Brinell to Rockwell C Hardness Converter
HB
Enter Brinell value above
Note: Conversions are approximate based on ASTM A370 standards. Valid range: 76-800 HB. Results below 154 HB do not have direct HRC equivalents.
Quick Conversions
Popular Brinell to HRC Conversions
| Brinell (HB) | Rockwell C (HRC) | Vickers (HV) | Tensile Strength (N/mm²) |
|---|---|---|---|
| 800 | 72 | – | ~2500 |
| 760 | 70 | – | ~2400 |
| 711 | 65 | – | ~2250 |
| 681 | 63 | – | ~2150 |
| 642 | 61 | – | ~2050 |
| 601 | 58 | 746 | ~1950 |
| 552 | 55 | 649 | ~1800 |
| 504 | 52 | 549 | ~1650 |
| 469 | 50 | 505 | ~1550 |
| 456 | 48 | 490 | 1569 |
| 419 | 45 | 448 | 1447 |
| 402 | 43 | 424 | 1390 |
| 375 | 41 | 393 | 1314 |
| 348 | 38 | 361 | 1187 |
| 322 | 35 | 332 | 1089 |
| 300 | 32 | 303 | 1020 |
| 277 | 30 | 285 | 971 |
| 250 | 25 | 255 | 853 |
| 229 | 21 | 235 | 775 |
| 212 | 18 | 218 | 706 |
| 199 | 15 | 199 | 667 |
| 180 | 10 | 180 | 608 |
| 167 | 6 | 172 | 555 |
| 154 | 1 | 152 | 515 |
Conversion Formula & Steps
Approximate Conversion Formula:
For HB values between 240-800:
HRC ≈ (HB – 104.2) / 10.08
For HB values below 240, refer to the standard conversion table as the relationship becomes non-linear.
For HB values between 240-800:
HRC ≈ (HB – 104.2) / 10.08
For HB values below 240, refer to the standard conversion table as the relationship becomes non-linear.
Conversion Steps
- Identify your Brinell value: Measure or obtain the BHN/HB reading from your material test results.
- Check the valid range: HRC conversions apply to hardened steels, typically HB values above 154.
- Apply conversion: Use the conversion table or formula to find the corresponding HRC value.
- Verify accuracy: Cross-reference with ASTM A370 standards for precision-critical applications.
- Consider material properties: Different steel compositions may yield slightly different results.
Brinell vs Rockwell C: Key Differences
Brinell Method (HB/BHN)
Indenter: 10mm tungsten carbide ball
Load: 3000 kg (29,400 N)
Duration: 10-15 seconds
Measurement: Diameter of indentation
Range: 76-800 HB
Best For: Large, coarse materials
Load: 3000 kg (29,400 N)
Duration: 10-15 seconds
Measurement: Diameter of indentation
Range: 76-800 HB
Best For: Large, coarse materials
Rockwell C Method (HRC)
Indenter: 120° diamond cone (Brale)
Load: 150 kg (1,471 N)
Duration: 2-6 seconds
Measurement: Depth of indentation
Range: 1-72 HRC
Best For: Hardened steels, fast results
Load: 150 kg (1,471 N)
Duration: 2-6 seconds
Measurement: Depth of indentation
Range: 1-72 HRC
Best For: Hardened steels, fast results
Accuracy Considerations
Brinell tests provide more reliable results for non-uniform materials due to larger indentation area. Rockwell C tests are faster and leave smaller marks, making them ideal for finished products or thin materials.
Material Damage
Rockwell C creates minimal surface damage with shallow indents (0.1-0.2mm depth). Brinell produces larger, more visible indentations (2-6mm diameter), which may affect finished surfaces or small components.
Applications in Metalworking
- Steel Manufacturing: Quality control for heat-treated steel components, verifying proper hardening processes and material strength specifications.
- Automotive Industry: Testing engine components, crankshafts, camshafts, and gears to meet strict durability and wear resistance requirements.
- Aerospace Engineering: Validating landing gear components, turbine blades, and structural elements where precise hardness values are critical for safety.
- Construction Equipment: Assessing bucket teeth, track links, and wear plates to predict service life under extreme operating conditions.
- Tool Manufacturing: Evaluating cutting tools, dies, and punches to achieve optimal balance between hardness and toughness.
- Oil & Gas: Testing drill bits, valve components, and pipeline materials exposed to high-pressure, high-temperature environments.
- Quality Assurance: Converting between hardness scales when specifications require different testing methods or when comparing historical data.
- Material Selection: Choosing appropriate steel grades based on hardness requirements for specific mechanical applications.
Hardness Testing Methods Explained
Brinell Hardness Test
The Brinell test applies a 10mm diameter tungsten carbide ball under a 3000 kg load to the material surface for 10-15 seconds. The resulting circular indentation’s diameter is measured using a microscope, and the Brinell Hardness Number (BHN) is calculated by dividing the applied load by the indentation’s surface area. This method excels at testing coarse-grained materials like castings and forgings because the larger indentation averages out microstructural variations.
Rockwell C Hardness Test
Rockwell C testing employs a 120° diamond cone indenter (Brale penetrator) with a 150 kg major load. The test applies a minor preload of 10 kg, then adds the major load, and measures the permanent depth increase after removing the major load while maintaining the minor load. This depth measurement directly converts to an HRC value on a dial or digital display, providing results within seconds. The shallow indentation makes it suitable for finished parts and production testing.
Why Conversion is Approximate
Each hardness scale measures different material properties: Brinell assesses resistance to penetration over a larger area, while Rockwell C measures elastic recovery and penetration depth. These fundamental differences mean no exact mathematical relationship exists between the scales. Conversion tables are developed through extensive empirical testing of various steel grades, providing reliable approximations for most applications but cannot account for all material variations, heat treatment processes, and microstructural differences.
Heat Treatment Hardness Ranges
| Heat Treatment Condition | Tensile Strength (N/mm²) | Brinell Range (HB) | Typical HRC Equivalent |
|---|---|---|---|
| Annealed | 400-550 | 110-160 | N/A (Use HRB) |
| Normalized | 550-700 | 140-200 | N/A – 17 |
| Condition Q | 625-775 | 179-229 | 10-21 |
| Condition R | 700-850 | 201-255 | 17-26 |
| Condition S | 775-925 | 223-277 | 20-30 |
| Condition T | 850-1000 | 248-302 | 23-33 |
| Condition U | 925-1075 | 269-331 | 28-36 |
| Condition V | 1000-1150 | 293-352 | 32-38 |
| Condition W | 1075-1225 | 311-375 | 34-41 |
| Condition X | 1150-1300 | 345-401 | 37-43 |
| Maximum Hardened | 1550+ | 444+ | 47-52 |
Frequently Asked Questions
What is the formula to convert Brinell to HRC?
+
There is no single precise formula due to the different testing principles. For approximate conversion of hardened steel (HB 240-800), the relationship HRC ≈ (HB – 104.2) / 10.08 provides reasonable estimates. Below HB 240, use standardized conversion tables based on ASTM A370 empirical data for better accuracy.
Can all Brinell values be converted to HRC?
+
No. The Rockwell C scale is designed for hardened materials and typically covers HB values from approximately 154 to 800. Softer materials (below 154 HB) should use the Rockwell B scale (HRB) instead, which employs a ball indenter rather than a diamond cone.
Which hardness test is more accurate?
+
Brinell testing is generally considered more accurate for heterogeneous materials and castings because the larger indentation (2-6mm) averages out microstructural variations. Rockwell C offers faster results and repeatability for uniform, hardened materials. The choice depends on material type, sample size, and application requirements.
Why do conversion tables show approximate values?
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Each hardness scale measures different material responses: Brinell measures resistance to plastic deformation over a large area, while Rockwell C measures elastic recovery and penetration depth. Material composition, heat treatment, and microstructure affect these properties differently, making exact conversion impossible. Conversion tables represent average values from extensive testing.
What is the hardest value on each scale?
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For steel materials, practical maximum values are approximately 800 HB (Brinell) and 72 HRC (Rockwell C). Specialized tool steels and carbides can reach these levels after proper heat treatment. Exceeding 65 HRC (approximately 711 HB) typically indicates fully hardened steel with extreme wear resistance but reduced toughness.
How does material thickness affect hardness testing?
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Brinell testing requires material thickness at least 10 times the indentation depth (typically 6-8mm minimum). Rockwell C needs only 10 times the indentation depth (approximately 1-2mm minimum). Thinner materials should use superficial Rockwell scales or Vickers testing to avoid anvil effects that produce artificially high readings.
Can hardness values predict tensile strength?
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Yes, for steel, an approximate relationship exists: Tensile Strength (N/mm²) ≈ 3.4 × HB. This correlation is reasonably accurate for medium-carbon steels but varies with alloy composition and heat treatment. The relationship is less reliable for non-ferrous metals and should not replace actual tensile testing for critical applications.
Which industries use Brinell to HRC conversion most?
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Automotive, aerospace, tool manufacturing, and heavy equipment industries frequently convert between scales. Engineering specifications may require one scale while shop equipment supports another. Quality control departments use conversions when comparing supplier certifications, historical data, or international standards that specify different hardness scales.
References
- ASTM International. (2021). ASTM A370-21: Standard Test Methods and Definitions for Mechanical Testing of Steel Products. West Conshohocken, PA: ASTM International. https://www.astm.org/a0370-21.html
- ASTM International. (2017). ASTM E10-17: Standard Test Method for Brinell Hardness of Metallic Materials. West Conshohocken, PA: ASTM International. https://www.astm.org/e0010-17.html
- ASTM International. (2016). ASTM E18-16: Standard Test Methods for Rockwell Hardness of Metallic Materials. West Conshohocken, PA: ASTM International. https://www.astm.org/e0018-16.html
- ISO. (2015). ISO 6506-1:2014: Metallic materials – Brinell hardness test – Part 1: Test method. Geneva, Switzerland: International Organization for Standardization.
- ISO. (2015). ISO 6508-1:2015: Metallic materials – Rockwell hardness test – Part 1: Test method. Geneva, Switzerland: International Organization for Standardization.
- Boyer, H. E., & Gall, T. L. (Eds.). (1985). Metals Handbook, Desk Edition. Materials Park, OH: ASM International.