Intermittent air bubbles

[brnomauser]

I'm hoping someone can make some suggestions for me. I'm getting air bubbles appearing in some of my welds. It's a MIG welder, I think 200A. Using straight CO2, clean wire. When I'm getting bubbles, it spatters and spits quite a lot and when I stop a little mountain grows out of the weld pool as it cools. When ground back it's very porous.

The thing is there is no pattern. I've searched and this seems to be a common problem when there is a lack of gas, contamination etc.. With me, it'll be fine one pass/side length, then on exactly the same piece of work it'll play up a lot. It doesn't matter if it's squeaky clean (verging on sterile), a bit dirty. Turning the gas up or down doesn't change it. The shroud is clean inside, there is nothing obstructing the flow. It seems completely random, some days it won't do it at all, other days I give up and use the arc or oxy.

Can anyone think of what might be causing this?

 

[shenion]

Could be air drafts blowing shielding away.
Too low a torch angle can cause it too.
Too far torch/work distance.
Cheap chinese wire could be it too.

 

[normspanners]

are you welding outside / drafty conditions?sounds more like lack of gas, is it possible that the thin pipe inside your lance is getting kinked in certain positions blocking the flow or the pipe has a split so the the majority of the gas is coming out of the nozzle /shroud but when moved the split allows the gas to go into the sheathing of the lance and actually comes out by the wire feed! ??

 

[Wendelspanswick]

Get a flow gauge on the end of the torch, disconnect the wire feed, pull the trigger and move the lead of the torch about while watching the flow gauge. Also some cheap regs play up when the pressure in the bottle is low.

 

[SiPMerlin150]

Check and be sure there is no spatter blocking the holes of the gas jets, or on the end of the contact tip or shroud. Make sure the shroud is a snug fit (not wobbly or loose) otherwise, air will be drawn into the gas stream creating the problems you describe.

 

[brnomauser]

Thanks guys. Welder is a Cigweld Transmic S3-C. Gas bottle is half full, CIG reg. I guess a damaged gas sleeve is possible, I'll think about that. I'm welding indoors - well a 3 walled workshop. Pretty sure it's not draft related. The flow meter sounds a good idea though, but what sort of meter?

It's good quality wire

 

[Bede]

Every possible problem has been covered already. It's definitely a gas flow issue so check everything mentioned. It might also be worth replacing the spring liner in your torch and blowing the dust through with an airline while you're at it.

 

[arceyered]

If possible Try another bottle the gas may be contaminated ?