Investigation of carburising treatment of injector flange in diesel engine

摘要

The applicability of carburising treatment of injector flange in a diesel engine was rninvestigated. Initially, a carburized case structure made of low-carbon (0.23%) steel was approximately modelled by five sub-regions. Then, finite element stress analyses were performed using Abaqus CAE~® software to determine performances of several models, which the thickness of five sub-regions were changed. Examining performances of case thicknesses with respect to load bearing capacity, minimum case thickness value was approximately determined to be 1 mm. After determining this superior case thickness configuration, for real service loading and boundary conditions, FE analyses were repeated to determine the cyclic stress components for a fatigue analysis. Based on the FE results, carburising treatment was applied and superior strength was determined for a case, in which the maximum hardness is 570 ± 20 Hv on surface and 290 ± 25 Hv at depth 1.05 mm from the surface with the condition that heat treatments before and after cold forming were properly applied. Experiments and FE analyses give almost similar results. The result showed that carburising treatment of injector flange provides 8% increase in static load bearing capability with 1 mm case thickness. Additionally, it is realized that the case hardened flange had a reasonable fatigue safety factor. In the real service test with 200 carburized flanges on 50 diesel engines, no failure was observed during 3000 engine operation hours (approximately 2 years).