Weld grows as it cools?

[rkde]

Hi,

When I am welding on thin sheet CR4 grade, I noticed yesterday that when I finish the weld and let go of the trigger sometimes a small leg appears from the weld and grows out by about 4mm. What is happening here?

I am using argon/co2 mix and I think its only happened on this new bottle and only a couple of times.

What's going on? never seen that before.

Cheers

 

[malcolm]

The shielding gas stops flowing when you lift off the trigger. The weld is still very hot and will oxidise without shielding gas - that's what the leg growing out will be.

To avoid that keep the torch in position over the weld when you stop - don't whip it away. Don't know how changing gas bottles would make a difference unless you have the new one set to a lower flow rate.

 

[Sparkey]

Yes, that's why with some mig welders you can set pre gas and post gas.
In your case you would be using the setting post gas (if this is possible with your kit?)
Other than that the flow rate should be around 10 lpm, and don't keep your torch too far from your work!
Any info on the kit you are using, flow rate, are you welding outside etc?

 

[rkde]

Cheers
for the help, I am using a clarke 151turbo. Thanks for the help. The can of gas has been playing up. No gas flows till the regulator is at max... With the gas set on top it is about where I normally weld be there is no more adjustment for any more gas

I was using less gas but the problem wasn't happening all the time and I could still lay good welds. Then I realised the problem. The rotating fan was on and it was just a chance that when I was doing some spot welds the fan was passing me.

Feel a bit stupid as I was getting quite annoyed with it oh well.

Thanks for the help. Because of the excellent advice on here I have been able to learn loads and brush up on my welding. Only been migging for 6 months but stick welding for over 10 years, I love the mig makes things so much easier, just wish I had changed a long time ago