heat treating/tempering

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blademan85

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Dec 25, 2012
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Hello,I am new here and just getting started in the art of knife making.I have made 11 knives and all by file only.I am currently working with 52100 1/8" thick and wanting to know if anyone has some experince wit treating/tempering this and what that procedure would be..I have been thru several pieces and it seems to be getting to soft..Almost to the point of maybe RE annealing?Thank for helping a greenhorn...Mike
 
come on guys help this guy out? tell him about the three heat treatments Criticle point, annealing, and then the hard finish tempering. i'm not a teacher nor experience in file knife making process. but the book "Step by Step Knife Making", by David Boyle, discusses it. it's good book for the beginner. F.Y.I. the folks on this forum ignore the words just learning, so try a different approach when asking a question next time. good luck
 
Well, a good simple heat treat recipe. All you need in tools is a torch, a magnet, and some sort of oven that is fairly accurate and a decent oven thermometer. I won't really get into the three quenches vs. single quench, except to say to experiment and find out what works best for you. For me with my shop triple quenching works for me, your milage may very.

Basically, on smaller knives anyway, I bring up to just above non magnetic, the point where a magnet is no long attracted to the steel. You'll see a slight color change once it gets above non magnetic. Let it air cool, I do this three times. It's called normalizing and it's a stress relieving cycle and helps refine the grain. Bring up to just above nonmagnetic and quench in warm oil. Oil can be just about anything, but my personal favorite is Texaco type A, but I've used standard vet grade mineral oil as well. I like to heat the oil to around 130 deg. F. Allow the blade to cool down in the oil overnight, repeat the quench twice more over the next two days. Then to tempering, I like to do mine around 370 deg. F. for two hours, let cool to room temp and do twice more. Sharpen and test the edge for flex, if the edge flexes and doesn't chip or stay flexed your good to go. If the edge chips bring your tempering temp up a bit, say 10-15 degree and temper again, if it stays flexed you'll need to re harden and temper a bit lower, say starting at 350.

There are a lot of variations and extra steps you can add, but that's the gist of it. And I'd suggest for your own knowledge to try a blade with a single quench, and one with a triple quench and test the crap out of both and see which does better for you.

Edited to add, when using a magnet to find your harding temp, remember you've only got to go about another 50 deg. or so hotter so be careful not to over heat the blade, 52100 is less forgiving than a lot of steels when it comes to overheating. If using a torch to "paint" the edge hot it's best to practice on some scrap steel to get the hang of it.
 
To really give a good answer, we need a good question. There are several things that you need to include in a post on HT.
How are you doing the HT? (What equipment are you using?)
What method are you using to shape the knife?
Where is the steel from?

Here is the search engine to use in researching a subject.
http://www.google.com/cse/home?cx=011197018607028182644:qfobr3dlcra

Here is a very extensive discussion on the HT of the three main steel categories:
http://www.bladeforums.com/forums/showthread.php/673173-Working-the-three-steel-types

52100 is one of those steels that gets a lot of discussion. It can make a great knife, but the HT for it is not simple. It can make an OK knife with simpler procedures. Ed Fowler is a person who uses 52100 extensively, and has procedures that he likes. You might want to send him an email for his thoughts.
Will52100 gave a basic guide to this steel, but I would point out that 50° above non-magnetic is still 100° too cool for getting a full hardness from 52100.

I will tell you the metallurgical way to do the HT for 52100:
The steel has 1% carbon and 1.4% chromium. This means that it is hyper-eutectiod steel with a fair amount of alloy to form chromium carbides. You will have to do the HT in such a way as to allow those elements to form the proper structures. To do this you will need a HT oven or forge that can be held at a controlled temperature for ten minutes, and a quench oil that will harden the blade. The oil should be a medium speed commercial quench oil, but Canola will do if nothing else is available. Forget about motor oil and ATF, etc.

Forging - Forge 52100 HOT. It is forged between 1700°F and 2100°F, and should not be forged in the lower red colors.
Normalize ( stress relieve) - Heat to 1650°F and air cool.
Annealing is tricky for 52100. The best way without really good equipment is to do a sub-critical anneal. Heat to 1250°F and cool to black. Then quench in oil. Do this a couple times.
Cycling the steel - This is one of the Triple Treatments often mentioned with 52100. It will get the steel ready for its final hardness and produce a fine grain. Start by heating the steel to 1650°F and quench in oil. Re-heat to 1350°F and quench in oil. Heat again to 1250° and cool to black, then quench in oil. Now the steel is ready to harden.
Hardening - Heat the steel to 1500-1525°F and hold for ten minutes. Quench in oil.
Tempering - Immediately temper at 400-450°F for two hours, cool in running water, and repeat the temper.
Cryo/Sub-zero treatment - 52100 can gain from cryo if you have the ability. Do a snap temper at 300°F and them immerse in a sub-zero bath at
-100° or in LN at -325°F. (An overnight stay in the home freezer won't do anything metallurgically.) After the sub-zero/cryo bath, temper as normal.
 
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First of all: all 52100 is not the same. You have to learn with each batch.
Once you find a batch you can understand get enough that you will never have to change. Each batch of steel has its own variables, these can cause nothing but confusion.
Then you learn that steel and you will soon that you will never know all there is to know. The textbooks will not tell you, only your personal performance testing of the knives you develop will teach you.

Some hold onto the written word like drunks holding onto a lamppost for support while others seek to see how far they can go by the illumination provided by those who came before.

There is only one rule: Enjoy your voyage with the steel of your choice.

When you want to know the value of the knowledge your are receiving, just ask the teacher how he tests his blades and go from there.
 
Thanks so much for the info.Its seems as though my method of heating is far to basic.I am using a pit forge to heat to non magnetic.Do not know the exact temps..The temps i am able to control are the pre heat of oil for quench and oven temp for tempering.Cryogenic freeze and ya lost me...sorry.I am starting to understand the fact that all steel do not react the same..1095/52100/15n20 and 1075 are the steels i have worked with..all from Njsteelbarron.The 1095 came out very nice..but the 52100 just seems a bit soft.some one wanted me to mention how i am shaping my blades.I use files only.Thanks for all the help.
 
I started just like you are, cold chisel, blow torch, files and emery cloth. You can do it.
 
when i get to knife talk and try to enter thte letters of the photo shown there is no picture?or letters..
 
Take Ed up on his offer of help. We don't always agree on everything, but we certainly agree that he has done a lot of 52100 blades.
 
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