Arc Welding

[Tweed]

What types of metal are suitable for arc welding and if joining two pieces do they have to be the same type?
And, when welding two pieces together which piece does the earth clamp connect and on which should you strike the electrode? Should the two pieces be electrically bridged (if a gap exists between the pieces)?

[gonzo00]

ahhh! this could get long winded!
basically only steels and steel alloys such as stainless steel,titanium,inconnel etc are suitable for arc welding but in modern day practice only steel and stainless steel would be arc welded. titainum etc would be tig welded.

as electricity flows downward in circles the earth (or to give it it's proper name RETURN) clamp should always be placed on the lower part of the workpiece,this would eliminate a phenomena known as arc blow..although if you ever find yourself in a position where this is not possible eg. the earth clamp has to be above the welding position,you must ensure that you are welding with ac current as arc blow only occurs when using dc current. so in short...earth clamp to the bottom piece and strike electrode on upper piece moving downward to encompass both pieces to be welded.

if a gap exixts between the two pieces....i've never known two pieces to be gapped and then bridged although i'm sure it would make sense to do so..in practice the gap will be there for a reason eg to perform a full penetration root run and the gap would usually only be a few millimeters and the arc would be more than capable of bridging this gap itself. i hope i've been of help..maybe i could have explained it a bit better but i'm only a layman..lol!

[Tweed]

Thanks for the info Gonzo00. I think you use a gap when the pieces are too thick that a beaded joint won't do (the weld penetrates the gap so the whole width is used for strength). When I try to weld two pieces together I end up running a bead along one of them and the other piece is left with just burn marks and still seperate from the other. I assume that electrical continuity would have to be maintained between the two pieces mechanically and that the arc would not be sufficient to do this.

[gonzo00]

are you maintaining too tight an arc??? try welding with the tip of the electrode about 4/5 mm from the workpiece and dont rush the weld...give the bead time to build and fill out...i've never had to bridge any two parts to weld them the arc should do this for you. the weld bead should be wide enough to "cover" both edges. alternatively use a little bit of weave to ensure you catch both sides.

[Tweed]

It's a 100A welder and I'm using 2mm & 1.6mm E6013 electrodes. I only bought it on Sat. I am, as you say, probably rushing it. You go through half a rod and think you have too big a blob so you stop and when the scag is removed the weld is about half the size. But, I find if the arc is too long the weld is bubbly. Is it enough just to let the bead cover both edges; will this be hot enough to melt the other piece to fuse them? It's a bit frustrating as I can do the bead row exercise but just haven't been able to join two pieces together. And I've run out of practise material. Your advise is much appreciated.

[gonzo00]

hi again tweed! ahhh..if you're using a 100 amp welder then things are a little different.. firstly 1.6/2 mm rods should burn nicely at 60-75 amps and you will have to keep quite a tight arc as if you pull away then the arc will struggle to jump the gap. try to let the weld build up then start to move off and weave a little from left to right to spread the weld fillet onto both pieces making sure that you touchdown and pause slightly on both sides of the weave,this will ensure that you "catch" on both sides.......damn! it's so difficult to explain..if i could get you here to my workshop i'd have you welding like a pro in ten minutes!!!....as you are using a 100 amp set i would amend my first answer i gave to you and tell you to strike the arc on the same plate as the earth clamp is attached to as this will help to start the arc more positively. please try the weaving bit as i'm sure it will help..it may take time but please stick with it.
as for practice material...stop into any reasonably sized engineering/fabrication workshop a have a chat with the lads..ask if you can have some bits of steel from thier offcut's bin to practice on..they won't mind as the price for scrap steel is so low these days! don't try to do a butt weld straight away..try to do a fillet weld first...lay one plate halfway over the other plate and try to weld along the join catching both the top and bottom plates..weld from left to right and at 45 degrees to the joint. let me know how you get on.

[Tweed]

Howdy Gonzo00. I'm getting somewhere now in my attempts to weld. I think I attempted dificult pieces to start with like different metal types, thin tubular poles and nails and the like. But I've cut a 3mm steel tube in two and welded it back again, letting the arc and the blob create the bridge (yes?). It's not pretty but does the job.

I'm a bit curious about it being different for a 100 amp welder though. Why is this if 75 amps is adequate for 2mm rods? Why would a bigger setup (more available amps) be better. Ta again.

[gonzo00]

well..thats all to do with "open circut voltage"! basically when you strike an arc it takes a lot more power to strike the arc than it does to maintain it...we're talking voltage rather than amperage. so your welding set creates big power upon striking an arc then settles back to the voltage required to maintain the amperage to weld. a larger welding set has a much larger open circut voltage than a smaller set so this is why it's easier to strike an arc with any size of rod when using say a 250amp welding plant. glad to hear that you're making progress ..stick with it and soon you will be amazing yourself with the welds that you can lay down! i once asked my journeyman (welding since the forties!)who i was an apprentice to.." what's the best weld you've ever done"???
he replied.."the next one"..it was years later that i realised that he meant as a welder you should always be improving and never assume that you know it all!!! good luck mate...find me on cb if ya ever need any further advice. :0)

[gonzo00]

ps. re.(yes?)....yes,thats the way to do it..you've got the hang of it now!! let the arc bridge the gap!

[Tweed]

Well explained there Gonzo00. I just need to practise more and have a little patience. I do intend to actually make something once the skill level has developed a bit.

[gonzo00]

meant to ask..what kind of things are you gonna be making?? i used to teach a welding nightclass at a local tech..came across an unusual selection of people who were wanting to make all sorts of weird and wonderful things. one slightly strange guy was learning the skill to make....bondage equipment!!!!

[Tweed]

Hello again Gonzo00. Well it certainly isn't for that sort of thing anyway. I'm getting some good results now. The first thing that comes to mind that I want to make is bespoke speaker stands, with spikes at the base, that can hold a 15kg load at a particular height. But, I'm just into this sort of thing anyway and it's good to add a new string to my bow so it's there when I need it. Re: your journeyman friend. It's so true; we should never be so arrogant to think we know it all - we are, and should think of it this way, always learning, no matter how experienced we think we are.