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Rockwell Hardness Conversion: B to C
6

Rockwell Hardness Conversion: B to C

Rockwell Hardness Conversion: B to C

(OP)
I have a material that is HRB 60.  I know this material is too soft for my application.  I have another material that I would like to use that is HRC 60.  All the conversion charts I've seen do not list a conversion between B and C that starts as low as HRB 60 (they start at about HRB 100).  How can I compare apples to apples?  i.e. How can I convert an HRC 60 to an HRB value?

RE: Rockwell Hardness Conversion: B to C

At a hardness of HRB 60, the HRC test method is invalid.  It's out of range.  If you performed an HRC test on the material, you would likely get a reading of "0".

RE: Rockwell Hardness Conversion: B to C

(OP)
Understood.  So how can I compare the two materials, then?  How can I know how much harder (even a rough ballpark) HRC 60 is than HRB 60?

RE: Rockwell Hardness Conversion: B to C

amoncur,

   Look around.  You should be able to find a chart showing hardness conversions.  I am looking at my old metalurgy book from college.

   For steel, Rockwell B60 is equivalent to a tensile strength of 55,000psi.  Rockwell C60 is equivalent to something over 300,000psi.

               JHG

RE: Rockwell Hardness Conversion: B to C

3
There is a hardness conversion calculator built into the freeware unit conversion program Uconeer. It can be freely downloaded from the link in my signature below. Disclaimer: I am the author of Uconeer.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Rockwell Hardness Conversion: B to C

Katmar,

I have a little problem with your Uconeer, which nonetheless I find handy and very useful:
Can't perform conversion from 60 HRC to tensile strength, as if this upper threshold were out of acceptable range (it works up to 59.9 HRC).   

RE: Rockwell Hardness Conversion: B to C

2
There is nothing wrong with Uconeer in cutting the conversion table off at Rc 60 since the conversion to tensile strength is inexact and is based on using unadorned steel.   You will find in any literature that their conversion tables cut off at Rc 60 unless it is a conversion for a specific alloy under specific conditions.

Also under most conditions of routine testing Rc 59.5 and Rc 60 are the same entity.  You also find that the reliability of the conversion from one scale to another falls off or subject to interpretation at the extremes.

Checkout the site linked below and download "Fundamentals of Rockwell Hardness Testing"

http://www.wilsoninstruments.com/en/literature-library



 

RE: Rockwell Hardness Conversion: B to C

unclesyd,

Thanks for your post, anyway I have probably been misunderstood (damn, English is not my native language). I was not questioning the fact that the upper limit is established in 60 HRC, but rather that despite of the fact this value seems to be regarded by Uconeer as an accessible value for conversion (HRC range from 1.7 to 60.0), the program does not allow to perform any conversion from 60 HRC to any tensile strength. It seems the upper limit taken into by Uconeer is 59.9 HRC (instead of the reported 60 HRC). So I was only trying to advice about a small,  minute, even trivial bug to the author of the program (maybe this is not the most opportune site).  

RE: Rockwell Hardness Conversion: B to C

ione, thanks for bringing this to my attention.  I understood that you were only saying "the product should do what it says on the box" - and I agree with that. Although UncleSyd is correct that within normal hardness testing accuracy there probably isn't a significant difference between Rc 59.9 and 60.0 it is not good that Uconeer shows that the allowable range for Rc to tensile is 1.7 to 60.0 but it will not work when you enter 60.0.  I used Vickers as the master scale when setting up this converter - i.e. to convert from Rc to Tensile it actually converts from Rc to Vickers and then from Vickers to Tensile.  This reduced the number of internal conversion routines required from 276 to 23, but causes some rounding errors.  All bug reports are appreciated.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Rockwell Hardness Conversion: B to C

Katmar,

I absolutely didn't mean to complaint about Uconeer, nor to say "the product should do what it says on the box" as it is for free, and so I am not entitled to say this.
Probably I should have sent you a private e-mail and not use a public forum (my apologies for this). As I underlined in my previous post I do use frequently your program and find it very useful. You've definitely done a great job, even more appreciated as you distributed it for free.
 

RE: Rockwell Hardness Conversion: B to C

katmar:

I wondered who wrote Uconeer...I use it frequently.

Good job, thanks on behalf of society for your contribution to knowledge.

 

Regards,

SNORGY.

RE: Rockwell Hardness Conversion: B to C

Nice little program.  I've been using convert.exe which is not as complete.  However, one thing it does have is a custom conversion where the user can add their own conversions.  I have Oersteds to A/m in mine.  You might want to consider that functionality.  Also, under the mass flow could you add g/min?  We use that constantly while our customers mainly use lb/hr.

RE: Rockwell Hardness Conversion: B to C

Just a thought, if you want to compare the hardness why not use a Vickers test?

RE: Rockwell Hardness Conversion: B to C

(OP)
Is there a way to use the Vickers scale to compare my two known Rockwell hardnesses?  I don't have access to test equipment, I'd just like to gauge the relative difference in hardness between the two.

RE: Rockwell Hardness Conversion: B to C

@amoncur - yes, HRB 60 = Vickers 110 and HRC 60 = Vickers 698 (per Uconeer)

@ione - I could see that you meant no offense, and I took none.

@SNORGY - thanks

@dgallup - thanks. There are so many things I would like to add, and many that are requested by the users, but there is so little time. One day...

RE: Rockwell Hardness Conversion: B to C

Getting back to the subject in original post, ASTM E140 gives standard hardness conversion tables, as well as equations for conversion between scales.

RE: Rockwell Hardness Conversion: B to C

60 HRC = 653 Brinell
65.7 HRB = 111 Brinell
That's as low as the scale goes on the one I found.

I don't know about linearity, so here are a few more:
100 HRB = 241 Brinell
90 HRB = 183 "
72 HRB = 126 "

so 10 pts HRB = 58 pts Brinell, and 18 pts HRB = 57 pts Brinell. . .  Oops! it's not linear.

But as a ballpark guesstimate, the 60 HRB would be mid-80's to upper 90's Brinell.

RE: Rockwell Hardness Conversion: B to C

The bottom line is you are making a HUGE change in hardness, do you really want to make such a big change?

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