They are three numbering systems for the same material. UNS is the American five-character scheme, DIN or Werkstoff is the German number, and GB is the Chinese designation. A drawing may name any one of them, and the chemistry windows are not always identical.
How each system is built
UNS is a five-character code: a letter for the family, then four digits. N is nickel, S is stainless, R is heat-resisting. So 718 becomes N07718 and 316L becomes S31603. The number is an identifier, not a specification — the actual requirements live in the ASTM or ASME product standard that cites it.
DIN or Werkstoff numbers are six digits after the 2. prefix for steels and alloys: 2.4668 for 718, 2.4856 for 625, 2.4671 for 713C. European buyers often quote these because they appear on EN drawings.
GB designations are the Chinese scheme, and for the wrought superalloys they usually take the GH prefix: GH4169 for 718, GH3625 for 625, GH3128 for Hastelloy X. Cast grades use K or J prefixes instead.
The part people get wrong
These are not exact equivalents, they are correspondences. Two national standards can specify different ranges for the same element, different minimum mechanical properties, or different permitted tolerances, while all three carrying the same familiar grade name.
The consequence is real: material conforming to one system may fail a certificate check against another. When a drawing cites a standard, the standard governs — the cross-reference only tells you which family to look in.
What to do with a drawing from another country
Send the standard number, not just the grade name. If the drawing says GH4169, we supply against that; if it says N07718, we supply against the ASTM product standard that cites it; if it says only 'Inconel 718', the first question back is which specification applies.
Our cross-reference table lists every grade with all three designations side by side, and each grade page carries its own standards table broken down by product form.