2. Stainless steel structure

Stainless steels are iron-based or, more precisely, steel-based metal alloys (iron-carbon alloys) that must contain at least 10.5% chromium (according to European standard EN 10088-1) and often other additives such as nickel (or its substitute manganese) and, to a lesser extent, molybdenum.

Before examining the various equilibrium diagrams, it is useful to recall the allotropic varieties of iron. At low temperatures and up to 910 C, iron has a face-centered cubic structure, this is α-iron. From 910°C onwards, it transforms into γ iron, which has a face-centered cubic structure, and a further transformation takes place at 1400°C to give δ iron, which has a face-centered cubic structure. These reversible transformations can be summarized as shown in table 3 .

Thus, chromium (face-centered...