MAJOR CLASSIFICATIONS OF STAINLESS STEEL
Stainless steel is divided in major 8 series which are mention in below chart along-with their respective classes and type of Alloy-
| Stainless Steel series | Classes | Alloy Type |
| 100 | Austenitic | Chromium-Nickel-Manganese alloys |
| 200 | Austenitic | Chromium-Nickel-Manganese alloys |
| 300 | Austenitic | Chromium-Nickel alloys |
| 400 | Ferritic & Martensitic | Chromium alloys |
| 500 | Heat resisting chromium alloys | Chromium alloys |
| 600 | Martensitic (Precipitation hardening alloys ) | Chromium-Nickel-Copper alloys |
| 900 | Austenitic | Chromium-Nickel-Molybdenum alloys |
| 2205, 2304, 2507 | Ferritic/ Austenitic (Duplex Stainless steel ) | Chromium-Nickel-Molybdenum-Manganese alloys |
DETAILS OF 5 CLASSES OF STAINLESS STEEL
Details of properties like magnetism, crystal structure along-with series of all classes of stainless steel are as follows-
| Classes | Magnetism | Crystal structure | Common examples |
| Ferritic | Magnetic | BCC | 405,430,442 |
| Austenitic | Non magnetic | FCC | 201,301,302,303,304,316 |
| Martensitic | Magnetic | BCT | 403,410,416 |
| Duplex | Magnetic | Combination | 2205,alloy255 |
| Precipitate-Hardened | Magnetic | Combination | 17-4PH,17-7PH |
FEATURES
Special features of class of stainless steel are as follows-
| Austenitic | Ferritic | Duplex | Martensitic | P-H |
| *Easily welded *High ductility *Good corrosion resistance *Suitable for high temperatures to e.g. 310 to 1100°C *Suitable for low temperatures including cryogenic applications. *Is non-magnetic | *Less expensive *Lower corrosion resistance *Can be welded, but requires more care *Easily formed [bent, cut, etc.] *Moderate high temperature [up to 800°C for 430] *Slight increases in strength by cold working [up to 50%] *Superior resistance to stress corrosion cracking *Is magnetic | *High resistance to stress corrosion cracking *Increased level of passivity *Good welding and formability *Higher tensile and yield strengths than austenitic and Ferritic grades . | *High mechanical strength combined with corrosion resistance is required e.g. knives | *Can be heat treated to provide tensile strengths of 850MPa to 1700MPa and yield strengths of 520MPA to over 1500MPa – some three or four times that of an austenitic stainless steel such as type 304 or type 316. |
PROPERTIES OF SOME POPULAR STAINLESS STEEL GRADES
Properties like structure, welding properties, machining properties, cold pressing properties and maximum service temperature of popular grades of stainless steel are as follows-
| S.I STAINLESS GRADE | STRUCTURE | WELDING PROPERTIES | MACHINING PROPERTIES | COLD PRESSING PROPERTIES | MAXIMUM SERVICE TEMP |
| 302 | Austenitic | Good | Fair | Good | 800°C |
| 303 | Austenitic | Fair | Excellent | Fair | 800°C |
| 304L | Austenitic | Good | Fair | Excellent | 800°C |
| 304 | Austenitic | Good | Fair | Very Good | 800°C |
| 310 | Austenitic | Good | Fair | Good | 1100°C |
| 316L | Austenitic | Good | Fair | Good | 800°C |
| 316 | Austenitic | Good | Fair | Good | 800°C |
| 317L | Austenitic | Good | Fair | Good | 800°C |
| 317 | Austenitic | Good | Fair | Good | 800°C |
| 321 | Austenitic | Excellent | Fair | Good | 800°C |
| 410 | Martensitic | Poor – Welds Brittle | Good | Fair | 750°C |
| 420 | Martensitic | Generally Not Recommended | Good | Poor | 750°C |
| 430 | Ferritic | Fair – Welds Brittle | Good | Fair | 800°C |
| 432 | Martensitic | Not Recommended | Good | Poor | 650°C |
