TIG welding thin steel - stuck to cast iron table
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  1. #1
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    Jun 2013
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    TIG welding thin steel - stuck to cast iron table

    Hi,

    I've just started playing around with my tig welder now that I have my welding table set up. Last night I butt welded two 1/16” mild steel plates to each other, and was quite pleased with the weld for a first attempt. At least, until I realized that the steel was stuck to the cast iron weld table top.... I had to pull fairly hard with some pliers to get it off, and it pulled some of the cast iron with it leaving a 3" long gouge in the top.

    The weld table top is a 4' x 3' cast iron platen that was originally part of a printing press. Overall thickness is about 3" including the ribs underneath, and the solid portion of the top is 1" thick. It's not pristine by any means, but I'd like to avoid this happening again if possible.

    My understanding was that one of the benefits of a cast iron top is that welds and spatter DON'T stick to it, but clearly this did! Any advice on what I'm doing wrong? Should I spray the entire top with anti-spatter?

    Thanks,

    Lee

    Sent from my SM-N920T using Tapatalk

  2. #2
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    Mar 2014
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    Re: TIG welding thin steel - stuck to cast iron table

    Lee,

    If you're running hot enough that you're melting thru and into the table top anti-spatter isn't going to do any thing to stop that. I think your best course of action at this point is to get an appropriate sized 1/4" (or so) thick piece of either aluminum or copper to put down underneath things when ever you think there's a chance you'll be melting all the way thru. A molten steel puddle won't stick to either of those metals. They'll act like a heat sink for the part also.

  3. #3
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    Jun 2013
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    Re: TIG welding thin steel - stuck to cast iron table

    Sounds good, thanks for the tip. I thought the weld bead wouldn't stick to the cast iron either, but clearly I was wrong!

    Lee

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  4. #4
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    Re: TIG welding thin steel - stuck to cast iron table

    Quote Originally Posted by leeko View Post
    Sounds good, thanks for the tip. I thought the weld bead wouldn't stick to the cast iron either, but clearly I was wrong!

    Lee

    Sent from my SM-N920T using Tapatalk
    Lee,

    Both "Cast Iron" and "Steel" are alloys of Iron and Carbon the only real difference being that Cast Iron just has a lot more Carbon in it than steel does. It's pretty much a given that they'll mix together in the molten state and then re-solidify with the same grain structure. The problem is that all the extra carbon in the Cast Iron makes things brittle. The reason you tore a chunk out of the cast iron was because the shrinkage stresses from the molten nugget re-solidifying caused what's known as "under-bead cracking".

  5. #5
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    Jun 2013
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    Re: TIG welding thin steel - stuck to cast iron table

    Good to know! Thanks

    Now I need to figure out how to repair the gouge... Brazing, maybe? I'll shoot a pic when I get home later

    Lee

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  6. #6
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    Mar 2014
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    Re: TIG welding thin steel - stuck to cast iron table

    The first 5 or 6 pages of this will give you some good general insight into the metallurgy of Cast Irons and Steels.

    https://digicoll.manoa.hawaii.edu/te.../PDF/NBS88.pdf

  7. #7
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    Re: TIG welding thin steel - stuck to cast iron table

    Quote Originally Posted by leeko View Post
    Good to know! Thanks

    Now I need to figure out how to repair the gouge... Brazing, maybe? I'll shoot a pic when I get home later

    Lee

    Sent from my SM-N920T using Tapatalk
    Lee,

    Oh man you might just want to learn to live with and work around that gouge. If you go heating up a small area out in the middle of that cast iron platen to "Bronze Brazing" temperature with out first having the whole thing preheated up to around 900+ F. you'll run the risk of getting some serious cracks in it. At the risk of having my professional welders card revoked....well, there's this thing called JB Weld you might want to consider using.

    But by all means take a picture of the gouge and post it.

  8. #8
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    Jun 2013
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    43

    Re: TIG welding thin steel - stuck to cast iron table

    Hehe fair enough. I could live with JB weld - whatever the repair is, it'll still show. Might as well do it the easy way... It's a welding table, after all...

    Thanks

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  9. #9
    Join Date
    Mar 2005
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    Re: TIG welding thin steel - stuck to cast iron table

    Mig the gouge and hit it with a flap wheel.

    Done.


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  10. #10
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    Nov 2005
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    Re: TIG welding thin steel - stuck to cast iron table

    Grounding issues. Ground to the part. Or clean the ground area on the table to fresh metal then Clamp parts to the table.

    If that is your ground on the corner , then it looks like you are over the paint.

  11. #11
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    Jun 2013
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    Re: TIG welding thin steel - stuck to cast iron table

    Hi Tapwelder,

    No, I'm grounded to the bare underside of the frame, and the table is bolted to the frame. The tab you see on the corner was just a feature of whatever the platen was in it's previous life.

    Grounding seemed just fine while it was welding, though. Can you explain for a TIG newbie what the grounding problem likely is, and how it resulted in the workpiece sticking? Not disagreeing, I just don't understand!

    Thanks!

    Lee

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  12. #12
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    Re: TIG welding thin steel - stuck to cast iron table

    If you have poor ground connection, then there is a possibility of arcing between the table and the part. Arcing can creates fusion of parts to table. And leave pits in the cast.

    Cheap all connections even inside the machine.
    Last edited by tapwelder; 05-08-2018 at 02:37 PM.

  13. #13
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    Jun 2013
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    Re: TIG welding thin steel - stuck to cast iron table

    Ah ok, thanks

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  14. #14
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    Dec 2010
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    Re: TIG welding thin steel - stuck to cast iron table

    Quote Originally Posted by leeko View Post
    need to figure out how to repair the gouge...
    I know you won't like this, but my first suggestion is to get a hand stone and stone the area of the gouge, making sure the table is flat all around the gouge. Then ignore the gouge.

    Or, you can fill the gouge with Devcon (metal filled epoxy) but beware that if you fill that gouge you will have to get the table flat again and that won't be easy.

    metalmagpie

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