Difference Between Brinell and Rockwell Hardness

Hardness is a measurement of a material’s resistance to deformation or indentation. It is an important characteristic in engineering and manufacturing applications since it establishes if a material is appropriate for a given task. The Brinell and Rockwell hardness tests are two of the many techniques used to gauge a material’s hardness. We shall examine how these two approaches vary in this essay.

What is Brinell Hardness?

The relationship between the applied force and the print’s surface is known as Brinell hardness (HBW). An indenter is a hard metal ball that leaves an impression on the material’s surface layers by applying force. It has a diameter of D. The ball’s standard diameters are 10 mm, 5 mm, 2.5 mm, and 1 mm.

A print of the shape of the cubic diameter of the base diameter dB and the depth hB is produced by imprinting the test material. The impulse force used by the Brinell hardness meter ranges from 9.807N to 29420N, depending on the test material and the impeller ball’s diameter.

When evaluating steel or steel-based materials, the load is typically applied for 10 to 15 seconds, whereas for softer materials, the weight must be applied for at least 30 seconds. To ensure the measurement is as accurate as possible and to establish the diameter of the calotte’s bowl, the topic to be examined must be cleansed, defatted, and have a flat surface.

There cannot be any vibration during the measurement since this could improperly affect the measured hardness levels. Brinell’s hardness is a size without dimensions. Brinell’s ball leaves the largest and deepest imprint when compared to other methods of hardness testing, deforming the surface in both a practical and aesthetic sense (assuming the product is being tested for hardness rather than a sample).

What is Rockwell Hardness?

Rockwell’s approach, in contrast to Brinell’s and Vickers’, measures the depth of the indenter’s penetration rather than the size of the imprint. For this reason, the Rockwell hardness is measured after it has been released on the hardness scale.

A diamond stem or an acacia ball is used to make inductors. The ball diameters are 1/16′′ and 1/8′′, while the stem diamonds have a peak angle of 1200 and a round radius of 0.2mm. Hardwoods and commonly heat-treated materials are tested using the HRC (cone) method, while soft and medium hard metals are tested using the HRB (ball) method.

Hardness according to the Rockwell’s method is 1e=0.002m because the total penetration depth of the indenters, which can be divided into 100 parts for the HRC method and 130 parts for the HRB method, is 0.2mm (HRC) or 0.26mm (HRB). The HRC method uses an indenter in the shape of a diamond trunk that is loaded for 3 seconds with pre-load F0=98.07 N to establish a baseline from which to evaluate penetration depth.

When the primary load F1 is removed and backfilling occurs because of the material’s elasticity, the total load F is created by adding the main load F1=1373N for a duration of 4 seconds. The amount of hardness determines the depth to which the indenter will penetrate. The same measurement principle applies to the HRB method, except the steel ball is imprinted with either a preload of F0=98.07N or a main load of F1=882.6N, resulting in a total load of F=980.7N.

Differences: Brinell and Rockwell Hardness

The Brinell and Rockwell hardness tests are not exactly the same. The kind of indenter utilized is one of the biggest variances. While the Rockwell test employs either a diamond cone or a hardened steel ball, the Brinell test uses a hardened steel ball. The material being tested and the level of precision required influence the indenter choice. The hardened steel ball is typically used for softer materials, whereas the diamond cone is typically utilized for harder materials.

The way in which the two tests are measured differs between them as well. The Brinell test measures the indentation’s diameter, whereas the Rockwell test gauges its depth. Since measuring an indentation’s diameter might be more difficult than measuring its depth, this may have an impact on the accuracy of the results.

The two tests also employ different measuring units. While the Rockwell hardness number is represented in arbitrary units (HRA, HRB, etc.), the Brinell hardness number is expressed in kilograms per square millimeter (kg/mm2). This may make comparing the findings of the two tests more challenging.

The two examinations have different testing methodologies as well. The Rockwell test involves providing an initial force followed by a secondary force, whereas the Brinell test requires applying a steady force for a predetermined amount of time. The use of two forces can increase the number of variables in the test, which can have an impact on the accuracy of the results.

And lastly, different materials can be examined using the two approaches. Aluminum, copper, and brass are examples of softer materials that respond better to the Brinell test. Contrarily, the Rockwell test is more appropriate for tougher materials like steel and titanium.

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Conclusion

In conclusion, both the Brinell and Rockwell hardness tests are widely used methods for measuring the hardness of materials. They differ in the type of indenter used, the method of measurement, the units of measurement, the testing procedures, and the materials that can be tested.

Choosing the right test for a specific application depends on the material being tested, the desired level of precision, and the availability of equipment. It is essential to select the appropriate method to ensure accurate and reliable results.

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