Shielding gas change: Essential Variable requirements

[WeldAppEng]

I work for a global Gas Manufacturer/Supplier and have a question re: Sect IV.

What is the threshold of change or allowable deviation in a shielding gas mixture that would not invoke the essence of it being considered an essential variable.?

Example: Root runs with GMAW process using either an S2 or S6 wire.

Gas: 75/25 Ar/CO2

If a gaseous additive in the amount of 275ppm was added, would this necessitate a re-qualification.??

thanx muchly.!

 

[Kiwi2671]

WeldAppEng,
You note Section IV ?
Do you mean Section IX ?
If so
QW 408.2 (c)requalification is required if you have a change in the specified percentage composition of a shielding gas mixture.

So if 75/25 Ar/CO2 becomes 75/24/1 AR/CO2/Additive you would need a new PQR,
Hope that helps,
Regards,
Kiwi

 

[WeldAppEng]

kiwi..I truly appreciate the response.

But as I noted the only addition to the mix is 275ppm of an additive. Not even close to 1%.!

The additive is NO (Nitric Oxide), It is added to the gas mix to reduce Ozone which is generated via ultra violet rays in the 100-200nM range generated by the arc. The Ozone (o3) reacts with the NO to make NO2 and O2. I wont get into a debate on the toxicity of NO2 but will state that the TLV of Ozone is .05 -.1% whereas NO2 is 3.0% 30-60 times less toxic.

What we have found and it was not our research that claims this, yet the majority of end users have told us that aside from a reduction in weld area ozone levels, they find a much more stabilized arc especially in short arc GMAW mild steel as well as stainless, and to a certain extent improved mechanicals: CVN & Tensiles. Up to 8% increase in values seemd the average when tested agains std grades.

This was noticeable with E71T-1, E70S-6 and E70C-6m type wires.

Our argument is that the additive is in no way impeding nor changing the base value or mixture by the addtion of the 275ppm NO. Although anecdotal evidence does seem to support increased mechanicals, this phenomena is/was an unexpected bonus.

I'm not try to sell this product here, simply trying to see if it is worthwhile to have ASME/AWS look at the product and make a determination as to whether the infitesimal minute amount of 275ppm is really a significant enough of a change in gas mixture to warrant invoking "essential variable"

Rgds,

 

[Kiwi2671]

WeldAppEng,
You need to get hold of SFA 5.32 (which I do not have).
It deals with purity, composition etc of shielding gases,
Regards,
Kiwi

 

[WeldAppEng]

Excellent Kiwi..thank you.

 

[rodofgod]

Hi All!

WeldAppEng, if the addition of NO has an effect on the weld properties of a material, then despite the very low amounts, I would have thought re qualification would be in order.

Regards

 

[WeldAppEng]

Well that may be. I can think that the only reason said mechanicals might be better than normal would be a slight removal of oxygen from the shielding gas itself due to the NO..? No-one really knows at this point.

Still thanx guys for the commentary.

 

[weldtek]

From past experience, the purity requirement for Ar is 99.997% min.

 

[GenB]

"simply trying to see if it is worthwhile to have ASME/AWS
It is my opinion that it is not acceptable. If I use the additive my inspector will shut me down in no time.

You can write the ASME and AWS and ask to qualify your idea. they should allow it. note that they will not under the current classification but listed as anew one.
then you patent the idea and make tons of money.

genb