When nickel is added to stainless steel in sufficient amounts the crystal structure changes to "austenite". The basic composition of austenitic stainless steels is 18% chromium and 8% nickel. Austenitic grades are the most commonly used stainless steels accounting for more than 70% of production (type 304 is the most commonly specified grade by far).
Basic properties
- excellent corrosion resistance
- excellent weldability (all processes)
- excellent formability, fabricability and ductility
- excellent cleanability, and hygiene characteristics
- good high and excellent low temperature properties
- non magnetic (if annealed)
- hardenable by cold work only
Common uses
- computer floppy disk shutters (304)
- computer keyboard key springs (301)
- kitchen sinks (304D)
- food processing equipment
- architectural applications
- chemical plant and equipment
Common austenitic stainless steel grades and their applications
Common Name | UNS No | Forms Available* | Typical Compositions (%) | Typical Applications | |||||
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| C | Cr | Ni | Mo | Ti | Other | |
301 | S30100 | Sheet and Coil | 0.05 | 17 | 7.0 | - | - | - | General purpose stainless steel with good corrosion resistance for most applications. Used where the high work-hardening exponent is desirable. Can be supplied cold worked to give high strength. Used for structural applications such as rail carriages and wagons. |
302HQ | S30430 | Wire | 0.02 | 18.0 | 9.0 | - | - | 3.5Cu | Wire for cold heading to produce fasteners etc. |
303 | S30300 | Bars | 0.12 | 18.0 | 9.0 | - | - | 0.25S | Free machining steel used where extensive machining is required. Corrosion resistance and weldability inferior to 304. |
304 | S30400 | Sheet and Coil, Plate and Bars | 0.05 | 18.5 | 8.5 | - | - | - | General purpose stainless steel with good corrosion resistance for most applications. Used for architecture, food processing, domestic sinks and tubs and deep drawing applications. |
304L | S30403 | Sheet and Coil, Plate | 0.025 | 18.5 | 9.0 | - | - | - | Chemical plant and food processing equipment, where freedom from sensitisation is required in plate thicknesses. |
304H | S30409 | Sheet and Coil, Plate, Pipe and Bar | 0.06 | 18.5 | 9.0 | - | - | - | Higher carbon content than 304L, for increased strength, particularly at elevated temperatures. |
310 | S31000 | Sheet and Coil, Plate and Bars | 0.12 | 25.0 | 20.0 | - | - | - | Furnace parts and equipment. Resistant to temperature 900oC to 1100oC. |
310S | S31008 | Sheet, Plate, Bar, Tube and Pipe | 0.08 | 25.0 | 20.0 | - | - | - | A low carbon version of 310 used to resist nitric acid corrosion. |
316 | S31600 | Sheet and Coil, Plate, Seamless and Welded Tube and Pipe | 0.05 | 17.0 | 11.0 | 2.1 | - | - | Used where higher corrosion resistance is required, ie marine equipment. Can be welded up to three millimetres without subsequent heat treatment. |
316L | S31603 | Sheet and Coil, Plate, Seamless and Welded Tube and Pipe | 0.02 | 17.0 | 11.0 | 2.1 | - | - | A low carbon modification of 316 where heavy section weldments are required without the risk of intergranular corrosion. |
316Ti | S31635 | Plate, Pipe and Tube | 0.05 | 17.0 | 11.0 | 2.1 | 0.5 | - | A titanium stabilised version of 316 used where good resistance to intergranular corrosion and high temperature strength is required. |
317L | S31703 | Sheet and Coil, Plate | 0.02 | 19.0 | 13.0 | 3.25 | - | - | For chemical plant - has a greater corrosion resistance than 316 in certain applications, notably in contact with brines and halogen salts. More usually available in the low carbon L grade. |
321 | S32100 | Sheet and Coil, Plate and Bar | 0.06 | 18.0 | 10.0 | - | 0.5 | - | Heavy weldments in chemical and other industries. |
904L | N08904 | Sheet, Plate, Bar, Pipe and Tube | 0.02 | 20.0 | 25.0 | 4.5 | - | 1.5Cu | High resistance to: general corrosion in eg sulphuric and acetic acids, crevice corrosion, stress corrosion cracking, pitting in chloride bearing solutions. Good weldability. |
+ | S31254 | Sheet, Plate, Tube, Pipe, Bar | 0.02 | 20.0 | 18.0 | 6.0 | - | 0.2N | Used where high resistance to chloride pitting and crevice corrosion is required, eg seawater heat exchangers, bleach vats and washers in the pulp and paper industry. |
+ | S30815 | Sheet, Plate, Bar, Tube and Pipe | 0.10 | 21.0 | 11.0 | - | - | 0.15N 0.04Ce | Used for furnace parts, radiant shields, fluidised beds. Resistant to temperatures up to 1150oC. Possesses high strength and resistance to sigma phase formation. |
* Compatible or equivalent grades also available in castings. | |||||||||