Cherepovets Metallurgical Combine Research Articles

Pilot Implementation of the Technology and Equipment for Feeding Cooling Inoculators Into the CCM Mold at Severstal

In the steel production at the Severstal Cherepovets Metallurgical Combine, we conducted pilot tests of equipment and technology in the continuous casting and simultaneous application of slag-forming mixtures and inoculators as a fraction. We observed improvement in the macrostructure in the axial zone of the ingot as a consequence of a more intensive cooling, as well as by increasing the number of crystallization sites. As an alternative to the method of introducing discrete inoculators, we propose a method and develop equipment designed to deliver a continuous ribbon chiller in the mold of the continuous caster. We determine the main parameters of the equipment and technology for introducing the ribbon into the mold of the continuous caster.

Analysis of Asymmetric Rolling Efficiency for Improving Rolled Strip Accuracy

Technology is analyzed for asymmetric rolling in order to improve rolled strip precision in large units: a 1700 strip cold rolling mill and a Severstal Cherepovets Metallurgical Combine 2000 broad-strip mill; in an ArcelorMittal Temirtau (Kazakhstan) 1700 continuous broad-strip mill. Research demonstrates the efficiency of asymmetric rolling for improving rolled strip precision. In the ArcelorMittal Temirtau 1700 broad-strip mill with asymmetric rolling of strip 2.0–3.0 mm thick non-flatness is reduced on average by 31% compared with symmetrical rolling. Trials of asymmetric strip rolling of corrosion resistant steel 12Kh18N10T in a Chelyabinsk Metallurgical Combine 500/1500×1700 reversing four-roll mill demonstrate the possibility of cold strip rolling with standard flatness with mill adjustment for peripheral speed mismatch of the upper and lower working rolls per pass by 2–7% and simultaneous excess of forward tension over the back tension by 3–7%.

Making BOF Steelmaking More Efficient Based on the Experience of the Cherepovets Metallurgical Combine

Results are reported from a study of BOF steelmaking at the Cherepovets Metallurgical Combine (CherMK), and the main measures that can make the BOF shop more efficient are described. The measures include improving the logistics of transport operations, the installation of new production equipment, or upgrade of the existing equipment. It is shown that the technical-economic indices of the shop can be improved in a short period of time at minimal cost by adopting a comprehensive approach to modernization of the present facilities.

INVESTIGATION OF AGGLOMERATES CHEREPOVETS METALLURGICAL PLANT JSC “SEVERSTAL” IN THE RANGE OF BASICITY 1.0 – 3.0

Applied to the burden and process conditions Cherepovets Metallurgical Combine “Severstal” studied mechanical properties and mineral com- position of the agglomerates in the range of basicity from 1,0 to 3,0.

Determination of the Optimum Size of Skip Coke

The unit consumption of coke in blast furnaces is decreasing significantly thanks to the implementation of various measures, including introduction of the practice of injecting pulverized-coal fuel (PCF). However, the decrease in the volume fraction of coke in the charge has appreciably increased the mechanical, thermal, and chemical loads on this material. For example, the introduction of PCF injection technology has increased the coke-based ore burden from 2.5‐3.5 to 4‐5 and lengthened the time these materials are in the furnace from 6‐8 to 9‐10 h. Moreover, the increase in the amount of time that coke is in the furnace is being accompanied by proportionate increases in the quantities of pig iron, slag, hearth gases, carbon dioxide, and alkalis that pass through it. This situation has quickly made it more urgent to improve the hot-strength index of coke while also improving its preparation and optimizing its fractional composition. The optimum fractional composition of the skip coke that is charged into a blast furnace has been a topic of discussion since the last century. In the course of attempting to optimize this characteristic of skip coke, a number of researchers have proposed using the fraction 25(30)‐60 mm to bring its coarseness closer to that of the ore-bearing charge materials and reduce the value of the ratio of the maximum size of the coke lumps to their minimum size to two or less. The reasoning behind these conclusions is that the “...best gas permeability is obtained during the initial part of the charging operation, when the finer fractions do not fill the interstices between the coarse fractions” [1]. Trial heats conducted with graded coke of the above-indicated fraction showed an improvement in the main technical-economic indices [2‐4]. Another group of researchers has recommended using coke of the 40‐80 mm fraction, especially to increase the smelting rate and the quantity of liquid smelting products obtained in large blast furnaces. To illustrate, the content of the 40‐25 mm fraction of skip coke rose to 25% at the Cherepovets Metallurgical Combine when the efficiency of its coke screens declined. This development seriously complicated the operation of the combine’s 2700-m 3 blast furnace [5].

Phase composition and structural features of Severstal Cherepovets metallurgical combine industrial agglomerate

As applied to production and charge conditions of Severstal Cherepovets Metallurgical Combine, the whole production cycle has been studied for industrial agglomerate from the structural features of the granulated charge to the phase composition and mechanical properties of the finished product. x-Ray phase analysis is used to establish the mineral composition of agglomerate silicate binders and their structural formulae are calculated.

System for monitoring the continuous casting of metal sections to prevent the formation of rhombicity

Rhombicity is a shape flaw seen on square semifinished products and is caused by a difference in the dimensions of the diagonals of the product’s cross section. It is a defect common to semifinished sections. A study conducted by the Pribor Scientific-Technical Center in the electric steelmaking shop of the Severstal Cherepovets Metallurgical Combine included tests of a system for real-time monitoring of the temperature regime and cross-sectional profile of semifinished products . The system was tested on stand No. 6 of the continuous section caster in the shop. The model incorporated into the system to describe the crystallization of semifinished sections makes it possible to analyze operating data in real time and calculate characteristics of the metal’s solidification. The equipment of the system and the crystallization model were both developed by Pribor.

Mastering the production of K70 skelp for large-diameter pipe on a 5000 mill

A technology for making a new generation of skelp in thicknesses from 15 to 27 mm for large-diameter pipes (LDP) has been developed on the 5000 mill at the Severstal Cherepovets Metallurgical Combine with the use of modern methods and metallographic techniques. The quality of the rolled product meets the requirements of the corresponding TU standards for steel of strength class K70 with respect to its strength and toughness-ductility characteristics, including the amount of tough component in the fracture of specimens in drop-weight tear tests (DWTT). Controlled rolling with accelerated cooling in an ACU (with possible subsequent tempering of the rolled product) was chosen as the most suitable technology.

Developing and testing structural steels with superior resistance to cold and to cracking in hydrogen-sulfide-bearing media for use in the production of electric-welded (HFC) oil-field tubing

New grades of steel for oil- and gas-line pipe of strength class K55 (steel 07GFB) and for pump-compressor tubing of strength class Ks (steel 18GFB) have been developed and undergone factory testing. The Cherepovets Metallurgical Combine Severstal has tested a new technology for making these experimental steels in a converter and subjecting them to controlled rolling to obtain coiled skelp on a 2000 continuous mill. The Volgorechensk Pipe Plant (owned by the company Gazpromtrubinvest) has used the steels to prepare trial batches of pipes that meet the established requirements.

Compliance with guaranteed specifications for rolled coils having strength grade Kh70

Required specifications for rolled materials intended for fabrication (without heat treatment) of spiral-seamed gas pipes in strength category Kh70 using a continuous wide-strip mill can be maintained by complying with basic principles regarding processes for controlled rolling of steels with finely-dispersed ferrite-bainite microstructure. High-strength steels should have low carbon content, increased niobium additives, and increased additives of elements that facilitate formation of bainite microstructure. Implementation of this process on the 2000 mill at the Severstal Cherepovets Metallurgical Combine enabled production of rolled material with the following specifications: σ y ≥ 535 N/mm2, σ u ≥ 640 N/mm2, δ 5 ≥ 23% (for longitudinal and transverse samples), KCV−20 ≥ 160 J/cm2, and B(IPG−20) = 90–100%, as well as a maximum 7% nonuniformity of strength properties for transverse samples.

Crushing hot sinter with the use of cantilevered grates

The sinter plant operated by the Cherepovets Metallurgical Combine Severstal’ is using cantilevered grates to crush the hot sinter. The use of such grates solves the problem of improving the durability of the crushing machines and results in a substantial monetary savings.

Optimizing the technology for making automobile sheet 08Yu based on the physicochemical principles of ladle metallurgy

The main method of eliminating the possibility of having the steel contaminated by nonmetallic inclusions is optimizing the parameters of the ladle treatment on the basis of reliable physicochemical representations of the processes of refining, alloy, and finishing of the steel, the interactions of the metal and slag phases, and other aspects of ladle metallurgy. This article examines the main steps being taken in this direction at the Cherepovets Metallurgical Combine Severstal’ in the production of high-quality automobile sheet 08Yu.

Use of slags from the production of manganese alloys in steelmaking

roalloys. One promising direction is the use of manganese slags in steelmaking, particularly in the oxygen-converter conversion of low-manganese pig irons. The addition of such slags in the necessary amounts simultaneously solves the problems of increas- ing the efficiency of oxygen-converter steelmaking and saving manganese ferroalloys. Studies were performed on the use of ladle residues (crests) of slag from the production of silicomanganese at the Nikopol' Ferroalloys Plant to make steels at the Nizhniy Tagil combine, Cherepovets Metallurgical Combine ("Severstal'"), and West Siberian Metallurgical Combine in 160-, 350-, and 300-ton converters from a semifinished product and pig iron with man- ganese contents of 0.02-0.05, 0.15-0.35, and 0.4-0.7%. The blowing rates were 1.9-2.4, 1.4-2.0, and 2.8-4.0 m3/ton.min, respectively. Ladle residues of slag from the production of silicomanganese consist of the alloy silicomanganese (15-25%) and the ferroalloy slag itself (75-85%). The ferroalloy slag contains 16--20% MnO, 8-10% A1203, 4--6% R20 , 3.5-4.5 MgO, 40-50% SiO 2, 10-15% CaO, and 0.7-1.2% S, and it has a melting point of 1250~ The ladle residues contain at least 30% MnOto t.

Preparation of a quartz-clay ramming compound under conditions of converter production of the Cherepovets Metallurgical Combine

Preparation of a quartz-clay ramming compound under conditions of converter production of the Cherepovets Metallurgical Combine

Tests of olivinite-containing refractories in steel teeming ladle linings

The effectiveness of the use of the olivine-containing refractories in Cherepovets Metallurgical Combine open hearth teeming ladle linings is obvious.

Corundum-graphite submerged nozzles for a slab continuous casting machine

A method of production of corundum-graphite submerged nozzles with thickening in the slag belt has been developed and introduced. The life of these nozzles in casting of high-manganese types of steel is as high as 700–800 tonnes (four or five heats) under the conditions of casting in the slab continuous casting machines of Cherepovets Metallurgical Combine Converter Shop. The maximum life obtained has been 866 tonnes of steel.

The influence of preliminary compaction of the mixture on the quality of chamotte refractories

A method of production of ladle brick making it possible to eliminate scrap of parts for separation, to reduce their porosity, and to increase the compressive strength has been developed. Under the conditions of Borovichi Refractory Combine the porosity has dropped from 17.3–18.4 to 15.5–17.1% while the compressive strength has increased from 27–40 to 68.6–93.0 N/mm2. The desirability of use of Kudinov deposit semiacid kaolinite-hydromicaceous clay as a raw material for the production of dense ladle brick and also the possibility of use of Ust'e-Brynkino deposit BLP-1 clay have been shown. Tests of experimental production lots of ladle brick in the 130-ton ladles of Cherepovets Metallurgical Combine Electric Melt Shop showed a significant advantage of them in wear resistance over the multichamotte compacted ladle brick of Borovichi Refractory Combine. The use of the experimental ladle brick produced using the method developed increases the life of steel-teeming ladle linings by 30%.

Decarbonizing corrosion-resistant steel by blowing with an argon-oxygen mixture through a submerged lance

The Cherepovets Metallurgical Combine has tried blowing a high-chromium melt in arc furnaces with a lance submerged in the slag or positioned at the boundary between the slag and the metal. Tests which were conducted involved the production of corrosion-resistant steel 08-12KhlSNIOT in a 10-ton arc furnace with the use of a single-nozzle oxygen lance. The design of the lance ensured a rate of flow of coolant water in the head of about 6 m/sec at a water consumption of 12 tons/h. This arrangement, in combination with the additional cooling of the reaction zone by argon, is sufficient to provide reliable operation of the lance when it is submerged in the melt to the slag-metal boundary.

Continuous monitoring of the temperature of molten metal

Such monitoring is done on the open-hearth furnaces and 100-ton arc furnaces at the Cherepovets Metallurgical Combine. The broad introduction of the practice of monitoring the temperature of molten metal in arc steelmaking furnaces is being held up by the complexity of the equipment design, the short life of the protective caps in the highly active slags, and the effect of the electromagnetic field of the electrode on measurement accuracy. The device used at the Cherepovets combine, which is inserted through the furnace wall, cannot be used on the 5-ton arc steelmaking furnaces at the "Elektrostal'" plant.

Reconstruction of strip loopers at a perforation unit

Experience in operation of the perforation unit at the Cherepovets Metallurgical Combine has shown that the existing loopers, which store the strip below the level of the press die in pits (Fig. i), has a significant effect on the life of the dies and, thus, on the productivity of the unit and the accuracy of spacing of the perforated holes in the strip. The free hanging of the strip in the pits, combined with the original parameters of the pits and the servo and the fact that the strip is fed into the die periodically, leads to vibration of the die and produces dynamic loads on the press and die feed mechanism. The latter developments in turn shorten the life of the die. Taking into account the positive experience gained in operating similar automatic units at the Kama River Truck Plant (KamAZ) and the Volkhov Aluminum Plant (VAZ) in which the reserve strip is stored above the press, we developed and introduced at the Cherepovets combine an experimental design of looper with the same arrangement, i.e., location of the strip above the level of the die and the retention of a minimum reserve of strip in the looper. The design of loopers located ahead of and after the press represents a floor-type roller table with empty undriven rolls and two pairs of undriven rolls which form a reserve of strip between them in the form of a loop. The size of the loop is controlled by a servo. The distance between the loop-forming rolls is regulated. Taking into consideration the step-by-step feed of the strip into the die and the different linear speeds of the strip in the press feed mechanism and on the sections ahead of and behind the press, to ensure reliable operation of the perforation unit in the automatic regime it is necessary to know the minimum and maximum values of the raising of the strip above the die H (Fig. 2) and the distance between the rolls A. It is necessary to know the minimum strip-lifting height Hmi n to prepare the automatic control system for operation so that it will ensure feeding of the strip and die without slip in the press feed mechanism and its pulling out from the press and roller-straightening machine during operation of the coiler. Knowledge of the maximum value Hma x guarantees a maximum reserve of metal before the press and coiler, so that no plastic strains will be made in the strip. With a substantial reserve of metal and a fixed distance between rolls A, the strip may be sent so that it will be plastically strained and will require additional straightening. In connection with the fact that the force needed to keep a bent thin strip in the elastic state exceeds the force exerted by the weight of the strip, to simplify the determination of H (Fig. 2) we assume that the strip is bent symmetrically along the radii RI and R2 relative to the halfway point between the rolls, i.e., we will not consider the weight and the effect of inertial forces on the shape of the bent strip. These curvature radii are determined on the basis of the condition that no plastic strains will occur in the bent strip when they are minimal. For low-carbon steels, the relative curvature radii at which plastic strains will appear lie within the range