Rockwell hardness scales and their corresponding indenters and test forces.

Rockwell hardness scales and their corresponding indenters and test forces  by Mikrosize Equipment Supplier.

In the field of materials science and engineering, hardness, as a crucial property of materials, is of self - evident significance. Whether it is in the manufacturing process of components in industrial production to ensure that products have sufficient wear resistance and strength, or in the field of materials research to explore the performance limits of new materials, the study of hardness properties plays an indispensable role. Precisely for this reason, the methods of hardness testing have become the focus of attention in the process of materials research and quality control.

Among numerous hardness testing methods, the Rockwell hardness testing method, with its remarkable characteristics of being convenient, fast, and easy to operate, stands out and has become the most widely used hardness testing method currently. It can obtain the hardness data of materials in a short time, providing timely and effective reference for production and research.

The Rockwell hardness scale system is mainly divided into three categories: common Rockwell, plastic Rockwell, and superficial Rockwell. Each hardness scale has its unique application scenarios and corresponds to specific indenter specifications and matching test forces. Meanwhile, the hardness ranges that each scale can measure also vary.

The common Rockwell hardness scale is suitable for the detection of materials with relatively high hardness, such as conventional metal materials. For example, the HRA scale uses a diamond cone indenter with a major test force of 588.4N and is often used to measure high - hardness materials such as cemented carbide; the HRB scale uses a steel ball indenter with a diameter of 1.588mm and a major test force of 980.7N, and is mostly applied to the hardness testing of softer metals, such as annealed copper alloys; the HRC scale also uses a diamond cone indenter, but the major test force is increased to 1471N, mainly used for the hardness determination of high - hardness metal materials such as quenched steel.

The plastic Rockwell hardness scale is specifically designed for soft materials such as plastics. For instance, the R scale uses a steel ball indenter with a diameter of 12.7mm and a total test force of 588.4N, which is suitable for softer plastic materials; while the M scale uses a steel ball indenter with a diameter of 6.35mm, and the total test force is increased to 980.7N, which can be used for the testing of slightly harder plastic materials.

The superficial Rockwell hardness scale is mainly aimed at the hardness detection of thin layers on the surface of materials. For example, the HR15N scale uses a diamond cone indenter with a total test force of 147.1N and is often used for the hardness measurement of surface hardened layers such as carburized layers and nitrided layers; the HR30N scale has a total test force of 294.2N, and the HR45N scale has a total test force of 441.3N. They play important roles in the surface detection of different hardened layer depths and hardness ranges.

The combinations of different Rockwell hardness scales, indenter specifications, and test forces meet the diverse needs of material hardness testing and provide comprehensive and accurate technical support for material performance evaluation. The following table presents each Rockwell hardness scale, its corresponding indenter specifications, and test forces.

Common Rockwell and plastic Rockwell scales (both with an initial test force of 98.07N/10kgf)

Superficial Rockwell scales (the initial test force is 29.42N/3kgf）

Graph of the Relationship between Rockwell Hardness Value and Minimum Specimen Thickness：