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Thread: Porosity when TIG welding laser cut steel plate (pickled and oiled)

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    Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Howdy, fairly newby-ish TIG welder trying to do a simple butt weld to merge two pieces of 1/4" thick HRPO (hot rolled picked and oiled) steel together. Figured I could tack it and run a nice little bead down the middle, but having issues with porosity which seems to kick up as I'm about an inch into it. One of the benefits of HRPO steel is that it doesn't have mill scale, and usually just needs to be hit with some acetone before welding, but I'm wondering if the porosity in this case might be caused by the very, very small amount of "slag" resulting from the laser cut edge? Here's a picture of the edge quality:

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    Experimenting, I took a couple test pieces (with laser cut edges) and wire wheeled and strip-disced them, and attempted a butt weld on those pieces. While it seems like I could run a bit of a longer bead, it still ended up giving me quite a bit of porosity (it didn't bubble up but I could feel it).

    Any suggestions? I'm trying to avoid hitting it with my big grinder or flapdisc since, well, there's no point in paying for the precision of laser cutting if I'm just going to grind the edges down.

    Here's a picture of the piece in question, with some porosity visible (sorry, don't have a macro lens). The hair was from my rag I was using to clean it. And yep, I know I need to step up the amps to get better penetration here.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    That coating on the cut edge is essentially mills scale and needs be removed. The lint of course needs to go too, a stainless brush would be one way to go after it. What is your gas flow, have you confirmed it with a torch tip meter and what cup size are you running?

    Try running a few beads, no filler on the flat face of the work piece to see what things look like.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

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    Steel still has milscale on both the cut side & the top. See where it flaked off?

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    Porosity when TIG welding laser cut steel plate (pickled and oiled)

    You will have to hit it with a fast flapper disc clean.
    Doesn't matter if it's been cut with a laser, plasma or acetylene. On a welding process as finicky as tig, it will need a little touch up with a flapper prior to welding. Those cut lines/marks and dross should be removed, especially if tig is your welding process.
    Stick welding would much more tolerant of this and would be much faster as far as welding.
    Last edited by snoeproe; 04-05-2020 at 10:42 AM.
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Thanks all, for confirming I just need to be a little more aggressive with cleaning the edges.

    sand_man_red, I will run a bead across the face and see how that goes -- good idea. Also, first I've heard of a torch meter. I see one on Amazon but reviews state it's very inaccurate. Any recommendations on supplier?

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Quote Originally Posted by ryanjg117 View Post
    Thanks all, for confirming I just need to be a little more aggressive with cleaning the edges.

    sand_man_red, I will run a bead across the face and see how that goes -- good idea. Also, first I've heard of a torch meter. I see one on Amazon but reviews state it's very inaccurate. Any recommendations on supplier?
    Mine's from Amazon too. It more or less agrees with the flow gage on my regulator. I suppose you could calibrate by displacing water over time but I never had a good reason to go that far.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)


    ryanjg117


    When TIG welding Black Iron [carbon steel] - all of the mill scale - gotta go . . .

    Virgin P&O is still dirty. The oxide on a laser cut edge is akin to the scale on a
    TIG bead - both must be removed when welded - or you get your results.

    Flapping: is a waste of a flapper - and usually just polishes the scale . . .

    I maintain four die grinders: two straight / two 90, equipped respectively with
    wire wheels, and stripping wheels . . .

    https://www.3m.com/3M/en_US/company-...3241120&rt=rud

    This product: will strip paint, powder coat and mill scale - without damaging
    the parent metal. This is important when doing Rustic/Period work . . .

    This site has Forty variants of the composite - I use a .500 x 4.00 / .375 arbor.

    With regard to Chem Cleaning before welding - all alcohol and acetone does -
    is remove fingerprints . . .

    hth -


    Opus

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    First things first - I welded a nice bead right down the middle of the surface of the HRPO steel without cleaning and it went down perfectly. So I know this issue isn't related to argon flow and has to do with the edges.

    The frustrations continue. I flap-disked the mating edges until they were nice and shiny, and this was still my result:

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    What I keep noticing is the start of the weld is fine, and deteriorates until there is a lot of porosity at the end. I'm wondering if it has to do with temperature build-up, or perhaps the fact that there is a slight gap between the pieces and maybe argon can't get into those nooks?

    I wanted to see what it looked like inside, so I grinded away at the top of the weld and pried them apart. Here's what the two mating surfaces looked like:

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    And here's a short video showing the cut-away (warning: turn down volume, I had a podcast running in the background): https://photos.app.goo.gl/MT1WFNrRvvGkoohH9

    Here's my torch - I've noticed the tungsten turns blue pretty quick - I have no idea if this matters?

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    Getting pretty frustrated, I tried again. Cleaned the edges and also cleaned the top and bottom surfaces. Here are the videos of the two mating surfaces once prepped:
    Part 1: https://photos.app.goo.gl/f1Ag7v6S8QEtUWdq7
    Part 2: https://photos.app.goo.gl/Cp7SQ4KiodrScGeJ8

    I welded it with four beads (two on each side). Here's a video of the final result: https://photos.app.goo.gl/6dR85NfLJwHB7r9r6

    While that last weld looks visually better, it didn't sound good when it was going down, and I know there's more porosity than what I can see on the surface.

    Any more ideas? I'm wondering if this is a scenario where I need to backpurge (which I can do, since the much more painful part of this project was welding notched, thin-walled stainless tubing, where everything was backpurged).

    Opus, where do you buy your 3M pads? I'd like to give them a try so long as I don't have to spend $250 on a 10 pack of them. I have been using the Black Hawk strip discs (Amazon) and like using those for removing rust/paint/scale without digging into the base material too much.
    Last edited by ryanjg117; 04-06-2020 at 02:50 AM.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    I question your torch set-up. Are you sure that is the correct insulator for that gas lens and clear cup? have you ever successfully welded with that exact torch and equipment? Torch assembled correctly with no missing parts? Have you welded with a regular ol' standard alumina cup, either with a regular or a gas lens collet body for an alumina cup?
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Quote Originally Posted by Oscar View Post
    I question your torch set-up. Are you sure that is the correct insulator for that gas lens and clear cup? have you ever successfully welded with that exact torch and equipment? Torch assembled correctly with no missing parts? Have you welded with a regular ol' standard alumina cup, either with a regular or a gas lens collet body for an alumina cup?
    I agree. Looks like a gas issue. Assuming the nitrogen/oxide scale has been removed, the issue becomes blatantly apparent an inch into the weld. And without knowing the parameters or equipment type, I would think the initial gas surge on arc start peters out after an inch and leaves insufficient coverage. Just look at the color of the tungsten.

    First thing I personally do is inspect the placement of the gas holes in the torch between the backcap and gas lens. The second thing is confirm the flowmeter output and whether it matches the torch end.
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Thanks shovelon and Oscar. I'll get the Torch flow meter on order from Amazon. I also have a backup torch that I can test, though I want to say I had the same issues when I swapped that in the other day. Which pretty much isolates it to the flowmeter. I'm using a new USA Weld dual argon flowmeter (with the other side shut off), but come to think of it, I've never really looked to see if the ball drops after a few seconds. It could also be faulty. I have a backup argon flowmeter I can swap in for the time being.

    What has me confused though - when I put a bead right down the middle of the piece, no problem. And it was a longer bead than this butt joint. If argon flow was a problem, wouldn't the same porosity issue pop up here?

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    So, I wanted to do one more test - running a long bead on the face with zero surface prep, ER70S2 filler. Wanted to test the gas cut-out hypothesis @shovelon suggested.

    Sure enough, using the same torch and flowmeter, I had no issues (save for a little nub at the end - that's not porosity, I just have to be better about ending my welds).

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    I'm still thinking this might come down to joint configuration? Is there some special considerations with a thick butt weld like this that I need to think about? My fitment isn't perfect so there is going to be a slight channel between these parts along most of the seam. Reading the article 22 possible causes of weld porosity, do you think #17 might play a part here? "If the weld joint is open at the root, it will suck in air from the back side. Unprotected liquid metal can absorb air easily."
    Last edited by ryanjg117; 04-06-2020 at 04:54 PM.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Sure it might be possible, but I doubt your scenario is considered an open-root type of situation. The puddle itself was not traversing the backside of the weld joint like it does in open-root TIG welding. How about grinding away the previous bead on the top-side, and re-attempt the the bead joining those same two plates? If the porosity comes back, then it might be related to it, but I doubt it.
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    I'm not a TIG welder but it looks like your tungsten is out pretty far which could affect gas flow. On that subject what tungsten are you using and what technique are you using that gives such wide spacing between the ripples? The bead looks more like something you'd see on aluminum TIG welds than steel. A bigger gas cup may help and you may be pulling the torch away too soon. and O2 is getting in the weld.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    It's not too bad when you have a gas lens. You get better gas coverage with longer stick-outs. For the wider-spaced ripples, just move the torch further on each movement. That's about it.
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Going out on a limb here... Could it be since there is that small gap in the middle, perhaps the oxygen has nowhere to go and ends up blowing out the weld? Kinda like when you're welding and closing up a cavity and you get blowout? I know I'm grasping for straws here...

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Are you leaving the argon on till it cools or pulling the torch away as soon as you break the arc?

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    I use a Walter "millscale" grinding wheel, it is definitely not made for grinding a weld or a bevel - it works great for it's intended use though.

    https://www.walter.com/products/-/pr...cut-mill-scale

    RideKTM350

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Gents, I'm lucky enough to know a local, retired welder who happened to stop by to see if he could solve my dilemma today. I'm embarrassed to admit the problem was fixed in about three minutes by... get this... turning up the argon.

    So, the earlier part of this project called for welding a bunch of thin wall stainless tubing, and 15 CFH was just fine for that. I forgot that stainless can usually be welded on a lower argon setting, and never brought it back up to 20 CFH to do the mild steel welds.

    D'oh.

    Thanks for all the help.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Well that's it. You're now relegated to use an oxy/acetylene torch.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Quote Originally Posted by Welder Dave View Post
    Well that's it. You're now relegated to use an oxy/acetylene torch.
    Heck yea, someone go over there and confiscate all his stuff. Commandeered in the name of all TIG welder!
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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Oxy/acetylene welding is almost a lost art now. It teaches you more about the puddle and fusion than anything else.

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)


    ryanjg117


    Quote Originally Posted by ryanjg117 View Post
    Opus, where do you buy your 3M pads? I'd like to give them a try
    so long as I don't have to spend $250 on a 10 pack of them.
    My LWS sells .500 x 5"/6" for 13.00$ to 15.00$ - one each.


    Opus

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)

    Quote Originally Posted by OPUS FERRO View Post

    ryanjg117




    My LWS sells .500 x 5"/6" for 13.00$ to 15.00$ - one each.


    Opus
    I was given long ago a no-name Clean&Strip disc, never got to use it. Finally after reading in WW about them, I gave it a try. Amazing! It works just great to remove paint from recycled steel, rust and mill scale. Wanting to stock on some more before I ran out, I checked for 125mm discs and not finding any name brand ones, I bought a pack of 5 out of Aliexpress (China). Cheap!

    As I received them it become clear that they were not going to perform the same. The problem is that the amount of abrassive embebed in the resin that gets smeared on the net-like backing of the disc is about 1/10 of what my original (still no name brand) had. So as soon as I started using it it was strugling to remove paint. Don't even talk about mill scale.

    So it became clear that in this particular case, it seems worth it to pay what 3M asks for his original consumables. The problem is that they don't seem to make 125mm discs for angle grinders... only 115. And I was trying my best to use up my current stock of 115 discs to retire the only one small grinder I have and get another 125mm one... I know I can still use 115mm discs on 125mm grinders... but I just don't like the idea.

    Do you guys know of any other manufacturer that makes their own version of Clean&strip discs that could be worth buying?

    Mikel

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    Re: Porosity when TIG welding laser cut steel plate (pickled and oiled)


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