heat treating first knife

T

torqueman

Guest
Well the first blade is looking better than I expected. Not great but Ok. I have learned a lot and I am sure my next grind will be a little better.

Anyway I want to try to heat treat this one myself. The steel is 1080. I have a gas forge. The plan is to bring it up to non-magnetic and quench it in used motor oil (I'm cheap and it is a first try.) Anyway what comes next is a mystery to me.

I have read everything from heat treating to 400 for one hour and letting air cool to heating back up in the forge and just quench the blade edge. What is the best thing (besides having someone else do it) for my fist time? Please spell it out as I ain't all that bright. Short Bus
 
1080 is pretty straight forward, no soak to speak of.
Ok, here is how I do it. I hold the knife in front of the forge to pre-heat it (this is probably not required but I feel like it stresses the steel less).
Once in the forge mind the edge that you dont overheat it, it is very easy to do. Take the blade to non magnetic, it will be red, let it go just a little more then quench in oil.
Temper at 350 for 1 hour the let cool and temper again.
I tried to keep this a simple explanation I know the first time I asked I got a lesson in metallurgy which was great but alot more than what I wanted at the time.:)

Hope this helps

Sean
 
Welcome to the wonderful world of heat treating. Two things that could help in hardening. Try to adjust the temperature of the forge down. This will decrease the tendency for the thin parts to heat up faster than the thick parts. Also let the forge burn of a little bit so that the heat distributes more evenly. If the tip gets too hot you can quinch it and return the knife to the forge. Another way to even out the temperature is to put a piece of black pipe into the forge that is big enough to accomadate the knife. If you seal one end with something, I used furnace putty, and toss a couple of pieces of charcoal into it along with the knife it will create a oxygen poor atmospher and reduce the scale formation. Don't overheat the blade; bright read should be fine. (Ok, that's more than two things, consider it a bonus ;-})

I like to temper three cycles for two hours to make sure that any retained austinite is converted to martensite and is then tempered. Starting out at 350 is good but be aware that you might have to retemper if it is too hard. You can always retemper at 25 degree incriments until the correct hardness is reached. I test by cutting through some bailing wire. If the knife chips out all I would have to do is grind out the chip and increase the tempering heat. If it is too soft and the edge rolls over it is necessary to repeat the hardening and then retemper. I use the kitchen oven to temper in (no wife to ask permission). I place a themometer on the same rack as the knife and check it periodically. The setting on the oven is not reliable.

Doug Lester
 
Thanks guys. I am going to give it a try. The process does not sound too hard but getting the stars to line up sounds like some trial and error.
 
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