Steel disintegrated at welding heat...WHY?!

[Polymarkos, Again]

Using my coal forge, I wanted to weld an eye from a spring steel clip used on railroads. I brought the material to a good orange heat, beat out one end, scarfed that end, and then bent it back to form a loop. I then fluxed it with straight borax, buried it in the coal fire, and brought it up to a yellow-white heat. When I took it to the anvil, one tap sent the entire unwelded eye to the floor. It literally fell apart from a tap. The steel showed some cracking, which was not there when I shaped it.

I tried another piece of spring steel, this from an automobile leaf spring. I drew out the end, scarfed it, folded it around in a loop, and then fluxed with straight borax. I buried it in the fire and brought it up to a yellow white heat. It looked like a good temp to weld. I took it to the anvil as quickly as I could. Before I even tapped it with my hammer, it fell into two pieces. It just disintegrated.

 

Does anyone have any idea what I did wrong? Too much heat? Borax eating steel? Bad ju-ju?

[JHCC]

Could be a number of things. The first one that springs to mind (see what I did there?) is that if you're working with recycled material, there may be microscopic stress cracks that aren't visible to the eye, but that lead to catastrophic failure at welding heats. 

[Polymarkos, Again]

It might be that tiny cracks were the case with the leaf spring, but I don't think that was the case with the clip. But to have two completely unrelated pieces of steel behave the same way? I think more likely it's something in my process.

[Steve Sells]

sounds like too much heat

[Latticino]

Sounds like burnt steel to me.  Too much heat, as Steve noted, but also possibly too deep in your coal fire.  You may have been in the oxidation zone, too close to the tuyer/air inlet. 

For forge welding in coal, what I've found works is a relatively tall igloo shaped fire, with an opening in the side to take the stock in and out.  The hot coals radiate heat all around the stock, and you keep it above the oxidation zone. 

One trick I was taught is to bring the stock up to that high yellow welding heat (remember that high carbon welds at temperatures below that of mild steel, no need for yellow/white heat, and if you are sparking you are too hot) then shut off the air for a count of ten before pulling the stock out of the fire and moving quickly to the anvil for a light tap together.  The soaking seem to help equalize the heat a bit... well it worked for me anyway.

Also, if your leaf spring is 5160, it is famously difficult to weld to itself.  The trick there is to have a sacrificial layer of some other steel in between the two layers of 5160.

[Polymarkos, Again]

Don't know the composition of either piece of steel. Might be just the wrong type.

Neither piece sparked seriously when taken from the fire, but I did flux the xxxx out of it.

Shaped the coal mound like a tall cone, was in about a third the way from the top.

 

Thanks for the input. Likely it was too much heat. But the clip did start severely cracking at lower heats after the first attempt at welding. It was just falling apart. It amazed the xxxx outta me.

[Frosty]

Sean: Rail clips are manganese steel and will NOT take a lot of time above critical, crumbling is a heat/time issue. Too HOT or too long above critical. Once it starts to exceed the limits it's not a home shop matter to anneal; ramping ovens, etc. Do all your forging and weld prep in the high orange max. If the joint is good and clean, and matched, lightly fluxed and it'll weld at low yellow with firm taps from a heavy hammer. Do NOT hit it hard you want as close to a dead blow as possible. Rail clips tend to bounce and shear welds, it's another of their charms. A thick layer of flux is like grease in a bearing it can cause it to shear sideways. 

Frosty The Lucky.

[ThomasPowers]

Once a piece of steel is burnt/overheated the best thing to do is to throw it away---not on the scrap pile but on the "sell back to the scrapyard" pile. If it's part of a larger piece cut well back of the burnt zone.  Far better to waste a bit of good steel than waste all the time you put into a project only to have it fail because you tried to save a bit of bad steel.

[JHCC]

30 minutes ago, ThomasPowers said:

Once a piece of steel is burnt/overheated the best thing to do is to throw it away---not on the scrap pile but on the "sell back to the scrapyard" pile. If it's part of a larger piece cut well back of the burnt zone.  Far better to waste a bit of good steel than waste all the time you put into a project only to have it fail because you tried to save a bit of bad steel.

This is very true. I've learned this the hard way from tongs that I let burn and tried to salvage, only to have them bend or break while I was using them to hold onto something hot.