304 sTAINLESS VS. 18/8

[nmiltner]

We are having a discussion over whether 304 stainless and 18/8 are the same material. My arguement is that 18/8 is the "family" and 304 is a member of the family along with 304L, 304H, 302...

basically, 304 stainless is an 18/8 steel, but 18/8 is not 304.

I am not a material specialist, so please bear with my lack of knowledge. Can someone set me straight?

Thanks

 

[metengr]

nmiltner;
Normally, grades of stainless steel are identified by number prefix 2,3,4xx. The "18/8" means nothing other than a generic classification. In reality, ordering a particular grade of stainless steel should be by UNS.

 

[MikeMet]

You are correct in your statements. 18/8 is still used by component suppliers as a materials designation for Type 304 sst. But as you state, 18/8 can fit more than just Type 304, so buyer beware if corrosion resistance or other special properties are required.

 

[strider6]

as you can see in this publication,

http://www.euro-inox.org/pdf/map/What_is_Stainless_Steel_EN.pdf,

304 is often referred to 18/8 or 18/10.

http://www.corrosionist.com/Materials_Stainless_Steel_Properties.htm

S

Corrosion & Rust Prevention Control

 

[JoeyV87]

Am I wrong in thinking that the Nickel content of a 304 is higher than 18/8? In my experience, 18/8, 17/4, 15/5 etc refers to chromium/nickel. Since 304 typically has at least 10% nickel, wouldn't this make it more of an 18/10?

 

[mcguire]

Yes. 304 has 8.0% minimum nickel. It is allowed to have up to 10.4 but you get more only if you specifically pay for the expensive extra amount. 18/8 is merely a nickname for 304. It was also the nickname for the outdated 302. Europeans started calling it 18/10, still a nickname, when they also knew it seldom, if ever, had that much nickel.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/