The relationship between the properties of the material being measured and the selection of the Richter hardness tester
The Richter hardness test method characterizes the hardness of a material based on the ratio of the rebound velocity of the impact body to the impact velocity, and its principle formula is: HL = (vR / vA) × 1000, where HL is the Richter hardness value, vRis the rebound velocity, vAis the speed of impact. To choose the right Richter hardness meter, the physical and mechanical properties of the material being measured must be considered first, including material type, hardness range, geometric dimensions, surface condition, and microstructure. These factors directly affect the selection of the test impact body, the setting of the impact energy, and the accuracy and repeatability of the final measurement results.
The impact device is selected according to the material type
The impact device of the Richter hardness tester, which is usually distinguished by different impact body types, needs to be matched to the material being measured. The elastic modulus, density, and plastic deformation behavior of different materials vary significantly, and the adapted impact device ensures that the impact energy is effectively absorbed and a clear rebound signal is generated. The general-purpose impact body is suitable for most common metal materials; For materials with low elastic modulus or thin elastic modulus, a device with less impact energy should be selected to avoid visible indentation or deformation of the specimen. For hardened layers or small components, consider using a specialized device with a more concentrated impact energy and a smaller probe.
| Major categories of materials to be tested | It is recommended to consider the type of impact body |
| Carbon steel, alloy steel, cast steel | General Purpose Type (Type D) |
| Stainless steel, tool steel | General purpose (Type D) or Specialized Type (Type C) |
| Aluminum alloy, copper alloy | Low energy type (type G or type C) |
| gray cast iron, ductile iron | Specialized type (Type C or Type D) |
| Sheet material (less than 3mm thick) | Low Energy Type (Type G) |
| Surface coating/bleeding layer | Low energy or ultra-low energy |
Consider the hardness range of the material and the specimen conditions
The expected hardness range of the material to be tested is a key parameter for selecting the hardness tester and impact device. Richter hardness testers usually have a corresponding measurement range, and it is necessary to ensure that the hardness of the material being measured falls within this range. At the same time, the geometric dimensions (thickness, mass, radius of curvature) and surface roughness of the specimen must meet the requirements of the corresponding test conditions. For example, when testing thin-walled specimens, the "mass effect" and "thickness effect" need to be evaluated, and if necessary, support rings or specific impact devices should be selected. If the surface roughness is too rough, it will disperse the impact energy and affect the test value, usually requiring the test surface to achieve a certain finish.
| Sample conditions and constraints | Selection and operation precautions |
| Hardness value range | Confirm the range coverage of the selected impact device |
| Minimum thickness of the specimen | It must be greater than the minimum thickness specified by the impact device |
| Minimum mass of specimens | The specified value must be met, otherwise rigid coupling is required |
| The radius of curvature of the test surface | A small radius of curvature requires the use of a surface support ring |
| Surface roughness | It needs to be sanded or polished below the specified Ra value |
| Material anisotropy | Test and evaluate differences in different directions |
Test results
The Richter hardness test is an indirect comparison method. For reports that comply with specific traditional hardness standards (e.g. Brinell HBW, Rockwell HRC, Vickers HV), conversion must be done using a conversion table or conversion function established according to the standard method. Conversions must be limited to similar materials and there will be some uncertainty about the conversion results. Before important testing, it is recommended to verify on a test block of the same material with a known standard hardness to confirm the suitability of the instrument setup and impact device selection. For new or unknown materials, benchmark data should be established through traditional hardness testing methods.
Standard compliance
The final choice also considers whether the test environment (e.g., temperature, vibration) meets the instrument's operating requirements and whether the tests performed need to comply with specific national or international standards. For example, for quality control in some industries, testing procedures may be required to strictly comply with standards such as ASTM A956 or ISO 16859 regarding instrument calibration, testing procedures, and result handling. Ensuring the traceability of the entire test system is the basis for guaranteeing reliable results.
Cited Literature
ASTM A956 - Standard Test Method for Richter Hardness Testing of Steel Products.
ISO 16859-1 - Richter hardness test for metallic materials - Part 1: Test methods.
GB/T 17394.1 - Metallic materials - Richter hardness test - Part 1: Test methods.