HRC what does it really mean?

[bubblewhip]

The rockwell hardness on knives have always confused me. I mean 4116 can be hardened to 58-59 rockwell and so can S30V. But we all know S30V blows the crap out of 4116 at the same hardness. I heard it's an indicator of heat treating but Scrapyard knives says a steel heat treated to 58-59 HRC in one hour isn't as good as a steel heat treated to 58-59 in 3 days. So what gives? Whats the use of HRC because it doesn't seem to indicate wear resistance, toughness, or stain resistance?

I heard that steels and HRC are also directly related to tensile strength can anyone confirm that?

 

[MORIMOTOM]

it is only one indicator of a steel's properties, and there are several that are relevant.

relative hardness will also be a contributing factor regarding other properties.

 

[FlaMtnBkr]

It does give an indicator of toughness and wear resistance. Especially when comparing one steel against itself at different hardness'. You can't assume that every steel at 60 HRC is going to behave the same, you need to know the steel's properties. But S30V hardened to 57 HRC is going to be more tough and less wear resistant than if it is hardened to 62. If you look at steels with similar compositions like low alloy carbon steels then you can make a better comparison than if you were comparing that to a highly alloyed stainless steel.

There is a whole science based on steel, what its alloyed with, and how its heat treated so it is not simple. But you can derive some information and an idea of how a steel will perform by it's hardness.

 

[tiguy7]

There are two things going on with wear resistance. One is the rigidity of the grain structure (its resistance to deformation). This is what the Rockwell tester measures. A little diamond pyramid is pressed into the surface of the steel with a known force. The farther it travels, the softer the steel. The other factor is inclusions. If your soft blade is loaded with tiny hard bits like Vanadium carbide (82HRC), the blade will have wear resistance that the tester can't measure. The pyramid pushes the hard stuff out of the way. If you add small hard stones to concrete, it increases its wear resistance.

 

[Blop]

The rockwell hardness on knives have always confused me. I mean 4116 can be hardened to 58-59 rockwell and so can S30V.

Yes, it can, but who does?

But we all know S30V blows the crap out of 4116 at the same hardness.

Does it? Have you found a comparision test? I would like to see it. Show me the link please!

Most of the times, blades, made from 1.4116 are tempered down to HRC 56 - 57. If there was a blade of this steel that hard, i would be very interested in.

I heard it's an indicator of heat treating but Scrapyard knives says a steel heat treated to 58-59 HRC in one hour isn't as good as a steel heat treated to 58-59 in 3 days.

You must be really into heat treating, to know, why Scrapyard needs a long heat treatment. But HRC is not an indicator for the heat treating process.

So what gives? Whats the use of HRC because it doesn't seem to indicate wear resistance, toughness, or stain resistance?

It indicates hardness. But have a look at the steel datas from Crucible Steels about 154CM. You see, how different a HRC 60 can be.

Most edges from high alloyed steel grades (that are what is offerd to 95%, like 154CM, S30V, 440C, and so on) benefit from a higher hardness. Just my personal experience. The + in toughness in that steel grades is minor.

The range of hardness advertised, can indicate how well the heat treating process is controlled. The closer the hardness range, the better. But that, can´t stand alone. To judge from the hardenss information to the edge quality misses first hand consumer information.

I don´t want to miss the hardness information.

 

[Gator97]

HRC was under impression that HRC was Hardness on Rockwell scale C.
There are A, B and C scales of Rockwell hadrness and the one used for steels used in knives is C scale.

Also, when I was researching carbides, I've tried to find hardness of some of the common and important ones in the alloys. E.g. Vanadium carbide.
What I found was that carbide hardness is not measured in HRC at all, but on a different scale system. Various sources on the net cite anything from 80HRC to 92HRC for Vanadium carbides, that included articles from knives magazine and other resources.
Rockwell C scale for the record goes to 69...
Hardness conversion calculators exist, but the results are not always consistent or you get infinity or invalid operand error.