🔩 Brinell Hardness

Construction PN-EN ISO 6506-1

Overview

STATUS (as of 28.10.2026). PN-EN ISO 6506-1:2014-12 — Polish version, published 12.08.2016, implements EN ISO 6506-1:2014 and ISO 6506-1:2014 [IDT]; it replaced PN-EN ISO 6506-1:2008. The standard is current — no withdrawal note; a new edition (prEN ISO 6506-1) is in preparation.

SCOPE AND PRINCIPLE (clauses 1, 3). The standard specifies the Brinell hardness test of metallic materials with stationary and portable hardness testing machines; for some materials and products there are specific standards, e.g. ISO 4498 for sintered metal materials. The indenter — a hardmetal ball of diameter D — is forced into the surface of the test piece, and after removal of the force F the diameter of the indentation d is measured. The hardness is proportional to the quotient of the force and the curved surface area of the indentation, which is calculated from the mean diameter of the indentation and the ball diameter, assuming that the indentation takes the shape of the unloaded ball.

FORMULA AND DESIGNATION (clause 4). HBW = 0.102 × 2F / [π · D² · (1 − √(1 − d²/D²))], where F is in N, D and d in mm, d — the mean of two diameters measured approximately at right angles; 0.102 ≈ 1/9.806 65 (conversion from kgf to N). Example designation: 600 HBW 1/30/20 — 600 is the hardness, 1 — the ball diameter in mm, 30 — the approximate equivalent of the force in kgf (30 kgf = 294.2 N), 20 — the duration of the test force in s, given only when it lies outside 10–15 s. The former symbols HB and HBS referred to steel balls, which the standard no longer permits.

FORCES AND BALLS (7.3–7.4, Tables 2–3). Combinations from Table 2 are used: balls of 10, 5, 2.5 and 1 mm at a force-diameter ratio 0.102 × F/D² of 30, 15 (10 mm ball only), 10, 5, 2.5 or 1 — forces from 9.807 N (HBW 1/1) to 29 420 N (HBW 10/3000); other forces only by special agreement. The force is chosen so that the diameter of the indentation lies between 0.24·D and 0.6·D; outside these limits the ratio d/D is stated in the test report. The ball should be as large as possible so as to cover the largest representative area of the test piece. Recommended ratios: steel, nickel and titanium alloys — 30; cast iron — 10 below 140 HBW and 30 from 140 HBW (cast iron only with 2.5, 5 or 10 mm balls); copper and copper alloys — 5 (< 35 HBW), 10 (35–200 HBW), 30 (> 200 HBW); light metals — 2.5 or 5 (< 35), 10 or 15 (35–80), 10 or 15 (> 80); lead and tin — 1; sintered metals — according to ISO 4498.

TEST PIECE (clause 6). The surface smooth and even, free from oxide scale, foreign matter and, in particular, lubricants, with a finish that permits accurate measurement of the indentation; with small balls polishing or lapping may be needed. The preparation must not alter the surface, e.g. by excessive heating or cold working. The thickness of the test piece — at least eight times the depth of the indentation (not the diameter); minimum thicknesses depending on the indentation diameter are given in Annex B, and a visible deformation on the underside of the test piece shows that it is too thin.

TIMES AND CONDITIONS (7.1, 7.6–7.8). The test is normally carried out at ambient temperature 10–35 °C; the laboratory may narrow the range, e.g. to (23 ± 5) °C. The indenter is brought into contact with the surface and the force is applied perpendicularly, without shock, vibration or overload — the method has no preliminary force. The force application time is 7 s with a tolerance of +1/−5 s (2–8 s), and the full force is maintained for 14 s with a tolerance of +1/−4 s (10–15 s); a longer time when the material requires it, with a tolerance of ± 2 s. Distance of the centre of the indentation from the edge — at least 2.5 times the mean indentation diameter; distance between the centres of adjacent indentations — at least 3 diameters.

RESULT AND UNCERTAINTY (7.10, clauses 8–9). The hardness is calculated from the formula and rounded to three significant figures, or read from the tables of ISO 6506-4. The standard states explicitly that there is no general process of accurately converting Brinell hardness into other hardness scales or into tensile strength — when converting, its basis and method must be stated. The uncertainty is estimated from direct calibration or from indirect verification with hardness reference blocks (guidance in Annex C).

WHAT WE DO NOT GIVE HERE. The content of Annexes A (verification of the testing machine before the test), B (table of minimum thicknesses) and C (uncertainty) and the requirements for machines and indenters from ISO 6506-2 — we only know their purpose. The standard does not require a specific number of indentations on the test piece.

Method principle

A polished hardmetal ball of diameter D (10, 5, 2.5 or 1 mm) is forced perpendicularly into a smooth metal surface with a force F from Table 2 of the standard: the force is applied over 2–8 s and maintained for 10–15 s. After removal of the force, the diameter of the indentation is measured in two directions approximately at right angles and their mean d is taken.

Brinell hardness HBW = 0.102 × 2F / [π · D² · (1 − √(1 − d²/D²))] — the force related to the curved surface area of the indentation — is rounded to three significant figures and recorded with the test conditions, e.g. 600 HBW 1/30/20. The force is chosen so that d lies between 0.24·D and 0.6·D.

Applications

• Hardness of metallic materials — steel, nickel and titanium alloys, cast iron, copper and copper alloys, light metals, lead and tin (recommended force-diameter ratios according to Table 3 of the standard)
• Measurements with stationary and portable hardness testing machines
• Sintered metal materials — according to the specific standard ISO 4498, which refers to PN-EN ISO 6506-1
• Materials requiring a longer duration of the test force — the time is given in the designation, with a tolerance of ± 2 s

Key parameters

Standard

Standard number

PN-EN ISO 6506-1:2014-12

Title (PL)

Metale — Pomiar twardości sposobem Brinella — Część 1: Metoda badania

Title (EN)

Metallic materials — Brinell hardness test — Part 1: Test method

Step-by-step procedure

1. Preparation of the test piece

   Surface smooth and even, free from scale, foreign matter and lubricants; with small balls, polishing or lapping if necessary. Do not overheat or cold-work the surface. Thickness at least 8 times the indentation depth (Annex B) (clause 6).

2. Verification of the testing machine

   Before the test, confirm that the verification according to Annex A of the standard has been carried out (7.2).

3. Choice of ball and force

   A combination from Table 2; the ratio 0.102 × F/D² according to the material and hardness from Table 3 (e.g. steel 30); the ball as large as possible; the indentation should be 0.24·D–0.6·D (7.3–7.4).

4. Positioning the test piece

   The test piece on a rigid, clean support, lying stably and not moving; the machine protected from shock and vibration (7.5, 7.7). Temperature normally 10–35 °C (7.1).

   🌡 Temperature: 10–35 °C

5. Making the indentation

   Bring the indenter into contact and apply the force perpendicularly, without shock, vibration or overload: application 2–8 s, duration 10–15 s (longer only if the material requires it, ± 2 s) (7.6).

6. Spacing of indentations

   Centre of the indentation at least 2.5·d from the edge; centres of adjacent indentations at least 3·d apart (7.8).

7. Measuring the indentation

   With a manual system — two diameters approximately at right angles, arithmetic mean; on a ground surface measurement at approx. 45° to the grinding direction is recommended. With an automatic system — also validated algorithms (more measurements, projected area of the indentation) (7.9).

8. Calculation and test report

   HBW from the formula (or from the tables of ISO 6506-4), rounded to three significant figures. Test report: reference to the standard, identification of the test piece, date, temperature if outside 10–35 °C, ratio d/D if outside 0.24–0.60, the result in HBW designation, basis and method of any conversion to another scale, occurrences that may have affected the result (7.10, clause 9).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard contains no safety requirements — the rules for working with the hardness testing machine are set by the laboratory on the basis of a risk assessment and the manufacturer's instructions
• While the force is being applied, do not hold the test piece in your hand or put your fingers in the indenter zone

Frequently asked questions