The method of distinguishing the true and false of high-strength national standard bolts mainly depends on 5 aspects:
1. Look at the logo, the box of general bolts has a logo. Divided into three levels: 8.8, 10.9, and 12.9. Generally, hexagonal bolts do not have a grade mark on the hexagonal plane, which is an ordinary grade. High-strength bolts generally have strength indications. Such as: 8.8; But note that there are too many fake and inferior products nowadays, and we should also pay attention to the purchase channels and purchase inspection.
2. In general, the grade of hexagon socket bolts is relatively high. The reason is that the hexagon socket of the hexagon socket bolt is generally required to be used after heat treatment. The materials that can be treated to increase the hardness are quenched and tempered steel, and the quenched and tempered steel is quenched and tempered. High mechanical strength afterwards;
3. Non-galvanized high-strength bolts are generally black. The black outer layer is an oxide layer formed by artificial processing, which is called blackening in the industry. It is a protective layer formed by using strong alkaline substances to corrode the metal surface, which can resist oxidation. There is also a process called hair orchid, whose function and principle are the same as above. Therefore, high-strength bolts generally will not rust!
4. The simplest empirical judgment: throw it under the ground, listen to the sound, the high-intensity sound is brittle, the sound is very bright, it is strip steel, use a saw blade and other hard tools to scratch the test, the surface hardness of the high-strength bolt is relatively ordinary The surface hardness of the bolt is greater.
5. The problem of tempering, the general high-strength material is not tempered at 8.8, and some merchants may not temper and sell to customers as 12.9 or 10.9. The way to distinguish is to see, in the sun, no tempering It’s the most basic common sense.