Does E70C-6M welded with 90Ar/10CO2 conform with A5.18?

By Lawrence (*****)

Date 09-05-2014 12:40 Edited 09-05-2014 12:43

That's a really good question.

I can help only a little by letting you know that for MCAW that A518 has been superseded by AWS A5.36 2012
Since D1.1 is a 2010 publication it will not reflect the change.

I have a copy but am not totally confident in what I do and don't understand.

I read:

The "C" designator for shield gas indicates a 100% Carbon Dioxide Shield gas.
The "M" designator for shield gas indicates a 75-80% Argon/balance C02 gas mixture.

This so far is the same as A518.

Back to A518..... Table two note "c" says"
"Use of a shielding gas other than will result in different weld metal compositon"

Does this mean 90/10 ain't a prequalified gas mix for your electrode?

So I looked a data sheet in my files for Corex Coreshield 8 which has the same designator as you posted E70C-6M and it "says" it has A518 compliance and lists a variety of shield gasses... Yours falls within the upper and lower percentages tested and found compliant.

I attached two data sheets... One older that has a 90/10 mechanical testing statement and one newer that provides more data but not on 90/10

Maybe somebody else can answer with more authority.

Attachment: MetalCor62014.pdf (324k)

Attachment: MetalCor6.pdf (29k)

By 803056

Date 09-05-2014 13:24 Edited 09-05-2014 13:27

I wouldn't challenge the position that it meets the requirements for prequalification as long as the manufacturer has published test data.

I would however use this electrode with caution for thick connections that require more than 6 weld layers. The mechanical properties indicated by the manufacturer's product sheet indicates the silicon and manganese increase with the higher percentage of argon in the shielding gas. The increasing amounts of deoxidizers in the weld deposit increase the carbon equivalency and could lead to a cracking problem when welding thick sections. Deoxidizers that not required for the purpose of deoxidation increases the strength, alloy content, and the carbon equivalency of the weld deposit

Best regards - Al

By ssbn727 (*****)

Date 09-05-2014 22:47

And to add to Al's points he makes of using certain percentages of argon in the mix, here's an article that will back up what Al's talking about:

http://www.fabricatingandmetalworking.com/2013/10/percentage-of-argon-in-mixed-shielding-gas-does-matter/

Even if one is using Metal cored filler, the same potential for these sort of problems can happen so one cannot say; "Well, that's just for FCAW dude!"

Your best bet is to heed to Al's advice about making sure what mix you can use with the specific cored filler you're using with the manufacturer of the wire & the EOR before moving forward and deciding to use it blindly.

Respectfully,
Henry

By BillC

Date 10-04-2014 16:04

Thanks to to the three of you for the helpful answers. I apologize that it took me so long to get back to say so. I did not dispute the use of the gas with the vendor because it was a qualified procedure.

This does point out that that the welding codes don't protect us from all of the possiblities, though. For example, what if the vendor had qualified the procedure using the 90/10 Ar/CO2 gas but with a wire intended for 100% CO2 gas (C designator)? At least our policy of approving WPSs prior to releasing purchase orders lets me screen for these things.

Thanks again.
Bill