hardness

 

Brinell, Rockwell and Vickers are commonly used to measure the hardness of stainless steel tubes.

 

Brinell hardness

 

In the standard of stainless steel pipe, Brinell hardness is the most widely used. The indentation diameter is often used to express the hardness of the material, which is both intuitive and convenient. But it is not suitable for steel pipes with harder or thinner steel.

 

Rockwell hardness

 

Rockwell hardness test of stainless steel tube is the same as Brinell hardness test, which is indentation test method. The difference is that it measures the depth of indentation. Rockwell hardness test is a widely used method at present, and HRC is used in steel pipe standard only after Brinell hardness HB. Rockwell hardness can be applied to the determination of metal materials from very soft to very hard. It makes up for the shortcoming of the Brinell method. It is simpler than the Brinell method and can read the hardness value directly from the dial of the hardness machine. However, because of its small indentation, the hardness value is not as accurate as that of Brinell method.

 

Vickers hardness

 

The Vickers hardness test of stainless steel tubes is also an indentation test method, which can be used to measure the hardness of very thin metal materials and surface layer. It has the main advantages of Brinell's method and Rockwell's method, and overcomes their basic shortcomings, but it is not as simple as Rockwell's method, and Vickers method is seldom used in steel pipe standards.

 

Hardness Testing

 

The W-B75 Wechsler hardness tester can be used for annealed stainless steel pipes with inner diameter over 6.0 mm and wall thickness under 13 mm. The tester is very fast and simple, and it is suitable for rapid and non-destructive inspection of stainless steel pipes. The hardness of HRB and HRC of stainless steel pipe with diameter greater than 30 mm and wall thickness greater than 1.2 mm was tested by Rockwell hardness tester. Stainless steel pipes with inner diameter greater than 30 mm and wall thickness less than 1.2 mm were tested by surface Rockwell hardness tester for HRT or HRN hardness. HR15T hardness of stainless steel pipes with inner diameter less than 0 mm and larger than 4.8 mm was tested by Rockwell hardness tester. When the inner diameter of stainless steel pipe is larger than 26 mm, the hardness of the inner wall of the pipe can also be measured by Rockwell hardness tester or surface Rockwell hardness tester.