combining stress relief with heat treatment

[gemeengoed]

hi guys,

this is my first post here, if i am posting wrong or anything, please let me know. i am an amateur knifemaker from holland and slowly but hopefully moving up to ultimately a professional level.

i've just aquired a professional ceramic oven with a regulator which can be programmed with 7 steps per program. gearing up while waiting for this oven i have a bunch of knifes ready for heat treatment: some 1.2510 [O1] knifes and some 1.2379 [D2] knives, as wel as a couple of O1 knives which were already heat treated but have overheated tips due to grind fail.

both steels have a stress relief temperature of [roughly] 1200 F and a heat treating temperature of 1850 F and 1550 F respectively, as you undoubtetly know.

now for the question part:

- do i need heat treating foil for the stress relief part?
- is it enough to stress relief those overheated knifes of do they need full annealing?
- can i do a stress relief cycle, pull out the knives to let them cool, but leave the oven at 1200F to pop them right in for the heat treatment, or do i have to let the oven cool down to room temperature?

for example:

i program this oven to ramp up to 1200 F, hold 1200 F for a few hours, ramp up to 1550 F, hold it there for about half an hour, ramp up to 1850 and hold for about half an hour, drop to 1000 F, hold that for about 2 hrs, and stoop.

in this way in my mind i can stress relief all those knives at the same time, let them cool, pop them right back in, heat treat the O1 knives, heat treat the D2 knives, and temper the D2 knives in one go.

is that possible?

thanks in advance for your time,

cheers,
-sander

 

[Fred.Rowe]

There is no need to cool them after the run at 1200. I run a lot of 01 and use stress relief, after the 2 hours at 1200 I ramp to 1500 for the quench, I soak for ten minutes at 1500. If you are not familiar with the oven, make sure are do the ramp at less than full heat. Its easy to over heat blades when doing this. I take an hour to get to 1200 and 1/2 hour to get to 1500.

Congrats on the new oven, Fred

 

[Willie71]

You don't need foil for the stress relief on the O1. I don't work with D2 so ill let others chime in on that steel.

1850 is too hot for the O1. There will be pretty significant grain growth. To refine the grain, 1650 for 10 min, air cool to magnetic, 1550f for 10 min, cool to magnetic, 1450 for 10 min, air cool to magnetic then quench in oil. Now heat treat at 1475 (O1 is hypereuctoid, and higher than 1475 will result in some retained austentite, and larger carbides. This is fine in industrial applications, as wear resistance can be better with larger carbides, and retained austentite can be managed with sub zero treatment, but it's not great in knives.)

Temper at 425f for an hour twice, and you are good to go. :thumbup: You'll be at RC61 approximately.

 

[samuraistuart]

I usually don't work with much O1 but I am in the process of polishing a santoku I heat treated in O1. I did do a stress relief tho, without decarb protection, and did get some decarb even at 1225 f.