Tig Welding Stainless Steel

[AlanRT]

Hello Guys, after my Aluminium episode (Getting quite good at it now and made up my intercooler pipework no problem), I am wanting to make up an exhaust.

After a bit of practice on some scrap tube, it seems my weld is quite porous. It's OK to begin with (When first releasing the heat), but then cools and pops and looks like an Aero.

The welding Rods I am using may not be the correct rods for welding stainless, but with that aside, what am I doing wrong? I'm getting plenty for penetration so current is OK, however I am using the Pure Argon from my Aluminium setup, could that be the problem?

Thanks
Alan

 

[pedrobedro]

The welding Rods I am using may not be the correct rods for welding stainless, but with that aside, what am I doing wrong? I'm getting plenty for penetration so current is OK, however I am using the Pure Argon from my Aluminium setup, could that be the problem?
Thanks
Alan

Pure argon is the gas you need for tig welding stainless, mild or aluminium. Aero weld sounds like you are running too hot. What rods are you using and what grade is your stainless ?

 

[AlanRT]

it's 1.6mm 304L Stainless Steel, I was using approx 45 amps. I think the rods were stainless, but not sure, not magnetic so presumed they were stainless but could be Inconel (Old rods from my grandads old supply 30+years old), so going to buy some new stainless rods and give it a go.

Didn't think that would be too hot although the welds did look like they were bubbling a bit?

Just watched a couple of videos where they were purging the tube, but this was basically on a flat surface

 

[Wendelspanswick]

it's 1.6mm 304L Stainless Steel, I was using approx 45 amps. I think the rods were stainless, but not sure, not magnetic so presumed they were stainless but could be Inconel (Old rods from my grandads old supply 30+years old), so going to buy some new stainless rods and give it a go.

Didn't think that would be too hot although the welds did look like they were bubbling a bit?

Just watched a couple of videos where they were purging the tube, but this was basically on a flat surface

Could be the rods were designed for gas welding and so unsuitable for TIG, I know this is true for mild steel rods but unsure on whether it also applies to stainless rods.

 

[wheresmejumper]

Stainless doesnt go porous that easily.either the base metal or filler isnt stainless,or either is severely contaminated

 

[backpurge]

Firstly is your material contaminant free.

I know all machines and set ups are different but 45 amps on 1.6mm material seems a bit high for a beginner. What is your fit up like, a tight fit up on that thickness material should allow you to get a really neat weld without the need to add filler.

Back purging will help enormously, in fact for a weld that you want to be permanent I would suggest it is essential, you say you are getting good penetration, if what you are seeing is a grey sugary looking bead, this is not penetration but oxide formation and the joint will fail

 

[Richard.]

Well you've kinda answered your own question. The filler rod may not be correct.
There is no point trying to weld it unsure of what the filler rod is and then be concerned your results ain't good.
If they are stainless it will be stamped on them. If it's not clear and stamped on the rod then it's probably not the right filler.
308 is the correct filler for 304 ss
45 amps is a little on the hot side for 1.6mm ss which may lead to the dull grey weld. Try 35-38.

 

[Richard.]

Wmj is right porosity with ss is not in the top line of common problems.
Your looking for good fusion, penetration and clean surface finish on both sides. The problems occur with balance. Especially on thin gage, you need the heat to ensure its well fused and through but a touch too much and you'll burn out the alloys and get that dull grey appearance. Don't go crazy looking for the American porn rainbow weld by using a 1nch cup and flooding it with gas, but a gas lens is a good thing with ss for aiding a decent shiny surface finish. A normal size 8 cup is sufficient with 6-8lpm been ideal. If it's to be used outside you'll need to remove the heat tinted areas anyway so it's more important to concentrate on the fact it's a sound weld.

 

[AlanRT]

Cheers guys, I'll get some new Rods today and see what happens. Got a feeling they aren't what I thought they were.

My welds are going to be fillet welds apart from one or two tube welds which I'll purge.

My welder is an R-tech unit, it didn't seem to be creating a pool very well when I tried it on lower amps, however I wasn't flowing much gas then, so may be the reason.

 

[Richard.]

Cheers guys, I'll get some new Rods today and see what happens. Got a feeling they aren't what I thought they were.

My welds are going to be fillet welds apart from one or two tube welds which I'll purge.

My welder is an R-tech unit, it didn't seem to be creating a pool very well when I tried it on lower amps, however I wasn't flowing much gas then, so may be the reason.

If the fillet weld or butt weld or outside corner etc is going on thin SS through through to the other side you'll need to purge it from the back. If your just playing with settings and having a practice then there is no reason to do it.
More gas flow won't help with getting a bigger pool. The opposite infact as flooding with gas tends to narrow everything up more. As BP said different machines different settings. A fillet joint on mine in 1.6 ss would be on the top side of 40amps. A butt joint perhaps 35 and an outside corner maybe 30-35. So it's just about getting a feeling for it.

 

[AlanRT]

Cheers Richard, huge help. Would it be the same (back purging) for thin mild steel?

 

[backpurge]

Alan, a lot of people don't bother to back purge mild steel as you don't get the same oxidation problems as with stainless, however I've found you do get a slightly better penetration bead, strangely enough the best results I've had were when using a argon plus 20%CO2 mix as a purge

 

[AlanRT]

Thanks for that BP. looking forward to getting stuck into some stainless welding this weekend

 

[AlanRT]

Right chaps, need further help with this, I'm still getting porous welds on the surface and not sure why. I thought I may not be cleaning it enough, but I've used a flapper wheel on my grinder to get right down to bare metal on the inside and outside and it's still happening, could this be due to leaving deposits on the metal from the paper grit??

What do you guys use to clean stainless thoroughly?? This is harder than Aluminium welding.

 

[eSCHEn]

Do you have a picture of your prepared steel and resulting weld(s) Alan?

May be helpful to see what you're getting.

Also what parameters are you using for the weld? Amps, rod, gas flow etc.

 

[AlanRT]

I will get some pictures tonight, I'm going to give it another go and use Acetone to give the prep a good clean. Also going to construct a shield around my work area to make sure there are no drafts affecting the gas flow.

I was using 31 Amps, 308L Rods for the 304 Stainless and around 7-8 l/min gas flow, red tip tungsten.

Some of the welds were OK, but some still had pitting, just can't figure out what is inconsistent in my setup.

 

[eSCHEn]

That setup sounds fine mate. Do you have a peashooter to prove the flow at the torch? Just thinking faulty reg or hose.

What's your arc length like? Should be a couple of mm or so.

Acetone's not really needed (but I will happily be corrected there by SWK) as long as it's not covered in crap. Give it a go over with a flap disc or linisher or some scotchbrite.

Make sure your tungsten is super sharp and ground parallel to its length.

Don't get it too hot! It's different to mild and gets grumpy

Have you ran an autogenous bead? Do you still get porosity? If not then that'd point to the filler.

I'm just fresh getting some nice SS beads as mine were awful to begin with. ^^^ those are things I had problems with and thought about pal. Maybe one of them will help Gotta give massive props to my man @Richard. for the SS help - he's been nothing short of a miracle worker!

Defo pictures though - should help a lot.

 

[AlanRT]

Cheers I'll take a look into a few points you've mentioned and will run a bead without filler. Getting it too hot may be a problem as I may not be working quick enough??

 

[eSCHEn]

Cheers I'll take a look into a few points you've mentioned and will run a bead without filler. Getting it too hot may be a problem as I may not be working quick enough??

You shouldn't be getting porosity with just too much heat I believe.

I can say my SS welds looked like poop until I got the above things (apart from the peashooter as I didn't have gas coverage issues) in order.

Edit: that's not to say they're brilliant now, just a lot better than they used to be! :P

 

[mike os]

AC or DC? ( dont know if it would make any difference)

are the cleaning products contaminated with another metal?