[sunppeli]

I've got to weld a 10mm thick flange to a BMW gearbox. This is the heaviest welding job I've ever attempted. I'm hoping to get some tips on how to approach this job! I've got a 250amp welder and a 17-style water-cooled torch from River-Weld. My setup looks like this:

Today I tried to weld it for the first time and it seems like it really needs some heat. I barely managed to tack weld it before the return water hose got almost too hot to touch. I first used straight 180amps and then pulsing at 1pps max 200 amps 45%bg and 40% on time. Pulsing seemed to work a little better. I set the ac balance to minimal cleaning. Still the torch got too hot before I really got a good puddle going. AC frequency is ~60hz and cannot be adjusted.



So the metals are clean and weld quite easily but just need lots of heat. I'm thinking of using a propane torch to heat the box up. What kind of temps should I be aiming at? I guess the limit is what the rubber/plastic parts in the box can take. Do the metals need a clean after being torched? Any other tips to get more heat into the weld? I also wonder if the torch return hose is actually supposed to take that much heat? The torch itself was only slightly warm and the water in the tank was still cold. I also have a 26-style air cooled torch, any idea in using that by welding in shorter sections?

Huge thanks for any help!!!

[Otto Nobedder]

First, it sounds like you have a flow issue with that torch, a restriction of some sort or an inadequate pump for the line resistance. I can weld above 200A HFAC all day with a wp17 and not have heat issues.

I'd try to diagnose that first. Unhook the return line (it should return through the "hot" lead, where the cable is), and watch it dump into a bucket. It should piss a pretty good stream after travelling to the torch and back. If it's a trickle, there's the heat problem, and sort the line out section by section back to the pump. If it's a trickle the whole way, look at the pump/heat exchanger circuit.

10mm, between 3/8" and 7/16", is a fairly heavy section for that machine, and preheat will help. If you have actual rubber seals (and residual oil) to be concerned with, 270*F (120ish *C) is about as hot as you want it. I assume, when you talk about propane for preheat, you're thinking something like a weed-burner? This is always a carburizing flame (propane/air), and a wire-brush will be enough cleaning. If you mean oxy/propane, be sure to set the flame SLIGHTLY rich, and the wire brush will be enough.

Once the cooling issue is resolved (and I'm sure you have one), if the preheat doesn't get you there, consider adding helium. Expensive, but it really does work wonders.

Oh, and for the air-cooled, unless it's a 400A+ rated torch, you'll find it really hot in a hurry on this, too.

Let us know what you find.

Steve S

[TamJeff]

Otto is right. The only issue I have here is with the WP-17 type torch at least. I think that's only rated about 115-120 amps AC. I use a WP-20 and 10mm will make it work hard, even at 250 amps. 9mm is about the max without adding heat or helium or creative joint prep if I am to make any time at all.

If you are running a water cooler, perhaps it never had conditioner added. Algae will clog up a torch's plumbing fast.

[sunppeli]

Thanks for your replies!! I have water cooler (aluminium water tank 20-liter), I think my pump is adequate but the inlet water line seems very small (2-3mm inside). I should try changing that to a bigger one. I doubt algae is an issue yet since the cooler/torch are only about 2 months old. I wonder what the real rating for the torch is? River-Weld only says 200amps but I highly doubt it's 100%.. Helium is too expensive for me right now...

So what I think I'll do is to change the inlet line to a larger one and preheat the parts. I'll just weld is shorter sections if the torch still heats up. At least it cools down fast.

[TamJeff]

That's about the ID of the lines on mine. Maybe your torch carries more amps as I am not familiar with river-weld products or even what all a 17 style torch represents. I have always used a 20. A wp-17 came with my used machine but it's air cooled, I think. When I told them I would be welding sched 40 aluminum pipe amd 1/4" aluminum flat stock, the water cooled wp-20 is what was recommended as minimum for my older machine. I have ballooned power cables welding 1/2" plate with a miller 250 syncrowave for more than 5 minutes at 250 amps.

[sunppeli]

I remembered wrong! My torch is actaully a 20-style. I guess a 20 is actually smaller than 17? Whatsoever it still gets too hot. Thanks for the info on the inlet hose, I will let the original in it's place but I'll look for a stronger pump.. Today I'm going to preheat it to 270F/120C and see if that makes things any easier.

[noddybrian]

Hi - I like the portable welding table - that's not the " Nomad " version though!

Looking at your pump it's not clear what it is so it's difficult to know how suitable the pressure / flow is - BUT the line from the tank looks very small - a pump needs a noticeably larger inlet from the tank than the outlet or it will cavitate badly - seems odd - but a pump hates sucking water - whereas it can push pressure happily - maybe worth checking out .

Looking at where your tacking - that outside corner is the hardest to get heat into & reflects heat back at the torch quite a bit - assuming your welding it on the inside as well for strength if the inside of the plate is flush with the bell housing it should be possible to do a V prep which would weld more easily - if your able to weld this first there will be alot of heat soak & once done with the inside you can go back and do the outside run where your tacks are - this avoids helium & excessive torch heating- may not be possible - just a thought.
Good luck with the project.

[sunppeli]

Yeah . Even portable it's not very light because there is a 600kg lathe headstock on the trailer!

This is my pump:
http://www.ekwb.com/shop/pumps-and-acce ... -pump.html
The inlet hose inside diameter as I recall is 8mm (or 6). Should I need a bigger hose? The flow really isn't that great.. Still it's not actually the torch that is overheating, it's the return hose/cable. The torch gets just a little warm.

I was planning to weld it only on the outside because the shape on the inside is a little difficult plus the plate is not flush with the gearbox on the inside.... Making the plates so that it could have also be welded on the inside would sure have been a good idea.. I'll see if I can still do something about that but I think that's the way it has to be done now..

I looked at rentable helium bottles and their prices aren't that bad actually. I guess I'll try that too.

The second attemp has to wait until next monday but I'll keep you informed how it goes!

[noddybrian]

Hi - had a quick look at that pump - it appears to be intended for use on water cooled CPU's / graphics on computers - I think because of the relative amounts of heat involved between this & the welding torch it just does'nt have sufficient flow rate - possible aggravated by the length of lines involved creating more dynamic head than it would normally experience - I believe Otto had a ball park figure for suitable flow he mentioned in a previous post concerning a " redneck " cooler set up - most likely he'll comment on this - I looked at a couple of similar pumps & decided against them - not researched it more as I'm kinda short on funds for the Tig at present so have not yet got a water cooled torch - what do you think of the Shop River / River Weld torch ?
If possible I'd try adjust the plate so you can weld the inside - bell housings experience more force / flex & vibration than you'd think & I've seen a few conversion plates crack or break after a relatively short time so welding both sides would be the way to go.
I'm intrigued as to your affordable source of helium - from clues in your post I assume your in the UK - now that can't be from our robbing bar-stewards @ BOC then ! - perhaps you'd share your supplier with us.
Cheers.

[Otto Nobedder]

Beware of discount helium. "Balloon-grade" has pretty high tolerance for impurities. I've even heard, though never researched, that it contains oxygen on purpose, as safety for the idiots who think it's funny to talk with a lung-full of helium.

I'll dig a little on the pump flow rates... The post noddybrian was referring to was a basic setup for mild steel, not extended use at high amp HFAC, so the figure I gave was intended to be "adequate" for a starter setup.

EDIT:

This link should give you a starting point for typical cooler pumps:

http://tectorch.com/water%20cooler%20re ... 0pumps.htm

Note it's a vane pump, meaning positive displacement, with a by-pass to limit line pressure to 50 psi max.

Steve S

[sunppeli]

I got it done! Helium was after all way too expensive so I just gave it a good pre-heat. Here's a video on it if you are interested!
http://www.youtube.com/watch?v=DvPvVwWHnjs

About my setup:
http://www.youtube.com/watch?v=uWcX2G7rB2g

Huge thanks for your tips!!

[Otto Nobedder]

Good for you!

That looks great.

The two places where it "puked" inpurities are probably due to the porous nature of cast aluminum... A tiny bit of oil migrated into the pores of the metal and gave you trouble. It says a lot for the quality of the casting that it only happened twice in that much weld.

It's all the more impressive since the machine only welds at 60 Hz.

Steve S

[RWhite_25]

Found these tips worthwhile. I bought an used boat that has thick aluminum to be welded. Where should I get discount Helium?

[Otto Nobedder]

You'll want welding grade helium, so you should check pricing at all the suppliers in your area. "Balloon" grade helium has way too many other gasses in it, and sometimes oxygen is added on purpose, for people who think it's fun to talk with a lung-full. Don't let them sell you "ultra-high-purity" helium, though. You're not building a nuclear reactor or a rocket engine.

How much you need, relative to argon, depends on your machine's capacity and the thicknesses you'll be welding. As an example, if your machine will do 200A, and you're welding 3/8", you may get by on preheat alone, but adding 25% He will allow you to back off the power for a longer duty-cycle. On that same 200A, if you're doing 5/8", you'll benefit from 50% helium. You can have it custom-mixed in one bottle, but the more economical route (in the long run) is a separate bottle and flowmeter, and wye the argon and helium outputs together before the machine. You can use a standard flowmeter on the helium bottle, but be aware that as soon as the ball starts to "dance", you're already between 5 and ten CFH. Soap-bubble test everything (including the bonnet of the bottle valve) and be sure it's leak-tight, and that helium will last a long time. One other tip, for ANY high-pressure bottle... Open it all the way, tight against the stop. There's a separate seal there that stops leakage past the valve's shaft, so you don't rely solely on the valve's packing to hold 2200 PSI.

Steve S