Welding applications and thin metal

[Grahame Collins]

When it comes to arc welding processes they are much like other things in life. No one would consider buying a small 4 cyl car and then expect it to tow a large caravan. It simply is not suited for that purpose.

Unfortunately some of those same people who are knowledgeable about what size vehicle can efficiently tow a caravan have little idea about their welder and fitness for purpose.

It all depends on the major tasks that you expect your welder to perform.

Too often purchases are made on a cost basis alone without appropriate consideration to the intended projects.

It seems sensible to examine some light welding jobs and attempt to group them with the most suitable process to weld them.
Lets look at where many seem to have big problems.

We will start off with the light stuff ,say .5mm to 2mm thickness
Light walled pipe, furniture tube, SHS, RHS and sheet metal ( Including vehicular sheetmetal ) are best joined by

• LP gas brazing or or Oxy Acetylene brazing- LP is probably the cheapest and requires little skill (see below for Oxy acetylene comments )
• Oxy Acetylene fusion welding - very efficient but needs a good level of skill-purchase costs are high .A full kit allows oxy cutting of ( carbon) steel ,Oxy welding of steel, stainless steel ,aluminium and brazing of a a wide range of ferrous and non ferrous metals over a wide range of thicknesses .Oxy consumable cost and cylinder rentals keep costs high.
• Tig welding –Extremely high quality but requires a high skill level. It can weld most known metals .It has a high purchase price and high gas consumable price and additional cylinder rental costs.
• Mig welding –a high purchase price gas consumable ,cylinder rental .Small diameter electrode .6mm works very well on light wall materials. NOTE Gasless or Flux core is not suited to thin wall applications. The term MIG is a misnomer when using a gasless wire Ie : a Gasless Metal Inert Gas.


What should be noted about welding thin wall materials is that they are highly susceptible to burn through and heat distortion. LP and Oxy brazing allow intermittent application and removal of the heat source without disruption to the weld. Mig and tig allow a good control of the heat input.
Stick can be applied to sheet work but only with techniques that recognize that overheating and distortion occur.

It not the definitive guide by any meansbut , does this help ?

Grahame

[watson]

It not the definitive guide by any meansbut , does this help ?

Grahame[/quote]

Well. it helped me.......just a heads up type of post...stuff you forget.
So Thanks,
Regards,
Noel

[martrix]

Good, tips Grahame.

Welding thin car panels is the very reason why I got into MIG welding.

I was restoring an old Holden and naturally it needed rust replacement panels and rusted through sections patched and welded.

I went around to a few panel beaters, and none of them would do it:? .
I got tired of asking around, so I went and bought a book, studied the process, and went and bought a MIG ($500 I think).

Ended up getting good enough to finish the car.

My question is regarding the methods of using MIG with thin auto panels.

The only way I could do it with out warping the panel from too much heat, was to just spot weld, constantly altering the areas being welded. Is this the right way?

[peter_sm]

Good on you for doing that Martrix. The right welder for the job, and it paid off for you. Truth be known you would have done a better job than some of the "smash" repair places could have done for you. I know I have been in the smash industry for a long time and seen enough of it to make me shake my head in shame.

Constant tacking is one way to reduce warping to a minimum. The only other option is to panel beat the panel straight after welding, and that is not too easy once a MIG weld has been put across it, even if it is grinded and linished back

[Grahame Collins]

Car metal is one of the jobs i am happy to leave to someone who knows more than me.

The usual stuff like .6 wire,clean ,good alignment etc etc.
I think there must be a better wire grade too as Lw1 is high tensile and would have a different co fficient of shrinkage than the car metal-- panel beaters advice here-I am surmising .

There was a good book on car welding around by a Donald Wait -a TAFE teacher in the subject.

Mig is ok if you have it ALL tacked up. some fellas after having tacked a little bit get all excited like and just have to see the job welded.Bad mistake

The go is to spread out the heat as evenly as possible. lots of tacks and small beads- small beads smaller heat. The idea is to weld opposites and let the distortion which does occur anyway to oppose its opposite number.
Clear as mud right?

Grahame

[ANTHONY62]

One thing that gets overlooked when welding thin gauge material,specifically sheet is the grinding/finishing process.

We can control our distortion in a number of ways as discussed in other posts eg.skip tacking and applying a wet rag immediately upon completion of tack, (time consuming, however very effective for zero distortion ), however a lot of individuals become heavy-handed when it comes to dressing the weld area and over-heating the metal,thus buckling the sheet, particularly car panels as I assume it is an average of around 22gauge (0.8 mm).

Keep an eye out for the colour change in the metal whilst grinding as it is an indicator of the heat input and possible distortion.

If for some reason you need to weld thin gauge material with stick, here's a hint- have a piece of scrap metal in close proximity to the area to be welded and strike an arc on it just prior to doing your tack or stitch weld - you warm the electrode up and makes it easier to initiate the arc especially on some of those finicky cheaper AC machines out there.
I have successfully welded 24gauge cold-rolled with this method.

Hope some of this helps.

Regards

[peter_sm]

The old Donald Wait book, I had that as an apprentice. Good old school stuff.

I and a lot of panel beaters I have worked with have found that 0.8mm wire is more reliable than 0.6 It seems the larger machines a shop uses will have problems with 0.6 as it is too weak and will buckle if the tip holds the wire. I have never worked in a shop that uses it with the usually 180A plus machines that are often used.

Getting the pieces exactly lined up and clean is most of the work. If you have crud or mis aligned pieces, then no manner of special machines or gifted welders can make the job perfect, they can only make it less messy.

It is true that sectional stitch welding of alternate areas will work well in keeping warpage to a minimum. One of the best ways to achieve this is to also have a helper that can use compressed air to blow cool the weld a second after you finish doing about 20-30mm.

A wet rag will work also, but gets hot after a while and also puts water on what you are about to weld.

Practice practice practice. Don't worry I get all muddled working with wood, because I know I can't just weld back on the piece I just cut too short.

[SPIRIT]

The old Donald Wait book, I had that as an apprentice. Good old school stuff.

I and a lot of panel beaters I have worked with have found that 0.8mm wire is more reliable than 0.6 It seems the larger machines a shop uses will have problems with 0.6 as it is too weak and will buckle if the tip holds the wire. I have never worked in a shop that uses it with the usually 180A plus machines that are often used.

Getting the pieces exactly lined up and clean is most of the work. If you have crud or mis aligned pieces, then no manner of special machines or gifted welders can make the job perfect, they can only make it less messy.

It is true that sectional stitch welding of alternate areas will work well in keeping warpage to a minimum. One of the best ways to achieve this is to also have a helper that can use compressed air to blow cool the weld a second after you finish doing about 20-30mm.

A wet rag will work also, but gets hot after a while and also puts water on what you are about to weld.

Practice practice practice. Don't worry I get all muddled working with wood, because I know I can't just weld back on the piece I just cut too short.dont know about compressed air and fire dont mix well
work with panel beater 20yrs only used water rags that was my job:C

[scooter]

One thing that ...


Thanks for an informative first post, Anthony, welcome aboard :)


Cheers.................Sean

[peter_sm]

dont know about compressed air and fire dont mix well
work with panel beater 20yrs only used water rags that was my job:C

Fire????

What fire? If you have fire you are obviously doing something wrong beforehand. In fact I would like to know how you started a fire with a MIG?

[tcns]

Fire????

What fire? If you have fire you are obviously doing something wrong beforehand. In fact I would like to know how you started a fire with a MIG?

I can think of a fair few ways:U, lets see, rags with thinners on bench, oily rags on bench,

And so on and so forth :o

I think he was referring to lighting the compressed air with the burning steel. I have used compressed air and have read a few other articles that has recommended it. Either way, whatever works for you

Tom

[SPIRIT]

when you weld a floor up you spend a day cleaning the crap off first or do it in 10 min and stop the crud from lighting up from inside

[ANTHONY62]

I've had the misfortune of almost being burnt alive twice whilst welding due to a couple of complacent fire watches, so I don't take any risks these days and always have an extinguisher on hand.
I certainly wouldn't take any risks with fire- even the earth clamp (return) produces a lot of heat if there is any resistance ie. paint etc. and produces sparks.

If you are considering welding aluminium at home, be aware that the commercial grade (5000 series) is alloyed with magnesium and effectively the spatter produced in the welding process is similar to a magnesium flare and will continue to produce a fair bit of heat for a few seconds - I've had it burn through my suede welding jacket and into my skin whilst welding out of position.
Just be wary of the fire risks whilst welding- the ones mentioned are only a few of the variables which come down to good house-keeping and awareness.

Regards

[SPIRIT]

the best fire we had was from grinding little did we know spray painter was puting rags with thiner on them in a 44 there was men ? running for thier life the block next to me just took off l was next bay over went to help it was like a bomb attack burning rags every where 20sqm ears were ringing for hrs so #### does happen :o
so thats where my ,,,where will fire come from story

[simso]

Been there and done that, Had to do a mig weld job on a gantry at work and half way through it the boss tells me he needs another job that needs doing about 40kms away, so I went and did the other job and came back after lunch and started welding again, little did I know that the guy in the paint shop placed an empty 20 gallon drum of thinners upside down on the angle line rack behind me about 4 ft away, started welding and caaaaaaboooomb. I was head to toe in a flash burn fire my overalls melted and I lost some hair on my head, I was disorientated and didnt have a clue what was going on, one of the guys in the workshop came racing out and ran probably about 100 metres to grab the fire extinguisher that was less than 2ft away from me but I couldnt even register that it was there. He put me out and the back half of the workshop went up in flames, my ears were ringing for days and my back was one big bruise. Everyone in the street was gawking within minutes it was that loud. Basically a sparc hit the angle line lit up the trapped fumes, and raced to the can where it exploded and turned the can into massive steel frisbees taking out all the overhead lights "2 story building". The force of the explosion from a little can was enough to lift me and through me an easy metre and I weigh 95kgs. It can and does happen out there. I count my blessings that I managed to walk out of there with minor injuries
Steve

[BobL]

Simso, you should post that story in the safety forum as an example of what can happen. My guess is not many WW read the metal work forum.

Anyway I hope you are OK now.

Cheers

[Chris Parks]

The welding incident (I refuse to call it an accident as it was sheer stupidity) that happened in the last few days in a houseboat is an example of someone not taking proper precautions and thinking about danger. Inboard boat hulls are a bomb waiting to go off and boat hulls in general whether inboard or outboard powered need a huge amount of respect due to gas and oil and petrol leakage. Forced ventilation for an extended period of time is needed. The guy paid with his life, lets all learn from it.
Stupidity in welding stories are legion. Two guys were welding a very large pressure vessel and when they finished, they leak tested it and found a leak in the top. They were standing on top of said vessel, when with the pressure still in it, they decided to touch up the leak with a quick run of weld. It exploded and they too died and these guys were professionals and should have known better.

[simso]

Okay just a little follow up on my previous post, and thanks bob all is good came out very safely. One of the earlier questions was how could you possibly catch a fire while welding or something along those lines. My story was merely to point out how easy it can happen. As far as the horrible tragedys that happen around the world, its always the welder thats blamed for stupidity ect in the inquests, people vary rarely look any further or try to find another reason. In my example, if one of the steel frisbees went threw me and I had of died, Ill bet your bottom dollar the inquest would have simply said the welder didnt ensure a safe and free clear zone. It wont take into consideration the fact that I stopped and started the job that I was required to go elsewhere during the job, that a person placed an empty drum of thinners on the metal rack ect, I would have been blamed and it left at that. There are always more than one side to any story and if your dead its hard to tell yours. These guys that die in these horrific accidents are just like you and me doing there job and its usually outside variables that end up killing them, not them doing there job. Very easy to call a dead man and idiot or morron ect, a tragedy is a tragedy but theres no need for bad labelling these people. Stupidity in welding stories are legendary. Thats a shame you should feel for these peoples families, if a clerk stuffs up his paperwork someone may not get paid ect or the order doenst get made, but in the building industry it usually results in death or impairment. We all stuff up no matter what the job, just the risks that go with it are different
Steve

[MoonShine]

Many years ago whilst in the RAN, we were told that a fuel tank cylinder is extremely dangerous when near empty. This applies to the usual cars fuel tank, or a huge LP gas tank.
Seems commonsense is out the winda with some, regardless of their occupation, qualification and supposed knowledge.

You want to try doing an Occ Health & Safety course and see how many in that classroom are destined to commit suicide in the workplace, just by their demeanour and behaviour in that classroom. I'd say without exaggeration, 2 out of every 10.

I sat here in Adelaide and watched the evening News covering the houseboat incident, and wondered why the hell this bloke didn't think to take into consideration, fumes?
Not casting aspertions upon anybody, but it was just another case of not doing your homework before attacking a task. Slack!

I've worked alongside people in the building industry who take chances/shortcuts every day, and doesn't it surprise you that they just happen to drive a car the same way? reflecting their attitude.

When I was a Weapons Mech in the Navy, we had 'em in the Magazine whilst priming projectiles, we had 'em on the Rifle Range.

They're out there, been living my life in the workforce hoping their stupid actions don't take one of my mates, or me, out.

I grimmace of the thought that many years ago I saw a fella in a Wrecking Yard firing up an Oxy -Acetylene to cut up a supposedly empty fuel tank???:no:

Sorry but I'm pretty passionate about this subject.

[ANTHONY62]

44's have two seams- upper and lower, that form the rims- knockover seams for want of a better term. Over time, the contents of the drum gradually leach into this formed seam. No amount of steam-cleaning or whatever is going to penetrate that rolled seam, so when you go and cut that drum in half, an amount of those contents is present within this join.

Something to ponder when the contents of that drum are unknown.

[Grahame Collins]

Moonshine,
Spare a though for yours truly then.I agree with your statement but in my case I reckon its about 4 in 10.

Attitudes to safety amongst our school kids are sometimes just appalling
We have just started the new lot of year 11 Engineering kids. Gave them the standard instruction lecture of safety and expected behaviour in the workshop.I am real big on them not walking off from a lathe and leaving the chuck key in the lathe chuck, among other things.There are machine shops in this town will sack a machinist for doing that.

I specifically tell them "your hand never leaves the key while its in the chuck"
Half an hour later a smarts rrs cherub rocks up and announces in a loud voice about fellow student leaving key in the chuck.
The thing is, that the kid(the lathe operator) was innocent, he had nothing in the chuck and was getting stuff ready and had no reason to use the key at that stage.

I am sure this loudmouth had attempted to set him up. Being an ex boilermaker political correctness means little to me.
A quiet word to the suspected miscreant and mention mention of dire consequences far exceeding school behaviour management practices would have better effect.

The scary part is that some of these wombats will have a license to drive in less than 12 months.

Stepping down off his soap box
grumpy Grahame

[Uncle Bob]

Years ago, While I was working as a labourer in a Plumbing and Sheetmetal shop. We had a job come in to alter a boats aluminum fuel tank. I got the job of flushing it out. It was left with water flushing it out for hours, and a few wash outs with detergent. I thought it must've been clean as a whistle and the shop foreman agreed. So he put it on his workbench and decided to strike an arc with this TIG torch on the filler neck just to check for a start.

Well BOOM, it flew a good 6 metres up through the air bounced off the roof (after denting it) and came back down and hit him on his shoulder. The explosion smashed half a dozen windows in the workshop and made a dust storm that you nearly couldn't see through (dust in the right concentration with air is a explosion hazard in itself).

The Foreman was ok besides a sore shoulder and ringing in his ears (all of ours were too). Mind you, he was half deaf from years of sheetmetal work. The fuel tank was a write off, and looked more like a half peeled banana and was built totally anew.

It was scary stuff, though once the dust cleared and found everyone was ok, we laughed a bit about it. To this day there is still a reminder of the incident, above this bench, the dent in the roof.
We all learnt a lesson, big time.