What steps should companies consider to both speed up and tighten their Brinell hardness testing? In this article and the subsequent one I’ll set out the logical progression.
The accompanying image of multiple indentations makes something immediately clear: the Brinell indenting process moves material sideways as well as downwards. This raises a simple question — where, exactly, is the true edge of the indentation? An accurate answer is essential, because a difference of just 0.2mm on an indentation diameter can equal 20 hardness points on the Brinell scale.
The Brinell diameter measurement challenge plagued the test for many decades, tainting it somewhat with a ‘rough and ready’ reputation — acceptable for the workshop machinist, perhaps, but not for the laboratory.
Measurement is therefore the first thing to address when considering improvements to in-house Brinell testing, because it is the test’s weakness. There are a great many applications where tolerances are narrow, and disagreements between customers and suppliers are an obvious consequence. Some of our customers who supply the oil-tool industry, previously relying on manual microscopes, have confided that they’d been resorting to expensive third-party laboratories because customers were disputing their hardness figures. The reputational and financial consequences of such disputes are obvious.
There is also a more routine but equally costly risk. If a manual microscope is used to check raw materials at goods-in and an operator misreads the hardness, the error may not come to light until final machining — by which point considerable time and effort has been invested in a part that proves too hard or too soft for its intended application. Even where results are adequate, the business of taking every sample, manipulating the microscope into precisely the right position, and making the best possible estimate of diameter is time-consuming in itself. Automatic measurement therefore offers both greater accuracy and, almost certainly, significant cost savings.
The world’s first automatic measurement microscope reached the market over forty years ago. Extracting every last drop of performance from a 4K computer, it was capable of measuring the diameter of an indentation across more than 100 axes, calculating the mean, and determining the hardness in a split second. The system has been refined continuously ever since and remains the industry benchmark.
It can handle almost any surface irregularity, functions in any light, and warns operators of poor surface preparation. Even better: the user isn’t required to position the indentation centrally in the field of view or to align it with a graticule. The effect of this technology — we call it the BRINtronic — on the international standing of the Brinell test was transformative.
