4130 weld question

admin

Hi all, new to forum. I have been gas welding 4130 for a long while and like it, but now I am involved in a project that I have to make some fairly complex jigs. It would be much simpler if I could make small  tacks with a mig, then go back over with the torch once the fixture is removed. Do you see any problem using this process. I would grind the tacks back of course before the finish welding.  4130 tubing, .065 wall and thicker.   Thanks, Jim
Reply:shouldn't be any issue grinding out tacks.  If the takes are within the weld joint and can be feathered usually don't even need to be fully removed.If you have access to mig, any overriding reason you don't weld it out with MIG? much faster than gas and cheaper consumables wise.
Reply:I imagine that the work you are doing is on plane parts and if it is I would stay with the one weld process you are welding with.  If you are gas welding or tig welding  I would not mix in any mig.
Reply:It shouldn't be a problem when following up with gas welding.
Reply:The professional aircraft weldors say NO. Primary reason is from quench cracking that can be caused by the rapid cooling of mig tacks. These cracks go through the thickness of the tube, and overwelding them does not get rid of them. Fatigue cracks start from this point. Not to mention oxide inclusions from going over the tacks and having the puddle "fizz". Tack with OA, weld with OA. Mig is not even suggested in any manual for aircraft parts unless from a manufacturer. Good Luck-Aaron