Volgograd State Technical University (Volgograd, Russia)

D. V. Rutskii, Cand. Eng., Associate Professor, Department “Technology of materials”, rutskiy79@mail.ru
N. A. Zyuban, Dr. Eng., Professor, Head of Department “Technology of materials”, tecmat49@vstu.ru
S. B. Gamanyuk, Cand. Eng., Associate Professor, Department “Technology of materials”, gamanuk@mail.ru

Solidification of large ingots is accompanied by development of the defects of shrinkage and segregation origination in these ingots. Such defects can reach significant size, remain in forgings after ingot deformation and lead to metal rejects at fabrication stage. At present time, serious attention is paid to the problems of manufacture of defect-free ingots. Any of such investigations present information about usage of the new technologies providing substantial improvement of ingot quality parameters. These methods make the ingot production process rather more complicated and expensive, especially for the case of fabrication of long hollow forging, what restricts possibility of their wide application. This work proposes the method of ingot production for hollow forgings, allowing to control forming and development of internal axial defects due to local chilling of the ingot head part, and to guarantee their complete removal during forging. It was established during metallographic examinations as well as physical and mathematical simulation that local chilling of the ingot head part leads to acceleration of solidification process practically in the whole ingot volume. Calculation of thermal work of chilling and hot feeder heads has revealed lowering of heat transferred to the body of chilled ingot. It stipulated increase of solidification rate and decrease of chemical heterogeneity in cast metal. Displacement of a thermal center to the axial part of the middle ingot section finalized in optimal location of a shrinkage, having essential length and small diameter; such location provides its guaranteed removal during fabrication of hollow ingot forging.

The reported study was funded by RFBR, according to the research project No. 15-08-08098 А and No. 16-08-01029 А, and tender СП-2015 (СП-4573.2015.1).

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