Units of Measure for Case Hardness such as HV, HRB, HRC, etc.

[Eusoof]

Anybody know why we should use too many unit measurement for hardness such as HV, HRB, HRC and etc. Should we need have one standard only? Anybody know the exactly method to measure the hardness? Refer to file attachment, please comment...or you have any idea the exactly where it's a point i need measure to make the data more reliable.

 

[CarolX]

Re: Units of Measure for Case Hardness

Anybody know why we should use too many unit measurement for hardness such as HV, HRB, HRC and etc. Should we need have one standard only? Anybody know the exactly method to measure the hardness? Refer to file attachment, please comment...or you have any idea the exactly where it's a point i need measure to make the data more reliable.

HR - Hardness, Vickers Scale

HRB - Hardness, Rockwell B-scale

HRC - Hardness, Rockwell C-scale

These are not different units of measurement, but different scales.

I don't know much about Vickers.

Rockwell has a different set of hardness scales based on the desired hardness. In other words, you switch scales as you move to harder material.

I can't tell from your file attachemnt what you are trying to accomplish - the resolution in the pictures is too low to read.

 

[Jim Wynne]

Re: Units of Measure for Case Hardness

HR - Hardness, Vickers Scale

The "R" in "HR" stands for Rockwell. Use of the Vickers scale is usually denoted "HV."

For the OP, different scales and methods are generally used for different applications, but like everything else, even the people who specify material hardness are sometimes confused about the standards. There's some pretty good general information on hardness measurement here.

 

[SteelMaiden]

I only have experience using a Rockwell tester, so my knowledge is limited. There are many hardness tests some of them are: Rockwell (standard and superficial, many scales), Vickers, Knoop, Shore, Brinell, and maybe others. The selection of the proper test would be dependent upon the type of material you are testing, and also the hardness. For example, a rockwell b scale uses a steel ball indenter, while the c scale uses a diamond indenter. Your test type would also depend on what your customers are asking for. Back when I was working in the lab, some of our customers asked for Brinell values, but allowed us to convert our Rockwell value to Brinell.

Can you provide us a little more information on what you are looking for?

 

[harry]

Eusoof, I hope you don't mind if we ask you to do a search for I remember coming across posts on:
1. Conversion/correlation table for the various type of scales
2. Preferred surface/area for conducting your test

 

[Kevin H]

Looking for a case hardness implies a carburizing or other surface treatment of steel (possibly nitriding), where the hardness differs based on the distance from the surface. Case depth is going to be measured in thousandths of an inch in the US. The hardness scales to use for hardness in the case would be either Vickers or Knoop - both microscopic scales. Even the superficial Rockwell scales would measure on too macroscopic a scale to accurately measure hardness in the case. Depending on the base steel, Rockwell B or Rockwell C could be used to measure the hardness of the core material. A typical grade for case hardening in the US would be 8620.

Typical specifications I've seen in the past for carburized steels specify a minimum hardness at a given case depth, and a minimum hardness for the core material as well. Sometimes there are microstructure requirements as well, or minimum surface carbon contents.

Once you have measured a Vickers or Knoop hardness, there are conversion tables available to "convert" the microhardness to an equivalent macroscopic hardness values such as Rockwell C, Rockwell B, Brinell, etc. with caveats as to the accuracy of the conversion.

One uses different hardness measurements depending on customer and specification requirements, the nature of the material being tested - iron, copper, aluminum, hardened/unhardened, macroscopic vs. microscopic requirements, thickness of material being tested, etc.

There are 6 Rockwell superficial hardness scales (15, 30, & 45 N and 15, 30, & 45 T) about 9 macroscopic Rockwell scales (C, B, A, D, E, F, G, H, & K) a different penetrator and different load for each one - 1/16 " tungsten carbide ball, 1/8" tungsten carbide ball, & diamond pyramid indenter with loads of 60, 100, & 150 kg. I don't do the microscopic ones often enough to remember, and Brineel hardness parallels macroscopic Rockwell - different indenters, different loads, etc. There are also unique hardness measurements - Scleroscope comes to mind - rebounded ball method used mostly to measure surface hardness of rolls such as those used to flat roll steel.

Hope the above ramble helps some.

 

[bakhtiar - 2009]

Hello,

Is there anyone could help me to get the specification of HRB for electrogalvanized steel thickness 0.8mm.

Thank you

 

[prototyper]

Hello,

Is there anyone could help me to get the specification of HRB for electrogalvanized steel thickness 0.8mm.

Thank you

What grade of steel?

The hardness varies considerably with the type and grade. You would need to specify the type of steel (chemical composition, hot or cold rolled, yield and tensile strength, or a specific code for the steel grade such as En, BS, ASTM, SAE, etc.