Seamless steel tube hardness test

Seamless steel tube hardness test

Seamless steel tubes are commonly used to measure the hardness of Brinell, Rockwell, and Vickers.
1. Brinell hardness
Among the seamless steel pipe standards, Brinell hardness is the most widely used, and the hardness of the material is often expressed by the indentation diameter, which is intuitive and convenient. However, it is not suitable for steel pipes with harder or thinner steel.
2. Rockwell hardness The Rockwell hardness test of seamless steel tubes 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. Rockwell hardness test is a widely used method at present, in which HRC is second only to Brinell hardness HB in the steel pipe standard. Rockwell hardness can be applied to the measurement of metal materials from extremely soft to extremely hard. It makes up for 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, because of its small indentation, the hardness value is not as accurate as the Brinell method.
3. Vickers hardness The Vickers hardness test of seamless steel tubes 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 the Brinell and Rockwell methods, and overcomes their basic shortcomings, but it is not as simple as the Rockwell method, and the Vickers method is rarely used in steel pipe standards.

Seamless steel tube hardness testing 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 using stainless steel as a raw material. Therefore, all seamless steel tubes must be tested for mechanical properties. The 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 seamless steel tube into a sample, pull the sample to break on a tensile test machine, and then measure one or several mechanical properties, usually only the tensile strength, yield strength, elongation after break and rate of reduction in area. 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, all provide tensile tests. Especially for materials whose shape is not convenient for hardness testing, tensile testing becomes the only means of testing mechanical properties.
The hardness test is to slowly press a hard indenter into the surface of the sample according to the specified conditions, and then test the depth or size of the indentation to determine the hardness of the material. The hardness test is the simplest, fastest and easiest method to perform in the mechanical properties test of materials. The hardness test is non-destructive, and there is an approximate conversion relationship between the material hardness value and the tensile strength value. The hardness value of the material can be converted into a tensile strength value, which has great practical significance.
Because the tensile test is not easy to test, and it is very convenient to convert from hardness to strength, people are increasingly testing only the hardness of the material and less testing its strength. In particular, due to the continuous advancement and innovation of the hardness tester manufacturing technology, some materials that could not be directly tested for hardness, such as seamless steel tubes, stainless steel plates and stainless steel bands, are now possible to directly test the hardness. Therefore, there is a tendency that the hardness test gradually replaces the tensile test.
Most of the national standards for stainless steel materials specify both tensile test and hardness test. For those materials that are not convenient for hardness testing, such as seamless steel tubes, only tensile tests are specified. In the stainless steel standard, three hardness test methods of cloth, Luo, and Wei are generally specified to determine the hardness values ​​of HB, HRB (or HRC), and HV, and only one of the three hardness values ​​is required. In particular, the company's newly developed portable surface Rockwell hardness tester and pipe Rockwell hardness tester can quickly and accurately test the hardness of stainless steel plates, stainless steel strips and seamless steel tubes as thin as ¢ 4.8mm It has solved problems that were difficult to solve in the past.

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