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Brinell Hardness to Rockwell Hardness Conversion Chart
Here’s the comprehensive Brinell Hardness to Rockwell Hardness Conversion Table specifically tailored for the plastic injection mold industry for your reference.
Injection Mold Industry: Brinell Hardness to Rockwell Hardness Conversion & Tensile Strength Reference chart
(Based on ASTM E140, ISO 18265 Standards – Applicable to Tool Steels & Mold Materials)
| Brinell Hardness (HBW) 3000kg, 10mm WC Ball | Rockwell A (HRA)60kg Brale | Rockwell B (HRB)100kg 1/16″ Ball | Rockwell C (HRC)150kg Brale | Tensile Strength (Approx.)ksi (×1000 psi) | Typical Mold Applications | Testing Guidelines |
| 85-100 | – | 52-60 | – | 35-45 | Aluminum mold frames (6061-T6) | HRB only, avoid ultra-low loads |
| 101-120 | – | 60-72 | – | 45-55 | Copper alloy inserts | Baseline for pre-hardening |
| 121-150 | – | 72-88 | – | 55-75 | Annealed H13 die casting molds | Specify HRB range clearly |
| 151-180 | 42.1-51.3 | 88-100 (Max) | – | 75-90 | P20 pre-hardened steel (28-32HRC equiv.) | Switch to HRC near upper HRB limits |
| 181-210 | 51.3-58.5 | – | – | 90-105 | 4140 mold base plates | Prefer HRA scale |
| 211-240 | 58.5-63.7 | – | 12.0-22.0 | 105-120 | NAK80 mirror polish steel | Verify tempering curve for HRC conversion |
| 241-270 | 63.7-67.8 | – | 22.0-29.0 | 120-140 | S7 shock-resistant steel | Avoid HBW on nitrided layers |
| 271-300 | 67.8-71.2 | – | 29.0-34.0 | 140-160 | Quenched H13 (un-tempered) | Maintain ≥3× indent spacing |
| 301-330 | 71.2-74.0 | – | 34.0-38.0 | 160-180 | D2 cold work tool steel | Report per ASTM E10 |
| 331-360 | 74.0-76.3 | – | 38.0-42.0 | 180-200 | M2 high-speed steel (54-56HRC equiv.) | Use tungsten carbide balls |
| 361-390 | 76.3-78.3 | – | 42.0-45.0 | 200-220 | Tungsten carbide inserts (WC-Co) | Conversion error increases above 400HBW |
| 391-420 | 78.3-80.0 | – | 45.0-48.0 | 220-240 | PM steels (e.g., ASP23) | Require metallographic verification |
| 421-450 | 80.0-81.6 | – | 48.0-51.0 | 240-260 | Cryo-treated molds | Lab-grade equipment only |
| 451-480 | 81.6-83.0 | – | 51.0-54.0 | 260-280 | Ceramic coating substrates (HV≥1500) | Test on polished surfaces |
| 481-510 | 83.0-84.3 | – | 54.0-56.0 | 280-300 | WC ejector pins (93%WC) | Multi-directional testing for anisotropy |
| 511-540 | 84.3-85.5 | – | 56.0-58.0 | 300-320 | Diamond coating substrates | Direct HRC measurement recommended |
| 541-600 | 85.5-88.0 | – | 58.0-63.0 | 320-370 | Industrial tungsten carbide (ISO K20) | Use HRA/HV above 600HBW |
Technical Notes
Conversion Formulas (ASTM E140 approximations)
- HRC ≈ (HBW – 100)/6 (Valid for 200-600HBW range)
- HRA ≈ 0.1 × HBW + 45 (Valid for 300-700HBW range)
Key Mold Steel Ranges
- P20 Pre-hardened: 290-330HBW ↔ 28-34HRC
- H13 Quenched & Tempered: 340-380HBW ↔ 38-42HRC
- S136 Stainless: 320-360HBW ↔ 35-40HRC
Tensile Strength Estimation
- Tensile Strength (ksi) ≈ 0.5 × HBW (±10% error for ferrous metals)
Testing Standards
- ASTM E10: Sample thickness ≥8× indent depth for Brinell tests
- ISO 6508: Mandatory calibration with standard blocks for Rockwell
Load-Specific Brinell Correction Factors |
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| Actual Test Load (kgf) | Conversion Factor to 3000kg | Applicable Materials |
| 500 | ×1.12 | Aluminum, copper alloys |
| 1000 | ×1.05 | Pre-hardened mold steels (≤35HRC) |
| 3000 (Standard) | ×1.00 | Tool steels, carbides |
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