Medium carbon steel shall be used as the material of automobile transmission shaft and transmission shaft suspension.

1. Low carbon steel has good plasticity, but low strength and hardness, and good weldability. It can be cold pressed and used to manufacture various standard parts, shaft sleeves, containers, etc.

2. High carbon steel has poor plasticity, high hardness, poor fatigue strength and poor machinability, resulting in insufficient toughness and easy fracture of shaft parts. This kind of steel is suitable for

manufacturing static pressure bearing and wear-resistant parts, such as heavy-duty rails and rollers. After proper heat treatment, it can also be made into spring, steel wire rope and other parts requiring high

hardness and high wear resistance.

3. The main function of the automobile transmission shaft is to support the rotating body and transmit power. Under the working condition, it generally bears alternating torque and tension and compression load, and

the journal and key components bear large friction and wear. The main failure modes are fracture and local excessive wear, and the fracture modes include fatigue fracture and overload fracture.

Therefore, when selecting materials, it is required that the materials have sufficient strength, rigidity and certain toughness, good wear resistance, high fatigue strength and good processability. In other words, the

spindle is required to have good comprehensive mechanical properties.

4. After proper heat treatment (quenching and tempering, surface quenching, carburizing, etc.), medium carbon steel can obtain better comprehensive mechanical properties such as core toughness and surface wear

resistance.

Alloy quenched and tempered steel (belonging to medium carbon steel) is recommended. Ordinary quenched and tempered steel has poor hardenability and low mechanical properties. It is only suitable for parts with small

size and light load. The alloying elements in the alloy quenched and tempered steel can improve the hardenability, obviously enhance the surface hardening effect of heat treatment such as quenching, and do not reduce

the core toughness. Alloy quenched and tempered steel has high strength, high wear resistance and good plasticity and toughness after heat treatment (quenching and tempering, quenching and tempering), that is, it has

good comprehensive mechanical properties.