Molten ball on wire?

[Punx0r]

I have a Monomig/Telmig using pure CO2 and 0.8mm mild wire.

Welding 2mm mild to 8mm mild on the highest power setting (~130A) I've noticed a few times a ball of molten steel forms on the end of the wire whilst the arc is active instead of going into the weld pool. I've seen them grow to approx 4mm in diameter before dropping off and sticking to the 8mm plate (has to be ground off). What on earth is causing this?

Possibly related problem, same situation as above: 2mm to 8mm, but at a right angle. Sometimes a weld pool forms directly below the tip on the 8mm instead of where the wire is pointing! I've found this occurs less if I avoid resting the shroud on the workpiece.

It seems to occur less since I cut back the shroud level with the tip to reduce stick out. Before that sometimes the shroud would end up stuck to the workpiece.

Thinking about it, welding stainless bolt heads to the 8mm mild is particularly bad as the weld pool ending up a few millimetres from where it should be. I have to aim well up the side of the bolt head to get the weld actually where the two parts meet!

Any tips or advice would be most welcome

Anthony

 

[Omniata]

"Live shroud?"

Check the spring and ceramic aren't bridged inside the shroud...

The shroud should never be live and shouldn't arc which it sounds like from what your saying


130A is a little low for 8mm, you could maybe do with upping it if you can and direct the torch more into the 8mm than the 2mm to account for the extra power...

 

[shenion]

Sounds like the wire speed id too low.

 

[backpurge]

Agree with shenion, sounds like you are drifting into globular transfer, turn the volts down or the wire feed speed up a touch

 

[Punx0r]

The shroud isn't live, I think it was just providing an easier path to ground showhow in some circumstances or other.

I haven't got voltage control, just four power settings

Cranking the wire speed up a bit seems to have helped. I also gave the shroud a good clean of spatter (there wasn't much on there anyway). Using a longer stick out seems to make quite a difference. I normally use about 1/4", but going to just under 1/2" seemed to improve things.

Assuming the longer stickout didn't just mean I was holding the gun at a different angle...

I looked on the internet for globular transfer, no idea if that's what's happening: the arc is stable and weld penetration and appearance is good.

I'll keep the wire speed up and see how it goes.

Thanks

 

[shenion]

at 130A you will not be getting into globular transfer especially on CO2. Globular transfer does not leave a ball on the end of the wire anyway.

Just the wire speed is too low. As you get going, the torch heats up and more heat is radiated back from the work. So the wire melts easier. What is a fast enough speed to start becomes too slow.

 

[BillJ]

I haven't got voltage control, just four power settings

You have four voltage settings

 

[Punx0r]

Ok, well I don't want to turn down the power!

shenion, what you'd said makes quite a bit of sense. Especially since I'd sometimes seen the ball grow in since.

I guess it must sometimes get too big and drop off because occasionally I've had a blob of molten hit the floor and send of a shower of sparks as it burns up. Usually just as a stop the arc.

The front panel on the welder claims a max output of 145A. I applied some pessimism to get 130A

 

[backpurge]

Does it look like this

If so it is globular transfer, you will get this condition at 130 amps with too much voltage, it can be quite common with CO2 as the gas does not allow you to achieve spray transfer like you can with argon/CO2 mixtures

As you have described it, rather than get a controlled, consistent stream of droplets being projected across the arc like you get in dip transfer, you are getting a large irregular molten droplet on the end of the wire which falls off into the weldpool

If you could post some pictures that would be great

 

[Punx0r]

The best I could do would be to photograph when I get a blob left near the weld afterwards, but I'm not sure that'd be much help.

I can't photo the ball on the wire whilst welding for practical reasons, but also because it only happens occasionally.

Whether it looks like the photo you posted, not sure? Besides being different colours and the other way up, the ball is centred on the wire, not off to one side (if that makes any odds).

The trouble is I'n relying on memory here... What I can recall is looking over the top of the torch, down the wire and a ball of yellow metal grows on the end of the wire to 3-4mm dia and looks like a miniture version of the Sun... If memory serves, it's not touching the weld pool, the arc goes between the ball and the weld pool.

Half the problem here is that off the top of my head I couldn't really describe very well what happens during a normal weld: Things are dark, then the ar starts and things are brighter and I can just about make out the line I'm supposed to follow. I move the bright spot along fast enough to stop it going too bright (which I've learnt precedes burning a hole).

My apologies if I'm leading you guys up the garden path with vague descriptions - I had imagined it'd be some easily recognisable rookie mistake or other.

I appreciate the input though

 

[Sparkey]

I move the bright spot along fast enough to stop it going too bright (which I've learnt precedes burning a hole).

Hmm, so you're probably right then BP! increasing the travelspeed will put you into globular...

So actually at 130 amps you can get into spray too? It must only depend on voltage then?
Please correct me if i'm wrong...

 

[shenion]

Here is globular transfer:

The balls are not much bigger than the wire. You also will not really see the balls as they move fairly fast and don hang around long. If you are seeing a 4mm ball then it is just too low a wire speed.

Ed Craig's site used to have references to globular/spray on CO2. Spray occurred at 270A. I would assume globular would be at least 200A.

 

[backpurge]

Think there is a difference in terminology between the UK and the States

 

[Drains]

Backpurge, a machine with four voltage settings is unlikely to be getting anywhere near globular transfer - short circuit only - probably a maximum of 21 volts at full whack. It's only a hobby set after all.
Perhaps you could get that with 130A, but surely not with that voltage? The issue certainly looks to me like wire speed is too low. It's a classic error for a learner, as is high wire speed. Whereas getting globular transfer out of a 130A set would try the skills of Thomas Edison.

 

[tombardier]

I have had the same problem since getting new gas. My kit and settings:
Sealey supermig 140
Coogar 5 gas (93% argon, 5% co2, 2% oxygen)
0.6mm wire (clarke)
Setting voltage to tops (max/2) and speed to very high (8-9)
Laying beads horizontally on to 2mm plate.

It's not that I have a problem as such, I'm just listing the conditions which cause me to have these globes build up, sometimes to almost 10mm! Interesting that people on the thread think it's due to slow wire speed 'cause mine couldn't be any faster! It does seem to be working very nicely until one of these balls start to form though

 

[xboxjoner]

I have had the same problem since getting new gas. My kit and settings:
Sealey supermig 140
Coogar 5 gas (93% argon, 5% co2, 2% oxygen)
0.6mm wire (clarke)
Setting voltage to tops (max/2) and speed to very high (8-9)
Laying beads horizontally on to 2mm plate.

It's not that I have a problem as such, I'm just listing the conditions which cause me to have these globes build up, sometimes to almost 10mm! Interesting that people on the thread think it's due to slow wire speed 'cause mine couldn't be any faster! It does seem to be working very nicely until one of these balls start to form though

If your wire speed is flat out should you not be using 0.8 wire? This will let you slow the feed rate down, a mate has a sealey 180 and 0.6 is no good as the wire feed is flat out on only low power settings, this was cured by using 0.8 wire

 

[millermatic]

i was having the same problem a few months back and i found out its just a matter of holding youre mig gun at a certain angle and haveing an appropiate stick out or you may just have the wrong tip in the end of the mig gun

 

[Punx0r]

I cranked up the wire speed a touch and learnt to move the gun faster. I no longer have this problem