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Is it worth welding ?

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cardiff_gareth:
The floor is not a structual part of the body so not required for an MOT, I have just changed my floor, hence the welder settings. If I was you then I'd leave it til last and concerntrate on the other parts which are more life threatening for a better phrase.
What level is the oil in the gearbox, seems daft but you never know, as stated, a change of oil can help wonders, are all gears hard to find as could be the selector plate in the top of the gearbox ?

Get an angle grinder with a grinding disc - I take it under the bonnet would be inner wings which are a swine to do, you need to remove the underseal as this is what catches fire when welding. Make your plates up with some sheet steel and then place them over the metal to be welded to. Draw around them and then angle grind both sides of the metal with the grinding disc to remove the paint and also the underseal. This then makes a better weld and also stops things catching fire.
I personaly would remove all rotten metal, make the plates up and treat the old metal with rust stopper before welding on new plates, paint on seam sealer followed by hammerite and finish with waxoil, that ain't never gonna rust again !
Oh yeah, disconnect the battery before you start :wink:

Leslie Henson:
I spoke to 2 MOT testers today and also posted on the MOT testers website. All so far have said that there is no restriction (or even mention) of gas welding being used to repair a body or chassis on a vehicle. The only comments were 'we have to pass some s***t welding done by any method - gas is not a woryy, just that the job is done properly. Perhaps those of you that have said that gas welding is not satisfactory for the MOT could say where you got this information from please?


Les.

Tyke:
Ok . . . . so what's mig and tig if not a form of gas welding . . . . . I know the gasses are just used for shielding but I can't for the life of me see a problem with oxy-acet . . . . . if done well and properly.



Anyway, most of the Disco body is non-stuctural, so corrosion shouldn't be a major issue for mot. All down the testers 'discretion'. . . . and their desire to screw you for a load of welding that may actually be, technicaly, unnecessary :evil:



If body mounts and seat belt anchors are sound the Disco should pass mot . . . . even with great big holes in the sills and floor . . . .  :lol:

Tyke:

--- Quote ---as i understand it oxy-acetaline welding can incoroperate oxygen from the atmospere into the weld (making it weaker) compared to MIG/TIG/MMA which produce inert gas sheilds around the weld preventing the oxygen entering the weld.

--- End quote ---



And while were at it . . . . we are dealing with low carbon steels on vehicle bodywork that do not react to heat in the same way as higher carbon structural steels.   The main issue is with the change in structure of the material, due to heat,  which can result in brittleness and subsequent 'stress corrosion' in the 'heat affected zone' . . .  HAZ to those who understand.

Generaly these effects are of no significance on a typical body panel as the material is seleced for it's ductility and structural strength is imparted to the panel during the bending and forming processes during manufacture. Application of heat, during welding, does not change the materials structure as the carbon content is too low. It may cause local annealing of the material, however, but this is somwhat less of a problem than local hardening . . . which can cause stress boundary failure on some steels due to the development of cracks caused through fatigue. This is often found along the boundary of the base metal and the HAZ and is the result of welding a medium/high carbon steel at too high a temperature . . . . vehicle body panels don't fall into this bracket of material.


To be perfectly blunt about it . . . . most vehicle welders i've ever spoken to don't have a clue about such things and which welding process and the critical temperatures to choose for a given steel or other material . . . . but hey . . . . that's what happens when you don't have the background knowledge . . . . then they sting your wallet . . . . especialy if mot's are involved :x

waveydavey:
The fact is that a gas weld done 100% properly is much better than any sort of electric weld but there are problems:

1; gas has a size limit for the parent metal (not a problem on vehicles but you can't weld 50mm thick steel plate with gas.

2; it's much easier to get gas wrong, especially compared to MIG.

With electric welding you have a very small 'hot area' which inevitably cools fast and will induce stresses. With gas you heat a greater area and control the cooling.

Mig is easiest to learn and certainly best for a home user but for vehicle welding there is nothing to beat a good gas welder (not me!).

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