Couple questions before Heat Treating O1

[Jesse Smith]

I bought a piece of O1 for my second knife ever, because Jantz (I think that's where I ordered it from) said it was an easy steel to heat treat at home. Then found out it should soak for 10-20 min., which ain't happening with my weed burner. So I have been doing a bunch of searching online, and it looks like I can get the job done, if not ideal, with a simple heat and quench.

I intend to use canola oil for my quenching media, because I have some I used for my first knife, but I see that it should be heated up rather than just used at room temp? Also, I plan to temper at say 360º F. for an hour then air cool.

Now for my questions...

1. Why heat the quenching oil before quenching, and how does one determine what temp it should be heated to?

2. Does my temper temp sound about right? I was thinking 375º but thought I'd drop it a touch to make up for the less than perfect heat treating without a soak time. (shooting for somewhere around a 61-62 Rc)

3. I see triple quenched and triple tempered advertised on custom knives sometimes. Is there a benefit to tempering it more than once?

4. I know I can't hold the O1 in the 50º window that it should be soaked at for 15 min, but would there be any benefit to trying to keep it in the neighborhood of somewhere beyond magnetic for a couple minutes or so before quenching it?

5. The knife is 1/8" x 1-1/4" x 7" (2-5/8" blade) I was intending to just quench the blade and leave the spine out of the oil, but would I be better off just dunking the whole thing or not?

Thanks for your time and help!!!

 

[jdm61]

Before I got my oven, I heat treated in my NC forge using one burner, a thermocouple, a black iron pipe muffle and a quick hand on the gas valve. When i got my Chile forge, I bought one of their small 1/2 inch burners and that was easier. I then got my Paragon and the rest is history.

 

[Greenberg Woods]

1. Because oil is at its thinnest at about 140 degrees and will conduct heat away better than cold oil, so this is always going to be your quench point for 01

2. No, it is too short and too cold. Try 400-450 for two hours for the 61 rockwell you are looking for

3. It refines the grain, making it less likely to crack or damage in use.

4. It really does help to hold it there. O1 is hyper eutectoid, so you want to melt those excess carbides to get a nice consistent steel.

5. No, you should quench it all together. Differential quenching can cause cracking, but that is more common in water. If you feel the spine needs to be softer, try laying the knife blade down in about 1/4 inch of water and drawing a torch across the spine.


Sorry this is not as detailed, site erased a more complete explanation twice! if you have more questions just ask.

 

[jdm61]

The medium speed oils that I have used like the Brownells, which is supposedly repackaged Houghton, has a "sweet spot" at about 150; it is a bit faster at that temp than at both 120 and 180. When they say 11-13 second, the specs indicated that it was 11 at 150 and 13 at the other two temps and "out of bounds" when colder than 120 or hotter than 180. That is the good thing about the Parks 50. It is not listed as being effective down to 70F which means in Florida, I might have to heat it up a little bit a few of weeks out of the year.

 

[Brian Avila]

I have heat treated a lot of O-1. I use canola oil at 130F, and then temper at 400F, twice 2 hours each temper.

Triple quenching is a joke, but I do temper twice for 1-2 hours each time.

O-1 really should be soaked but I have heat treated with a torch and I know others who have as well, but I would soak as much as you can at temp.

How you quench it is up to you. If you want a softer spine you can do an edge quench, but I like to quench the entire blade.

-Brian-

 

[Jesse Smith]

Thanks guys! That cleared up my concerns, and I feel much better about this project now.

Thanks again!

 

[Stacy E. Apelt - Bladesmith]

I pretty much echo Brian's info:

Your bar of steel came to you in good internal condition from Jantz, so you don't really need to do thermal cycles or anything to get it straightened out unless you forged the blade. Avoid the triple quench voodoo. It reads good in the magazines and online, but does nothing superior in reality. Thermal cycling will do the same if it is needed. Many smiths thermal cycle the blade as part of every HT. This is not a bad idea, but probably not needed for a beginner.

Basic Procedure for O-1 with a torch or unregulated heat source:
Quench in medium speed oil at 130F. Canola should be fine.
Heat the O-1 to 1455-1500F and hold as evenly as possible for at least a minute or so ( if possible). Try and avoid overheating the edge or tip. With a HT oven, soak for 10-15 minutes.
Full quench into the oil. ( once does it, three times is not going to affect the outcome in O-1)
Temper twice at 400-425F for one hour each, and cool in water between tempers and after the last temper. ( the old advice was for two hours each, but studies have found that in blade thicknesses, one hour temper cycles are sufficient)

TIP:
If using a torch to heat a blade for HT, heat the spine area. Allow the red color to move toward the edge. Play the torch along the spine and try and get an even color. The edge is what you are most concerned with, so concentrate your attention on that area. Check the blade against a magnet every so often, and when it stops sticking, the blade is about 1425F. Heat a shade brighter red color and it should be between 1450 and 1500F. Try to keep the edge at that color ( don't worry too much about the rest of the blade or the spine....the edge is what needs to be hardened right). By playing the flame along the spine and moving it farther away or closer as needed, a torch can do the heat treatment fairly well.
Now, here is the biggest part of this tip - Do the HT at night or in a dimly lit room. The less background light around, the better ( don't be silly and try and do it in the dark, though... You need some light). Practice this on a plain bar of steel several times right before doing the blade. Once you have it down, grab the blade and do it...it will seem pretty easy.