Lead is suitable as an alloying element if it is added in the maximum quantity of 0.5%. At this content, lead improves machinability and is mainly used for free-cutting steels. The addition of lead increases process reliability and forms shorter chips. The quality of the cut surfaces is improved as a result.
Despite the low Mohs hardness of 1.5 and the low melting point of around 328°C, lead does not affect other mechanical properties of steel.
Directive on the prohibition of the use of lead, mercury, cadmium and hexavalent chromium
In 2005, the use of the above elements was re-evaluated due to their hazardous effect on health.
In the process, the use of lead as an alloying element in the EU was also severely restricted and limited to 0.1 percent by weight. There are only a few exceptions where the limit value may be exceeded. These materials are excluded from the ban as long as a higher lead content is unavoidable. In the meantime, intensive material research has led to a progress in the production of lead-free steels, which still provide very good machining properties.
In the form in which it is supplied, steel alloyed with lead does not pose a health risk, as the element is firmly bound in the steel and cannot be inhaled, swallowed or absorbed through the skin. Suitable protective measures must be taken during processing to prevent health hazards.
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