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With China Plastic Machinery
With China Plastic Machinery
Plastic Rockwell hardness is a measurement method for expressing the hardness of materials. During the measurement, a specified indenter is pressed on the sample with a small load, then gradually increased to a larger value, and then returned to the smaller load.
Plastic Rockwell hardness is a material hardness value expressed by the net increase in the depth of the indentation on the sample caused by this. Different scales are specified according to the size of the indenter and the load value. For example, there are k scales, L scales, M scales, etc. There is no simple conversion relationship between different scales.
The advantages of this method are a wide range of measurements, simple operation, and no damage to the sample. The disadvantage is that due to the small indentation, if the material has uneven organization, the representativeness is poor, so the data is more discrete. In addition, since the pressures obtained with different scales are not geometrically similar, the hardness values measured with different scales cannot be compared with each other and strictly converted to the same amount.
1. The basic requirements of the Rockwell hardness test are that the surface to be tested should be perpendicular to the indenter, and the specimen to be tested should not move or slide slightly when the main load is applied. The indentation depth is measured by the displacement of the spindle on which the indenter is installed. Therefore, any movement or sliding of the specimen will be transmitted from the spindle to the dial, causing errors in the test.
2. In the hardness test, it is strictly forbidden to turn the variable load handwheel when adding test force, maintaining the moving test force, and removing the test force.
Rockwell hardness is an indicator that determines the hardness value based on the depth of plastic deformation of the indentation, with 0.002 mm as a hardness unit. Using different indenters and different test forces in the Rockwell hardness test will produce different combinations, corresponding to different Rockwell hardness scales. There are 3 commonly used scales, and their applications cover almost all commonly used metal materials.
For Rockwell hardness (HR) test, when the sample to be tested is too small or the Brinell hardness (HB) is greater than 450, Rockwell hardness measurement is used instead. The test method is to use a diamond cone with a vertex angle of 120 degrees or a steel ball with a diameter of 1.5875mm/3.175mm/6.35mm/12.7mm to press into the surface of the material to be tested under a certain load, and the hardness of the material is calculated from the indentation depth. The three most commonly used scales are A, B, and C, namely HRA, HRB, and HRC. According to the hardness of the experimental material, scales with different hardness ranges should be used to indicate it.
1. HRA is the hardness obtained by using a 60Kg load and a diamond cone indenter, and is used for materials with higher hardness. For example: steel thin plates, cemented carbide.
2. HRB is the hardness obtained by using a 100Kg load and a hardened steel ball with a diameter of 1.5875mm, and is used for materials with lower hardness. For example: mild steel, nonferrous metals, annealed steel, etc.
3.HRC is the hardness obtained by using a 150Kg load and a diamond cone indenter, and is used for materials with higher hardness. For example: hardened steel, cast iron, etc.
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