Welding Chromoly Cage ?

[zim]

Evening,

Not LR related, sorry

My brother is looking for another cage for his track day peugeot 106. OMP do a chromoly weld in cage.

I've been searching google, and have read mixed reviews about not using mig on it ?

What are peoples thoughts ?

If it's tig...then i'll get him to buy the half welded cage to save us work !

Cheers

Gordon

[forkrentfitter]

i think custom cages can supply a suitable mig wire for cromoly,but it is kin expensive!!!!!!!!

[B reg 90]

You want the right wire to get a weld that has the same properties as the tube, other wise your buying fancy high strength tube then doing a mild steel weld at the ends, kind of defeats the point...

However before you buy a chrome molly tube consider the heat treatment side. Cromo tubing will be available in different conditions, i.e. annealed up to be heat treated to get a higher strengths - they will probably be using anealed tube otherwise it would be a bugger to bend. When you weld the tube the welds will cool rapidily and create a hard 'brittle' (compared to the tube condition)section at and around the weld (Heat affected zone - 'HAZ'). Theoretically to get the same strength/ductility through out the cage you need to do post weld heat treatment. That said I understand that it's rairly done.

Adrian

[longlandy]

Nothing to add to the above other than tig is my prefered, though there has to be enough weld bead as is specified on structural drawings for other critical/load bearing parts.

All to often one sees a tig weld with just a surface fused joint and undercut

[dangerous doug]

all the frames on my bmx (that i havnt broken) have been made from 1430 cromolly there ALL tig welded, for that sort of thing you would have thought mig would be the cheaper quicker option but there all tig. enough said i think.

[Hybrid_From_Hell]

or is it 4130 cM ?

If so then er70-s6 tig rods is what I understand to be the babies, and erm "Not Cheap" is an understatement

However, you need to be sure what spec the CM is so that you can match to the most suitable rods, guessin' is not a great idea

Posty up spec of the tube ?

Nige

[brighouse shed]

Nige is spot on, TIG only as it's a controlled weld so good heat spread, essential you get spec of alloy then select rod, if you struggle try metrode who are superb and they will sort you.

As previous post usual quality rules about undercut apply.

[Kobold]

TIG +1

[inaine]

There will be bits you wanna Tig and bits you'll wanna Mig

If wires expensive then Tig will work out cheaper, remember to cut the holes in the floor and drop the cage down to do round the top of the roof bars

If your not compitent on the Tig hire a synergic pulse mig, mine runs it in so well you can even program the ripples into the weld like Tig!

[integerspin]

Long time since I welded it, I used normal A15 rods, which is what most chassis builders

use as far as I know. I think A18[ER70S-6] rods n wire are more or less the same price as A15s.

Will be plenty online about welding 4130.