440C Heat Treatment for Dummy

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Pat.Sevigny

Joined
Apr 10, 2013
Messages
3
Hello all ...!

I am a Rookie Knives Builder, I build generally big knife with stainless 440C with 1/4 inch thickness. I built a forge propane that works very well ...

http://youtu.be/9lYqDM_9Uj8


Q: How do you heat treatment for hardening stainless 440C ...!

I read MANY FORUM, lots of info on many site, sometimes there much difference between the treatment recommended by the manufacturer of metal and those of Knives Builder.

Usually, on the sites of 440C stainless producer, they recommend always the following treatment:

1. To anneal 440C stainless steel, heat uniformly to 840-875°C. Soak and cool very slowly in the furnace.

2. To harden stainless steel 440C heat to 1010-1070°C, fully soak and quench in warm oil or air cool. Be careful not to overheat or full hardness will not be obtained.

3. When tempering 440C a Rockwell hardness of 60HRc can be obtained. Temper for at least one hour. Tempering above 400°C is not recommended as this can cause a reduction in corrosion resistance and impact properties.

Some References:

http://www.westyorkssteel.com/stainless-steel/martensitic/440c/
http://cartech.ides.com/datasheet.aspx?i=103&e=72
http://www.beartechalloys.com/440-stainless-steel.html
http://www.interlloy.com.au/data_sheets/stainless_steel/440c.html

Personally I use the method recommended by the manufacturer. however, several knivemakers have very particular method, may be it is based on the thickness and size of the blade ?

what do you think..?

What is your surefire recipe for tempering 440C..?

thank you.

excuse the quality of my English, I speak French ... and Google translate :D
 
The blade must be enclosed in a stainless foil packet to keep all oxygen away from the blade.
Pre-heat at 1400F ( 760C) and hold for 10 minutes.
Raise temperature to austenitize at 1900F (1040C) and hold for 30 minutes.
Air cool or use aluminum quench plates. ( quench plates are best to prevent warp)
Cool in water to room temperature.
Immediately chill to at least -95F (-70C) for 30 minutes.
Allow to warm to room temperature.
Temper at 375F (190C) for two hours, cool in water to room temperature, and repeat the temper for a second two hours.
 
Thank you very much for your quick response.

For my personal knowledge I have a few questions:

If the metal was aneahealed in factory and I will only harden, is that I can skip steps in this procedure..?

If I do not put the blade in a stainless foil bag, what will happen? curing too? or the opposite ?

thank you.
 
I think most will tell you that in order to heat treat 440C you will need a heat treat oven to do it...it needs to be a controlled ramp up/hold ramp up/hold and quench....
 
440C must be placed in a pouch or the oxydation will eat into the blade and the scale will be extremely hard to remove. Use pouches or alternatively use an oxygen free atmosphere in the HT oven by injecting nitrogen during HT to displace atmospheric oxygen.
 
Annealed steel won't save any steps in the HT. All steps are required.

The sealed foil pouch and controlled heat source are necessary to HT any stainless steel.
 
Really hot this forum,

I am currently on the project to put a thermometer in my propane forge to be able to control the temperature, is that someone can suggest where I can find this kind of high temperature thermometer?

Regarding the stainless foil, I have seen several brands and thicknesses on e-bay, do you have any suggestions?

thank you again for your answers.
 
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