Introduction to Rockwell Hardness Test Method

Rockwell hardness test uses a standard indenter (a diamond cone indenter with a vertex angle of 120 degrees or a tungsten carbide ball indenter with a diameter of 1.58 mm) to press into the surface of the tested material under a certain test force, and the indentation depth is obtained The hardness of the material.

The test is: first, the indenter applies the initial test force F0 to the surface of the material to be tested, and stabilizes for 3-5 seconds, then applies the main test force F1 to make the total test force equal to (F0+F1), and then stabilizes for 3-5 seconds. Remove the main test force F1, and maintain the initial test force F0, and after 3-5 seconds of stabilization, remove the initial test force F0. The difference between the indentation depth after the main test force is applied and before the main test force is applied has a linear relationship with the Rockwell hardness value of the material. On the Rockwell hardness scale, every 2 micron indentation depth difference represents a Rockwell hardness scale. The symbol of Rockwell hardness is expressed in HR.

In order to adapt to the application of various materials, Rockwell hardness scales are distinguished according to different combinations of indenters and test forces used. ①HRA is the hardness measured by a total test force of 60 kg and a diamond cone indenter, and is used to test materials with high hardness, such as cemented carbide; ②HRB is a test force of 100 kg and a tungsten carbide ball with a diameter of 1.58 mm. The hardness measured by the indenter is used for materials with lower hardness, such as mild steel, non-ferrous metals, annealed steel, cast iron, etc.; High material, such as: hardened steel, etc. Because the Rockwell hardness measurement method is relatively simple and relatively cheap, it is widely used. Therefore, it is necessary to equip a Vickers hardness tester for units that carry out surface heat treatment or use a large number of surface heat treatment workpieces.

2. Surface Rockwell hardness tester: It is also very suitable for testing the hardness of surface quenched workpieces. There are three scales to choose from for surface Rockwell hardness testers, which can test various surface hardened workpieces whose effective hardening depth exceeds 0.1mm. Although the surface Rockwell hardness The accuracy of the Vickers hardness tester is not as high as that of the Vickers hardness tester, but as a detection method for quality management and qualification inspection in heat treatment plants, it can already meet the requirements. Moreover, it has the advantages of simple operation, convenient use, low price, rapid measurement, and direct reading of hardness. The surface Rockwell hardness tester can be used to quickly and non-destructively detect batches of surface heat-treated workpieces one by one, which is of great significance for metal processing and machinery manufacturing factories.

3. Rockwell hardness tester: When the surface heat treatment hardened layer is thick, the Rockwell hardness tester can also be used. When the heat treatment hardened layer thickness is 0.4~0.8mm, the HRA scale can be used. When the hardened layer thickness exceeds 0.8mm, HRC scale can be used. )

4. Hardness testing: For annealed stainless steel pipes with an inner diameter of 6.0mm or more and a wall thickness of 13mm or less, the W-B75 Webster hardness tester can be used. conformity inspection. For stainless steel tubes with an inner diameter greater than 30mm and a wall thickness greater than 1.2mm, use a Rockwell hardness tester to test the hardness of HRB and HRC. For stainless steel pipes with an inner diameter greater than 30mm and a wall thickness less than 1.2mm, use a surface Rockwell hardness tester to test the hardness of HRT or HRN. For stainless steel pipes with an inner diameter less than 0mm and greater than 4.8mm, use a special Rockwell hardness tester for pipes to test the hardness of HR15T , When the inner diameter of the stainless steel pipe is greater than 26mm, the hardness of the inner wall of the pipe can also be tested with the Cangzhou Oupu Rockwell or Surface Rockwell hardness tester.