The mechanical properties of carbon seamless steel tubes were tested by American Standard. The mechanical properties of test methods can be divided into two categories: tensile test and hardness test.


Tensile test is made of seamless steel tube specimens. Tensile test machine pulls the specimens to the fracture site and then measures one or more mechanical properties. Usually only tensile strength, yield strength, elongation and area reduction rate are measured. Tensile test is the most basic mechanical properties of metals in test methods. Almost all metal materials need to be tested as long as they have mechanical properties. In particular, tensile test is the only way to test the mechanical properties of materials that are not easy to test their hardness.


Hardness test is to press the hard indenter slowly into the sample surface according to the rules, and then test the indentation depth or size to determine the hardness of the material. Hardness testing is the simplest, quickest and easiest method for material testing. Hardness test is non-destructive, and the approximate conversion relationship between hardness and tensile strength is obtained. The hardness of the material can be converted to the tensile strength, which has great practical significance.


Because tensile test is not easy to test and it is very convenient to change from hardness to strength, more and more people only test the hardness of materials but less the strength. Especially due to the improvement and innovation of the hardness of manufacturing technology, some materials which could not be directly tested, such as seamless steel pipe, stainless steel, can now be directly tested hardness. Therefore, there is a tendency to gradually replace tensile test with hardness test.