As a widely used standard part, bolts are widely used in all walks of life. Mechanical equipment, vehicles and ships, aviation and railways, construction bridges, electronics and appliances, tools and instruments, etc. can be said to be ubiquitous. Various bolts have different properties. We can use some simple skills to quickly identify which industries these bolts are used in.
First is the name of the bolt. In fact, the name is its standard. For example, when we call it hexagonal bolt, it indicates that it is a certain national standard. If I say it is a socket head cap screw, it refers to another standard. The standards are clarified, and then the specifications. Basically, the size of the bolt is actually two important indicators: the thread diameter and the thread length. Other head sizes are already fixed in the internal and external hexagon standards. When describing the thread, if necessary, the pitch should also be supplemented, especially the distinction between fine teeth and coarse teeth, as well as the difference between British teeth and American teeth.
After knowing the standards and specifications, we need to know the bolt materials. The materials commonly used to produce bolts are stainless steel, carbon steel, copper and aluminum. If it is stainless steel, it is divided into SUS304 and SUS316. Of course, there is also SUS410, which is used to produce self tapping screws. Only 304 and 316 are the most common of all bolts and nuts. If it is carbon steel, it has strength grades of 4.8, 8.8, 10.9 and 12.9. Different grades correspond to different carbon steel materials. Copper and aluminum are relatively simple. Just look at the color.
Next, check whether the surface treatment of bolts is required. At present, the commonly used bolt surface treatment includes: blackening, zinc plating, copper plating, nickel plating, chromium plating, silver plating, gold plating, Dacromet, hot dip galvanizing, etc. The use environment is different with different surface treatment, and the anti-corrosion performance is different. It needs to be selected in accordance with the use environment.
After all these hardware standard parts are selected, it depends on whether the performance parameters of the bolts are consistent with the design. The performance parameters of stainless steel bolts are based on the materials, that is, what are the properties of the materials and what are the properties of the produced bolts, which are fixed when selecting materials. For the performance of carbon steel bolts, it involves the later heat treatment process, so it needs to be standardized. The heat treatment process is mainly carried out for carbon steel bolts. Generally, the heat treatment is required for bolts above grade 8.8. After heat treatment, the hydrogen embrittlement coefficient of bolts of this strength should be paid attention to. These are the quality problems in practical application after the selection of bolt standards. These cannot be observed with the naked eye, so the supplier is required to provide relevant data on the heat treatment and mechanical properties of the bolts during acceptance, and then the designer compares these technical parameters with the technical parameters of the equipment design, so that they can be used with confidence after matching.
