Heatreating and Rockwell?

aquatimer

aquatimer

Joined
May 10, 1999
Messages
208

If you Rockwell a blade at a certain spot,and the blade has not been differentialy heat treated,does that mean the entire blade has the same Rockwell as the spot tested?
If your A2 blade Rockwells at 61HC,and thats what Rockwell you wanted,does that guarantee that the blade has been heat treated correctly?.
Thanx,
John R.


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You'd have to check it in at least two places for an accurate RC hardness. I wouldn't reccoment trying to differential heat treat A2, though. Air hardening steels don't react well to it, from my understanding.

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Oz

"When your work speaks for itself, don't interrupt."
- Henry J. Kaiser
 
John; Others may disagree with me, but, I feel strongly that the answer to your question is "no". Correct or desired Rockwell hardness does not address the microstructure of the steel at all, it only indicates the hardness at the spot tested. so, it is possible to heat treat two pieces of the same steel differently, and end up with the same hardness, although one piece might have better toughness and edge holding than the other. That's right, more toughness AND more edge holding (wear resistance). This has lots to do with the steel's response to the heat treat cycle it was subject to, and how the alloying additions reacted to the process.
What you can be pretty sure of, is if you test a blade twice, and get the same hardness value, that the whole piece is probably the same hardness. I test the thickest section, as it is likely to be the softest part.

RJ Martin
 
In addition to my knives..... I heat treat manufacturing tooling on a daily basis. I have to agree with what RJ Martin said above to the letter!!
The only thing I would add is that when I use the larger "industrial" size ovens at work, I get more consistent Rc measurements than that with the small "knifemakers" ovens. I think this has to do with more even heating and air circulation.
Neil

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http://www.geocities.com/Eureka/Meeting/5520/index.html


 
i agree with the above also....Rc only tells you that your steel is a certain hardness.. however...if you followed the h/t profile properly and have good equipment and accurate gages...you call feel confident that you are on the money....but thats no guarantee.....the pounders give it the true test of death to make sure they did it right.

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http://www.mayoknives.com


 
I agree with RJ . The thickest section will be the softest most often. You may want to use this a reference for the future. If you grind the blade in a simular way and find that the edge is just the way you want it ... then most often it will be the same if you did everything the same way you did it when you got the reading on the thicker section.


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