Introduction to the meaning of the performance grade of large hexagonal bolts

The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, among which the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and have been heat-treated (quenching, tempering), commonly known as high-strength bolts, and the rest are commonly referred to as ordinary bolts. The performance grade label of large hexagonal bolts consists of two parts, which respectively represent the nominal tensile strength value and yield ratio of the bolt material.

For example, the bolts with performance grade 4.6 of large hexagonal bolts mean:

1. The nominal tensile strength of the large hexagonal bolt material reaches 400MPa; ??2. The yield strength ratio of the large hexagonal bolt material is 0.6; Grade 10.9 high-strength bolts.

After heat treatment, the large hexagonal bolt material can reach: ??1. The nominal tensile strength of the large hexagonal bolt material reaches 1000MPa; ??2. The yield strength ratio of the large hexagonal bolt material is 0.9; ??3. The large hexagonal bolt material The meaning of the performance grade of bolts with a nominal yield strength of 1000×0.9=900MPa is an international standard. Bolts of the same performance grade have the same performance regardless of the difference in their materials and origins. Only the performance grade can be selected in the design. .

Which areas are steel structure bolts suitable for?

Steel structure bolts are high-strength bolts and also a type of standard parts. The fastening performance is relatively good, and it is used in steel structures and engineering to make the fastening effect. ??Steel structure bolts are divided into torsional shear high-strength bolts and large hexagonal high-strength bolts. Large hexagonal high-strength bolts belong to the high-strength level of ordinary screws, while torsional shear high-strength bolts are improved types of large hexagonal high-strength bolts. For better construction . ??The construction of steel structure bolts must be tightened first and then final tightened. For the initial tightening of steel structure bolts, an impact electric wrench or torque adjustable electric wrench is required; while the final tightening of steel structure bolts has strict requirements, the final tightening of torsional shear steel Structural bolts must use a torsional shear type electric wrench, and final tightening torque type steel structure bolts must use a torque type electric wrench. The large hexagonal steel structure bolts are composed of a bolt, a nut, and two washers.

Types and parameters of steel structure bolts

Steel structure bolts are a type of bolts with high strength. Steel structure bolts are also called high-strength bolts, or high-strength bolt connection pairs. It is a new form of connection developed in the 1950s. The use of steel structure bolt connection has the advantages of convenient construction, good mechanical performance, removable, fatigue resistance, and no loosening under dynamic load, etc. It is a very promising connection method. The steel structure bolt is a kind of high-strength bolt, and it is also a kind of standard part. The fastening performance is relatively good, and it is used in steel structures and engineering to make the fastening effect. In general steel structures, the required steel structure bolts are above grade 8.8, and there are also grades 10.9 and 12.9, all of which are high-strength steel structure bolts. Sometimes the bolts on the steel structure do not need to be electroplated. Just OK. When installing steel structure bolts, the torque wrench needs to tighten the nuts, which makes the steel structure bolts generate a very large and controlled pre-tension force. The same amount of friction force is also generated on the pre-connected parts through the nut and the liner. Under the action of the pre-tension force, a relatively large friction force will be generated along the surface of the connected part. Obviously, as long as the sliding force is less than the friction If the force is sufficient, the parts will not be slid. This is the realization of the connection principle of steel structure bolts.