly the simultaneous precipitation of a lot of carbide by secondary hardening.This wire can solve the hard rolled problems of some solid wires with higher alloys while it can get over the conflicts of existing overlaying materials what are always possesed high hardness with poor machinability or low hardness,good machinability with poor wear resistance.Further,it also can overcome the interacting phenomena between welding beads and make the external hardness of overlaying metal homogenepus.Be sure it could be found the important significance in the overlaying of wear-resistant equipments.In this paper,two different flux-cored wires were selected to automatically hidden arc overlay weld,and the microstructure and hardness of overlaying alloy were analyzed systematically.Optical microscope,SEM and XRD were used to study the microstructure of overlaying alloy.The result shows that the microstructures include martensite,retained austenite and carbide.When dealing with stress relief, there is a phase transition from retained austenite in the tempering process,increase the content of martensite with the hardness increment.At the same time,much more hard phases have been obtained with the precipitation of alloy carbide,which is so-called "secondary hardening" phenomenon,stabilizing the hardness after tempering.Meanwhile,primary carbides and eutectic carbide combine with substrate more firmly,increasing the toughness of alloy accordingly.Results show that this kind of overlaying microstructures has good wear resistance,but also has high toughness.By the thermal fatigue resistance experiments of repeatedly heating and cooling,the probability of initial cracks in different cooling process was analyzed, and the mechanism for cracks initiating in this process was also analyzed.Using small amounts and muti-component alloy system,which is adding small amount,various-strong carbide formation elements to form high quality, muti-component and compound alloy strong carbides in overlaying metal.According to different alloy carbides having different effects in different range of temperatures, the adding of such alloy dements ensure overlaying alloy has good anti-temper softening property and good wear resistance,reducing the cost of alloy dements.