01 not hardening - plz help

U

Uhurungus

Joined
Jan 8, 2015
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hey all, having some issues with my 01 not getting hard after quench.

i quenched 10 blades yesterday

*all blades are forged in a charcoal forge.
*used an evenheat oven with a brand new thermocouple (as i've had this issue recently and suspected a wrong reading). i did an oven test using a magnet and it seemed to only be about a 5-10 degree difference between non magnetic and what the oven read.
*normalized at 1400 for 5 min, then 1200 for another 3, then air cooled to room temp
*brought to 1550 and at 10 minutes, each blade brought out and checked for straightness, one at a time, hammered slightly if needed, then put back in for another 10 minute (minimum) soak
*quenched in what the receipt said was "138 degree quench oil" bought expressly for 01 quenching. it's very old oil. 3 years or so? in an old army ammo box. old enough to have a small layer of sloughed decarb on the bottom. oil temp was always between 120 and 150 degrees.

file checked them all and the file grabbed on each one.

i didn't check for decarb layer as the blades are forged pretty thin as it is. i guess this could be it, but have not had this issue in the past using the same forumula.

due to the forging could i have burned all the carbon up? these blades have been somewhat lost in the shuffle and i had no idea what has been done to them in the past so decided to renormalize and harden again. so potentially, these all could have gone through the entire process (including tempering) already.

could the oil be too old?

i'm at a loss. thanks in advance for your input.
 
These blades were they ground between forging and the beginning of your heat treat? Between forging and the amount of time they were in your oven you're going to have a pretty good layer of decarb.

I've started foil wrapping during normalising and heat cycles to reduce it myself.

Other question on your times, you shut the door and start that countdown or is that countdown from temp stabilization?
 
1550f sounds much too high for hardening 01. Kevin cashen recommends 1450-1500, I use about 1465 and my blades get super hard with very nice grain structure. In fact I've gone from 1440 all the way up to 1500 with a HT testing trial and grain size looked decent across the board, slightly finer at the lower temps. Still waiting on hardness testing results from a friend who's testing for me.

Also, i'd normalize higher around 1600f or a little more and then thermal cycle down from there about 100degrees lower on each cycle.

What's the hardness like on the spine and thicker parts of the blade? If they're harder than the thinner edge of the blade it could be a decarb issue where the edge was too thin and being held at a higher heat for an extended amount or time.

It's unlikely that the oil would be the problem imo, as O1 has a long window of time to go from austenitizing to below the pearlite nose. Some people have even successfully plate quenched thinner blades though it doesn't seem to be a recommended practice.


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they were decarbed after forging originally but nothing as far as i know after that, and like i said, i'm not too sure around the history of these blades prior to me getting at them yesterday and doing what i described. they could have possibly been cycled prior up to the hardening point. in which case there would probably be a ton of decarb...

i'm ignorant on one of the last questions though. what exactly is "temp stabilization"? once my oven is up to heat and i open the door, it only takes a minute to reach and hold target temps. is there a rule for temp stabilization times? i had a lot of knives in there and while the ones in the front got 10 minutes, the ones in the back got at least 20.

thanks for your consideration.

i had been shooting for 1525 but pulling each one out and checking for straightness before quench took a few seconds more than i'm comfortable with so i decided to up the target temp to 1550 to compensate.

the blades are at the shop so i'll have to drive in later and check a bunch of things... knew i should have brought one home.
 
When I open my furnace door the temp drops quite a bit depending how long I have it open. I don't start my soak timer until it's come back up to the target temp, which means something I'm soaking 10 minutes is actually in there 13 or 14 minutes, adding to the decarb.

You shouldn't have needed to increase temp to compensate, there's nothing to compensate for. Even if that temp is a little high and promoting grain growth it should have hardened.

File further. The only time I get a clean file skate on oil hardening steel in the first few strokes is when I heat treat in my forge with a reducing atmosphere, because there isn't any decarb from the short time at temp and reduced oxygen environment.
 
First - 1550 is almost 100F too high for the austenitization temp. The normal range is 1455-1500F with a 10-15 minute soak. I like to stay on the lower side.
Second - while 150F won't ruin a blade, the oil is best at 120-130F.

Last - take one of those blades to the grinder and start cleaning it up. I bet a few seconds after you start it will be showering bright sparks from hard steel. Grind the edge back a tad, too.

Pretty much every forged carbon steel blade has a decarb layer on it. It is best to just forge, do a basic clean up and bevel on the grinder to a 120 grit finish, HT, and do the main clean up post HT.
 
yep you guys nailed it. they were covered with a very thick layer of decarb. as in very thick. anyway they are at a nice hardness and i feel much better about things. thanks for all the input about temps as well. going to pull back to 1475 and change/clean up my process a bit regarding straightening pre quench.

thanks a bunch all!
 
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