My Very First Heat Treat

CDHumiston said:
I am absolutely going to refine my process until I get it right. I was just surprised at the strength of the blade this being my very first heat treat and destructive test.
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Very Exciting, :D first of many, many heat treats.

@Larrin has a cool website called
"Knifesteelnerds" it's an excellent resource to get a good understanding of all the wonderful details.

Stay Curious :)
 
DevinT said:
How do you know what temperature the blade is?

Hoss
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CDHumiston CDHumiston

This gentleman is Devin Thomas, he is an extraordinary knife maker and pioneer in the world of advanced heat treatment and steel.

He is well known for his exotic pattern wielded stainless damacus.

He has been doing this longer than most folks here have been alive.

Anything you can learn from him is quite a treasure.
 
DevinT said:
How do you know what temperature the blade is?

Hoss
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I have a thermocouple heat sensor in my gas forge and a pretty decent regulator. I'm able to stabilize the forge pretty well.
I've also been trying to learn to tell by the color of the steel when heating.
 
And just to clarify some terminology (you keep bringing up "normalizing"). That is different from "thermal cycling", the process in which grain is refined. Normalizing is a high heat process that is done, particularly after forging, to even out overall grain structure. Usually this is about 150F give or take hotter than your hardening temperature. 1600F-1650F for 1095, for example. While the grain structure gets evened out, often in steels that have little alloying/carbides to pin grain boundaries like 1095, it results in large grain. But after the normalizing process is done, you drop down to roughly your hardening temp (or slightly under), and do the same thing 3 or 4 times. This is called "thermal cycling", and it is this heat process that packs more grains into a given volume, thus "shrinking" the grain. Some makers use the term "normalizing" when actually they are referring to "thermal cycling". This would be a VERY simplified order of operations:
1. forging (up to 2100F)
2. normalizing (1650F)
3. thermal cycling (1500F, as low as 1425F)
4. annealing (a slow temp drop from roughly hardening temp down to 1200F or ambient, not "required" if you are ready to harden)
5. austenitizing/hardening and then the quench (1475F, short soak if you can and then quench in fast oil, 130F canola, or water)
6. any cold treatments you may want to use (not "required" for low alloy steels like 1095)
7. tempering (300F-450F depending on application)
 
I made some 4" coupons yesterday. I heat treated them as suggested by Joshua. Problem is I can't seem to apply enough force to snap them! I tried putting them in my vise and clamping
a set of vise gips on them, but I guess I'm not strong enough. I need to find a piece of steel pipe that will fit around them to give me more leverage...
 
You can also score the coupons, take an angle grinder and make a very shallow cut across the width then break them but like Daniel said just hit them with a hammer they will break
 
Here are some pieces I did this morning. I have my notes on all the parameters.

Do these look better than the first heat treat? Do any of them look close to being there?

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Take a mental note of what the color looked like on those samples and go much lower, my guess is your over shooting by 100-200 degrees. Once a magnet stops sticking keep the piece in the forge just a bit longer so it’s a even color but you don’t want to leave it in too long, from non magnetic to ready to quench can be a matter of seconds. Also a steel tube inside the forge can help even out the heat so you aren’t getting direct heat from the burners.
 
Thanks for the analysis! I'm learning as I go. I have kept good notes and a mental picture of the color of the steel when ready to quench.

The forge was very close to a stable 1500 when I did those. However I may have left them in to long.

I tried breaking the ones I did yesterday again and they just won't break. They still seem to have some
bend properties in them. I'm guessing maybe not hot enough on those?
 
One other thing, can you tell me which of the 3 is the best? These were done with different parameters so I'll know where I'm going.
 
CDHumiston said:
I used a 3lb forging hammer and that's the biggest I have. The issue may be my vise being on a small table and moving under the force of the hammer.
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If they hardened right they should break just looking in them no hammer needed :) Try water or brine .
 
Also though yes if you can't break them fairly easily and they are not tempered they probably didn't get to full hardness. Depending on the design of your forge and the placement of the probe it doesn't mean that the probe being 1500F also means the knife is 1500F. I'd say the middle picture is best but it's all pretty similar.
 
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