Heat treat in kiln

C

ChrisKuhn

Joined
Aug 30, 2024
Messages
10
Good morning—I recently got a HT oven and am enjoying the precision it offers.

When heat treating, I’ve been putting the blade in the oven and letting it heat up to goal, then soaking dependent on thickness, then quenching.

My blades are getting hard, but having watched some vids on Knife Steel Needs, I’m concerned that possibly it is wrong to put the cold blade in the cold oven and let them heat up together, with carbides going into solution for too long, etc…

So, is this wrong and why?
Do folks here do preheats?

Appreciate your experience and insights.

Thanks.
 
Putting things in the oven and allowing them to heat up with the oven is used in industry for large and thick objects that heat slowly..
A pre-heat step at 1200 degrees is for thick objects, not thin knife blades.
The preferred way to HT a knife blade is to set the oven temperature and once it has reached temperature let it soak for about 15 minutes. Then place the blade in the oven and start timing when it rebounds (usually less than 1 minute).
 
Stacy E. Apelt - Bladesmith said:
Putting things in the oven and allowing them to heat up with the oven is used in industry for large and thick objects that heat slowly..
A pre-heat step at 1200 degrees is for thick objects, not thin knife blades.
The preferred way to HT a knife blade is to set the oven temperature and once it has reached temperature let it soak for about 15 minutes. Then place the blade in the oven and start timing when it rebounds (usually less than 1 minute).
Click to expand...
Got it, thanks, and that’s how I will do it future.

Would you say it’s likely that blades I heated up with the oven are compromised in some way even though they did harden and are holding an edge?

Wondering how much confidence I can have in those knives…
 
Stacy E. Apelt - Bladesmith said:
Putting things in the oven and allowing them to heat up with the oven is used in industry for large and thick objects that heat slowly..
A pre-heat step at 1200 degrees is for thick objects, not thin knife blades.
The preferred way to HT a knife blade is to set the oven temperature and once it has reached temperature let it soak for about 15 minutes. Then place the blade in the oven and start timing when it rebounds (usually less than 1 minute).
Click to expand...
Stacy
I was going to ask a similar question as the OP as I have an oven on the way. I think I read somewhere else in this forum that a minute per .030 of material was a rough number. Based on what you said it seems less than that.

I am going to be heat treating 1084, 1/8. Based on my math above I was thinking it would be about 4 mins. Sounds like it may be less - I guess I just need to see what the rebound time of the oven is?

Thanks!
Michael
 
My comment wasn't a particula;ar recipe. It was a general statement about not needing a pre-soak at 1200°F.

Different steels have different soak times. It varies on what the alloying is.
1084 is a eutectoid steel and requires only enough soak time to assure complete austenitization. 4-5 minutes would be plenty for 1084. Other steels require 10-15 minutes, and some high alloy stainless steels even more.
 
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