Tula State University (Tula, Russia):

A. S. Yamnikov, Dr. Eng., Prof., Dept. “Machinebuilding Technology”, E-mail: yamnikovas@mail.ru

JSC “Tulamashzavod” (Tula, Russia):
L. L. Safarova, Technologist, Post-Graduate, E-mail: l.bashkirceva@mail.ru

The widespread use of cast iron castings for workpieces of parts with a complex shape, subjected to high thermal and mechanical stresses during operation, has been explained. A review of domestic and foreign literature is presented, showing the interest of researchers in improving the chemical composition of special cast irons and the influence of individual components on the heat resistance and wear resistance of cast iron parts. It is noted that the heterogeneity of the structure of castings results in susceptibility to changes in their size and shape obtained after the final machining of critical surfaces. The works of Russian scientists are proposed, offering to carry out operations on aging workpieces to stabilize their size and shape. The results of the study of the density distribution over the cross section of a cylinder casting are analyzed using X-ray computed tomography of a diesel engine cylinder, conducted by employees of JSC “Tulamashzavod”, which showed that the density of the metal in the casting varies in a range of 6.75 ÷ 7.25 g/cm³. The influence of the method of performing the natural aging operation on the accuracy of the part was established. The results of changes in dimensional accuracy after applying two variants of natural aging to a batch of Cylinder parts were presented: natural aging for six months, stabilizing tempering before finishing machining, waiting time of parts for three days after the final honing and natural aging for six months, waiting time of parts within 12 days after the final honing. Measurements were made in four sections (eight points in each section) according to a calendar schedule corresponding to casting aging technology. It was established that in both aging variants, the change in the size of the finished part decreases from 3 ÷ 10 μm without aging to 0 ÷ 5 μm. Based on the studies, JSC Tulamashzavod decided to carry out natural aging of the workpieces within six months and stabilizing tempering before the operation of honing the workpieces for the Cylinder parts.

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