Research On Slag System Of Self-shielded Flux-cored Wire For Hardfacing

Hardfacing is a technique which involves applying a layer of hard material to a substrate by welding method for the purpose of increasing the wear and corrosion resistance of substrate. Wearing the patch on the mechanical parts by hardfacing can extend the service life of components, save precious materials and lower manufacturing costs and so on. Hardfacing with self-shielded flux-cored wire can improve the efficiency and shorten the production cycle and reduce costs. There are great social and economic benefits to improve the safety and lifespan of machinery and equipment.According to the characteristics of a high carbon content in wear-resistant surfacing material, this paper has designed C-Al-CaF₂-MgO slag system which was used for the special hardfacing in reference to the traditional slag system. In this slag system, C was used as a deoxidation agent making full use of its deoxidation product CO to protect weld puddle; Al was used as nitrogen fixation and deoxidation agent; CaF₂ and MgO were used as the main slagging agent; K₂CO₃ was used as a stable arc agent; Si and Mn were united to be as a deoxidation. Around the slag composition on droplet transfer behavior of flux-cored wire, welding arc stability, slag coverage and de-slag and other aspects of the impact of the systematic study and discussion.The effects of slag system composition on droplet transfer formations of flux-cored wire and welding spatter were investigated by high-speed photography, by collecting droplets in a water through and test of spatter. The results showed that when C was 6%, Al was 10% and MgO was 8%, welding spatter was smaller, but it was more then 10%.During the welding process, current and voltage fluctuations were registered by surfacing by DEWE-TRANS, and arc voltage, welding current waveform diagram were generated. At the same time, the electric arc shape could be observed through the high-speed photography. The effects of slag system composition on welding arc stability of the flux cored wire were therefore studied. The results showed that when the contents of graphite increase, the welding arc stability became better; when the contents of Al and MgO increase, the welding arc stability was improved first, and then was deteriorated; when graphite was about 6%, Al was 10% and MgO was 8%, the welding arc stability was the best.The paper has investigated the slag system composition influences on slag covering ability and slag detachability by slag covering ability evaluating and slag detachability testing. The results showed that when the contents of Al and MgO increase, the slag had a tendency to become conglobation and slag covering ability became weak; increase of the contents of Al improved slag covering ability in some sort, while increase of the contents of MgO deteriorated slag covering ability, but on the whole the effect was little; when the contents of Al was 10%, MgO was 8%, the slag was covered well and it was easy to take off.Finally, the paper has acquired the slag system composition for the flux cored wire with favorable welding operation performance, i.e. graphite was 5%⁶%, CaF₂ was 30%, Al was 10% and MgO was about 8%.