Improvement measures and validity verification of forging crack of a fuel gear pump shell

According to the cause analysis of the shell forging crack, the forging deformation is increased by increasing the forging process, breaking up the accumulation and distribution of the internal chain impurity phase, so that the internal and external deformation of the shell forging is more uniform. In order to further ensure the stability of the follow-up product quality, the heat treatment system is refined to fully release the internal stress.

Small batch (10 pieces) production was carried out with improvement measures, and relevant performance testing and machining were carried out to verify the feasibility of corrective measures. In the trial production batch, one forging was dissected and its performance was tested, two simulated machine drilling and penetration testing were carried out, and three semi finish machining was carried out according to the part drawing. The structure, stress and other properties of the processed forgings were tested.

  1. Low power detection and high power detection

No crack, segregation and non-metallic inclusion, oxide film and coarse crystal ring are found in macrostructure test. The macrostructure of the verification part is shown in Figure 1.

The microstructure has no overburning and a small amount of impurities, as shown in Figure 2.

  1. Detection of chain impurity phase distribution

Figure 3 shows the comparison between the impurity distribution of forgings produced by corrective measures and that of cracked parts. Under the condition of 200 times field of view, the area is larger than 6 μ M2 (to compare the size of impurity phase in forgings produced by different processes, 6 μ The results of impurity phase statistics were compared. It can be seen from the table that the total area of impurity phase in forgings produced by corrective measures is 400.00 μ The area of impurity phase accounts for 0.124%; The total area of impurity phase is 659.92 μ The area of impurity phase accounts for 0.205%; The total area of impurity phase is 462.37 μ The area of impurity phase accounts for 0.144%. Compared with the cracked parts, the area of impurity phase in the corrective parts decreased by 39.4%, and the area of impurity phase in the corrective parts decreased by 13.5%.

  1. Residual stress detection

The residual stress of semi finished parts is detected, and the detection position is the same as that of failed parts, as shown in Figure 4. The final results show that the residual stress of the corrective parts is less than that of the failure parts and normal parts.

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