| The high chromium cast iron flux cored wire is an important kind of hard facing material with good cost performance and excellent anti-abrasive wear performance, which is widely used in metallurgy, mining, cement, construction machinery, dredging equipment and many other fields. Flux-cored wire has many advantages, for example, the melting rate is high, automatic welding can be easily realized, deposited metal can be easily adjusted and more energy can be saved. Due to the reasons, much attention has been put on flux-cored wire and it is on behalf of the development direction of the surfacing material.The fill rate of flux-cored wire has limits especially when low-density component are added to the powder, the fill rate is difficult to improve. And the development of wear-resistant flux cored wires with high alloy content, high wear resistance and low-cost are greatly restricted. In this paper, a kind of coarse flux-cored wire of6mm diameter is designed and the fill rate of powder can be significantly improved. By now, there are two key issues urgently need to be solved when people develop and use the coarse flux-cored wire.The first issue is the relationship between alloying element content in the powder and the microstructure as well as property of surfacing metal.The second issue is the effect of thermal process during the welding on microstructure and property of surfacing metal.The current in flux-cored wire mainly flow through the peripheral strip around the wire and there are almost no current flows through the powder. In this paper, the heat flux distribution patterns of coarse flux-cored wire was built up based on current distribution characteristics listed above. The results showed that the maximum heat flux density of the coarse flux cored wire distributed on the circumference of the horizontal cross section of wire. And Bi-directional heat flux decreases gradually along the radial when leaving the circle. The author took the heat flux distribution pattern above as basis, analyzed the welding thermal process of coarse flux-cored wire by numerical simulation technology and calculated dilution rates under different welding parameters. The compositions of the surfacing weld were also calculated by dilution rates. And thermodynamic software "thermal calc" was employed to simulate the microstructure of the surfacing weld. The results showed that the simulation results of temperature field and microstructure were in good agreement with the test results. And the results made a basement for the design and application of the coarse flux cored wire.In the paper, the effect of vanadium, chromium and nitrogen alloying elements in the powder on the microstructure and properties of deposited metal was studied. The results showed that In the experimental conditions of this paper, V can refine the microstructure, when the addition amount is less than2%, the addition of V can improve the hardness of the surfacing layer. Chromium makes dendrites in the microstructure distribute more evenly, but it has little effect on the improvement of hardness. A very small amount of N (0.08%) will have a significant impact on the microstructure of the layer. Nitrogen can make the microstructure transit towards hypoeutectic and increase the content of primary austenite. Appropriate amount of added N can improve the macro-hardness of the surfacing layer, and make the hardness distributes more uniformly.The coarse flux cored wire was used to enhance coking components which work in high temperature environment and the lining of the pulverized coal injection pipeline which work in low-temperature abrasive wear working conditions. The service lives of the components are significantly increased. |
