M20 and M21 Gas question

Date 01-27-2022 18:39

My questions are about using 92% Argon and 8% Carbon Dioxide shielding gas with Hobart’s FabCOR Edge E70C-6M electrode.

Here is the link to the data sheet:

https://www.hobartbrothers.com/wp-content/uploads/hobart-catalog/datasheets/FabCOR_Edge.pdf

On the data sheet, in the upper left corner, is the information:
AWS 5.18: E70C-6M H4
EN ISO 17632-A T46 3 M M21 3 H5

First set of questions:

I am assuming that the M21 means that this electrode is only approved for M21 gas under AWS A5.36, which per AWS D1.1 (2020) Annex M Table M.5 is a mixed gas with greater than 15% up to and including 25% CO2. Is this a correct assumption?

If my assumption is correct, why does Hobart bother listing mechanical properties with 90/10 shielding gas (which would be M20)? And why would Hobart have a parameter table using 90/10 data and only mention 75/25 data in the notes below the table?

If the electrode is only approved for M21 gas, but I want to use M20 gas, would I have to qualify the WPS?

Or have I misunderstood what the M21 is for on the data sheet?

Second set of questions:
In Table M.1, it says that AWS A5.18 electrode with a classification of E70C-6 should be used with M21 gas but refers to note i below which says “For purposes of the D1.1 code, the prequalified argon/CO2 mixed shielding gas shall be limited to SG-AC–20/25 as with the previous AWS A5.18 and AWS A5.20 classification shielding gas requirements, and not the shielding gas range of M21.”

Does this mean that when using E70C-6 electrode, the shielding gas should really be 20 to 25% CO2 and not the 15 to 25% of regular M21 gas?

If yes, then using 92/8 shielding gas would not allowed under A5.18 either. Is that correct?

All of this boils down to one question really: Would a WPS written to AWS D1.1 (2020) requirements using E70C-6 electrode and 92% Argon 8% Carbon Dioxide be considered prequalified?

By Lawrence (*****)

Date 01-28-2022 16:06 Edited 01-28-2022 16:11

Hi TA

I don't see a way we can finagle it . As much as I would like to.

Table 5.7 goes down to 90/10 but is exclusive of MCAW electrodes. So No Joy.

D1.1 2020 Clause 5.6.3 (5) May be the door.

The Hobart electrode wire you linked looks superb and even has Impact testing high/low for Seismic D1.8 with 90/10 which I would assume is also an A5.18 classification test. But you would need to verify.

But I don't see a work around for 92/8 being prequalified even with solid wire....

A5.36 has been withdrawn... But is still right there in D1.1 meaning: You can use it if it suits you and ignore it and use A5.20 if it doesn't.

One thing you might do is reach out to the Hobart application engineers who's email is linked on the Data Sheet for the electrode wire and see if they have a work around that is compliant that I don't see.

D1.1 2020 Clause 5.6.3 (5) May be the door for Hobart to help. There may be testing ongoing or that was not published on that COC.

It all seems a bit crazy as a large portion of the industry uses 90/10 (M20) + or - 2% for MCAW. It's the most common bloody spray transfer gas in America... Not so much in the U.K.

By TALower (*)

Date 01-31-2022 22:07

Lawrence,

Thanks for the reply. I didn't dig into clause 5 as much as I should have to answer my questions. I knew about Annex M and quit looking after I had enough to ask my questions.

If A5.36 has been withdrawn, what does that mean for Annex M? It deals almost exclusively with A5.36.

Also, now that I have studied Table 5.7 better, are you not allowed to use ANY Ar/CO2 mix with CO2 below 10% without qualifying? If so, why is a 92/8 Ar/CO2 mix so frequently pushed by suppliers like AirGas and Praxair?

Anyway, now I need to have the shop change to 90/10 gas or qualify the procedures by testing. I kinda doubt that Hobart is going to do more testing. The datasheet was updated recently if I read the bottom of it correctly.

By Lawrence (*****)

Date 01-31-2022 22:36

Hey TA

As I read it. If the Manufacturer has qualified the electrode wire with "whatever" gas mix to A5... Than it's good for prequalification IAW D1.1 2020 Clause 5.6.3 (5) You never know. Maybe Hobart has taken this step for your gas.

If A5.36 has been withdrawn, what does that mean for Annex M? It deals almost exclusively with A5.36.

It's noted. You can use it. You may also use 2021 A5.20 Which ever best suits.

By 803056

Date 02-03-2022 22:53

Are you by chance confusing the AWS classification with the ISO?

The AWS classification under A5.20 simply specified a mixed gas. The ISO classification calls out the M21.

Maybe I'm confused.

Al

By Lawrence (*****)

Date 02-04-2022 16:45

Good question Al

A5.20 2021 revision provides "Mandatory Classification Designators" in a graphic.

The designator for "M" mixed gas says: M indicates that the electrode is classified with 75-80% Argon with Carbon Dioxide balance.

To me this says if an electrode other than in that range is to have A5 classification the Manufacturer must perform the tests in accordance with A5.20 with gas mixes outside of that range and publish in their COC if they are to be considered for D1.1 Prequalified status in Accordance D1.1 Clause 5.6.3 (5) . Many have done this with both FCAW and MCAW electrode wires.

5.6.3 Shielding Gas. Shielding gases for GMAW and FCAW-G shall conform to AWS A5.32M/A5.32 and one of the
following:

5.6.3 (5) The electrode/shielding gas combination shall have been tested in accordance with the applicable A5 filler metal
specification. The tests shall demonstrate that the electrode/shielding gas combination is capable of meeting all the
mechanical and chemical property and NDT requirements for the electrode classification. For FCAW-G and GMAW
composite (metal cored) electrodes, tests shall be performed for each electrode manufacturer’s brand and trade name to
be used. Testing shall be performed by the filler metal manufacturer or gas producer. For FCAW-G, the filler metal shall
have been classified by the filler metal manufacturer as an “–M” (i.e. mixed gas) product.