Welding Tips and Tricks

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

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.

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.

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.

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.

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.

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?

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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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.

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.

Sounds plausible. The beam was said to have been around for a while. But does shitty old mild steel develop orange skin like in my first picture?

Coldman wrote: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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homeboy wrote: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.

I'll try to do a welding test over the weekend. Thanks for that link, the spark test 'poster' is there nice.

I'm still puzzled about the material, thinking about how much it shattered the edges of the brand new cutting disc, when I separated it for transport.

nam2000 wrote:Sounds plausible. The beam was said to have been around for a while. But does shitty old mild steel develop orange skin like in my first picture?

Coldman wrote: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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Yes! Especially if it was a salt based corrosion.

One of the uses we had for these beams was to hang one on the end of the cable of my 60ft crane and with 4 or 5 guys to swing it to use it as a battering ram to bust up concrete walls or whatever else needed to be demolished. I never thought much of it but after a lot of beating over years the beam ends were still pretty much intact. Must have been pretty good stuff certainly better than mild steel I would think.

Whatever it is, I did a little test with ER70 (S6) and looks good, no cracks or porosity. So I'll proceed and be on the watch for old cracks. Thanks everyone for the input!

Poland308 wrote:

nam2000 wrote:Sounds plausible. The beam was said to have been around for a while. But does shitty old mild steel develop orange skin like in my first picture?

Coldman wrote: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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Yes! Especially if it was a salt based corrosion.