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Old 08-02-2012, 05:02 AM   #2971
DaBit
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I have welded aluminium using DC- in my home garage. To cope with the oxide I used an aluminium gas welding flux (SIF number 36 if I recall correctly).

The first experiment ever. No aluminium experience, no filler / autogenous weld, 6060 material.



Advantages of DC- and flux:
- It can be done for incidental aluminium welding and works OK if you're not after the most beautiful welds ever.
- Less welding current is needed because the heat end up in the workpiece instead of causing a orange glowing tungsten and the arc from a pointed electrode at DCEN is more concentrated than an AC arc. 120 amps of welding current is sufficient up to approximately 5mm thickness.

Disadvantages:
- While welding the very bright yellow sodium flare (brighter than the actual welding arc) makes that you must use a 1-2 shades darker helmet, which doesn't exactly improve the visibility of the puddle. Of course you could use an extra filter to cope with the sodium flare, but they are expensive.
- Especially when beginning the weld the flux obscures the puddle. After 1/2"- 1" this improves and there is a clean puddle surrounded by flux like a mountain like surrounded by mountains.
- When stopping the arc the flux residue solidifies, and HF won't strike through it. You must start the arc somewhere else and move back to the weld.
- The cup and tungsten become dirty quickly.
- Vapours escaping from the weld zone smell quite bad, and they probably are.
- The flux residue is agressive and very hard to clean.
- Mixing flux with water, applying a light coat to rod and workpiece and cleaning afterwards takes far more time than the welding itself.

If I had not modified my (DC) TIG-welder to AC-capable, I would still be doing it this way. I'm not welding enough aluminium to justify spending $2000 on a decent AC-TIG machine, and for the average bracket etc. it is more than good enough.
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Old 08-02-2012, 05:09 AM   #2972
Guy Young
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Originally Posted by David R View Post
I disagree. Tig alumium for the average Joe or even a regular welder is AC. It can be done with DC but has no cleaning action. The aluminum oxidizes instant from the atmosphere so no matter how well you clean it, the oxidation comes right back. The AC removes the oxidation as you weld. Can it be done? Uh huh, is it practical Not for repair welding. In specialized shops, or manufacturer sure.

TIG DC + takes a huge tungsten. Tig DC- has no cleaning action. You can't get through the oxidized layer and if you get it hot enough, the layer just sits there on top of the weld or work piece making it hard to weld and get the filler to flow.

The helium part is totally correct. Argon is heavier than air so it works better. Helium creates about 5 more volts in the arc so it welds hotter. Helium costs more and takes more Cubic Feet Per Hour because its lighter and does not stay at the weld. I think its with a little less control, but I use it on bigger stuff, so it doesn't matter.

Stop in any local shop and ask them if they TIG weld aluminum with DC. To weld cast aluminum or something not new and perfectly clean, not a chance.

MIG is DC+ on aluminum and that gives the cleaning. Most DC wire feed (mig) aluminum is spray arc.

This was done AC, 190 amps with a bunch of preheat first. The block on the end is solid, the tube is about 5/16" thick. With out 75/25 HE/AR, and preheat, I could not have welded it.

If you look at the weld, there is a white band along side. This is where the + part of the wave cleaned the oxide off the metal while I was welding it.

This is the preheat. Ihave posted this picture before, but it gives an idea of the size of the piece. I did 22 of these, all welds were vertical up (3f)
That was a hellava chunk of metal.

When you did the preheat, what temperature were you looking for before you started your weld??

.
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Old 08-02-2012, 11:44 AM   #2973
liquidsmile
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I have a questions, I just purchase a used powder coating booth. The booth itself is in good condition and is made up of stainless steel. I am the third person to purchase this booth and the second person who purchased it widened the booth. The floor now has 3 pieces of stainless steel running the length of the floor.

The stainless is a 1/4 inch thick and we are having a hell of a time welding up the seems to make a smooth surface that is easily cleanable. We have our welder turned down as much as possible and the heat is still causing the steel to warp making it almost impossible to accomplish the desired outcome.

Like I said the seems run the entire length of the floor, 2 seems in total. Basically they widened the paint booth and put another piece of stainless steel down the center of the floor to cover the hole that was made when they widened the booth.

I found some Stainless Steel putty made by Devcon, and was wondering if anyone here has actually ever used the stuff.

What I am trying to accomplish buy buying this is to smooth over the seems making the booth easier to clean. Think Bondo, but for stainless.

Here is what I am thinking about buying. http://www.devcon.com/products/produ...m?familyID=105

Short of order a large piece of Stainless, does anyone else here have any other suggestions?
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Old 08-02-2012, 12:59 PM   #2974
David R
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Quote:
Originally Posted by Guy Young View Post
That was a hellava chunk of metal.

When you did the preheat, what temperature were you looking for before you started your weld??

.
From Star Treck "I'm giving her all she's got Captain"

I just watched the clock. 3 minutes was not enough for that piece, but too much for one of the smaller pieces on the same job. More like 4.5 minutes with that torch which is supposed to be 500,000 btu. Not really sure, its a propane weed burner. I will guess 450*f. I just heated it until it welded properly. When doing aluminum and everything is right, you go pretty fast dipping the rod and moving along.

I have a laser type temp gun. It goes up to 500*f, BUT it reflects on shiny plate so it does not tell the truth. I would have to dull a spot or paint it black. Not on that job....

David
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Old 08-02-2012, 01:11 PM   #2975
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Quote:
Originally Posted by liquidsmile View Post
I have a questions, I just purchase a used powder coating booth. The booth itself is in good condition and is made up of stainless steel. I am the third person to purchase this booth and the second person who purchased it widened the booth. The floor now has 3 pieces of stainless steel running the length of the floor.

The stainless is a 1/4 inch thick and we are having a hell of a time welding up the seems to make a smooth surface that is easily cleanable. We have our welder turned down as much as possible and the heat is still causing the steel to warp making it almost impossible to accomplish the desired outcome.

Like I said the seems run the entire length of the floor, 2 seems in total. Basically they widened the paint booth and put another piece of stainless steel down the center of the floor to cover the hole that was made when they widened the booth.

I found some Stainless Steel putty made by Devcon, and was wondering if anyone here has actually ever used the stuff.

What I am trying to accomplish buy buying this is to smooth over the seems making the booth easier to clean. Think Bondo, but for stainless.

Here is what I am thinking about buying. http://www.devcon.com/products/produ...m?familyID=105

Short of order a large piece of Stainless, does anyone else here have any other suggestions?
The joint to be welded is a corner, butt, or lap? If it is a corner, are you welding the inside or the outside of the corner? Stainless warps like crazy, so much so that some times you need to place a tack weld every 1/4 to 1/8 of an inch (or even less) before welding the seam. Be sure you get ALL of any powder coat residue off of the material to be welded before tacking up.
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Old 08-02-2012, 02:42 PM   #2976
jgrady1982
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MillerMatic 130 Question

Hello,

I want to make a mobile base for an Index mill that my father is going to give to me. I have found some pictures of what I want to build online and I am going to use 3-4" 1/4" steel angle iron followed by some 1/4 plate to secure the casters.

Will my welder be enough? I have converted the welder from a flux core to a full MIG with 70/30 or 80/20 gas...I think, I cannot remember the exact combination.

I have a professional welder that I can use if needed, I am just trying to keep costs down with this project.

Thanks,
Jack
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Old 08-02-2012, 02:54 PM   #2977
Guy Young
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Quote:
Originally Posted by David R View Post
From Star Treck "I'm giving her all she's got Captain"

I just watched the clock. 3 minutes was not enough for that piece, but too much for one of the smaller pieces on the same job. More like 4.5 minutes with that torch which is supposed to be 500,000 btu. Not really sure, its a propane weed burner. I will guess 450*f. I just heated it until it welded properly. When doing aluminum and everything is right, you go pretty fast dipping the rod and moving along.

I have a laser type temp gun. It goes up to 500*f, BUT it reflects on shiny plate so it does not tell the truth. I would have to dull a spot or paint it black. Not on that job....

David
LOL!

Appreciate it. I was just curious.

I found that my laser thermometer works pretty well on reflective stuff. I use it to gauge the temps of Parkerizing fluids before I stick in the gun parts. I was a little skeptical at first, but found that it gave a pretty true reading for what I was doing.

Again, thank you. I seriously doubt that I will ever be doing anything that "robust," but still gives me some guidelines to go by.

.
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Old 08-02-2012, 03:16 PM   #2978
fxstbiluigi
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Quote:
Originally Posted by liquidsmile View Post
I have a questions, I just purchase a used powder coating booth. The booth itself is in good condition and is made up of stainless steel. I am the third person to purchase this booth and the second person who purchased it widened the booth. The floor now has 3 pieces of stainless steel running the length of the floor.

The stainless is a 1/4 inch thick and we are having a hell of a time welding up the seems to make a smooth surface that is easily cleanable. We have our welder turned down as much as possible and the heat is still causing the steel to warp making it almost impossible to accomplish the desired outcome.

Like I said the seems run the entire length of the floor, 2 seems in total. Basically they widened the paint booth and put another piece of stainless steel down the center of the floor to cover the hole that was made when they widened the booth.

I found some Stainless Steel putty made by Devcon, and was wondering if anyone here has actually ever used the stuff.

What I am trying to accomplish buy buying this is to smooth over the seems making the booth easier to clean. Think Bondo, but for stainless.

Here is what I am thinking about buying. http://www.devcon.com/products/produ...m?familyID=105

Short of order a large piece of Stainless, does anyone else here have any other suggestions?
By turning the amperage down on the machine you have increased the time it takes for the parent material to become hot enough to accept the fill wire. Thus increasing the total heat input.
Turn the amperage up to a point that your travel speed is fairly rapid and use a technique called "back stepping"
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Old 08-02-2012, 04:29 PM   #2979
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Thanks for your replies. I am not actually doing any of the welding. I hired an old friend who is a retired welder. We are using a mig and he chose the wire and the gas that we are using. I am going to give this devcon stuff a try and see how it goes.

I will talk to him tomorrow about trying to turn the welder up and back step it. Believe it or not we tried some JB Weld just to see how it would look, and it is seeming to do the trick.

I really just want to make the floor smooth where it will not hold any powder paint in the grooves that are currently there.

I will take some pics and post them up tomorrow.
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Old 08-02-2012, 04:41 PM   #2980
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If the stainless floor is already on another floor why weld it?
Fill the joints with some type of epoxy and be done with it.
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Old 08-02-2012, 05:30 PM   #2981
liquidsmile
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Quote:
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If the stainless floor is already on another floor why weld it?
Fill the joints with some type of epoxy and be done with it.
Well it was spot welded in places. I was just trying to have the gaps filled where it was not welded. That is pretty much the conclusion I have come to as well. I ordered some of the Devcon today from Grainger. Hopefully it will be in tomorrow and we can get this finished.
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Old 08-03-2012, 06:35 AM   #2982
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Devcon isnt likely to work..........its going to crack and fall out almost certainly. You would probably get good results from stitch welding the sheets together leaving 1ft gaps, grinding off the finished welds, and using maybe flexible heat resistant silicone sealer to deal with the gaps.
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Old 08-04-2012, 11:51 AM   #2983
Illiumrider
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Ive searched the tread and still have a question. Im looking to attach some casters to the legs of a stainless steel commercial kitchen table. The legs are 1 1/2" tube, prob 304?? The casters have 3" threaded rod. Anyways I am going to weld a nut in the center of a large fender washer with the OD of 2". I am gonna weld that fender washer to the bottom of the tube, and it will leave me 1/4" on the sides for weld. I picked up some 3/32" 309 electrode. Any ideas/thoughts/tips on welding mild steel to stainless tube???? Amperage/polarity?

Thanks all
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Old 08-04-2012, 02:14 PM   #2984
David R
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Originally Posted by Illiumrider View Post
Ive searched the tread and still have a question. Im looking to attach some casters to the legs of a stainless steel commercial kitchen table. The legs are 1 1/2" tube, prob 304?? The casters have 3" threaded rod. Anyways I am going to weld a nut in the center of a large fender washer with the OD of 2". I am gonna weld that fender washer to the bottom of the tube, and it will leave me 1/4" on the sides for weld. I picked up some 3/32" 309 electrode. Any ideas/thoughts/tips on welding mild steel to stainless tube???? Amperage/polarity?

Thanks all

It should say on the rod package suggested amps. Start low. DCEP unless stated other wise on the package. Keep the heat low to start. How thin are the tube legs?

David
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Old 08-04-2012, 02:31 PM   #2985
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Thanks DavidR. Much appreciated. As far as the thickness, I am not sure. They are legs for a commercial stainless table.....If I had to guess Id say maybe .075?
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