2. Stainless steels and machinability

2.1 A reminder of the different structures

The different structures of stainless steels have very different machining behaviors. The four main families are: austenitic, ferritic, martensitic and austeno-ferritic.

• Austenitic steels have a face-centered cubic structure and generally contain 18% chromium, 8-10% nickel and 0.02-0.06% carbon. Molybdenum improves their corrosion resistance.

  These steels are hyper-hardened from 1,050 or 1,100°C to avoid precipitation of chromium carbides at grain boundaries.

• Ferritics, with their cubic-centered structure, mainly comprise two families: chromium-rich (25% to 30%) and 17% chromium.

  After...