Microstructure Of High-carbon Ferromanganese Powders With Addition Of Calcium Carbonate Decarburized In Solid-state By Microwave Heating

High-carbon ferromanganese powder with addition of calcium carbonate powder can be achieved depth effect of decarburization of high-carbon ferromanganese in solid-state in microwave field. And the residual pure calcium oxide can be added to achieve dephosphorization and desulphurization effect during the steel decarburization as the auxiliary of ferromanganese. It is necessary to understanding the phase composition and microstructure of this new pattern metallurgy material in the theoretical and practical.In this paper, methods such as carbon content analysis, metallographic analysis, electron probe microanalysis, XRD phase analysis and experiment contrast were used to study the the metallographic structure and material phase composition of the materials of high-carbon ferromanganese powder with addition of calcium carbonate decarburization in solid phase by microwave heating and by muffle furnace. And then the heating characteristics of the material in the microwave heating field and conventional heating field, the effect of different heating methods to the decarburization, and explored the non-thermal effects of microwave heating field to solid state reaction of role in promoting. The main findings of this paper as follows: (1) The microstructure of high-carbon ferromanganese are mainly mosaic structure, encroachment and parcel structure, phase composition are mainly carbon-rich carbide phase (Mn0.86Fe0.14)7C3, content accounted for about47%; intermediate carbide phase(Mn0.80Fe0.20)5C2, content accounted for about32%; metal-rich carbide phase (Mn0.78Fe0.22)23C6, content accounted for about21%. In addition to containing ferromanganese carbide phase, there are Fe3C, Fe3Si, Fe0.4Mn3.6C, Mn15C4and free graphite phase in high-carbon ferromanganese.(2) The materials of high-carbon ferromanganese powders mixed with calcium carbonate powders with good microwave absorption, specific heating rate according to different decarburization molar ratio (CO2calcium carbonate powders:C high-carbon ferromanganese powders) can be in10℃/min·kg～50℃/min·kg. Heating the materials of same ratio, the average specific heating rate of microwave heating is faster than the average specific heating rate of the muffle furnace heating, to extend the decarburization time and improve the decarburization temperature helps decarburization. Under the same conditions of the insulation decarburization time and the decarburization temperature, the higher the decarburization molar ratio, the lower the carbon content of the decarburized materials, the better the decarbonization effect.(3) In the experimental conditions (decarburization tempreture are900℃,1000℃,1100℃,1200℃, insulation decarburization time is60min) the same case, the decarburization rates of microwave heating high-carbon ferromanganese powders with addition of calcium carbonate powders decarburization in solid phase were76.70%,82.90%,84.12%and85.78%, far above the muffle furnace heating solid phase decarbonization rate of31.92%,57.19%,58.85%and88.05%, especially in the low temperature, indicating that there is non-thermal effects in the microwave heating field, this non-thermal effects can significantly enhance the diffusion of carbon in the high-carbon feiromanganese powders, greatly improve the reaction dynamics of decarburization in solid phase. Decarburization reaction kinetics of conventional heating conditions significantly affected by temperature control, the higher the temperature of the solid phase decarburization, decarburization rate of the high-carbon ferromanganese powders will be higher.(4) Decarburization in solid phase of high-carbon ferromanganese powders with addition of calcium carbonate powders can achieve depth decarburization of high-carbon ferromanganese in microwave heating field, the decarburized materials showed the unique spherical layered structure, the spherical shell-like structure and the solid spherical structure which is mainly composed of metal manganese, metal ferromanganese phase, content accounted for about58%; metal-rich carbide phase, content accounted for about19%; calcium oxide phase, content accounted for about23%; in which residual pure calcium oxide can assist decarburized ferromanganese to desulfurization and dephosphorization in the molten steel process. When the decarbonization state in solid phase, the microwave heating field can promote the fusion of the metal of the same kinds of metal elements, metallic phase separation of the different kinds of metal elements. The best overall decarburization effect was achieved when the decarburization temperature is900℃, the oxidation degree of decarburized materials is in a low level and without manganese calcium and other ingredients.(5) The metal ferromanganese phase in decarburized materials of muffle furnace heating showing the irregular shape of the butterfly-like structures and solid spherical structures of different sizes, decarburized materials are only metal ferromanganese without single metal manganese or iron phase. Conventional heating does not appear similar phenomenon to microwave heating which to promote the same kind of metal aggregation, dissimilar metal separation.(6) When the decarburization temperature is same, the degree of oxidation of the microwave heating decarburized materials is significantly lower than the degree of oxidation of the muffle furnace heating decarburized materials, indicating that in microwave heating field, the diffusion of carbon in high-carbon ferromanganese powders is faster than the oxidation speed, the degree of oxidation is lower; while in conventional heating field, the rate of diffusion of carbon in high-carbon ferromanganese powders is slower than the oxidation rate, not only decarburization less effective and the degree of oxidation of the metal ferromanganese is relatively high.