Development of application technology of high strength bolts for electric spanners and steel structures in China. In the application of high-strength bolts in steel structures, the most important thing is how to ensure that the tightening axial force of all high-strength bolt connection pairs is designed as far as possible (other metal structures have similar or even higher requirements). This is also our goal to pursue engineers and technicians in transportation, construction and other industries. Excessive axial force (i.e., over-torsion) will lead to bolt fracture or delay fracture for a period of time; too low axial force (i.e., under-torsion) will bring hidden dangers to structural safety.

　　一代电动扳手

　　China's First Generation Electric Spanner我国一代电动扳手以电机的比较大输出扭矩为比较终输出扭矩，通过齿轮传动减速，也就是说，一代电动扳手只能提供比较大的输出扭矩。在1970年代和1960年代,由于相对落后的生产技术在的高强度螺栓,高强度螺栓的联合对同一批次不能提供按照保证转矩系数,所以旋转角的方法只能用于高强度螺栓。当时一代电动扳手的输出扭矩不够大，无法满足高强度螺栓联轴器的要求，只能使用气动冲击扳手。该方法施工过程复杂，精度低。

　　The first generation of electric wrenches in China takes the maximum output torque of the motor as the final output torque, and reduces the speed by gear transmission. That is to say, the first generation of electric wrenches can only provide the maximum output torque. In the 1970s and 1960s, due to the relatively backward production technology of high strength bolts in China, the combination of high strength bolts can not provide the same batch according to the guaranteed torque coefficient, so the rotation angle method can only be used for high strength bolts. At that time, the output torque of the first generation of electric wrenches was not large enough to meet the requirements of high strength bolt coupling, only pneumatic impact wrench was used. This method has complex construction process and low precision.

　　第二代、第三代电动扳手

　　Second and Third Generation Electric Spanners20世纪80年代，我国高强度螺栓连接的生产技术有了很大的提高，高强度螺栓生产厂家可以提供连接的扭矩系数，这为扭矩法应用于高强度螺栓创造了必要的条件。但是，当时还没有固定扭矩电动扳手。为了建设九江长江大桥，有关部门设立了开发第二代定扭矩电动扳手的项目。从上面的情况下,电动扳手的第三代精确的扭矩,扭矩输出可以设置,显示和记录存储、扭曲的过程中还可以转矩系数太小或太大高强度螺栓联接,从而大大提高高强度螺栓联接的精度;也大大简化了施工过程。采用第三代电动扳手拧紧高强螺栓联接副，使我国高强螺栓施工技术向前迈出了一大步，达到了世界水平。2014年11月，参加第三代电动扳手评估会的对其优异表现给予了肯定。

　　In the 1980s, the production technology of high-strength bolt connections in China has been greatly improved. The manufacturers of high-strength bolts can provide the torque coefficient of connections, which creates the necessary conditions for the application of the torque method to high-strength bolts. However, there was no fixed torque electric wrench in China at that time. In order to construct the Jiujiang Yangtze River Bridge, the relevant state departments have set up a project to develop the second generation of fixed torque electric wrenches. From the above situation, the third generation of accurate torque and torque output of electric wrench can be set, display and record storage, distortion process can also eliminate the torque coefficient too small or too large high-strength bolt connection, thus greatly improving the accuracy of high-strength bolt connection; and greatly simplify the construction process. Using the third generation electric wrench to tighten the high-strength bolt connection pair, the construction technology of high-strength bolt in our country has taken a big step forward and reached the world leading level. In November 2014, experts who participated in the Third Generation Electric Spanner Assessment Meeting affirmed its outstanding performance.

　　第三代第四代电动扳手

　　Third Generation and Fourth Generation Electric Spanners虽然第三代电动扳手的性能准确的输出扭矩,高强度螺栓连接副的收紧轴向力也是影响离散的螺栓连接副扭矩系数,所以第三代电动扳手的目的不能实现准确控制收紧螺栓连接副的轴向力。在成功开发第三代电动扳手的基础上，联合开发了第四代电动扳手。这一代电动扳手不仅能精确控制输出扭矩，还能设置、显示和记录高强度螺栓联轴器的拧紧轴力。只要用户在启动前输入螺杆联轴器所需的拧紧轴力，第四代电动扳手运行后即可自动实现所需的拧紧轴力(电流误差为5%)。这种电动扳手暂时称为预紧力可控的电动扳手。
                                 

　　Although the performance of the third generation electric wrench can accurately output the torque, the tightening axial force of the high strength bolt connection pair also affects the discrete torque coefficient of the bolt connection pair, so the purpose of the third generation electric wrench can not accurately control the tightening axial force of the bolt connection pair. Based on the successful development of the third generation electric wrench, the fourth generation electric wrench is developed jointly. This generation of electric wrenches can not only accurately control the output torque, but also set, display and record the tightening force of high strength bolt coupling. As long as the user inputs the required tightening force of the screw coupling before starting, the fourth generation electric wrench can automatically realize the required tightening force (current error is 5%) after running. This electric wrench is temporarily called an electric wrench with controllable preload.

　　第四代电动扳手不仅能控制螺杆接头副达到要求的拧紧轴向力，而且能满足高强度螺栓接头副拧入机体的要求，这在过去是很难做到的。此外，配合第四代电动扳手的螺纹连接副也可重复使用。

　　The fourth generation electric wrench can not only control the screw joint pair to achieve the required tightening axial force, but also meet the requirements of high strength bolt joint pair to screw into the body, which was difficult to achieve in the past. In addition, the threaded connection pair with the fourth generation electric wrench can also be reused.

　　4结论

　　4 Conclusion

　　电动扳手的第四代是目前世界上比较的电动扳手,用于螺杆高强度螺栓连接副,这将使关节的收紧轴向力对更准确,施工更方便,这将彻底改变电动扳手和加捻技术。将这项技术推广到其他行业(比如空客380，它要求严格控制机翼和机身之间每一对连接的轴向力)也将提高螺栓连接的质量。

　　The fourth generation of electric wrench is the most advanced electric wrench in the world. It is used in high strength bolt connection pair of screw. This will make the joint tightening axial force more accurate and construction more convenient, which will completely change the electric wrench and twisting technology. Extending this technology to other industries (such as Airbus 380, which requires strict control of the axial force of each pair of connections between the wing and fuselage) will also improve the quality of bolted connections.