DOI: 10.52150/2522-9117-2026-40-032
M. I. Medvediev1, D. Sc. (Tech.), Senior Researcher, ORCID 0000-0002-1230-420X
A. V. Krasiuk2, Production Director, ORCID 0009-0009-8354-687X
O. M. Kuzmina1,*, Ph. D. (Tech.), Assoc. Prof., ORCID 0000-0003-0794-0583
Yu. O. Hladkyi3, Engineer, ORCID 0009-0003-1051-2587
B. I. Kvak1, Ph. D. Student
D. O. Reviakin1, Ph. D. Student
Yu. V. Nytkin1, Ph. D. Student
1 Ukrainian State University of Science and Technologies
2 PJSC “CENTRAVIS PRODUCTION UKRAINE”
3 State Enterprise “State Research and Production Enterprise “Pavlograd Chemical Plant”
* Corresponding author: o.m.kuzmina@ust.edu.ua
THERMAL STATE OF TUBE BILLETS DURING PREPARATORY OPERATIONS OF HOT EXTRUSION OF NICKEL ALLOYS
Abstract. In the manufacturing process of seamless nickel-based alloy tubes by hot extrusion on horizontal hydraulic presses, the formation of surface defects remains a significant and pressing technological problem. One of the main causes for their occurrence is the instability of the temperature-velocity state of the tube billets at various stages of the technological process. Temperature deviations from the optimal narrow range of maximum technological plasticity lead to a rapid decrease in the metal’s deformability, an increase in initial stresses, and a deterioration in the overall quality of the finished tube products. This problem is particularly acute during the processing of the heat-resistant 602CA alloy, which is characterized by high sensitivity to thermal fluctuations and limited technological plasticity. The purpose of this study is to establish the fundamental regularities of changes in the temperature fields of heat-resistant 602CA alloy tube billets at the main stages of their preparation, transportation, and hot extrusion using protective glass lubricants on press installations with capacities of 16.0 and 31.5 MN. The research methodology is based on a comprehensive analysis of the actual industrial production process, direct experimental temperature measurements using thermoelectrodes, as well as mathematical modeling and the use of a system of analytical and semi-empirical relationships to calculate step-by-step temperature losses. The paper details the heat balance at five key stages: transportation of the billet from the induction heater to the lubrication table, application of the protective glass lubricant, transportation of the coated billets to the press, holding in the container before extrusion, and the actual extrusion, taking into account heat transfer through air gaps, wall thickness, and interaction with the tool. As a result of the work performed, it has been established that the total temperature decrease of the billets during auxiliary and transport operations is inversely proportional to the wall thickness of the resulting hollows. In the studied range of wall thicknesses from 40 to 120 mm and initial heating temperatures from 1050 to 1250 °C, the obtained dependence is close to linear. The developed mathematical model and proposed engineering calculation methodology allow for a scientifically justified selection of the glass lubricant’s viscosity characteristics (optimally within the range of 80–100 Pa·s) according to the actual temperature regime of deformation. The practical value of the results has been confirmed under industrial production conditions: the implementation of the developed methodology during the production of a batch of 120 tubes made of the heat-resistant 602CA alloy ensured stable tool protection, the complete elimination of surface defects, an improvement in the overall quality of the finished tube products, and a significant reduction in the defect rate.
Key words: hot extrusion, nickel-base alloys, tube billets, thermal regime, heat balance, glass lubricant, billet cooling, extrusion, surface defects, plasticity.
For citation: Medvediev, M. I., Krasiuk, A. V., Kuzmina, O. M., Hladkyi, Yu. O., Kvak, B. I., Reviakin, D. O., & Nytkin, Yu. V. (2026). Thermal state of tube billets during preparatory operations of hot extrusion of nickel alloys. Fundamental and applied problems of ferrous metallurgy, 40, 548-561. https://doi.org/10.52150/2522-9117-2026-40-032
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Рукопис надійшов до редакції / Received 01.04.2026
Рекомендовано до друку / Accepted 28.05.2026
Опубліковано / Published 30.05.2026
