What is a Hardness Tester?
A hardness tester is a device used to measure the hardness of materials, typically metals, by assessing their resistance to deformation. Hardness reference specimens, or standard specimens, play a crucial role in ensuring the accuracy of these measurements. They are test pieces with known hardness values used to calibrate and verify the performance of hardness testers.
Application of Hardness Testers
Hardness testing is critical in the metal manufacturing process, particularly in evaluating the effectiveness of heat treatments. It serves as a non-destructive quality control measure, offering insights into material properties such as tensile strength without the need for more costly and time-consuming tests. Hardness tests are essential for ensuring the desired mechanical properties in heat-treated parts and other components requiring specific hardness levels.
Principle of Hardness Testers
To maintain reliability, hardness testers must exhibit minimal hardness variation and remain stable over time. Materials like SKS3, SK85, C2600P, S10C, and S45C are commonly used.
Importance of Hardness Testers
Hardness testers offer a practical and economical alternative to direct strength tests in confirming material qualities. It is particularly useful for surface hardness measurements, where the minor marks left by the test can be easily removed in subsequent machining processes. Hardness is typically measured by the size of an indentation left by a defined indenter under a specific load, with results calibrated against known reference values.
Key Points in Hardness Testing
While hardness testers provide a range rather than an absolute value of hardness, they are indispensable for calibrating testers to ensure consistent and accurate measurements. These specimens undergo thorough heat treatment to prevent changes in hardness over time, although repeated use near previous indentations is discouraged to avoid work-hardening effects. The lifespan of a hardness tester is limited by the number of tests it can undergo before affecting its reliability.