Nitro V Heat Treat Problem

M

Marc Cooper

Joined
Apr 7, 2019
Messages
60
Hey All

I am having trouble with heat treating Nitro V steel. I'm using an Evenheat KO 22.5 Kiln that seems to work fine for other steels.

Here is my process for 5/32 thick blades that are wrapped in stainless foil:

Step 1: Preheat the steel at 1500 degrees for 15 minutes.

Step 2: Ramp up as fast as possible to 1950 degrees and let it stay at that temp for 15 minutes.

Step 3: Remove from oven and plate quench with 2x 3/4" thick aluminum plates til cool.

Step 4: I had then planned to soak in Liquid Nitrogen for an hour and 2x temper at 400 degrees.

I don't even get to step 4 because after Step 3 it is clear the Nitro V is not hard. I don't get to the liquid nitrogen step as the steel isn't close to the planned 63HRC once I'm done with the plate quench. My HRC tester is calibrated almost perfectly and I'm not even reaching a 50HRC 5-point average.

Anyone know what I'm doing wrong?
 
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I don't use NitroV but I believe you should go to step 4, do the nitrogen treatment and then do the hardness measurement. It is possible that you have only 50HRc because you have a lot of austenite retained, the passage in nitrogen converts it increasing the hardness. 50HRc is really low, wait for answer from Larrin or even from some friend who uses NitroV
 
Don’t know why knifemakers are so obsessed with testing hardness before cryo. Get it in the cryo right after quenching. The retained austenite is stabilizing quickly. The retained austenite reduces the as-quenched hardness.
 
With the thickness of steel we are typically are working with, I don't think you need to stick your blade in at 1500 and keep it in there until it reaches 1950, that's a lot of time in the oven.

Read the AEB-L and Nitro V sections in Knifesteelnerds.com. It's packed with nuggets.:thumbsup:

I have heat treated Nitro V like AEB-L with good results. I wrap in SS foil, do a 10 min. soak at 1750 then quench between plates, let the oven heat to 1975 then put the blade in for 15 min then plate quench again. Straight into LN for 1 hr and then temper at 325. I've been getting RC62 consistently with this routine.
Good luck!
 
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I think I will try the following:

Let it soak at 1950 for 20 minutes instead of 15 then straight to the liquid nitrogen. I'm thinking an extra 5 minutes should ensure full penetration and not promote too much grain growth.

I'll let you all know how it works out.
 
Marc Cooper said:
I think I will try the following:

Let it soak at 1950 for 20 minutes instead of 15 then straight to the liquid nitrogen. I'm thinking an extra 5 minutes should ensure full penetration and not promote too much grain growth.

I'll let you all know how it works out.
Click to expand...
Increasing time from 15 min to 20 min isn't the problem though.


I feel you should check hardness after the first temper and be sure to surface the steel down with a fresh 120 grit belt or higher without getting hot grinding.
Also make sure the test area is flat, any warping will give an incorrect reading.
Steels like Nitro V get harder with tempering and should stay in the 300f-350f range for best results.
 
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