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12th November 2013, 01:25 PM #1Senior Member
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Thinking about TIG - is it the wrong hammer for the job?
I seem to do an awful lot of welding with Duragal (not coated on the inside) and Supagal (coated inside and out). The choice boils down to what is available in a particular size. It's all been with stick up until now, but I'm thinking I might like to give TIG a go. Following on from DoctorWu's comments in this thread:
https://www.woodworkforums.com/f160/t...-steel-115743/
is it OK to TIG Dura/Supagal? Or is it an absolute nightmare of constantly cleaning/repairing electrodes from contamination? Obviously I could prepare the exterior with a flap disk, but it would be difficult with small diameter SHS/RHS/pipe to clean the inside of Supagal and inevitable fitting mistakes would no doubt mean that there's a chance of the gal on the inside affecting the weld. Is that how it is with TIG? Super critical to have inside/outside/everywhere within the heat affected zone clean?
While I realise that TIG isn't the perfect process for this material, I was frustrated with my recent pipe stuff with occasional slag contamination. This occurred from the small diameter pipe and having to move so much faster with the hand ~300mm away from the weld so e.g. for every 10mm of weld on a tee, you might have to move your hand ~400mm to keep the angles correct. Sometimes I'd end up behind, and then I'd push a bit of slag into a weld, which would then be tedious to fix. Particularly with the 6g nature of the joins. I figured if I keep doing pipe stuff, I'd rather spend more time preparing and end up with a slag-less weld than blast in there with the stick and then spend more time cleaning and fixing afterwards.
I wouldn't be starting TIG just for this stuff, but I have a queue of projects that will all involve this type of material so I might as well practice on it if it's suitable to use TIG.
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12th November 2013, 03:20 PM #2
I'm fairly new to TIG, but I have found welding Duragal to be a bit of a pain to weld with TIG (compared to black steel). This is mainly due to contamination/mess from the galvanising.
As much as I love the TIG process, I tend to shy away from welding Duragal with TIG unless the job was particularly fiddly and difficult to do with stick ... and then I would spend a lot of time removing the gal to minimise any issues.Cheers.
Vernon.
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Bite off more than you can chew and then chew like crazy.
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12th November 2013, 05:08 PM #3SENIOR MEMBER
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The reason I bought a MIG was because I was doing lots of galvanised (dura/supa gal) stuff. On the face of it, TIG is not a great process to use with galvanised material generally. However it can work well - it just takes more prep, but you can get an excellent result.
With TIG you obviously have to grind (flapdisk) off all the gal on the outside of the joint (I usually ensure at least 1cm from the edge). The issue is that the any zinc on the inside of the RHS that you can't grind will also start to find its way into the weld (and onto your electrode) if you get full penetration of the joint. If you have really good fit up and don't penetrate excessively (as in no actual keyholing), then you can avoid nearly if not all of the zinc issues.
You could also cheat a little by running a quick low amp tig bead around the joint to effectively seal the zinc inside, then a high amp cover pass. Once again, good fit up will limit issues of suck back of zinc contaminated material into your weld area.
Apart from the zinc issues, the type of joint you describe would be perfect for TIG and this process is a joy rather than a chore. TIG is usually a case of doing it once and doing it well.
Cheers
- Mick
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12th November 2013, 08:02 PM #4Philomath in training
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12th November 2013, 09:26 PM #5SENIOR MEMBER
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My suggestion starts with an "M" and ends with "IG". Provided you're not too hung up on bead profile, which can be improved with technique, CO2 gas is cheap and works very well with gal and also blasts through rusted and painted material. Welding 1.6mm Duragal is a doddle, and even narrow corners are entirely doable as the increased stick-out of the wire seems to be compensated by the crowding of the shielding gas.
With my UniMIG combo unit, I can be running gas MIG while also having the stick lead on hand (wired up as DCEP) and with a flick of a switch, can change to stick without having to touch the ground lead.
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12th November 2013, 10:50 PM #6Senior Member
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Yeah, I keep hearing that. Thing is, not only do I like making things difficult for myself, but I am kind of hung up on bead profile. Up until now, everything I've done has been outside garden stuff but I've got some inside projects and if I could make the welds a feature (wishful thinking, I'm sure) that would be awesome. I quite like great tig welds.
But mig makes sense, that's for sure. I've got access to a couple of machines but only used it a few times.
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13th November 2013, 12:22 PM #7Senior Member
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Some of the machines I'm looking at (higher end reputable brands), DC only due to $, some of them have pulse controls. While this seems like a cool idea, does anyone actually use pulsed DC TIG and how useful is it? I.e. some models have a pulsed and non-pulsed variant with a few hundred $ separating them.
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13th November 2013, 01:10 PM #8
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13th November 2013, 01:20 PM #9
I don't have pulse on mine, so maybe I don't know what I'm missing, but I've managed to quite easily butt weld 0.9mm MS sheet without using any filler.
Having said that, it is obviously a usable and useful feature, although not essential, so it really comes down to whether you are prepared to pay for it. As a hobbyist I tend to forgo time saving and ease of use features in favour of a lower purchase price. In a production setting I would have a different mindset.Cheers.
Vernon.
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Bite off more than you can chew and then chew like crazy.
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13th November 2013, 02:57 PM #10SENIOR MEMBER
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Yes... same here.
On the other hand as a sole operator/hobbist it is nice to know you can do anything and not be limited (so having extra features is actually good and I'm willing to sacrifice convenience to have those extra features). As an example, I'm happy to have my TIG machine double as my Stick machine - and put up with swapping leads around. If I was in production, I would have 2 separate machines.
Regarding pulse. I do have pulse features on my TIG and very rarely use them and I know plenty of people who are the same. Personally I reckon a few hundred extra dollars wouldn't be worth it for the general hobbist. I'd put the extra $$ towards a good auto helmet or ensuring you had HF start on your TIG. Having a good quality/clean/clear helmet really does pay benefits with TIG welding. I have a separate helmet for stick welding and it gets treated pretty roughly, has splatter marks, etc. etc.
As I and others have said previously - MIG is really the go to process for what you describe - it depends on what other capability you want.
Cheers
- Mick
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13th November 2013, 02:58 PM #11Member
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You can always use muriatic acid (30% hydrochloric acid) from a pool shop to strip the zinc off the ends of your tube. Just put an inch in a container and balance the tubes so the ends are in the acid. It will bubble, so make it a deep container. Use a lid to keep old stuff. You can use it again until it doesn't bubble anymore. Do it outside though and don't breath any fumes.
It only takes a few minutes and then you put the tube ends into sodium bicarbonate solution to neutralise the acid. You get that at the pool shop too. Makes the steel like new, but with no galv.
Its a bit messy but you get great results. I use the old stuff to kill weeds, but then, I hate gardening and don't care if nothing grows there again. it always does anyway.
It's a relatively safe acid because it hurts immediately if you get it on you, and washes off easy. Old clothes and glasses might be a good idea.
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