Stainless steels got their name when they were initially used in the manufacture of cutlery - literally, they would not stain. It is better to consider stainless steels as metals that are particularly resistant to corrosion.
These kinds of metals are iron alloys that contain a minimum of 10.5% Chromium. This element forms a self-healing very tight transparent layer over a steel surface and protects it from corrosion by stopping further oxidation. In addition to this alloying element, others are added to change the structure of the metal and give it different properties, for example,
- Abrasion Resistance
- Corrosion Resistance
- Oxidation Resistance at High Temperatures
- Strength and Ductility at Cryogenic Temperatures
- Strength at Elevated Temperatures
Commonly metal and non-metal elements are added to impart various properties:
- Aluminium - improves scaling resistance.
- Carbon - increases strength, but can reduce corrosion resistance.
- Chromium - forms a self-healing transparent film to protect against corrosion.
- Colombium - combines with Carbon to reduce intergranular corrosion.
- Copper - increases resistance to certain corrosive environments.
- Manganese - improves hot working properties and promotes austenite stability.
- Molybdenum - increases corrosion resistance and strength at high temperatures and useful in chloride environments.
- Nickel - increases ductility, high temperature strength and corrosion resistance, especially in marine environments.
- Silicon - increases scaling resistance and imparts carburizing resistance.
- Titanium - combines with Carbon to reduce intergranular corrosion.
The following are chemical composition tables for Stainless Steels. Please note that these are not standards but grade composition ranges only.
All information is given purely for reference purposes