High Copper 304L

[MetalMickey]

Hi all,
Looking at some 304L sheet at the moment with a high copper content of 1.5 wt% which was a suprise!, anyone think of good reasons chemistry may be at this level (everything else within AISI 30L spec) apart from poor scrap availability at the supplier?

 

[hacksaw]

copper helps with cold forming. it is common in stainless wire.

 

[rd400guy]

Austenite stabilizer? It might pose some welding concerns, as there would probably be 0% ferrite at that level - weld cracking or HAZ cracking possible. Could correct with higher FN rod. Most likely contaminated scrap, as you mentioned. Anything below 0.75% is usually standard.

 

[mcguire]

Is this material certified as 304L? It could be that the producer is trying to save money by substituting copper for nickel.It is certainly not an accident. This substitution can be done from an alloy design point of view and from a legalistic interpretation of ASTM standards, but it is not normally done. Call the mill who certfied it and ask them point blank if this is an intentional act on their part.
In this case high deliberate levels of an unspecified element is not harmful, but I wouldn't trust every producing mill to know what's best for your situation.
Ever wonder what they analyze for and don't report? I think steel purchasers would find that very interesting. By the way, normal residual Cu levels in 304 are 0.3%

 

[arunmrao]

Substition of Ni by Cu or Mn is a cheap and deliberate practice adopted by unscruplous manufacturers. Last week I came across 202 being passed off as 304.There is a great demand in our country for 304 and 316 grades, now with Moly prices sky rocketing one can find all sorts of unfair practices.

 

[mcguire]

Arunmrao is right. All steel looks the same and cheaters can fool you. But anyone who uses 304 stainless steel with nickel prices where they are today should switch to a PROPERLY made 201 or ferritic stainless, such 439 or 430 Ti.
I have helped many people do this and generate savings of $millions with no adverse effect.

 

[hacksaw]

it may be 302Cu rather than 304L

 

[MetalMickey]

Thanks for the input guys, to clarify all the other parts of the analysis fit 304L including Ni levels (albeit right at the bottom of the spec). The supplier has stated that the copper level is for deep drawing applications (not applicable to our use) which fits with hacksaws thoughts. I agree, mcguire, on the tricks the mill's try to pull, unfortunately we are seeing it more and more now.

 

[rd400guy]

I talked with one of our other metallurgists yesterday, and he's seen 304L intentionally made with higher copper and purposely sold as "antimicrobial" sheet for use in food service and laboratory equipment.

As for substituting Cu for Ni, I wholeheartedly agree that this practice is unscrupulous. Most mills will run expensive alloys toward the lower end of the spec, as long as the steel still meets required properties. But with the rising price of alloys the mills are passing this cost on to the customer in the form of surcharges, so intentionally substituting alloys with similar effect doesn't make much sense. Unless they're trying to surcharge you for nickel and giving you copper, in which case they'll probably be in litigation soon.