| Low-grade carbonate-oxidize manganese ore can’t be directly put into the smelting furnace and ferromanganese alloy powders generated in manufacturing process can’t be fully utilized which are two main problems facing by the ferroalloy enterprises. These issueses not only affect the process stability in the real process, but also de-crease economic benefits, that has become an urgent problem to be solved in enter-prise. Microwave heating has many advantages over conventional heating techniques, such as rapid and selective heating, volumetric heating, high efficiency, environmental friendly and fast switch on and off. It has been aroused widely attention in metallur-gical fields. Calcination of complex manganese ore by microwave and consolidate ferromanganese alloy powders by microwave sintering were studied and a new solu-tion method was provided to solve these problems.The present work attempts to investigate the calcine process conditions of the car-bonate-oxidize manganese ore by microwave. The manganese ore can be rapidly heated to 1000℃ from room temperature in 17 min with the average heating rate at 58℃/min. When the calcining temperature is 850～900℃, calcining time is 30min. The weight loss rate of calcined manganese ore is 15～19%. The TMn increase from 30% to 39～42% and the pulverulent ratio is 8～9%. The calcined manganese ore can be directly put into the smelting furnace.Thermodynamic analysis, XRD patterns and SEM analysis show that the decomposition process can be divided into three parts: MnCO3=MnO+CO2; 6Mn2O3=4Mn3O4+O2; CaCO3=CaO+CO2.The experiment of microwave melting and sintering ferromanganese alloy powders was investigated. The alloy powders can be rapidly heated by microwave and the smaller the particle size was, the higher heating rate was. Microwave melting ferro-manganese alloy powders experiment show that the best melting temperature is 1260 ℃ and the holding time is 10～20min. Thermodynamic analysis of alloy melt indi-cates that the carbon in material can prevent oxidation of other elements and decrease of the melting temperature can reduce manganese volatilization. Comparing with mi-crowave melting, microwave sintering process is simpler, more economic and effi- cient. The results show that sintering temperature, holding time and the content of-75μm powders significantly affect the properties and microstructure of sintering products. At the microwave sintering temperature of 1150℃, holding time of 10min and+75-150μm powders content of 50%, the value of compressive strength and vol-ume density of the sintered sample are 396MPa and 6.29g·cm-3, respectively. The chemical composition of ferromanganese agglomerates can be up to standard of FeMn78C8.0. SEM and EDAX analysis shows that the liquid phase formed in the sintering process leads to densification. XRD patterns indicate that the main phase of raw materials are Mn5C2 and Fe7C3 and the main reaction during microwave sintering is the decarbonization and carburization of iron carbide phase. The microwave sinter-ing process was optimized by response surface methodology. The optimum conditions are:sintering temperature of 1168.07℃, holding time of 10.58min,-75μm powders content of 62.18%. The predictions of compressive strength and volume density is 350MPa and 5.69g·cm-3, respectively.The experimental value have a good agreement with prediction. |
PDF Full Text Request