How to divide the strength grade of bolts
Release Time:
2022-10-21
How bolts are divided into strength grades: The performance grades of steel structure connecting bolts are divided into more than 10 grades, such as 3.6, 4.0, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9. The specific meaning of bolt grades is, for example, bolts of grade 4.8 representing tensile strength. 0.8 represents the ratio of strength divided by tensile strength, that is, the tensile strength of grade 4.8 bolts is 400MPa, and the strength is 400 × 0.8 = 320MPa. Other bolt grades have the same meaning.
How bolts are divided into strength grades:
The performance grades of steel structure connecting bolts are divided into more than 10 grades, such as 3.6, 4.0, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9. The specific meaning of bolt grades is, for example, bolts of grade 4.8 representing tensile strength. 0.8 represents the ratio of strength divided by tensile strength, that is, the tensile strength of grade 4.8 bolts is 400MPa, and the strength is 400 × 0.8 = 320MPa. Other bolt grades have the same meaning.
High strength bolts and ordinary bolts:
High-strength bolts can also be said to be English words. The English translation should be high-strength friction preload bolts. The word friction preload is omitted. It can be seen that the index to measure the performance of bolts is strength. Whether it is tensile strength or yield strength, in the final analysis, it is the allowable stress of the material. Some books say that bolts with a performance grade greater than or equal to 8.8 are called high-strength bolts, but many ordinary bolts we usually see are also 10.9 and 12.9 respectively, and the price is also the price of ordinary bolts. We do not consider the performance level of high-strength bolts, but only illustrate this problem from the perspective of force.
High-strength bolts rely on clamping two parts to increase the maximum static friction force by preloading. For high-strength bolts, they only bear the tensile force and are not affected by the shear force. If the two objects move relative to each other, the design is invalid. The design fails. This is important. This means that the two parts are firmly connected, the same as welding. If they slide, the welding fails. The established mechanical calculation model is inaccurate. Stiffness means that it is just connected and can transmit torque. This is the main point for designers to design high-strength bolts, and it is also the essential difference between ordinary bolts and high-strength bolts.
Grade 8.8 ordinary bolts only represent high strength.
Ordinary bolts rely on their own strength to resist shear forces. From a mechanical analysis point of view, ordinary bolts are hinges in mechanical calculations and can slide. To exaggerate, two objects may slide without tightening. The role of the bolt is only to connect two objects. As long as the bolt is pulled continuously, the two objects can slide.
To sum up, the difference between ordinary bolts and high-strength bolts is the strength of the material.
Related News
What are the classification and use of high-strength bolts?
High-strength bolts are special bolts made of high-quality carbon steel or low-alloy steel. They are called high-strength bolts because of their high strength. High-strength bolt connections have the advantages of simple and fast installation, good mechanical performance, assembly and disassembly, high pressure bearing, safety and reliability, etc. High-strength bolts are a new type of steel structure connection method developed after riveting connection, and have now developed into one of the main means of steel structure connection today. 1. Classification of high-strength bolts High-strength bolts can be divided into two types: large hexagonal head type and torsion shear type in appearance; if they are divided into 8.8, 10.9, 12.9, etc., according to the performance grade, the large hexagonal head high-strength bolts currently used in our country have 8.8 and 10.9 grades, while the torsion shear type high-strength bolt strength bolt is only 10.9 grades. The large hexagonal head high-strength bolt connection pair consists of a bolt, a nut and two washers (the screw head and the nut each have a washer): the torsion shear type high-strength bolt connection pair consists of bolts, nuts and washers. When bolts, nuts and washers form a connection pair, their performance levels must match. 2. According to the connection method, high-strength bolts can be divided into three types: friction connection, tensile connection and pressure connection. Friction connection and pressure-bearing connection are both shear connection. Bolt friction connection trans
Address: No. 8, Danhuagang Bridge South of Yanjiang Road, Xingang Industrial Park, Jingjiang City, Jiangsu Province
FAX：0523-84255089
Micro official website
Copyright 2022 Jiangsu Yonghao High Strength Bolt Co., Ltd. Powered by www.300.cn Changzhou 丨seo