The tensile test is to make a seamless steel pipe into a sample, the tensile sample is broken on a tensile testing machine, and then the mechanical properties are measured. Usually, only the tensile strength, yield strength, elongation and cross-sectional tightening rate are measured. Tensile test is the basic test method for the mechanical function of metal materials. Almost all metal materials can adjust the tensile test as long as they require mechanical functions. Unique raw materials are not convenient for hardness testing. Tensile testing is the only means of mechanical function testing.

The hardness test is to slowly press a hard indenter into the surface of the sample under specified conditions, and then test the depth or size of the indentation to determine the hardness of the raw material. Hardness test is a simple, fast and simple method to detect the mechanical properties of raw materials. The hardness test is correct and destructive. There is an approximate conversion relationship between material hardness and tensile strength. The hardness value of the raw material can be converted into the tensile strength value, which has important application significance.

Since the tensile test is not easy to test, and the conversion from hardness to strength is very simple, people are increasingly testing the hardness of raw materials instead of strength. The unique feature is that due to the continuous improvement of hardness manufacturing techniques and the elimination of old fabrics, some raw materials that cannot be directly tested for hardness, such as seamless steel pipes, stainless steel plates, and stainless steel strips, can still be directly tested for hardness. Therefore, the hardness test gradually replaces the tensile test