Hardness index of anti-corrosion spiral steel pipe

The ability of metal materials to resist the indentation of the surface of hard objects is called hardness according to different test methods and application ranges. The hardness can be divided into Vickers hardness, Shore hardness, Brinell hardness, Rockwell hardness, microhardness, and high temperature. Hardness, etc. For anti-corrosion spiral steel pipes, there are generally three types Rockwell hardness, Brinell hardness, and Vickers hardness.

A. Rockwell hardness (HK) 

Rockwell hardness test is the same as the Brinell hardness test, both are indentation test methods. The difference is that it measures the depth of the indentation. That is, under the successive action of the initial test force (Fo) and the total test force (F), the indenter (cone or steel ball) is pressed into the surface of the sample, and after the specified holding time, the main force is removed. Test force, the hardness value is calculated from the measured residual indentation depth increment (e).

B. Brinell hardness (HB) 

Use a steel ball or cemented carbide ball with a certain diameter, press it into the surface of the sample with the specified test force (F), remove the test force after the specified holding time, and measure the indentation diameter on the surface of the sample (L) The Brinell hardness value is the quotient obtained by dividing the test force by the surface area of the indentation spherical.

C. Vickers hardness (HV) 

Vickers hardness test is also an indentation test method, which is to press a regular quadrangular pyramid diamond indenter with an opposite angle of 1360 into the test surface with a selected test force (F). After the specified holding time, remove the test force and measure the two diagonal lengths of the indentation. The Vickers hardness value is the quotient obtained by dividing the test force by the indentation surface area, and its calculation formula is in the formula: HV--Vickers hardness symbol, N/mm2 (MPa); F--test force, N; d--pressure Arithmetic mean of the two diagonals of the marks, mm. The test force F used for Vickers hardness is 5 (49.03), 10 (98.07), 20 (196.1), 30 (294.2), 50 (490.3), 100 (980.7) Kgf (N) six grades, and the hardness value can be measured The range is 5 to 1000HV.