Maybe this was the wrong group to post this scenario in...

RCWI...

Aerospace welding is significantly different than industrial welding for a host of reasons that have taken me ~38-years to fully grasp.

NOTE.
My best mentor/teacher was a MASTER [my term] USAF Depot engine component welder who I worked with for +7 years. He could weld anything that was weldable... but applied a LOT of brain-power and 'set-up' before, and used amazing hands-on-skills during, weld operations. I did the easy part and presented suggestions on what needed repair, why repair was needed and what the part was used for. He studied each issue in amazing 'depth' and then announced 'I CAN DO this' or 'I CAN'T/WON'T DO this'. In either case, I trusted him and recorded the minutiae of his comments, concerns and the actual work. This is when I saw the blend of skill/art/experience/science in welding aerospace parts. I also learned another lesson: this is such a variable skill that You must know/trust Your welder to do the work to the highest level when chips are down and skin is on the table. This is when I learned that experience, skills and MUTUAL TRUST with Your welder is an absolute priority. There are times today, when I see a potential salvage repair for a part/Assy... but cannot trust that the 'right welder for the job' will actually be assigned to do the job... hence I WON'T allow the part to be weld repaired.

RANDOM THOUGHTS.

Engineers MUST know the materials [base/filler], joint design, welding specs, weld-processes and actual application [how critical is it?] before starting any job; as well as what has to happen before-hand [NDI for-extent of damage] and afterwards [post-weld NDI, re-machining/grinding to contour, finish restoration, etc].

Welding on new parts/assemblies is far different than repair-welding on parts/Assys that have been in-service a long time.

There is a substantial difference between each of the major alloy groups [Magnesium, Aluminum, Steel, Stainless steels, Heat-Resistant Alloys, Titanium, Ti, Cu, etc] for welding practices.

Welding wrought materials can be substantially different than welding on 'wraskley-castings' .

Base metal considerations**, weld filler selection, welding equipment parameters, careful cleaning and sculpting of bare-metal to-be-welded-surfaces, pre-weld heating, dry/inert gas saturation of the weld, actual welding sequence, post weld cool-down, post-weld re-heat treatment or stress relief, etc... are all massively important.. just to name a few of the 'big-ticket elements of concern'.
**some older aerospace drawings allow multiple base-material options: knowing EXACTLY what You are welding-on can be a challenge and may be a serious factor in up/down decision making.

Good aerospace welding practices dictate welding/testing of samples to verify materials, processes, techniques, etc. This is where a highly experienced master welder can make a difference for 1-off jobs of all-kinds: They already know how [by prior experience] to get desired results 'down to the gnat's-ass'.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

Thanks for the thoughts Wil, I am figuring out a lot of things quickly about aerospace welding. Fortunately the welding is the easy part. Unfortunately I find myself struggling with writing procedures that are sufficient to cover my bases. I have read many wps's and most of them have been fairly simple. Maybe I am trying to make this harder than it actually is. I appreciate your input and agree with your thoughts completely. I will struggle through writing the first couple of procedures, but I am confident I will figure it out.

I've been in your position, myself. Here's another way to think of it:

The engineer creates a drawing of the weld joint (either new fabrication or repair) and can specify all sorts of things such as the base materials, geometry, filler, thickness of the joint, post-weld heat treat and so on.
The welder, on the other hand, is trained to produce a joint with consistent properties, by setting the welding machine correctly, shielding gas flow rates, preparing the electrode, and so on.

Somewhere in between the drawing and the finished weld are a LOT of other steps that must be communicated in BOTH directions. The engineer and the welder must be made aware of fixturing, cutting, deburring, cleaning, and plenty of other steps that must be done for the weld to succeed. That's where the WPS steps in. If you don't have a document that specifies how to clean a part before repairing it, you will get contaminated weld repairs.

Your WPS doesn't have to go so far as define the tasks that are part of the welder's skill. It is best to specify a standard level of qualification and leave it at that. You may need to state that the capabilities of the equipment used must be adequate for the welding job at hand, but again, turning that into a specific capabilities list of your welding apparatus will just be a nasty list to maintain, and may "lock you in" to specific capabilities.

Please excuse the rant, but this reminds me of something that bothers me. I dearly wish my company did not put the available sheet-metal brake radius sizes into our sheet-metal forming process standard, but, unfortunately, there they are. I tried to get it taken out once, but the whole thing was re-revised a few months later and they were put back in. Some designers in the engineering department interpreted the absence of the list as carte-blanche to specify any bend radius they pleased, and so oddball bend radii were being approved on drawings. To me this was a training problem for engineering, but my superiors didn't see it that way. So we're now back at the original situation where a bend radius may appear on the drawings at "0.13" but the actual tool is "0.125" while the drawing tolerance is "+/- 0.030" meaning the part cannot be made without a non-conformance report.

Sorry for the tangent - just giving you a taste of how a process specification can go wrong.

STF

More random thoughts,
Noting the discussion on weld procedures here, and a passing comment about carbon steel. and yet another about Tig machine settings and gas purging, I should point out that Oxy fuel welding is alive and well particularly in maintenance settings. for tubular steel aircraft fuselages out in the field where you cannot get a Tig welder, and for aluminum fuel tanks. Some proponents claim that aluminum fuel tanks welded with oxy fuel and flux have less tendency to have porosity in the weld seams, and that the weld progress rate is comparable to Tig on thin aluminum.
Do not get locked into one particular method of welding a part new or repaired.
B.E.

You are judged not by what you know, but by what you can do.