Ironmaking & Steelmaking: Processes,Products and Applications

WorldAutoSteel launched phase 2 of its FutureSteelVehicle programme with the aim to show automakers how latest and future steel grades and technologies can provide light body structures for electrified vehicles. The objective was to develop detailed design concepts and fully optimise a radically different steel body structure for a compact battery electric vehicle in production in the 2015–2020 timeframe. This article discloses the final outcomes of the phase 2 development, detailing steel body structure concepts for the aforementioned vehicles that achieved the aggressive mass target of 190 kg, while meeting 2015–2020 crash performance objectives as well as total life cycle greenhouse gas emissions targets, noise, vibration and harshness, and stiffness. This is achieved using advanced and ultra high strength steels, engineering design optimisation and advanced steel technologies.

The need to automate welding processes in the shipbuilding sector is described, highlighting specific weld configurations and mechanised solutions. Some issues related to steel product supply into this industry sector are described highlighting specifically the material geometry requirements and their effects on automations are also discussed.

Two published papers on a novel solid state steelmaking (S³) process have been reviewed, with particular regard for the technical and economic feasibility of the process. The S³ process involves a two stage twin role casting to solid state decarburisation route and it is claimed to improve product quality and reduce process complexity, by eliminating oxygen blowing in the BOF. The process kinetics of the solid state decarburisation stage has led research to be directed towards a process with an initial starting carbon concentration of 1·2%. This relatively low start carbon level restricts exploitation of the S³ process to scrap intensive routes, such as an EAF, or alternative ironmaking feed, such as HIsarna. Consequently, it is believed that uptake of this process will be limited. Should the mass transfer limitations inherent in the solid state decarburisation be overcome then the possibility to deploy the S³ process to sites fed by the traditional blast furnace would be transformational for the steel industry, reducing capital and operating cost and having a major impact on CO₂ and energy requirements.

European regulations are about to impose a minimum 95% recycling of end of life vehicles with a 10% maximum energy recovery (Directive 2000/53/EC). Current 75% recycling requires the development of innovative processing for treating certain heterogeneous streams. In particular, the recycling of light post-shredder technology particles (fluff) in iron- and steelmaking is an interesting avenue to explore. More specifically, the use of iron oxide rich streams for their iron content [blast furnaces (BFs)] and plastic rich streams as a reducing agent and/or alternative fuel (electric arc furnaces and BFs) is an industrial challenge. This article describes the preliminary multitechnical characterisation results of streams from an industrial site and discusses the potential for recycling according to the nature of the crippling impurities [polyvinyl chloride (PVC) and metals]. The iron oxides contain Cu, Pb and Zn metals, critical as regards pig iron specifications; the high density plastics concentrate PVC (7%Cl) with critical Pb, Sb and Zn. Additional stream processing is essential for such recycling.

In order to optimise the recovery process of Fe and P from industrial steelmaking slag by microwave irradiation, the recovery ratios of Fe and P from slag–graphite mixtures were investigated. In the reduction of industrial slag by graphite at a fixed microwave processing time of 900 s using a microwave oven, the recovery ratio of Fe increased with increasing carbon equivalent (C _eq.: the mole ratio of carbon/oxygen to reduce Fe₂O₃ and FeO, yielding CO gas) and reached 0·87 when C _eq. = 1·56. The recovery ratio of P also increased with C _eq. and showed 0·93 at the same condition. From the comparison between the present and previous studies by Kim and Lee employing a synthetic slag, it was found that almost similar results were obtained. From the chemical analysis of the slag and metal after experiments, it was found that the phosphorus distribution ratio (L _p) strongly depended on the total Fe content in the slag, namely, as the FeO content decreased, the L _p value decreased. Discrepancies observed between the present and previous studies are discussed in view of microwave power and thermodynamic analysis.

Post-consumer steel scrap is often handpicked for contaminants, such as copper, to meet the specifications of steelmakers. If the hand sorting capacity exceeds 20 t scrap/h, the efficiency generally becomes problematic, leaving 50% of the copper contaminants in the steel product. In response, new technologies are emerging that facilitate hand sorting of these types of scrap. The advantages are increased revenues, expanded plant capacity and higher and more consistent steel product quality. A shape sensitive magnetic separator is proposed that presorts scrap into two products. One is a bulky, thin walled steel fraction of high purity, and the other is a volumetrically small flow of relatively heavy parts, including the contaminants. The concentrated contaminant product is amenable for effective sorting by hand pickers or for sensor sorting but could also be sold directly to specialised sorters that extract the copper. Detailed results for the magnetic sorter are reported for midsized incineration bottom ash scrap.

In the first part of the present study, the relation between the dimension free critical capillary number Ca* and the material number Λ are introduced as a stability criteria for slag entrainment at the steel/slag interface. With the knowledge of thermophysical properties of the immiscible liquids in contact, critical values of Ca* for slag entrainment as a function of Λ could be estimated. The interfacial tension was investigated at 1823 K for carbon and Cr–Ni steels in contact with ternary slags containing CaO, SiO₂, Al₂O₃, MgO and TiO₂ using the drop weight method. The apparent interfacial tension of CaO–SiO₂–TiO₂ slag systems in contact with Cr–Ni steel decreases with increasing TiO₂ content and was found to be influenced by interfacial area change during droplet formation at the capillary exit, slag composition and reactions at the steel/slag interface. Minimum values of interfacial tension, observed during measurements, increase the possibility for slag entrainment in the continuous casting mould.

Processing of secondary resources is a relatively new field in metallurgy. In addition to the direct processing of metallurgical dusts, an alternative interest is in the combined processing of various types of resources, including dusts either with high energy contents (carbon and hydrocarbons containing dusts) or with valuable metal contents. The first step in analysing the new metallurgical routes of materials processing is the thermodynamic approach, which gives a quick look at the feasibility and limitations of the defined new processing methods. In the present study, two examples of potential pyrometallurgical treatments for industrial dusts are analysed on the basis of the thermodynamic and thermochemical principles. The aim of this paper is to show the important role of thermodynamic/equilibrium predictions for the design and planning of experiments and the determination of optimal processing conditions.

The present work outlines the statistical analysis of industrial data collected for a few hundred heats from an integrated steel plant. The main purpose was to study the influence of impurities in the ferroalloys FeTi (FeTi70 and FeTi35) and FeP on steel cleanliness. Therefore, two steel grades [ultra low carbon (ULC) high Mn and ULC low Mn] to which these ferroalloys are added were chosen for the study. The number of Al based inclusions analysed with pulse discrimination analysis–optical emission spectroscopy was taken as a measure of steel cleanliness and compared using box plot analysis and through a t test for different grades of FeTi additions. The ferroalloy parameters as well as other major process parameters during secondary metallurgy were also correlated to the inclusion number density. The statistical analysis was supplemented with elemental (ferroalloy) recovery calculations based on the industrial data and FactSage, the equilibrium Fe–Al–P–O diagram and the inclusion extraction analysis. On the basis of this study, it is proposed that (1) FeTi70 is a comparatively cleaner ferroalloy than FeTi35 and (2) for FeP in ULC low carbon steel, the best addition practice to maintain a balance between P recovery and steel cleanliness is towards the end of decarburisation and before the addition of Al blocks.

The feasibility of ‘solid state steelmaking’ (S³ process) to meet the demand of environmental issues and higher production cost was previously studied. The S³ process is the production of high carbon iron sheets from high carbon hot metal using a strip caster and a solid state decarburisation process to produce low carbon steel sheets. In the present study, the possible use of Fe–C melts with relatively low carbon contents of 1·2–1·9 mass-% as an initial hot metal source and the decarburisation behaviours of the produced hypereutectoid iron sheets from these melts were investigated to evaluate practical application. Based on the decarburisation behaviours of the hypereutectoid iron sheets and its mechanical properties, the process using Fe–C melts with 1·2 mass-%C is promising as an environmentally conscious low cost steelmaking process, although further improvements will be necessary.

The effect of cobalt and aluminium on the austenite to pearlite transformation in superbainitic steel was investigated. Experimental work showed that the transformation rate of pearlitic and the volume fraction of pearlite both were increased by adding ∼4 wt-%Co and 1·5 wt-%Al to the parent superbainitic steel. The addition of cobalt and aluminium to superbainitic steels desirably accelerated the growth rate of pearlitic microstructure and undesirably reduced the interlamellar spacing of pearlite, resulting in hardness higher than that of the parent steel in the pearlitic condition. Nevertheless, the accelerated pearlitic reaction, as a softening process of superbainitic steels before machining/forming, may make the commercial use of these steels more viable.

In this work, a numerical study was carried out to characterise the hydrodynamics and heat transport in a five-strand asymmetric billet caster tundish. Employing a three-dimensional computational fluid dynamics model, several numerical experimentations were carried out to capture the exact physics of complex fluid flow and thermal transport in the tundish. Plant practices were simulated by considering seven distinct cases and analysed in detail. Tundish filling operation was tried out with volume of fluid methodology. The effects of thermal buoyancy, its effect on thermofluidic heat transfer and the abrupt change in thermal gradients at different zones in the tundish flow domain were explained after detailed analysis. Refractory heating simulations were performed, and results were analysed in detail. This is the first time that such an exhaustive numerical study on an asymmetric tundish has been reported.