The half shaft of the car is made of 40Cr: 

1. 40Cr is my country's national standard steel grade, and 40Cr steel is one of the most widely used steels in the machinery manufacturing industry; 2. After quality treatment, it has good comprehensive mechanical properties, good low-temperature impact toughness and low notch sensitivity; 3. The quenching effect of steel is good, water quenching can be adjusted to 28-60mm, and oil quenching can be adjusted to 15-40mm. In addition to treatment, this steel is also suitable for cyanide and high-frequency quenching treatment; 4. The cutting performance is better. When the hardness is 174～229HB, the relative machinability is 60%. The steel is suitable for making medium-sized plastic molds.