# Okay, new discussion: welding

## Which way to weld 4130 steel?

• ### Other

• Total voters
156

#### wsimpso1

##### Super Moderator
Staff member
Log Member
Qualified answer - If I were building a tube and fabric airplane, I would obtain a TIG type welder. Being as I am building a fiberglass bird and so I have only a limited number of welded pieces, I have an Oxy-Acetylene setup. The O-A will work, but will require more skill and a lot more practice before you can produce good results. You may also find a need for O-A for other purposes too.

Billski

#### Mike Armstrong

##### Well-Known Member
Qualified answer - If I were building a tube and fabric airplane, I would obtain a TIG type welder. The O-A will work, but will require more skill and a lot more practice before you can produce good results. Billski
Thanks, I seem to hear that alot lately.

A-O is a time proven technique, no doubt about it. TIG seems to have taken it's place as the new, modern (read:Cool) and easier way to weld 4130. At events like Osh, A-O is kinda the good 'ol timers way of welding, TIG is the buzzword and the 'gotta have a shiny new one in my shop' way of welding.

I think the advice to try them both and do the one that you do best is the best course of action.

Mike

#### steveair2

##### Well-Known Member
Log Member
I gas welded mine. The hundreds of tack welds needed to tack my fuse improved my welding skills. I then welded from firewall to tail post.
Welding started good and improved as I went.
This prepared me for the wing attach fittings.
I went to Sun-N-Fun last summer. I intended to try tig while I was there. On my way to the tig tent I just happend to walk past the gas tent. I stopped to look inside and found out how to gas weld aluminum!
I never made it to the tig tent. I like gas welding.

Steve

#### Roger Miller

##### Member
While your on the subject... How do you gas weld Aluminum? I tried once with NO luck.

Thanks,
Roger

#### Peter V

##### Well-Known Member
It's all about that flux. Aluminium needs to be oxide-free to weld, but it oxidises in under 5 seconds. The flux acts as a cleaning agent. Not sure it would be much of an O2 barrier as in stick welding. But it must be doing something, because the gas from your torch is not inert enough on it's own to shield the weld pool.
TIG uses AC pulses to blast the metal clean and pure Argon as a shield. Even adding as little as 20% CO2 to this will give you crap results (yeah, been there. MIG gasses are no substitute:emb.

#### Craig

##### Well-Known Member
I have brazed aluminum with O/A, correct rods and flux - works well, and is not too difficult. You really have to watch how close your flame comes to the aluminum, however, as holes can "magically" appear if you reach the melting point of the aluminum.

I've not been brave enough to try actually welding the alum with the O/A torch yet. Plant to get a nice TIG outfit for that!

#### Peter V

##### Well-Known Member
Little trick with aluminum: run your torch over it with the oxygen off to make it sooty. By some freak of coincidence, soot burns off at exactly the right pre-heat temperature for Aluminum, so you'll know when to stop heating and not burn holes in it.

#### steveair2

##### Well-Known Member
Log Member
George Biang gave an exellent forum at Sun-N-Fun last summer. He talked about gas
welding aluminum and fuel tank construction.

We used #3 tint lenz with cobalt blue filter (photographic stuff)

We used 5356 rod on 5052 aluminum.

George sells flux that he recommends.

After watching him, I made a pretty good weld on my first attempt.

I plan on gas welding my fuel tank when I get to that point. Summer I hope!

Steve

#### base363

##### Well-Known Member
This is from a post I made quite a while ago:

If most people are like me, (and for your sake, I hope your not!) they will try to rationalize their way into gas welding because of the cost of the TIG machine.

What I suggest to the undecided, is to purchase the Gas set-up and start practicing. You need a torch anyway, and the physical techniques of dabbing in the rod are identical.

Then, when you realize that you won't really be satisfied until you have the TIG Welder at your house, you will find a way to buy it!

Once you do, you'll never look back. And you'll still have the nice Gas rig you always needed too!

Colin
http://www.jumprunenterprises.com

#### Mike Armstrong

##### Well-Known Member
This is from a post I made quite a while ago:

If most people are like me, (and for your sake, I hope your not!) they will try to rationalize their way into gas welding because of the cost of the TIG machine.

What I suggest to the undecided, is to purchase the Gas set-up and start practicing. You need a torch anyway, and the physical techniques of dabbing in the rod are identical.

Then, when you realize that you won't really be satisfied until you have the TIG Welder at your house, you will find a way to buy it!

Once you do, you'll never look back. And you'll still have the nice Gas rig you always needed too!

Colin
[URL="http://www.jumprunenterprises.com"]http://www.jumprunenterprises.com[/URL]

Thats exactly what I'm doing. Also, I enrolled in a Community College welding course that teaches you both Gas & TIG. I bought some 4130 thin walled tube and some scrap thin steel plate to practice dabbing puddles on at home using my O/A setup I got from Tinmantech. I'll buy a TIG welder later.

Mike

#### Jephthah

##### New Member
I've been a lurker here for a while. Guess I'll chim in. TIG was invented for aircraft construction. "The TIG or GTAW, process was invented by the welding department at Northrop Aircraft Company in 1939-1941." See: www.techtorch.com It is NOT a new fangled thing. Over 60 years in existance, it is the method to use if you have the money and want a low distortion, consistant, nice looking, quality weld. I quizzed over a dozen professional welders, ALL recommended TIG for welding thin wall 4130 in a aircraft application. Every homebuilder I have talked with that went the TIG direction was very satisfied and upon looking back, glad they went that route.

The following is taken from: http://home.hiwaay.net/~langford/sportair/

"I'll try to hit the highlights here. When TIG welding thin-wall 4130 tubing, no preheating is required, other than bringing it up to room temperature and ensuring that no obvious moisture is present on the tubing. Likewise, no "post heating" or normalization is required either, but a draft-free work area is important. Keeping the weld bead as small as possible is best, in order to minimize the heat-affected zone. The best welding rod to use is ER80S-D2, ER70S-2, -3, or -6, in that order. There's nothing wrong with copper coated rod, which prevents the rod from rusting. Make sure you wipe the oils (used in manufacturing) off of the rods first. .045" diameter rod is best for thin-wall, but it's not commonly available. If you can't find it, visit Wyatt's web page at and he'll sell you small or large quantities. (Mention you're with the EAA and you'll get a 25% discount.) Tight fit-ups are of paramount importance when TIG welding OR gas welding. The tighter the joint, the less distortion you'll encounter as the structure is welded together.

There is an age-old debate regarding which is better for welding 4130, gas or TIG. I'm here to tell you that I'll never be able to gas weld 4130 with anything near the confidence level that I can TIG it. I have no doubt that someone with years of experience can gas weld 4130 just fine, but if you want joints with the same high quality (and a smaller heat affected zone) with minimal practice, TIG is the way to go! It costs more to "get in", but it sure is easy to pick up TIG welding. There are no real variables. Just step on the pedal until it melts into a puddle, and feed it the rod. With gas welding there are so many variables. Tip sizes, oxy-acetylene ratio, etc. I never could figure it out. I proudly took an early gas attempt to the local guy that does all the certified aircraft welding for the FBOs. He just sighed and said "I'm sorry, I thought you were further along than this. You've just cooked the hell out out of it".

Much of the argument against TIG welding steel have come from the gas welding camp, who are fond of breaking TIG joints welded with "official" 4130 rod. This high carbon rod is very brittle and prone to cracking when allowed to cool quickly, as most homebuilders would tend to do when welding thin-wall tubing. 4130 steel is normalized by a carefully controlled slow-cooling process during manufacture. So when you heat it up and let it cool at room temperature, it's very strong, but far more brittle. That's why milder steel rod is best for our thin-wall application. It's far better to have a slightly weaker joint than to have a brittle one with cracks in it!"

Meet Meet Mr Tig: www.tigdepot.net/meetmrtig.php

TIG Database: www.tigdepot.net/articles.php

I just ordered the DVD, but have not viewed it yet.

BASICS OF TIG WELDING DVD:www.tigdepot.net/products_details2.php?productid=87

I think every homebuilder should at least give TIG a chance before deciding. When I build my homebuilt I will use TIG.

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#### Peter V

##### Well-Known Member
Oh no, now you've done it.
the two camps were at peace for months, and now you had to go and wizz on their 'fire'. :gig:

#### Mike Armstrong

##### Well-Known Member
Thanks Jephthah.

I don't think I've spent more time researching and flip flopping 'final' decisions more than with this Gas vs TIG quagmire (well, with exception to which aircraft I decided to build). It's absolutely true that either method can give you an airworthy weld on 4130 tube. As has been suggested, I too think a builder should try both techniques and decide for themselves which one suits their skill set best. Whether you use one or the other does not matter as long as the end result is the same, a good weld.

I'm going to try to keep an open mind as I work on the basic skill of puddle dabbing using my Gas rig. In a couple of weeks my instructor is going to introduce the class to TIG. It will be interesting to see the difference in the quality of the weld produced.

Mike

#### PTAirco

##### Well-Known Member
I have never tried TIG. I used to be certified to (gas) weld on airplanes - sorry, aeroplanes - in Britain where they make you do a test before you can do anything, even on homebuilts. You have to weld certain samples (tube to tube, straight and angled, tube to sheet etc) which are then cut open, examined, x-rayed, put in a tensile test machine, bent, hammered flat and generally abused and hacked apart. If the numbers are within specs, you're free to go and weld. One point I would like to make is: there is no difference in the strength of a weld wether it is made by gas or TIG. The tests they are put through are the same and the expected results and numbers the same. I have heard some less well informed people (not in this forum, of course!) claim that TIG somehow produces a "stronger" weld. Not so.

They do look pretty, though! But I like to think on a good day with my trusty Henrob (Dillon) torch I can compete with the best of them. The pic is a random sample pulled from my "odds&ends" bin and looks pretty nice to me....

#### PTAirco

##### Well-Known Member
but the biggest issue i've heard of is carbon deposits in the weld, making it stiff and brittle. 4130 is an alloy of steel, chromium and a few others in much smaller quantities. the addition of carbon COULD cause significantly brittle welds.
Im sure they both could work, but my life isnt worth the \$500 bucks saved if it came down to the strength difference between the two.
The fact that there are aircraft flying that were gas-welded in the 1920's and before should be enough testimony that that process produces first-class, reliable welds. I have had gas welds tested, x-rayed, hammered, stretched, pulled apart, bent and otherwise abused and the bottom line is: it works. It works great. I would happily trust my life to a gas welded joint the same way pilots have been doing for nearly 100 years.

It does require skill to make a decent weld with a torch, but TIG does not compensate for sloppy welding practice.