52100 Chef knife tempering help

PaulDiStefano

PaulDiStefano

Joined
Nov 14, 2016
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636
Hello everyone, I have made a chef knife with the design of a Chinese pork cleaver.
The main purpose of these knives are to be used as chef knives. They are not for chopping but for general kitchen work like you would use any 8" chef knife. The blade is very thin and is only meant for slicing, not heavy chopping.
I followed heat treat/ thermal cycle instructions from Stacy Apelt found on the forum and also Willie71. Using my Evenheat Oven
(except maybe tempering temperature)
I tempered at 425F and found the knife blade to be a little soft. I was afraid of tempering at too low a temperature because of how much carbon it has thinking it might chip. I used the brass rod test and I could see very very tiny spots that didn't go back to true and remained a little bent.

I'm not exactly sure the best way to test chef knives besides using them but i am also not experienced in this steel and I do not know how long it should stay sharp for when in use.
I don't know the hardness I have at 425F temper. In my research I found that some people like their chef knives from 61-62 HRC. I have seen Nick Wheelers Paranee blade videos and he tempered at 385F and got 62 HRC.
Does anyone know what hardnedd for 52100 for would be great for a chef knife made for slicing and what Temper temperature would help me achieve it.
Thanks guys
 
What temperature did you use to austenize? Using the old industry standard for bearings of 1500F+, guys used to have to temper at like 500F in order to get 59Rc. It sounds like the low temperature austenizing method of 1475F might give you higher initial hardness, but "soften" faster.
 
Thank you for the quick reply. I used 1475 but for some reason was unsure if it hardened during a quick file test and I remember readin on some thread that if you see a range of aust temperature sometimes the lowest isn't the best idea so i requenched at 1500F
 
Ah. I have never used 52100, but I recall being told that it does not do well when you do it over. I will defer to the experts.
 
Also during hardness testing I don't know if this test was too extreme for a think chef knife but I did a little chop into a piece of wood and the blade bent at the exact spot it made first contact. It was only a light flick of my wrist. I also don't know how a thin knife should respond to that test. It is a 13 oz blade because it's about 8.5 inches long and 3.85 inches wide
 
If anyone else has any thoughts or insight its all welcome. I would love not to waste anymore 9 inch long 4inch wide 52100 haha it's very expensive. It is Aldo Steel by the way in case that helps with anything
 
If you followed the directions given by Stacy & Willie71, they should have already warned you about the opportunity of resetting the heavy spheroidized conditions of the as bought 52100. Very big carbides, floating into a matrix of iron, will let go the carbon only at higher temperatures or incredibly longer soaking. Smaller carbides, finely dispersed all over the matrix will disappear very quickly at 1475 °F, making for a quick and easy final austenitizing.
Normalizing thoroughly that steel before that austenitizing is thus important, to unlock the carbon and render it readily available for the final austenitization and quench.
If you attempt to austenitize the steel "as is" (spheroidized) with normal time/temperature soaking, you run the risk to only scrape a slight amount of the carbon from the huge carbides and put it in solution, and the resulting martensite will be softer than expected to begin with.
Of course if that is the case, tempering will let drop the not-so-high hardness very quickly.
The full hard martensite of 52100 will require a lot of temperature to drop in tempering.
 
There is a whole 52100 thread in the Stickys. That is one reason we recommend a new maker read the stickys before making a knife.

When asking about a problem, we need all the info to give an answer. Give:
The steel and its source
The thickness and other dimensions of the blade
Edge thickness
Type of heating method/device for austenitization
Any blade surface protection methods used
Austenitization temperatures and hold times
Quenchant and quench method
Cryo or sub zero method used ( applies to high alloy or stainless steels)
Tempering device, temperatures and times
 
The 52100 is .094 from Aldo which is probably more like .105 and the dimensions are 8.5 long 3.86 wide. I took the edge to about the thickness of a nickel before heat treat. Using an evenheat oven with rampmaster
I brought it to 1650,1550,1450 for 10 min soak and cool to black between each cycle. Then 1475 for 15minutes then quenched in 120F canola oil. I checked with a file and thought it was biting in more than any other steel I have used from the 10xxseries so I went through all the steps again and held at 1500F for 15 min for the quench the second time around. tempered for an hour each at 425. I have read a lot about 52100 on the forum I just am confused by the results. I guess I didn't understand some things I read because the product didn't turn out so great.
Thanks Stacy.
I hope this info helps, I'm really trying to understand what's going wrong.
 
With the 1475 austentize, you need a faster quench than the higher temps need. I think you get less chromium in solution, and there isn't a lot of manganese. You don't need parks 50 fast, but heated canola should be good. I temper between 300 and 350 for kitchen knives. 450f will put you at Rc57/58 iirc. I aim for Rc63/64 for 52100 kitchen knives.

The 1500 austentize will leave you with some retained austenite, further softening the steel. You went half way between two different heat treat recipes, not optimized for either. I would put it in the oven for 10 min at 1475, quench, and temper starting at 300f. Should be as hard as woodpeckers lips at that point.
 
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I think (a guess), edge of this blade hit PN therefore it lacked of spring attribute when tested with brass rod and tiny tap into wood.

Due to large flat thermal mass of this cleaver, I suggest re-hardening as follow:

* have a brine and 120F canola oil tanks next to each other and close to oven
* assuming start from cold oven
* grind edge back to thickness at least 0.025". Coat 1/8" of the edge with clay to decrease cooling rate - preventing bacon and or crack edge in step 4.

1. Oven prg1 - 9999, 1550, 30 * could use segment but I prefer prg - will explain why below
2. Put blade in * estimate oven will cool down to below 1400 quickly
3. Run prg2 - 9999,1460,25 * Evenheat rampmaster isn't that smart, so this way force it ramp at 9999/max
4. After 20minutes soak: quench blade with spine down in brine with very rapid slicing motion back/forth 3-5" distance for 2 seconds. * This will cool most of the blade mass below PN - ok to have small% of center mass hit PN.
5. Quick switch to 120F canola quench - same slicing motions for 20 seconds. Take out - if oil is smoking (blade is still above 425F), then same quench for another 10 seconds.
6. Take blade out (150-300F) use glove or a lot of paper towel. Wipe down oil. Straighten the blade.
7. Air cool until can hold with barehand comfortable (below 110F).
8. Soap wash, then into freezer for 10 minutes, then wash in cold water, dry
9. Into pre-heat 200-225F kitchen/toaster oven for 15 minutes. Wash. Project/expect 65+rc
10. Grind off decarb on edge to expose 90 degrees corner * it is a crude test edge against a file and scrape against knives with known hrc.
11. Temper start at 375F 30 minutes twice. * est 62-63rc.
12. Grind a edge to test. IF needed increase temper temp 25F increment to whatever edge stability you targeted/sought.

Good lucks!

PaulDiStefano said:
The 52100 is .094 from Aldo which is probably more like .105 and the dimensions are 8.5 long 3.86 wide. I took the edge to about the thickness of a nickel before heat treat. Using an evenheat oven with rampmaster
I brought it to 1650,1550,1450 for 10 min soak and cool to black between each cycle. Then 1475 for 15minutes then quenched in 120F canola oil. I checked with a file and thought it was biting in more than any other steel I have used from the 10xxseries so I went through all the steps again and held at 1500F for 15 min for the quench the second time around. tempered for an hour each at 425. I have read a lot about 52100 on the forum I just am confused by the results. I guess I didn't understand some things I read because the product didn't turn out so great.
Thanks Stacy.
I hope this info helps, I'm really trying to understand what's going wrong.
Click to expand...
 
Thanks willie71 and bluntcut. With those instructions I'm sure I'll get the exact hardness I want. You guys are the best. I was definitely tempering way to high haha. I'm gonna try both of those recipes out.
 
Highly recommend the 52100 from Alpha Knife Supply or Kelly Cupples if you run into any more problems.
 
Nothing at all wrong with Aldo's. I just finished up a Santoku in the .094 stock and had no issues at all. Normalized at 1700F, 3 cycles 1500F, 1475F, 1450F, hardened 1475F 10 minute soak, P50 quench down to 0°F, 3x tempered @ 300F, about 65HRC. Steel was very clean, very nice finish. Bars were received straight, too!
 
samuraistuart said:
Nothing at all wrong with Aldo's. I just finished up a Santoku in the .094 stock and had no issues at all. Normalized at 1700F, 3 cycles 1500F, 1475F, 1450F, hardened 1475F 10 minute soak, P50 quench down to 0°F, 3x tempered @ 300F, about 65HRC. Steel was very clean, very nice finish. Bars were received straight, too!
Click to expand...
Any pictures?
 
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