Having problems

[coyoteboy]

OK I'm fairly practiced, though not *that* experienced, with MIG welding. I've managed some lovely welds on 1.6mm bar, both butt and lap, and I've been practicing in the garage with sheets down to 0.7mm and managed just fine to lay some nice clean smooth welds (with the odd hole on the thin stuff, but I can quickly re-fill those with weld). I've arc welded 3mm+ beams, and have done some bodywork in the long distant past. I've used both a large industrial rig and my little migmate 130, and been fine. Until it matters! I moved to working on two large patches for my sills (700mmx75mm), and I've had a nightmare. The sill material is 0.9mm, the patch material is 1mm and sat in behind the hole in the sill so it forms a nice overlap inside which I'll drown in waxy mess when I've finished.

The problem - despite using the settings that work fine indoors on the same material, out on the car I seem to be getting either zero penetration or blowing massive holes out of the sill material. All of the settings seem to be wrong all of a sudden. I've ended up having to drop the current to stop eating my base material away and I've turned up the gas a little in case the very slight breeze is blowing it away - no luck. I'm laying down high seams which seem to be unwilling to shake hands between sides despite sub 1mm gaps. The best welds seem to be where I do have a large gap and have filled it, developing a nice hot spot, but I can't do that on the thin bits.

Any tips? I'm going to grind it all back and see how bad it is, then try again at the weekend! It seems solid, a good hard punch doesn't shift it, but I don't trust it and it's a mess.

 

[the snooper]

if you have had to turn down the power to stop blowing holes and are now getting high welds (cold) try lowering the wire speed you may have to move slower but should get the penetration back

 

[coyoteboy]

I tried lowering the wire speed but everything got very jerky and sticky and I ended up turning it back up again, it seems to require wire speeds right up at the upper end of the scale for some reason 7-9 / 10.

 

[boydy1989]

I tried lowering the wire speed but everything got very jerky and sticky and I ended up turning it back up again, it seems to require wire speeds right up at the upper end of the scale for some reason 7-9 / 10.

i found a similar problem with my little mig in this situation. I found that turning the speed down a good bit, but also just getting the torch much closer helped.

I am also a bit of a beginner

Oh, and a new tip made a huge difference too.

 

[coyoteboy]

I'll give the suggestions a try over the weekend and post some images if I'm still unable to make anything but bird poo spatters!

 

[gavuk]

Are you trying to run a bead are using the "thin metal technique" described in the tutorial.....?

 

[coyoteboy]

Yeah, I'm trying to use the technique but I'm not having any real success with it as I'm not getting a steady spark, I'm getting a lot of spatter. I got much more acceptable penetration when I started off without any shield gas (by mistake) so I ramped up the gas and found I was spattering again, so I started to increase the power and it improved a little - I got the odd occasional 5-10mm of steady arc but it rapidly dropped back to spatter. In the end I was getting best results from max power - 100A on 0.9mm metal with 0.6mm wire?

Attached is the horrific results. I honestly feel I've taken some massive step backwards, I'd done a heap of test runs and had lovely smooth ones almost as nice as the ones in the demo vids, cut through them and seens a nice even penetration either side and no porosity, but this is how it results on the actual vehicle?!

 

[the snooper]

you say you have put the new plate inside the sill looks like it might be contamination from whatever is on the sill back
do you have the gas flow set to 10 lpm and what gas are you using ?

 

[coyoteboy]

I've no method of measuring gas flow on this rig but I've got the flow set at a rate that works perfectly indoors, set by trial and error.

The back of the sill may have a smidge of rust still, I have tried to clean it up as best I can but I can't get an angle grinder in there as the opening is only 50mm or so wide. It also definitely has some original internal/protective paintwork so you could well be right that it's causing the troubles.

The last set of welds seems to be pretty solid - ive ground them all back to flush and it doesn't seem to have any porosity problems, only the odd gap where it's clearly blown a hole.

Hmmm. Not the neat job I'd been hoping for, but providing it's solid and I can grind it back and fill the remaining volume up to the old sill level it should be fine.

 

[pob125]

ur problems the gas supply

 

[pob125]

you can have too much gas as well as not enough

 

[coyoteboy]

Hmmm I've tried a variety of gas settings and it seems to be fine on virgin metal. I managed some improved welds on the other side of the car which I prepared to almost clinical levels, got some lovely smooth diamondy welds and then it all went a bit spotty again. I'm still working on it but I've managed to get it under enough control to make functional well penatrated welds instead of bird poo!

Time I got a flow meter.