Porosity

[wheresmejumper]

doing some 60x5mm ms pipe,and getting terrible porosity.the root looks okay but capping it reveals/pulls out all the holes.so does a grinder.
i checked every hose and connection with leak detector,the regulator,flowmeter,every torch element, and 100% sure theres no leaks.back cap,collet etc.was convinced it was poor gas so brought my bottle back to be replaced.new bottle now but the same problem.i now have a replacement regulator,connected straight into a new scratch start valved torch,new consumables and still no joy.
steel is ground back inside and outside pipe.even cleaned with acetone,something ive never had to do with new stock.

the tungsten does discolour,but being new to scratch and lift start,i wasnt sure if small amounts of deterioration were the norm.but this is a fresh red,2.4 tungsten after about 10 seconds of a run at 75 amps.cant be right



i have tried gas lenses,standard collet bodies,size 5 to 8 cups, and gas from 5 to 10 lpm.

pretty sure it isnt technique either.,i cant see how it would just appear now

i cant really imagine getting two bad bottles of gas


its going on for 10 days of eliminating things one by one.
and then re eliminating things.

wits end

 

[johnny max]

Why are you tigging up 60x5 ms tube
Is it test pieces

 

[rohart]

Are you going straight from the regulator to the valve in the torch ? If so, you'll have to change the torch, in case the valve in the torch is letting air in. If not, do so, and eliminate what's in between.

Are you using filler rod ? If so, do some autonomous work, without filler, and see if that goes better. Back to square one and run some beads on some clean MS plate.

Is there a gap between your lengths of pipe ? Do you need to purge ?

Just some thoughts - good luck.

 

[hotrodder]

If the tungsten has gotten discoloured then it's been exposed to air while 'kin hot. Contamination from a messed up 'scratch start', dunking it into the weldpool etc will mess up the tip but that's it, discolouration (especially away from the tip) is the result of oxidation.

'Bad gas' is extremely unlikely IMO, had leaking cylinders etc but never a cylinder of contaminated argon and don't know anyone that has. Always turns out to be something else unless it's something daft like a bottle of argoshield or stainshield MIG mixes

Might be the pic (or me) and won't effect shielding quality but that tungsten looks to have been ground radially rather than axially?
Weld geometry can mess with shielding enough to draw air in and contaminate everything. Does the same thing happen with a simple weld bead on plate? What about the spot weld test? Bit more complicated with scratch start in that breaking the arc without messing up shielding is a chunk more difficult than it is with post flow control. Thinking about it on the off chance that's the cause of the tungsten discolouration what is the EXACT spec of the filler wire you're using? It is proper TIG wire and not oxyfuel stuff right?

The valve on the torch... did you test that open as it would be while welding? Like the back cap a leak there will draw air in rather than push argon out...

 

[wheresmejumper]

thanks for all the replies
im just practicing root and cap on a bit of pipe,not a job or test piece
2.5 gap,no purge

i have an older wp26 non valved torch that i plugged directly into regulator this morning,and i am getting porosity on just cleaned mild steel flat bar.even without filler,which is er70-2,or -6 cant remember which.it varies in amount,but always there.
that tungsten was done one handed on a flap disc on grinder.lighting might be throwing it off a bit
i suspected gas as it was in one of the first replies i googled.moisture in argon came up,and didnt know if it was related to recent heatwave.but im sure i wouldnt be their only customer having issues if it was at fault.
3 different torches,2 welding plants,2 regulators,4 back caps
i might just be unlucky and all torches,or both regulators,all back caps etc i have are screwed.a friend will try to grab a few bits from work on stuff known to be good,hopefully will be able to isolate problem.

 

[backpurge]

As HR says above when you are TIG welding mild steel, you need to use proper TIG filler wire, you will get porosity if you try to weld it without filler or use gas filler rods

 

[wheresmejumper]

it is pressed/stamped with er70s6
is that tig filler?

 

[justmental]

yes it is tig filler rod

 

[wheresmejumper]

how about these
http://www.walshengineering.com/shop/Welding/Welding+Consumables/TIG+Wire/Mild+Steel/Bohler+2.4mm+Super+Steel+TIG+Wire.html

'particularly for root runs on pipe'

but it also says can be used with oxyfuel?

 

[hotrodder]

You can use TIG wire with oxyfuel but not the other way around*. It's all to do with the flavour of gas that's protecting the weldpool... TIG uses argon which is inert, oxy acetylene and MIG (strictly speaking MAG due to the CO2/O2 mixed with the argon) aren't inert

The result is that TIG is totally reliant on 'deoxidisers' in the filler wire to deal with any scale/oxides/inclusions etc when welding carbon steels. A metallurgist like TechnicAl will point out that strictly speaking er70-s6 (A18) is a MIG/MAG filler wire- it's alloyed to work better with an active gas shield, explained in more depth by the man himself here. It's used all the time with TIG but in my experience it's less tolerant of crud than er70-s2 (A15)... about the only time i use it is when i want/need some wire finer than 1.0mm and nick some 0.6 or 0.8 from a mates MIG. While it usually works fine it's about the only time i've had porosity issues (talking the odd pore, not an aero bar) although that could be as much to do with the size of welds i.e. stupidly thin stuff hence the fine wire and so not adding much filler metal to the weld...

Moisture in the argon/dewpoint shouldn't be an issue and note that (as far as i can work out) most of the 'bad gas' stuff on the internet comes from US welding forums... cylinder regs are different over there and it's far more common to own them and for LWS to refill by decanting. I still think most of the 'bad gas' stuff is user error but if LWS filling procedures are sloppy/the stories about buying an Ar/CO2 cylinder and getting it filled with pure argon are true...

* the deoxidising elements in MIG/TIG wire result in a sluggish, 'pasty' weld pool with oxyfuel when compared to the correct O/A wire which has little to no Si in it and none of the other stuff except for Mn which (as Al says in the link) is there for other reasons

 

[wheresmejumper]

i think ill pick up some er70-s2 tomorrow

i said id practice on carbon pipe to save on material and purge gas instead of stainless

flawless idea

 

[Desilvawelding]

Make sure you grind the tungstens vertically its must anyone who grinds them sideways onto a wheel ain't doing it right. fact. Helps with gas flow prolongs tip life. Also angle of tungsten not too steep not too pointy

 

[ronan]

What i do is if i am getting porosity in a mild steel or carbon steel weld , is to do a test piece using a different rod, maybe stainless and if the porosity disappears then you can assume its the incorrect rod causing the problem. Its amazing how many places try to sell you oxy-acetylene gas welding rods if you ask for rods to tig mild or carbon steel.
Have you tried a gas lens ? And are you keeping the end of the rod in the gas flow after you have dipped it in the weld pool ? If not you could be introducing oxidized or burnt metal into the weld.

 

[Lawnmowerboy]

Make sure you grind the tungstens vertically its must anyone who grinds them sideways onto a wheel ain't doing it right. fact. Helps with gas flow prolongs tip life. Also angle of tungsten not too steep not too pointy

Not just that. The biggest factor it changes it the electron flow through the tungsten and off at the point, Which should be the fine point you've vertically ground on the end

 

[wheresmejumper]

i grind them properly on the belt sander normally.the last two weeks i couldnt be arsed every time,arc stability/quality was the least of my worries.as for doing it on a wheel,its a fairly common method on site
the problem has went from fairly constant to intermittent.stainless rods should,and do make a big difference,but dont completely eradicate the issue.i have tried a few gas lenses too,without luck.im keeping the rods in the shielding gas,and cut off the used end every time i start.new er70-s2 made no difference

 

[Lawnmowerboy]

Are you sure it's not the metal you're using? Leaded steel welds rather badly and does conaminate.

 

[wheresmejumper]

i got the pipe from local supplier,its 'black' steel?
i have tried a few other pieces i had around,grinded clean,with mixed results,some okay,but not perfect.
a friend has had a look,and another is due during the week,hopefully 3 heads will sort it.

in the meantime,to preserve the little sanity i have left,i bought 5 feet of sched10 stainless

 

[hotrodder]

If the tungsten is still discoloured a ways back from the tip like in the pic then you have a shielding gas problem. Granted a lack of post flow can cause it or (as we're talking valved torch and scratch start) snapping the torch away too violently when breaking the arc but given the porosity issues...

Read this thread and post some more pics

 

[ronan]

i got the pipe from local supplier,its 'black' steel?
i have tried a few other pieces i had around,grinded clean,with mixed results,some okay,but not perfect.
a friend has had a look,and another is due during the week,hopefully 3 heads will sort it.

in the meantime,to preserve the little sanity i have left,i bought 5 feet of sched10 stainless

Where did you buy the dairy tube wmj ?

 

[wheresmejumper]

If the tungsten is still discoloured a ways back from the tip like in the pic then you have a shielding gas problem. Granted a lack of post flow can cause it or (as we're talking valved torch and scratch start) snapping the torch away too violently when breaking the arc but given the porosity issues...

Read this thread and post some more pics

i will take some more pics tomorrow.i havent seen the tungsten get anywhere near as bad as pc18 in that thread though.im actually running out or thoriated now from charring,then cutting off contamination and regrinding,to be on the safe side.