The hardness measurement. The Brinell hardness test (Part 2).

For measuring Brinell hardness test is usually used a steel ball 10 mm in diameter and a load 3000kgf. However, since the test conditions such as the hardness and thickness of the sample can vary, may require different type and diameter of the ball, and the value of the applied load. Among other types of balls which can be used it is possible to call a 5-mm ball from the tempered steel and a 10-mm ball from tungsten carbide. For soft metals it is possible to use loadings no more than 500 kgf. The equivalent results can be received with loads from 500 to 3000 kgf. When testing Brinell in the field to create a fingerprint is often used hammer strikes on the test specimen and reference sample, which is known hardness. Then, the hardness of the test cell is determined by comparing the fingerprint diameter extruded therein diameter indentation formed on the reference sample.

The value НВ is usually determined by measuring the diameter of the indentation, the appropriate hardness of the table.

Typically, the Brinell test consists of the following steps:

  1. The surface preparation of the under study;
  2. The application of the load;
  3. The load impact during a certain time;
  4. The indentation diameter measurement;
  5. Determination of HB values according the table.

Here it is necessary to pay special attention to the loading application operation during a certain time. For iron and steel this time makes from about 10 to 15 seconds. For softer metals this influence should be prolonged up to 30 seconds. When using figurative models of test cars this hold time is modeled by preservation of hydraulic loading after achievement of test loading. In other test devices shock influence can be used, and hold time isn’t required.

From the description of these simple operations it is visible; the method of determination of hardness according to Brinell is simple. Despite its simplicity, the received results can be rather exact provided that all operations have been executed properly.

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