Volgograd State Technical University (Volgograd, Russia):

Rutskii D. V., Cand. Eng., Ass. Prof., Chair of Materials Technology
Zyuban N. A., Dr. Eng., Prof., Head of Chair of Materials Technology, e-mail: tecmat@vstu.ru; tecmat49@vstu.ru
Gamanyuk S. B., Cand. Eng., Ass. Prof., Chair of Materials Technology
Chubukov M. Yu., Post-graduate, Chair of Materials Technology

The analysis of the standard sizes of forgings, produced at machine building factories, shows that most forgings are hollow. Hollow and elongated ingots, both with and without a hot top, are used to manufacture such forgings.Ingot solidifi cation is accompanied with defect development inside the ingot. These defects can achieve considerable dimensions and fully or partially transfer to the forging after ingot deformation or mechanical treatment. These defects may result in rejecting the forging either during its production or delivery trials. Optical and electronic microscopy methods are used in the paper to investigate the quality of steel 38XH3MФA in a 1.53 ton ingot teemed into a mold with a top cooling unit. In addition, an investigation was carried out to analyze metal quality of hollow forgings fabricated from ingots with a cooled top and a heat insulated hot top unit. A metallographic study and mathematical modeling have established that if ingot top is cooled, solidifi cation occurs faster throughout practically the entire ingot mass and shifts the heat center to the ingot central axial zone. Top cooling results in a more favorable location of the shrinkage cavity which has a considerable length and a small diameter. These factors make it possible to fully remove the cavity during ingot deformation to producea hollow forging. Teeming ingots with a cooled top makes it possible to produce hollow forgings with a higher chemical heterogeneity over the ingot length and cross section; besides, ingot-to-product yield can be increased on the average by 7%.
The reported study was funded by RFBR, according to the research project No. 15-08-08098 А and No. 16-08-01029 А, and № 16-38-60007 мол_а_дк».

1. Tsukanov V. V. Modern steels and technologies in power plant industry. Saint Petersburg : ANO LA «Professional», 2014. 464 p.
2. Durynin V. A., Solntsev Yu. P. Research and improvement of production technology for increasing of the resource of steel products made of high-duty heavy forgings. Saint Petersburg : Khimizdat, 2006. 272 p.
3. Ikeda Y., Morinaka K., Muraoka T. Recent Technological Progress on Large Ingots for Rotor Forgings. 18^th International Forgemasters Market and Technical Proceedings September 12–15, 2011. Pittsburgh, PA, USA. pp. 166–169.
4. Dub V. S., Romashkin A. N., Malginov A. N. et al. Technological development of steel-teeming in ingots. Tyazheloe mashinostroenie. 2012. No. 8. pp. 2–8.
5. By Sang-Hun Oh, Jung Namkung, Seog-Ou, Cho, Dong-Hee Lee. A Study on the Fabrication of a Large Hollow Ingot by CAE : 18^th Int. Forgemasters Market and Technical Proc. (Pittsburgh, PA, USA. September 12–15, 2011). pp. 179–182.
6. Nazaratin V. V., Kobelev O. A., Efimov M. V. et al. Analysis of technologies used to make hollow ingots and prospects for their improvement. Metallurgist. 2013. Vol. 56, Iss. 9–10.
7. Tomioka A., Michio Nishihara, Katsushige Nishiguchi. Quality of the work roll by new ESR. 16^th IFM-2009. pp. 75–84.
8. Dub A. V., Levkov L. Ya., Shurygin D. A. et al. Prospects for production of NPP equipment using electroslag refining. Voprosy atomnoy nauki i tekhniki. Seriya : Obespechenie bezopasnosti AES. 2014. No. 34. pp. 11–18.
9. Rutskiy D. V., Zyuban N. A. Development of defect zones and cast metal structure in elongared two-piece Cr-Ni-Mo steel ingots. CIS Iron and Steel Review. 2015. No. 10. pp. 14–18.
10. Zhulyev S. I., Zyuban N. A., Rutskiy D. V. Steel ingots : problems and new technologies : monograph. Volgograd : VolgGTU, 2016. 176 p.
11. Galkin A. N. Investigation of infl uence of thermal-physics solidification conditions and ingot shape for tubular billets on its agening and distribution of non-metallic inclusions : Dissertation … of Candidate of Engineering Sciences. Volgograd, 2015. 106 p.
12. Zyuban N. A., Rutskiy D. V., Galkin A. N., Gamanyuk S. B., Kosova E. A., Puzikov A. Ya. Ingot mould model for research of ingot crystallization process. Patent RF, No. 141550, IPC B22D7/08. Volgograd State Technical University, 2014.
13. Efimov V. A., Eldarkhanov A. S. Modern technologies of casting and crystallization of alloys. Moscow : Mashinostroenie, 1998. 359 p.
14. Efimov V. A. Casting and crystallization of steel. Moscow : Metallurgiya, 1976. 552 p.
15. Spies H.-J. Verhalten von nichtmetallischen Einschlussen im Stahl. Ed.: V. A. Kudrin. Translated from German by G. N. Elanskiy. Moscow : Metallurgiya, 1971. 129 p.
16. State registration certificate for electronic computer No. 2013613206 on 28.03.2013. Computer simulation system «Crystal». V. P. Bagmutov, I. N. Zakharov, N. A. Zyuban, D. V. Rutskiy, S. B. Gamanyuk. Volgograd State Technical University, 2013.
17. Shamrey V. A. Investigation of ingots with cold top parts and their use for production of hollow forgings: Dissertation of Candidate of Engineering Sciences. Moscow : TsNIIChermet, 2007. 146 p.
18. Shamrey V. A., Zhulev S. I. New form of forging ingot for production of hollow forged products. Metallurg. 2007. No. 11. pp. 54–57.