Steel is a flexible, high-strength, readily formed iron alloy. Its characteristics can be changed to a great extent by different processes, for instance its hardness can be increased to almost that of diamond. Several ways of its production is known, one of the most widespread ways all over the world is the basic-oxygen steel-making process also applied by DUNAFERR, which is an oxidizing melting process. During this the raw materials are charged into a big “melting pot” having a lining, the so-called converter. The main charge materials, pig iron and solid steel scrap are put into the converter together with fluxing agents. Then oxygen is blown in through the upper hole, the water-cooled injection lance. Oxidizing melting takes place at a high temperature, the final product of which is crude steel. During blowing 99 percent of the carbon content of charged raw materials burns out, silicon content is totally oxidized together with one part of manganese and phosphorus content, and desulphurisation also takes place. The basic oxygen steel-making process started in August 1981 in Dunai Vasmű (Danube Ironworks). Two basic oxygen furnaces with the capacity of 135 tonnes each operate in the Converter Plant of the Steelworks in DUNAFERR Co. Ltd. Production is going on in an operation of 2/1 alternately, but in case of need both furnaces can be operated. 32-33 charges of crude steel are produced in the plant on a daily basis, and the overall quantity is forwarded to the continuous steel casting plant for processing.
Slab is a rectangular semi-finished product with different cross-section dimensions that is produced in the continuous steel casting plant. Its raw material is pig iron from the basic oxygen furnace, which is cast to steel slabs on a vertical production line using different equipment and auxiliaries. During the operational process the casting ladle full of steel is taken to the level of casting by cranes, i.e. to the height of 20 meters, and then it is turned by the ladle-turning fork into the position of casting. At the bottom of the ladle a hydraulically movable closing device with refractory panels controls the quantity of the steel discharged. Steel is placed in a distributing pony ladle, and then while going through the crystallizer and cooling systems its state is changed from liquid to solid. Then the steel strand going continuously downwards is cut to pieces with the required dimensions by a gas cutting installation.
The entire production process in the continuous steel casting plant of the Steelworks in DUNAFERR Co. Ltd. is controlled by computers. Slabs with the uniform thickness of 230 mm are cast in the continuous steel casting plant with two lengths (3000-4200 mm, as well as 7000-8400 mm) and seven widths from 860 to 1550 mm. The steel slabs cast are forwarded to the hot rolling mill for processing.
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