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New maker, here. I am working on an order that is a 52100 12 inch long, 3/16 inch thick Bowie styled blade. I do alot of my research and studying on youtube (it's just how I learn best) watching videos made by reputable knife makers (i.e. Jason Knight, Kyle Royer, Fire Creek Forge, etc.) And their processes of working with certain types of steel and so on. I saw that on one of the videos I had studied for 52100 steel, the maker heat treated, cryo treated and then tempered. My reason for posting this, is to obtain a detailed proper description on the steps taken to complete this process. I use a homemade coal forge that gets more than hot enough to attain fairly controllable heat treat temps for doing my own heat treatments (I will soon be upgrading my entire setup to an actual professional level very soon, I know that my described setup isn't really ideal). The cryogenic treatment was achieved with dry ice and ethanol and I would like to use this method to acquire a few extra points of hardness in this 52100 knife and give my customer a super strong blade. 

 

If this is the wrong place to post this, I apologize. Please let me know where to move it to or where to go to read about this specific process, if that is indeed the case. 

 

Thanks!!

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I'm not certain that 52100 is improved much by a cryo treatment.  I could very well be incorrect though.  Here's a link to Kevin Cashens' page where he details his 52100 heat treat sequence.  It may not be exactly what you're looking for, but hopefully it helps.

 

http://www.cashenblades.com/steel/52100.html

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The best thing to do for toughness in 52100 is multiple normalization cycles.  Like, seven or eight.  Most steels reach a point of diminishing returns after three, but you can take the grain of 52100 down finer than industry checks for in addition to making the carbides smaller.  I also don't think dry ice cryo will do a lot for this steel.  Liquid nitrogen might add some toughness and maybe a point of hardness.

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I don't play with 52100 too much, so I had to look it up a little bit.  The ASM Heat Treater's Guide mentions that aerospace tends to use refrigeration (-95F or lower) with this alloy.  You do this immediately after an oil/polymer quench and keep it cold for at least an hour.  Then slowly warm to room temp, then temper.  This isn't really that commonly done because there is very little retained austenite to convert.  90% martensite conversion is done by about 325F, so we are darn near 100% by the time we are room temp.  

 

And yes, this was the correct sub-forum.  

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20 hours ago, Alan Longmire said:

The best thing to do for toughness in 52100 is multiple normalization cycles.  Like, seven or eight.  Most steels reach a point of diminishing returns after three, but you can take the grain of 52100 down finer than industry checks for in addition to making the carbides smaller.  I also don't think dry ice cryo will do a lot for this steel.  Liquid nitrogen might add some toughness and maybe a point of hardness.

I use 52100 a lot, I have a bucket full of Timken bearing races......
I always normalize, but 2 or 3 times max. Eight times?  What temperatures do you use?
I would be scared of cooking all the carbon out.

Another vote for for Kevin Cashen's site, my go-to reference.

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The guy who taught me about 52100 did a series of tests on 52100 from flattened ball bearings.  As-forged, the grain was what industry calls a 3.  I don't know what the units are, but they grade grain from coarse to fine on a scale of 1 to 10, with 10 being the finest, the ideal you see in a broken file.  After three normalizations, the grain was a 9.  After eight, the metallurgist who was looking at it said "It's off the scale, but I'd call it maybe a 13?"  

 

Temperature was estimated by decalescence in a gas-fired drum forge.  The steel was allowed to cool to black as seen in a bucket painted black in dim light, then taken just to decalescence again.  

 

He made a competition cutter from that batch that outcut anything I've seen.  He even took a chunk out of the 6mm thick mild steel tabletop during the water bottle cut.  The chip out of the edge of the steel tabletop was a clean cut about 20mm long and three mm deep in the center.  The knife had no discernable damage or loss of sharpness.  

 

Decarb is not an issue in a reducing atmosphere.  That said, knowing you have an electric furnace, this same guy bought an electric furnace and had to completely redo his HT methods.  Lost a lot of blades before he realized he needed anti-scale powder or HT foil.  So yes, you are right to worry about decarb with your setup!

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28 minutes ago, Alan Longmire said:

I don't know what the units are, but they grade grain from coarse to fine on a scale of 1 to 10, with 10 being the finest, the ideal you see in a broken file.

I do!  It is based on the number of grains per unit of area, as measured in an optical microscope.  This is done by polishing a cross-section and etching it, then going in and taking a look and actually counting grains.  It is only really a valid number when the grains are relatively uniform in size and distribution.  The old formulation was N = 2^(n-1), where N is the number of grains counted at 100x magnification per square inch, and n is the ASTM grain size number.  My understanding is that there is a new formula, n = (3.321928*log10(N))-2.954 where n is the grain size number, but now N is the number of grains counted at 1X in 1mm^2.  This appears to be covered by AST E112, which I do not have a copy of because we do not use it.  

 

Therefore a grain size number of 10 would indicate about 7,500 grains per square mm.  That is why it looks so smooth.  Using the older formula we would get 512 grains per in^2 at 100X magnification.  I like the older way because it is far less counting.  Then again, it is often done with software now, and computers can count pretty high pretty fast.  Doing it manually involves more math, because you aren't really looking at a set sized area of 1 in^2 or 1mm^2.  

 

More info on the Olympus website.  

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Yet again why I love this place.....
@Alan Longmire I know I did good heat treats in my charcoal forge with a pipe, time and usage has shown that.  I love the accuracy of the kiln, removes any doubt, but reading this reinforces a feeling I've had for a while that I should get a secondary (most likely gas) forge for heat treating, or maybe a charcoal forge specifically for longer blades.

Thank you for sharing that very interesting bit of information. 

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Thank you all, for sharing this invaluable knowledge on this thread. I have found that my first try working with 52100 and putting your advice into practice in my coal forge worked out beautifully! I still have some scrap 52100 that I'm going to cut up into 3 inch pieces and do some testing with heat treat processes. Its easily my new favorite blade steel!

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This is the 52100 blade that I have been working on since posting this question. I have heat treated and profiled and am now hand sanding and polishing. Its 3/16 thick, 12 inches long and 1 1/4 wide. I tempered at 350 for 2 one and a half hour cycles. 

20210128_012432.jpg

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6 hours ago, Gerhard Gerber said:


@Widney Burton it is an amazing steel, and nothing else I've experienced take such a beautiful dark & durable coffee etch.

I was actually gonna etch this blade to make the spine very dark and the bevels bright. Good to know that it takes on a good etch!

Edited by Widney Burton
Misspelling
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I just heat treated some of the barrons 52100 last night. Normalized it and thermal cycled it 5 times.

There is a small tail(for lack of a better word) below the ricasso.....I do that on purpose because it helps me keep my plunge lines crisper.

Its only about 3/4"x3/4". I am gonna cut it off and attempt to snap it. If I am successful I will post some pics.

Any suggestions on trying to break something that small?

I have NOT tempered it yet....and was just thinking of putting it in the vise horizontally the hitting it in the center with a hammer and chisel.

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That ought to work, but wear your safety glasses!  I'd also put tape on both sides of the 52100, that way you may have a chance of finding it after it breaks.;)

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Were you successful in snapping that small piece? I was going to say use a hammer and your vise but I never would have thought to tape it lol that's good thinking. I think I'm going to start leaving a piece of extra steel sticking off the side of all of my blades from now on to cut off and try snapping after I heat treat them. Thats a great idea to get data on my blades heat treatment! 

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2 hours ago, Widney Burton said:

Were you successful in snapping that small piece? I was going to say use a hammer and your vise but I never would have thought to tape it lol that's good thinking. I think I'm going to start leaving a piece of extra steel sticking off the side of all of my blades from now on to cut off and try snapping after I heat treat them. Thats a great idea to get data on my blades heat treatment! 

Horizontal in the vice I just kept knocking through the vice. Put it in vertically .....tightened the vice as tight as I could......and ended up knocking it outta the vice several times. I though not being tempered it would snap fairly easily. I was wrong. lol

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Well, it is pretty tough steel... :lol:  I'd have thought that horizontal with a small gap between the jaws, struck hard with a blunt chisel would do it, though.  Or maybe not!

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