Brinell to Vickers

How Do You Convert Brinell to Vickers?

Brinell (HBW) and Vickers (HV) hardness values are approximately equal for hardnesses below about 350, diverging at higher values where Vickers readings become progressively larger. The approximate relationship is HV = HBW x 1.05 for soft-to-medium materials, with increasing divergence above 350 HBW. ASTM E140 provides the definitive conversion table. At 200 HBW, Vickers reads about 210 HV. At 400 HBW, Vickers reads about 420 HV. At 600 HBW, Vickers reads about 700 HV or more. Both tests create indentations — Brinell uses a 10mm ball, Vickers uses a diamond pyramid — and both measure the resulting impression to calculate hardness. The tests often agree well on softer materials because the ball and pyramid indenters create similar stress fields. At higher hardnesses, the Vickers diamond pyramid does not deform (unlike the Brinell ball), so Vickers readings remain accurate while Brinell readings may become unreliable. Metallurgists converting between these scales are typically working with quality data from different testing labs, historical records, or specifications written in one scale when the available equipment uses the other.

How to Convert Brinell to Vickers

1. Start with the Brinell hardness value (HBW).
2. For HBW under 350, multiply by approximately 1.05 for a rough HV estimate.
3. For HBW above 350, the relationship diverges — use the ASTM E140 table.
4. ASTM E140 reference points: 150 HBW = 157 HV, 250 HBW = 263 HV, 350 HBW = 372 HV, 450 HBW = 481 HV.
5. For precision work, always refer to ASTM E140 rather than an approximation formula.

Real-World Examples

History of Brinell and Vickers

The Brinell test (1900) predates the Vickers test (1921) by two decades. When the Vickers test was introduced, one of its immediate advantages was the ability to test very hard materials that deformed the Brinell ball. Researchers quickly established empirical correlations between the two scales. The near-equality of HBW and HV for soft materials is not a coincidence — both tests measure resistance to plastic deformation, and at low hardness levels, the geometry of the indenter matters less. At higher hardnesses, the Vickers pyramid's sharper geometry concentrates stress differently than the Brinell ball, causing the scales to diverge. The ASTM E140 standard captures these empirical relationships in tables that have been refined over decades of inter-laboratory comparisons.

Common Mistakes to Avoid

• Assuming HBW and HV are always numerically equal. They are close at low values but diverge significantly above 350. At 600 HBW, the Vickers equivalent may be 700 HV or more.
• Using the approximate factor (1.05) for very hard materials. Above 400-450 HBW, the factor increases and the linear approximation breaks down. Use the ASTM E140 table.
• Comparing Brinell results from different test loads. Standard Brinell for steel is 3000 kgf with a 10mm ball (HBW 10/3000). Other load-ball combinations produce different numbers. Ensure the test conditions match before converting.
• Treating a micro-Vickers reading as interchangeable with a macro-Brinell value without considering indentation size effects. Fine surface layers and gradients can make the two numbers diverge even on the same part.

Frequently Asked Questions