Fasteners are a kind of mechanical parts that are used for fastening and are widely used. They are also a necessity in our lives. If they are negligent, they will cause more or less loss, from small to large, to large. Safety. Therefore, when using fasteners, you must have a certain understanding of their regulations.
According to rough statistics, there are about 40,000 varieties and millions of fasteners of various forms and specifications at home and abroad, and their use occasions and environment are ever-changing. As the connecting part of the main unit and the components, the fastener bears the basic performance of the main body and the basic functions of the main unit. It must adapt to high temperature, high pressure, low temperature, vibration, corrosion, heavy load, alternating stress and shear resistance. Cut and resist twisting and other occasions. However, the probability of a fastener failure causing an accident is very high, so the materials used to make the fastener must be carefully selected in advance.
1. Common bolts for steel structure connection, high-strength large hex head bolt connection pair, torsion-shear type high-strength bolt connection pair and other fasteners.
2. The high-strength large hexagon bolt connection pair and the torsion-shear type high-strength bolt connection pair shall have the factory-qualified inspection report of the torque coefficient and the tightening axial force (pre-tension), respectively, and accompany the box. When the high-strength bolting connection is used for more than 6 months, the torque coefficient or tightening axial force test shall be repeated according to the relevant requirements and shall be used after passing the test.
3. The high-strength large hex head bolt connection pair and the torsion-shear type high-strength bolt connection pair shall be separately tested for torque coefficient and tightening axial force (pre-tension). The test bolts shall be randomly selected from the bolt batches to be installed at the construction site. Each batch should draw 8 sets of connection pairs for re-inspection.
4, the security level of a building structure, and a span of 40m or more bolts in Steel truss structure, which should be connected to high-strength bolts the surface hardness test, the surface hardness of the high strength bolt should be 8.8 HRC21 ~ 29, 10.9 high-strength bolts shall have a surface hardness of HRC32~36 and shall not have cracks or damage.
5, a common bolt permanently connecting bolts, and its design document or the mass doubt, should be a bolt tensile load minimum physical retest, when reinspection should checks each bolt size 8.
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