These alloys can be added as 'lump additions', but more commonly are injected into the steel. The choice of addition is highly dependant on the steel type being made, its processing conditions and final application. They also reduce cutting temperatures and tool wear. The lead forms discrete particles in the steel structure on solidification, often present as tails on manganese sulphide inclusions.
Tellurium is very toxic and therefore requires strict precautions to be taken during steelmaking.
It is present as manganese telluride in the solid product and has a similar effect to lead. It also acts to modify the shape of manganese sulphide inclusions from an elongated to globular morphology . It has a similar effect to lead but it is a considerably more expensive addition. Treatment of hard, angular, abrasive alumina inclusions in aluminium deoxidised steels, gives calcium aluminate inclusions which are softer and globular at rolling temperatures, thereby improving the material's processing characteristics. Some inclusions found in steel have a tendency to block the nozzles in continuous casting machines, resulting in casting being terminated prematurely, lost output and increased costs.