TIG welding diff thickness Aluminum 2

[camfambmw540]

Hello all,
I am trying to TIG weld a 1/16 " aluminum tube to a 1/4" aluminum plate (actually there is a 2" diameter hole in the plate that the tube fits into...) and I am having troubel...can anyone assist me with some pointers, tips, sites to check out, etc..../

I would really appreciate it

John

 

[Goahead]

You probably burn off the thin tube while the heavy plate does not even start to heat up. The difference in size is too large. Could you machine in the plate a butt joint of same thickness as the tube, down to half the plate thickness? Otherwise you would be better off by brazing. Or by friction welding (not available, I know).

http://www.welding-advisers.com/

 

[CWIC]

camfam:
Joining these thicknesses is achievable by a seasoned welder. Technique is the key. More info provided can help to help you.
1. What type of welding power source is being used or intended to be used?
2. Electrode and/or filler metal classifications?
3. Composition of shielding?
4. Position of welding?
5. Welding parameters (amps, type of current, pulsing, etc.)
6. What specific "trouble" are you having?
a. Burning through the tubing?
b. Warpage?
c. Weld and/or base metal cracking?
d. Color matching?

 

[camfambmw540]

Wow, nice credentials (CWIC), I am impressed. I appreciate, as well as the 100 or so others you have helped, your time and energy.

1) I am using a Lincoln Electric Square Wave 175
2) 3/32 98 % tungsten, 2% thorium (sp?)
3)100% argon
4) Don't know what you mean, the pieces are flat on welding table (it's an intake manifold)
5) AC (obviously) set amp to 175 and use pedal to moderate power flow
6) I can’t get the two parts to meld without either causing a concave channel to form on thicker plate 9unatractive in appearance) or a burn through on 1/16 inch tube. To clarify, I purchased the TIG three weeks ago and it is probably my lack of skill (not, as you refrenced, a seasoned welder..4-5 months with OXY is about it). I am turning to you folks for tips to cut down my "boy was that stupid" time

As a not, I think I should (have ordered them0 use 100 % tungsten tips, my filler is 1/8 4xxx standard filler from weld shop). Aluminum is 6061

Any (further) help would be greatly apreciated.

John

 

[CWIC]

camfam:
1) Your Lincoln power source is probably working on the upper range of the machine, particularly using AC current. Goahead's comment is very applicable at this point; "You probably burn off the thin tube while the heavy plate does not even start to heat up."
2) I would get your hands on some 100% pure tungsten (AWS classification EWP, which should have a green color band.) This should help out some. The 2% can be used, but you will notice a difference particularly at lower amperages.
3) DC welding is very common with GTAW of aluminum. It takes practice and a different shielding gas (helium), or a helium rich gas mixture is required.
4) It sounds as if you are welding in the flat position.
5) See number 3. If you go to DC - straight polarity, you can optimize the output of your machine. The entire process will be much more efficient, but it takes more practice and some coaching.
6) It sounds as if your undercutting on the thicker member. Did you try preheating the thicker member before welding? It does not take much, maybe 200 degrees F. Do not overheat the part! Do not preheat the tubing, it won't require it.

*Try going down one size (3/32" diameter) in filler material, it will take less heat to melt the filler metal.

*You just bought the machine, it does take practice, lot's of it. The materials, thicknesses and joint are such that even a "seasoned" welder would have problems unless he/she welded these regularly.

*Practice on scrap materials of the same thicknesses and not your part.

*Practice, practice, and more practice... All the posts in this or any other forum can't help you without more...

 

[CWIC]

p.s.:
I would not consider learning to be "boy was that stupid time." We all had to learn to crawl before we could walk, walk before we ran, etc. Don't expect so much so soon, it is an acquired skill that takes some months, years or an entire lifetime to learn and master. Your at the "puppy" stage, soon you'll be running with the big dogs...

practice........

 

[camfambmw540]

CWIC,

I have a question for you: You reference that I can use DC with Helium. I have practiced for the last week or two with little success (which is fine, I fully understand the learning curve issue), but, are you suggesting that I get helium and try DC welding of Aluminum? You mention that "The entire process will be much more efficient, but it takes more practice and some coaching". What do you mean by coaching, how/where would I get this coaching and when you say "take more practice" are implying that it is more difficult (the true issue for me) or, just different than AC with 100% Argon?

Sorry to have so many questions, but please know I am very appreciative of any help you can provide.

John

 

[camfambmw540]

One more Idea..is there a easier combination of Aluminum class (6xxx, etc) that is easier to work with in combination with a particular filler rod to make the entire process easier to tackle? I am using 6061 now.

Thanks again

John

 

[funnelguy]

camfambmw540,
1. Is the 1/4" flange laying flat against a steel welding table? The table will tend to sink out heat, making your job that much more difficult.

2. Could you increase the wall thickness of your tube to say 3/32? I think that would help more than you would think.

3. I hope you are not doing all of your practicing on this combination. Start off with easy welds and work your way up.

4. It would be helpful for you to watch an experienced welder make the weld and talk you through it. Try to find a willing coach.

5. You are using gold lenses, right? No coffee and quit when you get frustrated. Best of luck!

 

[CWIC]

cam:
Using DC is another technique for joining aluminum. It is commonly used in the aircraft/aerospace industries. I mentioned this technique due to the thicker member involved with your project and the rated output of your machine. DC current will require less amperage from the machine, arc travel speed is increased - increasing process efficiency. If you are still struggling with AC and the Ar gas shielding, you are not ready to step up to DC welding.

Coaching: This term is self explanatory. You need practicle (hands on) help from someone who is proficient with GTAW on thick/thin aluminum. You won't get this help through a computer (this or any other forum) as I previously noted.

6061-T6 is one of the most common of the 6XXX series of Al alloys. This material is alloyed with Mg/Si, T6 is heat treated and artificially aged. ER4043 can be used as well as a number of other filler materials. ER53656 would be used to increase tensile strength of the weld metal and aid in color matching if anodizing is in the future for the part. If this material is overheated, (too high preheat and interpass temps., welding and/or rewelding at any given location for extended periods, etc.) will dramatically reduce the strength of the base metal and surrounding area (HAZ). Using another Al alloy/filler material combination will not increase your welding skills.

 

[PaulRBrown]

You will run into problems trying to use DC electrode positive with the amount of current the electrode can handle, it will be 1/10 the amount that DC electrode negative can use, but you need to use electrode positive on Al for the effect it has of removing the Al oxide layer, that is why AC is used as you get the higher amperage of Negative and the oxide removal of Positive. The machine is usually in the negative side for about 60 to 65 percent of the time.The reason for using Pure tungsten is the way the ball forms on the tip of the electrode, 2%thoriated has spikes shoot off its ball and is not very controlable, Zirconiated [brown marking] can give as good a ball as pure and also can handle the same amperage as thoriated[50% more than pure tungsten for the same size]you should probably step up to a 1/8 inch electrode for its ability to handle more amperage. The other thing about Al Welding that is extremely important, Cleanliness, just before welding, scotchbrite the surfaces with scotchbrite that has only been used on Al, then clean with acetone,laquer thinner,xylene, or the best according to ESAB welding[the people who invented tig and the covered smaw electrode]is toluene, avaiable at better paint stores. this evaporates the quickest.Don't forget to scotchbrite the rods also, and degrease. make sure your gloves are very clean also, the least bit of grease will cause mayhem. The talk about helium is a good suggestion, helium makes the arc hotter/more powerful, a 50/50 argon helium mix works great, I know when I was learning I had lots of problems with Argon, tried some 50/50 and man what a difference. it does cost about 75% more though. Your flow also has to be higher due to the helium floating up, argon is heavier that air so it hangs around the weld better except on overhead. Good Luck, Paul

 

[camfambmw540]

Paul, thanks for the helpful ideas. I will check out the 50/50 blend. I'll get back to you all with an update in a week or so.



John

 

[griffengm]

One technique I've used when faced with widely mismatched material thicknesses is to cool the thinner piece. Usually helps to reduce distortion. On occasion, we set damp clothes on the thin section to pull away some of the excess heat. Other times made cooling coils of copper tube and set the thin section on the coils, sometimes the coil on the section.
Never tried it on Al (mostly SS sheet to heavy flanges and CRS sheet to schedule 80 pipe) but this sounds like a situation where it might work.