technique articles

Factors Affecting the Test Accuracy of Portable Brinell Hardness Tester (2)

4. sample placement

When selecting anvils and placing samples, it shall be noted that the test surface is perpendicular to the axis of the indenter, and attention shall be paid to prevent sample displacement, local elastic deformation and incorrect direction of force application during the process of force application

For the plane specimen, in order to ensure the vertical force application, it is required that the bearing surface and the test surface have a certain degree of parallelism. Otherwise, the test results will be affected, especially the C scale.

The flat anvil shall be used for the warped plate-shaped specimen, and the convex surface shall rest on the anvil. In this way, the bearing surface of the test point of the sample can be avoided from hanging, resulting in the elastic deformation of the sample under the action of the test force.

For pipe samples, appropriate anvils shall be selected according to the pipe diameter and wall thickness to avoid sample movement or elastic deformation. If the wall thickness of the pipe is insufficient, due to the influence of the elastic deformation of the pipe, errors may occur due to inaccurate measurement of the indentation depth during the test.

5. hardness block failure

The hardness block is only allowed to use its front face. It is impossible for the hardness block to provide unlimited tests. When it is "filled", it should be replaced with a new hardness block. If the hardness block is rusted, the test will be inaccurate, and a new hardness block should also be replaced.

Different instruments are equipped with different hardness blocks. The surface Rockwell hardness tester is equipped with hrn and HRT surface Rockwell hardness blocks, the Rockwell hardness tester is equipped with HRA, HRB and HRC Rockwell hardness blocks, and the Brinell hardness tester is equipped with HBW 5 or HBW 2.5/187.5 hardness blocks. Hardness blocks shall not be mixed, otherwise the measurement is invalid.

6. incorrect force application

During the test, the force shall be applied slowly and evenly, and the pointer of the force value meter shall accurately coincide with the corresponding scale line. If the scale line is not reached or exceeded, the test accuracy will be affected due to the inaccuracy of the test force.

Different test forces shall be selected for different test conditions and different scales. The test force of Rockwell hardness is indicated in black, and that of Brinell hardness is indicated in red. If the test force is selected incorrectly, the measurement is invalid.