Research On Slag-free Self-shielded Flux-cored Wire And Its Hardfacing Alloy Properties

Self-shielded flux-cored wire is a new type welding material, which can achieve self-protective welding through the alloy elements of flux-core in the welding. High properties of hardfacing alloy can be obtained when overlaying several layers on the matrix surface. And it is widely used in the manufacture and maintenance of the components like coal grinding roll and roller mill. In the current, the cost of commercial self-shielded flux-cored wire is very high, because the addition of alloy elements is generally large, and most of them are noble metal elements. The subject is hoped to obtain low cost and good properties of the micro-slag self-shielded flux cored wire by adding alloying elements. In this paper, the composition design, welding technological property and the properties of surfacing alloy were studied systematically, and the effects of various substances on the welding properties in the flux-cored were also discussed. The practical value results as follows:1. Through a series of experiments, it was clear that a reasonable allocation of Si, Mn, TiO2, potassium titanate, CaF2, sodium fluoride, CaO, Al and Mg, which can only produce a small amount of slag and the slag can fall off, and then played a protective role. And figure out the effects of graphite content on the welding properties in the flux-cored. The open arc surfacing welding arc could be stable and the gas holes in the surface layer would disappear when the graphite content was1.5wt.%.2. Adding a small amount of B, W and rare earth Y on the basis of the Fe-Cr-C alloy can further improve the properties of the hardfacing alloy. Using boron carton instead of graphite can increase transfer coefficient of carton and augmented the amount of (Fe, Cr)7C3, also the area fraction of carbide can reach37.14%. Adding to scruple of B and W based on high carbon and high chromium, microscopic structure consisted of big massive primary (Fe, CO7C3style carbide and Fe2B and WC and austenite and martensitic structure, the area fraction of carbide reached42.23%, surface macro hardness reached as high as61.6HRC. The rare earth Y played a heterogeneous nucleation effect in Fe-Cr-C-B-W-Y surfacing alloy system, microscopic structure was tiny (Fe, Cr)7C3style carbide which scattered in eutectic structure, the area fraction of carbide reached42.09%, surface macro hardness reached59.6HRC. Surfacing alloy performed a favorable metallurgical bonding with the matrix, and the hardness distribution was uniform.3. On the basis of the above experiments, there were three compositions in the formulation of modified Fe-Cr-C hardfacing alloy can be obtained, they were Fe-25wt%Cr-3. lwt%C-0.6wt%B, Fe-25wt%Cr-3.1wt%C-0.6wt%B-0.7wt%W and Fe-25wt%Cr-3.1wt%C-0.6wt%B-0.7wt%W-0.05wt%Y. And the properties of Fe-25wt%Cr-3.1wt%C-0.6wt%B-0.7wt%W flux-cored wire was comparable with Stellite Delcrome943-o, which possessed commercial prospects.