Heat Treating O1 For Blades

[ex_isp]

I've been using O1 for quite some time due to it's balance of abrasion resistance, toughness and hardness.

I use a gas forge that runs at about 3K degrees F. Hot enough to reach forge welding temps with ease. 2 full in. of Kaowool liner. Gets up to temp very quickly. Almost too hot for heat treats without being VERY careful.

I used to use a decarb preventer that does a reasonable job... I've used a powder product that melts on warm steel going a glassy surface and keeps th O2 off the steel at HT temps. Two weeks ago, I made a minor change to the way I HT in this forge. I assume most know about the preheat soak time with O1 (and others) as opposed to 10 series steels where you just get it non-magnetic and quench it.

I have begun doing my heat treats outside the forge body right at the opening of the forge with a very rich fuel mixture. Definite "dragons breath" from the front. I'm not using any decarb products any more and am getting less scale than with it due to the slow heating and rich fuel. This is much to do with the highly rich heat plume coming out the front of the forge and the fact that it is heating much slower to the non-magnetic temp. In this process, I'm taking a full 10 mins in this fuel rich atmosphere to reach "semi-magnetic". Another 2-3 mins and it's fully non-magnetic. So this is my soak period and is MUCH easier to not overcook the steel.

So yesterday I made a short version to simulate the ABS 90 degree bend test. Total length, 6". No handle room and less blade length, creating a much sharper bend then is allowed on the ABS bend/break test. 1.5" was in the vise and 1" in a 14" adjustable end wrench, forcing an abnormally short bend radius. No break even on the edge and mostly, returned to straight. I was wowed! Still shaving sharp. Gripped the blade tightly with 2 visegrip pliers to prevent it slipping on a chop test. Remember, this is just a blade stopping at the ricasso. Chop test was survived and still shaving sharp.

Conclusion? Even with proper soak times at pre-heat and at Austenitic temp, SLOW, long heat has made a huge difference. Now the REAL surprising part for me. Even drawn back to 54 RHc for this test (according to the tables (650F for 54-55 RHc and double drawn), a new Nicholson halfround file still skates on it! That part I don't understand, but like!

Looking forward to any comments on this test and observation

 

[rgray]

Happy to hear someone is using 01 for blades. I'm not sold on some of these fancy blade steels now days, Seems they make a pretty knife but making it/keeping it sharp is challenging.
I can see a forge like that being a challenge. I use an electric furnace and so achieving a "temp" is easy. Just set the temp and it goes there. The book I have agrees with your plan for slower heating. It says cook at 1200 for 20 min per inch cross section, and then 5 min per inch cross section at 1500 then quench.
Book also says you can cook it at 1200 indefinitely without damage. And can raise it to it's tempered temp all you want without damaging or softening it.
I don't see much scale on 01. Sometimes there is more of a shell that is laying in the oven after cooking and I often think it's the oil layer because I didn't clean it well before heating. If I clean it well before then there is often none of that residue left in the oven.

 

[ex_isp]

Completely agree, rgray! Most often, I don't clean the quench oil off before tempering but to perhaps do a light wipe with a paper towel. Blades willperhaps enrich their black color a tad over what the hardening did, but the slower
HT has reduced my scale. Wish I had a temp controlled oven but for now, HTs are in the forge.

Do you use O1, or something else? I normally use (for quick access) Kevin Cashens page for my charts but also have "Heat Treatment, Selection, and Application of Tool Steels" book when I want greater detail
on a steel I may not be as familiar with. It's from "Modern Machine Shop Publications" and is chock full of good, detailed info.

I mentioned a few weeks back that I would be starting a power hammer project and try to document it. I'll be starting a new thread today as I just picked up steel for it today.

 

[rgray]

Do you use O1, or something else?

I always have some 01 around. Both flat and round stock. I'm not much of a knifemaker , have just played with it a little.
Built a few throwing knifes from o1 and a couple from automotive leaf springs. Strated a sword project from a leaf spring but haven't gotten far with it.
Hadn't seen Kevin Cashens site before. lots of good stuff there.
I also use that book "Heat treatment selection and application of tool steels" great book.

 

[ex_isp]

Glad you like Cashens site. Not quite the detail you get from the books, but if you already have familiarity with the steels you use most,
it's a wonderful quick reference!