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I heated a piece of rebar way past cherry red on a whim
So I was messing around in the shop yesterday, just trying to use up some scrap. I grabbed a piece of old concrete rebar, the kind with the ridges, and stuck it in the forge. I got it way hotter than I normally would, past a bright cherry red, almost into a yellow heat. When I pulled it out and started hammering, it felt weirdly soft and moved like clay, but then it started to crumble at the edges instead of drawing out clean. I cooled it and it was super brittle, like chalk. I think I burned the carbon right out of it by getting it too hot. It was a total waste of time, but it showed me how easy it is to ruin steel if you're not paying close attention to your temps. Has anyone else accidentally burned a piece of steel and learned a hard lesson about heat control?
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quinnm775mo ago
Yeah, that's decarburization, not burning. Burning is when you get sparks and it literally starts to eat itself. You just cooked the carbon out of the surface layer by holding it way too hot in an oxidizing fire. The core might still be okay steel, but you'd have to grind off a lot of that chalky outer shell to find out. It's a good lesson on how much heat matters, and for how long.
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matthewwilson5mo ago
Exactly, that chalky layer is basically dead metal now. You see this a lot with beginners leaving steel in the forge while they fix a clamp or something. The real trick is learning to read the fire's color and how the steel looks when it's ready, not just going by time. A reducing atmosphere helps, but if you don't have control, you're just baking the good stuff right out of it. Grinding will tell, but it's a tough way to learn how thin your margins for error really are.
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