What material is better for motor shaft?

Many customers asked when the data performance of the motor fully meets the equipment use requirements, but the motor shaft is easy to bend, and we don't want to replace the motor with a larger size and larger diameter output shaft, how can we solve the problem of the shaft? This involves the motor shaft with what material is better. Today, we will focus on the material model and processing technology of the shaft, so that you can better choose the motor shaft suitable for your own equipment.

What material is better for the motor shaft? 

The motor shaft is generally made of 45# steel. High power motors can be quenched and tempered with 40Cr. High-speed and high-precision motors use 38CrMoAlA. I haven't heard of T8. T8 is characterized by high hardness and good wear resistance after quenching, but it is not torque resistant and easy to break under impact. If the motor shaft made of T8 is really used in the future, the shaft will break when the torque is large;

In addition, the material of the shaft of an ordinary motor has no effect on the electromagnetism, or it doesn't matter whether it has any effect, because the electromagnetic force acts on the iron core of the rotor (specifically, it is the most obvious at the maximum circle of the iron core), not on the shaft. 

The following are the characteristics of shafts of different types of materials:

Heat treatment method of motor shaft parts

① Quenching and tempering heat treatment

45 steel is a medium carbon structural steel with good cold and hot workability, good mechanical properties, low price, and wide sources. Its biggest weakness is low hardenability, and it is not suitable for workpieces with high section size and requirements.

Because 45 steel has low hardenability, 10% brine solution with a high cooling rate should be used. The workpiece shall be quenched thoroughly, but not cold thoroughly. If the workpiece is cooled thoroughly in saltwater, it is possible to crack the workpiece, which is due to the rapid transformation of austenite into martensite when the workpiece is cooled to about 180 °, resulting in excessive structural stress. Therefore, when the quenched workpiece is quickly cooled to this temperature area, the slow cooling method should be adopted. Because the outlet water temperature is difficult to control, it must be operated by experience. When the shaking of the workpiece in the water stops, the outlet water can be air-cooled, and the oil cooling is better. In addition, the workpiece should be dynamic rather than static. It should move regularly according to the geometry of the workpiece. Static cooling medium and static workpiece lead to uneven hardness and stress, resulting in large deformation and even cracking of workpiece.

② Surface quenching, low-temperature tempering

Surface quenching is a heat treatment process that only quenches the surface of the workpiece to change the structure and properties of the surface. It is realized by the combination of rapid heating and immediate quenching and cooling, that is, rapid heating is used to quickly heat the surface of the workpiece to the quenching temperature. When the unequal heat is fully transmitted to the center, it is cooled rapidly to make the surface obtain martensite and harden, The core remains in the non quenched state, that is, the annealed, normalized, or quenched and tempered state with good plasticity and toughness.

③ Low-temperature artificial aging

Heat the parts to 120 ~ 150 ℃ for stress relief annealing, take them out after long-time insulation (5-12 hours), and cool them in the air. The purpose is to reduce the micro stress and machining residual stress in the shaft parts after quenching and prevent deformation and cracking. Low-temperature artificial aging has the advantages of simple operation and low cost. Compared with natural aging, it saves time and removes residual stress more thoroughly.

Transmission structure and working principle of gear shaft

Transmission structure and working principle of gear shaft

There are generally two ways of shaft transmission: universal joint shaft transmission and straight shaft transmission. In practical application, different shaft transmission modes are mainly adopted according to the layout direction of the engine. Generally, when the engine is arranged horizontally, universal joint shaft transmission and straight shaft transmission can be adopted; When the engine is arranged longitudinally, it can only be driven by a straight shaft. This paper briefly introduces the universal joint shaft transmission, which is most widely used in imported motorcycles.

The engine adopts a transversely arranged universal joint shaft structure. A driving gear is installed on the secondary shaft of the transmission, which meshes with the driven gear to change the transmission direction, and transmits the power output by the transmission to the rear wheels through the transmission shaft on the output shaft gear. In order to realize long-distance power transmission, the transmission shaft borrows the hollow tubular space of the rear rocker arm, and a universal joint fork is installed at the rear end of the transmission shaft. The output shaft gear is installed on the half shaft gearbox through the bearing, and the two journals of the universal joint cross shaft are installed on the universal joint fork.

The other two journals of the cross shaft are installed on the universal joint fork at the front end of the transmission shaft, and the rear end of the transmission shaft is provided with long splines. The rear bevel pinion is also provided with a section of the shaft, the front end of the shaft is provided with a spline sleeve, and the long spline at the rear end of the transmission shaft is in this spline sleeve. The rear bevel gear is fixedly connected with the rear wheel hub and meshed with the small bevel gear. In this way, the power of the engine is transmitted to the rear wheel through the driving gear, output shaft gear, universal joint, transmission shaft, bevel gear, and bevel gear, so as to drive the motorcycle forward.


Rotating shaft seal
In petroleum and chemical production, the sealing of rotating shafts of reaction kettle, fermentation tank, compressor, fan, pump and other machinery and equipment is not only a necessary condition to ensure the normal operation of equipment, but also an important link for equipment sealing and anti-virus. There are many types of seals for rotating shaft, such as stuffing box, sealing ring, labyrinth seal, mechanical seal (also known as end face seal), impeller or jet seal with packing seal, magnetic seal, etc.

How to deal with the broken shaft fault of the motor shaft? 

The fracture of the motor journal can be repaired theoretically. Welding and post-weld heat treatment are important links in the whole repair process. Before welding, the original shaft and processed shaft head must be carefully cleaned, and all impurities such as oil that will produce hydrogen must be strictly removed.

J857 electrode with a diameter of 3.2 can be selected for welding. Before welding, the electrode shall be dried at the heat source for 2h and taken at any time to remove the moisture in the electrode. The reverse connection method is adopted for welding on the DC welding machine. Firstly, preheat the motor rotor shaft and processing shaft head by 300 ℃, take them out and lift them onto the roller support, start symmetrical staggered welding, and fill the U-shaped groove layer by layer.

During welding, the current value can be 90 ~ 100, and slow welding can prevent overheating of the rotor shaft. After welding, immediately heat the area within 100 ~ 120 mm of the welding repair position with a gas cutting torch, and constantly rotate the rotor shaft to heat it evenly to avoid deformation. When the heating temperature reaches 500 ~ 600 ℃, hold it for 1h, lift it into a 300 ℃ oven and cool it to normal temperature.