Definition
The Richter hardness tester is a dynamic hardness testing instrument designed based on the principle of Richter hardness measurement. This instrument indirectly evaluates the hardness value of the material by measuring the ratio of the rebound velocity of the impact body on the surface of the specimen to the impact velocity. As a portable device, it is suitable for rapid testing of the hardness of metal materials in the field or in the laboratory, and can obtain the approximate values of commonly used hardness scales such as Brinell and Rockwell and Vickers by conversion.
Principle
The measurement principle of the Richter hardness tester belongs to the rebound method. The impact body inside the instrument impacts the surface of the specimen vertically at a certain speed under the action of spring force. After impact, the impact body will produce rebound. Through electromagnetic induction, the instrument can accurately measure the impact velocity and rebound velocity of the impact object at a specific distance from the surface of the specimen. The Richter hardness value (HL) is defined as the ratio of the rebound velocity to the impact velocity multiplied by a constant, and is calculated as follows:
HL = (vR / vI) × 1000
Where, vRrepresents rebound velocity, vIRepresents impact velocity. The ratio is correlated with the hardness of the material, and when the hardness of the material is high, the energy consumed by plastic deformation is less, the rebound speed is relatively high, and the measured HL value is also larger.
Measurement method
When measuring with a Richter hardness tester, a standardized operating procedure is followed. First, the appropriate type of impact device should be selected based on the expected hardness and shape size of the material being tested. Before testing, the surface to be tested should be treated with necessary treatments, such as sanding and leveling to ensure stable coupling with the impact device support ring. When measuring, the impact direction should be perpendicular to the test surface of the specimen and sufficient pressure should be applied to stabilize the device. After a single measurement, the instrument displays the HL value directly. It is generally recommended to average multiple measurements around a single point and spread the test over different regions to improve the representativeness of the results. Finally, depending on the material type, the HL value can be converted into a reference value for other hardness scales via the conversion table built into the instrument or provided by standard.
Influencing factors
The measurement results of the Richter hardness tester can be influenced by a variety of factors. In terms of material factors, the quality, thickness, depth of the hardening layer, and the anisotropy of the material itself (e.g., rolling direction) all affect the test value. Geometric factors include the radius of curvature of the piece being measured, and for small diameter tubes or curved workpieces, special support rings or result corrections are required. The test condition factors involve the impact direction, and the non-vertical impact will introduce errors; In addition, the surface roughness and cleanliness of the specimen, as well as the stability of the coupling, are critical. Environmental factors such as strong magnetic fields or severe vibrations can interfere with the proper operation of the instrument. Operators need to fully understand these factors and ensure data reliability through standardized operations and necessary corrections during testing.
Application
Richter hardness testers have a wide range of applications in the industrial sector due to their portability and speed. It is commonly used for on-site hardness testing of large workpieces or installed equipment, such as large gears, shafts, pressure vessels in power plants, and heat-affected zones of pipeline welds. In the manufacturing industry, it can be used to quickly check the hardness of batch products on the production line. In addition, it is also suitable for hardness testing of mold cavities, rolls, and other workpieces that are not easy to move or have complex shapes. In the quality control and material acceptance process, it can provide a quick reference for hardness data. It should be noted that static testing methods such as benchtop hardness testers still need to be relied upon for arbitration testing or testing of extremely thin specimens that require high accuracy.
Selection
Choosing the right Richter hardness timer requires a combination of aspects. First of all, the type of impact device should be determined according to the type of material to be tested, the hardness range and the size of the workpiece, and the impact energy and applicable scenarios of different models are different. Secondly, consider the functional requirements of the instrument, such as whether it needs to be connected to a computer for data management, whether it needs to have multiple built-in material conversion curves, and the requirements for display and storage functions. The durability and reliability of the instrument, including the enclosure protection level and immunity to interference, are important for industrial site environments. In addition, it is necessary to confirm whether the instrument complies with relevant national or international standards, such as GB/T, ASTM or ISO standards, to ensure the standardization of the test method. Finally, the user-friendly design of the operation, such as screen clarity, menu logic and grip feel, can also improve the long-term use experience.