The working principle of the torque wrench is that after the motor is decelerated by the planetary gear mechanism, the power is transmitted to the impact head, and the two convex heads of the impact head drive the pull shaft to rotate through the pull shaft claw, and the pull shaft completes the power output.

那么扭力扳手使用一段时间后不可避免会出现输出动力下降的现象，随着扳手的使用时间的增加，输出动力将继续下降，直无法工作。

Then the torque wrench will inevitably decline in output power after a period of use. With the increase of wrench use time, the output power will continue to decline until it can not work.

技术人员通过对电动扭力扳手的解体观察，发现所有使用过的扭力扳手，其扳轴工作面无一例外地发生了严重磨损。磨损后的工作面是与原工作面成大约45度角的一个斜面，这个斜面在工作中将使作用在扳轴上的冲击力分散。冲击力分散后，扭力扳手内部各部件的受力情况也随之改变。

The technicians found that the working face of the wrench shaft of all the used torque wrenches was severely worn without exception through the disassembly and observation of the electric torque wrench. The worn working face is an inclined plane with an angle of about 45 degrees with the original working face, which will disperse the impact force acting on the wrench shaft. After the impact force is dispersed, the stress situation of the internal parts of the torque wrench will also change.

通过以上的观察结论，我们找出了电动扳手失效的主要原因-------扳轴工作面的严重磨损。所以说要有效延长电动扳手的使用寿命，就一定要磨损问题，并且由于扳轴磨损比冲击头要更严重，所以，扳轴磨损的问题是关键。若此问题得以，冲击头磨损问题也就迎刃而解了。将整体式的扳轴改为拆分式的，扳轴的工作面可以拆卸，在使用一段时间后，可视其磨损情况进行更换。活动工作面可单独选用适合的材料，通过合理的加工工艺过程，达到较高的机械性能。

Through the above observation conclusion, we find out the main cause of the failure of the electric wrench - the serious wear of the working face of the wrench shaft. Therefore, in order to effectively extend the service life of the electric wrench, it is necessary to solve the problem of wear, and since the shaft wear is more serious than the impact head, the shaft wear is the key. If this problem can be solved, the problem of impact head wear will be solved. Change the integral pull shaft to the split type, and the working surface of the pull shaft can be disassembled. After a period of use, it can be replaced according to its wear condition. Suitable materials can be selected independently for the movable working face, and high mechanical properties can be achieved through reasonable processing process.

因此选用高碳钢，进行先淬火后中温回火的热处理工艺。这样加工后的活动工作面既有较高的硬度又有一定的韧性，使其在经受冲击时不会发生断裂，且可以进行大批量的加工，一次加工即可满足长期更换的使用要求，非常方便。而电动扳手失效的问题也就迎刃而解。

Therefore, high carbon steel is selected for the heat treatment process of first quenching and then medium temperature tempering. In this way, the working face after machining has high hardness and certain toughness, so that it will not break when it is impacted, and can be processed in large quantities. One processing can meet the use requirements of long-term replacement, which is very convenient. And the problem of electric wrench failure is solved.