The selection of mechanical testing equipment for cast iron brake shoes shall comply with the standard: ICS 45.060.20. This standard specifies that the mechanical property testing is divided into two parts:
1.Tensile Test
It shall be carried out in accordance with the provisions of ISO 6892-1:2019. The dimensions and processing quality of tensile specimens shall meet the requirements of ISO 185:2005.
2.Hardness Testing Method
It shall be implemented in accordance with ISO 6506-1:2014. Hardness specimens shall be cut from the lower half of the separately cast test bar; if there is no test bar, one brake shoe shall be taken, 6mm – 10mm shall be planed off from its side, and the hardness shall be measured at 4 test points, with the average value being the test result.
Basis for Hardness Testing Method
The standard ISO 6506-1:2014 “Metallic Materials – Brinell Hardness Test – Part 1: Test Method”specifies the principle, symbols and explanations, test equipment, specimens, test procedures, uncertainty of results and test report for the Brinell hardness test of metallic materials.
2.1 Selection of Test Equipment: Brinell Hardness Tester (Recommended Firstly)
Advantages:The indentation area is large, which can reflect the overall hardness of the cast iron material (cast iron may have uneven structure), and the results are more representative.
It is suitable for medium and low hardness cast iron (HB 80 – 450), which fully covers the hardness range of cast iron brake shoes.
The operation is relatively simple, and the requirement for the surface finish of the specimen is relatively low (generally Ra 1.6 – 6.3μm is sufficient).
2.2 Principle of Brinell Hardness Test
The principle can be summarized as follows: A hard alloy ball (or quenched steel ball) with a diameter of 10mm is pressed into the surface of the specimen under a certain test force (such as 3000kgf). After measuring the indentation diameter, the hardness value (HBW) is calculated to characterize the material’s ability to resist plastic deformation. Its core advantage lies in the strong representativeness of the results, which can reflect the macroscopic hardness characteristics of the material. It is a classic method widely used in the performance testing of metallic materials.
2.3 Symbols and Explanations of Brinell Hardness Value
The core definition of the Brinell hardness value (HBW) is: the ratio of the test force (F) to the indentation surface area (A), with the unit of MPa (but usually the unit is not marked, and only the numerical value is used). The calculation formula is as follows:HBW=πD(D−D2−d2)2×0.102×F
Where:
F is the test force (unit: N);
D is the indenter diameter (unit: mm);
d is the average diameter of the indentation (unit: mm);
The coefficient “0.102″ is a conversion factor used to convert the test force unit from kgf to N (if calculated directly in N, the formula can be simplified).
It can be seen from the formula that under the same test force and indenter diameter, the smaller the indentation diameter, the stronger the material’s ability to resist plastic deformation, and the higher the Brinell hardness value; conversely, the lower the hardness value.
According to the material characteristics of cast iron brake shoes (gray cast iron), the parameters of the Brinell hardness test are usually as follows:
Test force (F): Generally, 3000kgf (29.42kN) is used, and the corresponding hardness symbol is “HBW 10/3000″.
Note: If the specimen is thin or the material is soft, the test force can be adjusted (such as 1500kgf or 500kgf) in accordance with ISO 6506-1:2014, but this shall be indicated in the test report.
Post time: Aug-26-2025
