Hardness Conversion Table for Carbon and Alloy Steels

Brinell Testing is a fairly simple test but the most destructive type. It requires more sample preparation and can at times require destruction of a finished part. A defined load of 500-kg to 3000-kg is applied through a 10 mm hardened steel ball indenter and the subsequent impression is measured. A Brinell number is then assigned to that measurement. Brinell numbers are unique to the process and do not have units assigned.

Rockwell Testing again requires application of various loads to a variety of indenters to achieve again a reading of resistance to penetration through depth measurement. The Rockwell test is simpler to run and requires less sample preparation and minimal damage to finish parts. The Rockwell testing machine calculates the penetration and gives the unique hardness number. This number also has no units.

Harder materials require heavier loads and harder indenters. Tungsten Carbide indenters for Brinell and diamond indenters for Rockwell are used. Small loads are used for thinner materials making Rockwell A and N and T type hardness more reliable for sheet and tube. They are also better suited to softer materials like Aluminum as well.

It is possible to convert hardness to Tensile Strength and this is shown in the chart. It is best used on hardened steel products as accuracy is better. This same conversion cannot be used for Yield Strength. Tensile Strength is shown in KSI which stands for 1000 pounds per square inch (psi). Also shown is the metric version of strength which is in MPa (Mega Pascal) or N/mm2 (Newton per millimeter squared)

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