Vol 60, No 1-2 (2016)

An equation is obtained to describe the energy balance of the process of rolling oil-country tubular products on a reducing mill. Numerical engineering methods are used to solve integral equations for the components of the energy balance, and it is shown that the theoretical description which is obtained can be put to practical use. A method is presented for analytically determining the lead and lag zones in tube reduction, and a relation is derived to describe how the size of the reduction in the tube’s outside diameter for different values of the friction coefficient affects the speed at which it is leaves the stand.

The existing two-stage technology used to make iron and steel is based on the use of hot reducing gases, which results in the formation of waste gases and dust and creates an environmental problem. The results obtained from an analysis of metallurgical processes that involve smelting reduction are used to propose a new technology based on the smelting reduction of a monocharge contains carbon and oxides of metals. The monocharge is composed in such a way as to ensure complete reduction of the metals while also preventing their carburization. A monocharge was subjected to smelting reduction to obtain the world’s first specimens of directly-made alloy steel without the intermediate conversions – the production of pig iron and metallized semifinished products.

In order to reduce dust formation and entrainment during steel production, it is necessary to know its formation mechanism. Existing ideas are based on combined effects or on model idealized studies, whereas there are no direct studies of such fundamental processes as evaporation of melt of the Fe–C system at steel smelting process temperatures. In this work, iron vapor pressure and melt evaporation rate from Fe–C melts are measured at temperatures up to 2200°C. An equation is obtained for the temperature dependence of these parameters. The task of suppressing dust formation involves a reduction in reaction zone temperature during blowing a bath with oxygen with retention of a sufficiently high carbon oxidation rate.

The article shows the necessity of combining the heat treatment of heat-exchanger tubes with their straightening. It describes the principle of operation and the design of a unit developed to heat-treat tubes and straighten tubes in tension. The new unit ensures the formation of the prescribed stress state during heating and cooling, which results in straightening of the tubes and creates compressive residual stresses in them. The presence of those stresses makes heat-exchanger tubes less susceptible to stress-corrosion cracking and lengthens their service life. Results are described from successful tests of the proposed method in the heat treatment of 16 × 1.5 mm heat-exchanger tubes of steel 08Kh18N10T at the Pervouralsk New Pipe Plant.

Chemical composition, microstructure, contamination with nonmetallic inclusions, and corrosion resistance indices are studied for about twenty grades of steel. Dependences are determined for the effect of rolled product properties on pipe metal corrosion resistance indices. A concept of producing corrosion-resistant “SeverkorYuni” steels is developed for use in the housing and utilities sector.

Results are presented from calculation of the dimensions of the fusion zone in the hardfacing of rollingmill rolls by a composite strip electrode. The calculation is performed on the basis of the solution of a differential equation of heat conduction that accounts for the temperature dependence of the thermophysical properties of the material comprising the rolls. Heat propagation in a semi-infinite body undergoing hardfacing is modeled by the finite-element method. The values calculated for the depth of fusion agree well with the experimental data. The calculated results are used to determine the effect of the parameters of the composite electrode on the formation of the weld pool and the conditions necessary to obtain a macroscopically heterogeneous composition with a prescribed hardness distribution across the hardfaced bead (weld). The uneven wear being exhibited by such a heterogeneous hardfaced layer formed on the work roll of a roughing scale-breaker in a wide-strip hot-rolling mill is making it easier to remove scale from the surface of the rolled product.

The microstructure and mechanical properties of castings made of alloy Al+3%Mg were studied along with a tire mold made by low-pressure casting. The microstructure of the alloy was analyzed by optical microscopy, and scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to perform a detailed analysis of its structural components. Static tests of tensile strength were conducted and Brinell hardness was measured to evaluate its mechanical properties. The tensile tests were carried out at normal and elevated temperatures in order to simulate the service conditions of the mold.

Hard-alloy dies with channels of the traditional form and dimensions have been shown to have inadequate resistance to fracture during the drawing of nichrome and ferronichrome strips. Their durability can be improved by favorably directing the forces that are normal to the surface of the channel’s working zone, which reduces the probability of fracture. To do this, a drawing-die insert was made with a drawing channel having an outlet zone equal to 0.24–0.32 of the total length of the channel. Comparison of the traditional channel and the improved channel showed that the effect of the stresses created during service is smoothed out in the weak parts of the die. The effects of the highest stresses and stress intensity are reduced by using an insert with a larger cross section and a more massive yoke.

The operation of stamping is modeled in the software suite DEFORM-3D to determine the impact energy required of the hammer to completely fill the die in a single impact. The flow of the metal during stamping is analyzed and the probability of defect formation is estimated.

On blast furnaces that have never been operated with the injection of pulverized-coal and that first need to be provided with high-quality iron-ore-bearing materials and coke, the use of a technology that charges lump anthracite into the furnaces can significantly reduce coke consumption and the cost of making pig iron. The technology is especially effective if the furnace’s productivity is limited by problems in obtaining the desired finished product and it has to be operated at lower speeds or it runs more efficiently under such conditions.

Results are presented from work that was done to increase the service life of the submersible nozzles on a continuous caster at the Novolipetskii Metallurgical Combine and stabilize the steel-casting operation.

This article discusses reducing the hydrogen content of low-alloy steels for oil and gas line pipe and shipbuilding and improving these steel’s ductility. In addition to the saturation of the liquid steel with hydrogen, it is also possible for the steel’s hydrogen content to increase after it has solidified. For example, this could occur when slabs are heated in furnaces that are fired with certain types of fuel and have different atmospheres. When a furnace is fired with coke-oven gas and the internal pressure in the furnace is positive, the high hydrogen content of this gas helps saturate the steel with hydrogen. That in turn increases the steel’s contents of discontinuities and nonmetallic inclusions, which leads to the formation of structural stress concentrators and a decrease in ductility. Results are presented from physical modeling of the saturation of pipe steel with hydrogen during the heating of slabs made of the above-indicated types of steel. Aspects of the steel’s saturation in different furnaces atmospheres are examined, the degree of contamination of the steel by hydrogen is determined, and the formation of its structure and hydrogenation are studied. It is definitively established that an increase in the moisture content of the furnace atmosphere increases the degree of saturation of the steel by hydrogen. Recommendations are given on alleviating the hydrogen saturation of steel. It is noted in particular that it is necessary to replace coke-oven gas by natural gas for the slab-heating operation, shorten the heating time to an acceptable extent, and establish the correct values for gas pressure and the gas/air ratio in the furnace.

A new approach needs to be taken to the formation of high-strength thick-walled steel line pipe, since such pipe is characterized by a higher springback coefficient and greater deforming force than ordinary thin-walled pipes. A description is given of a two-dimensional numerical model for forming pipes in accordance with the JCOE scheme. Results are presented from experimental studies performed with the use of noncontact methods to measure the geometric parameters of tubular semifinished products on the stepped-forming section of a TESA 1420 line. The experimental results are compared to the results obtained by mathematical modeling. The results obtained from the investigation as a whole show that computer systems can be used to evaluate the effect of deviations in the geometries of the initial semifinished product and the deforming tool on the geometry of the tubular semifinished product after the forming operation. Such evaluations will make it possible to review present requirements on the initial semifinished product and the methods currently used to assess geometric accuracy after forming, as well as to correct the existing deformation regimes.

The expediency of using nanostructured carbon materials (graphene, fullerene black) as effective additives to a cast iron modifier is substantiated. Experimental results for preparation of high quality iron castings with nanocarbon additions in the presence of a combined modifier are confirmed by improvement of cast iron structural and tribological properties. The promising nature of using fullerene black (FB) as a comparatively cheap by-product of fullerene nanotechnology exhibiting improved tribological properties is demonstrated. The mechanism of graphitization of cast iron modified with FB-additive is revealed on the basis of existing studies and results of research in the field of nanomodification.

Studies are made of the use of hydrochloric acid for the autoclave decomposition of boehmite-kaolinite bauxites from the North Onezhky Deposit. The spatial location and structure of the bauxites are investigated, and the solid residue left after autoclave decomposition is examined by x-ray phase analysis and electron microscopy to study the mechanism of the bauxites’ dissolution. The data that is obtained confirms the presence of hard films of amorphous silica. These films prevent complete dissolution of the aluminum-bearing minerals: boehmite and kaolinite.

A study is made of the effect of the final density of the pulp in the pulp-thickening operation on the quality of the final flotation product at the Talnakh Concentrator Plant. The effect of the reagents that are used on the flotation process is thoroughly analyzed. The main relations which express the dependence of the quality indices of the finished concentrate on the thickening operation are examined and results obtained under actual production conditions are reported. The effect of the density of the incoming pulp in a flotation machine on the quality of the concentrate is evaluated.

Nitride leaching of copper-zinc sulfide middlings that are difficult to concentrate is studied with the aim of clarifying and supplementing results obtained previously. It is shown that organization of two-stage countercurrent leaching makes it possible to reduce the concentration of nitrate ions within leaching solution, to increase the degree of nitric acid regeneration, and to increase copper and zinc concentration in solution and precious metals in the residue.