# Porosity With Tig On Mild Steel.



## savarin

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?


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## FOMOGO

Any kind of coating on the tubing? Are you purging the tube with gas? Mike


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## zmotorsports

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.


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## Rootpass

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.


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## Ulma Doctor

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.


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## savarin

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.


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## Uglydog

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


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## savarin

Mainly I dip as in this session but I have used autogenous on thin raised sections but I never knew it was called that


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## jayville

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


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## Uglydog

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


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## savarin

Hi Daryl, its a long point as I'm fairly sure that was what I was taught over 40 years ago but looking at the vids on line it seems that such is not the case today


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## Uglydog

I usually try to grind a taper approximately 2.5 x the diameter.
Very approximate....

Jayvilles point about filler rod is valid, if you aren't using good fillers.
Old coat hangers may work ok for OA. But, TIG needs good stuff.

Check your travel angle....

Daryl
MN


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## DSaul

TIG likes clean bright metal.  If you don't sand off any scale or coatings, you're just mixing contaminants into your puddle.


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## Rootpass

The comment about using stainless steel filler wire is a good one. I should have mentioned that. That is a boilermakers trick. Stainless steel filler rod will eliminate porosity due to surface prep and contaminates but not gas issues!


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## savarin

Can stainless mig wire be used? I have never considered usinh stainless filler with mild steel. How does it affect the weld strength?
Heaps of good info thanks


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## zmotorsports

I think your culprit is the mill scale.  TIG welding does not play well with the scale.

You could try some 309 or even some 308 S/S wire but plain ole ER70S-2 should work fine as long as the metal is bare and clean.  I am not a fan of using S/S wire to mask an underlying issue, I use it where the weld or specs call for it.

Mike.


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## savarin

I'm convinced its the mill scale but another string to the bow is always worthwhile


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## Rootpass

Yes you can use MIG wire but it's probably .035? I think you will find that with filler wire of that diameter you will have issues of it wanting to burn back and ball up before you get it in the weld pool. But it is a very good option for small detailed welds on thin small things if that makes sense. Tungsten condition will be more important. Sharp point and frequent touch ups if the end gets dirty from contact with the weld pool. Also you may find a smaller more focused arc with 3/32" tungsten vs 1/8" but really shouldn't make much difference.
For sharpening tungsten it's hard to beat a drill and grinding wheel. Often it's done in the field on a hand held 4 1/2" grinder although there is usually a bench grinder out side the tool room. At home I have cut and removed a portion of the bench grinder guard on the back so I can grind with the rotation of the wheel vs on the front where the wheel first contacts the tip. Seems to give a better finish and tip.
While Mike talks about masking an underlying issue that's true. But when I need to make a tool to shut the city water off in the front yard I'm not going to clean everything down to bright shiny metal. I'm not welding pipe at the Savannah River nuclear site anymore. I'll use ss 308 or 316 filler.
Most codes allow filler metal of a higher grade than the base metal to be used. Is there a difference between ER70 and 316l? Sure. Does it matter? I'm going out on a limb and say probably not. I've had this conversation with weld inspectors and engineers several times trying to find out for my own benefit. But match the filler to your base metal and use the ss on carbon tip if you need to! Just as important for frustration welding is to match your wire size to what you are doing. 3/32" is probably more useful to us than 1/8" is due to the fact that our stuff is thin and small. Lol


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## Rootpass




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## Rootpass

I don't want to give the impression that I half a$$ things. When I built my gantry crane in the garage I followed every industry standard that applied for the work I was doing. Full penetration, open root, X-ray quality(or better) welds. I keep a rod oven plugged in with 7018 rods etc. it's been on for 8 years. Hate to think what that has cost.


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## Franko

It is a good idea to purge the air from the hoses. If my rig has been unused for a while, I have gotten porosity in the first inch or so of a bead. It is a good idea to push the pedal a couple of times to purge air from the lines before striking an arc.


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## Fitter Bill

Possibly a "lower" grade of steel. Many years ago a friend wanted to fabricate a 40 gallon gasoline storage tank, he purchased the metal ( 14 ga) and I got the job of TIG welding the seams.... Holy piece of crap, whats happening? Went to work next day, talked to Jim ( the most knowledgeable welder around and my mentor) first words out of his mouth were rimmed or killed steel. I ended up stick welding ( 6010 & 7018) the seams.... Google "Rimmed or Killed Steel" wealth of information there. Hope this helps.

Bill


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## TOOLMASTER

I weld all my steel with stainless rod...(tig)


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## Uglydog

Mill scale.
Next time you get to the steel yard ask to see a piece of Hot Rolled (HR) and a piece of Cold Rolled (CR). The HR has scales like a fish, while the CR is relatively shiny. 
HR is rolled to its final size while hot enough to scale (over about 1700 degrees F). CR is rolled to size below scaling temperatures.
HR also seems to be oily. I don't know that it is. 

Daryl 
MN


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## jayville

most of my tig welding is done with 2.4 mm tungsten and .6 mm,.9mm and 1.2 mm 316 mig wire,it is not very often the I have to use  1mm tungsten but I do when material is like paper thin...and like wise with wire..rarely do I use 1.6 mm wire or heavier unless the material is over about 5 mm...the thinner wire is a lot easier to use on thinner material...I do not have any golden rule on how I sharpen my tungsten other than to hold it vertical when sharpening against wheel..this keeps impurities to a minimum from grinding wheel..the point of the tungsten tapers back about 6mm...I have worked in stainless industry for many years and these are the basic guide lines that I have always stuck by...clem


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## savarin

found this http://www.weldingtipsandtricks.com/tig-welding-tips.html pretty good stuff


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## savarin

I'm sold, stainless rods on mild steel from now on.
The welder, three in one chinese welder





The rods




The welds
1, mild steel on cleaned metal
2, mild steel on uncleaned metal
3, no filler just fusion on cleaned
4, stainless on cleaned



5, stainless high amps on uncleaned
6, mild steel low amps on uncleaned 
7, mild steel high amps on uncleaned
8, stainless edge bead on cleaned
This should be flipped as 5,6,7 were welded right to left
All welds were pos earth


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## TOOLMASTER

are you sure you are getting gas out?   should look way better than that


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## Tony Wells

What do you get with no filler? Just run a puddle across that sample. Metal cleaned.


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## TOOLMASTER

over cooking maybe?


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## TOOLMASTER

wrong gas from supplier is not unheard of


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## savarin

The gas is the first time I have used a disposable  cylinder of pure argon. I do so little tig that the phenomenal cost of a hire cylinder it out the question.
In all the welding I have done to date I have never seen this problem as bad.
A touch of porosity maybe at the start when the line was empty but no more.
I will try one last go with the gas cranked way up and the amps down as low as possible and still arc.
Still if needed I can now fall back onto stainless wire.


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## TOOLMASTER

WAS  it veeeery humid?


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## savarin

this is our dry season so humidity was down in the mid 50's very nice.


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## DSaul

Something is very wrong there.  That must be the wrong gas or you're just not getting good shielding.  Is there a breeze or fan blowing that could be blowing the shielding gas away?  Are there sparks when you're welding?(there should never be sparks) What cup size and flow rate are you using?  How much tungsten stick out?  Is your tungsten contaminated?(does it look black and sooty?)



This is mild steel with a 3/32" 2% lanthanated tungsten, #8 cup with about 15cfh argon using er70s2 filler and I'm just a hack garage welder.


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## TOOLMASTER

YUP..THATS WHAT IT SHOULD LOOK LIKE.....

TUNGSTEN TO FAR OUT? MAYBE


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## Franko

The people at Miller told me that too much gas flow can be as bad as not enough.

I've never experienced porous welds like that that weren't caused by a lack of shielding gas.

I had a similar experience with my MIG. It turned out that I didn't have the hose pushed in correctly. You might check to see that your hose connection is correctly seated.


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## DHJ

As Franco says check connections and check hose from solinoid to torch, a small burn hole in the hose can sometimes pull o2 into the line. Sure looks like a gas problem to me.


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## TOOLMASTER

LEAK IN TOP CAP? ORING MISSING?


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## TOOLMASTER

are you welding ac or dc..straight or reversed?


you may be set up for the wrong weld type..


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## TOOLMASTER

more than likely your issue is polarity


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## savarin

I believe my polarity is positive earth, dont know if its ac or dc.
watching the videos right now


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## xman_charl

correct polarity



tig welder



a few welds









Charl


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## TOOLMASTER

THATS BETTER....DID you check the internal polarity


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## savarin

Charl, thats for mig isnt it?
Just a note, I tried swapping the external earth lead over and the tig wont strike.
If the internal leads are swapped over as in the above video which was to allow gas less mig wont that screw up the tig weld?
How would I check the internal polarity? meter? exactly what kind?
The more I think the more I'm convinced its a gas problem.
I had a cig mig welder that had swarf inside the gas tap on the gun that prevented it from correctly working, once that was removed it was fine.
Even the replacement tap had the same problem.
When I get the time I will explore the total gas path and report back but am unsure exactly when. (too many irons in the fire)


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## Ironken

zmotorsports said:


> I think your culprit is the mill scale.  TIG welding does not play well with the scale.
> 
> You could try some 309 or even some 308 S/S wire but plain ole ER70S-2 should work fine as long as the metal is bare and clean.  I am not a fan of using S/S wire to mask an underlying issue, I use it where the weld or specs call for it.
> 
> Mike.



Very well said. Unless I'm joining SS to CS the 309 stays put away. I guess there are some instances where you have to use SS but, that's the hail mary. I would rather know why the problems are arising.


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## savarin

It isnt the mill scale, it happens whether there is scale or not.
I still have to check out the total gas path for leaks or whatever.


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## dlane

Sounds like air in there, are u in wind ,fan ,drafts = not good, Stinger gas flow should put out lighter 
2" away with Ar .  That's what's I do ,


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## Subwayrocket

That's what it looks like when you've got galvanized or some kind of zinc coating. Even when you think you've ground it all off, there's still some impregnated down into the grain below shiny bright metal.  Was there a garlic kind of odor with the weld ? And if there is any coating on the back side, it will wick thru even if you think you're not getting full penetration. That porosity looks like what you get when you dip the tungsten in aluminum !  Did you ever figure out the cause ?


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## savarin

No not yet, too many other demands upon my time to strip the welder.
I will report back when I find out what it is.
This welder used to be very good for tig which is why I'm flummoxed at present.


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## Subwayrocket

savarin said:


> No not yet, too many other demands upon my time to strip the welder.
> I will report back when I find out what it is.
> This welder used to be very good for tig which is why I'm flummoxed at present.


Go get a piece of known metal , say a piece of 304 stainless ...or grind off a piece of known mild steel ...see how the identical setup works. Go back and look at that thin wall tubing and tabs you had probs with. Upload some pics of the thin wall tubing and tabs just as they are , prior to sanding/grinding ...if it's zinc coated or Galv , it will weld like hell . It's like striking your tungsten on a match. It flares up, stinks and has porosity . Another good idea is to post the question on weldingtipsandtricks  , that forum has a lot of very helpful members .


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