Cutlery stainless steel grades '18/8', '18/10' and '18/0'
Compositions of '18/8', '18/10' and 18/0'
These figures relate to the chromium and nickel contents of the steel, respectively.
'18/8' is probably the most commonly used stainless steel and contains 18% chromium and 8% nickel.
This steel is also known as '304' (in the American AISI grade designation system) or 1.4301 in the European BS EN 10088 standard.
It is an 'austenitic' type of stainless steel and so is not (or only very weakly) attracted by a magnet.
'18/10' is a designation used on some cutlery and holloware as an alternative to '18/8'. This designation is claimed to indicate a better quality steel than '18/8', and is essentially the same as the '304 (1.4301) grade . In practice the "10" does not indicate an actual higher Ni content and is purely a marketing ploy.
'18/0' is a 'ferritic' stainless steel type, which is attracted by a magnet (like pure iron). This steel is known as '430' in the AISI system or 1.4016 in the European standard.
It is used where corrosion resistance is not too demanding as an alternative to the '18/8' 304 type. The chromium content is optimistically said to be 18% but is nearer 17%.
Applications for these grades
The austenitic and ferritic '18/8', '18/10' and '18/0' stainless steels cannot be hardened by heat treatment and so can only be used for knife handles, forks and spoons.
Hardenable martensitic types of stainless steel, like the ferritics, contain only chromium, but with additional carbon. This enables them to respond to hardening heat treatments and so they can be used for knife blades.
The best quality table knives are made in two pieces using a martensitic blade and an austenitic (18/8 or 18/10) handle, bonded together.
Less expensive cutlery is often made as single piece martensitic knives, forks and spoons. This steel is not as costly, as it does not contain the nickel of the 18/8 - 18/10 types, but consequently has lower corrosion resistance. The corrosion resistance of cutlery made in this way should however be adequate for normal tableware use.
Cutlery manufacturers may choose to limit 'life' statements or guarantees on these lower cost pieces.
More information can be found on cutlery at the Cutlery and Allied Trades Association website.