| Sinter ore was mainly composed of iron mineral phase and binding phase. The content of binding phase in sinter ore could be 30%～35%, and it generated from the low melting point compounds which generated by solid phase reaction during sintering process.The chemical and mineral composition of binding phase depended on component of raw materials, sintering temperature and cooling process of sinter. The chemical and mineral composition of binding phase would changed with the composition of raw materials and sintering technologies. In high basicity sinter, calcium ferrite was the main binding phase, and silicates for self-fluxing sinter.The physical properties of binding phase, including fluidity, liquid phase generative capacity, wettability and self-strength, have great influence to the sinter quality, due to relationships of fluidity with distribution of binding phase in sinter, liquid phase generative capacity with liquid amount in sintering process, wettibility with binding strength, and self-strength directly with sinter strength.This paper studied the effect of binding phase's physical properties on sinter strength, and discussed the proper composition of binding phase.The binding phase samples were made up with analytic reagents based on the binding phase composition obtained by EPMA analysis, and the physical properties were investigated. The results indicated that:(1) Calcium ferrite binding phase in high basicity sinterThe better fluidity of calcium ferrite binding phase was obtained at nCaO:nFe2O3=1:1 (with no other compounds); at nCaO:nFe2O3=1:1, the fluidity was deteriorated with addition of MgO, SiO2 and Al2O3.The liquid phase generative capacity of calcium ferrite binding phase was the best at nCaO:nFe2O3=1:1 (with no other compounds); at nCaO:nFe2O3=1:1, the liquid phase generative capacity was deteriorated with addition of MgO, was improved when proper contents of SiO2 and Al2O3 were added.The wettability of calcium ferrite binding phase was the best at nCaO:nFe2O3=1:1 (with no other compounds); at nCaO:nFe2O3=1:1, the wettability was deteriorated when MgO, SiO2 or Al2O3 was added.The best fracture and compression strength of calcium ferrite binding phase was obtained at nCaO:nFe2O3=1:2 without other compounds, the strength was the lowest at nCaO:nFe2O3=2:1; at nCaO:nFe2O3=1:1, the strength of binding phase was deteriorated with addition of MgO, proper contents of SiO2 was helpful for improving the fracture and compression strength, but Al2O3 was not favor for strength.(2) Silicate binding phase in self-fluxing sinterWith the change of basicity (w(CaO)/w(SiO2)), the better fluidity was obtained when basicity was 1.40. When basicity was 1.18, proper content of MgO could improve the fluidity of binding phase and the fluidity was improved with increase of CaF2 and FeO.The liquid phase generative capacity was the best at basicity 1.18; Under this condition (basicity 1.18), the liquid phase generative capacity was the best when the MgO content was 1.97%, and the liquid phase generative capacity was improved with increase of CaF2 and FeO contents..The best wettability was obtained at basicity 1.18; Under this condition (basicity 1.18), the wettability was deteriorated with increase of MgO contents, while the wettability was improved with increase of CaF2 and FeO contents.With the change of basicity, the fracture and compression strength was the highest at basicity 1.18, when the basicity was greater than or equal to 1.40, binding phase disintegrated after melting and cooling; at the same basicity 1.18, the self-strength decreased with increase of MgO contents, the self-strength increased when little CaF2 was added, and the fracture and compression strength was the highest when the FeO content was 3.86%.(3) Sintering ExperimentsAccording to the physical properties of binding phase, the proper composition of calcium ferrite binding phase was, nCaO:nFe2O3=1:1, w (SiO2) 3% without MgO and Al2O3; the proper composition of silicate binding phase was, basicity (w(CaO/w(SiO2)) 1.18, w(MgO) 1.97%, w(CaF2) 4.42%, w(FeO) 7.53%.The sintering pot experiments for high basicity sinter were carried on, the results were:The drum intensity increased with increase of basicity. At the basicity 2.0, the highest yield, the shortest sintering time and the highest utility coefficient for sintering pot was obtained. Under this condition (basicity 2.0), with increase of MgO content, the yield decreased, sintering time increased, utility coefficient for sintering pot decreased and drum intensity decreased; with decrease of SiO2 content, yield and utility coefficient decreased, sintering time increased and drum intensity decreased dramatically; with increase of Al2O3 content, the yield and utility coefficient decreased, sintering time increased and drum intensity of sinter decreased.Summarily, the drum intensity increased with increase of basicity, but the TFe decreased sequently and the basicity should not be too high; with addition of MgO and Al2O3, the drum intensity decreased; proper content of SiO2 was important for the generation of definited liquid phase in sintering process, when the content of SiO2 in iron preparation concentrate was low, the basicity should be increased to guarantee the generation of definited liquid phase. The high strength of the third generation sinter could be explained reasonably based on the physical properties of silicate binding phase.
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