The information below is for guidance only and should not be used when working to stringent specifications.
| BS970 | 416 S21 Per cent | 431 S29 Per cent | 310 S24 Per cent |
304 S15 Per cent |
303 S21 Per cent | 321 S12 Per cent | 316 S31 Per cent | 430 S15 Per cent | ||||||||
| min. | max. | min. | max. | min. | max. | min. | max. | min. | max. | min. | max. | min. | max. | min. | max. | |
| Carbon | 0.09 | 0.15 | 0.12 | 0.20 | – | 0.15 | 0.06 | – | 0.12 | – | 0.08 | – | 0.07 | – | 0.10 | |
| Silicon | – | 1.00 | – | 0.80 | 0.20 | 1.00 | 0.20 | 1.00 | 0.20 | 1.00 | 0.20 | 1.00 | – | 1.00 | – | 0.80 |
| Manganese | – | 1.50 | – | 1 .00 | 0.50 | 2.00 | 0.50 | 2.00 | 1.00 | 2.00 | 0.50 | 2.00 | – | 2.00 | 1.00 | 2.00 |
| Nickel | – | 1.00 | 2.00 | 3.00 | 19.00 | 22.00 | 8.00 | 11.00 | 8.00 | 1 1.00 | *9.00 | 12.00 | 10.50 | 13.50 | – | 0.50 |
| Chromium | 11.50 | 13.50 | 15.00 | 18.00 | 23.00 | 26.00 | 17.50 | 19.00 | 17.00 | 19.00 | *17.00 | 19.00 | 16.50 | 18.50 | 16.00 | 18.00 |
| Sulphur | 0.15 | 0.30 | – | 0.03 | – | 0.03 | – | 0.03 | 0.15 | 0.30 | – | 0.03 | – | 0.03 | 0.03 | |
| Phosphorus | – | 0.04 | – | 0.04 | – | 0.045 | – | 0.045 | – | 0.045 | – | 0.045 | – | 0.045 | – | 0.04 |
| Molydbenum | – | 0.60 | – | – | – | – | – | – | 0.70 | – | – | 2.00 | 2.50 | – | – | |
| Titanium | – | – | – | – | – | – | Unstabilised | Unstabilised | + | 0.70 | s | |||||
| Martensitic | Martensitic | Austenitic | Austenitic | Austenitic | Austenitic | Austenitic | Ferritic | |||||||||
Stainless Steel
*, The sum of the Nickel and Chromium content shall not be less than 25.00%.
+, Not less than four times
S, These elements may be present the Carbon content. at the o tion of the manufacturer.
CORROSION AND OXIDATION CHARACTERISTICS
416 S21 formerly EN 56AM
More often referred to as a stainless iron and not a stainless steel. Owing to its low corrosion resistance is not recommended for atmospheric exposure unless it is able to be cleaned regularly. Has a good resistance to nitric acid attack but is inferior to austenitic stainless steels. Magnetic.
431 S29 formerly EN 57
This specification has a greater corrosion resistance and tensile strength over 416 S21 and because of this, is widely used in the aircraft industry. It also has a good wear resistance surface due to the martensitic formation of the structure when it has been quench cooled after heat treatment. This often lends itself to such applications as spindles, pivot pins and roller bearings, etc. Magnetic.
430 S15
Fairly good resistance to outdoor corrosion if cleaned regularly. Can also be used with some weak acids and foodstuffs; good oxidation resistance up to 800QC. It is quite often used in the food processing industry in sheet form and a limited range of fasteners con also be supplied. Magnetic.
304 S15 formerly EN 58E A2-18/8
Except in severe industrial and marine conditions this specification has resistance up to 850QC (particularly when stabilised with Titanium) and its ability to resist organic acids is satisfactory under certain conditions. It is not recommended for use with acids such as hydrochloric and chlorides and is non-magnetic except when heavily cold worked. Although not harden-able by heat treatment, the cold working greatly strengthens the product.
303 S21 formerly EN 58AM
This specification is basically a free machining stainless steel resulting from the addition of sulphur to 302 S25. Although the faster machining speeds are appreciated by engineers, some free machining grades may have lower corrosion resistance than other types. Non-magnetic.
321 S12 formerly EN 58B
A “weld decay” proof austenitic steel containing Titanium. It is intended for all types of welded plant and equipment employed in the manufacture and processing of chemicals and foodstuffs. Also widely used in aircraft construction, petrochemical, hydraulic and mechanical engineering. Non-magnetic unless heavily cold worked.
316 S31 A4-18/10
This specification has greater corrosion resistance than 304 S15 in certain environments and is often used in Marine applications. The material is hardened during the cold working process. Non-magnetic except when heavily cold worked.
310 S24
The feature of this austenitic chromium nickel steel is a higher alloy content than normal. This factor improves the “creep” strength and appreciably raises the resistance of the steel to oxidation. It is recommended for use at temperatures to approx. 1000 deg. C and is commonly used in high temperature furnace equipment. Special fasteners can be manufactured to this specification.
