Évolutions structurales d’aciers faiblement alliés au Ni − Cr − Mo au cours de chauffages et de refroidissements effectués à différentes vitesses

Mechanisms controlling the structural evolutions of Ni − Cr − Mo low alloy steels during thermal cycles performed whith different rates : part II

¹ Laboratoire de Métallurgie structurale, UA CNRS 04 1107, Université Paris-Sud, Centre d'Orsay, Orsay, France
² Laboratoire de Structure des Matériaux Métalliques, Université Paris-Sud, Centre d'Orsay, Orsay,France

Abstract

First, the behaviour of the 40 NSCD 7-7-3 low alloy steel (AIS/300M) was studied during coolings carried out at various rates from different austenitizing temperatures. The resulting CCT diagrams were drawn and the different microstructures were characterized. Secondly, in order to specify the influence of silicon on the structural transformations occurring during coolings on the 40 NSCD 7-7-3 steel, a 40 NCD steel (with only 0.33 wt% Si, instead of 1.72 wt%) was investigated. Finally, the TTT diagram was drawn in the case of the 40 NSCD 7-7-3. Dilatometric experiments, hardness measurements and transmission electron microscope observations were mainly performed.