What power do I need for thin metal?

[MattS]

Hi All,

So I am new to welding (I did a welding course where I did a bit of Arc and MIG welding and I preferred Arc welding).

I am looking to weld some steel SHS box sections together (35mm x 35mm x 1.5mm or 2mm). This leads me to my first question..

What sort of power will I need to do this?

If I used too high a power could I burn through 1.5mm?
But too low a power wouldn't weld 2mm steel SHS?

I am looking to buy my first cheap-o Arc welder something like this:
http://www.machinemart.co.uk/shop/product/details/010110942?da=1&TC=SRC-arc welder

But I am not sure if this is going to do the job I want..

Any help is appreciated!

 

[BrokenBiker]

For 2mm about 70-80 amps with a 2.5mm rod. For 1.5 you want about 60 ps but that is right on the bottom limit of the 2.5mm rod, i would use a 2mm rod.


if you are joining the 2 then set for the 2mm

 

[MattS]

I'm aiming to weld the two box sections with a 45 degree cut. Will the 2mm make much more of a difference than the 1.5mm? I want it to be as light as possible (also the 1.5mm is cheaper than the 2mm) which makes my girlfriend happier! haha.

The Easi Arc welder apparently goes as low as 40 amps (up to 100 amps). So it should be able to weld a 1.5mm box steel section?

 

[BrokenBiker]

put a 2.5mm rod im, around 70 amps should be plenty. Weld slightly bias on the 2mm section and keep an eye on the thinner side and watch for it to start to blow through, pick speed up a bit if it does. It wont be too hard to join those two if you keep a tight arc

 

[PTvor]

You can weld that together with arc and 1.6mm or 2mm rods, I've done things like that with 2mm rods at 55A, with an inverter with the electrode negative. You'll find it's tricky though, particularly the outside angle on a 45 degree joint will drop into holes very easily. You need good fit up.

You'd probably be better off practising with 2.5mm rods and some 3 to 4mm steel first.

 

[sardine]

I weld 2mm sheet and tube with a 2 mm electrode, 1.6 ' s are a PITA I find. If the fit up is bad or thinner metal i use overlapping tacks method, a full penetration tack, spaced apart, clean off slag and repeat until you fill the joint. You can grind off and lay a stringer over the top if you want neatness. It also cuts down on distortion.