Welding steel tube

[ms08]

I need to weld a new flexi into my down pipe - 3" - what is the best way - chamfer the ends and butt joint so i weld into a 'V' , just butt joint and weld or leave a small - 1mm air gap and weld between the two. I think the original might be stainless so will that cause problems and do I need to change wire. Original was TIG welded.

 

[the black box]

Tube should slide inside the flexi to give the joint mechanical strength otherwise it'll crack very easily. I suspect the flexi will need to be swelled to allow this.

You can weld stainless with mild steel wire obviously joint will corrode and can get cracking.

Also on flexis around the collar take a bit of the coating off around the edge you are to weld to and send each end flat makes them easier to weld as the collars are usually aluminised mild steel

 

[ms08]

Many thanks...I assume I should try and cut the flexi in half cross ways and then clean off the existing flexi carefully without shortening the exhaust down pipe itself marking up the front and rear sections so they remain in the same position in relation to each other?

 

[the black box]

Yes that's one way of doing it. Just be careful that the new flexi is straight and not under strain otherwise they don't last long!

If you have approx 50mm of straight undistorted tube (i.e. Not close to a bend) either side well worth considering making it clamp on just for easier replacement some flexis available are of dubious quality!