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Precautions when grinding rods are strengthened

Views: 224 Update Date:May 20 , 2022
When the surface of the grinding rod is strengthened, the following principles should be followed. The maximum and minimum hardness difference at 3 points on the same rod should not exceed 0.5HRC, and the maximum hardness difference between the grinding rods should not exceed 1HRC.

1. The hardness value of the surface of the grinding rod increases with time, but after a certain period of time, the hardness does not increase significantly, and the time is long, the productivity is low, and it is easy to crack the surface of the grinding rod and damage the inner rod. Therefore, under the premise of maintaining hardness, the strengthening time should be limited to minimize the range within the rod and the range between rods.

2. The grinding rod test shows that the surface hardness of the grinding rod increases rapidly at the beginning of strengthening, and the range within the rod and the rod shape range that characterize the uniformity of hardness generally increase, reaching the highest point for about 2~4h. Then it started to drop, with the lowest point at about 4-6 hours. This change is related to the diameter of the rod. Generally, the reinforcement larger than 9.525mm is about 4h, and the reinforcement smaller than 9.25mm is about 5~6h. The strength uniformity is the best, and the hardness value in both cases also meets the requirements.


grinding rod


3. The effect of strengthening time on the structure of the grinding rod. After heat treatment, the microstructure of the grinding rod is martensite and retained austenite. Martensite has dislocation type and twin type. The dislocation type is plate-like and non-uniform. The twins are flaky and very brittle. After strengthening and breaking, cracks will be induced; the retained austenite is soft and can be partially transformed into martensite after strengthening, but if the strengthening time is too long, it will no longer transform, and cracks may occur on the surface.

4. The effect of strengthening time on the crushing load of the grinding rod. In the initial stage of strengthening, the crushing load of the grinding rod increases rapidly, and then changes slowly or even decreases slightly when the steel is further strengthened. This is because the metal brittleness of the surface layer increases, and the strength is weakened by excessive strengthening.
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