Hardness test of steel pipe
Hardness test of steel pipe
Steel tube hardness test is the quickest, most economical and simplest test method to evaluate the mechanical properties of steel tube. The main purpose of steel tube hardness testing is to determine the applicability of the steel tube, or the effect of special hardening or softening treatment for the purpose of use.
Hardness is one of the most commonly used indexes for evaluating the mechanical properties of steel tubes. The hardness is essentially the ability of the steel tube to resist the entry of another hard material. For the tested steel pipe, hardness represents the comprehensive properties of elasticity, plasticity, strength, toughness and wear resistance reflected by certain indenter and test force.
Principle of steel tube hardness test
The steel tube hardness test is to determine the hardness of the steel tube by slowly pressing a hard indenter into the surface of the steel tube specimen according to the prescribed conditions, and then testing the indentation depth or size. The hardness test is non-destructive, and there is an approximate conversion relationship between the hardness value and the tensile strength value of the steel tube. The hardness value of steel tube can be converted into tensile strength value.
Method for hardness testing of steel tubes
The determination of hardness is mainly determined by the depth of indentation, the area of indentation projection or the area of indentation gravure.
The main test method of steel pipe hardness testing, static test method, this kind of method test force is applied slowly without impact. Static test methods include brucelli, Rockwell, Vivtorinox, nu Shi, Wechsler and Pasteurella.
Brinell, Rockwell and Vickers test methods are the most widely used, they are the main test methods for steel tube hardness testing.
1) Brinell hardness
In seamless steel tube standard, Brinell hardness is the most widely used, and 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 tubes with harder or thinner steel.
2) Rockwell hardness
The Rockwell hardness test of seamless steel tube is the same as Brinell hardness test. The difference is that it measures the depth of indentation. Rockwell hardness test is a widely used method at present, and HRC is second only to Brinell hardness HB in steel pipe standard. Rockwell hardness can be used to measure metal materials from very soft to very hard. It makes up for the shortcomings of Brinell method. It is simpler than Brinell method and can read hardness value directly from the dial of hardness machine. However, because of its small indentation, the hardness value is not as accurate as that of Brinell method.
3) Vivtorinox hardness
Vickers hardness test of seamless steel tube is also an indentation test method, which can be used to determine the hardness of very thin metal materials and surface layer. It has the main advantages of Brinell method and Rockwell method, and overcomes their basic shortcomings. But it is not as simple as Rockwell method, which is seldom used in steel pipe standard.