Avoiding quenching

[Ferguson]

I have a question about quenching, or rather avoiding quenching. If I leave a piece out in the air, intending that it be annealed, what is the temperature below which I can put the work in water without affecting the metallurgy of the steel? I have been taking the work out of the forge, letting it air cool, waiting until the work is down to 300F, as measured by a non-contact thermometer. Once the work is warm, not hot, I drop the work in water to cool it so that I can sand it or drill it or perform other processes. My guess is that the real cutoff is maybe 400 or 500F. My goal is that the work be annealed, without me waiting for the work to get down to room temperature.

I said annealing, but maybe I mean normalized.

For purposes of this discussion, assume 1020, 1045, or 4130 steel. I do understand that 1020 steel is not going to harden like 1045.

I wish I had paid more attention in Metallurgy class. ;-)

Thanks.

Richard

[Rich Hale]

Lots of things will affect how this is answered: for instance; is it a carbon steel? If it is a real low carbon steel it will resist hardening by quenching using normal methods and will make no difference at wot temp you dip in quench. If it is a higher carbon steel then you need to know if it is air hardening oil hardening or water hardening. In any of these cases letting it air cool will be helpful as if it is air hardening this will leave it harder than you want to be able to drill, file or wotever.
That all being said, if you do not know wot the steel is you can use samples of it to test and see wot works for you with that particuler steel. I could spend a lot of time on this question, but that has already been done and you can see it if you go to the knife stickies on heat treat. If nothing I have done here has helped you at all, then maybe you could let us know wot the steel is and we can fill in more blanks...Hope it does help.

[Frank Turley]

You can normalize 1020 at about 1700ºF (creeping into an orange heat), but it is mild steel and you're not going to soften it appreciably. It is already pretty soft, and it doesn't have enough carbon to get tool-hard when quenched.

1045 is medium carbon steel; the digits "45" indicate approximately 0.45% (45/100 of 1%) carbon, and it contains 0.60/0.90% manganese. It will harden, usually in water. Normalize at 1550-1650ºF (bright red, just above cherry red); cool in still air. Wait until it's room temperature. Don't be impatient. Do something else in the shop until it is cool. Harden at 1475-1525ºF (bright cherry red).

4130, sometimes called "Chromoly" steel, has a typical percentage analysis of carbon 0.28/0.33; manganese o.40/0.60; silicon 0.15/0.35; chromium 0.80/1/10; manganese 0.15/0.25. Because of the alloying, it's heat treatment behavior is going to be altogether different that 1045. Forge 2150-2250ºF (yellow/white heat); normalize 1600-1700ºF (bright red); harden 1550-1600ºF (bright cherry red) for a water quench and 1575-1625ºF for oil quench. The tempering temperatures are not always specifically given, because each workpiece has its own temperature depending upon its end use. The tempering range for 4130 is 400º-1300ºF.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[thingmaker3]

Believe it or don't: you can safely quench your 4130 at 575F without hardening it - IF you cool it slowly enough. Put it in ash or vermiculite or something for five minutes or so.

[cracker72]

I have a question about quenching, or rather avoiding quenching. If I leave a piece out in the air, intending that it be annealed, what is the temperature below which I can put the work in water without affecting the metallurgy of the steel? I have been taking the work out of the forge, letting it air cool, waiting until the work is down to 300F, as measured by a non-contact thermometer. Once the work is warm, not hot, I drop the work in water to cool it so that I can sand it or drill it or perform other processes. My guess is that the real cutoff is maybe 400 or 500F. My goal is that the work be annealed, without me waiting for the work to get down to room temperature.

I said annealing, but maybe I mean normalized.

For purposes of this discussion, assume 1020, 1045, or 4130 steel. I do understand that 1020 steel is not going to harden like 1045.

I wish I had paid more attention in Metallurgy class. ;-)

Thanks.

Richard

This is just how I do it. I don't claim to be anything of an expert, etc.
I take a piece of steel, heat it to orange and draw out into a strip about three inches long and quarter inch thick. While it's still red I score it into sections with a chisel, making about five marks. Now stick it in the sand next to the forge and go to bed. Next day heat one end to orange and let the forging colours run down the length of the piece so that the last section is dark red. Pull it from the fire and remember which section was what colour. Drop it in the tub. Put it in the vice and starting at what was the orange end try and snap that section off at the chisel mark. If it's high C steel it will snap easily, low C steel will just bend. I repeat this for every chisel mark, line up the bits in order of colour and look at the metal structure at the breaks. I look for the finest grain structure with a dull grey colour which is usually in the red/dark red for hC steel.
So from this test I now know roughly what it is and what will happen to the grain structure at various quench temps.
Image

From left to right - dark red - red - orange.
See the grain enlargement with increase temps.

[MattBower]

For simple carbon steels, air cooling down to a black heat works well. Can't say about 4140. Quenching will not cause formation of martensite unless the steel is austenitic when the quench starts. That's somewhere north of 1400 F -- in some cases way north.