Bit of an issue

[Mr Toasty]

As the title suggests, im doing some structural chassis welding on my car at the moment and it seems like im getting tiny holes in my weld pool when i end a weld or when I grind a weld back, i know that this has been covered before but i can't find my answer. It seems to only happen at high amps. to lay bare the situation

Im welding 3mm box section onto the chassis rails to mount the cage off of. i'm using a clarke 151 en turbo with carbon dioxide on the 3 max setting and about 8 on wire speed and it only happens when im doing the oyster curl technique were as with the double back it doen't seem to do it. I have enough gas aswell.

any ideas on this issue would be greatly appreciated.

 

[Tigman]

Have you cleaned the chasis right back to shiny metal ? are you out in a draught, wind can blow the gas away from the weld ! any pictures ?

 

[Mr Toasty]

the metal is absoulotly shiny and im in a sealed room so no wind ill posy some pics this afternoon

 

[Tigman]

got to be gas issue , take a look at your torch take off the shroud and clean inside , check the diffuser is ok , holes clear ! then crank up the gas to make sure you can feel it coming out .

 

[Tigman]

is the chassis full of waxoil , when your welding the oil runs could contaminate the weld ?

 

[gavuk]

Why are you weaving on 3mm?,oyster and double back technique?....sorry are not terms i'm familiar with can you explain?....any photo's?

 

[Mr Toasty]

Why are you weaving on 3mm?,oyster and double back technique?....sorry are not terms i'm familiar with can you explain?....any photo's?

The terms i used i was told by an old boy (75) who taught me how to weld. not to sure of the technical name for it.

It's not a gas issue as the bottle is newish and i hear it when i pull the trigger, yes the chassis is full of waxoyl bit it was only on the second pass which is weird it's still uber strong just wondered what it might be.

 

[Wozzaaah]

What gas flow rate are you using?
Show us some pics of the welds before you grind them back, it'll make it easier to diagnose.

 

[subarc boy]

porosity

that looks like porosity may be caused by to much gas to little gas or the weld pool getting contamination into it
ie paint or grease underseal ???

 

[Lewis Medlock]

'Venturi effect' maybe? not so much quantity of shielding gas but quality.

http://www.lincolnelectric.ca/knowledge/articles/content/gmaw.asp

Porosity problem #2 says....

'A turbulent flow of gas as it exits the gun may also lead to porosity problems. Ideally, the gas will lay over the weld puddle much like a blanket. Turbulent gas flow can be caused by too high a flow, an excessive amount of spatter inside the gun nozzle, or spatter build-up in the gas diffuser.

Other possible causes of insufficient gas flow may be damaged guns, cables, gas lines, hoses or loose gas fittings. These damaged accessories may create what is referred to as a “venturi effect” where air is sucked in through these openings and flow is reduced.'

When you say it only happens at high amps, are you then using a higher flow rate? Is the CO2 freezing the regulator and restricting the flow?

All the best, Jim

 

[Sparkey]

Yes, i would like to see pics of the beads before you grind them back too!

Make sure the shroud is free of spatter, gasflow around 10 lpm (too much gasflow can cause trouble too!) and make nice even stringer beads...no fancy pancy weaving, just a straight line...