The crankshaft, whether it is an automobile engine crankshaft, a marine engine crankshaft or an industrial pump crankshaft, is subjected to the combined action of alternating bending and alternating torsional loads during the rotation process. The dangerous sections of the crankshaft, especially the transition fillet between the journal and the crankshaft. At this point, the crankshaft is often fractured due to the high concentration of stress. Therefore, the service conditions require the crankshaft to have sufficient strength to ensure that the crankshaft does not break during operation. At present, changing the fatigue resistance of crankshaft by shot peening has been widely used in a wide range, and the effect is quite satisfactory.

Compared with the defects of the traditional rolling process, that is, due to the limitation of the crankshaft processing technology, the rounded corners of each journal are difficult to match the rollers, which often causes the phenomenon of gnawing and cutting of the rounded corners, and the crankshaft after rolling is deformed greatly. ,not effectively. The mechanism of shot peening is to use shot particles with a strictly controlled diameter and a certain strength. Under the action of high-speed air flow, a flow of shot is formed and continuously sprayed on the metal surface of the crankshaft, just like hammering with countless small hammers, so that the surface of the crankshaft is hammered. Produces extremely strong plastic deformation, forms cold work hardening layer. In simple terms, because the crankshaft is subjected to various mechanical cutting forces during processing, the stress distribution on its surface, especially at the transition fillet of the crankshaft section changes, is extremely uneven, and it is subjected to alternating stress during work, so it is easy to Stress corrosion occurs and the fatigue life of the crankshaft is reduced. The shot peening process is to offset the tensile stress that the parts will be subjected to in the subsequent working cycle by introducing a pre-compression stress, thereby improving the fatigue resistance and safe service life of the workpiece.

In addition, crankshaft forging blanks are directly made from steel ingots or forged from hot-rolled steel. If the forging and rolling processes are not properly controlled, there will often be component segregation in the blanks, coarse grains of the original structure, and unreasonable distribution of internal structures. and other metallurgical and organizational defects, thereby reducing the fatigue life of the crankshaft, and the strengthening process can refine the organizational structure and significantly improve its fatigue performance.