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2019-07

Three Kinds of Hardness of Stainless Steel Pipe

Stainless steel pipe is a hollow, elongated, circular steel material widely used in various industries. We need to understand its hardness. This article briefly introduces its three types of hardness:

Stainless steel pipe is a hollow, elongated, circular steel material widely used in various industries. We need to understand its hardness. This article briefly introduces its three types of hardness:

1. Rockwell hardness

The Rockwell hardness test for stainless steel tubes is the same as the Brinell hardness test, which is an indentation test method. The difference is that it is used to measure the depth of indentation. Rockwell hardness test is currently a widely used method. 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 shortcomings of the Brinell method, which is simpler than the Brinell method, and can directly read the hardness value 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. Brinell hardness

Among the standards for stainless steel pipes, Brinell hardness is the most widely used, and the hardness of the material is often expressed by the indentation diameter, which is both intuitive and convenient. However, it is not suitable for steel pipes made of harder or thinner steel.

3. Vickers hardness

The Vickers hardness test for stainless steel pipes is also an indentation test method that can be used to measure the hardness of very thin metal materials and surface layers. It has the main advantages of the Brinell and Rockwell methods, but overcomes their basic disadvantages. However, it is not as simple as the Rockwell method, which is rarely used in steel pipe standards.

4. Hardness testing

Annealed stainless steel pipes with an inner diameter of more than 6.0 mm and a wall thickness of less than 13 mm can be tested using a W-B75 Wechsler hardness tester, which is very fast and simple, and is suitable for rapid non-destructive qualification testing of stainless steel pipes. Stainless steel pipes with an inner diameter greater than 30mm and a wall thickness greater than 1.2mm shall be tested for HRB and HRC hardness using a Rockwell hardness tester. For stainless steel pipes with an inner diameter of more than 30mm and a wall thickness of less than 1.2mm, a surface Rockwell hardness tester is used to test HRT or HRN hardness. For stainless steel pipes with an inner diameter of less than 0mm and greater than 4.8mm, a dedicated Rockwell hardness tester is used to test HR15T hardness. When the inner diameter of stainless steel pipes is greater than 26mm, a Rockwell or surface Rockwell hardness tester can also be used to test the hardness of the inner wall of the pipes.