Cold Briquetting of DRI Fines for Use in Steel Making Process

DRI fines, generated during its manufacture and handling, generate high content of fines in the size fraction less than 2 mm. It has iron content above 80%. It is difficult to directly use such iron-rich material in the primary steel making process, without agglomeration. At JSW Steel Vijayanagar, around 50 to 70 tons per day of DRI fines with < 2 mm size fraction get generated. The fines are used in base sinter mix or it may be agglomerated suitably to use it as a coolant in the primary steel making process. Since the fines are extremely reactive, they are susceptible to oxidation if it is not agglomerated as soon as it is generated. The present study brings out the development of an agglomeration process for the DRI fines to a dense metallized briquette, for use as a coolant in basic oxygen furnace. Initially, the conditions for briquetting such as use of binder, hardener, lime, dust, moisture, briquetting and curing conditions were established in a 10 kg batch size. This was followed by industrial-scale processing, at 500 kg batch size. The physical and chemical characteristics of the fines and briquettes were assessed at different stages. The cold compressive strength of the cured briquette was found to be a function of moisture content. The handling parameters in the production condition, for long-term pile-up of briquettes against oxidation, were brought out. The successful use of the briquettes in basic oxygen process was demonstrated.     

冷压成型用煤的粘结性

分析了成型用煤粘结性对冷压成型和型煤炭化工艺的作用,讨论了主体煤粘结性和配粘结用煤对型煤和型焦的强度及热性质的影响。主要结论是：(1)型煤强度主要取决于所用粘结剂的质和量,与煤本身的粘结性无关,型焦的强度和热性质主要受成型用煤的粘结性和所用粘结剂的相互作用的影响;(2)有弱粘结性的低挥发分主体煤特别是贫瘦煤是制备强度高,热性质好的冶金型焦和铸造型焦的优质原料。     

不锈钢除尘灰冷固结团块抗压强度的影响因素

采用冷固结成型法对不锈钢除尘灰进行造块,在微机控制电子式万能试验机上进行抗压强度测试。通过单因子实验,研究闷料时间、持压时间和球团失水各因素对团块强度的影响规律。并设计正交实验研究了石墨粉、水分、蔗糖和团压压力4个因素对球团强度影响的主次性。结果表明,闷料步骤对不锈钢除尘灰冷固结成型至关重要,球团失水对提高球团强度作用显著,持压时间对球团强度也有一定程度的影响;石墨粉等对团块抗压强度影响大小顺序为:水分蔗糖石墨粉团压压力。并且得到最优配比(质量分数):配加水分为13%、蔗糖为13%、石墨粉为11%,团压压力为30 MPa,此时球团可获得27 MPa以上的抗压强度。     

Effect of Lead Addition and Milling on Densification and Mechanical Properties of 6061 Aluminium Alloys

In the present work, one batch of prealloyed 6061Al powder was mixed with different lead compositions (5, 10, 15 vol.%) and another set with same composition was ball-milled for 5 h at 300 rpm. Microstructural features such as lattice constant, crystallite size, particle size and morphology were studied using XRD, particle size analyzer and SEM. Both the as-mixed as well as ball-milled powders were compacted at 300 MPa and sintered under N₂ atmosphere for 1 h in tube furnace at 590 °C. The ball milling of 6061Al alloy powder improved sinter density and densification while lead addition showed negligible influence on these parameters. The microstructure of as-mixed 6061Al–Pb alloys exhibited equiaxial morphology whereas ball-milling resulted in elongated grains with uniform lead distribution. Quasi-static compressive mechanical behavior was investigated for 6061Al–Pb alloys at 1 × 10^?3 s^?1 strain rate. Results indicated that ultimate compressive and yield strength were sensitive to milling and lead volume fraction.     

Characterisation of coal–charcoal composite biocoke as a sustainable alternative for ironmaking

The partial substitution of coal by wood charcoal or other types of biomass for the production of metallurgical coke is catching the attention of the steelmaking industry worldwide because it generates less CO₂ in the industrial processes. The objective of this paper is to correlate the effect of the proportion of coal and wood charcoal on the mechanical strength and CO₂ reactivity in briquettes of mixtures of coal and wood charcoal. The briquettes were manufactured from mixtures of coal and 5, 10, 15, 20, 30, 40 or 50 wt-% of wood charcoal. Both materials were grounded and sieved until the particle size was less than 0.044?mm. The mixture was then pressed in a cylindrical die and heat-treated under a nitrogen flow from ambient temperature until 1373?K for 8 hours. Compressive strength and CO₂ reactivity tests were conducted on the samples. Optimal results of the compressive strength were obtained for additions of wood charcoal between 10 and 15 wt-%. For mixtures with wood charcoal contents above 5 wt-%, the CO₂ reactivity tests showed an increase in the reactivity compared to the briquettes of coal without the addition of wood charcoal.     

Preparation of Iron Ore Micro-pellets and Their Effect on Sinter Bed Permeability

At present around 6–7% of iron ore slimes, out of total production, are being generated and accumulated at iron ore mine sites of National Mineral Development Corporation Limited, India. The accumulated slimes of finer size and relatively inferior grade should be utilized in an economical way for sustainable mining. These slimes can be agglomerated into micro-pellets for subsequent use in sinter making through hybrid pellet sintering method. However, the micro-pellets of sufficient size and strength are required for hybrid sinter making. The green properties of the micro-pellets depend upon various parameters such as surface area, moisture, binder, etc. In this study, iron ore slimes were beneficiated through gravity, and magnetic separation and concentrate of grade 65% Fe (Total) was obtained. Since the concentrate obtained had low surface area (700–900 cm²/grams) rendering it unsuitable for micro-pellet making, it was further subjected to grinding in a ball mill. The requirement of surface area for producing an optimum quality of green micro-pellets was established. The resultant micro-pellets were further used in studying sinter bed properties. The effect of moisture and size of micro-pellets on permeability of sinter bed were examined. The results confirmed that the addition of micro-pellets to the sinter mix improved the permeability of the sinter bed. The sinter bed with highest permeability of JPU 25.25 and void fraction of 36.27% was achieved with micro-pellets of size 3–6 mm at 7% moisture level. Mean granule size of sinter mix was also studied with respect to moisture content and size of the micro-pellets.     

Understanding the Agglomeration Behavior of Selected Copper Ores Using Statistical Design of Experiments

The drum agglomeration of two different crushed copper ores (I and II) has been optimized using Taguchi's L₁₆ (4⁵) orthogonal array design to determine the optimum conditions for maximizing the average agglomerate size and minimizing the amount of fines. The effects of controllable operating factors including moisture content (ore I: 9.6–11.1%; ore II: 12.8–14%), retention time (2–4 min), drum speed (15–45% critical), drum load (ore I: 13–32%; ore II: 6–24%) and acid concentration (6.5–90 g/L) on the performance of the agglomeration process were studied. For ore I, the maximum average agglomerate size and minimum percent fines (?1 mm) occurred under the conditions: drum load (22.75%), moisture (10.35%), time (4 min), drum speed (30% critical), and acid concentration (41 g/L), whereas for ore II, the same conditions occurred under the drum load (18%), moisture (13%), time (3 min), drum speed (30% critical), and acid concentration (30 g/L). Under the conditions studied for ore I, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be drum load. For ore I, time and acid concentration had a measurable effect on maximizing average agglomerate size, whereas moisture had a statistically significant effect on minimizing the amount of fines. For ore II, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be acid concentration. Time had a measurable effect on maximizing average agglomerate size, whereas the other variables did not affect the responses significantly for ore II.     

Research on the Solubility of Radioactive Elements in the Ashes from the Soma in Turkey

Coal combustion results in wastes such as fly ash, slag, and flue gases. In Turkey, approximately 45 million tons of coals are fired annually and consequently around 20 million tons of fly ashes are produced. Such large volumes of ash pose a significant problem both for society and the environment. Furthermore, significant amounts of uranium and thorium are often encountered in these ashes. These concentrations are relatively higher for ashes from younger age lignites. Within the scope of this study, a series of characterization tests were performed on samples taken from Soma thermal power plant, one of the largest in Turkey. Characterization studies include particle size analysis, moisture analysis, density determination, pH profile measurements, chemical analyses, and mineralogical analyses. Leach tests with sulfuric acid (H₂SO₄) were then performed. The leaching of the radioactive minerals (uranium and thorium) with the help of sulfuric acid in the ashes was examined and the optimum leaching parameters were investigated. The recovery opportunities of uranium and thorium metals in the ashes were addressed. The results indicated that under optimum conditions, 94.71% uranium dissolution efficiency and 93.21% thorium dissolution efficiency were obtained.     

Influence of raw material particle size on quality of pellets

Abstract

Pellet plant (4·2 MPta capacity) of JSW Steel Ltd imports iron ore fines from different mines to produce pellets for its Corex and Blast Furnace plants. The pelletisation process involves drying the ore fines to reduce the moisture content to less than 1%, grinding in open circuit ball mills to get required fineness. To produce good quality of pellets certain additives are important and limestone is employed for modifying the pellet basicity. Iron ore fines of ?10 mm size and limestone are ground together in a ball mill to get sufficient fineness for the balling process. However, as limestone is harder than iron ore fines the + 100 mesh size limestone particles is higher than required and not all the limestone is fully consumed in the reaction for melt formation. Microstructural studies were conducted under a Leica DMRX polarized microscope at different level fineness (?325# ? 56, 58 and 60%) to investigate its effect on the pellet quality. The cold crushing strength of the pellet improved from 203 to 220 kg p^?1 with increase in fineness. With increase in percentage of ?325# particle size in the ground product RDI of the pellet decreased from 13·8 to 11·9% with increased melt formation from 5 to 9%. With increase in fineness ?325# from 56 to 60% the 150 to 500 μm size pores decreased from 51·8 to 13·6%.     

生物质合成气直接还原铁矿-生物质复合球团炼铁

为了使炼铁工业摆脱对化石能源的依赖及满足越来越严格的环境要求,将生物质能的开发利用与直接还原技术进行集成提出一种新型的绿色炼铁方法.把生物质、铁矿石粉与添加剂混合制取生球团,利用生物质催化气化制备的富氢合成气作为还原剂,生物质的高温燃烧为生球团的预热和预热球团的直接还原提供外加热源.对影响生物质直接还原炼铁的因素,如预热、还原温度及球团粒径进行了研究,发现减小球团粒径、增加预热和还原温度能够提高直接还原铁产品的全铁质量分数及金属化率.当采用品位65.21%的铁精矿为原料,在最优操作条件下(生球团粒径介于8~10 mm之间,900℃预热30 min,1000℃下还原60 min)可制得全铁TFe质量分数为86.1%,金属化率为94.9%的高质量直接还原铁产品.      

Microstructure Evolution and Mechanical Behavior of Cold-Sprayed,Bulk Nanostructured Titanium

To provide insight into the microstructural evolution and mechanical behavior of bulk nanostructured Ti, we used cold gas dynamic spraying of Ti particles to synthesize thick coatings (e.g., >10 mm in thickness). Accordingly, the grain size, lattice parameter, lattice strain, residual stress, porosity, microhardness, tensile, and compressive behavior of the bulk Ti deposits before and after annealing were comparatively analyzed. Our results show that the microstructure of the as-sprayed bulk Ti was characterized by a grain size of ~60 nm, lattice expansion (~2 pct for \( a \) and ~3 pct for \( c \) ), lattice strain (~1.65 × 10^?5), and residual compressive stress (~53 MPa). Moreover, annealing of the as-deposited bulk Ti led to a significant decrease in lattice expansion, lattice strain, and residual stress, whereas porosity remained unchanged (~11 pct). The mechanisms of grain growth, as well as the evolution of particle interfaces during annealing, were also investigated. In terms of mechanical behavior, the as-deposited bulk Ti exhibited a very low modulus (52 GPa) with relatively high tensile and compressive strength values (180 and 850 MPa, respectively). Annealing in the temperature range of 1023 K to 1173 K (750 °C to 900 °C) led to a significant increase of tensile and compressive strength (to 380 MPa and more than 1200 MPa, respectively). Finally, annealing resulted in a slight increase of elastic modulus, which was rationalized on the basis of changes in pore geometry in the bulk Ti deposits.     

Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint

Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min^?1 and 500 rpm 100 mm min^?1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al₁₃Fe₄ and small size Fe₃Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min^?1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min^?1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al₁₃Fe₄ at 1000 rpm and travel speed 50 mm min^?1 in amounts higher than 500 rpm and a travel speed of 100 mm min^?1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.     

The development of technology for making SvAK12 welding wire from shaving billet

A technology for making a welding wire with a diameter of 1.2 and 2.0 mm from the shavings of SvAK12 aluminum alloy is developed. This technology includes hot briquetting the graded shaving scrap at 400–420°C, the hot extrusion of briquettes at 460–470°C with elongation factors of 32 and 56, cold wire drawing the extruded bars with average unit reductions for a pass of 15–20%, and intermediate annealings at 400°C. It is shown that this wire is suitable for soldering parts of aluminum alloys, and the level of the mechanical properties allows it to be recommended for wide application.     

Effects of Binder on the Properties of Iron Ore-Coal Composite Pellets

Large amounts of fines and superfines are generated in Indian iron ore and coal mines due to mechanized mining and mineral dressing operations. Utilization of these fines for extracting metal is of vital concern for resource utilization and pollution control. For agglomeration of these fines, a suitable binder is required. Iron ore-coal composite pellets were prepared by cold bonding. Various binders such as lime, Ca(OH)₂, slaked lime, dextrose, molasses, and sodium polyacrylate (SPA), alone or in combination, were employed for making composite briquettes. The slaked lime–dextrose combination produced the highest strength among the various binders employed for producing composite briquettes and was therefore selected for producing composite pellets for the smelting reduction. In cold bonding, the composite pellets attain the requisite properties due to physico-chemical changes of the binder in ambient conditions. It was possible to obtain a dry strength of more than 300 N per pellet in some cases and more than 200 N per pellet in many trials. Drop strength and shatter index values of composite pellets were also measured. In the present paper an attempt has been made to evaluate the mechanical properties of cold-bonded composite pellets so as to throw some light on the capacity of these pellets to withstand stresses during handling and transportation.     

THE MECHANICAL PROPERTIES OF HOT-RECOMPACTED IRON-NICKEL SINTERED ALLOYS

Abstract

Powder-metallurgy components which are to withstand high dynamic stress are frequently required to possess both high strength and great toughness. This combination of properties can best be achieved by increasing the density of the sintered component and one method of doing so is bot pressing.

This paper deals with the mechanical properties of sintered iron–nickel alloys produced by hot compacting in six stages, as follows:

(1) Preparation of the powder mix.

(2) Production of compacts under a pressure of 8 Mp/cm²

(3) Heating the compacts to 1000°C (1275 K).

(4) Re-pressing the hot compacts in a die heated to 300°C (575 K).

(5) Cooling in air.

(6) Sintering at optimum temperature and time under optimum furnace conditions.

The investigation covered the dependence of tensile strength, elongation at fracture, and Brinell hardness of alloys with Ni contents of 1–10% on the sintering temperature and time, on the furnace conditions, and on raw-material variables.

It was found that Fe–Ni powder-metallurgy parts with a maximum tensile strength of ～60 kp/cm² could be produced. The Brinell hardness reached 190 kp/mm² with 10% Ni content. Elongation at fracture was in the region of 45% with 1% Ni and remained comparatively satisfactory even with high Ni contents if very pure raw materials were used. Powder-metallurgy materials with a tensile strength of 60 kp/cm² and an elongation at fracture of 17% can be obtained by the process.     

Improving the Elevated-Temperature Properties by Two-Step Heat Treatments in Al-Mn-Mg 3004 Alloys

In the present work, two-step heat treatments with preheating at different temperatures (175 °C, 250 °C, and 330 °C) as the first step followed by the peak precipitation treatment (375 °C/48 h) as the second step were performed in Al-Mn-Mg 3004 alloys to study their effects on the formation of dispersoids and the evolution of the elevated-temperature strength and creep resistance. During the two-step heat treatments, the microhardness is gradually increased with increasing time to a plateau after 24 hours when first treated at 250 °C and 330 °C, while there is a minor decrease with time when first treated at 175 °C. Results show that both the yield strength (YS) and creep resistance at 300 °C reach the peak values after the two-step treatment of 250 °C/24 h + 375 °C/48 h. The formation of dispersoids is greatly related to the type and size of pre-existing Mg₂Si precipitated during the preheating treatments. It was found that coarse rodlike β^′-Mg₂Si strongly promotes the nucleation of dispersoids, while fine needle like β^″-Mg₂Si has less influence. Under optimized two-step heat treatment and modified alloying elements, the YS at 300 °C can reach as high as 97 MPa with the minimum creep rate of 2.2 × 10^?9 s^?1 at 300 °C in Al-Mn-Mg 3004 alloys, enabling them as one of the most promising candidates in lightweight aluminum alloys for elevated-temperature applications.     

Biomass Residue Briquetting and Characterization

All kinds of biomasses pull carbon out of the air as they grow. Waste biomass can be made into usable fuel by densification. These biomasses can then replace some coal in power plants, which will reduce carbon emissions and greenhouse gas effects. Densification of low-density biomass (agricultural and agro-industrial waste) is called biomass briquetting. The briquette form facilitates easy transportation, enables better handling and storage, and is efficient to use as an alternative fuel to coal and firewood. The high temperature developed during the high-pressure densification process assists the inherent lignin, which is the binder in the biomass, to bind the biomass and form a densified fuel called briquettes. In this paper, four kinds of biomasses (mango leaves, eucalyptus leaves, wheat straw, and sawdust) were briquetted. Physicochemical and thermochemical characterization of the biomass residues was carried out by using standard methods. A hydraulic press and an automatic compression testing machine were used for the briquetting and testing. The effect of various parameters, such as compression pressure, pressure application rate, holding time, particle size, and moisture content, on the density of the briquettes was studied. The impact resistance test was carried out by using the standard ASTM method. All the briquettes prepared from the biomass studied in this paper have more heating value than half of Indian coal; thus, they can be used as an alternative to coal and firewood.     

Mechanical and Thermal Properties of Pulsed Electric Current Sintered (PECS) Cu-Diamond Compacts

In this work, dispersion strengthening of copper by diamonds is explored. In particular, the influence of 50- and 250-nm diamonds at contents of 3 and 6 vol. pct on the mechanical and thermal properties of pulsed electric current sintered (PECS) Cu composites is studied. The composite powders were prepared by mechanical alloying in argon atmosphere using a high-energy vibratory ball mill. The PECS compacts prepared had high density (>97 pct of T.D.) with quite evenly distributed diamonds. The effectiveness of dispersoids in increasing the microhardness was more pronounced at a smaller particle size and larger volume fraction, explained by Hall–Petch and Orowan strengthening models. The microhardness of Cu with 6 and 3 vol. pct nanodiamonds and pure sm-Cu (submicron-sized Cu) was 1.77, 1.46, and 1.02 GPa, respectively. In annealing experiments at 623 K to 873 K (350 °C to 600 °C), the composites with 6 vol. pct dispersoids retained their hardness better than those with less dispersoids or sm-Cu. The coefficient of thermal expansion was lowered when diamonds were added, being the lowest at about 14 × 10^?6 K^?1 between 473 K and 573 K (200 °C and 300 °C). Good bonding between the copper and diamond was qualitatively demonstrated by nanoindentation. In conclusion, high-quality Cu-diamond composites can be produced by PECS with improved strength and better thermal stability than for sm-Cu.     

Physical simulation of converter steelmaking with powder injection

A water model of top and bottom blown converter with top lance powder injection and bottom tuyere powder injection was established to investigate the powder injection. The results show that the powder penetration ratio under the condition of top lance injection is greater than that under the condition of bottom tuyere powder injection. In both cases, the powder penetration ratio increases with the increase of solid/gas ratio and powder particle size. Powder uniform dispersion time with top lance powder injection is longer than that with bottom tuyere powder injection. Top lance powder injection, lance height of 258?mm, bottom blowing rate of 1·96?Nm³?h^?1 and powder particle size of 0·212–0·380?mm are suggested as the optimum powder injection operation under the experimental condition. The corresponding optimum operation for prototype is top lance powder injection with lance height of 1550?mm, powder size of 1–5?mm and bottom blowing rate of 450?Nm³?h^?1.     

Hard Alloy WC–24% Ni Obtained in the Solid Phase from Ultrafine WC,NiO, and C Powders. Part 2. Mechanical Properties

Mechanical properties of WC–24 mass% Ni alloy prepared by a combination in single stage of metal phase synthesis and compaction of an ultrafine mixture of WC–Ni powders by high-energy compaction and sintering are studied. Tungsten carbide, nickel oxide, and carbon are selected as the starting powders. After milling the initial powders the average particle size is 200-300 nm. Previously compacted briquettes of WC + NiO + C are heated, sintered, and pressed in the range 950-1300°C at vacuum of 0.133 Pa. Briquettes are also sintered in the liquid phase at 1350°C for comparison. Ultimate strength in bending, fracture toughness, ultimate strength in compression, and Vickers hardness are determined for specimens prepared at different temperatures. The dependence of mechanical properties on specimen consolidation temperature is studied. It is shown that these dependences for pressed specimens have a maximum at 1200-1250°C. The high level of properties (ultimate strength in bending 2500 MPa, ultimate strength in compression 3100 MPa, fracture toughness 19 MPa·m^1/2, and hardness 10.0 GPa) are achieved for a WC + Ni + C powder mixture to which carbon is added in the form of a liquid carbon-containing compound. Introduction into the mixture of commercial carbon grade P803 leads to low specimen mechanical properties. The effect on mechanical properties of porosity and pore size, and also grain boundary quality between particles is studied.