Welding question

[geraldmorrissey]

I made an honest search of the forum but gave up without an answer. Pretty sure I've seen this question before, maybe by me. Can I tack with O/A and finish weld with Tig? Concerned about compatibility of the filler rods. Want the option of going either way for finish welding.

[jaredyates]

You can definitely go the other direction, tacking with TIG and then OA finish welding. Hopefully someone with more knowledge can answer your question.

[alaskabearhawk]

No problem at all with that.

[davzLSA]

I do O/A welding and use the same filler rod that is used for tig welding. If you can use the same rod for both it can simplify things?

[Redneckmech]

It just happens that my supervisor for my day job is an aerospace welding engineer, I asked him this question and his response was that if your tacks are fully consumed when TIG welding across them you should be fine providing a suitable TIG filler is used for the finish weld.

He did state not to use OA rod for TIG welding. TIG rods have higher concentration of silicon and other de-oxidizers to make them more suited for Tig welding. OA welding allows the impurities to be flushed out and pushed ahead of the weld puddle due to the greater heat input so RG series rods do not have de-oxidizers and are unsuitable for use with TIG as they can result in porosity and impurities in the weld.


Hope this helps,

Bill

[whee]

I agree with the above.

just make your O/A tacks using tig rod and use the same tig rod for final welding. That just keeps things easy.

[Mark Moyle]

Look for Paul Minelga’s destructive testing videos on you tube. You’ll learn one key thing from his videos as it pertains to TIG welding. Weld the entire cluster all at once. TIG welding induces allot of heat into a small area. You want to get the entire cluster hot enough to reduce the formation of martensite crystal formation.

[spinningwrench]

As mentioned above TIG rods have far more de-oxiders so do your welds entirely with TIG rods if switching between technologies. I actually find it more useful to do small tack welds with TIG rather than O/A and the problem you will have is that O/A makes a much larger weld puddle than TIG so you will have to work hard to totally consume your O/A tack welds if welding over the top with TIG. You may find the videos of TIG aircraft welding from "Mr Tig" on YouTube to be very informative.

[fairchild1934]

maybe its just me---- but I dont find Mr. Tig's welds all that cosmetic. i like Jody at welding tips and tricks MUCH better.
i often use .035 er70-6 mig wire for tacks and welds on small tubes (1/4 and 3/8) and especially where sheet metal ribs weld to the tubes.

[JayDub]

Mark hit on what I was taught when he said, "TIG welding induces allot of heat into a small area". Because of this you can have a hardened zone that is narrow between the weld and the normalized steel from the mill. I was taught if you tig weld the chromoly you need to come back with a "rosebud" torch and heat the joints back up to an orange/red and let them cool as it gets rid of that hardened zone which would be susceptible to cracking: air cooled normalizing. I like to TIG weld and it seems cleaner but OA eliminates this added step of reheating joints because the OA welding puts a lot of heat all over the parts eliminating that hardness zone. YMMV

[spinningwrench]

Normalizing 4130 steel is a very precise operation that can only be done by soaking the metal in a controlled heat oven for a long length of time and followed by a very gradual cool down. Heating with a rosebud is not normalizing and is completely unnecessary in metal thicknesses under 1/8” thick. There is a reason that TIG welding is the only approved method for welding NASCAR race car frames and it doesn’t involve post heating with a torch.

[sjt]

I liked the recent EAA webinar

https://www.eaa.org/videos/webinars/aircraft-building/6319145063112

THESE ARE GENERAL GUIDELINES FROM WEBINAR

TIG ==> No need to normalize with rosebud

for tubing some prefer 9 series flex head - limited amperage

1/16 tungsten
if you can get RED 2% thoriated otherwise use (BLUE maybe better for aluminum)
dedicated grinding wheel.
tig finger (weldmonger.com)
gas lens (I got mine from JODY tig welding tips and tricks weldmonger.com)
can save gas but I need it for the stick out in some locations -UP TO 1 INCH- 10 to 15 cfpm

if you can get it er80s-D2 otherwise er70s-2 or er70s-6
0.045 for good fitup or 1/16 for 1/2 or larger tubing

(I got some from amazon 0.045)

https://www.amazon.com/gp/product/B00G4B5SQ0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

for ac your choices are 4043 for some alloys and 5356 for other alloys
3003 for fairs 4043 rod
5200 for gas tanks 5356 rod
6061 for fittings 4043 rod

warning you can not clean aluminum enough times
warning you can not pull rod out of gas shield

questions and answers are about 1 hour into webinar



Earl Luce taught me at the gas welding school. This webinar was Tig.



I have tried to use the tube oil product. I am always disappointed when I go back a month latter - after priming - and find that the tube oil has found the tiniest area to bleed thru.

[Redneckmech]

Great summary, a couple things to add from personal experience is if you are welding aluminum it can be better to not use a gas lens and instead us a collet body with a #5 cup. This is especially important if you are running a smaller tig welder since the arc will tend to spread out over the area that is covered by the shielding gas, by restricting the shielding gas coverage with the smaller cup and non-laminar flow you will focus the heat into the weld. (This is not to say you cannot weld aluminum with a gas lens, I use it for probably 95% of my welding but I also have a 350 amp machine.). If you need more heat, get a gas mix that has a few percent of helium in it and/or adjust your AC balance slightly negative if your machine will allow it. That will focus the heat more into the weld and less onto the tungsten.

Edit: after thinking about it, the above comment is likely outside of the scope of the aluminum welding needed for the Bearhawk. YMMV

I completely agree on cleaning aluminum... Have a dedicated stainless steel wire brush that is for aluminum only, carbon will contaminate your weld. Clean it with a solvent such as acetone first then scrub it with the stainless wire brush as if you are trying to get it to admit all of its sins against you (it helps if you have been fighting contaminated welds since you will already be ticked off at it). If you can heat it a little bit before wire brushing it is easier to get the oxides off.


Weldmonger.com and furickcup.com are great suppliers. There is no comparison against the cheap gas lenses that you get on ebay or amazon it is a noticeable difference.

[Olm]

Do anybody use "cold welding"? Of course it is not reasonable for fuselage frame but for small parts such as pedals, bellcranks and so on.

[jaredyates]

OA and Tig welding are the only acceptable methods. Most of those small parts are still safety of flight items.

[Olm]

I mean a type of TIG welding, but the parts are not overheated and you have no problem with metal tention(or what they call it(sorry for bad English)) around the welds. Working with inox there is also no problem with metal deformation what is usual when you weld it with TIG. It is good type of welding for thin metals. Example video: https://www.youtube.com/watch?v=9IaLQ5uFLN0