Use of an austenitic steel comprising (in wt.%): carbon (0.01-0.4); silicon (0.1-8); manganese (0.1-25); chromium (0.1-25); nickel (less than 13); molybdenum (less than 4); nitrogen (less than 0.5); aluminum (0-15); copper (0-10); niobium (0-4); vanadium (...