Specifications of Stainless Steel

Grade compositions, mechanical properties and production specifications are governed by a range of international and national standards for stainless steel. While the old AISI three digit stainless steel numbering system (e.g. 304 and 316) is still commonly used for the classification of stainless steel grades, new classification systems have been developed.

These systems include a 1-letter + 5-digit UNS number, like S30400, as defined by SAE and ASTM. European countries are adopting unified Euronorm standards. These countries are either replacing or adapting their own country specific standards to mirror the Euronorm standards. Other designations being replaced include old BS and EN numbers like 304S31 and 58E.

Some grades are not covered by standard numbers and could be proprietary grades or be named using standards for specialist products like welding wire.

Stainless steel standards are explained in detail in the British Stainless Steel Association “Guide to Stainless Steel Specifications”, also known as the BSSA “Blue Guide”.

The table lists a range of stainless steel grades, their old BS designation, new UNS number and new EN designation.

 Stainless steel grades and their international equivalents

 ASTM does not recognise the designations in brackets. Many other grades and specifications are available.

 Material supplied by Bestar Steel has been manufactured to comply with a number of standards depending upon the product. Standards also cover the finish of the material.