Heat treating O1 tool steel

[WorkHorse]

I am going to start making some knives hopefully very soon. I have made a gas propane forge to use for hardening and I am going to be using a toaster oven to help temper it so that it will be tempered correctly at 400 degrees. I know to properly harden the steel it needs to be 1250- 1300 degrees, but how will i know when it reaches that temperature. I have read where people have said you just heat it up till it looses magnetism, but I have also read where people said it needs to be hotter than that.

My gas forge is made up firebrick and the torch is made like this
http://www.instructables.com/id/how-...-forge-burner/

[R. Yates]

NO it does not need to be hotter the place you get the steel should tell you what the temp should be for HT follow it . Nice burner by the way .

Sam

[Doug Lester]

Excuse me, but steel does not change phase, austinize, until it reaches 1341? F., but that's not the end of the story. You also have to get the carbon into solution to harden it to martnesite. For simple steels where the carbon is primarily locked up in cementite that doesn't take too much of a higher temperature, maybe 1450-1475? for a hypereutectic (more than 77 points of carbon), a little hotter, arount 1500-1550? for a hypoeutectic steel (less than 77 points of carbon). For more complex steels such as O1 or 5160 the carbides are harder to disolve and you may have to go a bit hotter, unless you are dealing with a hypereutectic steel as in O1 then you may need to drop you temperature back to a little under 1500? and extend the soak time to about 5-10 minutes to prevent grain growth but not too long or too much carbon will dissolve and promote retained austinite.

Yes, you do have to know the steel that you are using and heat treating is not a one size fits all proposition. Some of the stainless steels have to be austinized up to around 1800-1900? F. with as long as a 30 minute soak. You can go to Alpha Knife Supply and look in their metals section. They maintain heat treating guidelines there for various alloys.

O1 is not the best steel to heat treat in a propane forge. I would stick with 10XX series steels or hypoeutectic higher alloy steels like 5160 or 9260. W series of tool steels are also useful but you will need to know the exact alloy of the lot you buy because they can have a carbon content from 60-140 points (0.6-1.40% carbon by weight).

Doug

[metal99]

I would take Doug's advice. I made the mistake of getting 1095 and O1 when I first started and it just made things more difficult then they had to be. Now I switched to 1084 and couldn't be happier.

[R. Yates]

Excuse Me , I find it rhetorical and a down play if a maker can not utilize other steels and deems it necessary to push others to make and forge the same steel as they do ! let the individual decide if they have the ability to work with the other steels and any other combinations that is why there are so many types of steel today .

Sam

[AUBE]

Basically sticking to a low alloy steel with close to .77% carbon is the easiest steel to heat treat for a beginner, and thats why 1075 and 1084 are often recommended.

When you start adding carbon above .77% you have to start worrying about retained austenite. When you start adding certain alloys you have to start worrying about making sure everything fully disolves at temp. With steels like O1 it is possible to do it in a forge, but it does give you a few more variables.

Even if you are off a bit with your heat treat of O1, 5160, etc it can still make a decent performing blade. Lets say you don't soak the steel long enough, it won't perform as well as it could, but many people won't realize its not at its best. The reason steels like 1070/1084 are recommended is because its easier for the average beginner to get the best out of the steel. Most people think "why pay the extra money for O1 if you can't squeeze out all the extra benefits of it?"

[WBE]

Originally Posted by Sam Cro

Excuse Me , I find it rhetorical and a down play if a maker can not utilize other steels and deems it necessary to push others to make and forge the same steel as they do ! let the individual decide if they have the ability to work with the other steels and any other combinations that is why there are so many types of steel today .

Sam

Excuse me, but I think you have much to learn yourself before giving advice to another newby, when you obviously have no idea of what you are talking about. Doug Lester knows what he is talking about, and he is not advocating others to use his choices of steel. Only that beginners should use steels of a type that they may be able to use successfully with their available equipment, level of knowledge, and avoid failures that are easily prevented with a little basic knowledge which you seem to not possess yourself.

[Ray Rogers]

Conversation is getting a bit testy. Ease up a bit guys ...

[R. Yates]

I f he has built a Gasser forge ,knows that he must heat treat, and harden . Then he is not a beginner, to making knives he may be new to making them However he asked about heat treating O1 steel and no it does not need to be Heated past the Non magnetic stage he would burn the carbon in the steel .

Now as to my Making Knives and forging Steel Yes I do and have for well over 15 years , and did so in the Military as well . I will leave it to that as you seem to be hung up on your own style and those that have more post then I do . I can tell the site is full of New knife makers and folks that are starting to Forge That is why I joined to help them out I was asked by a member to come over here to help out .

Sorry if your are offended .

Sam

[WBE]

I'm not offended. Doug may be. Apparently the people that make 01 steel have a lot to learn about heat treating it, and we are all grateful that you can correct their erroneous info on the matter. No, I am not offended, but sick to learn that I've been doing my 01 HT all wrong. Many thanks for the correction, but how do I tell all my customers that their blades have no carbon left in them? This is a real conundrum for me. I really thought I at least halfway knew how to HT it in a decent manner. This is truly a sad day.

[R. Yates]

Originally Posted by WBE

I'm not offended. Doug may be. Apparently the people that make 01 steel have a lot to learn about heat treating it, and we are all grateful that you can correct their erroneous info on the matter. No, I am not offended, but sick to learn that I've been doing my 01 HT all wrong. Many thanks for the correction, but how do I tell all my customers that their blades have no carbon left in them? This is a real conundrum for me. I really thought I at least halfway knew how to HT it in a decent manner. This is truly a sad day.

No need to be sarcastic I leave this thread to you as you seem not to need any help with anything and are being rude about my input . Be Well Brother .

Sam

[Doug Lester]

Sam, basically, it would help if you knew what you were talking about to be very blunt and very honest. My authority on that is people who have doctorates in metallurgy and a very long history of industry practices in heat treating steel. If you think that you can get steel to quench harden without heating it past non-magnetic to trigger a phase change, go for it, but there is nothing that supports your claim and a whole lot that says your opinion is totally and absolutely wrong. Burning carbon out of steel at proper forging and heat treating temperatures causes very minimal carbon loss. Even at forge welding temperatures it is not a major problem.

If you enjoy making knives, if you do make knives, the way that you indicate that you do then by all means continue but do people a favor and keep them for yourself. They're not worth using.

Doug

[ranger1]

A simple way to do a usable heat=treat is to put table salt on the blade. Correct me if I'm wrong but I believe it melts at about 1425 deg F. I have used this on some fun competitions where we had to make a serviceable knife in 2 hrs. With no other way to tell temp. it works pretty well. But, I normally use 1084 for these demo's

[Doug Lester]

That sounds like it would work well for 1084 but one size does not fit all. The temperature "crayons" would be another option that would serve the same purpose. Some of your more complex steels with tungsten and vanadium need higher temperatures to austinize or, more precisely, dissolve their carbides and put their carbon into solution. Also time is a factor.

Doug

[AUBE]

Originally Posted by Sam Cro

I f he has built a Gasser forge ,knows that he must heat treat, and harden . Then he is not a beginner, to making knives he may be new to making them

Sam, just because he knows he must "heat treat and harden", does not mean he is not a beginner. Thats like saying someone that has never driven a car isn't a beginner because they know they need to hit the brake and gas.


I think this discussion highlights the problem of heat treating with a simple setup like a forge... In a digitally controlled oven you can simply set it to hit a certain temp (lets say 1500) and you know when it hits that temp. Using a basic forge it can be hard to know the exact temp so instead of saying "heat to 1500" we say "heat to non magnetic and then go slightly higher" One mans "slightly" may vary from another mans.

By "slightly" most people mean 50-100 degrees higher than the curie (non magnetic) point. At that slight increase you won't have to worry about burning out carbon, that occurs at higher temps. Now if you definition of "slightly higher" is 400 degrees higher, then yes, you will have problems, mainly with grain growth.

So if you go by the definition of "slightly" being 50-100 degrees, then yes, you need to heat O1 slightly higher than nonmagnetic.

(let me preface this next part by saying I am NOT a metallurgist, I've only taken a few metallurgy courses and read a few books..both of which were years ago. I didn't take the time to find charts for O1, and its 11am and I haven't slept yet after a nights work so please feel free to point out where I may be mistaken)

To those of you that want to know the science behind it, you need to look at iron-carbon phase, TTT, CCT, diagrams. Heres one I pulled up with a quick Google http://www.substech.com/dokuwiki/dok...2ef3b3a0c1ce40

When we are heating up a steel to "hardening temperature" we are heating it up to the austenization temp, where the phase turns to austenite. Look on the chart and find the "acm" line. Now look for the 1% carbon (O1 is .95%carbon) line at the bottom. Find where the 2 lines intersect. We want to stay to the left of the acm line where the phase is austenite with no cementite. Notice thats at around 1475 degrees? Now look for the "a1,a2" line which is where the steel starts turning nonmagnetic. The temperature is considerably lower.

Now check with a heat treat schedule from a reputable source...lets say this one " http://www.crucible.com/eselector/ge...eralpart2.html " Notice the austenization temp is listed as 1450-1500, which matches up with what we saw in the chart.

There are different charts for each alloy steel. The addition of different elements can have a drastic effect. Carbon dissolves pretty easily, but other elements need increased temperatures and soak times. Thats why higher alloy steels are typically not recommended for beginners heat treating in a simple forge.


Ok, so what about the carbon loss that was mentioned? The carbon moves through a process called diffusion. The rate of diffusion depends on both time and temperature. Raising the temperature can have a very drastic affect on the rate of diffusion. Thats why we worry about losing carbon from steel at elevated temps. In the 1500degree range its not something to be concerned about. In the 2000 degree range the carbon will move much faster. A note of interest is that carbon moves from areas of high carbon density to areas of low carbon density. Which means if you have the hot steel in a carbon rich environment you can actually gain carbon instead of losing it if the conditions are right. Thats whats happening in carburizing processes.