| In recent years,China's implementation of the "coal to electricity" policy has brought new opportunities for development of the electrothermal alloy industry.Fe-Cr-Al alloy is the most widely used electrothermal alloy in China.The alloy is resistant to high temperature,corrosion,oxidation and radiation,and can be widely used in nuclear power,porous materials,automotive and power generation,electric heating and other fields.At present,the most excellent performance of commercial iron-chromium aluminum alloys is the Kanthal brand in Sweden.Kanthal APMT and AF series alloys are well-known worldwide because they are formed by powder metallurgy,This series of alloys has excellent performance,high efficiency,and has a broad market,but its specific preparation process is rarely publicly reported.The present work is financially supported with the project of school-enterprise cooperation and is based on the feasibility of industrial production of high-performance iron,chromium and aluminum.The two processes of electroslag remelting method and powder metallurgy method are designed to produce iron-chromium aluminum alloy wire,which is divided into two process routes.The structure and performance of the alloy under various technological conditions were studied.The processing and serviceability of the alloy were optimized through the heat treatment process.The high-temperature oxidation resistance of the two processes was studied in depth and the oxidation mechanism was discussed.First,vacuum induction smelting prepares master alloy bar stock,which is then subjected to electroslag remelting and aerosolization with inert gas to produce powder.The results show that:(1)The content of O and N is reduced to 16 ppm after electroslag remelting.18 ppm,can remove most non-metallic inclusions.The tensile strength of the master alloy ingot is low,and the grains of the electroslag ingot are coarse.The number and size of inclusions in electroslag ingots are more than that of powder metallurgical materials.(2)The atomized powder has a small particle size with good sphericity,high purity,no satellite ball.After cold isostatic pressing of the powder without binder,the green compact strength is low,and the density of the central part after sintering is high.There are aluminum nitride and carbide in the surrounding area and the pores are large.(3)After the alloys prepared with the two processes are forged,the powder metallurgical material(PMM)is maintained at a fine grain size of 10 ?m.The thermal expansion coefficient of PMM in the forged state is slightly smaller than that of the electroslag material(EM).The mechanical properties are even better,which can well suppress the brittleness of the alloy and significantly improve the high temperature performance of the alloy.Secondly,(1)In order to improve the processing performance of the alloy,the best performance of the room temperature tensile of the PPM is found through the heat treatment process,which is equivalent to the Kanthal brand,and the elongation is higher than Kanthal.The reason is that there are dispersed Y-Fe particles in the PPM.The high temperature creep resistance of the PPM is also comparable to Kanthal.(2)The fast life test results of the wire materials prepared by the two processes show that the oxide film of PMM has stronger adhesion and higher life value,which can reduce the aggregation of carbonitrides and reduce the unevenness of the alloy resistance.In terms of elongation after break,electrical resistance and resistivity,temperature drop,etc.,the performance of PMM is better than that of EM.Finally,the oxidation performance analysis was carried out,and it was concluded that PMM has better oxidation resistance,the oxidation rate constant is much smaller than EM.The oxide film of iron-chromium aluminum alloy oxidized at 1200 ? is ?-Al2O3,which is divided into two layers,the outer layer is thin and the inner layer is thick.The pinning of Y oxide at the interface between the oxide and the substrate improves the adhesion of the oxide film.Alloy powder prepared by the present paper in terms of tensile properties,fast life,and other oxide weight gain substantially Kanthal APMT,AF series to achieve the same performance.After the optimization of each process parameter,industrial production can be carried out. |
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