Recommendation? Is my 440C Heat Treat Procedure Ok?

[Marc Cooper]

Hey All

Just starting to work with Stainless steels after purchasing a new Kiln. (I live on the island of Newfoundland so shipping things out to be heat treated would be a royal pain.)

I've read a lot about heat treating 440C, but wanted to make sure the Kiln schedule I've programmed is not wacky.

Sorry if this is a common question, but I want to make sure I have my head around this before I try this weekend.

1. Wrap Blade airtight in Proper Kiln Foil with a small piece of tissue to absorb oxygen;

2. Heat oven to 1500 degrees at maximum heating rate and let the knife soak at this temp for 30 minutes;

3. Raise heat to 1950 degrees at maximum heating rate and let the knife soak for 1 hour;

4. Remove Wrapped Knife and Aluminum Plate Quench to room temp before removing the foil;

5. 6+ Hours in Liquid Nitrogen;

6. Two Tempering cycles at 400 degrees for 1 hour each cycle.

Am I in the ballpark here?

 

[Natlek]

You will get answer soon from experienced knife maker I m sure . I think it is typo from your side but in any case....You can t use aluminium foil in that temperature

 

[Marc Cooper]

You will get answer soon from experienced knife maker I m sure . I think it is typo from your side but in any case....You can t use aluminium foil in that temperature

Ha. Just noticed that. Better not be aluminum foil for what I paid for it.

 

[Stacy E. Apelt - Bladesmith]

Forget the paper in the packet. Just wrap the blade and double fold the seams.
Otherwise, it looks fine.

I usually only go to 1900-1925F for 30 minutes, and I temper kitchen blades at 375F.

 

[samuraistuart]

Blades really shouldn’t be inside the kiln as it’s warming up. They should be inserted once the kiln has reached temperature and soaked for a while. That way the blade will not be exposed to temp overshoots during the full speed ramp up to heat.

There is no need for a “pre heat”. That is used for parts of complex cross sections so that the different parts of the piece can equalize before moving on to higher temps. A knife blade is a very simple cross section.

Metallurgically the faster a blade is brought to temp the better, so just insert the blade into the kiln once the readout shows your target temp and has sat there a little while. Once blade is inserted and the temperature has rebounded to your target temp, start the soak timer. You can even set the temp 100° hotter, that way there is less time for the oven to come back to temp after the door was opened. Just make sure to reset your target temp after inserting the blade. That’s a trick I learned from Nathan Carothers!

 

[Marc Cooper]

Blades really shouldn’t be inside the kiln as it’s warming up. They should be inserted once the kiln has reached temperature and soaked for a while. That way the blade will not be exposed to temp overshoots during the full speed ramp up to heat.

There is no need for a “pre heat”. That is used for parts of complex cross sections so that the different parts of the piece can equalize before moving on to higher temps. A knife blade is a very simple cross section.

Metallurgically the faster a blade is brought to temp the better, so just insert the blade into the kiln once the readout shows your target temp and has sat there a little while. Once blade is inserted and the temperature has rebounded to your target temp, start the soak timer. You can even set the temp 100° hotter, that way there is less time for the oven to come back to temp after the door was opened. Just make sure to reset your target temp after inserting the blade. That’s a trick I learned from Nathan Carothers!

Thanks! This is the type of advise that is so valuable to a new Kiln user!
Gotta say, this forum is a wealth of information!