Trying to weld tubing, but no good?

[frustratedwelder]

HI Guys,

Im trying to weld 30 X 30mm steel tubing I bought from an engineering shop to make a suitable ramp for my motorcycle to run down. The only thing is is that the tubing will not be welded, Im using a Cosmo Mig with 0.6mm (a bit small I know) wire and gas but cannot get a decent weld at all, it seems as though the steel isnt melting and the wire is just blobbing on the top, the resulting weld will hold for a while but just breaks as soon as any pressure in put on it. Now ive tested the mig and get good welds with other bits of metal...

Ive welded loads of things before and would like to think im reasonably ok at it but this has got me flummoxed!

Could it be the wrong grade of the steel (carbon steel?) or what?

Cheers
Steve

 

[malcolm]

Welcome to the forum

You say tubing so it's not solid (thankfully). What's the wall thickness of the tubing? And which type of Cosmo do you have? It could possibly be an incompatibility problem between size of welder and tubing (for which there could be ways around).

 

[frustratedwelder]

HI, thanks for the welcome!

The tubing is 2mm thick, the welder is a Cosmo Gasless (thats all its got on the box) and like I said, I cannot get anything to weld to this tubing, its like the metal isnt being melted at all by the heat of the welder (the welder is on its highest setting by the way) and everything is just falling off it!

 

[Wozzaaah]

If it's a dual purpose machine (Cosmo 130) then it may be factory set for gasless in which case you have to change the torch polarity for solid wire. Positive for gas, negative for gasless.
Have you previously used it with gas or is this the first time? What gas are you using? Can you post some pics of the machine, and the welds?
Lots of questions but it will help diagnose your problems.
Oh and welcome to the forum

 

[malcolm]

I can never rember which way around, but the polarity ought to be changed when going between gasless and normal gas shielded welding. This might be handy:

The big difference was with gas. With the wrong polarity had no penetration and weld sloppily piled up. It was as if the drops from the wire were repelled by the metal and thrown around.

I was using a minimum wire speed and 1/8" steel. Later I learned that a faster wire speed worked better.

I think when you are set up with the right polarity for gasless wire all the energy goes into melting the wire and less of the stuff goes into melting the actual metal.

Any numbers on the Cosmo? Such as 90 amps max? You can reduce the amps required by grinding a V shape in the metal you want to weld. See my experiments with a Clarke 90 amp welder.