- Smelting
The main shaft steel should be smelted using electric furnaces, with refining outside the furnace and vacuum degassing.
2.Forging
The main shaft should be directly forged from steel ingots. The alignment between the axis of the main shaft and the center line of the ingot should be maintained as much as possible. Sufficient material allowance should be provided at both ends of the ingot to ensure that the main shaft has no shrinkage holes, severe segregation, or other significant defects. The forging of the main shaft should be performed on forging equipment with sufficient capacity, and the forging ratio should be greater than 3.5 to ensure full forging and uniform microstructure.
3.Heat treatment After forging, the main shaft should undergo normalizing heat treatment to improve its structure and machinability. Welding of the main shaft is not allowed during processing and forging.
4.Chemical composition
The supplier should conduct melt analysis for each batch of liquid steel, and the results should comply with relevant regulations. The requirements for hydrogen, oxygen, and nitrogen content (mass fraction) in the steel are as follows: hydrogen content not exceeding 2.0X10-6, oxygen content not exceeding 3.0X10-5, and nitrogen content not exceeding 1.0X10-4. When there are special requirements from the buyer, the supplier should conduct finished product analysis of the main shaft, and specific requirements should be specified in the contract or order. Deviations within allowable limits for finished product analysis are permitted if specified by relevant regulations.
5.Mechanical properties
Unless otherwise specified by the user, the mechanical properties of the main shaft should meet the relevant requirements. The Charpy impact test temperature for 42CrMoA main shaft is -30°C, while for 34CrNiMoA main shaft, it is -40°C. The Charpy impact energy absorption should be verified based on the arithmetic mean of three specimens, allowing one specimen to have a test result lower than the specified value, but not less than 70% of the specified value.
6.Hardness
The uniformity of hardness should be inspected after performance heat treatment of the main shaft. The difference in hardness on the surface of the same main shaft should not exceed 30HBW.
7.Non-destructive testing General Requirements
The main shaft should not have defects such as cracks, white spots, shrinkage holes, folding, severe segregation, or severe accumulation of non-metallic inclusions that affect its performance and surface quality. For main shafts with center holes, the inner surface of the hole should be inspected, which should be clean and free from stains, thermal spalling, rust, tool fragments, grinding marks, scratches, or spiral flow lines. Smooth transitions should exist between different diameters without sharp angles or edges. After quenching and tempering heat treatment and rough turning of the surface, the main shaft should undergo 100% ultrasonic flaw detection. After precision machining the outer surface of the main shaft, magnetic particle inspection should be carried out on the entire outer surface and both end faces.
8.Grain size
The average grain size of the main shaft after quenching and tempering should be greater than or equal to 6.0 grades.
Post time: Oct-09-2023
