Secondary Steelmaking Processes

Where pneumatic injection systems are used, finer grades (e.g., 2 to 6 mm) are specified to suit the characteristics of the system [27.5]. 

Secondary steelmaking is used to bring the steels produced by the BOF and the EAF into specification. In many works it acts as a physical and chemical buffer between the primary steelmaking processes and the continuous caster. It has been the main growth area in steelmaking since the early 1980s as a result of  

Particularly as a result of (b), the roles of the primary steelmaking processes have changed, with the BOF being used mainly for the removal of carbon from pig iron, and the EAF being used mainly to melt steel scrap. This places increased emphasis on refining the hot metal either before the primary steelmaking operation (i.e., treatment of pig iron — see section 27.3), or after it (i.e., secondary steelmaking). 

The processes used in secondary steelmaking are many and varied [27.2, 27.8, 27.22]. For the purposes of this section, they can be divided into five types of operations [27.5]  

Many of the processes combine two or more of the above operations. 

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Direct-bonded magnesia-chrome ore materials exhibit a high strength at high temperatures, superior resistance to slags and volume stability up to 1800 C. They also show a much lower tendency to expansion and subsequent spalling as a result of interaction with iron oxides (cf. the follow ing section on chromite materials). Direct--bonded ware finds application in open-hearth furnaces, in electric arc furnaces, in secondary steelmaking processes, in rotary cement kilns, etc. 

Steels with the lowest sulfur specifications (of less than 0.001 %, or 10 mg/kg) are generally produced by a combination of a pig iron desulfurisation stage, combined with efficient desulfurisation in the BOS and secondary steelmaking processes. 

Vacuum Degassing. A secondary STEELMAKING PROCESS in which the bath of molten steel in the ladle, or the stream of molten steel from it, is exposed to a vacuum to accelerate the removal of hydrogen from the steel. Vacuum Drying. Reducing the air pressure over ware being dried speeds up moisture removal. 

Increasingly today, steels after they have been tapped (poured) from the furnace undergo a further stage of processing called secondary steelmaking before the steel is cast. This applies to both the basic oxygen process route and to the electric arc furnace route. 

Electric furnaces, 12 286-318 76 144, 145. See also Electric arc furnace (EAF) Fuel-fired furnaces applications for, 12 315-316 arc furnaces, 12 297-306 classification of, 12 286 economic aspects of, 12 313-314 health and safety factors related to, 12 314 induction furnaces, 12 307-313 in phosphorus manufacture, 19 8-11 resistance furnaces, 12 287-297 for secondary slags, 14 759-760 Electric furnace steelmaking processes,... 

Slags play an important role in secondary steelmaking and, as the objectives of the several processes vary, so do the compositions of the slags used [27.5,27.19]. 

Addition rates of quicklime vary widely. The AOD process uses about 90 kg/t steel, whereas other processes use as little as Ikg/t. The average total use in secondary steelmaking is in the range 5 to 15 kg/t [27.5]. 

Secondary Emissions from Basic Oxygen Process Steelmaking Facilities for Which Construction Commenced after January 20, 1983 Sewage Treatment Plants Primary Copper Smelters Primary Zinc Smelters... 

Steelmaking is a sophisticated and complex process, with many secondary production operations, each having unique air pollution problems to varying degrees. Figures 10, 11, and 12 provide some examples of common air pollution problems. 

Standards of Performance for Secondary Emissions From Basic Oxygen Process Steelmaking Facilities for Which Construction Is Commenced After January 20, 1983 Standards of Performance for Sewage Treatment Plants Standards of Performance for Primary Copper Smelters Standards of Performance for Primary Zinc Smelters Standards of Performance for Primary Lead Smelters Standards of Performance for Primary Aluminum Reduction Plants... 

You may have heard of Coras - it s the largest steelmaker in the UK. I work for a company that is half owned by them called SMS Mevac. We are internationally active in plant construction and mechanical engineering relating to the processing of steel, non-ferrous metals and plastics. We are specialists in secondary metallurgy. 

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