[Bruno]

Last week I got this heat treatment explanation from Wayne D.
It is for O1 (or in belgium / germany: 1.2510) steel. I am posting it here because it might help others as well, and this way I know where I can find it when I need it.

O1 is an oil hardening steel, so wants quenching in oil. If you do it in ice water you run the risk of cracking the steel.

From Wayne:

I use motor oil in a large turkey roasting tray
it's simple to heat treat O1,
you need a pan of motor oil a magnet aluminium kitchen foil (bacofoil) and a kitchen cooker preheated to 250 oC or gas mark 8

heat the steel in the fire until it goes a cherry red colour then touch it against the magnet if it's attracted it's not hot enough yet,
keep heating until the steel is not attracted (antimagnetic) then quench in the oil keeping all of the O1 under the surface move it around a little to stop the oil getting too hot.
take out of oil, clean with a cloth and repeat this heating 2 more times.
* at this point the O1 is very brittle so don't drop it *

when you've done this wrap the O1 in the aluminium foil - it stops your kitchen smelling of burned motor oil and helps even out the heating process

then put it in your preheated oven for 1 hour.
take it out of the oven and allow it to sit on the worksurface until it's cool enough to pick up with your hands comfortably - but not cold
then place back in the oven for 1 hour, remove allow to cool down to hand temperature,

place back in oven for 1 hour and then when you take it out allow to cool totaly.
when you remove the foil the metal should be in the range of light brown/ straw / golden/ yellow colour

this means you have heat treated it to between Rockwell 60 and 62.

[FiReSTaRT]

Would just turning off the oven and letting it cool even more gradually improve the treating process?

[C utz]

Originally Posted by FiReSTaRT

Would just turning off the oven and letting it cool even more gradually improve the treating process?

I was thinking the same thing...That's what I would have done, considering all my knife making experience (which is zero!)
I wonder what the reply is

C utz

[Wayne D]

Originally Posted by C utz

I was thinking the same thing...That's what I would have done, considering all my knife making experience (which is zero!)
I wonder what the reply is

C utz

Hi Gents,

I have actualy tried this and what I found was that the steel didn't heat treat properly and came out too soft. then when I needed to place the steel back in the oven, the oven itself was too cool, and then took time to heated back up to the temperature I needed.

remember the Oven needs to be pre-heated to the temperature before the steel
goes in.

This is my way of doing it from experience and training with other Smiths I know - BUT, I have no doubt others may have different ways of doing a Heat treat for O!

hope this helps

[randydance062449]

Thats the sequence that I learned also but applied to W1-W2(old files) and 1095 steel. The tempering in the oven is done at 200 C or 400 F. What I was taught was that you have 1 second to get the steel from the forge and into the quench oil.

[JoshEarl]

Oh, goodie, now I get to pass on all the knowledge that Mike Blue, Tim Zowada and Kevin Cashen have drummed into my head...

O1 is a very good steel, but it's not the best steel for beginners. On the plus side, it's less likely to crack than some other steels. But it needs to be treated properly if you're going to get full hardness out of it.

O1 is an alloy with a lot of chromium in it. The chromium has the effect of pulling carbon out of the steel and holding onto it. This causes the steel to be softer unless you do something about it.

To get maximum hardness out of O1, you need to heat it above the temperature where the carbon starts to dissolve back into the steel--somewhere around 1450 degrees F. Then you have to hold it there for a while without overheating it. That's the tricky part. Unless you're using a decent forge and a thermometer, or an electric heat-treating oven with digital controls, you'll probably overheat the steel pretty quickly. That will result in softer, weaker steel.

I've worked out a pretty good process for O1, but better equipment would make it more precise. Here's what I do:

Heat the steel to 1450 F, hold it for two or three minutes, then allow it to air cool. This relieves forging and grinding stresses; it's called normalizing. I normalize three times.

Heat to 1450 F and hold for 15 minutes. This is called soaking, and it allows the carbon to dissolve back into the iron.

Quench in Parks AAA quench oil, preheated to 130 F. This is a slow cooling oil. You could also use vegitable oil or any number of other oils, but this stuff was designed specifically for heat treatment. For about $10 a gallon, I'd rather just use the best.

After a minute, take the steel out and allow it to air cool. When it's cool enough to touch, put it in the oven to temper it. I temper at 425 F for two hours. Allowing the steel to cool down in one hour cycles isn't necessary.

If you do everything right, the blade should be harder than any vintage razor you've ever tried to hone. If I only temper at 400 F I can't even get the thing honed, it's so hard.

That's just how I do it.

Josh

[Wayne D]

Hi Josh,

It' interesting that you think O1 is a difficult steel for beginners, I have always found it easier to use than any others both in forging and stock removal .

the only tiem I had a problem was about 4 years ago when I couldn't get a batch of knife blades to quench properly and they were coming out too soft or too hard, after corrosponding with Brian Goode and picking his brains and a few other Smiths over on British Blades I worked out what the culprit was - it was the quenching oil I was using , so I went back to my old favourite of 20W/40 engine oil mixed gearbox oil nad it sorted my problem out.

I've always found the antimagnetic test method to be more than adequate for when to quench my blades.

but I don't use a gas forge, I use an open Forge with either coke or oak charcoal.

I do use a gas oven for for the 'cooking' later and have never had a problem with my knives, they are pretty consistent with the RC range .

but as I said earlier that's the great thing about O1 it's very forgiving and simple to use.

[Mike Blue]

Well, you're all right. A good balanced discussion. Josh has "rediscovered" O-1 after its long languishing as an abandoned blade steel in the US. We tend to go whoring off after unobtainium and wunderstahl anyway. Wayne has properly noted the UK's experience with it as a common blade steel and their knowledge thereof.

The subtleties of heat treatment include two points, one is the martensite start temperature and the martensite finish temperature. Hitting both of those is required to make the best difference of hard and soft. Slow cooling in the oven denies these points on one end or the other. Missing the Ms point (Randy: less than a second) will help you miss right off the bat.

I'd add only one more thing. Motor oil (used or new), as a quenchant, stinks. Literally a great way to have SWMBO ask very sharp and pointy questions about what you think you are doing. No answer you give will be correct. Especially when you're standing in mid-kitchen en flagrant delicto....

No death you can imagine will be any more horrible.

If you're a bachelor, go for it.

[mastermute]

The kitchen is my domain.. the only thing I allow my SWMBO to use there is the dishwasher!

[JoshEarl]

Wayne,

I agree that O1 is a great steel, and in some ways it's good for beginners. (I'm still in that category, so take my statements with a grain of salt.) I would go so far as to say that O1 is a fantastic steel, especially for razors. My only beef with it right now is that I'm having trouble drilling holes after forging, and I wasted a few hours over the last couple of weeks messing around with this stinkin' blade... The extra carbon in the steel forms nasty carbides once it's heated to forge, and I haven't figured out how to soften it again for drilling. But anyway...

The stuff about O1 needing to soak to get maximum benefit out of the steel is from Kevin Cashen, who is a well regarded bladesmith and really knows his metallurgy. In order to get full hardness from the quench, O1 needs a proper soak. That will put the blade up into the RC 67 range out of the quench, and the temper will draw it down from there. Kevin's point is that O1 has the potential to outperform simple carbon steels if heat treated properly. If a simpler treatment is used, it will "just" equal other less expensive steels.

Using non-magnetic as a marker will still get the blade very hard, and I'm sure it's plenty hard to make a great razor. I've shaved for several months with a razor that's probably in the 52-55 range, and it works great. Yours are probably a lot harder than that, as I messed up the heat-treatment on that particular blade.

But for a guy who's just starting out, I think I would recommend something like 1080 carbon steel. It's much cheaper than O1, and with a basic heat-treatment setup it'll probably be just as good. I think you UK guys have a hard time getting some of the steels we have over here in the U.S., so that changes things a bit.

Josh

[JoshEarl]

I wanted to reinforce something Mike said. Randy mentioned the one second guideline for getting the blade from the fire into the quench oil. This is a common misconception. Where the one second comes in is mainly after you quench the steel.

It's not a good idea to dilly dally once you take the blade out of the forge or furnace, but steel doesn't air cool that quickly. Two or three seconds might be fine. Just move quickly to quench the blade, but don't rush.

Once you immerse the blade into the quenchant, the cooling speed of the oil becomes very important. Thicker oils, like motor oil, will disperse the heat more slowly, slowing the cooling process. Some steels are OK with slower cooling. However, a steel like 1095, for example, needs a thin, fast cooling oil. Preheating the oil to around 130 degrees F makes it more viscious, so it disperses the heat more quickly.

Each steel has its own formula, but basically you need to get it from it's critical temperature to somewhere between 600 and 800 degrees in a set timeframe, and then it can cool more slowly.

Josh