316 with Cu content? material identification help

[rmetzger]

We recently received parts with a 316 spec that had the following composition:

Element
C 0.03
Mn 0.91
Si 0.30
P 0.018
S 0.001
Cr 17.0
Ni 10.9
Mo 2.09
Cu 3.22

They were supposed to be 316 - anyone have an idea if this is a similar grade (parts from China) or what we can expect from this material. Seawater corrosion is our main concern (continual submersion - not sealing surfaces)

thanks
Ron

 

[metengr]

Ron;
This looks like a bad heat of steel. The high copper could be from a heat that was intended to be 17-4 PH stainless steel. Either way, I would reject it, period.

 

[arunmrao]

copper must have got mixed up in the scrap . This is an off heat chemistry and can be rejected.

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[jistre]

Add one to the "me too" chorus. Reject these parts outright. You specified 316, they did not provide 316. Period. Why spend time and effort trying to see if the metal they provided will do what you want it to? It's their responsibility to provide what you asked for in the contract.

 

[arunmrao]

Except copper the entire chemistry conforms to 316 L,source of copper is what surprises me as no other element is out of spec. Perhaps if the application is not in an aggressive environment,one can get on with due concessions.

Probably if it is a casting,then my guess is that the lining of the melting furnace must have contributed to copper pickup from a previous campaign of copper casting!

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[btrueblood]

Or, they started with fastener-grade 18-8 (30403?) then threw in some Moly to make it look like 316?

 

[rmetzger]

thanks all!

I couldn't cross this composition with any grade either.

Ron

 

[btrueblood]

Sorry, that should've been 30430, sometimes called 304Cu, or 18-9LW. Could also be 30433 (302HQ).

I can't see why a copper addition would decrease the pitting resistance (which is why I think you want 316 in a seawater environment?) of the 316, but can't find any data to prove it, either.

 

[rmetzger]

we seem to have a new twist in this..

The manufacturer is saying they are meeting an ISO 3506-1979 which stipulates that the material can deviate from the chemical composition as long as the manufacture can guarantee "the required physical and mechanical properties" and "an equivalent corrosion resistance"

Defining the first item is fairly straight-forward, the second is almost per application so its much harder to define. Does anyone have any insight on this standard or its acceptance in industry?

 

[CoryPad]

Are you purchasing the parts according to ISO 3506-1? Are you requesting Grade A4, which is generally equated with 316?

Grade A2 allows up to 4 % Cu. It doesn't specify a Mo concentration, but it allows Mo at the descretion of the manufacturer.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[metengr]

rmetzger;
I would ask the supplier for specific corrosion test information to support

an equivalent corrosion resistance

with this level of copper content in lieu of any guarantee before I would accept for use.

 

[rmetzger]

we requested the test results and test procedures from the supplier as well as info on any corrosion testing that was performed.

The print specified the grade of material (316) but no particular standard was on the print (ie - it was not listed as ASTM or AISI 316). The ISO standard cross references to the AISI or ANSI standard but via breaking them down as grade A1, A2, A4 much more generically. We did not specify a ISO grade A4 material as the shop delivered (and are claiming is equivalent)

 

[rmetzger]

one additional question:

I've not typically found that crossing standards is acceptable unless its stated specifically on the print. I'm not an expert in the field of metallurgy so I'm wondering if we should expect that specifying 316 will open us up to comparable grades without our prior consent. To me thats poor practice but that may be the recognized standard in other disciplines. thoughts?

again - thanks for the help!

 

[arunmrao]

If your request is for 316 then you get 316 , and no deviants. This is the first time I am hearing of such an expeerience. I hope the drawing too reads as 316,which shall be the last call.

Perhaps time for you to have a rethink on the supply source .

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[Metaljon]

I would reject it as being totally unacceptable. Raised copper levels in stainless steel is becoming an increasing problem due to scrap recyling. 3% copper content is grossly abnormal. We had one client who used a high copper (1% addition) stainless steel grade on an expensive balustrade system on a building which needed to be pickling after welding. The surface after pickling produced a horrible mottled appearance. The balustrade system had to be scrapped and remanufactured. It shows that copper does degrade surface corrosion resistance and is not good practice.