Analysis on forging crack of a fuel gear pump shell

Fuel gear pump is a kind of product that relies on the change of working volume formed between the pump shell cavity and meshing gear to realize fuel delivery and pressurization. The shell is a key part, which has high requirements for material density, strength and structure. It is often cast with steel and aluminum alloy with better casting performance, or processed with aluminum alloy forgings with better forging performance. The shell is made of 2A14 forged aluminum alloy. Aiming at the crack problem of the shell in the semi finishing process of the 8-shaped hole in the gear cavity, the failure analysis is carried out. Finally, the cause of the failure is determined, and the corresponding improvement measures are formulated to improve the quality stability and use reliability of the shell.

During the processing of jzp1704073 batch (43 pieces), jzp1704073-2 batch (53 pieces) and jzp1704013 batch (41 pieces) forging shells, it was found that 5 shells had visible cracks at the position of 8-shaped hole in the gear cavity, and the location and shape of the cracks were the same, as shown in the figure.

The cracking fault of the forging of a certain type of fuel oil gear pump shell occurred in the semi finishing process of the 8-shaped hole in the gear cavity. Through analysis, it is related to the distribution of chain impurities and large residual stress in the shell. By optimizing the forging process, adjusting the heat treatment after forging and other measures, and verified by small batch processing, the size of impurity phase is reduced, its distribution is more dispersed, and the stress in the shell is reduced.