Development of low alloy ultrahigh strength steel

Thermomechanical treatment (TMT) of plates is used to obtain the optimum combination of strength and toughness. Although this technique is applied to high strength low alloy (HSLA) steels, its application to ultrahigh strength steel (UHSS) is still under study. In this investigation, four C, Mn, Cr and Mo alloys, some with Nb or Ti additions, were prepared by electroslag refining (ESR), hot rolling with TMT and variations in cooling rate. Mechanical properties were evaluated and microstructural features were characterised. The oil cooled specimens of titanium alloy produced the optimum properties with higher strength values: ultimate tensile strength (UTS) = 52177 MPa, yield strength (YS) = 51795 MPa, elongation (El) = 58% and impact toughness = 713 kJ m(-2), with microstructures predominantly consisting of lath martensite.