Advise on MIG welding please

[Gerry]

Need some help please.
MIG is not my choice of welding method although I do use it now and then.
Question is: I have been advised that MIG is probably the best way to go for the welding on my fuel tank. Its made of 2mm thick MS and does benefit from most of the parts being formed with a fold in them. Reason I have been told to use MIG is that it puts less heat in and so should minimize distortion. So can you guys give me an idea of the amperage, wire thickness and speed that would be a good starting point. I really dont want to go the TIG route as I think it will take many hours to do all the weld. There is about 200 inches of weld on the tank alone.
Any help appreciated.
I was trained on Arc, TIG and gas but not MIG so my experience with it is limited. I find the weld always seems to build too much, giving a high bead. Not what i want on the seams of the tank.
Gerry

 

[ruggs]

Gerry,
After all the time you spent forming this tank, is now really the time to change to MIG? I would personally put some x-tra padding on my stool and spend alot of time at the bench with my tig....ruggs

 

[putz]

The biggest problem is every welder is by 1-5 numbers in heat ranges not amps and wire speed is so variable. Some welders you touch wire soeed and it flys out. What brand and model of welder do you have? that might help somebody with advise.

 

[Gerry]

150 amp SnapOn., Variable wire feed
G

 

[Youngster]

Gerry,
If you want a seam that you can leave pretty much alone and go right to a finish, MIG is probaly not your best choice. From what I've seen of your TIG welding skills, I would agree with Ruggs. Just stay with mild steel filler if you are going to plate it later. If you are still set on using a MIG, most machines come with a chart that gives you start settings. here's some random thoughts on tank welding;

1.Cut your self a bunch of 6" practice sheets and have at it. I would suggest welding in a downhill position at about 30 degree lean back, with as little pausing as posible. Your puddle will want to run away from you so you need to get to where you can stay ahead of it and still have penetration. You want heat but not a lot of wire to make a nice, leak free, good appearing weld.

2.When practicing try to set gaps at the thicknesss of your wire. Tack with your Tig to keep them as small as possible and about 2" to 3" apart.

3.Also try practicing with no gap, some have better luck that way.

4.As you probably know a chill bar on the inside of the long beads on the ends will help keep distortion at a minimum.

I hope this helps you deside which way to weld your tank. If you have any more questiona please don't hesitate to ask.

Ron

 

[ruggs]

Gerry,
As youngster said.....Here is a website that has a calculator for MIG, My link
It should get you in the ball park you'll just have to adjust up or down and check penetration....ruggs

 

[Ted Brown]

Myself, I would use the TIG, go slow and not long in any one place, keep it all cool, end up with it tacked everywhere, but do it from side to side, switch around so the whole thing never gets too warm... I love stainless rod, but you are plating it, and that is not a good mix, if I remember right? Good Luck, stay cool in every way... PS, Someone that welds tanks for a living, will be the better man to tell you for sure how to do this, I learn everyday...

 

[fordsbyjay]

If you can Tig that is the route I would go. The biggest downside to Mig welding is it hardens the metal and makes it darn near impossible to drill, tap or manipulate after. With Tig or Gas the metal will remain soft and you can hammer/shape it if necessary.

The last experience I had Mig welding a fuel tank was not very successful. Don't do it is my only suggestion. Mig can sometimes leave small air pockets in the weld but look like a good weld on top. I welded a sump on the tank in my 56 and when I leak tested it water would seep out in spots. Sometimes it would take awhile but eventually it would leak somewhere. I ended up grinding out all the mig weld and gas welding it back on. Total pain in the butt.


Here is a link I found with some suggestions to prevent the problems I had.

My link

 

[coops]

Gerry,I did a similar project using light gage ms like yours but with different welders.Mine is a lincoln 135 and where I normally use the same wire size on most of my applications I could not on the project.This is the setup for mine I do not no how it will translate to yours...THIS 135 HAS 10 INFINITE POS FOR WIRE SPEED AND VOLTAGE.Wire size .023 ,voltage about 2.6-2.8, wire speed 3.0-3.2, on gas not fluxcore .Paying attention to the heat and metal I closely spotted the entire break always rotating to keep heat/distortion @ low.Mine has flat non pressed sides so distortion was a large concern.Slowly ground and pressure tested .Myself ,if it was to be done over,I also would have chose tig but at the time mig was my only setup.Good luck with the tank

 

[Whiplash]

Hey Gerry, sit that tank out in the snow,wrap yourself up well, put 3 or 4 pairs socks on your feet, and use your tig. The snow will help keep the tank cool, the extra cloths will keep your internals working, the socks will stop frost bite and as written above the tig will allow you to file and dress your welds were as mig welds are hard and one can only grind them down to dress. Keep warm my friend. :drowsy:

 

[lkeuten]

Hey Gerry, I just looked it up on Millers weld parameter calculator. Your 2mm = my 14 gauge. What Miller reccommends for a 75% Argon/ 25% CO2 cover gas are as follows: 17-18 Volts and a wire speed of 250-340 inches per minute using 0.030 size wire. This will put you in the 120 to 130 amp range. Now if I were to do this weld with mig I would put tacks in, spacing them approx 2 inches apart working around the piece to keep heat warpage to a minimum. Then I would grind the tacks down as much as possible. The idea here is that you are going to weld through the tacks and not leave a hump in the weld and still hold the metal in place. You should be able to weld 3 to 4 inches before you start to warp. Starts and Stops in the welds will need to be either ground or wire wheeled to clean them up so you can bring the next weld in to match. I know this process works because I've used it on 18 gauge with good results. Your mig weld will be somewhat harder to work with a hammer/grinder/wire wheel etc. I would practice this on some scrap before I started on the real deal.
Now that being said, personally I would tig it. You'll have a nicer looking weld, less chance for porosity in the weld, and a whole lot less elbow work with a grinder.

 

[RPM]

I have built over the last few years probably 600 tanks. 3-4 every week. We pretty much always use 14 gauge hot rolled steel. 14 Gauge is very close to your 2 mm. Just before we start to weld we grind back about 1/2" all the mill scale to get good clean steel. Dirt does not weld good. Assemble all the pieces where you want them and leave about .030 gap in the parts. Tack weld about every 4-5" and tack all the corners. All of the welding is done vertical top down to the bottom. Hold the gun at about a 45 degree angle as this will try to push the weld back up into the puddle. We use .023" wire. We try to weld the entire seem in one pass if possible. A 30" seem is hard to do without a stop but it can be done. Gently grind the tops off the tacks so you don't get a hump in the weld. Now if you have to stop to reposition yourself, when you start back you will have to over lap the weld about 1/4" or it will leak at the joint. You can grind the top off of the overlap when you are finished. I can't tell you what amps or wire speed. We use a Millermatic 180 with infinite amps and it is set at about 3.5 and wire speed is about 4. Weld all of the tank and grind any overlaps and dress as needed. Then we pressure test with air at 10 psi. We fined that Windex works really great to find any leaks. If you have any leaks grind 1/4" either side of the pin hole and weld it back in, dress as needed and retest. I would practice on some scrap to get the hang of it. I would guess about 90% of the tanks do not need any work to repair holes when they are tested, but it took a lot of practice to achieve that.

 

[fordsbyjay]

Hey Gerry, sit that tank out in the snow,wrap yourself up well, put 3 or 4 pairs socks on your feet, and use your tig. The snow will help keep the tank cool, the extra cloths will keep your internals working, the socks will stop frost bite and as written above the tig will allow you to file and dress your welds were as mig welds are hard and one can only grind them down to dress. Keep warm my friend. :drowsy:

Tig welding is so clean that you could just bring your project inside and do it in the kitchen. :hyper:

We try to weld the entire seem in one pass if possible. A 30" seem is hard to do without a stop but it can be done.

I can't believe you get 30" done without warping something. Well I do believe you Ron it just amazes me that's all.

 

[RPM]

You have to tack it all in place first. Also most of the tanks are made in just 2 parts.

 

[Youngster]

I welded hydraulic tanks for a lot of years. Our seams where 28" long. It took awhile before I could go the entire length without stopping. When I was new at it, I would start half way down the seam and as time awent by each time I would start further up the seam. Warpage was always a problem, The bestway to prvent it was to, as Ron said, hold a 45 degree angle with the gun pointed up and watch the flare at the end of the wire. If it is equal on both sides of the seam, it will cool at the same rate. If you need to make multi passes, stop on a start that has been ground bacl a 1/4" or so. The start is where you're going to find the least penetration. As mentioned, grind those tacks down to where they just hold.

Ron

 

[VegasBruce]

The only thing I do different than RPM and Youngster is any place I stop or stat is grind the weld down about an inch back for a starting point. I also weld around all the corners first. About an inch on both sides and grind them smooth, then weld the tank. I found that any leaks I had in the beginning where in the corners, so I weld around them first. And, always pressure test them first. :jester:

 

[Gerry]

I have built over the last few years probably 600 tanks. 3-4 every week. We pretty much always use 14 gauge hot rolled steel. 14 Gauge is very close to your 2 mm. Just before we start to weld we grind back about 1/2" all the mill scale to get good clean steel. Dirt does not weld good. Assemble all the pieces where you want them and leave about .030 gap in the parts. Tack weld about every 4-5" and tack all the corners. All of the welding is done vertical top down to the bottom. Hold the gun at about a 45 degree angle as this will try to push the weld back up into the puddle. We use .023" wire. We try to weld the entire seem in one pass if possible. A 30" seem is hard to do without a stop but it can be done. Gently grind the tops off the tacks so you don't get a hump in the weld. Now if you have to stop to reposition yourself, when you start back you will have to over lap the weld about 1/4" or it will leak at the joint. You can grind the top off of the overlap when you are finished. I can't tell you what amps or wire speed. We use a Millermatic 180 with infinite amps and it is set at about 3.5 and wire speed is about 4. Weld all of the tank and grind any overlaps and dress as needed. Then we pressure test with air at 10 psi. We fined that Windex works really great to find any leaks. If you have any leaks grind 1/4" either side of the pin hole and weld it back in, dress as needed and retest. I would practice on some scrap to get the hang of it. I would guess about 90% of the tanks do not need any work to repair holes when they are tested, but it took a lot of practice to achieve that.

A couple of points.
Do you agree that MIG is less hot than TIG so less distortion.?
I plan to coat the inside of the tank with a sealer once finished to make sure.
Not familiar with Windex. What is it?
I always was going to pressure test it with air at around 10psi. Have you had any deformation with this pressure?
Gerry

 

[RPM]

A couple of points.
Do you agree that MIG is less hot than TIG so less distortion.?
I plan to coat the inside of the tank with a sealer once finished to make sure.
Not familiar with Windex. What is it?
I always was going to pressure test it with air at around 10psi. Have you had any deformation with this pressure?
Gerry

Mig is a lot faster than tig and does run cooler so less distortion.

Windex is a window glass cleaner it does not have a soap in it, like soapy water does so it does not leave a residue on the tank.

It the tank has really big panels it with push these out under pressure, but they have always come back when the pressure is released from it.

PS I am going to check some more on your yoke. I'll email you.

 

[Gerry]

Mig is a lot faster than tig and does run cooler so less distortion.

Windex is a window glass cleaner it does not have a soap in it, like soapy water does so it does not leave a residue on the tank.

It the tank has really big panels it with push these out under pressure, but they have always come back when the pressure is released from it.

PS I am going to check some more on your yoke. I'll email you.

Thanks for help.
I m stranded at home. My PT blew all its water out even though I checked the antifreeze last week (-35 it said). Have to wait 6 hours for a recovery to get it to work and find out whats going on. It was -11 this morning and when the heater packed up it got rather cold. Bit down in the dumps but at least thinking about the tank helps.
Looks like from what you have said I will go for broke and MIG it.
Cant thank you enough
Gerry
PS No hurry on the yoke. I think the propUJ section was from a Chev truck but can send the measurement when you need them

 

[Youngster]

That's a great tip Bruce. If I get a leak, it's usually on a corner. Thanks for posting.

Ron