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Brinell Hardness Number (HBW / BHN) Calculator — ASTM E10

Calculate the Brinell Hardness Number (HBW / BHN), indentation surface area, and estimated tensile strength using the official ASTM E10 / ISO 6506 formula.

🔩 Calculator Parameters
Calculated Results
Brinell Hardness Number (HBW)
—
kgf/mm² indentation resistance
Estimated Tensile Strength (UTS)
—
Approximate steel UTS (MPa)
Estimated Tensile Strength (ksi)
—
Imperial tensile strength
Spherical Indentation Area
—
Curved contact area (mm²)

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How to Use the Brinell Hardness Number (HBW / BHN) Calculator — ASTM E10

Introduced by Swedish metallurgist Johan August Brinell in 1900 and standardized under ASTM E10 and ISO 6506, the Brinell hardness test presses a precision tungsten carbide ball of diameter D (typically 10 mm) into a metal specimen under a controlled load P (typically 3,000 kgf for steels or 500 kgf for soft non-ferrous alloys) for 10 to 15 seconds.

Formula and Calculation Methodology

HBW = (2P ÷ (π D (D – √(D2 – d2))))
  • P: Applied test force in kilogram-force (kgf), where F(N) = P × 9.80665
  • D: Diameter of the tungsten carbide spherical indenter ball (typically 10 mm)
  • d: Mean diameter of the permanent circular impression left in the metal (mm)

Because the 10 mm spherical indenter creates a relatively large impression (typically 2.4 mm to 6.0 mm wide), Brinell testing averages out localized microstructural variations, making it ideal for coarse-grained castings, forgings, and structural steel plates. Furthermore, for carbon and alloy steels, multiplying the Brinell Hardness Number (HBW) by 3.45 provides a remarkably accurate non-destructive estimate of Ultimate Tensile Strength (UTS) in megapascals (MPa).

Typical Brinell Hardness (HBW 10/3000) & Tensile Strength of Engineering Metals

Material / AlloyIndentation d (mm)Brinell Hardness (HBW)Approx. Rockwell CTensile Strength (MPa)
6061-T6 Aluminum (500 kgf)2.52 mm95 HBWN/A (HRB 60)310 MPa
A36 Mild Structural Steel5.10 mm137 HBWN/A (HRB 75)475 MPa
AISI 1045 Normalized Steel4.30 mm197 HBW~13 HRC680 MPa
AISI 4140 Quenched & Tempered3.50 mm302 HBW~32 HRC1,040 MPa
AR400 Abrasion-Resistant Plate3.05 mm401 HBW~43 HRC1,380 MPa

Frequently Asked Questions

What does HBW mean compared to BHN?

Modern ASTM E10 and ISO 6506 standards mandate tungsten carbide balls—denoted ‘HBW’ (where W is the chemical symbol for Wolfram/Tungsten)—and have retired older steel ball indenters (‘HBS’ or ‘BHN’).

What is the valid indentation diameter range for a 10mm ball?

To maintain geometric similarity and accurate strain distribution under ASTM E10, the impression diameter d should fall between 0.24D and 0.60D (2.40 mm to 6.00 mm for a 10 mm ball).

How do I estimate steel tensile strength in PSI from Brinell Hardness?

Multiply the HBW value by 500 to get the approximate Ultimate Tensile Strength in pounds per square inch (PSI), or multiply by 3.45 to get MPa.

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