Stainless Steel 303
Stainless steel 303 Stockists
303 stainless steel is a chromium-nickel austenitic stainless steel known for its excellent machinability, good strength, and corrosion resistance. It is typically supplied in an annealed condition with a Brinell hardness of around 190.
This steel is prized for its superior machinability and resistance to galling, largely due to its higher sulphur content. While this sulphur addition slightly reduces corrosion resistance, 303 still offers sufficient resistance to general atmospheric conditions, food processing environments, sterilizing solutions, dyes, and most organic and some inorganic chemicals. However, its resistance to acids is somewhat limited.
303 stainless steel cannot be hardened through heat treatment, but its strength and hardness can be significantly increased through cold working, which may reduce its ductility.
303 is most commonly used in applications that require extensive machining or complex parts that benefit from excellent machinability. Typical uses include architectural components, food processing equipment, dairy machinery, dyeing industry tools, hardware, and kitchenware. It is often used to manufacture bolts, nuts, bushes, gears, shafts, valve bodies, and fittings.
When in the annealed condition, 303 is non-magnetic, but can become slightly magnetic after extensive cold working. If necessary, annealing can restore its non-magnetic properties.
| Related Specifications | |
| Australia | AS 2837-1986-303 |
| Germany | W.Nr 1.4305 X10CrNiS 18 9 |
| Great Britain | BS970 Part3 1991 303S31 BS970 1955 EN58M |
| Japan | JIS G4303 SuS 303 |
| USA | ASTM A582/582M-95b 303 SAE 30303 AISI 303 UNS S30300 |
Chemical Composition of 303 Stainless Steel
| Chemical Composition | ||
| Min. % | Max % | |
| Carbon | 0 | 0.15 |
| Silicon | 0 | 1.00 |
| Manganese | 0 | 2.00 |
| Nickel | 8.00 | 10.00 |
| Chromium | 17.00 | 19.00 |
| *Molybdenum | 0 | 1.00 |
| Phosphorous | 0 | 0.06 |
| Sulphur | 0.15 | 0.35 |
| *Molybdenum option addition. |
Temperature Properties of Stainless Steel 303
| Typical Mechanical Properties At Room Temperature - Annealed | |||
| Finish | Cold Drawn | Other | |
| Tensile Strength Mpa | 720 | 600 | |
| Yield Strength Mpa | 510 | 240 | |
| Elongation in 50mm % | 36 | 55 | |
| Impact Charpy V J | 120 | ||
| Hardness | HB | 220 | 165 |
| Rc | 165 |
| Elevated Temperature Properties |
| 303 displays good oxidation resistance in continuous service up to 870 oC and in intermittent service up to 760 oC.
Continuous service however, between 430 oC and 850 oC is not recommended, nor is slow cooling through this range due to the problem of intergranular corrosion. N.B. High temperature use is therefore not generally recommended. |
| Cold Bending |
| 303 has very limited cold bending properties and it is not generally recommended. |
| Hot Blending |
| Hot bending should be performed at 950 oC - 1100 oC, followed by annealing to restore optimum corrosion resistance. |
| Corrosion Resistance - All Corrosion Types |
| Because of its increased sulphur content, 303 is less resistant to all forms of corrosion than 304 and all other austenitic stainless steels in the 300 family.
Because of this, it is typically chosen due to its superior machinability and less corrosion resistance. N.B. To guarantee that a chrome oxide coating is constantly present to protect stainless steel, it is crucial that oxygen be able to flow freely over all of its surfaces. If not, corrosion will happen just like it does with other non-stainless steel varieties. Surfaces need to be clear of foreign particles and scale for maximum resistance to corrosive agents. It is necessary to passivate finished components. |
| Forging |
| Heat uniformly to 1150 oC - 1200 oC, hold until temperature is uniform throughout the section.
Do not forge below 900 oC Finished forgings should be air cooled. Finally forgings will require to be annealed in order to obtain optimum corrosion resistance. N.B. Severe upset forging of this grade is not recommended. |
303 Stainless Steel Heat Treatment |
| Annealing |
| Heat to 1050 oC - 1100 oC, hold until temperature is uniform throughout the section. *Soak as required. Quench in water to obtain optimum corrosion resistance.
*Actual soaking time should be long enough to ensure that the part is heated thoroughly throughout its section to the required temperature, 30 minutes per 25 mm of section may be used as a guide. Please consult your heat treater for best results. |
Machining 303 Stainless Steel |
| 303 was developed as a free machining grade and has by far the best machinability of all the 300 series austenitic stainless steels, and indeed has better machinability than most of the 400 series martensitic stainless steels with the exception of the free machining grades. It has a typical machinability rating of about 75% - 80% of free machining (S1214) mild steel.
It has, however, as with all austenitic stainless grades, a high work hardening rate and cutting or drilling tools etc. must be kept sharp at all times and not cause unnecessary work hardening of the surface. All machining should be carried out as per machine manufacturer's recommendations for suitable tool type, feeds and speeds. |
Welding
| Welding |
| 303 is not generally recommended for welding due to its high sulphur content which can cause hot cracking.
However if unavoidable, the following procedures may be taken as a guide. |
| Welding Procedure |
| Welding electrodes or rods should be 308 or *similar depending upon the application.
No pre-heat or post heat is generally required. Post weld annealing will be required to restore corrosion resistance.*Please consult your welding consumables supplier. |