Thread: Calling TIG experts - motorbike related.

Originally Posted by chancho196

I've just bought a Weldsmart TIG200P welder because i want to be able to make my own stainless exhaust pipes, repair aluminium covers and carry out general repairs.

I've read a lot about how clean the workpiece needs to be when using a TIG, but what about when welding to an old motorbike frame where the rust is only on the inside of the frame tubes?
For instance, when repairing cracks or adding brackets to a frame tube, the outside surface could be clean and shiny, but the inside could be badly pitted. How much grief will this cause? The mild steel rods are supposed to be good for slightly dirty, rusted metal so is this the key?

Cheers folks.

No problems whatsoever unless the section is so badly rusted/thin that you actually melt through the tube. I don't know what your sources of information have been, but tig will put up with a fair degree of contamination on steel while still producing good results. Just don't try welding galvanised or zincseal with it as the nicely sharpened tungsten will have a ball of crap on it in about 2 seconds flat! Only use filler wire designed for tig welding as the lower grade oxy welding fillers are not triple deoxidised and will produce poor results.
Aluminium and magnesiun need to be cleaner of course due to the tenacious oxide layer they possess.
The secret to tig welding is arc length, heat control and correct gas flow for a given shroud size, a short arc and a small shroud using DC and a bit longer arc and a larger shroud using AC.

Thanks Karl, that's a great help and makes sense. I was thinking I'd be penetrating through to the other side and dragiing rubbish back - not the case if done properly!

As soon as my mate has fitted the 15A supply in the garage I'll be practising.

Not sure if this is relavent but if making repairs to motorbike engine casings, they usually contain a percentage of magnesium in their construction. There are alumiuium filler rods available that contain a percentage of magnesium which would help to make your weld/repair more successful.

Thanks Pete, great help. Got a few cases to repair too.

Loving this TIG! So neat. Repaired a few cracks in the frame and really impressed with the results.

Are there any limits when welding a mild steel frame such as this in terms of cracking/heat stress etc.? Will I find out further down the line?

mate when your welding those casings up you might want to bolt them to a piece of thickish plate ( 1/2" 5/8 " ) drill the hole pattern and assemble the prepared case to the plate and weld it out . let it cool and unbolt it from the plate, it will warp otherwise and probably crack again when you bolt it back on the engine.

Top bloody tip! Thanks old mate, never thought of that.

Originally Posted by chancho196

Thanks Pete, great help. Got a few cases to repair too.

Loving this TIG! So neat. Repaired a few cracks in the frame and really impressed with the results.

Are there any limits when welding a mild steel frame such as this in terms of cracking/heat stress etc.? Will I find out further down the line?

Cracking/ heat stress can be reduced with preheating and slow cooling of the welded part. The degree to which you do this, for me, depends on how critical the component is in term of brittleness of the parent metal, and induced stress which the component will have to endure. Mild steel is fairly tolerant but if you can preheat the weldsite, the weld has a better chance of not cracking just beside the weld. You need to think about the microstructure of the metal being welded.If you weld a cold joint, you are heating the weldsite metal to melting point so you can add your filler,this changes the microstructure of that metal at that point.The metal beyond that point is nowhere near that temperature and therefore there are induced differences in microstructure which create stress and fracture points. Thus, cracking just beside your nicely laid weld.
Hope this helps.
PS: I love my TIG,wouldn't be without one. Do you have a foot control with yours?

If you haven't already, get yourself a stainless steel wire brush for aluminium/magnesium. Using a standard wire brush will contaminate your weldsite.

Yes, got the foot control but only really practiced with it so far on aluminium. If I panic when finishing the weld (trying to be neat) I sometimes floor it instead of letting off! It'll come with time I'm sure.

Interesting points about the heating up first. Makes sense. Oh, and I do use the stainless brush on my aluminium bits and pieces.

Originally Posted by chancho196

Yes, got the foot control but only really practiced with it so far on aluminium. If I panic when finishing the weld (trying to be neat) I sometimes floor it instead of letting off! It'll come with time I'm sure.

Interesting points about the heating up first. Makes sense. Oh, and I do use the stainless brush on my aluminium bits and pieces.

Geez, I'm not coming near you in a parking lot!! Just imagine you're finishing your parking manovure and you hit the loud pedal.....Into the crowd of pedestrians you go.

It's alright, I don't use the welder for parking.

Gold.