Heat treating 52100

L

Les Voorhies

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Can anyone give me some info on heat treating 52100. i have a forge but would prefer to heat treat it in the oven.

thanks
 
I certainly don't want to encourage any differring opinions here, but I would be very interested in hearing the approximate recipes from everyone who uses this steel. Mine is as follows:

Forge from 3/4" round stock at no more than +-1700 degrees( as judged by a thermocouple and scale)- forging by hand, this usually means that the steel has been through quite a few thermal cycles, but I've never really counted.

Normallize from critical at least three times, more if there is any question about any part of the process so far.

Heat the blade in the forge (the entire blade) to critical, soak for about 30 seconds, edge quench in +-150 degree mineral oil. Place blade in freezer overnight (I once had to go for 6 days in between quenches, but I noticed no differing results in testing)

Repeat previous steps two more times

Temper in 375 degree oven for two hours, three times, with an overnight soak in the freezer after each temper.

Test the edge with the brass rod and adjust tempering temperature accordingly. I have hade to adjust the tempering temperature as much as 30 degrees to get it right, and have had to requench one blade and temper at 350 degrees.

I think that consistent steel chemistry is very important in getting the most out of this steel, but I haven't found consistent chemistry from either Admirals round stock or from ball bearings.

I have had great success with this steel using the above recipe. It is the toughest steel I've tested and always cuts extremely well, but it is also very labor intensive.

I look forward to hearing other "recipes" as well, and hope to gain much insight from this thead.

Todd
 
I also must say that with the above recipe, I'm not trying to make a blade that will pass the ABS 90 degree bend test. Most of the blades (4 out of 7) I've tested using this recipe will bend 90 degrees without breaking, but a few did break after using a 4' cheater on the tang and applying extreme force. What I'm after is a blade that will take extreme force to break, and this steel and this recipe gives it to me. I haven't used a torque wrench to guage the psi to either bend or break each blade, but I'm satisfied that it's extreme.

I had one broken blade Rockwell tested and the spine was 55 Rc while the edge was 59-60 Rc. I assume that the air hardening properties of this steel made the spine so hard.

I look forward to seeing other maker's heat treat recipes and results.


Todd
 
Nick

Because it's got to be put somewhere untill I get back to working on it...:D Seriously, though, there is nowhere else I can store blades overnight that they could possibly derive some benefit. I haven't proven or disproven that this makes any difference, but I haven't seen where anyone else has disproven it, and it is a convenient place for me to store blades overnight. I have seen, through testing, that time between quenching cycles makes some difference in the finished blade, and that 20 hours between tempering cycles lets me get a full night's sleep and a full day's work in between cycles.:D It's nothing more than that, as far as testing the tempering goes, I'm afraid. I wish I had the time and money to work out just ten percent of the variables in my head...

Todd
 
Here is my 2 cents...



I start with 1 or 1 1/2 inch virgin 52100 stock purchased in bulk from Sullivan Steel who supply me with spec sheets and advice on heat treating.

Forging..I dont over heat, and never let it get so cool that its below a red heat.....

Normalise three times (critical and air cool) three times.I do not anneal as I see no need for my purposes. After I normalise, the steel is soft enough that I can drill, file and stamp my mark.

I use a Even heat oven...pre heat the oven to 1550F.....and use Chevron 70 quenching oil and pre heat to around 150F.

I go thru two quenching cycles to further refine the grain and set everything up for the final quench....so I pre heat to 1550 till non magnetic then full quench in warm oil...remove when below 400F and return to oven for a second quench.

The reason I do two quenches is because I did some destructive testing on multiple quench v multiple normalising, and found that mutliple quenching will refine the grain as much, (maybe more?) than normalising.
Its feesable that I could miss out the normalising and replace it by the quenching procedure to refine the grain, or maybr skip the two quenches and just rely on the triple normalising:confused: ...the jury is out on that at the moment, so I will continue this way for a while until I know more..:)

Third time will be the hardening quench...difference is that I soak the blade at 1550F for about 4 to 5 mins, depending on blade size...then quench in the preheated oil (usualy as high as 160F which gives me a very fast quench).

I tend not to do edge quenches, but either full quenches point first, or a modification of an edge quench where the blade is lowered in edge first but at a deep angle..keeping the shoulders out of the oil.
The latter quench is unlikely to give a blade that will bend 90 degrees , but is likely to bend to 45 and need a lot of weight on a preecher bar to get it there. The full quench will be very difficult to bend , but will flex a certain amount and tends to fail at aound 20 degrees or so.

If I want the blade to have more flex and be able to bend multiple times then I would either do a shallow edge quench (passed my JS this way) or a full quench and draw the back three times with a torch....but these specs are usualy outside of what I want in my knives.

My tempering oven is preheated to 400F...and the blades are placed in whilst still warm...temper for 2 hrs...remove and air cool.
Second temper is raised to 425 F for 2 hrs.
Final temper starts at 440F , but sometimes I will raise it higher if my 60 Rc file is not cutting the way I want it to...The steel is always past the bronze color, and is into the purple before I stop.


I saw a big leap in performance when I started to use a temperature controlled oven for my heat treating which meant I could give accurate soaks, compared to heat and quench in the forge. I also saw an improvement when I changed from peanut oil to using Chevron 70......


I am interested to hear what other do, especialy anyone that does a cryo cycle and what effect that has...something I am considering.

Thanks.
 
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