Vickers hardness is expressed as "hardness value test force test force holding time", such as the hardness value maintained under the test force is the impact toughness. The ability of metal materials to resist impact loads without being damaged is to evaluate the brittle fracture tendency of materials under impact loads, which is reflected by impact toughness. Impact toughness is usually measured by Charpy pendulum impact test. Charpy pendulum impact test is to place a notched specimen of specified geometric shape between two supports of the testing machine, with the notch facing away from the striking surface, and the pendulum falls from a certain height, and the specimen is broken under one impact. In this process, the absorption of the specimen is called impact absorption, which is indicated by . There are two commonly used specimen notches: type and type notch, and the measured impact absorption is expressed as and respectively. For example, represents the impact absorption of the type notch impact specimen under the pendulum blade. The greater the impact absorption, the better the impact toughness of the material. Fatigue strength Many mechanical parts such as the crankshaft, connecting rod, gear, spring, etc. of the engine work under alternating loads. The so-called alternating load refers to a load whose magnitude and direction change periodically over time. The phenomenon that parts suddenly break after working for a long time under alternating loads is called fatigue.

The relationship curve between the alternating stress and the number of cycles of Stainless Steel Weld Fittings is called the stress life curve. It can be seen from the curve that when the stress is lower than a certain value, the sample can withstand infinite cycles without damage. This stress value is called fatigue strength or fatigue limit, which is marked with a table. In fact, it is impossible to achieve an infinite number of alternating load tests. Generally, ferrous metals take the maximum cyclic stress that can withstand when the number of cycles is the fatigue strength, and non-ferrous metals such as steel take times. In order to improve the fatigue strength of parts, stainless steel pipe fittings can adopt the structural shape of parts, reduce the surface roughness value of parts, improve the surface processing quality and apply chemical heat treatment, surface quenching, shot peening, surface rolling and other surface strengthening treatment methods.

The evaluation of the high-temperature mechanical properties of stainless steel pipe fittings metal materials, on the basis of room temperature mechanical properties, also needs to add two factors: temperature and time. The mechanical properties of metals at high temperatures include high-temperature strength, also known as thermal strength and hot hardness.