The fatigue strength of high-strength bolts has always been an indispensable problem. Some data show that the failure of high-strength bolts is generally caused by fatigue failure, and there is basically no sign of fatigue failure of bolts. Therefore, it is easy to cause major safety accidents when fatigue failure occurs. So, can heat treatment improve the properties of master material? What is the fatigue strength increase? As the application requirements of high-strength bolts are getting higher and higher, it is very important for maijin to increase the fatigue strength of bolt materials through heat treatment. 1. The place where the fatigue crack starts is called the source of fatigue. The source of fatigue is particularly sensitive to the microstructure of the nut and can cause fatigue cracks on a very small scale. 2. Within 3 to 5 grain sizes, product quality problems on the surface of high-strength bolts are the main source of fatigue, and most of the fatigue originates from the surface or subsurface of high-strength bolts. There are several factors that may contribute to the fatigue strength of aluminum alloys. The results show that the fatigue crack sites are dislocations, surface inclusions or two-phase particles, cracks, which are related to the complex and ever-changing structure of the raw materials. If the microstructure can be improved after heat treatment, the fatigue strength of high-strength bolt materials can be improved to a certain extent. Effect of heat treatment on fatigue strength When studying the fatigue strength of high-strength bolts, it is found that the static load bearing capacity of high-strength bolts can be improved by increasing the hardness, but the fatigue strength cannot be improved by increasing the hardness. Since the vacant ground stress of high-strength bolts will also cause more stress concentration, for samples without stress concentration, increasing the hardness can improve the fatigue strength. 1. Strength is an index to test the strength and softness of metal composite materials. That is also the level of material resistance to being pressed into a harder object. Strength also reflects the strength and ductility of metal materials. 2. Stress concentration on the surface of high-strength bolts will also reduce its surface compressive strength. When the high-strength bolts are subjected to alternating dynamic loads, micro-deformations and repairs continue to occur at the vacant stress concentration locations, and the stress is much higher than that of the non-stress concentration locations, which can easily cause fatigue cracks.