ASME Section IX LBW and Qualified Thickness for Groove Weld 2

[Ryan615]

Hi all,

I need some clarification on ASME Section IX in regards to qualified thickness of a groove weld using the laser beam welding process. I have read a number of posts, but did not find many posts specifically related to LBW. A search for QW-403.3 did not bring up any relevant information. I am trying to determine at what thicknesses I need to qualify in order to achieve the desired parameters for a new WPS. I am trying to qualify 0.025 in. to 0.050 in. thick base metal on one WPS. The weld is joining sheet to a plate with a machined step that acts as an integral backing plate (the machined step depth is matched to the thickness of the sheet).

First, I believe I have correctly worked through the code to determine requirements for WPS development. QW-202.1 sends me to QW-451.1 to determine relevant testing. The notes on QW-451.1 send me to QW-403.2, .3, .6, .9, .10; QW-404.32; and QW-407.4 for additional limits on thickness qualified. QW-264 (LBW Essential Variables) tells me that QW-403.3 is the only relevant note from the notes of QW-451.1. (I think I have it right up to this point).

QW-403.3 states:

Where the measurement of penetration can be made by visual or mechanical means, requalification is required where the base metal thickness differs by 20% from that of the test coupon thickness when the test coupon thickness is 1 in. and under, and 10% when test coupon thickness is over 1 in. Where the measurement of penetration cannot be made, requalification is required where the base metal thickness differs by 10% from that of the test coupon when the test coupon thickness is 1 in. and under, and 5% when the test coupon thickness is over 1 in.

The test coupon is <1 in., so this all comes down to whether or not "measurement of penetration can be made by visual or mechanical means." If yes, then I would interpret this to mean that the WPS is valid for +/-20% of the test coupon thicknesses. Otherwise, we are limited to +/-10% of the test coupon thickness. This would mean that in order to achieve our WPS thickness range goal, we need additional PQRs.

We are using destructive analysis (macro etch) on a sample of parts during production to determine penetration. We cannot do a direct visual measurement of penetration due to an integral backing plate. I don't think our DE meets the definition of "mechanical means" but, for me, that is the hang up. Where are the "mechanical means" defined? I'm having a tough time understanding whether I fall in the +/-20% or +/-10% range.

If anyone has any feedback on this one, I would greatly appreciate it. Hopefully I'm not hopelessly lost on this one... I'm shooting for partially lost. Partially lost, I can manage.

Thanks!
-Ryan

 

[Ryan615]

Any insight on this one? I'm pretty much convinced T to 2T is not applicable for this application, and I'm thinking that we are able to qualify +/- 20% T. It seems logical, anyway.

Thanks,
-Ryan

 

[DekDee]

Ryan,
Your situation falls under QW 403.3 (b) - Full penetration single - sided welds with backing so T to 2T is applicable,
Hope that helps,
Cheers,
DD

 

[aburafdi]

Ryan,
As your weld is with backing, then "Where the measurement of penetration cannot be made" applies. Thus the limit is 10% thicker.

Regards,
AR

 

[aburafdi]

Sorry....wrong placed smiley.

 

[Ryan615]

Thanks folks. Looks like the older version of the code I borrowed is missing an important clarification. New versions specifically reference backing. That clears it up. Seems to me, that puts us at 10% (not T to 2T, which is just a bad idea with LBW).

Is there any allowance for me to use logic to qualify the thicknesses between those used in the PQRs? If I qualify .025 and .05 thicknesses at the same settings, it seems rational to consider the thicknesses in between qualified as well.

 

[DekDee]

Ryan,
Did you look at QW 403.3 (b) ?
It is not in the 2007 edition but it is in 2010.
If you do a PQR on 0.025 mm it qualifies you from 0.025 to 0.050 (T to 2T) and those thicknesses in between which is apparently what you want.

In answer to one of your earlier questions - macro-etch is a perfectly acceptable "mechanical" means of determining depth of penetration.
Regards,
DD

 

[Ryan615]

DekDee,

I looked through the 2013 version of the code and there was no 403.3(b).

-Ryan

 

[DekDee]

Ryan,
I do not have a 2013 edition so cannot comment.
Does seem strange it was not in 2007 edition, was added in 2010 edition and then removed in the 2013 edition.
This may explain the removal (although not specifically mentioned)

Summary of Changes in
ASME Section IX, 2010 Edition, 2011 Addenda
As published in the Welding Journal, November, 2011
Pages 61 through 63

There were major changes in the variables for procedures and qualification for laser
beam welding (LBW). The prior rules were conservative since the industry had little
experience with LBW when they were written in the 1980s. The revisions reduce
the number of qualifications that are typically required and tighten up some
aspects. For example,

The joint design to be used is limited to that qualified.
The base metal thickness qualified now has only a maximum qualified thickness
instead of a minimum and a maximum.
Filler metal is no longer limited to the specific chemical composition qualified
as long as it is the same F-number and A-number.
A tolerance of ±10% has been added to oscillation width, frequency and dwell
time and to beam pulsing frequency and duration.
A tolerance of 10° has been added to the angle of the beam relative to the
workpiece surface.
The type of equipment is no longer an essential variable, but additional variables
have been added to address the type of laser (YAG, CO2, etc.), beam optics
and gas.

Cheers,
DD

 

[Ryan615]

Great post! Thanks for the info. I'll be looking to get a PO approved for the new version today. Looks like some significant changes that are directly related to a core piece of equipment.

-Ryan C

 

[Ryan615]

Interesting that the summary of changes claims: The base metal thickness qualified now has only a maximum qualified thickness instead of a minimum and a maximum.

I can't find anything that supports this. Wonder if this should read "...maximum qualified depth of penetration."

-Ryan