Casting and Drawing Lubrication

A South African Standard specifies the qualities of lime for metallurgical purposes [32.14]. 

The HogenSs process is widely used for the production of reduced metal powders [32.24]. In the production of iron powder, for example, pure magnetite ores are comminuted, screened and purified using magnetic separators. They are then mixed with a blend of coke and quicklime, and heated in a silicon carbide lined retort at 1050 to 1200 °C for 24 to 40 hours. The iron oxide is reduced by the coke to iron and the quicklime reacts with sulfur, silica and alumina in the ore and coke, forming a slag. 

The reaction product is a strongly sintered sponge, which includes the slag. The sponge is ground into a powder, screened and non-metallic inclusions are removed using magnetic separation. 

High-calcium quicklime is used with a similar chemical requirement to those for steelmaking (see section 27.4.2). As in steelmaking, the required particle size depends on the method of addition/injection of the quicklime. 

This section refers to the use of quicklime as a component of continuous casting lubricants and of slaked lime as a lubricant carrier in wire drawing (the use of lime in greases and calcium soaps is described in section 31.13). 

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