440C Heat Treat

[JTknives]

Has anyone other then me noticed the wild variance in heat treat data for 440C. I been working on a customers order which is 440C and soMe of the thinnest blades I have ever worked on. So I figured some research was in order. Most everyone says something different. The austonitzing temps seam consistent but the big difference is as quenched hardness and the temper temps and resulting hardness. I have a gut feeling that it's a data error as it seams too off. For exzample crucible and a blade steel suplyer says 200°f temper gives you 59RC. And others say around 200°c gives 59RC. Some say quench from 1850°, 1900°, 1950° And everywhere in between.

The six blades I did at 1875° with a 30min soak. I then plate quenched for a min and then removed from the foil and hand straightened the blades while still soft. Once cool i poped them in the oven at the listed 220°F for two hrs and did a RC test and two tests at 63RC. So back in at 400° and with a water quench. I rechecked the calibration on my hardness tester and it was spot on so onto the knives. I did 2 tests in the same area that gave me 63RC and hot damn a solid 60.5RC.

I know a lot of people make 440C but the data does not seam to match up. I'm not complaining as I will take harder then softer any day but if there are guys out there fallowing some of these charts as gospel and can't test hardness then thy could be way off and not even know it.

Here are the blades in question. I'm going to ask him where he got the steel. I was almost positive we where goi g to bacon edge these knives but some tender loving with gloves and thy are quite nice.

Spine

Edge

 

[KnuckleDownKnives]

Man oh man, didn't leave much metal left on those pre heat treat huh??? Hope they don't get jacked up.. Good luck.

 

[Jarrett Fleming]

When I first started out 440c was the only steel I used and in my oven soaking at 1900 for 30 minutes and 2 tempers at 400 for 2 hours gave me 59-60RC.
I haven't used it in years because people seem to turn their nose up to it now. It's a shame because it's a great steel.

 

[Larrin]

440C has a relatively large carbon range, and different manufacturers may have different target compositions. It seems many of the datasheets don't include cryo or even multiple austenitizing temperatures. The carpenter datasheet seems to be a little closer to the behavior you are describing: https://www.alphaknifesupply.com/Pictures/Info/Steel/440C-DS-Carpenter.pdf

 

[Ghostman3]

Holy batman thats thin for pre-HT!!

 

[JTknives]

Funny thing is the hardness I achieved is rather high and we did not cryo these blades. Yeah thy are thin but it was a fun challenge to see what I could do. Some times you surprise your self in the results. If this was AEB-L we might've singing a different tune.