The mechanical function requirements of bolts and nuts are different
① The mechanical function of the nut mainly depends on the hardness of the nut, the height of the nut and the wall thickness of the nut. Therefore, the requirements for the data are not high. Of course, the higher level data should also be used if the nut has the requirements for the durability, for example, the higher level data are required for the chemical fastener nut.
② The higher the functional grade of the bolt, the higher the strength. The lower the tempering temperature, the lower the strength. However, it can't meet the requirements of plasticity and durability. In the fastener testing, brittle fracture is judged as unqualified. The steel structure bolt also has higher tensile strength, which is to ensure the plasticity and durability of the bolt.
