Stainless Steel

The corrosion resistance of steels is due to the element Chromium which is added to the steel during steel production. A minimum of 13% Chromium is required to form an inert, corrosion resistant, surface layer, which protects not only against corrosion but also against high temperature oxidation. The corrosion resistance increases with higher Chromium concentration, but so does the price. Carbon has a detrimental effect on the corrosion resistance. Steels which also contain aluminium are even more suitable for oxidation resistance at high temperatures. Stainless steels containing Molybdenum are required to offer protection against corrosion in sea water and during cooking. Three classes of stainless steels are distinguished: - the ferritic grades, containing only C and Cr as alloying elements. These steels are relatively cheap but have a moderate formability. They are weldable. - the martensitic grades, containing more than 0.1% C and Cr, have somewhat higher mechanical properties. They are not weldable. - the austenitic grades, containing also approximately 10% Ni. These steels have excellent corrosion resistance, good formability and are weldable. They are non-magnetic. Steel codes: XaaCrNi : aa = Carbon % x 100, bb = Cr%, cc = Ni%. (References DIN 1.4002, AISI 405). Can be quenched from high temperatures without any hardening occurring. Ductile and easy machinable.