The fixing of expansion screws is to use the shear slope to promote expansion and produce friction and grip force to achieve the fixing effect. The screw has a thread on one end and a taper on the other end. It is wrapped with a steel sheet. There are several cuts on the half of the iron cylinder. They are stuffed into the hole in the wall together, and then the nut is locked. The nut pulls the screw outward and pulls the taper into the steel cylinder. The steel cylinder is expanded and fixed tightly to the wall. It is generally used for fastening guardrails, awnings, air conditioners, etc. on cement, bricks and other materials, but its fixing is not very reliable. If the load has a large vibration, it may loosen, so it is not recommended for installing ceiling fans, etc. Introduce the role, performance level, construction process, construction precautions and advantages of expansion screws. The role of expansion screws.1. The expansion screw is composed of a screw and an expansion tube. The tail of the screw is conical, and the inner diameter of the cone is larger than the inner diameter of the expansion tube. When the nut is tightened, the screw moves outward, and the axial movement of the thread causes the cone to move, thereby forming a large positive pressure on the outer circumference of the expansion tube. In addition, the angle of the cone is very small, so that friction self-locking is formed between the wall, the expansion tube and the cone, thereby achieving a fixing effect; 2. The spring washer on the expansion screw is a standard part. Because its opening is staggered and elastic, it is called a spring washer. The function of the spring washer is to use the sharp corners of the staggered opening to pierce the nut and the flat washer to prevent the nut from loosening; 3. The flat washer is also a standard part. Its function is to evenly distribute the pressure of the nut on the connected parts.The performance grade of expansion screws, performance grade 10.9 high-strength expansion bolts, after heat treatment, can achieve: the nominal tensile strength of the expansion bolt material reaches 1000MPa; the yield strength ratio of the expansion bolt material is 0.9; the nominal yield strength of the expansion bolt material reaches 1000×0.9=900MPa.
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