Hi everyone I have a simple question about heat treating but I don't know the answer. I am using nitro v and would like to know when to place the blank into the oven I was told to put it in about 1 minute before the oven reaches the required temp . Is this how you do it? Thank you
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Heat treat question
- Thread starter Wedgy
- Start date
A.McPherson
Knifemaker / Craftsman / Service Provider
- Joined
- Jan 27, 2012
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- 2,870
Do as
D
DevinT
says. You want the oven to have a chance to equalize before you stick your work in.
That way it's had a chance to really soak in the heat and when you open the door it will retain more heat so it doesn't have to work so hard to get the set temp back.
The harder it has to work, the more over temp your work will get, and obviously you want to avoid that.
That way it's had a chance to really soak in the heat and when you open the door it will retain more heat so it doesn't have to work so hard to get the set temp back.
The harder it has to work, the more over temp your work will get, and obviously you want to avoid that.
Sando
Knife Maker
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- Jul 4, 2002
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- 1,148
Yeah, I do the above pre-heat process. I have a programmable oven so here's my setup. Note, mine has an alarm that goes off 2 minutes before it times out. Let's just say I want 1,500 degrees for 5 minutes:
Program:
Step 1: 1,500 for 15 minutes (or whatever preheat time you like)
Step 2: 1,500 for 7 minutes
Process:
When the alarm for Step one goes off (that would be after 13 minutes), put the blade(s) in.
Press skip to go to Step two.
When the oven returns to 1,500 the second timer will start.
When the alarm for Step two goes off (that would be 5 minutes), take the blade(s) out and quench
I like doing this because the blade timer starts automatically after the temp is hit - I don't have to watch it. By having step two 2 minutes longer, I don't have to worry about the oven shutting off before I get there.
It works for me.
Program:
Step 1: 1,500 for 15 minutes (or whatever preheat time you like)
Step 2: 1,500 for 7 minutes
Process:
When the alarm for Step one goes off (that would be after 13 minutes), put the blade(s) in.
Press skip to go to Step two.
When the oven returns to 1,500 the second timer will start.
When the alarm for Step two goes off (that would be 5 minutes), take the blade(s) out and quench
I like doing this because the blade timer starts automatically after the temp is hit - I don't have to watch it. By having step two 2 minutes longer, I don't have to worry about the oven shutting off before I get there.
It works for me.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
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- Aug 20, 2004
- Messages
- 37,941
Just as an addition to the info provided:
The oven needs to be fully soaked so it is not just full of hot air but hot refractory. This takes from 15 minutes to half an hour. Just because the readout says the oven is at temperature does not mean it is ready for a blade yet.
The blade should go into the oven at the target temperature after the oven is soaked. By soaking the oven the temperature drops very little when opened. It may take only a minute or two to rebound in some cases.
The timer should be started when the oven returns to the target temp. In most cases a few minutes one way or the other won't matter. 8 minutes, 10 minutes, or 12 minutes at target will get the same results. Most soak times in the charts allow for some wiggle room.
You will see in some HT books a pre-heat step. This is often something like: "Pre-heat steel at 1500°F for 30 minutes and ramp to 1950°F .....".
This is not needed for knives. Our blades have simple geometry and go straight in the oven at the target. There are a few rare exceptions in some high alloy steels, but 99% of knife steels need no pre-soak at a lower temperature. Oddly shaped parts in industry is where this is used.
The oven needs to be fully soaked so it is not just full of hot air but hot refractory. This takes from 15 minutes to half an hour. Just because the readout says the oven is at temperature does not mean it is ready for a blade yet.
The blade should go into the oven at the target temperature after the oven is soaked. By soaking the oven the temperature drops very little when opened. It may take only a minute or two to rebound in some cases.
The timer should be started when the oven returns to the target temp. In most cases a few minutes one way or the other won't matter. 8 minutes, 10 minutes, or 12 minutes at target will get the same results. Most soak times in the charts allow for some wiggle room.
You will see in some HT books a pre-heat step. This is often something like: "Pre-heat steel at 1500°F for 30 minutes and ramp to 1950°F .....".
This is not needed for knives. Our blades have simple geometry and go straight in the oven at the target. There are a few rare exceptions in some high alloy steels, but 99% of knife steels need no pre-soak at a lower temperature. Oddly shaped parts in industry is where this is used.
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