Influence of rare earth metals on inclusion modification of dual phase steel: Influence des métaux de terres rares sur la modification des inclusions de l'acier biphasé

Abstract

Inclusions are very critical in advanced high-strength steels as they are used in automobile and aerospace industries in which modification of inclusions is required. In this investigation, Rare Earth Metals (REM) have been used to control and modify the inclusions in the steel. With the addition of REMs, the total sulphur content present in the steel has been reduced by 22%. An inclusion study has been performed using the inclusion classifier and ISO-4967 method. Total inclusions and the number of inclusions at higher indexes (severity) are reduced by adding REM. The chemistry of the modified inclusions, such as oxides, sulphides and oxysulphides of REM, is compatible with the steel matrix and does not have harmful effects. With the addition of REM, the global cleanliness index value at 1.5, 2, 2.5 and 3 indexes are decreased. This may be attributed to the REM breaking down the stringers. Whereas value has been increased at 0.5 and 1 indexes after the addition of RE metals, inclusions sizes are reduced, which is not harmful to the properties of the steel.