Density and electrical conductivity of synthetic slags added to the ladle–furnace unit

The properties of a series of synthetic slag melts for steel refining in the ladle–furnace unit are determined in the range 1430–1645°C: the slag density ρ on the basis of the maximum pressure in a gas (argon) bubble; and the electrical conductivity æ by the double-contact ac volt–ampere method (at 2 and 5 kHz). On the basis of the measurements, the following characteristics are calculated: the bulk expansion coefficient β and actual molar volume V _M (both referred to 1600°C), the relative excess molar volume δV _M , the activation energy E _æ of the electrical conductivity, and the preexponential factor æ in the Arrhenius equation that approximates the influence of the temperature on æ. The dependence of these variables on the degree of replacement N of the polymer-forming oxides Al₂O₃ and SiO₂ in the slag batch by sodium monoxide is analyzed. With increase in N, it is found that ρ, δV _M , E _æ, and æ₀ decline monotonically, while æ increases. The dependence of β on N is more complex. The behavior of β and δV _M is discussed in terms of the polymer theory of slags.     

Reconstruction of gas-purification system and ladle–furnace unit at PAO Severstal’

The gas-purification system for shaft electrofurnace 1 and ladle–furnace unit 1 at PAO Severstal’ have been reconstructed by specialists from Energostal’ Ukrainian Scientific and Technological Center. For the first time in the world, large electrofilters have been replaced by bag filters with pulsed regeneration (total filtration area 33000 m²). The influence of dust deposits from the furnace in various smelting periods on the dust concentration in the atmosphere of the working zone has been studied. The waste gases and unorganized emissions are completely removed from the furnace, with guaranteed atmospheric levels in the working zone that do not exceed the background concentrations by more than the maximum permissible concentration (1 kg/m³) and residual dust concentration of 3–5 mg/m³ at the smokestack.     

Laws of nitriding of alloy steel in a plasma–arc remelting furnace

Metal drop samples are taken during plasma–arc remelting of 12Kh25N16G7AR steel billets. An analysis of the drops shows that the fraction of steel nitriding in the drops accounts for 20–40% of the total steel nitriding at a nitrogen content of 0.06% in a billet. An equation is derived to estimate the nitriding of a liquid Cr–Ni–Mn steel from the nitrogen concentration in the billet to be remelted.     

Influence of the pressure in the vacuum unit’s working chamber on the content of hydrogen and nonmetallic inclusions in steel

In electrosmelting shop 2 at Belarussian Metallurgical Plant, the removal of hydrogen from steel is studied as a function of the residual pressure in the working chamber of the RH vacuum unit. The influence of the pressure on the quantity and composition of the nonmetallic inclusions in cord steel is also investigated.     

Simulation of tuyere–raceway system in blast furnace

Abstract

A uniform distribution of the blast is an important prerequisite of a balanced blast furnace operation, because the blast is the main source of the hot gases that are needed to preheat, reduce and melt iron ores. The supply of hot gas from the raceways is not necessarily uniform along the furnace periphery, but depends on flow resistances encountered on the individual bustle main tuyere–raceway–raceway boundary routes. A model for this system has been developed in order to study and analyse the effects of changes in tuyere parameters and boundary conditions. Variables such as the total blast volume, blast pressure, tuyere diameter and the combustion degree of injected reductants in the tuyeres can be studied. An online version of the model has also been developed to track how the conditions on the tuyere level change with time in operating blast furnaces.     

Impact of slag–refractory lining reactions on the formation of inclusions in steel

Abstract

The present study was carried out to investigate the impact of slag– refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.     

Effect of limestone injection into furnace and desulfurization on boiler’s operation characteristics

In combination with the related documents and actual experience in the project operation,this paper analyzes the effect of limestone injection into furnace and desulfurization (LIFDS) on furnace slagging tendency,dust deposit speed of the heating surface,wearing,corrosion,boiler’s combustion conditions and combustion efficiency,secondary pollution,etc.Based on this situation,some countermeasures and suggestions were advanced so as to strengthen the boiler’s soot-blowing management,the operation of ash removal,supervision,and analysis of boiler operation parameters,planned inspection during the maintenance downtime,tracking management of coal quality and optimization of the operation and management.All these have a directive meaning to boilers’ safety operation.     

Wear resistance and structure–phase states in the surface of the welding-deposited coating on steel

The elemental and phase composition, the state of a defect substructure, and the tribological characteristics of the layer deposited on the surface of a low-carbon low-alloy steel by a welding method are studied. The deposited layer on the steel surface causes the formation of a multilayer structure, and the wear resistance of the deposited layer is found to increase.     

Transfer of iron to Cu–Ni alloys from the lining of the vacuum induction furnace

In Ni–Cu alloys, iron must be excluded in many cases. Iron may enter the alloy from the batch or the furnace lining. Since the Fe₂O₃ content in refractories may be as much as 2.5%, it is important to assess the increase in iron content in alloys on account of interaction with the furnace lining. In the present work, the influence of the Fe₂O₃ content in the crucible and the volume of the crucible on the iron content in the final alloy is studied. Thermodynamic analysis and experimental data indicate that the nickel and copper in Ni–Cu alloys may reduce iron that is present in the lining. When using low-iron batch, iron from the crucible is transferred almost completely to the melt. The increase in iron content in Ni–Cu alloys is investigated as a function of the capacity of the vacuum induction furnace and the Fe₂O₃ content in the periclase crucibles, with complete transfer of the iron from the lining to the melt. With increase in furnace capacity, less iron enters the melt from the crucible. With more than 200 kg of metal, the increase in iron concentration mainly depends not on the furnace capacity but on the Fe₂O₃ content in the refractory. In order to produce Ni–Cu alloys with <0.01% Fe, refractories with Fe₂O₃ content no higher than 0.5% must be used. To produce Ni?Cu alloys with <0.05% Fe, the use of lining refractories with Fe₂O₃ content no higher than 2.5% is recommended.     

Influence of bed conditions on gas flow in the COREX shaft furnace by DEM–CFD modelling

The gas flow plays an indispensable part in the production process of direct reduction iron in the COREX shaft furnace. So as to assess the gas flow under different bed conditions which are including shapes of the bed, different particle diameters and particle motion speed, a three-dimensional model has been built. The behaviour of gas flow was investigated by a hybrid model of DEM–CFD coupling. The results show that the bed void differences which is caused by the packing way and particle diameter has an important influence on the gas flow and the shaped bed of ‘V’ is the better choice to provide the optimal gas flow in the packed bed. When the descend velocity is 1 or 2?m?h^?1, it has little impact on the gas flow in the packed bed, and we can think that the bed is static.     

Sustainability–steel and the environment

Abstract

A two-dimensional heat and fluid flow model was used to simulate the plasma arc furnace, where the flow is governed by the steady state incompressible Navier–Stokes equations. The flow has been taken as turbulent and the standard k-epsilon model was used to simulate the turbulence in the flow. The coupled non-linear differential equations were solved with suitable boundary conditions and temperature dependent plasma properties at atmospheric pressure by employing an efficient finite volume method. The calculations and heat transfer to various parts of the furnace were calculated for argon, nitrogen and hydrogen plasmas. The voltage–current characteristic for the different types of plasma and the effect of other process parameters on heat transfer are discussed.     

Influence of titanium microalloying on the properties of low-alloy Cr–Mo–V steel

The influence of titanium, which readily forms nitrides, on the structure and the long- and short-term mechanical properties of Cr–Mo–V steel is investigated. Increase in the Ti content to 0.075% increases the thermal stability of the steel. With increase in Ti content to 0.13%, the thermal stability of the steel declines sharply, on account of structural changes.     

Increase in the efficiency of electric melting of pellets in an arc furnace with allowance for the energy effect of afterburning of carbon oxide in slag using fuel–oxygen burners

The problems of increasing the efficiency of electric steelmaking using fuel–oxygen burners to supply oxygen for the afterburning of effluent gases in an arc furnace are considered. The application of a new energy-saving regime based on a proposed technology of electric melting is shown to intensify the processes of slag formation, heating, and metal decarburization.