Shielding gas composition for GTAW

[QualityAsia]

MY Owner has been requesting me to specify 99.997% Argon gas composition in our revised WPS, questions as below,

1. Are there any papers to support minimum 99.997% Argon gas composition required for GTAW?
2. 99.9% Argon gas composition was specified in old PQR. Can I specify 99.997% Argon gas composition in new WPS?
3. How many percents of Argon gas composition generally were used for offshore and onshore weldings by GTAW process.

Thanks & Regards

QualityAsia

 

[Ballbearing1]

Qualityasia,
What materials are you welding ?
Generally 99.9% Argon written on the WPS is acceptable (Usual welding grade argon is 99.995 or 99.996%)
The only time I have heard of a specific percentage being noted on the WPS (99.999%) is Ultra high purity argon which is required for welding Titanium.
Hope that helps,
Regards,
BB

 

[QualityAsia]

Thanks BB,

Materails are CS and SS per ASME Section II.

Refer to
1. QW 408.2(d), Cites to SFA 5.32 for Argon purity of shielding gas.
2. SFA 5.32 specifies the minimum purity of Argon for sheilding is 99.997%.

I am confusing because I see many WPS(s) specify 99.995% Argon purity.

Thanks & regards,

QualityAsia

 

[QualityAsia]

Materails are
1. WPS for SA 106
2. WPS for Materail Grade 316

Thanks $ regards,

QualityAsia

 

[QualityAsia]

Sorry for typing error, 99.95% Argon purity not 99.995%

Thanks & regards,

QualityAsia

 

[DVWE]

Are there any papers to support minimum 99.997% Argon gas composition required for GTAW?

As you already know, the SFA 5.32 is all you need to support this.

99.9% Argon gas composition was specified in old PQR. Can I specify 99.997% Argon gas composition in new WPS?

Yes, but then it ultimately becomes the welders responsibility to verify the gas purity. If anyone wants to know the purity of your Argon, you should give them that information from your gas supplier.

QW 408.2(d), Cites to SFA 5.32 for Argon purity of shielding gas.

QW-408.2(d) is refering to gas composition, not gas purity. Table 4 gives the AWS classifications for mixed gas compositions.

 

[Ballbearing1]

Qualityasia,
As DVWE has pointed out QW-408.2(d) is refering to gas composition, and not gas purity.
If you are welding titanium or other exotics that require ultra pure argon then yes, putting 99.997% minimum on your WPS would be correct.
However,you state you are only welding carbon and stainless steel which generally do not require ultra pure.
As most commercial grade argons are 99.995 / 99.996% you would not be able to use them, and ultra pure is much harder to source and more expensive.
Regards,
BB

 

[DVWE]

BB,

5.32 actually lists the minimum purity of Argon as 99.997%. You are saying this is classified as "ultra pure"?

 

[Ballbearing1]

Hi DVWE,
No I am not saying it is UHP.
I don't have a copy of 5.32 so I am flying a bit blind but when I googled the various gas suppliers it was either 99.995 or 99.996% for commercial grade argon and 99.999% for ultra high purity.
Does 5.32 list a minimum for UHP ?
Cheers,
BB

 

[DVWE]

BB,

Not that I can tell (for UHP). I read it as 99.997% is the minimum for any gas supplier that supplies Argon in accordance with 5.32. But, I'm less familiar with 5.32. Luckily for me, my customers don't hound me much on the subject of gas purity.

 

[Ballbearing1]

DVWE,
Had another look and AWS have a paper on "Recommended Shielding Gases for GTAW."
This states "Welding grade Argon and Nitrogen sre supplied with a purity of 99.995% or greater."
Is SFA 5.32 a mandatory document ?
Cheers,
BB

 

[DVWE]

If gas is supplied in accordance with 5.32, then yes, it is.

 

[QualityAsia]

Thanks all,

So,

1.QW408.2(d) specifies that Table 4 of SFA5.32 may be used to specify the shieding gas composition. And the table 1 specifies the minimum gas purity for each gas component only,doesn't it.

2."Recommended Shielding Gases for GTAW" by AWS is interesting.

Please kindly recommend how you select the shieding gas composition. What criterion do you use to make the decision on selection of the shieding gas composition for general CS or SS?

Thanks & regards

QualityAsia

 

[Ballbearing1]

Qualityasia,
If your specifications state a required gas purity or that the purity of the gas must comply with SFA5.32 then you are governed by those requirements.
Otherwise, follow the industry norms - 99.995% and greater for carbon and stainless steel and 99.999% for Titanium and Zirconium,
Regards,
BB

 

[DVWE]

Please kindly recommend how you select the shieding gas composition. What criterion do you use to make the decision on selection of the shieding gas composition for general CS or SS?

The annex of 5.32 is an excellent source.

 

[Ballbearing1]

Qualityasia,
To go back to the original question, if 99.9% was listed in the original PQR then 99.9% is all that is required in a revised WPS. If your owner requires 99.997% to be listed then you are limiting yourself when IMHO there is no reason to do this.
Regards,
BB