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Welding Cast Iron Beams (maybe)?

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Welding Cast Iron Beams (maybe)?

Postby nam2000 » Mon Jul 31, 2017 1:40 pm

Hi,

I recently acquired a couple of steel I-beams. They're old and rusty. I want to use them to build the underframe for a larger desk. The plan requires me to cut two sides of each beam and build a bracket-like shape by welding it, angled, to a smaller sections the beam on each side.

It didn't occur to me until I got the beams home, that the beams might not be made of usual carbon steel. I had to cut it once for transport and did notice the sparks. They are pretty reddish and a lot less than I expected. Also the surface of the beams is 'dimpled' like on a golf ball. I'd grind down the rust a little and below is a dark brownish/blackish surface.

Aren't construction beams made of cast iron today a rarity? Am I missing something? Is this cast iron? I have a "spark test" video, don't know how to upload, .mov + .mp4 not allowed.

If they're actually cast iron, is it reasonable to TIG weld them with 309L?

Thanks!
Nils
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Re: Welding Cast Iron Beams (maybe)?

Postby Poland308 » Mon Jul 31, 2017 7:15 pm

Take a hammer to the very corner of the beam. If it's cast it will break off a small piece. If it's steel then it will mushroom.
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Re: Welding Cast Iron Beams (maybe)?

Postby weldin mike 27 » Tue Aug 01, 2017 6:17 am

Also tig a tiny puddle on the corner. Let it cool and then try to file it, If it is cast iron it'll be as hard as a coffin nail. This is a trick from one of Jody's videos.
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Re: Welding Cast Iron Beams (maybe)?

Postby Poland308 » Tue Aug 01, 2017 6:59 am

weldin mike 27 wrote:Also tig a tiny puddle on the corner. Let it cool and then try to file it, If it is cast iron it'll be as hard as a coffin nail. This is a trick from one of Jody's videos.


This does work really well.
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Re: Welding Cast Iron Beams (maybe)?

Postby nam2000 » Tue Aug 01, 2017 7:59 am

I'll try the hammer and the Tig-Corner test on the weekend, thanks for the input.

Here's a side by side comparison of the spark test btw. On top the I-beam, below a piece of mild steel.
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Re: Welding Cast Iron Beams (maybe)?

Postby weldin mike 27 » Wed Aug 02, 2017 4:04 am

My pleasure. You could design the desk to be collapsible (unboltable) with some cool looking brackets and it wouldn't matter what they were made out of.
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Re: Welding Cast Iron Beams (maybe)?

Postby nam2000 » Wed Aug 02, 2017 5:39 am

Ok, couldn't wait. I tried tigging the corner to see if that hardened it. Well, not sure what happened, but I seemed to be able to hand-file it down pretty easily. Made me optimistic...

...however: I called out the other corner with a 500g hammer. Below you see what happened. That crack means that's undoubtedly cast iron, isn't it?
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Tig'ed the corner + hand-filed it
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Re: Welding Cast Iron Beams (maybe)?

Postby Coldman » Wed Aug 02, 2017 4:47 pm

Look in the crack, it's old meaning you didn't do it. What you have is an old very rusty abused and @&itty piece of mild steel.


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Re: Welding Cast Iron Beams (maybe)?

Postby Poland308 » Wed Aug 02, 2017 7:38 pm

Pretty sure Cold called. That much rust inside means a real old crack. Plus being able to file it after arcing up on it says steel. I'd be real wary of using that beam for any thing other than practice welding. I imagine after you grind it clean you will find lots of micro cracking or stress cracks.
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Re: Welding Cast Iron Beams (maybe)?

Postby homeboy » Wed Aug 02, 2017 8:53 pm

Search - http://www.scrapmetaljunkie.com spark test - and they have some clear pictures of several spark tests on various metals plus other info. From the look of their pictures compared to yours the closest would be tool steel! Would that be possible in an I beam? If so could it be for a special purpose? I had 2 beams that I got many years ago from an old, small backroad bridge that was dismantled that had a similar profile. :?
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