Complete Conversion Formulas and Analysis of Rockwell, Brinell, Vickers, and Knoop Hardness
Release Time:
2025-05-28
In the machinery industry, whether it's production, sales, or technical personnel, it is necessary to come into contact with different material hardness. Sometimes the hardness representation methods are different, requiring mutual conversion. However, most people cannot handle this. Today, Metal Processing editors have compiled this information, hoping to provide some help to machinery professionals. We also hope you can share it on your social media. Conversion between different types of indentation hardness: In practical applications, the hardness obtained may be from several different testing methods. For easy comparison, different hardness values need to be converted. The Metal Processing WeChat account has good content, worth checking out.
In the machinery industry, whether it's production, sales, or especially technical personnel, everyone needs to come into contact with different material hardnesses. Sometimes the hardness representation methods are different, requiring mutual conversion. However, most people can't handle this easily. Today, Metalworking Editor compiles this information, hoping to provide some help to machinery professionals. We also hope you can share it on your Moments.
Conversion of different types of indentation hardness: In practical applications, the hardness we obtain may come from several different testing methods. For easy comparison, different hardnesses need to be converted. Metalworking WeChat, good content, worth following. So far, some research has been conducted on hardness conversion, but most conversion formulas are proposed under the guidance of practical experience and have not formed a universally recognized conversion system.
The following are some research results on hardness conversion in China.
1. Conversion between Knoop hardness and Vickers hardness
(1) Based on the principle that objects with the same hardness have equal resistance to Knoop and Vickers indenters under the same load, the stress under the load is derived for both Vickers and Knoop indenters, and then according to σHK=σHV, we get: HV=0.968HK. This formula is measured under low load and has a relatively large error. In addition, when the hardness value is greater than HV900, the error of this formula is very large and loses its reference value.
(2) After derivation and correction, the conversion formula between Knoop hardness and Vickers hardness is proposed as:
After verification with actual data, the maximum relative conversion error of this formula is 0.75%, which has high reference value.
2. Conversion between Rockwell hardness and Vickers hardness
(1) After modifying the Qvarnstorm conversion formula proposed by Hans·Qvarnstorm,
The conversion formula between Rockwell hardness and Vickers hardness is obtained as:
This formula is used to convert the published hardness standard data of ferrous metals in China. The HRC error is basically within the range of ±0.4 HRC, and the maximum error is only ±0.9HRC. The maximum calculated HV error is ±15HV.
(2) According to σHRC=σHV, the stress received by different indenters, the formula is derived by analyzing the relationship curve of indentation depth between Rockwell hardness and Vickers hardness:
Compared with the national standard experimental conversion value, the error between the calculation result of the conversion formula and the standard experimental value is ±0.1HRC.
(3) Based on actual experimental data, the linear regression method is used to discuss the conversion between Rockwell hardness and Vickers hardness, and the formula is obtained as:
This formula has a small range of application and a large error, but the calculation is simple and can be used when the accuracy requirement is not high.
3. Conversion between Rockwell hardness and Brinell hardness (1) Analyze the relationship between Brinell indentation and Rockwell indentation depth, and according to the stress σHRC
=σHB, the conversion formula is obtained:
Compared with the national standard experimental value, the error between the calculation result of the conversion formula and the standard experimental value is ±0.1HRC.
(2) The formula is obtained by the linear regression method based on actual experimental data:
The error of the formula is relatively large, and the range of application is small, but the calculation is simple, and it can be used when the accuracy requirement is not high.
4. Conversion between Brinell hardness and Vickers hardness
The relationship between Brinell hardness and Vickers hardness is obtained according to σHB=σHV. The conversion error of this formula is ±2HV compared with the national standard conversion value.
5. Conversion between Knoop hardness and Rockwell hardness
Because the corresponding curve between Knoop hardness and Rockwell hardness is similar to a parabola [7], the approximate conversion formula is obtained from the curve:
This formula is relatively accurate and can be used as a reference.
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