Porosity With Tig On Mild Steel.

savarin

savarin

Active User
H-M Supporter Gold Member
Joined
Aug 22, 2012
Messages
4,106
I had a small job to do the other day welding some thin brackets to thin tube.
I used argon and a thoriated tungsten.
I could not stop the porosity, it looked like foamed metal.
I played with the amps, up and down, gas,from very low to very high and nozzle diameters all to no avail.
Anyone got any more ideas?
 
Any kind of coating on the tubing? Are you purging the tube with gas? Mike
 
Is the porosity on the side your welding or on the backside? I used to get it on the backside of small tabs and brackets when I was building drag chassis until I started back-purging. That corrected the porosity or sugary looking back side. Recently I fabricated some small argon backer boxes or purge boxes for this very purpose.

If the porosity is on the front side where you are welding the only things I can think of are the cleanliness of the metal or breeze blowing your shielding gas away. After getting the scale off of the metal (I usually used 4130 chromoly for the chassis) I would wipe them down with acetone prior to welding. I also made sure to not weld with a breeze blowing or close the shop door to avoid the argon being disturbed.

Mike.
 
He could be using the wrong gas. You need 100% argon not a mix like you would use for MIG.
Porosity could be coming from the backside of what you are welding. Just make sure both sides of something thin are free of rush, mill scale, moisture,oil , paint etc.
 
joining dissimilar metals can be tricky, especially if you are joining unknown alloys.
12L14 doesn't weld well at all, trace lead makes for poor welding characteristics.
as others mentioned, a tube full of atmosphere is not conducive to a good weld.
sometimes increased post gas flow time will help too, if your problem exists after the purge solution.
filler rod contamination will wreck a weld too.:bang head:
 
I used pure argon, shop door was closed, these were external welds not penetrating into the tubing, filler rods are tig copper coated.
Angle iron was hot rolled but I hadnt sanded back to bare metal, the tubes came from a trampoline and I cant remember if that had been sanded back.
As the porosity started as soon as a pool formed I must assume that scale was the culprit.
I've never noticed this before, literally as soon as the arc melted a small spot it blew up into a bubble. It looked like aero chocolate bar.
I will clean some angle iron and have another go and see what happens.
Thanks.
 
Consider a more vertical position for your travel angle.
If she gets to hot, preheating with a shallow angle she'll start to boil.
Also, make sure that the steel is clean.
Even new hot rolled will TIG differently than cold rolled on account of the oils.
Also, are you dipping or lay or autogenous?
Dipping will cool the puddles and cover porisoity better.

Well at least this is my experience....


Daryl
MN
 
Mainly I dip as in this session but I have used autogenous on thin raised sections but I never knew it was called that
 
try a better quality filler rod ..I have found that if I do a single run all is ok ,if I try to do a multiple pass I can get porosity...I work mostly in stainless but on the occasion that I want to tig mild steel I usually use a chrome moly or a stainless filler wire...stainless wire works very well....clem
 
How is the grind on your tungsten? To shallow of an angle might not focus the arc which means increased time / heat leading to porosity.

Daryl
MN


Sent from my iPhone using Tapatalk
 
You must log in or register to reply here.
Back
Top