Stainless steel pipe hardness test

Stainless steel pipes are generally measured by three hardness indicators: Brinell, Rockwell and Vickers.

1. Brinell hardness

In the standard of stainless steel pipes, Brinell hardness is the most widely used. The hardness of the material is often expressed by the diameter of the indentation, which is both intuitive and convenient. However, it is not applicable to steel pipes made of harder or thinner steel.

2. Rockwell hardness

The Rockwell hardness test of stainless steel pipes is the same as the Brinell hardness test, which is an indentation test method. The difference is that it measures the depth of the indentation. The Rockwell hardness test is currently a widely used method, among which HRC is second only to the Brinell hardness HB in the use of 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. It is simpler than the Brinell method and 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.

3. Vickers hardness

The Vickers hardness test of 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, and overcomes their basic disadvantages, but it is not as simple as the Rockwell method, and the Vickers method is rarely used in steel pipe standards.

Stainless steel pipe hardness test method

The hardness test of stainless steel should take into account its mechanical properties, which is related to the performance and quality of deformation, stamping, cutting and other processing with stainless steel as raw material. Therefore, all stainless steel pipes must be tested for mechanical properties. Mechanical property test methods are mainly divided into two categories, one is tensile test and the other is hardness test. The

tensile test is to make a stainless steel pipe into a specimen, pull the specimen to break on a tensile testing machine, and then measure one or several mechanical properties, usually only tensile strength, yield strength, elongation after fracture and cross-sectional shrinkage. Tensile test is the most basic mechanical property test method for metal materials. Almost all metal materials, as long as there are requirements for mechanical properties, have tensile tests specified. Especially for those materials whose shapes are not convenient for hardness testing, tensile test becomes the only means of mechanical property testing. The

hardness test is to slowly press a hard indenter into the surface of the specimen under specified conditions, and then test the depth or size of the indentation to determine the hardness of the material. Hardness test is the simplest, fastest and easiest to implement method in material mechanical property test. Hardness test is non-destructive, and there is an approximate conversion relationship between material hardness value and tensile strength value. The hardness value of the material can be converted into tensile strength value, which has great practical significance.

Since tensile test is not convenient for testing, and it is very convenient to convert hardness to strength, more and more people only test the hardness of materials and less test their strength. In particular, due to the continuous progress and innovation of hardness tester manufacturing technology, some materials that could not be directly tested for hardness, such as stainless steel pipes, stainless steel plates and stainless steel strips, can now be directly tested for hardness. Therefore, there is a trend that hardness test gradually replaces tensile test.

Most of the national standards for stainless steel materials stipulate tensile test and hardness test at the same time. For those materials that are not convenient for hardness test, such as stainless steel pipes, only tensile test is stipulated. In stainless steel standards, three hardness test methods are generally stipulated: Burkhardt, Lowe's and Vickers hardness test methods, which measure HB, HRB (or HRC) and HV hardness values, and only one of the three hardness values ​​is stipulated to be measured. In particular, the portable surface Rockwell hardness tester and pipe Rockwell hardness tester newly developed by our company can quickly and accurately test the hardness of stainless steel plates and strips as thin as 0.05mm and stainless steel pipes as thin as 4.8mm, which solves the problems that were difficult to solve in the past.

Stainless steel pipe hardness testing tool

For annealed stainless steel pipes with an inner diameter of more than 6.0mm and a wall thickness of less than 13mm, the W-B75 Webster hardness tester can be used. It is very fast and simple to test, and is suitable for fast and non-destructive qualified 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 HRB and HRC hardness. For stainless steel pipes with an inner diameter greater than 30mm and a wall thickness less than 1.2mm, the surface Rockwell hardness tester is used to test the HRT or HRN hardness. For stainless steel pipes with an inner diameter less than 0mm and a wall thickness less than 4.8mm, the Rockwell hardness tester dedicated to pipes is used to test the HR15T hardness. 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. (end)