Hot metal is a Fe-based alloy, generally having a carbon content of 4 - 5 percent, also containing other elements, and produced by a metallurgical process from iron ores. It is an intermediate product, which is the base material of steel-making. Raw materials required for production are: iron ore pellet, sinter, flux, and blast furnace coke. Ores are imported mainly from Russia and the Ukraine.
The raw materials charged from the top of the blast furnace move down towards the hearth. The carbon content of the blast furnace coke reacts with the oxygen content of preheated air (1100°C) and burns, and the gas generated in this way flows upwards, heating up and reducing the descending ore. Ore (and its gangue) melts in the lower zones of the blast furnace due to the high temperature developing due to the burning of coke, and the generated melt flows to the bottom part, i.e. the hearth, of the blast furnace. The resulting products are hot metal and slag, which are periodically removed from the blast furnace (tapping).
One of the by-products of metallurgical operations is top gas (mainly containing CO₂, CO, N and H) used for energy production, boiler heating, and after recycling, for preheating of the air blown into the blast furnace. Tapped slag in solid condition is used for many purposes, in both the cement and construction industries.
Ores are smelted in two blast furnaces. Blast furnace 1 and blast furnace 2 were commissioned in 1954 and 1957, respectively. Afterwards, both have been overhauled several times. The hot metal production capacity of ISD DUNAFERR is 1.3 million tons.
The Sinter Plant receives, stores and performs the physical and metallurgical preparation of arriving raw materials and additions. 12 bunkers and 2 lime powder silos are available for storing charge components. The charge fed on the sintering strand is composed of various ores, ore substitutes and fluxes, return material, as well as coke powder serving as fuel. The optimum grain size of the charge to be processed on the sintering strand is between 1 and 8 mm. As this grain size is relatively rare or very expensive, fine grained materials have to be prepared to have a condition that can be processed – this operation is called charge preparation. Charge preparation is a pelleting process, during which micro-grained parts stick to each other or to greater grained parts as an effect of charging water and binding material (burnt lime) and the rolling movement generated in the mixing drums.
The metallurgical preparation of ores is done on 2 pieces of Dwight-Lloyd traversing-grate agglomerating plants, on the so-called sintering strand. This method produces sinter or agglomerated ore, a material with physical and chemical properties that are the most favourable in terms of processing in the blast furnace. The production capacity of the sintering strands is 1 000 000 tons/year.
The Ore Dressing Plant and the Agglomerating Plant started operation in 1955 and 1956, respectively.