Leeb Hardness Tester
At present, the Leeb hardness tester is widely used in the hardness testing of castings. The Leeb hardness tester adopts the principle of dynamic hardness testing and uses computer technology to realize the miniaturization and electronicization of the hardness tester. It is simple and convenient to use, the reading is more intuitive, and the test results can be easily converted into Brinell hardness values, so it is widely welcomed.
Many castings are medium-to-large workpieces, some of which weigh several tons, and cannot be tested on a bench-top hardness tester. The precise hardness test of castings mainly uses separately cast test rods or test blocks attached to castings. However, neither the test bar nor the test block can completely replace the workpiece itself. Even if it is the same furnace of molten iron, the casting process and heat treatment conditions are the same. Because of the huge difference in size, the heating rate, especially the cooling rate, will be different. It is difficult to make the two have exactly the same hardness. For this reason, many customers care more about and believe in the hardness of the workpiece itself. This requires a portable precision hardness tester to test the hardness of castings. The Leeb hardness tester solves this problem, but it is necessary to pay attention to the surface finish of the workpiece during the use of the Leeb hardness tester. The Leeb hardness tester has requirements for the surface roughness of the workpiece.
Brinell Hardness Tester
Brinell hardness tester should be used for the hardness test of castings. For gray iron castings with relatively coarse grains, the test conditions of 3000kg force and 10mm ball should be used as much as possible. When the casting size is small, Rockwell hardness tester can also be used.
Iron castings usually have uneven structure, larger grains, and contain more carbon, silicon and other impurities than steel, and the hardness will vary in different small areas or at different points. The indenter of the Brinell hardness tester has a larger size and a larger indentation area, and can measure the average value of material hardness within a certain range. Therefore, the Brinell hardness tester has a higher test accuracy and a smaller dispersion of hardness values. The measured hardness value is more representative of the actual hardness of the workpiece. Therefore, the Brinell hardness tester is widely used in the foundry industry.
Rockwell hardness
Rockwell hardness testers are also commonly used for hardness testing of cast iron. For workpieces with fine grains, if there is not enough area for Brinell hardness test, Rockwell hardness test can also be carried out. For pearlitic malleable cast iron, chilled cast iron and steel castings, HRB or HRC scale can be used. If the material is not Evenly, several readings should be measured and the average value should be taken.
Shore Hardness Tester
In individual cases, for some castings with large shapes, it is not allowed to cut the sample, and it is not allowed to cast additional test blocks for hardness testing. At this time, hardness testing will encounter difficulties. For this case, the common method is to test the hardness with a portable Shore hardness tester on the smooth surface after the casting is finished. For example, in the roll standard widely used in the metallurgical industry, it is stipulated that the Shore hardness tester should be used to test the hardness.
Post time: Dec-29-2022
