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Old 11-26-2018, 08:20 PM
RB86 RB86 is offline
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Default Gas weld vs. Tig welding

It seems quite popular to oxy/acetylene weld panels in the sheet metal shaping world. Is there advantage to that over Tig? Or vice versa? The gas seems to have a larger heat effected zone.
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Old 11-27-2018, 12:14 AM
Stretch Stretch is offline
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Hi Rob. For many years I used to gas weld both aluminium and steel body panels as it was considered the traditional way. These days I will only gas weld aluminium body panels, but steel I will always Tig fuse with no filler rod as the distortion created by the heat affected zone is approximately half that of gas welding. This equates to a much shorter dress up time of the welded areas. Gas welding does a great job on steel - don't get me wrong - but when I weigh up the time taken for the job Tig comes out as the clear winner for overall neatness and lesser distortion.
Tig welding aluminium body panels tends to leave the panel prone to cracks, particularly at the end of the welds. Some folk tend to counter this by Tig welding both sides of the weld, but this makes the job twice the effort and isn't always practical when welding direct to a body. Gas welding aluminium is a very fast process once you become proficient and leaves a beautifully penetrated weld, which is virtually impossible to replicate with Tig due to not being able to bathe the underside of the weld in a shield of argon whilst fusing. It really becomes impractical - but not impossible - i guess.
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Old 11-27-2018, 02:29 AM
Mike Whelan Mike Whelan is offline
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Hi Rob,
I'm an amateur restorer and have used OA welding for many years. I fusion weld panels that are butt joined together. Heat transfer and distortion can be a problem especially on low crown areas like doors etc. but after planishing the surface finish is excellent.

A few years ago I bought a Miller Tig welder which had no pedal. I was impressed at the low heat transfer/distortion compared with OA. The weld appearance was very good and probably a bit better than OA. On steel I got more consistent penetration

However, the downside was the need for perfect fit up which was not always possible. Even with good fit up I have difficulties with the edges of the panels creeping apart.

I find the heat from the Tig more concentrated and harsher than the slower softer OA flame.

Once the Tig puddle is started I can usually keep going but starting is the problem.

Maybe Matt can contribute some ideas?


Mike
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Old 11-27-2018, 04:15 AM
Jaroslav Jaroslav is offline
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OA makes you a soft shot. You can roll in EW reliably. Tig left a smaller footprint. Caution !!! I was alerted to TIG health risks. Microwave radiation and used gas. Older births people may have health consequences that were not expected. Well ventilate or suck in ventilation. Microwave radiation ....... you do not have leakage.
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Old 11-27-2018, 06:55 AM
RockHillWill RockHillWill is offline
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Having recently been exposed to a four day class put on by Kent White that was specifically designed to learn different 'joining' processes including gas welding, a little bit about TIG and learning to do brazing and soldering of different types of steel, aluminum and assorted alloys, and it was VERY informative. His knowledge of metallurgy and the development of the assorted dies for use in his planishing hammer left each of us with the distinct preference for gas welding any panels, etc. that include the need for butt welding, fusion welding and any form of deformation after the weld has been completed. He was particularly adamant about the advantages of the use of flux as a method for eliminating inclusions and porosity most often found in TIG welding. The large over the road trucking industry has gone away from TIG welding their large fuel tanks in favor of gas welding due to the problem of porosity. We repaired such a tank as part of Kent's seminar. It is true that the gas weld makes a wider HAZ, but that small additional amount of cooling time permits the flux 'puddle' to more completely allow time for the impurities and porosity to boil their way to the surface and not be left in the weld itself. He made me and others a believer in gas welding, especially for use when shaping panels. Kent's power hammer was outfitted with a multitude of engineering based die designs and with the variety of motor sizes we hammered the 'crap' out of a large number of panels of both aluminum and steel with no cracking or brakes. It was MOST impressive. We were able to both stretch and shrink without issues of any sort.
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Old 11-27-2018, 11:15 PM
RB86 RB86 is offline
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Thanks for the input everyone.

I don't know a thing about the gas welding equipment. What kind of money is it to get into a good setup? What kind of costs are involved in refilling?
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Old 11-28-2018, 12:51 AM
Jim Tomczyk Jim Tomczyk is offline
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Quote:
Originally Posted by Stretch View Post
.............
Tig welding aluminium body panels tends to leave the panel prone to cracks, particularly at the end of the welds.........
Has anyone any experience of these Ali tig rods that profess to be fully ductile and crack proof -or is it the more concentrated HAZ that is the root cause of the issue with tig Ali welds?

https://www.metals4u.co.uk/welding/c...m-1.0kg/p58040
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Old 11-28-2018, 03:15 AM
skintkarter skintkarter is offline
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Just to add my 2c worth - I'm 63 and have owned a gas set since I was 13. All of my panel repairs when I had a panel shop (rust repairs and accident damage) in the mid 70's was done with O/A. I bought a small Mig in the late 70's and that cut welding time significantly on the kind of work I was doing at the time. However any butt welding I was doing, I still did with O/A - tacked up, planished to release the stresses and then fused with no filler rod. Since becoming a filthy Life insurance broker and having more time to play in the shed with ever increasingly complex projects, I've bought a Tig and taught myself to drive it. Absolutely with Matt (Stretch) here in that butt welding steel, Tig is a bunch easier to control than O/A. Fitup and tacking is crucial - all without filler rod unless absolutely necessary (a bit of 0.9mm Mig wire at the ready if need be) and then a fuse with no filler at all. The result is a contolled narrow HAZ and full penetration which can be planished flat and filed up to a paint finish.

My experience with Aluminium is that it's a whole different ball game.

I almost hate it, but am persevering. The Ducati Imola tank project I recently completed gave me particular grief with porosity and took a while to winkle out the weepy bits...

I really need to learn to O/A ali.

However, what constantly sickens me is that I have a metalshaping God mate who can execute consistently low profile crack free Aluminium Tig welds on 1.2mm using slivers of parent metal as his filler rod. The resulting welds are then crushed flat in his wheel, completely disappearing for polished finishes.

The trick appears to be preheating the bejesus out of the first 6" of the weld before lighting up the Tig. He never suffers from cracking and the amount of filler he adds generally needs no filing before wheeling flat.

Right now I'm sticking pins in a waxen effigy of him...

For the rest of us mere mortals without the 'seat time' that my buddy has, Aluminium sheet butt joins seem to be much more predictable and faster with O/A - but I gather it is quite a skill to master. I've bought some flux and plan to have a practice shortly.

O/A is also very handy to have in the shed for other stuff - O/A cutting and O/A spot heat shrinking, so let's face it you just need all of the gear...
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Old 11-28-2018, 06:20 AM
RockHillWill RockHillWill is offline
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I am a long way from being an expert on this, but I am fortunate to be able to hang around a number of folks that are, and it is becoming clearer and clearer, that if you are going to start from scratch, there is only one clear option for those of us in the US.

https://www.tinmantech.com/products/welding/

Kent White has spent the greatest part of his metal shaping lifetime researching and studying this lost art and has developed not only the most applicable equipment, but the most logical approach to learning gas welding that I have been exposed to. He was at my shop for eight days just last week and I witnessed first hand his knowledge and technique. I struggled with getting any form of decent results until I watched a video of his on gas welding aluminum. I do not want this to seem to be a 'sales pitch', but this recent time spent around him has reinforced my earlier appreciation for his approach to gas welding both steel and aluminum.
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Old 11-28-2018, 08:34 AM
Stretch Stretch is offline
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Try Tig tacking a butt joint on 16 gauge aluminium without adding any filler rod if you are in any doubt about the stresses inherent in Tig butt welding aluminium sheet. I will guarantee you at least 50% of your tacks will crack. This exercise will substantiate my point with a lot more clarity. I've been involved in restoring aluminium race cars since 1984 (D-Types, C-Types and Lightweight E's etc) and never, ever did myself or any of the guys I worked with use the Tig setup for butt fusing aluminium sheet. It was common knowledge that Tig = cracks somewhere down the line on bodywork. I'm sure someone with metallurgy experience will be able to explain the 'how's and why's', but for us it was just fact based on experience.
As a side bonus, gas fusing aluminium is so much faster, so win-win.
Matt
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