Stainless steel is steel which has chromium offered with it. This gives the steel corrosion resistance properties, and these properties allow the steel certain advantages. Plenty of different types of steels, and they are employed for various applications such as sinks or basins and steel cutlery to mention a few.
Steels are graded as stated by their properties. Some is extremely 'hard' and difficult to machine/fabricated (milling & turning etc.) whilst others in a position to relatively 'soft' and reasonably easy to machine. Tough ones will reduce the lifetime of the cutting tool whilst relatively softer steels will machine more easily and the life of the tool will be prolonged.
Duplex stainless steels are very immune to corrosion and furthermore have a high resistance to intergranular corrosion. They exhibit very high resistance even in sulphide and chloride environments, and have a superior resistance to stress corrosion cracking. Super duplex grades exhibit even higher capability corrosion.
Due to appeal of soy content of chromium in them, temperatures of over 300 degrees centigrade will result in embrittlement, however at lower temperatures the steel has better ductility than ferritic and martensitic marks. Duplex grades of stainless steels can be readily used right down to at least -50 degrees centigrade.
When machining or fabricating any types of steels, only tools dedicated to stainless materials should use. Work and tooling surfaces should be clean to avoid any cross contamination by easily corroded metals that may discolour the top of the machined product.
They do not harden if heat treated but it might be work hardened. Annealing (a softening up process) may be performed by rapid cooling after heating to about 1100 degrees centigrade.
Due to the properties of duplex steels machining is normally extremely difficult, but the machining may be enhanced by using the following procedures;
o Dull edges cause work hardening so keep cutting tools sharp
o Light cuts should be taken but deep enough to prevent skimming the surface
o Use adequate amounts of coolants and cutting fluids
Some typical applications for duplex steels can include chemical processing, marine environments, oil and gas refining and pulp and paper manufacturing.