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Using the Rockwell Hardness Test for Metal Applications

Tag Archive: hardness conversion table

  1. Using the Rockwell Hardness Test for Metal Applications

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    A metal’s hardness indicates its resistance to permanent shape changes when a compressive force is applied. Naturally, it is an important characteristic, and measuring hardness enables a manufacturer to choose an appropriate material for an application.

    There are various methods (such as Rockwell, Brinell, and Vickers) for measuring metal hardness. Of these, the simplest and most cost effective is the Rockwell hardness test, which involves applying a specific load on the material using an indenter and measuring how far the indenter penetrates.

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    Why do manufacturers run hardness tests?

    Manufacturers leverage metal hardness tests to determine the material’s tensile strength, elasticity, and plasticity.

    These factors indicate its resistance or susceptibility to mechanical wear and tear for different applications.

    Metals must often withstand pressure or extreme temperature during its application use, and hardness testing is an ideal way to determine whether the component can perform.

    Because of this, hardness testing is often critical during quality control. Knowing a material’s hardness can also help judge whether additional strengthening measures such as heat treatment are required.

    Being the most cost-effective method, the Rockwell Hardness test is widely employed for measuring indentation hardness.

    How it works

    The Rockwell Hardness test uses a conical diamond or a hard steel ball as an indenter. Initially, a minor load is applied on the metal to be tested. This force is to allow the indenter to penetrate the material surface, thus eliminating any errors causes by surface roughness.

    An additional major force is then applied for a predetermined period and then reduced to minor load state. The difference in indenter position before and after the application of the major load is measured. This is the permanent deformation caused by the major load.

    The Rockwell hardness scale, which combines multiple test loads and indenter types, allow the user to judge the hardness of the material using the permanent deformation readings.

    Use cases

    Manufacturers can also use hardness testing to eliminate secondary processes.

    One example involved ESI’s client, who was encountering a problem with their metal stamped part. Given the soft steel being used, the part needed to be heat treated and plated. Plating the material, however, caused the parts to become entangled during packing and shipping.

    ESI employed the Rockwell method to identify a new stainless steel of appropriate hardness where the entire tempering and plating process could be eliminated.

    This substitution allowed the client to eliminate the trouble associated with shipping, and simultaneously allowed the manufacturing process to be shortened and streamlined.

    ESI provides a conversion table for anyone using the Rockwell, Brinell or Vickers methods for assessing material hardness. This table can save an engineer’s time, and help assess material qualities such as hardness and approximate tensile strength of the material being tested.

    Get your free copy of the hardness conversion table by clicking here or on the link below.

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  2. Rockwell, Brinell, and Vickers Metal Hardness Tests: What’s the Difference?

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    Completing a hardness test is a critical step in qualifying metal parts; these tests determine the various properties of a specific metal, such as resistance to wear, toughness, and formability.

    rockwell brinell vickersDifferent test scales were created to assist engineers in selecting the appropriate metals and hardness for their specific application.

    To help you understand the different test scales we’ve created a cross-reference table for three of the most popular hardness tests below.

    Brinell Hardness Test

    The first widely used standardized hardness test, the Brinell method determines the indentation hardness of metal materials and is typically used for materials with a coarse surface or a surface too rough to be tested through other methods.

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    The Brinell test is not useful for fully hardened steel or other hard materials, however, and often leaves a large impression on the metal. The Brinell test is also very slow.

    The Brinell test is not useful for fully hardened steel or other hard materials, however, and often leaves a large impression on the metal. The Brinell test is also very slow.

    Rockwell Hardness Test

    Developed to provide a less destructive alternative to the Brinell test, this differential-depth method eliminates the errors associated with mechanical imperfections.

    Quicker and cheaper than the Brinell and Vickers tests, the Rockwell test requires no material prep, and hardness value is easily readable without any extra equipment, making this one of the most commonly used methods of measuring metal hardness.

    Vickers Hardness Test

    Making use of a diamond indenter, the Vickers hardness test is done with less force and more accuracy than the Brinell test. By magnifying the surface of a metal, this test can target specific microstructural constituents like martensite or bainite, or assess the quality of heat treating or surface hardening operations.

    Requiring an optical system and material prep, the Vickers test incurs higher costs and takes longer to complete than the Rockwell test.

    Selecting the Right Hardness Test for Your Application

    To assist you in understanding the most popular test scales, ESI has created a free Hardness Conversion Table, with approximate tensile strength in PSI and MPa as well as groupings of approximate fastener property classes compiled in one easy-to-read guide.

    Convert Hardness Measurements  Download your free copy of the table >>