Basic Oxygen Steelmaking

Several variations of the oxygen steelmaking process have been developed. They include bottom-blown converters (e.g., the OBM process, the Q-BOP process and the LSW process) and the top-blown converters (e.g., the LD process, its variant the LD-AC process, the Kaldo process and the Oberhausen process) [27.3,27.8]. 

A basic oxygen furnace is shown in Fig. 27.2 and a cross-section is given in Fig. 27.3. The furnace is lined with dead-burned magnesia refractory impregnated with carbon, lypically the charge consists of molten iron at about 1250 °C (80 %), scrap iron (18 %), plate iron (1 %) and iron ore (1 %). Varying the amount of 

Oxygen is blown into the molten metal at supersonic speeds through a water-cooled lance for about 15 min. to oxidise some of the impurities. Two to three minutes after the start of the oxygen blow, quicklime (30 to 50 kg/t of hot metal) soft-burned dolomite (10 to 25 kg/t) [27.21] and, optionally, fluorspar (up to 

The removal of impurities from the molten metal during the course of the oxygen blow is illustrated in Fig. 27.4. Silicon is removed rapidly at the start of the blow (27.1), carbon is removed progressively throughout the blow (27.2), with phosphorous being removed towards the end of the blow (27.3). Manganese, and iron are also oxidised (27.4-27.6). 

Si02 + 3ChO — (C30)3Si02 P2O5 + 3FcO — Fc3(P04)2 Fe3(P04)2 + 3CaO Ca3(P04)2 + 3FeO 

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Fig. 4. Sketch of a basic-oxygen steelmaking furnace, where an oxygen lance is iaserted through the mouth of the furnace (1).

The BOS (Basic Oxygen Steelmaking) process is the major modem process for making bulk steels. Apart from special quality steels (such as stainless steel), all flat products, and long products over a certain size, are rolled from steel made by the BOS process. 

Basic Oxygen Steelmaking. New Technology Emerges Proceedings of the Conference, Metallurgical Society of London, 1979. Contains papers on refractories for conventional and new bottom-blown vessels. 

The open hearth steelmaking process was invented in 1863 and up to the early 1960s was the principal means of producing steel in the U.S.A. and the U.K. [11.2]. Since then, it has been displaced by the basic oxygen steelmaking processes (see sections 27.4 and 27.5). 

The rapid growth of the Basic Oxygen Steelmaking process in the 1960s required kilns which could produce a 6 to 40 mm quicklime, with a relatively high reactivity, low residual % CaCOs and low sulfur content. Initially, much of this new demand was met by Calcimatic and rotary kilns. 

Before the 1960s, the premium products were lump limes, with particle sizes up to 250 mm. With the advent of the Basic Oxygen Steelmaking process (section 27.4), however, the lead product for many producers became a 10 to 40 mm fraction with a low sulfur content (the so-called BOS-quality lime). 

Basic oxygen steelmaking 30 Agriculture, food etc see Table 30.1... 

As described in section 25.2, in many countries the iron and steel industry vies with building and construction as the largest market segment for lime. Most of the lime used is for fluxing impurities in the basic oxygen steelmaking (BOS) process [27.20]. Lime is also used in smaller quantities in ... 

Chromite—Magnesite Inner lining of basic oxygen steelmaking vessels, side walls of soaking pits, etc. 

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