Steel Hardness Testing Methods: HRC, HB, HV Guide

What Is Hardness?

Hardness is the resistance of a material to plastic deformation or penetration by an indenter. In the steel industry, hardness testing is the most fundamental and rapid method of material quality control. The hardness value is directly related to other mechanical properties such as tensile strength and wear resistance.

Frequently Asked Questions

What Is Rockwell Hardness (HRC/HRB)?

The Rockwell method is the most common and fastest hardness testing method. It measures how deeply an indenter penetrates the material under a specified load.

HRC (Rockwell C):

• Indenter: Diamond cone (120° angle)
• Load: 150 kgf (preliminary load 10 kgf)
• Measurement range: 20-70 HRC
• Application: Hardened steels, quenched and tempered parts
• Typical values: Quenched and tempered steel 28-35 HRC, tool steel 58-65 HRC

HRB (Rockwell B):

• Indenter: 1/16" steel ball
• Load: 100 kgf
• Measurement range: 20-100 HRB
• Application: Soft steels, copper alloys

What Is Brinell Hardness (HB/HBW)?

The Brinell method is based on measuring the diameter of the impression created by pressing a large hard ball into the material surface.

• Indenter: Tungsten carbide ball (typically 10 mm)
• Load: 3000 kgf (for steel), 500/750 kgf (soft metals)
• Measurement range: 80-650 HBW
• Formula: HB = 2F / (πD × (D - √(D²-d²)))

Advantages:

• Reliable results in inhomogeneous structures due to large impression area
• Ideal for cast iron, forged parts
• Widely referenced in industrial standards

Disadvantages:

• Long measurement time (impression diameter read by microscope)
• Cannot be applied to very hard materials (>650 HB)
• Specimen surface must be flat and smooth

What Is Vickers Hardness (HV)?

The Vickers method uses a 136° diamond pyramid indenter for measurement.

• Indenter: Diamond square pyramid (136° included angle between opposite faces)
• Load: 1-120 kgf (micro: 10-1000 gf)
• Measurement range: 10-2500 HV (no theoretical limit)
• Formula: HV = 1.8544 × F / d²

Advantages:

• Single scale measurement across the entire hardness range
• Micro-hardness measurement capability (thin layers, case depth)
• Load-independent result (geometric similarity)

Disadvantages:

• Surface preparation required (polishing)
• Microscopic impression measurement is time-consuming
• Not suitable for field measurement

Should I Use Brinell or Rockwell?

Selection criteria:

Situation	Recommended Method
Hardened steel (>30 HRC)	Rockwell C (HRC)
Normalized/annealed steel	Brinell (HBW)
Thin layers/coatings	Vickers (HV)
Field measurement	Rockwell (fast results)
Cast iron	Brinell
Quality control (serial)	Rockwell
Research & development	Vickers

What Is the Relationship Between Hardness and Tensile Strength?

Approximate conversion formulas for carbon and low-alloy steels:

• Rm (MPa) ≈ 3.45 × HB (valid for Brinell 120-450)
• Rm (MPa) ≈ 3.30 × HV (Vickers equivalent)

Examples:

• 200 HB → ~690 MPa tensile strength
• 300 HB → ~1035 MPa tensile strength

These are approximate formulas; for exact values, refer to the material certificate.

How to Convert Between Hardness Scales?

Inter-scale conversion is non-linear and based on empirical tables. Key reference standards:

• ASTM E140: Hardness conversion tables
• ISO 18265: Hardness conversion for metallic materials

Common equivalents (approximate):

HRC	HB (approx.)	HV (approx.)	Rm (MPa)
20	226	238	780
25	253	266	870
30	286	302	990
35	321	340	1110
40	363	382	1250
45	409	432	1410
50	460	484	1590

For quick and accurate conversion, we recommend using our Hardness Converter tool.

How to Minimize Measurement Errors?

• Specimen thickness should be at least 10 times the indentation depth
• Surface should be smooth and parallel
• Spacing between measurement points should be at least 3 times the indentation diameter
• Distance from edge should be at least 2.5 times the indentation diameter
• Measurement should be performed on a vibration-free, stable platform
• Instrument calibration must be current

Aktif Çelik Quality Assurance

At Aktif Çelik, hardness values of all steel bars we supply are documented in 3.1 certificates. Brinell hardness testing is applied as standard on all our hot-rolled products. We collaborate with accredited laboratories for additional hardness tests (HRC, HV) and mechanical tests required by our customers. You can use our tool for converting hardness values indicated in your material certificate between different scales.