烧结矿矿相特性研究
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摘要
以现场烧结矿为研究对象,在实验室中采用XRD分析、光学显微镜定量观测、EPMA分析和纳米力学测试等方法,研究烧结矿矿相特性,并从烧结微区成分、烧结温度和褐铁矿反应行为等方面,探讨返矿形成机理。试验研究表明:(1)烧结矿矿物主要包括赤铁矿、磁铁矿、铁酸钙和玻璃相,成品矿中矿物组成以铁酸钙和熔蚀形磁铁矿为主,并伴有大量的二次赤铁矿,原生矿比例较低;而返矿矿物组成含有较多的自形晶磁铁矿和二次赤铁矿,铁酸钙含量较低,且部分铁酸钙呈细密针状结构与原生赤铁矿共生,细粒级中含有较多的原生褐铁矿。(2)不同形貌的复合铁酸钙中,枝晶状铁酸钙Si O_2和Al_2O_3含量较低、二元碱度和Fe_2O_3与Ca O的摩尔比较高;而板、块状铁酸钙Si O_2和Al_2O_3含量较高、二元碱度和Fe_2O_3与Ca O的摩尔比较低。(3)烧结矿矿相中,赤铁矿硬度较高,硬度值为18~22 GPa;铁酸钙、磁铁矿硬度次之;而玻璃相硬度最低。返矿形成机理方面,分析认为:低碱度微区形成的自形晶磁铁矿和玻璃相的矿相组织、烧结温度偏低区域形成的SFCA-I和原生赤铁矿的矿相组织、原生褐铁矿本体及其周边反应区域的矿相组织,上述矿相组织抵御外力冲击能力较弱,易于形成返矿。
The properties of sinter mineral phases were studied by the means of XRD,microscope quantitative observation,EPMA,nanoindentation technique,and the formation mechanism of return fines was discussed by the factors of sinter microregion composition,sintering temperature,reaction behaviour of pisolite. The study shows:(1)Sinter mineral assemblage is mainly composed of hematite,magnetite,calcium ferrite and glass. Furthermore the mineral assemblage of sinter product is of a great deal of calcium ferrite and melt-erosive magnetite,together with abundant secondary hematite and a small amount of primary iron ore,whereas the mineral assemblage of return fines is of plentiful euhedral magnetite and secondary hematite,with a large amount of primary pisolite in< 1 mm particle size and relatively less calcium ferrite,in particular some calcium ferrite coexisting with primary iron ore presents fiber-like microstucture.(2)Dentritic calcium ferrite has less SiO_2 and Al_2O_3,higher basicity( wCaO/wSiO_2) and molar ratio of Fe_2O_3 and CaO,whereas platy and blocky calcium ferrite have more SiO_2 and Al_2O_3,lower basicity( wCaO/wSiO_2) and molar ratio of Fe_2O_3 and CaO.(3)Hardness of hematite is the highest( 18-22 GPa),hardness of calcium ferrite and magnetite are relatively lower,hardness of glass is the lowest.In terms of formation mechanism of return fines,these sorts of mineral phases & microstructure,which are euhedral magnetite and glass formed in microregion with low basicity,SFCA-I and primary iron ore formed in region with relatively low sintering temperature,primary pisolite and its nearby reacted region,are inclined to form return fines because of their weak ability to resist external shocks.
The properties of sinter mineral phases were studied by the means of XRD,microscope quantitative observation,EPMA,nanoindentation technique,and the formation mechanism of return fines was discussed by the factors of sinter microregion composition,sintering temperature,reaction behaviour of pisolite. The study shows:(1)Sinter mineral assemblage is mainly composed of hematite,magnetite,calcium ferrite and glass. Furthermore the mineral assemblage of sinter product is of a great deal of calcium ferrite and melt-erosive magnetite,together with abundant secondary hematite and a small amount of primary iron ore,whereas the mineral assemblage of return fines is of plentiful euhedral magnetite and secondary hematite,with a large amount of primary pisolite in< 1 mm particle size and relatively less calcium ferrite,in particular some calcium ferrite coexisting with primary iron ore presents fiber-like microstucture.(2)Dentritic calcium ferrite has less SiO_2 and Al_2O_3,higher basicity( wCaO/wSiO_2) and molar ratio of Fe_2O_3 and CaO,whereas platy and blocky calcium ferrite have more SiO_2 and Al_2O_3,lower basicity( wCaO/wSiO_2) and molar ratio of Fe_2O_3 and CaO.(3)Hardness of hematite is the highest( 18-22 GPa),hardness of calcium ferrite and magnetite are relatively lower,hardness of glass is the lowest.In terms of formation mechanism of return fines,these sorts of mineral phases & microstructure,which are euhedral magnetite and glass formed in microregion with low basicity,SFCA-I and primary iron ore formed in region with relatively low sintering temperature,primary pisolite and its nearby reacted region,are inclined to form return fines because of their weak ability to resist external shocks.
引文
[1]NICOLA V Y,SCARLETT Mark I,POWNCEBY Ian C,et al.Reaction sequences in the formation of silico-ferrites of calcium and aluminum in iron ore[J].Metall.Mater.Trans.B,2004,35(5):929-930.
[2]Kowalski M,Spencer P,Neuschütz D.Slag Atlas[M].2nd ed.Verlag Stahleisen Gmb H,Düsseldorf,Germany,1995:127.
[3]Satoshi Machida,Koichi Nushiro,Koichi Ichikawa,et al.Experiment evaluation of chemical composition and viscosity of melts during iron ore sintering[J].ISIJ Int.,2005,45(4):520.
[4]NATHAN A S,WEBSTER Mark I,POWNCEBY Ica C,et al.Effect of oxygen partial pressure on the formation mechanisms of complex Ca-rich ferrites[J].ISIJ Int.,2013,53(5):774-781.
[2]Kowalski M,Spencer P,Neuschütz D.Slag Atlas[M].2nd ed.Verlag Stahleisen Gmb H,Düsseldorf,Germany,1995:127.
[3]Satoshi Machida,Koichi Nushiro,Koichi Ichikawa,et al.Experiment evaluation of chemical composition and viscosity of melts during iron ore sintering[J].ISIJ Int.,2005,45(4):520.
[4]NATHAN A S,WEBSTER Mark I,POWNCEBY Ica C,et al.Effect of oxygen partial pressure on the formation mechanisms of complex Ca-rich ferrites[J].ISIJ Int.,2013,53(5):774-781.