Sorry to tell you but rebar cools at the same rate as any other steel of the same cross sectional area. Now the alloy may have a more limited temperature range where it's forgeable; but it cools at the same rate.

Yes. This is what I was trying to tell you. If your steel seems to be cooling down too fast, it's because you're not getting it hot enough before you start forging, because you're not very efficient at forging (which could be attributable to tools, technique, or both), or a combination of the two. Different steel -- of the same size -- will not solve the problem.

Heat a piece till you have a sparkler. The end probably is ruined from burning, but that is OK, we are learning, cut off the burnt end. Now heat a piece till it is just kicking off a few sparks. That is about the temperature you want to start at, or just below this temperature.

Phil

Has anyone ever done any research into the proportions of heat lost through radiation into the air, into the anvil and into the stock (or tongs)?

You can look up specifics in any decent thermodynamics text book. Still air is considered a good insulator, that is why heating the anvil is more a concern than anything else for cold weather forging. The anvil is the largest heat sink typically, and tong jaws usually warm relatively quickly, and are not holding the hottest part anyways.

Steel is a relatively poor conductor of heat, especially compared to copper. This is to our benefit as you can hold steel bare handed a few inches away from a portion at welding temperature. Steel is not an insulator, heat travels through it quite readily, but large temperature changes take time to move through a bar.

Phil

Yo mang! Im in Lebanon, IL I ussually get steel from Lickenbrock Welding in O'Fallon IL. They got good steel at a good price theres the awnser im sure you were lookin for.

Dang Phil, you're gonna start thinking I'm beating up on you. You covered conduction and convection, but left out radiation! At forging heat, by far the greatest loss is from IR and broad-spectrum radiation. You can feel the heat from a foot or more away and all them escaping photons can light the room!

Interesting, I suppose rebar might cool a "little" faster. After all it has cooling fins, right?

Nope you are not beating me up. Radiant heat loss somehow that did not get in there. We keep coming back to radiant heat you and me. You are right, that is the mechanisms of heat transfer at forging temperatures are conduction and radiation in a solid fuel forge, and radiation in a gas forge. The metal looses energy primarily through radiation.

I have a strange sense of De Ja Vu here.

Phil

. Spending £500 on stock to play with seems a bit ostentatious; in the UK most stockholders will deliver within a couple of days, even for smaller orders.

fair point but
a) i'm hoping to make a business out of this, it's not just a hobby and
b ) you'd pay delivery on every order