Current state of steelmaking slag processing

In the present work, the properties and composition of steelmaking slag are assessed by analysing existing processing methods, including desulfurisation and dephosphorisation. The atomic absorption and optical emission methods were used to study the chemical composition of slag samples, and metallographic analysis was used to study their microstructure. Major approaches to processing slags applied in Russia and abroad were studied. It was shown that steelmaking slags are neutralised and treated by various methods and subsequently applied in construction and road industries, while the obtained phosphorus-containing products are used in agriculture instead of superphosphate. In addition, these products reduce lime consumption and improve slag formation in steelmaking. The key factor hampering reusing electric steelmaking and converter slags for metal refining is shown to be the presence of phosphorus. The chemical composition of slag samples from the electric steelmaking production was analysed; the iron content amounted to 33.2 wt%, calcium – 19.15 wt%, phosphorus – 0.33 wt% and silicon – 5.39 wt%. Iron is present in the oxidised form (FeO, Fe2O3 and Fe3O4), silicon and calcium in the form of dicalcium silicate (2CaO ∙ SiO2 ), phosphorus in the form of calcium silicophosphate having complex composition – Ca2(SiO4)6(Ca3(PO4)2. Phosphorus is fed to the melting units with gangue minerals, agglomerate, ore and fluxes. When the slags are reused, phosphorus returns to the metal, thus contaminating the final product. Possible methods for extracting phosphorus from steelmaking slags include magnetic and electrostatic separation, gravity and flotation concentration, as well as hydrometallurgical processing.

Carbonized Steel-Smelting Slag Is a Promising Raw Material for the Production of Artificial Concrete

Obtaining an artificial stone based on steel-smelting slag is possible as a result of carbonization of the feedstock in carbon dioxide. The feedstock - slag and carbon dioxide - are by-products from steel smelting in electric furnaces, which must be disposed of in order to improve the environmental situation in the region. The condition for obtaining the cementing ability of steelmaking slag is the preparation of a charge with certain properties and maturation technology: humidity, dispersion of the fine fraction and the maximum size of the coarse fraction, the ratio between the coarse and dispersed fractions, the concentration of carbon dioxide in the gas-air environment, temperature, pressure and flow time. carbonization reactions in the reactor, the magnitude of the pressure during the production of pressed articles, the process of stone maturation in the post-carbonization period.

Development of a Calcium Aluminate Cement from steelmaking slag by altering its mineralogical compositions

Strict environmental norms and raising concern to recycle solid wastes generated during ironmaking and steelmaking processes has been the key driving force in developing various technologies. The present study describes a calcium-aluminate clinker prepared from steel ladle slag by modifying its mineral compositions. The slag paste prepared by mixing with water exhibited flash setting behaviour due to the presence of C12A7 and C3A phases. In contrast, the slag clinker, developed by sintering a mixture of pre-determined quantity of slag and Al2O3 at 1400°C for 2h and 4h, contained CA, CA2, Gehlenite and ‘Q’ phases. Hydration of slag clinker contained stable C3AH6, AH3 and stratlingite with preferential growth of calcium-aluminate hydrate prisms along c-axis that provided a well-defined raceme like morphology with interlinked structure. It improved the setting time and crushing strength of the clinkers after 6h and 24h curing at room temperature. Additionally, presence of ‘Q’ phase with lamellar prismatic crystals also helped in enhancing the strength. The developed clinker also exhibited superior crushing strength as compared to commercially available calcium aluminate cement of medium purity. The slag, used as a source of CaO could replace CaCO3 completely and thus contributed to reduction in CO2 emission during clinker making process.

Mechanical properties of steel slag replaced mineral aggregate for road base/sub-base application based Vietnam and Japan standard

Steelmaking slag is one of the most massive industrial by-products generated during steelmaking processes. This paper presents the current steelmaking slag production status and its potential to use as mineral aggregates in base/sub-base layer of road pavement. The mechanical properties of steelmaking slag were confirmed by the test method specified in Vietnam specification. The volume stability test of the slag was conducted based on JIS A 5015-2018 (Japanese Industrial Standard: Iron and steel slag for road construction). From the results, it was confirmed that steelmaking slag can satisfy all the mechanical requirements specified in Vietnam specification and the requirements regarding stability specified in JIS A 5015-2018. In addition, it was found that the elastic modulus of steelmaking slag applied as a base or sub-base layer in pavement was higher than that of the conventional graded aggregate made from mineral aggregate. Therefore, the thickness of pavement can be reduced by using steelmaking slag, and the construction cost can be lower.

On possibility of using silicomanganese slag and ladle electric steelmaking slag in manufacture of welding fluxes

Analysis of the existing trends in development of technologies for production of welding and surfacing fluxes showed that one of the actively developing areas is the production of fluxes using man-made waste (including metallurgical one) as components of the initial charge. This is due to the fact that the slag waste of metallurgical production contains a large amount of manganese and silicon, which in turn are the basis in welding fluxes. Within the framework of this direction development, the article describes principal possibility and efficiency of using materials based on ladle electric steelmaking slag from JSC “EVRAZ United West Siberian Metallurgical Combine” and slag produced by silicomanganese from LLC “West Siberian Electrometallurgical Plant” in the charge for production of fluxes used in the surfacing of rolling rolls. All the laboratory tests were made using the equipment of the scientific and production center “Welding Processes and Technologies”. For surfacing steel samples, the authors used a flux additive obtained by mixing ladle electric steelmaking slag of a fraction less than 0.2 mm with liquid sodium glass in a ratio of 62 and 38 %. The resulting flux additive was mixed with slag from the production of silicomanganese of a fraction of 0.45 - 2.50 mm in various ratios. Studies of the chemical composition (by the spectral method) and metallographic studies of the deposited layer revealed a tendency to an increase in sulfur content and in contamination with non-metallic inclusions in it with an increase in content of the flux additive in the charge of more than 20 %. According to the results of visual quality control of the deposited layer macrostructure, the absence of defects was established with a flux additive content of up to 30 %.