| The manufacturing process of stainless steel and chromium alloy steelrequires a large number of Medium and low carbon ferrochrome. Liquid-phasedecarburization of high-carbon ferrochrome powders(HCFP) is graduallylimited by environmental protection because metallurgical chrome slag is a kindof harmful solid waste produced in the productive process. Therefore, it isurgent to find a new methed of the decarburization of high-carbon ferrochrome.The solid-phase decarburization has the advantage of low energyconsumption, relatively low reaction temperature, but it is affected by particlesize, quality, and flow dynamics and other factors which lead to relatively poordynamic conditions of gas-solid decarbonization and a long time fordecarbonization. The microwave has the advantage of selective reaction, rapidheating, high efficiency heating. In this paper, the microstructure of HCFP,which was heated by microwave spouted fluidized bed, was studied. Thedecarbonization effect and differences in microstructure of HCFP decarburizedwith different experimental conditions were comparatively researched. The sticking and defluidizing phenomena and the oxidation degree of decarbonizedmaterial were studied in some degree. The main conclusions are as follows:1.The metallographic organization structure of HCFP is mainly white bulkylumps phase (Cr,Fe)7C3as the matrix phase, which is hexagonal prism shape orlong cylindrical shape, occupying more than80%of the total phase, as well assmall amounts of gray irregular shape phase (Cr,Fe)23C6and Chromium ferritic(CrFe) filled in (Cr,Fe)7C3matrix phase.2.In the condition of HCFP heated to800℃,900℃,1000℃and preservatedfor1h,2h,3h in the microwave spouted fluidized bed, with the extension of theheating temperature and holding time, the decarbonization effect of material ismore obvious. The decarbonization percentage of HCFP decarbonized in800℃for1h (9.73%) is minimum. The decarbonization effect of material heated in1000℃for3h is best. The decarbonization percentage is49.64%.3.In the different microwave flied heating condition,(Cr,Fe)23C6–CrFephase gradually extended from the star-like form to densely interwoven mesh. Inthe condition of900℃for3h, the area of (Cr,Fe)23C6–CrFe or (Cr,Fe)7C3isabout50%in the total phase area.4.By the XRD analysis, in the condition of800℃for different preservationtime, Each of the crystalline of HCFP decarbonized is basically same. Widedegree of peak is slightly different for each phase. In the condition of900℃and1000℃, there are significant differences between each wide degree of peak andother experimental condition. Oxide phase Cr2O3has been detected in the decarburization material except the sample which had been holding in800℃for1h and2h.5.With the improvement of temperature and holding time, the degree ofoxidation of the HCFP decarbonized,of which partical size is under0.15mm，isgradually increasing. The maximum partical size of oxidation in the HCFPdecarbonized in1000℃is32.0um. The range of oxidation partical size isbetween4.0to27.0um.6.In the HCFP decarbonized partical size within0mm to0.15mm，Theminimum mass fraction of Cr oxidized is13.4%, the maximum one is21.2%.The content of Cr unoxidized is more than the minimum standards required forproduction. In the HCFP decarbonized partical size bigger than0.15mm, theoxide phase does not appear. It meets industry standards.7.There is no defluidizing phenomena in the test，but some sample stickstogether. With the improvement of the temperature and holding time,ferrochrome powder gradually changed from bright white to black. The mass ofHCFP decarbonized partical size within0.270mm and0.180to0.270mm ismuch heavier than the raw material. The mass of HCFP decarbonized particalsize within0.075to0.045mm and less than0.045mm is much lighter than theraw material. The HCFP decarbonized partical size within0.150to0.106mm isa little heavier than the raw material, but it dose not change significantly. |
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