Vol 46, No 9 (2016)

In the production of copper from sulfide ore, slag accumulates at the processing plant. In the present work, the phase transformations that occur in such slag during its reduction by the gasification products of carbon at 1100 and 1200°C are investigated. Experiments show that most of the iron present in such slag may be converted to metallic form by the gasification products of carbon in cupola furnaces at 1100°C. Subsequent increase in temperature to 1200°C improves the extraction of iron. In the indirect reduction of slag at temperatures above its melting point, metallic iron is mainly concentrated at the outer surface of the product, forming large inclusions that are easily extracted by magnetic separation. An expedient approach is to reduce laminar batch consisting of slag layers no thicker than 5 mm and interlayers of ground coal.

The influence of the temperature, strain, and strain rate on the deformability of low-alloy carbon steel is studied experimentally. Samples are tested on the STD 812 torsional plastometer at Czestochowa Technological University. The hardening of low-alloy carbon steel at different strain rates and temperatures is plotted on the basis of the results for its resistance to deformation. For all the curves, the rate of hardening is high in the initial section, with no relaxation processes. The influence of the strain rate and temperature on the maximum resistance to deformation is quantitatively determined; this is important for practical purposes. The resistance to deformation declines on account of relaxation. The influence of the strain rate and temperature on the mean hardening rate in the range 0 < ε_u < ε_u*is also studied.

A model is proposed for the formation of metallic phase when gaseous reducing agent is bubbled through multicomponent oxide melt. The model includes the following stages: the formation of bubbles when gas is injected in the melt; the reduction of metal at the surface of the bubbles and its concentration in droplet form at the rear of the bubble; motion of the bubble–droplet system in a direction determined by the ratio of the uplift forces on the bubble and the gravitational forces on the droplet; entrainment of the droplets to the surface; and coalescence of the droplets and their descent on reaching a size such that the gravitational forces exceed the sum of the hydrostatic collision forces and the surface tension forces. Equations are presented for estimating the size of the gas bubble and the droplet moving in oxide melt without decrease in size; the direction of motion of the bubble–droplet system; its rate of ascent or descent; and the conditions in which the bubble–droplet system breaks down. The factors responsible for separation of the bubble and the droplet are identified: the surface properties of the oxide melt and the metallic melts and their interphase characteristics. By adjusting these parameters, the formation of metallic phase at the bottom of the vessel may be regulated.

The treatment of Fe–Cr and Fe–Cr–Ni alloys by means of oxygen-bearing plasma is investigated in the laboratory, using a plasma furnace with a tungsten cathode and a water-cooled copper anode. That permits modeling of the processes in the contact spot of the plasma arc and the melt surface. The mathematical model developed describes the melt–plasma interaction. The kinetic parameters of the decarburization of high-chromium melt by argon–oxygen plasma are determined from experimental data. The results show that considerable decarburization of high-chromium melt is possible, with little loss of chromium, by treatment with plasma containing no more than 15–17% oxygen. Comparison shows that the model data and experimental results are in good agreement.

Traditionally, iron and steel production is based on a two-stage system consisting of a blast furnace and a converter, which is characterized not only by high productivity but also by copious generation of gaseous emissions and solid wastes. Reductive smelting in a blast furnace with unavoidable carburization of the metal—the formation of molten iron—calls for the organization of oxidative conversion of iron to steel. The direct reduction of iron and the accompanying metals in the batch by solid carbon, with dosing and regulation of the carbon inputs, permits the organization of reductive smelting without excessive carbon concentrations in the metal. That eliminates the need for oxidative smelting of the steel. Reductive smelting of coal-bearing batch has been undertaken and, for the first time anywhere, alloy-steel samples have been produced directly from batch, without the intermediate production of hot metal.

The basic factors that affect the ladle treatment of steel are analyzed. Balance equations, chemicalkinetic equations, thermodynamic equations, and hydrodynamic and gas-dynamic equations are written for the treatment of steel in a ladle–furnace unit with a vacuum-degassing system. A cylindrically symmetric calculation grid is developed. The equations are adapted on the basis of the finite-element method.

By statistical analysis, a formula describing the tabular relationship between the Brinell (HB) and Rockwell hardness (HRC) of carbon steel is derived. Likewise, a formula relating HRC to the alloy strength σ_u is found. The dependence of the coercive force H_c of carbon steel on σ_u is established on the basis of measurements of HRC and H_c and σ_u values calculated from the proposed formula. Results of assessing σ_u on the basis of H_c are presented for 30, 35, 45, U8, U10, and U12 steel.