Abstract: Ferritic stainless steel which resists oxidation at high temperature, of use in particular for a catalyst support structure, such as for example structures contained in the exhaust pipes of motor vehicles. This stainless steel comprises by weight:12 to 25% chromium, 4 to 7% aluminium, less than 0.03% carbon, less than 0.02% nitrogen, less than 0.22% nickel, less than 0.002% sulphur,less than 0.6% silicon, less than 0.4% manganese,the active elements selected from the group comprising cerium, lanthanum, neodymium, praseodymium, yttrium taken alone or in combination, at a content of lower than 0.08%, at least one stabilizing element selected from the group comprising zirconium and niobium,the zirconium and/or niobium contents satisfying the following conditions:for the zirconium,(C%/12+N%/14)-0.1.ltoreq.Zr.ltoreq.91 (C%/12+N%/14)+0.1for the niobium,93.times.0.8(C%/12)-0.1.ltoreq.Nb .ltoreq.93.times.0.8(C%/12)+0.15 and Nb<0.3%,for the zirconium and the niobium,91(N%/14)-0.05.ltoreq.Zr .ltoreq.91(N%/14)+0.

Abstract: Resulphurized austenitic stainless steel with improved machinability, characterized in that its weight composition is the following:carbon lower than or equal to 0.15%silicon lower than or equal to 2%manganese lower than or equal to 2%molybdenum lower than or equal to 3%nickel between 7 and 12%chromium between 15 and 25%sulphur between 0.10 and 0.40%calcium higher than or equal to 30.times.10.sup.-4 %oxygen higher than or equal to 70.times.10.sup.-4 %the ratio of the calcium content and of the oxygen content Ca/O being between 0.2 and 0.6.