Technology
OEMK’s technological process includes the following stages:
Production of fluxed oxidized pellets
Pellet and Direct Reduction Plant produces partially fluxed oxidized pellets out of the iron ore concentrate supplied from the Holding’s Lebedinsky Mining and Processing Plant (Lebedinsky GOK). The slurry is transported to OEMK through the slurry pipeline 26.5 km long.
In the Pellet Plant, the slurry is processed on disc vacuum filters to obtain cake (moist concentrate), which, after the addition of bonding and fluxing materials, is transported to a mixer and then to pelletizers where green pellets are made.
The pellet firing is carried out at a horizontal-grate machine 480 square meters in area. The output capacity of the Pellet Plant is 3.300 thousands tons per year. Oxidized pellets are 5-20 mm in size; minimum Fe content in the pellets is 67%, silica content is 3.3% max, basicity (CaO/SiO2) is 0.4 min, strength is at least 250 kg/pellet.
Oxidized pellets are fed via transporters to the shaft furnaces of the Direct Reduction Plant.
Production of metallized pellets (DRI)
The Direct reduction Plant produces metalized pellets out of oxidized pellets using the MIDREX technology, i.e. by means of heated bustle gas, which is obtained from natural gas after its conversion in reformers. The Direct reduction Plant is equipped with four DRI units with the total output of 2.2 million tons of metallized pellets per year. These furnaces produce metallized pellets, which is then transferred to the Electric Arc Furnace Shop as well as shipped to other steel factories, and also exported. OEMK’s thermally passivated metallized pellets are high-quality metallurgical raw material characterized by high iron content, low content of sulfur, phosphorus, and nonferrous metals, and low reoxidation susceptibility. The metallized pellets are safe for transportation in open railroad carriages, as well as in river crafts and sea vessels. When moisturized by atmospheric precipitations, metallized pellets virtually do not lose any of their metallurgical properties, so they are fit for storage in open areas.
Steel smelting
From the Direct reduction Plant, metallized pellets are fed via the transporters to the Electric Arc Furnace (EAF) Shop, where they are melted in 150-tons Electric Arc Furnaces to get steel. The EAF shop’s output amounts to 3 million tons cast billets per year.
Smelting is performed by means of a single-slag process with the use of 60 to 100 % metallized pellets in the furnace charge. The steel production technology includes secondary refining and alloying at the argon blowing units, vacuum degassers, and ladle furnaces. The liquid steel is cast on continuous billet-casting machines. The resulting cast billets and blooms are transferred to the rolling Mills №1 and 2 for rolling or for shipping to outside customers.
Today OEMK’s product range includes about 2,000 grades of high-quality carbon and alloyed steels. Supplied in accordance with national and international standards as well as individual specifications from the customers, these steels meet all requirements of the parts producers and final customers (rerolling, seamless pipes production, forging, cold massive forming, machining, etc.) in various industries.
Rolling
The plant’s rolling facilities include two mills:
- Rolling Mill №1 (Mill-700) produces both commercial products — heavy sections, tubular billets, square bars for forging, die forming, and rerolling and also bars for subsequent re-rolling on the Mill-350.
- Rolling Mill №2 (Mill350) produces small and medium sections.
MILL–700
Rolling Mill №1 has an annual production capacity of 2.1 million tons of rolled products.
The mill comprises the following facilities:
- Cast billet storage with the capacity of 35 thousand tons. Each heat is stored in a separate cell, and information about every billet and storage place is entered in the information database.
- Three continuous heating furnaces with walking beams and one homogenizing furnace.
- Large sections Rolling Mill700 comprises a breakdown reversing stand “1000”, two continuous four-stand groups with vertical and horizontal rolls, shares, and hot-cutting saws.
- Heat treatment and cooling area consisting of three furnaces and four notched cooling beds.
- High bay intermediate rolled stock warehouse with the capacity of 17,000 tons controlled by the automatic control system that allows tracking the specification requirements, weight and storage point of each bundle.
- Rolled product finishing division comprising abrasive peeling and machining areas, here the rolled bars are subjected to ultrasonic and magnetic inspection for internal and surface defects at Dr. Foerster, Volna7, Karl Deutsch inspection units.
The existing Rolling Mill control system is entirely automated, which frees the operator from the need to interfere with the rolling process and minimizes the possibility of errors.
MILL-350
Rolling Mill №2 has an annual design capacity of 1 million tons, including 700,000 tons of medium sections in rods and 300,000 tons of small sections in rods and coils.
Rolling Mill №2 comprises the following technological areas:
- In-line inspection and finishing of original bars.
- Small and medium sections Rolling Mill-350.
- In-line heat treatment of coils and rods in three through-type thermal furnaces.
- Out-of-line inspection and finishing of rods.
- Heat treatment in two protective gas furnaces.
The equipment in the shop allows to use the following cutting-edge solutions of the rolled sections manufacturing:
- All original bars (150 mm and 170 mm squares) are straightened, descaled, subjected to surface inspection and, if necessary, abrasive scarfing.
- Prior to rolling, the bars are preheated in two continuous walking beam furnaces. A low temperature bar heating technology is provided (to around 900°C), which reduces the energy consumption by 15% and considerably reduces the rolled product decarburization.
- Scale is removed off the bar surface using water under high pressure at the water descaling unit.
- Rolling is made in continuous lines, one for small sections and one for medium ones. The stands’ high stiffness, automatic speed coordination, and a looping system in the finishing small sections group help to receive high precision rolled products. Behind the small sections line is installed a KOCKS gauging block. Hot-gauged rolled bars have the diameter tolerance +/0.15 mm. In-flow is installed the equipment for surface quality inspection and geometry verification on hot bars. The rolled products are made as rods up to 12 m long (in bundles up to 10 tons in weight) and in coils (weighing up to 2.45 tons).
- Both lines of the Mill-350 are equipped with rolled product quick cooling units. Thanks to the strain-heat hardening technology it is possible to obtain, right in flow, the rolled metal whose application characteristics match those of heat treated products (rolled stock for cold massive forming). It considerably decreases the buildup of scale on the bars’ surface and improves its pickling ability. Quick cooling helps to produce high-tensile rebars.
- In-flow heat treatment of rods and coils combined with strain-thermal hardening ensures a wide range of mechanical properties and structure of rolled metal.
- Out-of-the-line finishing encompasses straightening, surface defect inspection on Karl Deutsch’s Echograph, ultrasonic inspection at Dr. Foerster’s Circoflux, rolled product mixing check at Dr. Foerster’s Magnotest, selective abrasive scarfing, complete abrasive grinding, turning of round rods. The rolled products are turned with the accuracy degree of h11 and h12. On the BUNDLE-ROD unit, hot rolled coils are processed to obtain machined rods up to 6.5 meter long with the cutting accuracy of +/5 mm. The machine also provides polishing.
- Heat treatment of rods at the out-of-the-line finishing section is made in Ebner protective atmosphere furnaces, so it is possible to obtain the preset microstructure avoiding oxidation and decarburization.
