Influence of centrifuge spindle vibration on black spot defect of diesel engine cast iron cylinder liner

The structure of horizontal centrifuge is simple, and abnormal vibration of centrifuge spindle occurs from time to time. The abnormal vibration (channeling and shaking) of the centrifuge spindle produces disordered power in different directions to the small particles in the solidification process of molten iron, affects the tissue uniformity and aggravates the segregation phenomenon. The research team conducted a test to verify the influence of centrifuge spindle vibration on casting black spot defects.

When the casting black spot defect cylinder liner is cut open to check the section, it can be found that there is uneven distribution of grain size and fine inclusions in the section. During production, check the vibration of the main shaft of the centrifuge, take a sample of all centrifuges, and cut open the inspection section. Some cylinder liners produced by centrifuges with abnormal spindle vibration can be observed with the naked eye from the section. For the cylinder liner section produced by normal centrifugal casting, the grain gradually becomes thinner from the inner wall to the outer wall. The cylinder liner section produced by centrifuge with abnormal spindle vibration shows coarse and fine grain inclusions and irregular distribution, and coarse grains appear in the center of the section and even in the outer wall. Sample the products produced by the centrifuge with irregular distribution of coarse and fine grains and inclusions on the section, and track them during commissioning. The test results are shown in the table.

It can be seen from the test results in the table that the proportion of black spots on the cylinder liner with abnormal spindle vibration of the centrifuge is as high as 36%. In the ideal state, the centrifuge rotates around the rotating shaft (main shaft) in balance. In the process of rotation, the rotating shaft itself does not jump up, down, left and right or move back and forth. At this time, in addition to centrifugal force, the force on each part of molten iron is only its own gravity. The actual situation is that due to the wear of bearings, improper positioning of main shafts, excessive clearance between bearings and main shafts, the main shafts jump up, down, left and right or move back and forth during operation, which is equivalent to adding another irregular power to the solidified molten iron in addition to centrifugal force and its own gravity. Because the molten iron itself has uneven chemical composition, such as uneven diffusion of inoculant and uneven dispersion of alloy elements, this irregular dynamic action acts on the molten iron, and the effect of each part of the molten iron under the action of force is also uneven, and the uneven dynamic action is amplified, resulting in the expansion of the heterogeneity of molten iron structure, Finally, it shows the inclusion and irregular distribution of coarse and fine grains in the cylinder liner section.

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