Comparative research on microstructure of high-carbon ferrochrome powders decarburized in solid-state by microwave field and conventional field

The effect of different heating fields on microstructure of the material was studied, which provided evidence for special effects of microwave heating field. The high-carbon ferrochrome powders (HCFP) with addition of calcium carbonate powders (CCP) was studied, and the microstructure of HCFP was also comparatively researched after being heated by microwave and conventional field. The results show that (Cr, Fe)7C3 in HCFP begins to decompose, and a small quantity of (Cr, Fe)23C6-(CrFe) forms on the edge of crystalline grain, when mixed material is heated to 900 ℃ by microwave heating. When heated by conventional field, the metallographic structure of HCFP has no obvious change; when the temperature raises to 1 000 ℃ and 1 100 ℃, by microwave heating field, (Cr, Fe)7C3 in HCFP disappears gradually. Meanwhile, a large amount of (Cr, Fe)23C6-(CrFe) forms and uniformly distributes in the matrix. But heated by conventional field, the content of (Cr, Fe)23C6-(CrFe) is low and with serious macro segregation. When heated to 1 200 ℃ by microwave heating, (Cr, Fe)7C3 almost completely turns into (Cr, Fe)23C6-(CrFe). While being conventionally heated to 1 200 ℃, a lot of (Cr, Fe)7C3 remain with very unevenly distribution, and the degree of oxidation is obviously higher thanthat of microwave heating. The solid state decarburization by microwave heating has the characteristics as follows: low temperature, fast and uniform reaction rate, low oxidation degree, which embody the superiority of microwave, and it can significantly improve the diffusivity of the carbon in HCFP.