INCONSISTENCY OF CLASSIFICATION OF CREEP-RESISTANT STEELS IN EUROPEANSTANDARD EN-288-3

The medium alloy creep resistant steels can be well separated from the high alloy creep resistant steels on the bases of chemical compositio n and welding technology. These two subgroups should be classified dif ferently, therefore, in welding standards for creep resistant steel gr ades. In the present work, the general conclusions from a randomly cho se BS 762 steel are valid for the new BS 629 steels, where the martens ite start temperatures for charges with upper and lower composition li mits can differ by as much as 80 K, resulting in different crack sensi tivities within the same specification even at a low carbon content. T o achieve minimal and uniform cracking sensitivity, preheating and int ermediate cooling temperatures are defined for the high alloy (chromiu m greater than or equal to 4 wt-%) creep resistant steels and a reclas sification of creep resistant steels in the European standard EN 288-3 is suggested. (C) 1997 The Institute of Materials.