Effect of Milling Periods on the Iron Mill Scale Particle Size and Properties (original) (raw)
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The objective of this work is the recycling of mill scale formed during the steel hot rolling process with a reducing gas (carbon monoxide) in order to produce iron powder having characteristics required by powder metallurgy. The reduction was carried out at various temperatures (7501050°C) during different times ranging between 40 and 180 min in an atmosphere of pure CO. The produced iron powder was characterized by chemical analysis, x-rays diffraction, optical microscopy and scanning electron microscopy. These methods of investigation confirm the presence of iron, graphite and iron carbide (Fe3C) as the products of reactions. The maximum iron content (98.40% Fe) in the iron powder was obtained by reduction of mill scale at 1050°C for 180 min. A reduction annealing under hydrogen makes it possible to decrease carbon and oxygen content of the reduced iron powder up to acceptable values.
Investigation on Iron Ore Grinding based on Particle Size Distribution and Liberation
Transactions of the Indian Institute of Metals, 2020
In the iron and steel industry, the production of narrow particle size distribution (PSD) for pellet feed making with acceptable liberation of valuables from the iron ore is very difficult. This study has been carried out to achieve desired pellet feed with narrow PSD and maximum liberation of hematite from the iron ore. The iron ores have been collected from three different sources (mines in Karnataka state) and milled. The iron ores and the blend feed samples were analyzed in the Optical Microscope (OM) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) to understand the PSD and percentage of hematite liberation. The new approach is adapted to identify the retention time (RT) of the iron ore in the mill, and the total RT taken for the blend sample in the Bond's ball mill is considered as the reference grinding time for milling in the Laboratory Ball Mill (LBM). The desired narrow PSD (-150/? 10 lm) with acceptable hematite liberation is achieved at an optimal grinding time of 7 min in the LBM.
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Powdered form of iron typically < 250 microns is phrased as iron powder. Commercial manufacturing of iron powder is majorly restricted to atomization, carbonyl, electrolytic and reduction routes. Powders from the later three techniques generally cater to special iron powders applicable to non-powder metallurgy segments such as food fortification, chemical reagents, water purification, etc. In this work, mill scale iron powders are synthesized by thermo-chemical reduction of mill scale, a steel industry by product, and their properties are analysed and compared with commercial iron powders such as carbonyl, electrolytic and reduced. Chemical and physical characterizations such as Optical Microscopy, Scanning Electron Microscopy and X-ray Diffraction of the powders are performed. Obtained results reveal that, mill scale iron powders MIP and MIP45 possess good product properties. Especially, MIP45 grade exhibited finer particle size of D 50 < 30 microns and BET surface area of 0.63 m 2 /g along with Fe (T) > 98%, true density-7.55 g/cc, apparent density 2.67-2.83 g/cc, packed bulk density of 3.44 g/cc and good flowability. This product of mill scale with highest apparent density and good surface area is expected to qualify to new segment of applications along with other commercial iron powders.
Characterization of Mill Scale for Potential Application in Construction Industry
The physical and chemical characterization of mill scale is attempted in the current work and the literature available on the same is compiled as a part of systematic experimental investigations on the feasibility studies of mill scale as partial replacement of fine ABSTRACT The physical and chemical characterization of mill scale is attempted in the current work and the literature available on the same is compiled as a part of systematic experimental investigations on the feasibility studies of mill scale as partial replacement of fine ABSTRACT The physical and chemical characterization of mill scale is attempted in the current work and the literature available on the same is compiled as a part of systematic experimental investigations on the feasibility studies of mill scale as partial replacement of fine
Recycling of steel plant mill scale via iron ore sintering plant
Ironmaking & Steelmaking, 2012
Mill scale is an iron oxide waste generated during steelmaking, casting and rolling. Total generation of mill scale at JSWSL is around 150 t/day and contains 60-70%FeO and 30-35%Fe 2 O 3. To recover the iron, the mill scale must be smelted in a blast furnace or other reduction furnace; however, it is usually too fine to use without previous agglomeration such as via pellet or sinter mix. JSWSL operates a 4?2 Mtpa pellet plant to produce pellets for Corex and BF ironmaking units. The aim of this study is to determine the effect of mill scale on pellet properties. Detailed laboratory basket trials were conducted using up to 40% of mill scale in the pellet mix. The addition of mill scale up to 10% is considered to provide the optimum balance of chemical, physical and metallurgical properties of the pellet.
Particle Size Analysis of Coarse and Fine Ore Samples Experiment 1
—Particles are very important factors in the industry, because almost all products are made up of particles. Particles have different characteristics and one of that is the particle size. Since a particle and its size is a crucial factor in the industry then it is important that it must be analyzed, thus there is the Particle Size Analysis. This study attempts to do Particle Size Analysis on some samples of Coarse and Fine particles by sieving the particles and by plotting the gathered results using Gates-Gaudin-Schuhmann plot, Rosin-Rammler Plot and a 7-range Histogram. Data was gathered and the experiment was attempted. Results have been analyzed using the said 3 different plots.
Metallurgical and Materials Transactions A, 2001
The microstructure and the strength of an iron mechanically milled with various amounts of oxygen (i.e., 0.2, 0.6, and 1.5 mass pct) were studied. The samples were subjected to a mechanical milling in an argon atmosphere for 100 hours followed by consolidating bar rolling to a total reduction of about 86 pct at 700 ЊC. The microstructure of the steels sensitively changed depending on the oxygen content, i.e., on the volume fraction of the oxide particles. The average grain size decreased from about 0.7 to 0.2 m with an increase in the amount of oxygen. Moreover, the misorientation distributions of the grain boundaries were different in the samples with various amounts of oxygen. A relatively large fraction of low-angle boundaries arranged crosswise to the rolling axis was registered in the samples with 0.2 and 0.6 pct oxygen, while the near random distribution of the boundary misorientations was obtained in the specimens with 1.5 pct oxygen. The effect of dispersed particles on the structure evolution and the relationship between microstructures and some mechanical properties are discussed.
Study of the Nanometric Grain Size Distribution in Iron Compacts Obtained by Mechanical Milling
Materials Science Forum, 2006
A study has been carried out on the grain size distribution of cylindrical compacts obtained by consolidation of iron powder severely deformed by mechanical milling. Consolidation has been performed in two consecutive steps: cold and hot conditions. The hot one was done at two temperatures, namely 425 and 475°C. After milling, the iron powder has a grain size of 8 nm (± 4 nm) with an average hardness of 800 HV. After hot compaction the grain size increases up to 50 nm, especially at 475°C where a small fraction of grains reach larger values than the average. The grain size was evaluated by two different techniques, X-Ray Diffraction and Transmission Electron Microscopy. Results showed some differences between both methods. The advantage of using TEM is that grain size distribution, and not only the average size, can be obtained. Small discs were also obtained from the compacted specimen in order to fracture them on a “ball on three balls” equipment. The fracture behaviour of the sam...
Characterization and Reduction Behavior of Mill Scale
ISIJ International, 2011
This paper presents an initial part of a project devoted to the recycling of mill scale in the form of selfreducing briquettes. First chemical and morphological characteristics of mill scale were investigated and next its gaseous reduction behavior was studied by thermogravimetry. The chemical characterization showed that wustite is the major constituent of this waste matter, with small amounts of magnetite, hematite and metallic iron. The microscopic examination of the scale revealed its complex and layered microstructure with three distinct zones. The outer layer is relatively thin and porous. It is mainly composed of hematite and magnetite. The intermediate layer is made of the dense, columnar grains of wustite. The inner layer is a very porous wustite. The gaseous reduction by carbon monoxide has a topochemical character regardless of initial morphology of scale and, depending on temperature and reducing gas composition it produces a porous iron or the iron whiskers. The unreacted shrinking core model with one interface fits quite well the kinetic data and the activation energy of reduction is about 80 kJ/mol.
Effect of Iron Ore Pellet Size on its Properties and Microstructure
The properties of the pellets and their microstructure mainly depend on the raw material mix proportion, raw material chemical composition and the physicochemical conditions like the temperature and oxygen partial pressure within the induration machine. The pelletising plant products are in the size range of 8 to 16 mm. With increasing pellet size, the sintering intensity, thermo-chemical conditions and formation of different phases vary across its cross section. The time required for varies reactions within the pellet is directly proportional to the pellet size. Because of differences in pellet size, the reduction and oxidation process takes place under different conditions resulting in different phases and microstructures. In this work, detailed studies were carried out on pellets of different size (8 to 16 mm) produced from a 4.2 Mtpa pellet plant for their physical, metallurgical and microstructural properties. It was observed that the pellets in the size range of +8 to -12 mm s...