The effect of residuals on the elevated temperature properties of some creep resistant steels

The effect of residuals and other deliberate minor additions on the elevated temperature properties of austenitic, CrMo and CrMoV steels is reviewed and those that affect these properties are identified. The elements boron, molybdenum, nitrogen and phosphorus in austenitic steels all increased creep rupture life although only boron and molybdenum were beneficial to rupture ductility. In the ferritic steels the embrittling elements antimony, arsenic, phosphorus and tin were considered together with aluminium, copper, silicon, titanium and boron. It is apparent that the effect of an individual element on creep rupture properties is dependent on the other elements present. However, in a 1 %CrMoVTiB steel additions of copper plus nickel and arsenic plus tin decrease rupture life although only the latter two reduce ductility. Similarly, in a 2 1/4% Cr1% Mo steel arsenic has a detrimental effect on ductility and tin and phosphorus have been identified as segregating to prior austenite grain boundaries. In contrast, silicon in a 2 1/4%Cr1 %Mo steel can improve ductility. Aluminium can improve both the creep life and ductility of 1 %CrMoVTiB steels, as can boron in the presence of titanium.