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View Full Version : FINALLY got to use a TIG today! A few Q's



DusterRT
10-13-2005, 07:08 PM
Well, it finally happened! Something worthy of me coming out of lurk mode for, lol. I've been looking forward to trying TIG out for a long, long time. I had a guy run me through the setup of the machine the other day but I pretty well just sat down on my own for a few hours today. This is at the mini-formula shop at my school (SIUC), a couple of the guys are fairly experienced but no resident experts are on hand..anyway.

At first, it was really weird. Not point and shoot like the MIG! It was frustrating at first but I'm starting to get the hang of it (and am glad the grinder is near by for the frequent trips to clean off the electrode). I think I've found a couple things that would give me problems though..

1. I'm welding on .080" wall 4130 tube. I'm told this isn't the easiest stuff to weld..or is it just not the easiest stuff to weld correctly?

2. The filler rod I used for 98% of what I was doing was 3/32" 4130. IIRC, isn't stainless ideal for 4130? And it's way thick..I wasn't too sure about this until I dug around and found an 8" piece of 1/32" rod with "ER70S-2" (stainless?) and proceeded to lay down some extremely impressive beads as compared to what I had been doing. There was some thicker mild steel laying around that I put together with the thick rod and it came out really well. Is this more the change of material, or the thickness? I also tried some .025" MIG wire but it was too thin for what I was doing (it was melting before I could get it to the puddle).

3. The guy who showed me how to set up the welder suggested the gas be set to 35 CFM. This seems pretty high to me, I think I saw TIG-God Matt say he used 15 CFM somewhere?

4. Anyone want to reccomend some welding gloves? The ones we have are bulky, and expecially with the filler rod, make things harder to control. On the other hand, it doesn't take long for that torch to get HOT! I think I now know why people are so big on water cooled units..maybe I'll just get a leftie..

Well that's all I've got for now. I'll get some pics soon if anyone would be interested in critiquing my work..and thanks for any input!

Travis

Matt@RFR
10-13-2005, 08:45 PM
Travis, congrats on the new experience. A tip: Cut your tungsten in halves, and sharpen both ends. Do that to 3-4 sticks, and you will be able to weld for awhile until you've gone through all the prep'd tungsten, then go sharpen all of them again. After you have more practice, you'll be grinding tungsten less and less.

1. Chrome Moly itself is not any more difficult to weld than mild steel, it's just different. (that's what I say about stainless too) It requires less heat input than mild steel, and subsequently requires a very short arc length. The two things that are most difficult to learn. :)

.080" isn't the best to learn on, either, but won't be impossible. Same with round tube. You're doing this the hard way! If you can, find some 1/8 - 3/16 flat bar to practice on. Thicker base metal will be a ton more forgiving with regard to heat input, and will let you use bigger filler, which most guys find easier to use when they're starting out.

2. 3/32 is WAAAAY too big for .080. Way too big. 1/32 would be called .035". And yes, that's the correct size for what you're practicing on. I use .035 filler on base metals as thick as 1/8", and sometimes thicker.

Stainless filler (Ex: ER308, ER316, ER347) is not the best filler for 4130N. Most shops that do that are only looking at the higher tensile strength potential of the weld, but are turning a blind eye to the lack-luster elongation percentage potential. (Meaning it doesn't like to bend) Depending on the intended use for the weldment, ER70S-2, ER70S-6, ER80S-D2 are the most common, with ER80S-D2 being the closest match to 4130N's tensile numbers, while still retaining good elongation percentage potential*. Using stainless filler isn't the choice of well-read fabricators, and is just plain expensive.

There are occasions when 4130N filler is used, but it is required to pre-heat and post weld heat treat (anneal) the weld and the HAZ, or the weld has a good chance of being extremely brittle.

(* I say potential because elongation percentage, when talking about a weld zone, is defined by the amount of dilution between base metal and filler metal, as well as the joint design, and the weld parameters used.)

3. You recall correctly. :) 15cfh is a good catch-all starting point. 35cfh is way too much, and can cause excess turbulance, which can pull atmoshpere into the gas stream and contaminate the weld.

4. Tillman kid skin gloves are the industry standard.

4a. Yeah, air cooled torches do get hot, although it should take quite awhile to get hot when welding .080 steel. You should only be running around 60 amps. The second (and more important to me) reason everybody likes water cooled torches is that they're half the size of an air cooled torch. Once I used a water cooled torch, the next time I picked up an air cooled torch, I felt like a one legged retard trying to swim. I refuse to even touch them anymore.

4b. Pictures!

toxicz28
10-14-2005, 12:05 PM
I felt like a one legged retard trying to swim.

:rotfl: :lmao: THAT is hysterical!!!

Matt@RFR
10-14-2005, 12:37 PM
So I'll be meeting you in hell too? :)

toxicz28
10-14-2005, 04:29 PM
So I'll be meeting you in hell too? :)


If the wife gets her wish, I'll be waiting there for you. I guess I'll hold the door open for you.

DusterRT
10-14-2005, 08:36 PM
Got a little more time in today. Brought my work home and took some pictures..



This is some exhaust tubing I cut for something, and then decided to use something else. So it got put back together. On the left, I used no filler. On the right was my 3rd bead with the lovely 3/32" 4130 rod (all we have at the moment). I'm having troubles working the photos here so each one will have its own reply..critics, fire at will..

https://static1.pt-content.com/images/noimg.gif

DusterRT
10-14-2005, 08:37 PM
Same thing, just 1st and 2nd tries..

https://static1.pt-content.com/images/noimg.gif

DusterRT
10-14-2005, 08:38 PM
...and the inside...

https://static1.pt-content.com/images/noimg.gif

DusterRT
10-14-2005, 08:40 PM
Here I scrounged up a tiny bit more of the ER70S-2 rod.


https://static1.pt-content.com/images/noimg.gif

DusterRT
10-14-2005, 08:41 PM
...and 3. This one I kept going until I ran into the tack.


https://static1.pt-content.com/images/noimg.gif

DusterRT
10-14-2005, 08:42 PM
And a crappy inside shot.

https://static1.pt-content.com/images/noimg.gif

Matt@RFR
10-14-2005, 09:11 PM
First and foremost, that is either galvanized or aluminized tubing, either of which the fumes from welding can KILL you if exposed to long enough. Besides that, you'll never, ever get an exceptable weld without first grinding the coating off. To be honest, I'm amazed you got that far. This especially applies to TIG.

Obviously the .035 filler is working much better for you. It looks like you're pushing the filler into the puddle in one continous motion, correct? If that's the case, there's no need for it, and consistent beads will be much harder with that technique. If you're not doing that, you should try spreading your filler deposition apart some.

The inconsistent penetration could be a combination of several things:

Inconsistent torch travel / lean angle
Inconsistent arc length
Inconsistent amperage via working the pedal too much (arc length
also has an effect on amperage)
Filler deposition timing and amount effect penetration, and also has
a cooling effect on the puddle

Other than that, it looks like it's just a matter of practice, and making sure you're good and comfy when welding. If your back hurts (etc.), your welds will reflect your pain.

(Edit) One last thing: You need to try and get in the habit of not slamming the pedal off when you finish a weld. As you're adding that last little bit of filler, start backing off the pedal, and you won't get those craters.

DusterRT
10-14-2005, 10:12 PM
It's hard to see, but I took the aluminizing off with a wire wheel in a die grinder about 3/4" out from the seam..or did I only think I took it off? Is that white ring the aluminizing? Yeah..I'm gonna try to avoid killing myself doing this, lol.

The way I've been working the filler is I let some of the base material pool up and then I add some filler..though I'm not 100% consistant with how much filler I add yet. Is the idea to leave a glob that you drag out or keep a consistant pool size as you move? And as you move, are you supposed to go smoothly in one motion (what I've been doing, or trying to at least)?

And yeah, you got that right..my back has been killing me. The steel workbench is occupied by a frame and a bunch of smaller mini-projects, I'm working off the corner sitting on a stool that is too tall so I'm hunched over as well. I'll hopefully have more room after this weekend.

Ahh yes!! Those craters. I've been wondering about those but forgot to mention it.

Your tip of double pointing a few electrodes was great advice. Made things a lot less frustrating not having to get up every couple minutes!

Something I was wondering about was a couple of frame failures on last year's car. In the back connecting to the engine "cradle" they had a couple 4130 tubes welded to (I think) mild steel square. Both tubes on both sides broke clean in two about 3/4" away from the weld. I wasn't around when it happened though so I don't know if it was just from long term vibrations or if something gave the frame a good jolt. What would be some potential causes for a failure like that? I don't have any pictures unfortunately, and the tubes were replaced a while ago..

All things considered I'm pretty happy with my progress. Going back for more tomorrow afternoon...:icon996: thanks a million, Matt!!

Travis

Matt@RFR
10-15-2005, 09:15 AM
Well, I have to fess up. I have no idea if welding aluminized tubing will have any ill effects like galvinized does, and an internet search of my regular suspects didn't reveal anything. However, it won't help the weld any. There's evidence in your pictures that you didn't get the coating off, and that is definetely messing you up to atleast a small degree. MIG wouldn't care, but TIG does.

Now that you point it out, I can see where you stopped with the wire wheel, but like I said, the coating is still present. You'll have to grind or sand it off until you have shiny silver metal. Keep in mind, too, on thin weldments like this that when you get full penetration, any coating on the inside of the tube will be pulled into the weld. Yippie! I know, I know, but to do this right, you're gonna have to grind the inside too.


The way I've been working the filler is I let some of the base material pool up and then I add some filler..though I'm not 100% consistant with how much filler I add yet. Is the idea to leave a glob that you drag out or keep a consistant pool size as you move? And as you move, are you supposed to go smoothly in one motion (what I've been doing, or trying to at least)?
To illistrate, look at the attached picture. That was done in a positioning table (lathe chuck attached to an electric motor), the torch was held stationary, and filler was added at equal intervals. So, yes, the torch movement should be a steady forward progress. The filler deposition is what gives you the 'look'.


Something I was wondering about was a couple of frame failures on last year's car. In the back connecting to the engine "cradle" they had a couple 4130 tubes welded to (I think) mild steel square. Both tubes on both sides broke clean in two about 3/4" away from the weld. I wasn't around when it happened though so I don't know if it was just from long term vibrations or if something gave the frame a good jolt. What would be some potential causes for a failure like that? I don't have any pictures unfortunately, and the tubes were replaced a while ago..
This could've been the result of a poor design, but for the sake of discussion, assuming the failure was weld related, it would point to a too-hot weld. Chrome Moly is very sensitive to heat input, and if the heat input is too high, it will get brittle unless post weld heat treatment has been performed. Being that it broke that far away from the actual weld, that would point to a brittle HAZ (heat effected zone). A 3/4" HAZ is HUGE for small 4130N tubing, which, again, points to too much heat. It most likely broke at the edge of the HAZ, where the base metal transitions from it's normal state to heat effected state.

68protouring454
10-15-2005, 10:09 AM
matt you really are my hero, how do you do it? how do you even breath you are out of this world

MrQuick
10-24-2005, 02:48 PM
Matt=show off, Jake = suck up..heeee heee j/k....i have a question but will start a new thread.