高强螺栓可分为扭剪型和大六角型两种，国标扭剪型高强螺栓为M16、M20、M22、M24四种，现在也有非国标的M27、M30两种;国标大六角高强螺栓为M16、M20、M22、M24、M27、M30等几种。一般的对于高强螺栓的紧固都要先初紧再终紧，而且每步都需要有严格的扭矩要求。大六角高强螺栓的初紧和终紧都必须使用定扭矩扳手。
High-strength bolts can be divided into two types: torsional shear type and large hexagon type. The national standard torsional shear type high-strength bolts are M16, M20, M22 and M24, and now there are also two types of non-national standard M27 and M30; National standard large hexagon high-strength bolts are M16, M20, M22, M24, M27, M30, etc. Generally, the high-strength bolts should be tightened first and then finally, and each step should have strict torque requirements. Fixed torque wrench must be used for initial and final tightening of large hexagon high-strength bolts.
定扭矩电动扳手的使用:
Use of fixed torque electric wrench:
定扭矩电动扳手既可初紧又可终紧，它的使用是先调节扭矩，再紧固螺栓。
The fixed torque electric wrench can be used for both initial and final tightening. Its use is to adjust the torque first and then tighten the bolts.
