Heat treatment problems

Joined
Aug 29, 2019
Messages
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Hello, new to the forum, new to knife making, about 10 months.
If you have a problem with the heat treatment process can you repeat and still achieve the desired results? I'm heat treating A-2 steel. I placed then knife in the kiln, raised the temp AFAP to 1450 set to soak for 15 minutes. At 0 hold time the temperature starts to decrease to about 1420 then increases to the set 1450. This takes about 3 minutes. As programed, after the 15 minutes soak temp, raise AFAP to 1750. Set to soak for 30 minutes. At 0 hold time same thing happens. Get this resolved, go to take the blade out and it has fallen to the bottom of the kiln (vertical kiln). Cannot get to the knife without possibly burning myself. I have protective gear but I'm going to be safe. So I shut the kiln down.
The kiln looks like it has a problem and I made a mistake hanging the blade. But can I normalize the blade perform another heat treatment and have a usable blade.

Thanks, Joe
 
Welcome to Shop Talk Joseph. Fill out your profile so we know where you are and a bit about you.

No need to normalize it, just repeat the HT.

Use 10 or 12 gauge stainless wire for the blade hangers.
 
Can someone explain to me why a preheat is required for thin knife blades in A2?

Personally I like 1775F for 30 min soak, no preheat required, followed by cryo treatment
 
I am sure Larrin will elaborate, but it isn't as important with a thin blade as it is in industry with thicker and odd shaped things. It doesn't hurt, but the things it does are not a big problem with knife blades.

It allows the entire mass to come up to the transition point before heating higher. This assures full depth of temperature to the center as well as lessens distortion. Neither is a big issue with a knife blade. As with stainless steel, it is usually fine to bring the oven up to the target temperature and put in the blade.
 
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