High Quality Common Rail Diesel /Fuel Injector NozzleDLLA145P574

Analysis of why the injector nozzle stuck in the injectors (part 2)

2.2 Surface roughness and hardness measurement results The surface roughness of the needle valve is measured, and the surface roughness requirement of the needle valve is 61HRC～65HRC for the surface hardness requirement. The roughness of the needle valve with steel stamp number HHM is Ra0.03, Rt0.34, and the surface hardness is 60.4HRC～60.7HRC; the needle valve with steel stamp number HD is Ra0.02, Rt0.37, and the surface hardness is 62.3HRC. The roughness and hardness of the two needle valves submitted for inspection all meet the design requirements. After the nozzle was dissected, the inner hole roughness was measured. The inner hole roughness requirement of the nozzle was 0.05Rt0.8. Valve Ra0.07～1.16, Rt0.82～1.79. The inner hole roughness of the two nozzles submitted for inspection did not meet the design requirements.

2.3 Surface hardness measurement and metallographic analysis results The surface hardness of the needle valve is required to be 61HRC-65HRC, free bainite is not allowed, and the residual austenite does not exceed 5%. The hardness of the needle valve with the initial stamp number HHM is 62.9HRC～63.6HRC, the grain size is 10, and the degree of superheat is 2; the hardness of the needle valve with the initial steel stamp number HD is 62.4HRC～63.4HRC, the grain size is 9, and the degree of superheat is 2. The hardness of the two needle valves all meet the design requirements.