Welding for beginners

[Sixpence]

All plans for this weekend have gone up the spout for one reason or another so I end up with the unenviable repairs to a steel framed pool . I left it empty overnight for one night during the winter and we just happened to get hit by a storm that night which bent a load of the T piece legs . Where the upright meats the T piece some of the welds have split so although I've managed to straighten them all out , I need to weld the joins again , and also reinforce the others.
So I had a go with a stick welder but the only rods I have need a fairly hefty current to work properly which blasted holes in the first attempt so I switched to the Tig welder ( could be Mig but I think it's Tig ) . With the power set to minimum there were some joints where the thing still blasted a hole and others where it had almost no effect at all so I ended up constantly changing settings to get it to work .
I've finally got all the legs repaired , and ground to a half decent finish but , here comes the question .
Is there any way I can tell if the weld has actually worked , short of putting them through the storm test again . Also , if anyone has any tips on welding they would come in useful to me as you've probably guessed that I'm a total amateur when it comes to sticking bits of metal together .

 

[pete]

For thin metal eg tent poles I used to use my stick welder with a carbon arc attachment ( like large pair of insulated pliers with the rods attached at an angle so as they almost touch and so form an arc FLAME) and braze the joints ,it is much more manageable and a slower process and you can see the brass flowing into the joint obviously you will need the brazing flux to go with it. With this method you would have to go mad to burn holes.

Or use a gas plant.

Hope this helps

pete

 

[savageseadog]

Suggest a mig welder lots of gas flow (Argon/CO2 mix) and 0.6mm wire. For thin stuff you need to do the welds in short bursts perhaps 1 second at a time.

 

[Sixpence]

That's something I hadn't thought about , I was trying to do it in continuous runs , could explain the burn throughs

Pete , that sounds a bit like doing a plumbing joint but with heavier metals but do the rods extend automatically ? if I'm understanding what you mean

 

[pete]

Sorry I should have explained better The holder is sprung, and as you squeeze it the rods go together, relax and the come apart so when the rods very slowly wear down you just squeeze a bit more. This is very controllable and I have used it to fit many wings and body panels to thin metal on cars But I don`t know if that is still allowed (though if not I don`t know why as once they have been brazed on they certainly very difficult to remove later.
Look here http://www.welddirect.co.uk/welding.php/Tools/6_96
and here http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=1;t=021593;p=0
pete

 

[Sixpence]

That's great thanks Pete , some very useful links too

 

[misterg]

[ QUOTE ]
Is there any way I can tell if the weld has actually worked , short of putting them through the storm test again.

[/ QUOTE ]

Penetration! (sorry /forums/images/graemlins/blush.gif)

You need to make sure that the weld you've added has melted through the full thickness of the bit you're fixing. Ignoring complications about trying to weld dissimilar metals, this is the main thing to watch. If you're trying to weld up a crack, it's normal practice to grind it out, such that there's a gap which you can fill with weld (unless it's in something dead thin, such that one pass with the welder will penetrate the full thickness).

If you were using TIG, you would should have a separate filler rod. I assume you were using MIG where the filler wire is fed automatically - much more common.

Get the settings roughly right by laying down lines of weld on a flat plate the same thickness as you will be fixing - You should be able to get a neat line of weld on one surface, and if the amps are right, there should be a melted line on the opposite side, too. If the weld pool 'fizzes' and blows sparks, there's a problem with the gas flow / draughts - it's not easy to MIG weld outdoors if there's any breeze. (I suppose you might be using a MIG with flux cored filler wire, which doesn't need gas - never used one of these).

You get the best feel for it by listening and watching what happens when you weld - does it make a continuous noise like sizzling bacon? Are the edges of the parts 'rounding off' and melting into the weld pool?

Once you can lay down lines of weld on a flat plate OK, make some test welds in similar parts, and then rip them apart - the failure should be in the parent metal (maybe close to the weld).

If you're welding zinc plated / galvanised / zinc passivated then:

a) The fumes are very bad for you, and
b) The heated areas will corrode like mad unless you protect them.

Practice, Practice, Practice.

I used to have a VW camper, so I've had lots of practice.

Andy

 

[Avocet]

Depending on what the pieces are made of, it can be extremely hard to get a good weld. Some grades of steel are difficult, if not impossible to weld with a MIG set. When I was a teenager, I decided to try and make a dinghy trailer out of "Dexion" pressed steel shelving. That's very high tensile steel and didn't take at all kindly to our attempts to weld it! It kept cracking round the edges of the welds. Assuming your bits were just mild steel, the only advice is, as has already been said, don't build up too much heat - just keep spotting them together in short bursts. Absolute cleanliness (no paint or rust) helps too. As for testing, no, I don't know any non-destructive way. If you had a spare bit, you could put it in the vice and heave it backwards and forwards until it broke - making sure it went at the side of the weld rather than through the middle of it. If you can see both sides and there are signs of penetration, you're probably OK.

 

[Lakesailor]

I used to go grass track racing with a mate who was a builder's merchant Ergo: all our roll cages and nerf bars were made of scaffold pipe, which is galvanised water pipe. Stick welding galvanised pipe really taught you to weld properly. It was so easy for the clag to build up and prevent a proper weld that you learned to listen to the welding. That way you could tell if you'd got rid of the treated surface and were stitching real steel.
Similarly, I learned to gas weld on rusty cars and old exhaust sysetms. After that real, new, steel sheet was easy peasy.

 

[Sixpence]

Seems I may need to have a lot more practice because my welds were more of a big blob that needed a fair ammount of grinding so thanks for the tips

 

[BrendanS]

Banger racing was the same. We used scaffolding poles as cheap resource, to make the roll cage.

I never did the welding but it held up well if done by someone that knew what they were doing.

Wouldn't get onto the track these days I suspect.

 

[Lakesailor]

Def not. It's all seamless steel tubing and radiused bends these days.

 

[BrendanS]

shame, we used to buy a car, get it welded up, race it, then sell it same day, paying for our costs.

Could never have done it otherwise. These days even banger racing would cost a fortune.

 

[Sixpence]

Friend of mine does banger racing , he picks up cars due to be scrapped , clears them out and kits them with a single roll cage that when he wrecks that one he takes the cage and fits it to the next car . Doubt he's doing the right thing but he enjoys it . Does all the work himself so saves on labour charges

 

[Lakesailor]

Our transport was a builders merchant's wagon. We loaded the car on 10ft long steel channel section. That was nearly as exciting as the racing.

 

[Sixpence]

Mate uses a beaver tail recovery truck , he dropped off one of his cars here to be converted in the barn , he had it secured via the winch cable to front bumper , front bumper obviously stayed put while the car rolled down the ramp and ran into the barn door . The doors never closed properly since , I never stand behind him when unloading anymore , but he insists that he secures properly now . Somehow I don't feel like taking chances

 

[misterg]

[ QUOTE ]
Seems I may need to have a lot more practice because my welds were more of a big blob that needed a fair ammount of grinding so thanks for the tips

[/ QUOTE ]

MIG welds are never the neatest (IMHO) - If the weld has penetrated through the original part, then you should be OK (can you look at the 'wrong' side of your welds?). If not, you may have done very little to repair the piece - If all the metal you've put on sat on the surface, and now you've ground most of it off, there's no strength in it. (This is easy to do with MIG, IMHO, particularly if he parts aren't very clean / rust free.)

Seriously, I would try and snap one - if you can't manage to, it's probably fine (assuming future failure would be a PITA, rather than life threatening).

If you do re-weld, try slowing the wire feed down a bit, and if no better up the amps (& stop welding after a couple of seconds). In fact, are you sure the wire feed is operating smoothly? You mentioned having to constantly adjust settings - it could be that the wire feed is playing up - this will mess you up big style, and make it impossible to get a good weld. Typically, if a MIG set has sat at the back of someone's garage for a while, the wire gets rusty, and starts jamming in the sheath. If you're lucky, it's only the outer layer on the spool, and you can pull it through and discard it. Make sure the 'lead' to the handset isn't kinked, or bent too tightly because this stops the wire feeding, too.

Worth getting it right.

Andy

 

[Sixpence]

Thanks Andy , luckily the T pieces are about six inches long with a bend in the middle and although it looks messy on the inside I can see plenty of metal there so maybe I did it right after all . There's about the same ammount of blob inside as there was on the outside

 

[William_H]

Just for the record MIG welding involves the constant feed of the welding rod (wire) via a motor drive (adjustable) to a head where the arc from the end of the wire is bathed in the inert gas.
TIG Tungsten Inert Gas welding uses an electrode of tungsten which does not get consumed (much) it operates under a ceramic shield which holds the inert gas in the weld area. The actual weld rod is fed in by hand a bit like gas welding. olewill

 

[Sixpence]

Thank you very much for that William , I must admit I didn't know there were so many different ways and your post confirms that I used a MIG setup