Heat treating newbie questions

Did you really anneal it? Annealing shouldn't be necessary after machining. Stress-relieving or normalizing can be helpful if the machining imparts stresses in the work, but I'm wondering whether you mean hardening, or "austenitizing." Apologies if I'm off-base here.

What kind of oven? What was the cycle?

For the best, most consistent results hardening O-1, it should be heated to very near 1520F (within 30-40F), and held there long enough to fully austenitize the steel. Typically, this takes about a 20 minute soak. The part should then be quenched in oil, which is preheated to about 140F.

Temper right after quenching -- as soon as the part temperature drops below 160F, and before it reaches 120F. The tempering temperature depends on the desired final hardness of the part, and runs anywhere between 360F for maximum hardness (~62HRC) to usually no more than 500F (58-60HRC). Higher tempering temperatures (up to nearly 800F) are used rarely, for special applications.

To be fair, O-1 is a pretty forgiving steel. It can be hardened and tempered into an acceptable tool without being quite so finicky as I just described. A common method goes more like, "Heat until it's no longer attracted to a magnet, then quench in oil, brighten it up with some emery cloth, and temper to straw."

That indicates some loss of carbon, and it may or may not be a problem, depending on the extent of it. It happens because of heating in an oxygen-rich atmosphere.

It should help reduce the scaling, but may not be necessary.

Probably. Most likely, the softer "skin" caused by the lost carbon will be removed when you finish-grind the part.

Probably not, and only at the surface if at all.

If you need the wrap at all, yes. (This is the question that made me question my interpretation of your first question. (G))

If the scaling or loss of carbon at the surface is a problem and you have no other way to control the amount of oxygen coming into contact with the part, then use the wrap any time it's heated above 900F or so.

Cheers!

Jim

We prefer to heat treat the newbies just like we do the hardened veterans - lots of OT flaming :) Texas Parts Guy

I annealed before machining. The oven is a HT-13 oven with controller from Paragon Kilns. My recent addition :)

The procedure I used for annealing was (from buffalo precision which outlines it in their data sheet found at

1.. Anneal: Heat slowly to 1450° F, soak thoroughly. Cool 25° F per hour to 900° F. Air cool to room temperature. With this as their recommended hardening regime.

Preheat: Heat to 1200° F, and hold at this temperature until thoroughly soaked. Harden: Heat to 1475 to 1500° F. Soak at heat for 30 minutes per inch of thickness. Quench: Oil quench to 150 to 200° F. Temper immediately. Temper: Normally oil hardening steels need to be single tempered only. However, double tempering may sometimes be preferred. Soak at heat for 2 hours per inch of thickness for each temper. Air cool to room temperature between tempers. The normal tempering range for this grade is 300 to 450

Ok. If it was new stock, annealing was not needed. It comes that way from the supplier. O1 is usually even "spheroidized."

Regarding your wrap question, then, yes, you can use it to impede the scale buildup.

Cheers!

Jim

Jim sez: "Regarding your wrap question, then, yes, you can use it to impede the scale buildup."

I've made several large taps and dies us> > I annealed before machining. The oven is a HT-13 oven with controller from

.

Depends how long you heat it, too. Something treated properly with a good

1/2 to 2 hour soak will certainly have a generous bark on it.

Ditto for tempering, I can set the oven at 350°F, set something shiny and scary hard in there for an hour and it comes out not straw but more in the purple range. "Straw color" and no wrap/flux/etc. works fine for short quickies.

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

By cracky, you've got it, Tim!