BHN vs. HRC

Attribute	BHN	HRC
Definition	Brinell Hardness Number	Rockwell Hardness C Scale
Measurement method	Indentation hardness test using a hardened steel ball	Indentation hardness test using a conical diamond penetrator
Scale range	0-1000	20-70
Material suitability	Generally used for softer materials	Commonly used for harder materials

Introduction

Brinell Hardness Number (BHN) and Rockwell Hardness Number (HRC) are two common methods used to measure the hardness of materials. Both methods provide valuable information about the material's resistance to deformation, but they have distinct differences in terms of testing procedures, applications, and accuracy.

Testing Procedure

BHN is determined by measuring the diameter of an indentation made by a hardened steel ball or carbide ball under a known load. The hardness number is calculated based on the applied load and the surface area of the indentation. On the other hand, HRC uses a conical diamond or hardened steel ball to make an indentation on the material's surface. The depth of the indentation is measured, and the hardness number is determined based on the depth of penetration.

Accuracy

One of the key differences between BHN and HRC is their accuracy in measuring hardness. BHN is known for its high accuracy in measuring the hardness of soft materials, such as aluminum and copper alloys. However, it may not be as accurate for harder materials like steel. On the contrary, HRC is more accurate for measuring the hardness of hard materials due to its ability to penetrate deeper into the material's surface.

Applications

Both BHN and HRC have specific applications where they excel. BHN is commonly used in industries where softer materials need to be tested, such as automotive and aerospace industries. It is also preferred for materials with irregular shapes or rough surfaces. In contrast, HRC is widely used in the manufacturing of tools, dies, and machine parts where high hardness values are required. It is also suitable for measuring the hardness of heat-treated materials.

Conversion

Since BHN and HRC are two different scales for measuring hardness, it is often necessary to convert between the two. There are conversion charts available that allow for easy conversion between BHN and HRC values. However, it is important to note that the conversion may not be exact due to the differences in testing procedures and materials being tested.

Cost

Another factor to consider when choosing between BHN and HRC is the cost associated with each method. BHN testing equipment, such as the Brinell hardness tester, can be more expensive compared to HRC testing equipment, such as the Rockwell hardness tester. Additionally, the cost of maintenance and calibration for BHN equipment may be higher, making HRC a more cost-effective option for some industries.

Conclusion

In conclusion, both BHN and HRC are valuable methods for measuring the hardness of materials, each with its own strengths and limitations. BHN is preferred for softer materials and irregular surfaces, while HRC is more accurate for harder materials and heat-treated alloys. The choice between BHN and HRC ultimately depends on the specific requirements of the application, budget constraints, and the desired level of accuracy.