Tig Welding a C-Clamp and Identifying Metals

Identifying Metals


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Ever need to weld something that looked kinda like cast iron, but you were not exactly sure?

That’s what I got to thinking about when a friend asked me to weld a C-Clamp.

This C-Clamp had the appearance of a cast part. The finish was kind of rough. I was sure it was not because making a C-Clamp out of cast iron would be a horrible idea.

So how did this clamp get cut?

It was holding a bunch of bar stock together for a stack cut in the bandsaw. Someone got distracted, phone call came in, who knows? …And the C-Clamp almost got cut in half.

So how do you determine if the part to be welded is cast iron?

Well, there are clues. For example, pretty much most exhaust manifolds are cast iron. You can pretty much depend on that.

But there are some things made from cast iron that are not so obvious.

Cast iron is cheap and sometimes even used in applications where it should not be.

I used to work at a place where some motor brackets used to mount large electric motors overhead were made from cast iron. One of those brackets failed and nearly killed someone. Those brackets should have been made from steel.

So once again… is there a quick test to determine if something is cast iron?

Here is one that I use a lot.

I use a tig torch to puddle a very small area in a place where I put a file on it. If it files easily, it’s not cast iron.

I know this because cast iron is loaded with carbon. And carbon is the main determining factor for hardening iron. Anything above 0.3 % carbon and there is potential for hardening.

Cast iron has upwards of 2%.

… not 0.2 as in point 2… but 2 whole percent.

When you puddle cast iron quickly with a tig torch and with no filler rod, all the cool mass around the tiny puddle quench the metal and harden the area like crazy. That is why a high preheat helps for most cast iron jobs. It slows cooling rates and prevents excessive hardening.

Ok now that we have established that the clamp is not hardenable, I am still using 309 ss tig rod to weld it.

I like using 309 rod for quick repairs like this where I sort of know the metal but not exactly.

Both 309 and 312 stainless make good all around maintenance rods for non critical weld repairs where the exact composition of the metal cannot be determined.


( As always, feel free to visit us at our sister site, WeldingTipsAndTricks.com. )


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39 Comments

  1. when would dipping the rod or leaving it in the puddle while tig welding effect the integrity of the weld.in what situation would it be best to do either or? during the c-clamp repair video the welder said he was doing both for the purpose of the video and wouldnt effect the weld in that case either way.but when and how would it,in what circumstance and what material is it best to do eithr or?

  2. in what situation or for what reason is it more appropriate to just dip the filler wire as opposed to just leaving it in the puddle without taking it out while tig welding.in the c-clamp repair video the welder said there were times that u should do either or.for the purpose of the video he did both with no effect in comprimising the integrity of the weld.but when and how would it effect the welds integrity either way.

  3. Thanks for all the tips on aluminum welding which I watched on youtube, just passed my Xrays on 5356 aluminum tig 3g,4g,5g. And I did my test with the help of the tig finger, it really helps keep that finger cool thanks man and you didnt even know you helped me.

  4. Jody, would there be any reason to “slow” cool the clamp after welding. I would think the C clamp would have a little more carbon content then 1018 or 1020 and maybe some carbon precipitation in the heat affected zone could possibly fail under pressure?
    What are your thoughts?

  5. Superb work Jody once again!

    How does 309 filler rod differ from for example 316L exactly in this case? Would 316L create more martensitic phase, or something else?

    I know this is not down ‘n’ dirty way anymore, but sometimes it’s good to understand what’s going on in the metal when welding…

    Greetings from Finland

    • 309 is more for stainless to carbon steel where as 316L is for more stainless to stainless welding atleast it is when I weld in the shipyard.

  6. Hey, guys – if you’re reading this, wondering why your video is only 19 seconds long, just reload your page and the issue should be fixed. So sorry for the whoopsy!!!

    Best,

    Jody

  7. Jody,
    What the heck? I can’t believe you messed up, and only aired 19 seconds of a video. I paid good money to see this video ($0), and you let me down.
    Just kidding obviously, but please do us all a favor and let us know when the complete video is up. I always enjoy your videos, and this one started out great as well. I, and I’m sure many others, would love to see the ending to this one.
    Thanks for all your effort and hard work. Rich.

  8. I think I nodded off again! Hahahaha!

  9. Jody, I thought I nodded off again. Guess I better pay attention. When is the next 19 seconds coming? Thanks! Hahahahaha!

  10. I Like it it was informative

  11. Jody,
    Sometimes you just have to read the text. It is relaxing……
    LOL

    Thanks for all the great stuff you do and I especially enjoyed Bubba!

  12. Can we see the rest by Friday???

  13. Jody, I am a pretty quick study, but 19 seconds, I’ll try to do better.

  14. A bit of an anticlimax but some good advice all the same mate. Thanks.
    Keep them coming mate.
    Cheers.

  15. This was like a prom date that started out looking good but crashed and burned when the juicy stuff began. But we still love your videos.

  16. Well this is a first. I,ve been watching you for a long time and have seen some great work from you ,so well i think we can just forget this little mishap. Thanks for all of the really GGGOOd videos. Mike

  17. Been watching you for along time , this is a first. Oh well, no body,s perfect, but your a darn good welder so i believe we can all just forget this one. Thanks for all of your great videos.

  18. Jody you teasing us only 19 sec????????????

  19. Markus Sundqvist

    December 12, 2012 at 2:10 PM

    Argh this is not happening right now… Waited so long for the newest one, well two days:D
    Problems with uploading or something like that I quess. Looked interesting subject btw:)

  20. Heyyyyyyyyyy I didnt get butter in my popcorn. The show ended too fast. why…….

  21. Hi Jody,

    Only 19 sec Video this week?

  22. terrence chaplin

    December 12, 2012 at 1:48 PM

    why was the video of the week-welding a c-clamp only 19sec. long?

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