Stainless steel pipe is a hollow long round steel, which is widely used in petroleum, chemical, medical, food, light industry, mechanical instrumentation and other industrial pipelines and mechanical structural parts. In addition, when the bending and torsion strength are the same, the weight is lighter, so it is also widely used in the manufacture of mechanical parts and engineering structures. It is also often used as furniture and kitchen utensils. Stainless steel pipes generally use three hardness indexes, Brinell, Rockwell, and Vickers to measure their hardness. Now, let us have a simple understanding of these three hardness indicators!
Three indicators for weighing the hardness of stainless steel pipes:
Rockwell hardness
The Rockwell hardness test of stainless steel pipe is the same as the Brinell hardness test, which is the indentation test method. The difference is that it measures the depth of the indentation. Rockwell hardness test is currently a widely used method, among which HRC is second only to Brinell hardness HB in steel pipe standards. Rockwell hardness can be used to measure metal materials from extremely soft to extremely hard. It makes up for the difference of the Brinell method and is simpler than the Brinell method. The hardness value can be read directly from the dial of the hardness machine. However, due to its small indentation, the hardness value is not as accurate as the Brinell method.
2. Vickers hardness
The stainless steel tube Vickers hardness test is also an indentation test method, which can be used to determine the hardness of very thin metal materials and surface layers. It has the main advantages of Brinell and Rockwell method, and overcomes their basic shortcomings, but it is not as simple as Rockwell method. Vickers method is rarely used in steel pipe standards.
Three, hardness testing
For stainless steel pipes with an inner diameter above 6.0mm and wall thickness below 13mm, the W-B75 Webster hardness tester can be used. The test is very fast and simple, and it is suitable for quick and non-destructive qualification inspection of stainless steel pipes. For stainless steel pipes with an inner diameter greater than 30mm and a wall thickness greater than 1.2mm, the Rockwell hardness tester is used to test the hardness of HRB and HRC. Stainless steel pipes with inner diameters greater than 30mm and wall thicknesses less than 1.2mm shall be tested with HRT or HRN hardness using a surface Rockwell hardness tester. For stainless steel pipes with an inner diameter of less than 0mm and greater than 4.8mm, use a special Rockwell hardness tester for pipes to test the hardness of HR15T. When the inner diameter of the stainless steel pipe is greater than 26mm, the hardness of the inner wall of the pipe can also be tested with a Rockwell or surface Rockwell hardness tester.
