Propriedades mecânicas

Propriedades Mecânicas

A martensita revenida pode ser quase tão dura e resistente quanto a martensita,porém com ductilidade e tenacidade aprimoradas

A dureza e resistência são explicadas pelogrande número de contornos entre asfases ferrita e cementita devido àsnumerosas e finas partículas de cementita

A fase cementita, dura, reforça a matriz deferrita ao longo dos contornos e atuamcomo barreiras de discordâncias durante adeformação plástica

A fase ferrita, é muito dúctil e relativamente tenaz, o que responde pela melhoria da ductilidade e tenacidade na martensita revenida

In addition to their effect on hardenability, some of the alloying elements also have a significant effect on the temper resistance of the steels. This allows combinations of high strength, high ductility and toughness to be generated in section sizes much larger than can be done with plain carbon steels.

The rank order of the effects of the alloying elements on temper resistance in decreasing the order, is as follows:

Vanadium

Molybdenum

Manganese

Chromium

Silicon

Nickel

V, Cr and Mo form complex carbides, the composition of which changes with tempering time and temperature, with the relative proportions of the presence of each of them in the steel. At levels above 1%, Mo induces a secondary hardening effect as shown in the diagram.

It is also beneficial in reducing the risk of temper embrittlement, which is caused by the segregation of elements such as phosphorus to the grain boundaries. These three elements also are the basis of creep resistant steels. These are designed for service at high temperatures, for example, above 500 °C, for example, in power generation plant.