Hardness is an important property in manufacturing steel and other metallic materials. Manufacturing standards and specification documents establish common requirements for materials and services, enabling suppliers to compete more effectively in a global market. Manufacturers should be able to reference them easily from a single source to facilitate the adoption of these standards. The Brinell Hardness Test is one of the popular methods used to measure the hardness of metals. This method is used to inspect materials that have a rough surface, and other methods cannot be used. This article is an ASTM Brinell Hardness Standard Test Reference Guide.
I. Importance of Brinell Hardness Standard Test
Important details regarding the structure and quality of materials, including their tensile strength, wear resistance, elasticity, and other physical qualities, can be learned via the Brinell indentation test. Brinell hardness testing is normally used as a quality control test after material thickness and hardness before it goes into the manufacturing process. This test is used in automobile, aerospace, electronic and high-precision components.
II. Principles of Brinell Hardness Test
The Brinell hardness test works under two stages. The indenter is brought into contact with the test sample in the first step, and the indenter is then subjected to a certain amount of force. After a predetermined dwell period, the force is applied and then released. The indent diameter is measured in at least two perpendicular directions in the following step. The Brinell hardness test is calculated using the measurements and the mathematical method.
The hardness testing equipment is designed to stop any movement of the test sample during measurement. The hardness testing machine’s anvil should be clean and debris-free. The tungsten carbide balls with the required diameters from the ASTM standards are the indenters used to carry out the Brinell hardness test.
The hardness testing machine should have a measurement device as standard equipment, or it might be a separate device. A microscope is typically employed as a measuring device.
III. Test Requirements
- To perform the Brinell hardness test, only tungsten carbide ball indenters with the necessary diameters should be used.
- The test component needs to be clean and free of debris, grease, and other foreign objects for proper results.
- You should check the indenters and test apparatus frequently to guarantee authentic and reliable test results.
- The machines should be verified following ASTM requirements using the proper testing blocks.
- The symbol HBW should be placed after the Brinell hardness numbers, and an index describing the testing conditions should be added.
IV. Test Specimen
- Any standard does not specify the test sample’s size or form.
- The test piece shouldn’t have any bulges or marks on the side or opposite of the indentation that would indicate the impact of the indenter’s force. At least ten times the size of the depression should be the thickness of the test sample.
- The test sample’s minimum width must meet ASTM standards to meet the requirements for indentation spacing.
- The test sample’s surface should be machined, polished, and filed with an abrasive material to accurately measure the indent’s diameter. The test sample should be prepared to minimize any surface changes brought on by machining or heating.
V. Test Procedure
- The indent diameter should be at least 24 to 60% of the indenting ball diameter.
- The testing machine should be operated under standardized conditions, and applicable safety precautions must be followed.
- There should be no vibration, shock, or overshoot when the indenter is in contact with the test sample.
- One to eight seconds is the required dwell time for the first force. It is okay to apply force more quickly when the results are ineffective. Apply the subsequent force for 10 to 15 seconds. The applied force should be released after the dwell period without shock or vibration.
- Two directions that are 90° perpendicular to one another are used to measure the indents. When required, additional measurements of the indent might be taken.
- The difference between the largest and smallest measurement while taking measures on a level surface shouldn’t be greater than 0.1mm.
- The Brinell hardness test should be performed between 10 and 35 °C of ambient temperature. The tester needs to be cautious with temperature variations because they could affect the results.
VI. ASTM Standards
Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
Practice of Calibration of Force-Measurement Instruments for verifying the Force Indication of Testing Machines.
Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb Hardness.
Test Method for Knoop and Vickers Hardness of Materials.
VI. ISO Standards
Conformity Assessment and General Requirements for Accreditation Bodies Accrediting Conformity Assessment Bodies
General Requirement for the Competence of Calibration and Testing
The Brinell hardness test was developed by the American Henry Brinell, who created the first tester in 1873. This is a widely accepted method in the field. The ASTM’s Brinell hardness test standard is used by alloy and metal suppliers and users, and it’s a basic requirement for all hardness testing equipment. This kind of hardness testing is used to measure the hardness and toughness of metallic materials. This test determines the amount of indentation you will see in the indentation gauge when you press the test piece onto it. The hardness testing machine has an anvil pressed against the test piece, and an indent is made as the tester presses down on it. Several industrial documents and standards use the Brinell hardness test, including ASTM standards for automotive parts, chemical analysis standards, consumer product standards, and aerospace industry standards.