Volgograd State Technical University (Volgograd, Russia):

D. V. Rutskiy, Cand. Eng., Associate Professor, Department “Technology of materials”, e-mail: rutskiy79@mail.ru
N. A. Zyuban, Dr. Eng., Professor, Head pf Department “Technology of materials”, e-mail: tecmat49@vstu.ru

The paper investigates the peculiarities of the internal structure and development of shrinkage and segregation defects in elongated two-piece hot-top 2.99 and 4.07 ton ingots of Cr-Ni-Mo steel. It has been established that sizable shrinkage defects develop in the upper part of the two-piece ingots. These defects develop mostly heightwise and practically do not develop diametrically. This shape of shrinkage defects makes it possible to remove them as holing waste thus making the ingots suitable for production of hollow forgings. The analysis of the distribution of chemical heterogeneity shows that two-piece ingots have greater chemical heterogeneity caused by a larger negative segregation zone. In the two-piece ingots this zone is 1.5 times greater compared with conventional hot-top ingots. The internal surface of two-piece molds is greater than that of conventional geometry molds: the surface area participating in the cooling of 1 kg of melted steel is 1.7 times greater than that in hot-top ingots with the H/D=2 ratio. It results in the growth of the temperature gradient along the height and throughout the mass of the solidifying ingot. The analysis of the simulation of two-piece and conventional geometry ingots has established that a horizontal solidification front line is more typical for twopiece ingots, which results in a faster rate of solid phase propagation and leads to a greater chemical heterogeneity of the cast metal. The study of the structure of elongated two-piece ingots shows that such ingots can be used for the production of hollow longsized forgings.

1. Zhulyev S. I. Proizvodstvo I problemy kachestva kovanykh slitkov (Production and problems of quality of a forge ingot). Volgograd. Volgograd State Technical university (VSTU). 2003. 168 p.
2. Dyudkin D. A. Proizvodstvo stali (Steelmaking). Moscow. Teplotekhnik = Heat Engineer. 2008. 400 p.
3. Efimov V. A. Tekhnologiya sovremennoy metallurgii (Technology of modern metallurgy). Moscow. Novye tekhnologii = New technologies. 2004. 786 p.
4. Pozhivanov M. A., Shahpazov E. Kh., Svyazhin A. G. Vyplavka stali dlya avtolista (Steel melting for automotive sheet). Moscow. Interkontakt Nauka = Intercontact Science. 2006. 166 p.
5. Ubukata T., Suzuki T., Ueda S., Shibata T. Muroran Plant Dehydrogenation in Large Ingot Casting Process. Proceedings of 16th IFM. 2009. P. 52–68.
6. Tomioka A., Nishihara M., Nishiguchi K. Quality of the work roll by new ESR. Proceedings of 16th IFM. 2009 P. 75–84.
7. Dub A. V., Levkov L. Ya, Shurygin D. A., Kriger Yu. N., Markov S. I., Orlov S. V., Dub V. S., Volobuev Yu. S., Kuznetsova K. N., Kisselman S. A. Perspektivy proizvodstva oborudovaniya dlya AES s ispolzovaniem EshP (Prospects of production of the equipment for NES with the use of ESR). Voprosy atomnoy nauki I tekhniki. Seriya: Obespechenie bezopasnosti AES = Problems of nuclear science and equipment. Series: Providing of NPP security. 2014. No. 34. P. 11–18.
8. Dub V. S., Romashkin A. N., Malginov A. N. Main trends in the development of technology for casting steel into ingots. Metallurgist. 2013. Volume 57. Issue 5–6. 2013, P. 487–504.
9. Dub A. V., Dub V. S., Kriger Yu. N., Levkov L. Ya, Orlov S. V., Shurygin D. A., Markov S. I., Dednev A. A., Kisselman S. A., Nekhamin S. M., Chernyak A. I., Bessonov A. V., Kamantsev S. V., Krasovskiy A. V., Sokolov S. O. Elektroshlakovyi pereplav – sposob kardinalnogo povysheniya kachestva i svoistv otvetstvennykh izdeliy v sovremennom mashiniostroenii. Tekhnicheskie trebovaniya i novye resheniya (The electroslag remelting process – way of cardinal improvement of quality and properties of responsible products in modern mechanical engineering. Technical requirements and new decisions). Tyazheloe mashinostroenie = Heavy Machinery. 2012. No. 6. P. 2–6.
10. Medovar L., Fedorovskii B., Stovpchenko A., Zhuravel V., Bogachev D. ESR of Hollow Ingots. New Approaches to a Traditional Problem. Proceedings of 18^th International Forgemasters Market and Technical Conference. Pittsburgh, PA. USA. 2011. P. 183-188.
11. Liu Xi-Hai, Jia Wei-Guo, Wang Jun-Qing, Tang Zuo- Bin, Zhao Lin, Duan Yan-Xiao. Design of 120t Large Electroslag Remelting Furnace and Its Producing Technology. Proceedings of 18^th International Forgemasters Market and Technical Conference. Pittsburgh, PA. USA. 2011. P. 194– 198.
12. Romashkin A. N., Malginov A. N., Tolstykh D. S., Shamrov E. V., Matveeva Yu. L., Ivanov I. A., Dub V. S. Vliyanie geometrii slitka na obyem osevoy rykhlosti v nem (Influence of ingot geometry on the volume of its axial friability). Elektrometallurgiya = Electrometallurgy. 2013. No. 7. P. 36–39.
13. Rutskiy D. V. Zhulyev S. I., Mozgovoy A. V., Titov K. E. Povyshenie kachestva I effektivnosti proizv odstva krupnogabaritnykh polykh izdeliy (Impro vement of quality and production efficiency of large-size hollow products). Technologiya masinostroeniya = Technologu of machine-buiding. 2007. No. 10. P. 8–11.
14. Rutskiy D. V., Zhulyev S. I., Bod K. Yu. Primenenie sdvoennykh stupenchatykh slitkov dlya proizvodstva pokovok (Research of applicability of dual step ingots for production of forgings). Technologiya masinostroeniya = Technologu of machine-buiding. 2007. No. 10. P. 7–9.
15. Zyuban N. A., Rutskiy D. V., Gamanyuk S. B., Konovalov S. S. Kuznechnye slitki: problemy kachestva i novye podkhody (Forge ingots: Problems of quality and new approaches). Chernye Metally = Ferrous Metals, 2014. No. 7. P. 17–21.
16. Rutskiy D. V. Zhulyev S. I., Sivak B. A., Shelukhina Yu. M., Mozgovoy A. V. Stabilizatsiya mekhanicheskikh svoistv v izdeliyakh nyazhelogo mashinostroeniya (Stabilization of mechanical properties in products of heavy mechanical engineering). Tyazheloe mashinostroenie = Heavy Machinery. 2012. No. 12, P. 26–28.
17. Zhulyev S. I., Rutskiy D. V., Bod K. Yu. Razrabotka kuznechnykh slitkov peremennogo secheniya dlya polucheniya polykh srypenchatykh pokovok s povyshennoy odnorodnostyu mekhanicheskikh svoistv (Development of forge ingots of variable section for receiving hollow step forgings with the increased uniformity of mechanical properties). Problemy chernoy metallurgii I materalovedeniya = Problems of ferrous metallurgy and materials science. 2009. No. 1, P. 26–30.
18. Bagmutov V. P.,Zaharov I. N. etc. Volgograd State Technical University: State registration certificate of the computer program “Crystal” computer simulation system. RF No. 2013613206 dated 28.03.2013.