Том 61, № 7-8 (2017)

The use and advantages of simulation of cold rolling with allowance for the nonstationary and stochastic nature of its parameters are shown. The results of simulation of the parameters of rolling and electric drives are compared to experimental data obtained by oscillography on the Severstal 1700 five-stand cold-rolling mill. A method of finding the most effective technology from the characteristics of the rolling process and the rolled strip are developed based on a dynamic model. It is concluded that it is reasonable to use the dynamic model of cold-rolling process in developing new and improving existing technologies for the production of cold-rolled wide thin strips.

New technology is developed for Waelz treatment of electric arc furnace dust with the addition of calcium oxide to a charge. In this case, lead and halides are transferred into distillates. Calcium ferrite and zinc oxide remain in clinker. Clinker is sent for leaching zinc followed by zinc electrolysis from solution. The insoluble residue of calcium ferrite is used in ferrous metallurgy. The efficiency of this technology is determined by the process of charge preparation for loading into a Waelz kiln. In order to provide complete reaction of zinc ferrite with calcium oxide, it is necessary to provide effective component mixing; in order to provide selectivity of halide and lead liberation, reducing distillate volume, a powder mixture is pelletized. Exploratory research is conducted for preparing pellets of a mixture of electric arc furnace dust with lime, and the effect of some binder reagents on pellet strength is demonstrated. The following optimum parameters are determined for charge pelletizing from electric arc furnace dust and calcium-containing flux under conditions of a plate-like granulator: pelletizing duration 15 min; granule moisture content 19–20%. With the use of an intense type mixer-pelletizer, the optimum moisture content is 13–14%, which is connected with the improved conditions for pellet compaction. Comparison of various inorganic and organic additives for mixture granulation shows that the best are additives containing sodium hydrate sulfate, although their optimum consumption is unacceptable for the technology of material pyrometallurgical treatment. The presence in the production mixture of calcium-containing flux makes it possible to use it also as a binding additive for pelletizing calcium hydroxide in the form of an aqueous suspension. Feeding a pelletized mixture of electric arc furnace dust with lime into a Waelz kiln makes it possible to provide effective reaction of charge components in the kiln and to reduce to reduce escape of dust.

VNIIMETMASh completes modernization of an existing section continuous steel casting machine for the metallurgical plant of Baku Steel Company (Azerbaijan). The work makes it possible in CBCM-2 with base radius R = 6 m to produce round pipe billets 130, 170, 190, and 220 mm in diameter, and also square billets 130 ×130 mm in cross section.

Quantitative estimation of structural banding in alloy steels 40KhN2MA, 38KhGMA, and 20KhN3A is performed. The dependence of anisotropy index according to GOST R 54570 (ASTM E 1268) on the steel bar diameter and sample selection position is determined. It is shown that there is a direct relationship between structural banding, specified by the anisotropy index and steel mechanical properties (scatter of the microhardness values and anisotropy of the impact strength).

The SMS Meer ring-rolling mill and RKP 600-2500/600 expander installed at the Electrostal Metallurgical Plant are described. The production of solid-rolled rings of wide ranges of dimensions and grades on radial-axial ring-rolling mills was mastered at this plant in 2014–2016. Various sequences for the production of solid-rolled rings were tested to find the optimal one that produces rings of the required quality.

On the basis of physicochemical prediction of the effect of component content on the phase and structural transformations, it is shown that in order to prepare a favourable ferrite-pearlite microstructure and to ensure the key capacity of round rolled product for cold upsetting, it is preferable to obtain in special alloy steels 40Х, 38KhGNM, 35KhGSA, 30G1R, and 12KhN an element content close to the lower grade limit. A study of the microstructure and hardness of round-rolled specimens from steels 35KhGSA, 38KhGNM, and 40Х establishes that isothermal annealing at 20–50°C below the А1 temperature and nonisothermal annealing at 1–30°C below the А1 temperature are the optimum for spheroidizing heat treatment. In this case, a different fraction of globular pearlite is obtained in the metal microstructure depending on the steel grade: 35KhGSA about 90%, 38KhGNM and 40Х about 30%, and in all cases there are favorable results for cold upsetting tests. The defining effect of surface defects and rolled product structural state on cold upsetting capacity is demonstrated.

Rational reduction and tension schedules and roll profiles for 150/500×400 four-high reversing mill and 350×450 two-high reversing mill were developed and studied to increase the output of strips of high accuracy. For the 150/500×400 mill, increasing the work roll crown from +0.1 to +0.15 mm, the specific back tension from 0.12–0.16 to 0.14–0.18 МРа, and the specific front tension from 0.16–0.18 to 0.18–0.20 MPa appeared to decrease the transverse thickness deviation of strips by 10% compared with the conventional reduction and tension schedules. For the 350×450 mill, increasing the work roll crown from +(0.04–0.07) to +0.09 mm, the specific back tension from 3.3 to 8.7 MPa, and the specific front tension from 4.44 to 10.0 МРа appeared to decrease the transverse thickness deviation of 1-mm strips to 0.039 mm, which may be considered high accuracy. A mathematical model is proposed to analyze the stress-strain state of wavy strips with allowance for hardening. The numerical modeling showed that the tangential stresses are maximum on the upper and lower faces of a 0.5h₁ strip, while the radial stresses are maximum in the neutral plane of the strip.

By optimizing the rounding radius of the corners of the rectangular cross-section of die channel in its deformation and sizing areas, angular rounding capacity is increased, metal laminar flow is achieved, and the deformation scheme is improved. As a result, there is a significant improvement in hard alloy die life, strip breakage during drawing is eliminated, and product quality indices are improved.

A sorption method is proposed for cleaning industrial effluent with a new nanostructured complex sorbent based on Taganskoe deposit bentonite clay and mineral wool production waste. It is shown that with mechanical activation of bentonite clay together with mineral wool production waste there is an increase in clay particle content with a size less than 1 μm. It is established that for comprehensive and effective cleaning of electrolysis effluent from heavy metal ions a nanostructured complex sorbent (NSCS) is recommended based on bentonite clay from the 11th level and mineral wool production waste with observation of the following optimum conditions: 2:1 ratio of components in NSCS of 11th level bentonite clay : mineral wool production waste; rational mechanical activation scheme with grinding and nanostructuring of complex sorbent starting materials for 15 min; S:L = 1:100 (1 g of paste (in terms of dry substance) to 100 cm³ clean water); sorption time 3 h with constant stirring.

The sintering process in a sinter machine with a sintering area of 224 m² involving recirculation of flue gas to reduce the emission of harmful substances into the atmosphere and its flow through a bag filter to be installed after the existing electrostatic precipitator is analyzed. Alternatives of supplying a portion of the flue gas alone or mixed with atmospheric air or hot air from the sinter cooler to the bed to increase the oxygen content of the gas are considered. It is shown that forcing atmospheric air into the bed is inappropriate. It is recommended to recirculate a mixture of 70% flue gas and 30% air. Implementing the recommended alternative will reduce the gas flow through the bag filter by 30–35%, the CO emissions into the atmosphere by 8136 tons/yr, and the solid fuel consumption by 5600 tons/yr.

Results are provided for work conducted in the Magnitogorsk Metallurgical Combine blast-furnace workshop for production satisfaction of a blast-furnace automatic control system by stagewise introduction of local systems combining into one automated system for control, optimization, and prediction of blast furnace smelting (ASCOP BF). Using mathematical models and special ASCOP BF algorithms for each blast furnace, there is continuous automatic monitoring of radial and circumferential gas distribution in the bell, circumferential gas distribution in the furnace hearth, material and thermal balances of smelting and furnace heating; optimization of the smelting gas dynamic regime, radial and circumferential gas distribution in the bell, circumferential gas distribution in the furnace hearth, smelting recovery processes, thermal state of a furnace and melting zone parameters; prediction of silicon content in cast iron. The order of conducting operations is proposed and substantiated for achieving maximum productivity and minimum coke consumption with given smelting raw material and operating conditions. It is shown that the mathematical models used in the system by the process described are ready for use in blast furnace automatic control systems already created for blast furnaces in other metallurgical enterprises in order to achieve the best smelting indices.

A system is described for development of new products and technology based on modeling, simulation, and laboratory testing for processes applied to VMZ 5000 rolling mill conditions. Approaches are demonstrated for creating slab heating technology using mathematical modeling of carbonitride particle dissolution and austenite grain growth as well as an approach to creating strategies for rough rolling by new Hot Rolling Recrystallization Model (HRRM) software and the finishing stage. Specific features of rolled product structure formation during cooling and alloying concepts in relation to steel strength class are described. Results are given for industrial production, including steels for underwater pipelines and pipelines in areas near active tectonic faults.

Results are given for evaluation of the effect of longitudinal deformation on the change of the mechanical properties and steel properties with a two-phase pipe metal structure previously given low-temperature heat treatment simulating application of an anticorrosion coating. A reduction in steel deformation capacity to the minimum permissible level is evaluated by a criterion δ_un ≥ 3% and σ_y(R_t0.5)/σ_u ≤ 0.96–0.98. As a result of testing plates subjected to longitudinal tension with plastic deformation ε_p = 1.5–7.0%, it is shown that exhaustion of steel deformation capacity is predicted in the transverse direction with preliminary deformation ε_p ≈ 5%, and in the longitudinal direction with ε_p ≈ 4–5%. SEM and TEM methods are used to study the effect of steel main structural characteristics whose presence facilitates retention of capacity for steel strain hardening after heating (200–220°C, 5 min): fine islands of twinned martensite, fine cementite particles and abundant precipitation of nanosize particles of Nb and V carbonitrides. During branch pipe bending deformation (ε_p ≤ 3.0%) in a two-phase steel structure (main components are ferrite and lath martensite) includes transformation of residual austenite from the MA-component in twinned martensite.

The effect of limestone on the hardening of pellets during heat treatment is studied. Procedures and results of laboratory experiments are presented. They show that the strength of pellets varies with the limestone content of iron-ore pellets produced from magnetite concentrate of the Kursk Magnetic Anomaly.

The chemical composition of raw material used plays a vital role in achieving the required product quality, in particular, in ferrochrome alloy production. Different types of ore are used in the South Africa ferrochrome industry, including lumpy and small lumpy chrome ores. Reduction of lumpy ore has its own features during manufacture when used alone in the furnace or mixed with small lumpy chrome ore. It is important to test lean chrome ore and investigate its behavior alone and when blended with other chrome ores. Many phases can form during reduction, governing final product composition. Therefore, it is important to understand the behavior of a specific type of ore during its reduction and its effect on phases formed on mixing with different types of chrome ores. In this research, behavior is studied during reduction of lumpy, small lumpy, and lean ores at 1300 and 1500°C. A graphite crucible is used, placed in a silica crucible. After preparing the leading sample, the mixture is placed in a tubular ceramic furnace and established at the required temperature. Products obtained at different temperatures are rapidly water quenched to avoid much oxidation. Behavior is evaluated with solid-phase reduction and with reaction of a solid reducing agent with different ore melts. The amount of phases formed at the working temperatures is evaluated. x-Ray phase analysis and scanning electron microscopy are used for identification and quantitative evaluation of phases present in the products.