No abstract

The medium alloy creep resistant steels can be well separated from the high alloy creep resistant steels on the bases of chemical composition and welding technology. These two subgroups should be classified differently, therefore, in welding standards for creep resistant steel grades. In the present work, the general conclusions from a randomly chosen BS 762 steel are valid for the new BS 629 steels, where the martensite start temperatures for charges with upper and lower composition limits can differ by as much as 80 K, resulting in different crack sensitivities within the same specification even at a low carbon content. To achieve minimal and uniform cracking sensitivity, preheating and intermediate cooling temperatures are defined for the high alloy (chromium ≥4 wt-%) creep resistant steels and a reclassification of creep resistant steels in the European standard EN 288–3 is suggested.