Rosenhain Centenary Conference - 3. Materials development present and future 3.7. Recent developments in ultra high strength steels and their applications

As far as the development of new classes of ultra high strength steels is concerned the past decade has seen little progress apart from a few notable exceptions such as the trip steels. However, the introduction of fracture mechanics concepts to the evaluation of material properties has been responsible for an enormous breakthrough in the understanding of the factors which influence the fracture processes in conventional high strength steels. This approach has concerned not only the resistance of these materials to unstable fracture under rising load but also the stable crack propagation which can occur in aggressive environments under static load and in both aggressive and inert environments under cyclic loading conditions. Utilization of fracture mechanics has demonstrated the improvement which can be obtained in the properties of high strength steels through the use of thermomechanical treatments, hardening by intermetallic compounds and control of inclusions. Though much still remains to be learned in each of these fields, this paper highlights some aspects of the progress which has been made in the understanding of the fracture, fatigue and stress corrosion cracking of high strength steels.