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Relation between vickers and rockwell hardness

  1. Apr 25, 2006 #1
    I am doing my university project about the relation between vickers and rockwell hardness. I know that there is not a mathematical relation but I need to find a good approximation. I have practice both tests in more than 50 specimens (HV70-HV950) and I have more than 300 (HV1,HR1),(HV2,HR2),... points. Any idea how to find the relation? I have done some graphics and got their ecuation with excel but how can I know which is the best one, because I have more than seven different equations (logaritmic, polinomical, exponentials,...). Sorry about my english thanks
     
  2. jcsd
  3. Apr 25, 2006 #2

    Astronuc

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    Staff: Mentor

    The conversion will depend on the material (hard or soft) somewhat.

    Hard - http://www.gordonengland.co.uk/hardness/hardness_conversion_2c.htm
    Soft - http://www.gordonengland.co.uk/hardness/hardness_conversion_3c.htm

    Or

    http://www.hardnesstesters.com/hardness-conversion-high.htm
    http://www.hardnesstesters.com/hardness-conversion-low.htm

    Hardness conversion calculator - http://www.tribology-abc.com/calculators/hardness.htm
    Standard Hardness Conversion for metals acc. ASTM E 140 - 97, September 1999, Conversion for Non-Austenitic Steels, Table 1.

    A nice overview of hardness testing on steels - http://www.key-to-steel.com/Articles/Art140.htm
     
  4. Apr 27, 2006 #3
    I need the formula

    Sorry did not express correctly. The aim of my project is to find the formula that links vickers and rockwell (example: HR=a(HV)^2+b(HV)+c). I have done tests using steel Which goes from HV170 to HV900. My question is: How can I get that formula using the values I got in my test?
    Thanks for your interest Astronuc
     
  5. Apr 27, 2006 #4

    Astronuc

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    Staff: Mentor

    borja, in your case, you could use the data provided in the links I provided and do a best fit between HV and appropriate HR data, and then apply that equation to your HV data to get the corresponding HR values.

    Otherwise, you would have to do both Vickers and Rockwell tests on the same specimens, and from that develop a correlation as you mention.
     
  6. Jun 2, 2006 #5
    renting prize

    thank you very much for the information. I have already finished the investigation and I am doing the quote. I want to take in count all the expenses and I vave been trying to find how much costs to rent a vickers and rockwell hardness testers. I have sendt some e-mails to canadian and french companies but They didn`t answer to me. Does anybody know it?
    Thanks
     
  7. Jun 11, 2006 #6

    Astronuc

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    Staff: Mentor

    I think one has to rely on the companies, since they are the one's who will give the quote (price). I have not heard of someone renting a hardness tester.

    It seems that most academic and industrial labs buy such equipment.

    Perhaps one could contact US and/or Japanese manufacturers as well.
     
  8. Aug 2, 2006 #7

    dng

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    Hi borja, have you found a formula for this conversion? Of course a polynomial equation could be the easier way to fit the data. I am also working with this conversion. I have used conversion tables but I had some discrepancies. Did you compare your results with these conversion tables?
    Thank you and regards
     
  9. Sep 19, 2006 #8
    Dear Dng,
    Polynomial conversion is the easiest way for doing it, but I have found a better one:

    HV = 7091,843768 / (125,6010596- HRB)
    HV = 1974914,439/ (102,9783872- HRC)2 ---------- 20 < HRC < 40
    HV = 15936,2268 / (79,13859914– HRC) ---------- HRC > 40


    I have compared my results with conversion tables and I had very good results. Try this way and send a reply please, so I can know if it suits correctly with other values.
     
    Last edited: Sep 20, 2006
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