Academic literature on the topic 'Direct reduction (Metallurgy)'

For quite a long time efforts have been made to develop processes for producing iron i.e. steel without employing conventional procedures - from ore, coke, blast furnace, iron, electric arc furnace, converter to steel. The insufficient availability and the high price of the coking coals have forced many countries to research and adopt the non-coke-consuming reduction and metal manufacturing processes (non-coke metallurgy, direct reduction, direct processes). This paper represents a survey of the most relevant processes from this domain by the end of 2000, which display a constant increase in the modern process metallurgy.

A new mineral processing and metallurgy technology was proposed, which was that the ferro-nickel concentrate was prepared from laterite ore by coal-based direct reduction. Under the reduction of cheap reductant and the catalysis of composite additives, the effects of coal-based direct reduction were enhanced and the ferro-nickel was extracted. The optimal conditions were followed that the alkalinity was 0.87, and the roasting temperature was 1150°C, and the roasting time is 2.5 hours. The recovery rate of nickel was 86.7% and the nickel content of ferro-nickel concentrate was 5.3%.

A significant research effort within the CSIRO Light Metal Flagship is aimed at developing new processes for the manufacture of (semi-finished) titanium products based on a powder metallurgy approach. The main driver for considering alternative processing and consolidation techniques to conventional ingot metallurgy is improved techno-economics associated with a reduction in processing steps and increased productivity via rapid consolidation of parts. In this respect, CSIRO has developed a process to manufacture sheet products utilising direct powder rolling; the process consists of cold rolling the powder feedstock to a green strip, which is then rapidly heated and hot rolled to consolidate the material completely. The work reported here was an investigation into the feasibility of fabricating Ti-6Al-4V strip by a blended elemental powder metallurgy route. The development of microstructures occurring during the processing and heat treatment steps has been studied. The generic roles of some process, material and heat treatment variables on the tensile properties and homogeneity of the final material have been assessed and are discussed in this paper.

The article is devoted to the analysis of mutual direct investments in Russia and the EU in steel industry and nonferrous metal industry after the beginning of the global financial crisis. The author notes a great importance of the EU market for Russian companies in their foreign expansion. In particular in steel industry the EU market plays a key role as the North American market does. In nonferrous metal industry the importance of the EU market is reduced due to lack of developed raw material sources within the EU and due to the diversification of foreign activity of Russian companies. The author notes that a reduction of mutual direct investments began after 2008. Russian companies have focused their activities on their own enterprises in Russia because of high debt leverage. The crisis has also resulted in an appearance of new crisis strategies of Russian metallurgical companies for European assets. These crisis strategies include sale of assets, suspension of production and strategic partner search. Traditional strategies of foreign investing were relevant during the crisis. The modernization of production was the most applied strategy. Buying up of core assets was also applied. European investments in Russia were made mainly by creating new production capacity frequently including joint ventures with Russian companies. European investors along with investments introduced new technologies and equipment into Russian metallurgy. The article notes that because of the crisis the number of capital investment projects including European companies was reduced. The author notes that the EU will remain the key area for Russian metallurgical companies if the situation in global metallurgical markets will improve and sanctions against Russia will be lifted off. Acknowledgments. The article has been supported by a grant of the Russian Science Foundation (project № 14-28-00097 “The optimization of Russian foreign investment ties in the context of deteriorating relations with the EU”).

Nowadays a significant number of alternative processes of ferrous metals production have been developed, it differs in the principles of operation, as well as the design arrangement of the aggregates. In general, "alternative" processes of ferrous metals production can be divided into 4 groups. The processes of the first group (the production of sponge iron in direct reduction units with remelting in electric arc furnaces) are based on the use of reduction gases (CO, H2 or a mixture of them) or coal for the reduction. Depending on this, they have different principles of work and design. Shaft processes of direct reduction, based on the use of reduction gases, have the dominant positions in the global production of HBI. This is due to the design simplicity of these units, the reliability of their work and the low content of harmful impurities (S, P) in the products. The principle of the processes of the second group (production of carbon semi-products in smelting reduction units with blowing in BOF) involves the reduction of iron ore with power-generating coal at temperatures of 1400-1600 °C and obtaining hot metal. The processes of this group can use as a charge partially reduced iron ore materials (Corex processes, Finex, Tecnored, etc.), as well as raw iron ore (processes Hismelt, Romelt, Ausiron). More than forty processes in various countries have been developed and tested to substitute blast furnace process. Currently, there are 7 Corex units in the world (2 - China, 4 - India, 1 - South Africa) with a total annual productivity of about 7 million tons; 3 Finex units (2 in Korea, 1 in India) with an annual productivity of about 3.5 million tons. The development of processes for the direct production of steel from iron ore (the third group) is currently focused on the processing of iron-containing waste (sludge, scale, dust iron ore) to crude steel. Examples include: the process of jet-emulsion refining, production of high carbon steel in rotary inclined furnaces or perspective direct electrolysis processes of iron ore (MOE), the development of which is at the initial stages of laboratory research. Continuous processes for the production of crude steel from hot metal (the fourth group), due to difficulties in controlling a continuous process, high consumption of refractories, low economic indexes and, most importantly, the rapid growth of ladle treatment of steel, could not compete with the LD-process and are currently hardly used. It should be said about the prospects of the considered alternative processes for the ferrous metals production. The processes of direct reduction have proven their competitiveness, the prospects of their development is determined by the need of electric steelmaking in high-quality metal charge. At the moment smelting reduction processes of ferrous metals production are not the real competitors to BF process and so far they should be considered only as an addition to it. However, if the price of metallurgical coke continues to grow, then the further spread of smelting reduction processes is possible. The processes of the third group are directed to the utilization of iron-containing metallurgical wastes and dust iron ores, but the development of majority of these processes is on its initial stages, their prospects will be determined by economic efficiency. Continuous steelmaking processes with use of hot metal as a charge could not clearly prove their superiority to the well-known steelmaking processes, at this stage their prospects are rather doubtful.

The low carbon metallurgy technology based on the high-value utilization of biomass is considered as the key development orientation of green ironmaking. In this paper, a pyrolysis coupling technology of biomass tar and iron ore powder is proposed for the reduction of iron ore. Tar is degraded efficiently due to the synergy effects respectively through oxidation of iron oxides and the catalytic action of reduced iron, and simultaneously the reduction of iron oxide to metallic iron. Representative tar components including vanillin, naphthalene, and catechol were selected as tar model compounds. The various reaction conditions on the reduction degree of iron ores was investigated, which include the type of tar component, the pyrolysis temperature, and the ratio of reactants. According to the results, the optimal relationship between tar degradation and reduction of iron ore was identified. It can be found that under the catalytic effects of iron ore fines, the degradation efficiency of the three model compounds followed the following order: naphthalene > vanillin > catechol. Naphthalene owned the better reduction ability. The highest reduction degree of the product reached to 78.5% at 800 °C for 30 min.

Hydrogen has received much attention in the development of direct reduction of iron ores because hydrogen metallurgy is one of the effective methods to reduce CO2 emission in the iron and steel industry. In this study, the kinetic mechanism of reduction of hematite particles was studied in a hydrogen atmosphere. The phases and morphological transformation of hematite during the reduction were characterized using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. It was found that porous magnetite was formed, and the particles were degraded during the reduction. Finally, sintering of the reduced iron and wüstite retarded the reductive progress. The average activation energy was extracted to be 86.1 kJ/mol and 79.1 kJ/mol according to Flynn-Wall-Ozawa (FWO) and Starink methods, respectively. The reaction fraction dependent values of activation energy were suggested to be the result of multi-stage reactions during the reduction process. Furthermore, the variation of activation energy value was smoothed after heat treatment of hematite particles.

Utilization of titanium components made by powder metallurgy methods has had limited acceptance largely due to the high cost of titanium (Ti) powder. There has been renewed interest in lower cost economical powders and several Ti reduction methods that produce a particulate product show promise. This talk summarizes work done at Oak Ridge National Laboratory to consolidate these economical powders into mill products. Press and sinter consolidation, hot isostatic pressing (HIP) and direct roll consolidation to make sheet have been explored. The characteristics of the consolidated products will be described as a function of the consolidation parameters.

AbstractLaser cladding is a well-established technique, with the majority of prior numerical modelling work focused on delivery and melt pool behaviour of powder-based processes. This research presents new investigations into optimised laser beam shaping for the unique characteristics of wire-based processes, where direct substrate heating, as well as heat transfer between the wire and substrate, is important. The value of this subject is the improved deposition rates and dense metallic structures that can be achieved by wire-based deposition processes compared to powder-based material delivery. The within-wire temperature distribution (AISI 316 stainless steel), the heat transfer and direct heating of the substrate (mild steel) are modelled via heat transfer simulations, with three laser beam irradiance distributions. This analysis identified the removal of localised high-temperature regions typically associated to standard Gaussian distributions, and the improved substrate heating that a uniform square beam profile can provide. Experiments using pre-placed wire and a 1.2 kW CO2 laser were analysed using cross-sectional optical microscopy to provide model validation and evidence of improved wire-substrate wetting, while maintaining favourable austenitic metallurgy in the clad material. A key finding of this work is a reduction, from 480 to 190 W/mm2, in the required irradiance for effective melt pool formation when changing from a Gaussian distribution to a uniform square distribution. This also provided a 50% reduction in total energy. The potential improvements to energy efficiency, cost reductions and sustainability improvements are recognised and discussed.