Thread: Welding applications and thin metal

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

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

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?

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

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

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

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.

Originally Posted by 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.

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

Originally Posted by ANTHONY62

One thing that ...

Thanks for an informative first post, Anthony, welcome aboard


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

Originally Posted by SPIRIT

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

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?

Originally Posted by peter_sm

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, lets see, rags with thinners on bench, oily rags on bench,

And so on and so forth

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

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

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

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
so thats where my ,,,where will fire come from story

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