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XL83NL (Mechanical) (OP)
28 Sep 12 8:49
I have a question on orbital GTAW welding in ASME IX (2010 edt 2011 add), specifically on how 'passes' are addressed in orbital welding where no filler material is used (i.e. T-joints).
Definition on pass acc. ASME IX;

Quote:

pass: a single progression of a welding or surfacing operation along a joint, weld deposit, or substrate. The result of a pass is a weld bead or layer.

Let's say a PQR is made based on a pWPS where the electrode only does 1 orbit (i.e. slightly more tahn 360 degrees) around the joint to be welded.
No filler material was used. Joint design is OD up to 1", wall thickness up to 0.083". Notch toughness is not required/addressed by the Code. Code of construction is B31.3.
While welding the pWPS, an additional sample was made to qualify for a WPQ. The orbital welding machine is defined as machine welding in ASME IX.


Now, say we make a new WPS where 2 orbits in stead of 1 are made during welding. Are these 2 orbits then defined as a multi pass?
I believe 2 orbits have to be considered as a multi pass acc the ASME IX definition on passes. Technically one may argue that no extra weld bead or layer is made during the 2nd orbit, hence 2 orbits can also be considered as a single pass.

Assuming 2 orbits are defined as multiple pass;
For the PQR it seems no re-qualification is required, acc QW-256; QW-410.9 is a supplementary essential variable. Hence no restriction.
For the WPQ it seems re-qualification is required, acc QW-361.2(h); the welding operator has changed from single to multiple passes per side.


Anyone who can share his thoughts?
metengr (Materials)
28 Sep 12 9:29
The above example would be considered multipass welding. Each pass is defined as above so I don't see how one can argue that re-melting is not considered a second pass.
gtaw (Structural)
28 Sep 12 9:47
I concur. Two rotations of the welding machine is multipass. The welding is considered to be autogenous, i.e., no filler metal additions.

Best regards - Al

XL83NL (Mechanical) (OP)
28 Sep 12 16:11
So one may not argue that such a re-weld (or 2nd orbit) doesnt make a new layer or weld bead?
You might say that there really isnt any layer (as defined in ASME IX), as there's no weld 'deposit'. See definitions of layer and weld bead:

Quote:

layer: a stratum of weld metal consisting of one or more beads. See figures QW/QB-492.1 and QW/QB-492.2.

Quote:

weld bead: a weld deposit resulting from a pass.
Dont get the me wrong, I just want to know why it's considered as such, so I try to be critical.


Helpful Member!  gtaw (Structural)
28 Sep 12 16:26
A weld can be made with or without the addition of filler metal. Regardless of whether filler metal is used or not, the base metal and the previous weld are subjected to additional thermal cycles each time the welding arc passes over the area. The thermal cycles will affect the base metal in one way or another. Rarely is the influence of the additional thermal cycle completely benign. Usually the mechanical properties suffer, but not in all cases.

Whether the mechanical properties are affected can only be determined by testing a sample to see what the results are.

Best regards - Al

dhengr (Structural)
28 Sep 12 16:58
Coming out of a groove weld, for example, you might have one layer which is 1 - 1.25" wide, made up of 3, 4, 5 or 6 weld beads or passes, for that layer. This weld might be made with a single welding head, thus 3,4, 5... rotations are required; or it might be made with multiple heads, in which case it takes fewer revolutions. But, the number of layers or the number of weld beads doesn’t change. Maybe you could make a case for fewer passes when using a multi-head welding system. You never (rarely, unlikely) completely remelt previous weld beads or passes, or welds in a previous layer so you still have various layers of metallurgy from each weld pass. With some processes and consumables multiple weld beads and layers can precipitate some alloying elements to a higher concentration in the upper layer, and this can cause problems.
XL83NL (Mechanical) (OP)
3 Oct 12 3:32
thanks all for your insights.

could anyone think of agrument(s) that would not make it feasible to define orbital GTAW welding as automatic welding (see pag 201 ASME IX 2010 edt 2011 add), instead of machine welding?
XL83NL (Mechanical) (OP)
3 Nov 12 9:49
PQR's from Lloyd's seem to indicate orbital GTAW as being automatic welding. Guess that answers my question :)

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