TIG welding question

Hi all,

I've got a 180 A stick welding set, but it's AC only. I may want to weld stainless in the future, but am unlikely to want to weld aluminium. (Okay, I'm thinking of building a coffee roaster when I've finished the phase convertor project, and it would be attractive to build it from stainless). I've heard that you need DC TIG to weld stainless, is that right? I know where I might get an add-on TIG unit for my welder, but the guy said it was suitable for aluminium only.

So here are the questions. If I want to TIG weld stainless, must it be DC TIG? If so, is it possible to get a small add-on unit which will rectify the current from an AC stick welder and enable it to be used for DC TIG? I don't have a picture of my welder, but it's pretty similar to this one I saw on eBay recently:

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Mine is a little larger and has an in-built battery charger, and it's built by Cytringan rather than Oxford, but the current rating is the same. Whoever scored that set on eBay got a nice deal. I'm not eager to replace the set as it suits my stick welding needs and offers 100% duty cycle, plus I like it a lot. Is there any way to weld stainless without getting a second welder?

Suggestions would be appreciated.

Chris

Reply to
Christopher Tidy
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Chris, I don't think you can tig weld stainless with AC. I tried by accident before and it weren't pretty. However, you may be able to stick weld it with AC. Call the weld supply and see if they have rod that would do this. ERS

Reply to
Eric R Snow

I would expect you can AC tig weld stainless. I can't think of any reason that you couldn't. But I know you can stick weld stainless with an AC welder. May not be as pretty as TIG.

You can also silver solder ( braze ) stainless. It might be the best looking way to do it. Is the stainless fairly thin? Can you use a brake to put a flange on the edge and have a lap joint? You could use either propane or carbon arc.

Dan C Is there any way to weld stainless without

Reply to
dcaster

Dan and Eric: Thanks for suggesting that I could stick weld stainless. I'll do a search online and look for suitable electrodes, then get in touch with the welding supply store (if my coffee roaster project gets off the ground).

Dan: It would be thin-ish stainless, but would likely have to be 1.6 to

2 mm if I was going to stick weld it. I don't have a brake, so putting a flange on the stainless could be a problem. But I do recall than the data plate on my welder says something about using a carbon arc torch on the 80 V AC terminal. I'll have a look.

Thanks for the suggestions.

Chris

Reply to
Christopher Tidy

Most of the time I use a wood stud with C-clamps to clamp sheet metal to a steel channel. Then use a mallet to form a 90 degree bend. More work than a brake and not as nice looking but it works. Just start at one end and tap it over about 20 degrees and go down the line. Then come back bending it another 20 degrees or so. untill you can flatten it against the channel for a 90 degree bend. Works okay for 1 mm stainless.

Dan

Reply to
dcaster

Yes, you can put rectifiers on a stick welder to make it DC for either stick or TIG. I've done it. The usual problem is that with a bridge rectifier, neither stinger (or torch) nor groundclamp are really "ground" so the work can't be grounded. That really isn't a problem other than you need to know about it. You won't have HF start -- and shouldn't need it to TIG SS.

Another big difference is that you won't have footpedal control -- but that may not be a big deal with SS. My DialArc 250 was originally used for welding SS silos together; came with about 50 feet of leather-enclosed cables and waterline -- and no footpedal! There was a switch on the torch handle, but it was just an on-off switch. So apparantly the guys that were doing that thin SS had no problem doing it without a footpedal.

Reply to
Don Foreman

Reply to
David Billington

Thanks for advice. I'll keep an eye out for a used rectifier unit. Any idea what they're worth in decent condition?

Best wishes,

Chris

Reply to
Christopher Tidy

Why can't the work be grounded? Neither side of the welder secondary is grounded and the whole secondary circuit is floating. How could there be any circuit to ground? I'm sure that I'm missing something - what is it?

Bob

Reply to
Bob Engelhardt

You can make your own rectifier from diodes, or buy a fully made rectifier bridge. They sell a lot of them on ebay. Lot of 4 Diode 1N3267 - 400 Volt 160 Amp

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You can make a rectifier bridge out of SCRs, as well:

SCR Stud Mounted 300 Amp Heavy Duty 250051 High Volt

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these SCRs could get you weld at under 180A.
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2 Huge SCRs, SCR diode
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I have two more SCRs that I can give you, good for 300A each, free except you pay shipping to UK.

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Note that besides a rectifier, it would be good to have something to smooth your DC voltage. That usually includes some capacitors. I can give you three 19,000 uF 75V capacitors that are already paralleled and have discharge resistors on them already, for free, if you pay shipping to UK.

If you look for SCR on ebay, also type thyristor in the search box.

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Reply to
Ignoramus408

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Thanks for all the kind offers! I'll think about building an add-on and get back to you if I do, but I was hoping I might find a ready built unit this time. Otherwise every tool becomes a project, as I'm sure you've discovered :-). That said, postage from the US to the UK is usually much cheaper than the other way around. USPS seem to do work as opposed to sitting behind their desks in trendy hi-vis vests chewing gum and listening to rock (this was what I found when I visited our local sorting office recently).

Sadly I daren't do any welding right now. I spilt a gallon of diesel on the workshop floor and soaked it up with sawdust, so now I'm giving it some time to evaporate to reduce the fire risk!

Chris

Reply to
Christopher Tidy

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no problem. I ship stuff all the time. I will be happy to see these things actually used in some real project. I will keep these things for at least 2 months, likely much more (but no guarantee beyond two months)

Read a little bit about rectification and chokes for current, snubbing and such, before embarking on this.

I am in the middle of the tig inverter project (kind of the opposite to what you do, you want to make DC out of AC and I want to make AC out of DC), and this project has ballooned in scope fivefold from what I thought it would take, time wise. I am learning as I go along, and it is not hugely expensive, but it is a lengthy project. It is near having a working prototype actually, I hope to have a working inverter by the end of next week. I would say that I am 60% done. Once (and if) the inverter works, I would have to fabricate an enclosure, preferably from scrap parts, and that again would take efforts.

It must really stink there. I would not even come near it. Diesel fuel smell gives me a headache every time.

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Reply to
Ignoramus408

Reply to
David Billington

I'll look forward to seeing the finished unit!

It does. Fortunately I don't mind the smell of diesel too much, but 1 gallon evaporating in a 10' x 12' room is overpowering even for me at the moment.

Chris

Reply to
Christopher Tidy

Let me know if you/he does wish to sell it anytime in the future. No need to disrupt his permanent loan, but I could be interested. I can see that sometime I'm going to need to weld stainless, and besides, it would be a good skill to learn. Presumably this is a rectifier and a gas supply unit, but without HF, so you still have to contact the work to strike an arc? Did you keep the Pickhill for arc welding but get a full-blown TIG machine yourself?

Best wishes,

Chris

Reply to
Christopher Tidy

Its just a rectifier choke unit, the gas control is within the HF unit so that was always last in the system and used for arc starting. I set-up a few jumper cables with Dinse connectors and so could swap from AC to DC and back in a few minutes.

I did keep the Pickhill for stick weld> David Bill>

Reply to
David Billington

True enough about the portability, but I think the nice thing about the oil-cooled sets is the 100% duty cycle and the fact that they pretty much last forever. I don't worry about mine being in a slightly damp environment, but I would with many of the more complex modern machines.

I'll have a think about the various TIG options and see how badly I need it over the next few months...

Chris

Reply to
Christopher Tidy

Chris you can weld stainless with the AC stick welder...308-16 rod works ver well on AC... others such as 347-15 work on DC only what is the thickness of the material you'll be welding

-- xkvator

Reply to
xkvator

Most likely 2-3 mm.

Chris

Reply to
Christopher Tidy

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