Relation between Sinter Microstructures and Sinter Properties during Reduction

Sato, Katsuhiko; Suzuki, Satoru; Sawamura, Yasumasa; Ono, Kazuyoshi

doi:10.2355/tetsutohagane1955.68.15_2215

Cited by 17 publications

(17 citation statements)

References 1 publication

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“…According to the fitting patterns and the R factors, the observed diffraction patterns largely match the calculated patterns. Generally speaking, the ratio [44][45][46] of ingredients composing sintered ore is 40-70 mass% iron ores, 20-50 mass% ferrites (most of which are SFCA), < 10 mass% glasses, and < 10 mass% calcium silicates. The results (Table 2) of the XRD/Rietveld refinement are within these reported ranges.…”

Section: Figmentioning

confidence: 99%

Crystalline Phase Quantitation of Sintered Ore with Powder X-ray Diffractometry with Rietveld Refinement

et al. 2016

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X-ray diffractometry (XRD) with Rietveld refinement was applied to the crystalline phase analysis of two certified standard sintered ores (JSS 851-2 and JSS 851-5) and an industrial sintered ore (SO-1). An eskolaite (Cr 2 O 3 ) powder was mixed at 10 mass% with each sintered ore sample as an internal standard to correct for the effect of amorphous phase and unknown crystalline phases. The results of Rietveld refinement for JSS 851-2 were 23.0 mass% hematite, 29.5 mass% magnetite, 39.8 mass% silico ferrites of calcium and aluminum, 5.6 mass% dicalcium silicate, and 2 mass% amorphous phase, and these values are within the range previously reported for its phase composition. The elemental concentrations calculated from the crystalline compositions using Rietveld refinement of the three sintered ore samples were also in good agreement with the certified values and those from X-ray fluorescence analysis. A calibration curve method and a diffraction-absorption method for crystalline phase quantitation were used to validate the results of the powder XRD/Rietveld method, and the three results agreed well. The present method enables reliable determination of not only the major crystalline phases but also the amorphous phase present in the sintered ore.KEY WORDS: sintered ore; X-ray diffractometry; Rietveld refinement; internal standard.

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Section: Figmentioning

confidence: 99%

Crystalline Phase Quantitation of Sintered Ore with Powder X-ray Diffractometry with Rietveld Refinement

et al. 2016

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“…12) Many works have been done on the reduction and the expansion during reduction of these calcium ferrites. It has been reported that quaternary and part of ternary calcium ferrite decomposed into the wustite, which contains CaO, SiO 2 and Al 2 O 3 , and that they were reduced to metallic iron at the final reduction stage.…”

Section: Effect Of Al 2 O 3 In Cao-sio 2 -Wustite On Kmentioning

confidence: 99%

Effects of SiO2 and Al2O3 on the Lattice Parameter and CO Gas Reduction of CaO-containing Dense Wustite.

Inami

Suzuki

2003

ISIJ International

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The effects of SiO 2 and Al 2 O 3 on the lattice parameter and the initial reduction rate of CaO-containing wustite were studied at 1 273 K. Wustite plates containing 0.5-2 mass% CaO, 0.2-2 mass% SiO 2 and 1 mass% Al 2 O 3 were prepared at the mass fractions of CaO/SiO 2 ϭ0.5-5. The lattice parameter of CaO-SiO 2 -containing wustite decreased with decreasing CaO/SiO 2 ratio at a constant CaO content. This corresponded to a decrease of the dissolved content of CaO in the wustite due to a formation of CaO-FeO-SiO 2 compounds. Similarly, the dissolved content of CaO decreased in CaO-SiO 2 -Al 2 O 3 -containing wustite. The process of CO gas reduction within the wustite phase field was traced with the lattice parameter measurement of the partially reduced samples and was analyzed with a mixed-control model of chemical reaction at the surface and the solid state diffusion in the wustite. The chemical reaction rate constant, kЈ, decreased with increasing the amount of SiO 2 addition at a constant CaO content. The dependence of kЈ on SiO 2 (and Al 2 O 3 ) addition was in good accordance with the change in the dissolved content of CaO in the wustite owing to the formation of the compounds containing CaO. The inter-diffusion coefficient, D , tended to decrease slightly with increasing the amount of compound.KEY WORDS: wustite; CO gas reduction; chemical reaction rate constant; inter-diffusion constant; mixedcontrol model; lattice parameter; iron making. brated wustite samples was about 5.4ϫ10 3 kg/m 3 and slightly less than that of pure wustite summarized by Onoda and Sasaki. 4) The reduction experiments were conducted at 1 273 K by using a thermo-balance. CO-CO 2 -Ar gas mixtures (P CO 2 / P CO ϭ0.04 and 0.16, hereafter a), flowing at a rate of 2.5ϫ10 Ϫ5 m 3 /s, were used as reducing gas in order to avoid carbon-deposition from the gas mixtures. Under these conditions, the effect of gas-side resistance on the over all rate of reduction is negligibly small as demonstrated previously. 1) X-ray diffraction analysis was performed for the partially reduced sample and the change in lattice parameter in the depth direction of the samples was measured by stepwise polishing of the samples. As the lattice parameter has been reported to be a parameter corresponding to wustite composition, 5) the concentration profile of iron ion in the samples partially reduced was estimated from the lattice parameter profile measured. Moreover, morphological observation and analysis of elements on the section of samples were carried out with EPMA. Thereafter, prepared wustite samples were distinguished as follows: The SiO 2 -and CaO-SiO 2 -wustite denoted the wustite containing only SiO 2 and both CaO and SiO 2 , respectively. Experimental Results Lattice Parameter and Morphology of CaO-SiO 2 -Wustite before Reduction The dependences of lattice parameter on oxide content in 5) SiO 2 -, and Al 2 O 3 -wustite equilibrated with the CO-CO 2 gas mixture (Ksϭ50/50) at 1 273 K are shown in Fig. 1(a). The lattice parameter a increased linearly with an in...

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“…1) There have been many studies on the influence of pores and porosity on reduction, however, detailed information on the influence of pore diameter is only limited and the findings are often in disagreement with each other. For example, some studies show that a small pore diameter is beneficial for the reduction of sinter and pellets, 2,3) whereas other studies claim that large pores are beneficial instead. [4][5][6] Such contrasting claims are most likely a result of the difficulty in directly assessing the influence of the pore diameter.…”

Section: Introductionmentioning

confidence: 99%

Influence of Artificially Induced Porosity on Strength and Reduction Behavior of Hematite Compacts

Higuchi

Heerema

2005

ISIJ Int.

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With the objective to gain more fundamental understanding of the influence of pore structure on the lowtemperature reduction behavior of iron ore agglomerates, laboratory-scale induration experiments were performed using pure hematite compacts doped with naphthalene as a porosity-generating agent. The pore structure was thus controlled up to 60 % porosity and 1.4 mm pore diameter, and no mineralogical changes were observed in these ranges after induration. The cold strength of indurated compacts was higher with pores smaller than 0.125 mm in diameter, as well as with pores larger than 1 mm. Changes in the cold crushing behavior of indurated compacts are discussed based on matrix length and distribution theory. Reduction tests in CO-CO 2 -N 2 gas at temperatures in the range of 350-800°C revealed high strength after reduction of compacts with fine pores less than 0.125 mm in diameter. Reasons for this high strength were the isotropic stress distribution within the compacts, as well as lower expansion due to development of a complex reduction front.

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Relation between Sinter Microstructures and Sinter Properties during Reduction

Cited by 17 publications

References 1 publication

Crystalline Phase Quantitation of Sintered Ore with Powder X-ray Diffractometry with Rietveld Refinement

Crystalline Phase Quantitation of Sintered Ore with Powder X-ray Diffractometry with Rietveld Refinement

Effects of SiO2 and Al2O3 on the Lattice Parameter and CO Gas Reduction of CaO-containing Dense Wustite.

Influence of Artificially Induced Porosity on Strength and Reduction Behavior of Hematite Compacts

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