Developing On Production And Welding Technology Of Series Flux-cored Wire

Series flux-cored wire of arc welding and hardfacing for high strength steels applied in the field of marine engineering was developed and its welding technology was investigated.In the present work, the development and preparation of flux-cored wire, gas shielded flux-cored wire and self shielded flux-cored wire were firstly introduced. Then the influence of ingredient to flux-cored wire welding technology was stated in detail. Finally the research progress of hardfacing alloys and its flux-cored wire was presented.A series of basic experiments including the production technology of flux-cored wire was carried out. The pretreatment of flux powder, study on cross section morphology and drawing process of flux-cored wire, optimization of its preparation for obtaining wire product with stable quality can provide theoretical foundations and experience to the future research.With TiO2-CaCO3-fluoride-MgO as the main slag system, gas shielded flux-cored wire for600MPa high strength steels was studied. This type of wire possesses excellent weldability and can get deposited metal with good mechanical properties. Self shielded flux-cored wire, whose slag system is CaF2-Al-Mg, was employed to weld X70pipe line steel in arc welding method. Results show that the wire owns good weldability and yield strength of weld joints is qualified. Based on the main slag systems, formulation optimization was conducted, the effect of different ingredients of flux on weldability was investigated. By means of the analysis of microstructure and scanning electron microscope, it was found that the existence of Al inclusion in weld could decrease impact toughness of weld metal.Meanwhile, the influence of welding heat input to the properties of high strength steel weld joints during gas shielded welding was studied. It’s shown from the results that in the condition of three different heat input, namely10kJ/cm,15kJ/cm,20kJ/cm, the size of granular bainite in coarse grain zone of weld increased as the heat input raised. Softening of heat affected zone took place, and with the increase of welding heat input, the width and softening level of HAZ increased.On account of Fe-Cr-Mn-C alloy system and optimized activating fluxes, series flux-cored wires, including submerge arc welding, gas shielded welding and self shielded welding, was developed for surfacing process. CaF2-TiO2slag formation system was adopted for flux-cored wire of self shielded surfacing. Welding experiment using three surfacing flux-cored wire was carried out, the hardness and wear performance of deposited metal were evaluated. Results indicate that the weldability of three types of wire above was excellent and the deposited metal possessed good impact and abrasive resistance. From the further investigation, the weld metal was featured by work hardening, metastable austenite was prone to transform into martensite, which could improve the hardness and wear resistance of deposited metal. At the end, the application of self made surfacing flux-cored wire in the restoration of carbon steel wearable components was introduced.