In the machining industry, quality control of parts is crucial, and hardness, as one of the key indicators to measure material performance, has a profound impact on the service life and reliability of the product. Imagine that when the mechanical parts you carefully designed and manufactured wear out quickly due to insufficient hardness during operation, or cause brittle fracture due to excessive hardness, it will be a great waste of time, cost and energy. At this time, the Brinell hardness, Rockwell hardness and Vickers hardness test methods come in handy. They are like precise "quality referees" that can accurately evaluate the ability of materials to resist deformation and damage. Brinell hardness, with its large indentation reflecting the average hardness of the material, is suitable for large workpieces such as castings and forgings that are not very sensitive to surface damage; Rockwell hardness, with its fast and efficient testing process, has become the first choice for quality inspection of mass-produced parts; Vickers hardness, with its tiny indentation, helps the hardness analysis of microstructures and thin layers of materials.
What is Test principle ?
Brinell hardness: Use a carbide ball of a certain diameter to press into the surface of the material to be tested with a specified test force. After keeping it for a specified time, measure the indentation diameter, and express the hardness value as the average pressure per unit area of the indentation.
Rockwell hardness: Use a diamond cone or a steel ball of a certain diameter as an indenter. Under the action of the initial test force and the main test force, press the indenter into the surface of the material to be tested. Determine the hardness value based on the indentation depth.
Vickers hardness: Use a regular tetrahedral diamond indenter with a relative angle of 136° to press into the surface of the material to be tested under the action of a specified test force. After keeping it for a specified time, measure the diagonal length of the indentation, and determine the hardness value by calculating the average pressure on the surface area of the indentation.
Hardness value representation
Brinell hardness: The unit of hardness value is MPa, but the unit is usually not marked, such as HBW10/3000/30 represents the Brinell hardness value measured by using a carbide ball with a diameter of 10mm and maintaining a test force of 3000kgf for 30s.
Rockwell hardness: According to different scales, the hardness value is directly expressed in numbers, such as HRA, HRB, HRC, etc., and the number behind is the hardness value. For example, HRC60 means that the Rockwell hardness value measured by the C scale is 60.
Vickers hardness: The unit of hardness value is MPa, but the unit is usually not marked, such as HV10 represents the Vickers hardness value measured under a test force of 10kgf.
Test range
Brinell hardness: Generally suitable for measuring materials with lower hardness such as soft steel, gray cast iron and non-ferrous metals after annealing, normalizing, quenching and tempering. The Brinell hardness value is usually below 450HBW.
Rockwell hardness: Applicable to materials of various hardness ranges, different scales can measure materials of different hardness. For example, the HRA scale is applicable to high-hardness materials, such as cemented carbide, etc.; the HRB scale is applicable to softer materials, such as annealed copper alloy, etc.; the HRC scale is applicable to materials with higher hardness, such as hardened steel, etc.
Vickers hardness: The test range is wide, and it can be applied to various materials from soft metals to cemented carbide, especially suitable for measuring the hardness of different phases or small areas in the microstructure.
Indentation shape and size
Brinell hardness: The indentation is circular with a large diameter, which causes greater damage to the material surface. Due to the large indentation, it can reflect the average hardness of a larger area of the material, and the test results are relatively stable.
Rockwell hardness: The indentation is conical or spherical, and the indentation is small. The Rockwell hardness test is efficient and causes less damage to the material surface, but due to the small indentation, the test results are greatly affected by the unevenness of the material microstructure.
Vickers hardness: The indentation is a square pyramid with a small indentation size. The indentation profile of the Vickers hardness test is clear, and the diagonal length measurement accuracy is high, so the hardness value is relatively accurate.
Application
Brinell hardness: commonly used for raw material inspection, hardness determination of annealed and normalized materials, and hardness detection of parts with low hardness requirements, such as large castings and forgings. It is widely used in some occasions where the surface quality requirements are not high, but the overall hardness performance of the material needs to be understood.
Rockwell hardness: the most widely used in production practice, such as part hardness detection during machining, hardness control after heat treatment, quality inspection of metal materials, etc. Due to the high test efficiency, it is particularly suitable for rapid detection in mass production.
Vickers hardness: commonly used to study the relationship between the microstructure and hardness of materials, such as analyzing the hardness of alloy phases, hardness changes of different organizations during heat treatment, etc. In the field of scientific research and precision machining, Vickers hardness testing has unique advantages for hardness measurement of tiny parts, thin parts and surface treatment layers.
