Welding thin ally tube to flat sheet question

[topcat]

Hi all, I have a nice ally fuel tank I have got to weld a small breather on to, I have only done this once or twice in the past and I was never very happy with the result.

Is there any tips to get a good result? The problem I seem to remember was the tube (8mm 1mm wall) blowing through before the sheet is hot enough to weld. Is more pre-heating the answer? I can't put a copper bar inside or anything as a heatsink as the tube needs to be bend first (unless I can do it after...)

Any input welcomed!

Thanks,
TC

 

[pedrobedro]

Is the tank metal thicker than the tubing and does the tube go through or butt up? You need to weld on the thicker and let it wick over to the thinner

 

[FranV8]

As Pedro says, I tend to start the weld bead a few mm away from the thinner item, then just move over quickly to get the weld pool edge to fuse with said thinner item.

The key is the right welding current, not so fierce that you blow holes, but not so low that you put so much heat in by the time you get a pool established that everything goes. if you can adjust frequency go for a higher one too to concentrate the heat input.

 

[topcat]

Thanks for the replies, I have done it now, just kept the current fairly low with a 1.5mm tungsten, the tube was about 1mm thick and the tank must have been 2mm, I started on the tank a couple of mm away from the tube and let it wick over as you also said, worked fine just quite slow. I don't know how these other guys who fab the tanks up get the same big bead welds around such thin tube without it melting! I just did it slowly so there is no beading effect but I'm sure it will seal ok as it looks good

 

[derekm]

Hi all, I have a nice ally fuel tank I have got to weld a small breather on to, I have only done this once or twice in the past and I was never very happy with the result.

Is there any tips to get a good result? The problem I seem to remember was the tube (8mm 1mm wall) blowing through before the sheet is hot enough to weld. Is more pre-heating the answer? I can't put a copper bar inside or anything as a heatsink as the tube needs to be bend first (unless I can do it after...)

Any input welcomed!

Thanks,
TC

Heres what i do
Weld a sheet metal flange( more like an ally washer) to the pipe. Then weld the flange to the tank.
Or run a bead round the pipe first. let it cool then weld the bead to the tank.