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Thread: Question about hardness

  1. #1

    Question about hardness

    Guys,
    I am trying to remember how HRC scale scales? I remember it was not linear, but can't seem to able to dig any threads that mention what it was.
    Thanks

  2. #2

    Join Date
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    Not sure what you mean . Rockwell is a depth on penetration hardness test. On the C scale it is related to the depth of penetration of a hardened cone with a 150 kg load. The less penetration, the greater the hardness. As far as I remember it is linear within the scale.

    -AJ

  3. #3
    Like how the test is performed, or what the typical numbers for steel are?

  4. #4

  5. #5
    What I wanted to find out is what is the difference between two HRC values, for example 55 and 58? If I remember correctly it is not linear, I remember people posting it was either exponential increase or log increase, I am not sure if this was even correct. I was not able to find info on that online.

    Thanks

  6. #6
    It can be difficult to compare different measures of strength. You can get approximations though.

    Here's Rockwell vs Vickers hardness: http://www.gordonengland.co.uk/hardn...ell_c_conv.htm

    Vickers varies fairly linearly with tensile strength: http://www.gordonengland.co.uk/hardn...sion_chart.htm

    Also here's a conversion table: http://www.gordonengland.co.uk/hardn...version_2c.htm

  7. #7
    Thanks guys

  8. #8

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    55 to 58 hrc is a linear increase.

    -AJ

  9. #9
    Here's a graph I made based on the conversion chart:

    Uploaded with ImageShack.us

  10. #10
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    Quote Originally Posted by mainaman View Post
    What I wanted to find out is what is the difference between two HRC values, for example 55 and 58? If I remember correctly it is not linear, I remember people posting it was either exponential increase or log increase, I am not sure if this was even correct. I was not able to find info on that online.

    Thanks
    If I'm understanding correctly, to get a very hard rating, a material has to resist a large amount of force spread over a small area. As the depth of the penetration increases, the area over which the force is spread increases dramatically. In this sense, the rating is not linear with respect to pressure (force per unit area). It would seem that a 55-56 difference is much smaller than a 61-62 difference. I'm sure it's more complex than that but this reduction seems pretty intuitive.

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