Manganese is also an essential element in all carbon, low-alloy, and alloy steels. Manganese has several roles as an alloying element. One role is to assure that all residual sulfur is combined to form manganese sulfide (MnS). Manganese is generally added to steel with a minimum manganese–sulfur ratio of 20 1. Without manganese the sulfur would combine with iron and form iron sulfide (FeS), which is a brittle compound that lowers toughness and ductility and causes a phenomenon called hot shortness. Hot shortness is a condition where a compound (such as FeS) or insoluble element (such as copper) in steel has a low
melting point and thus forms an unacceptable cracklike surface condition during hot rolling.

Another role of manganese is in strengthening steel. Manganese is a substitutional element and can replace iron atoms in the bcc or fcc lattice. Each 0.1% Mn added to iron will increase the yield strength by about 3 MPa. Manganese also lowers the eutectoid transformation temperature and lowers the eutectoid carbon content. In large amounts (12% or higher), manganese is an austenite stabilizer in alloy steels and forms a special class of steels called austenitic manganese steels (also called Hadfield manganese steels). These steels are used in applications requiring excellent wear resistance, e.g., in rock crushers and in railway track connections where two rails meet or cross.

Bruce L. Bramfitt
International Steel Group, Inc.
Research Laboratories
Bethlehem, Pennsylvania

Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright  2006 by John Wiley & Sons, Inc.

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