Microstructural and magnetic studies on thermomechanically treated hsla steel

Thermomechanical treatment of commercial grade HSLA steel microalloyed with Nb, V and Ti has been carried out in order to obtain microstructures with spherodised carbides evenly distributed thourghout the matrix and therefore with good magnetic properties at high strength levels. Alloys were tempered after rolling-quenching, as well as forging-quenching. In both cases, rolled as well as forged, good magnetic properties were obtained at a strength of 600-620 MPa after spheroidisation of carbides. Thus, for a given level of carbon, the spheroidised carbides lead to a lower coercive force compared to the case in which they are lamellar. This is believed to be associated with lower locked-up microstresses in the former situation.