The concept of material hardness
Hardness is a performance indicator that measures the softness and hardness of solid materials. Solid metal materials have hardness, while non-metallic solid materials also have hardness, and non-metallic solid materials also have hardness. Diamond has the highest hardness among all solid materials. For metal materials, hardness can sensitively reflect the differences in chemical composition, aroma structure, and heat treatment process of metal materials. In engineering and the mechanical and metallurgical industry, people can use simple hardness tests and empirical formulas to calculate the other thermodynamic properties and fracture characteristics of metal materials. In material research, hardness testing has also been widely used. Therefore, hardness testing has become one of the indispensable means for inspecting product quality, developing materials, and determining reasonable processing techniques.
Hardness actually refers to the resistance of a solid material surface to elastic deformation, plastic deformation, or hard cracking within a small or very small volume. Therefore, hardness is not a simple and definite physical quantity, but a comprehensive performance index composed of a series of different mechanical properties such as elasticity, plasticity, and toughness of the material. So, the amount represented by hardness not only depends on the hardness itself, but also on the testing method and conditions.
The significance of hardness testing for metal materials
The physical meaning of hardness is determined by the relationship between its testing method and strength, as well as plasticity or fracture indicators. Overall, it can be summarized as one sentence, that is, the hardness of a metal refers to the ability of the metal to resist deformation or fracture within a small volume range on the surface of the metal.
Through hardness testing, not only can the hardness value of the material itself be measured, but also other properties of metal materials can be measured. These properties are:
1. Measure the elastic properties of materials using the rebound method.
2. Measure the micro plastic deformation resistance using the indentation method to obtain performance similar to the yield limit.
3. Measure a large amount of plastic deformation resistance using the indentation method to obtain properties similar to necking metal strength.
4. Measure the true tensile strength using the scoring method.
5. Measure the deformation specific work using the bounce method.
6. Measure the anisotropy of plastic deformation using indentation and marking methods.
Common metal hardness testers include: micro Vickers hardness tester, Vickers hardness tester, Rockwell hardness tester, and Brinell hardness tester.
