Study the Effects of the Cryogenic Method Using Liquid Nitrogen on Fittings in Assembly Process

Cryogenics is a field that involves producing, storing, transporting, and using materials at freezing temperatures. One application of this technology is in the shrinkage fitting process, where coolant materials like liquid nitrogen are used to reduce the dimensions of parts so that they can be joined together. This technique is often utilized in sub-assemblies to create a strong fit between the internal and external surfaces of components, which eliminates relative movement between parts, allowing force to be directly transferred from one part to another. In a recent study, we investigated different methods for fitting bush and axle parts with precise dimensions. Cryogenic, pressing, and thermal methods were utilized for assembly fitting. The cryogenic and thermal methods utilized contraction and expansion of parts for assembly fitting, while no dimensional changes occurred in press fitting.  Results from the study showed that the cryogenic method required less force for the assembly and disassembly of parts, and the surface quality of the parts after disassembly was better compared to the other methods. Metallographic tests demonstrated that the microstructure of the parts did not change, and impact tests showed that there was no decrease in the toughness of the parts after the cryogenic operation. Based on these findings, the researchers concluded that the cryogenic method is an excellent technique for fitting SAE4140 Steel parts.