Why hardness matters

Measuring the hardness of metal is a critical step in the manufacturing process. Cross-industry recognised standards and accurate testing are vital not only for safety and efficiency but also to understand materials durability and stability in high-pressure conditions.

For more than a century the Brinell scale and hardness test have been widely used to determine the hardness value of steel, cast iron and aluminium components.

The challenges around building bespoke measurement systems fit for inspecting metalwork are multi-faceted. What is the importance of the Brinell method of testing and how do Somerset-based manufacturers of Brinell hardness testing equipment, Foundrax, ensure they get it right every time?

Brinell hardness test – a brief history

More than 100 years ago, engineer Johan August Brinell, created a formula and procedure for determining the hardness of a metal. Employed in the Swedish iron industry for more than fifty years, Brinell focussed on changes in the internal structure of steel as it was heated or cooled.

During the 1900 Paris Exposition, where talking films and escalators were seen for the first time, Brinell showcased his prototype hardness testing apparatus and formula, kick-starting these measurement tools as the first universally accurate methods of testing the hardness of materials.

While basic scratch tests originally determined materials’ (specifically minerals) hardness and were measured against Mohs scale, Brinell’s machine shed new light on determining the quality of manufactured materials.

He standardised the measurement of metal by pressing a steel ball into the surface of a specimen. He used a known load quantity to plastically deform (the permanent distortion occurring when a material is subjected to tensile, torsion or compressive stresses causing it to buckle or bend) the material. From this Brinell acquired data from which hardness could be calculated.

Further developments in measuring material hardness by Knoop, Rockwell and Vickers Ltd came about in the following decades. While each test expresses its results using a unique measurement, the empirical value of the Brinell method lies in the ability to test rough-surfaced, non-homogeneous components like iron and steel castings. Moreover, the ability to choose test forces and ball diameters, means it has a wide variety of applications.

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