newb question about hardness

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mjolnirman

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Jan 15, 2008
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What's the difference between hardness from steel and hardness from heat treat? ie, if a 420c blade were heat treated to 60 rc, and a s30v blade were heat treated to 60 rc, what would the difference be?
 
Difference would be in the wear resistance, I would think. Hard is hard, but how long will the edge hold up in use is the question.

--nathan
 
mjolnirman said:
...if a 420c blade were heat treated to 60 rc, and a s30v blade were heat treated to 60 rc, what would the difference be?
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I'm not an expert, but I would expect the wear resistance and brittleness to be different.

I might as well give a specific example of this. One claim to fame of INFI steel I've heard is that it can be made quite hard without becoming prone to edge chipping.
 
so does wear resistance correlate with edge holding? i always believed harder meant sharper, longer edge, but more brittle and prone to breaking/chipping. I gotta take a material science class.
 
It's all basically up to person doing the heat treat. You for instance could heat treat a piece of steel to 60 and it would be hard, but very brittle, whereas I (just for instance :D) could heat treat the same piece of steel to 60, but because I know what i'm doing more than you, my blade will last much longer edgewise than yours.

One would think 60RC is 60RC.

Anyone can hardnen something, not everyone knows how to make a TOUGH as well as hard blade. :D
 
that makes sense, well the next question then, a little off topic: is the 420hc on the buck sbmf any good? since it's heat treated by paul bos.
 
The 420hc is better than the other 420 steels but not a great steel. Remember that hardness only tells you of part of the story.Don't rate blades by hardness alone !!
 
its alright for stainless I think

rockwell hardness is just how easy it can be centre punched, not edge holding or strength.
 
A simple example of comparing hardness in two materials is steel and glass. Both are about equally hard.....But would you want to drive a nail with a glass hammer?????

There are several factors that are used to evaluate steel. Final hardness is not really an issue with any knife blade steel ,as they all can attain a Rc of greater than 60. They are usually tempered to a final Rc of between 54 and 62, depending on the use of the blade, and the steel chosen. The main properties that are needed are Wear Resistance, and Toughness ( there are several others, but those are the main points).
Wear resistance is the ability to resist the edge wearing down in use (getting dull) , Toughness is the ability to resist damage due to the stresses applied to the blade in use (chipping and breaking).What you are looking for is a steel that has a spot on its HT chart where the two meet at a level that is desirable for the use intended.Scalpel blades can be very hard and super sharp,but are brittle and break easily. Swords are very tough and not so hard and sharp. Most knives are a compromise between the two extremes. Planning the HT and picking the right steel are what knife blade metallurgy are all about.
Stacy
 
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