How well do you know the specimen requirements for conducting a Brinell hardness test?
Hardness measurement is often peculiar to the test specimen or material, and certain specifications must be observed. These requirements often significantly affect the accuracy of the hardness measurement result. However, many hardness testing professionals still fall short when it comes to these requirements, which may result in errors during the Brinell test. Graciously, this article packs a lot of value as it gives you all the information you need concerning the specimen requirements for the Brinell hardness testing method.
I. Brinell Test
Considering the test specimen size and thickness when selecting an appropriate hardness test is critical. The Brinell hardness testing method is often the preferred method for coarse-grained surface specimens because it gives more accurate results for these categories of specimens. Yet, it requires using an optical instrument to correctly read and measure the indentation provided by the indenter on the application of the set load on the material surface. Furthermore, this test is standardized, which means the test procedures conform to standard specifications and documents like the ASTM E10 and ISO 6506 to ensure accuracy.
II. How to Carry out the Brinell Hardness Test?
To conduct a Brinell hardness test requires an indenter made from a hardened steel ball with a diameter of 10mm. The indenter applies a load range of 500kgf to 1,500kgf for soft materials but can apply as high as 3,000kgf for very large and thick materials. These loads are applied for 10 – 30 seconds, depending on whether the material is iron. By applying the load using a microscope, measuring the indentation on the material surface gives the impression diameter, which helps to calculate the Brinell hardness method. The Brinell hardness value formula is derived from the indentation’s surface area divided by the applied load.
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III. Specimen Requirements for the Brinell Test Method
Complying with specific specimen requirements is essential to carrying out the Brinell test. These requirements often involve specimen preparations and placement, including proper cleaning of the specimen support platform to ensure the specimen is parallel to the surface of the support. Though there is no need to polish the specimen’s surface high level due to its large indentation load, you must still ensure that the surface is relatively smooth, and the required level is adequate. However, you must ensure the specimen is adequately clamped to the support platform to avoid movement due to surrounding vibrations and shocks that can cause inaccurate hardness measurement results.
Related Article: What are the Specimen Requirements for the Rockwell Method?
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IV. What Surface Condition is Necessary for Brinell Test?
Though the surface of the specimen is often large in a Brinell test, and the impression made by the indentation is usually deep, there is still a need to prepare the surface before carrying out the test. The specimen preparation required for the Brinell hardness test can include machining, grindings, polishing, and lapping. However, the surface finish will not be as high as with the Vickers method, where no surface roughness can be tolerated.
V. What is the Minimum Thickness of the Specimen Required in the Brinell Hardness Test?
To ensure that the indentation does not puncture through the material surface, given that the Brinell method applies a large load for indentation, the applicable standards give certain thickness requirements. For instance, the ASTM standards specify that the specimen should have a minimum of ten times the indentation depth. Also, the ISO standards stipulate a minimum of eight times the indentation depth for the specimen thickness. These standards ensure that the load does not deform the specimen beyond measurable conditions.
VI. How Load is Applied to the Specimen in Brinell Hardness Test?
Load application for specimens in a Brinell test is often similar to popular methods like the Rockwell and Vickers hardness tests but differs from methods like the Leebs. Brinell test applies the loads directly to the specimen’s surface using a ball indenter with weights of 500kgf to 1,500kgf for softer materials and up to 3,000kgf for thicker materials. These loads are often applied for 10 to 15 seconds for softer materials and up to 30 seconds for thicker materials.
In conclusion, the Brinell hardness test methods have specimen requirements that contribute immensely to the accuracy of the test. These requirements include surface preparations like grinding and machining, which are often minimal due to the large size of the material and the loads applied. Also, the minimum thickness requirements specified by the relevant standards help to ensure that the load does not punch through the specimen during the loading stages. Ultimately, you want to carefully consider these requirements to ensure that you arrive at an accurate result for your Brinell hardness test.