Nizhny Novgorod State Technical University named after. R. E. Alekseev, Nizhny Novgorod, Russia

E. I. Yarovaya, Cand. Eng., Associate Prof., Dept. of Metallurgical Technologies and Equipment, e-mail: helyar@yandex.ru
I. O. Leushin, Dr. Eng., Prof., Head of the Dept. of Metallurgical Technologies and Equipment, e-mail: igoleu@yandex.ru

Russian Federal Nuclear Center of the All-Russian Research Institute of Experimental Physics “Research Institute of Measuring Systems named after. Yu. E. Sedakov”, Nizhny Novgorod, Russia
A. Yu. Gusev, Deputy Chief Designer - Head of Branch Department, e-mail: algus_76@mail.ru

Based on the analysis of the change in the strain-stress state of the casting "hub" made of 30KhNML steel formed in sand-clay moulds (SCM) and from cold-hardening mixtures (CHM), it was found that the SCM process is more sensitive to cracking. Stresses in the casting cooled in the SCM-form in the zone of ultimate plastic deformations of steel are higher than in the CHM-form, temperature fluctuations in the volume are 10–15 -С (for SCM), 8–10 °С (for CHM), crack failure is 1–1.5 %. It has been found that these fluctuations can be due to profitable structures in the upper part and the gap between the contact surfaces of the casting and the mold (up to 0.5 mm), which affect heat transfer. Critical stresses in metal were determined at different cooling rates of 0,1–0,35 °С/s in the range of 1480–500°С. Possibility of reducing crack formation is considered based on the analysis of three parameters: cooling rate, internal stresses, heat transfer. For the casting "hub" made of 30KhNML, thermoregulation is necessary, which eliminates temperature differences, shrinkage stresses and cracks. Installation of thermostatic elements, which in the ductility interval provide uniform cooling rate (less than 0,25 °С/s), contact surface corresponding to casting geometry; have low coefficient of linear expansion and thermal conductivity is the solution to the problem.

1. Chernyshov E. A., Evstigneev A. I., Evlampiev A. A. Foundry defects. Reasons for formation. Prevention and correction methods. Moscow : Mashinostroenie, 2008. 282 p.
2. Monroe C., Beckermann C. Development of a hot tear indicator for steel castings. Material Science and Engineering: A. 2005. Vol. 413-414. pp. 30–36.
3. Stradomski Z., Stachura S., Stradomski G. Fracture mechanisms in steel castings. Archives of Foundry Engineering. 2013. Vol. 13, Iss. 3. pp. 88–91.
4. Shibeev E. A., Moskvin I. P., Tanakova Yu. E. Influence of mixture compliance on casting defects in the form of cracks. Omskiy nauchny vestnik. 2017. No. 6 (156). pp. 19–23.
5. Chernyshov E. A. Formation of steel castings under external and complex influence. Nizhny Novgorod : Izdatelstvo NGTU, 2007. 199 p.
6. Isagulov A. Z., Ibatov M. K., Medvedeva I. E., Malashkevichute-Briyan E. I. et al. The use of internal refrigerators at lost foam casting. Trudy universiteta. 2021. No. 4 (85). pp. 73–77.
7. Boldin A. N. et al. Foundry molding materials. Molding, core mixtures and coatings: reference book. MGTU imeni N. E. Baumana. Moscow : Mashinostroenie, 2006. 507 p.
8. Zhukovskiy S. S. et al. Molding materials and mold technology : reference book. Moscow : Mashinostroenie, 1993. 431 p.
9. GOST R 53464–2009. Metal and alloy castings. Dimensions and mass tolerances and machining allowances. Introduced: 01.07.2010.
10. Lukashik K. A., Burtsev D. S., Ponomarev A. A., Solokhnenko V. V. Development of ideas about accuracy formation of castings obtained by casting into molds from cold-hardening mixtures. Zagotovitelnye proizvodstva v mashinostroenii. 2019. Vol. 17. No. 9. pp. 387–389.
11. Batyshev A. I., Batyshev K. A. Formation of hot cracks in steel castings depending on solidification conditions. Part IV. Liteinoe proizvodstvo. 2018. No. 1. pp. 12–14.
12. Ivanov M. A., Shvetsov V. I. Influence of the alloy cooling rate on the process of crack formation in castings. Lityo i metallurgiya. 2013. No. 3 (72). pp. 106–108.
13. Kuzov S. S., Makarenko K. V., Dmitrieva N. V. Analysis of influence of chemical composition of steel on formation of hot cracks in castings. Liteinoe proizvodstvo. 2018. No. 2. pp. 17–19.
14. Timofeev G. I. Mechanics of alloys during crystallization of ingots and castings. Moscow : Metallurgiya, 1977. 160 p.
15. Samoilovich Yu. A., Timoshpolsky N. L., Mandel V. I. Indicators of ductility of carbon and alloy steel at elevated temperatures (review). Lityo i metallurgiya. 2006. No. 1 (37). pp. 93–96.
16. Santillana B., Eskin D. G., Boom R., Katgerman L. The 3rd International Conference on Advances in Solidification Processes. IOP Conf. Series: Materials Science and Engineering. 2011. Vol. 27. pp. 1–6.
17. Davies G. J. Solidification and casting. London : Applied Science Publishers LTD, 1973. 206 p.
18. Desnitskaya L. V., Desnitsky V. V., Matveev I. A. Accounting for the stress-strain state of crystallizing steel castings in their production technology. Liteinoe proizvodstvo. 2019. No. 4. pp. 6–8.
19. Balandin G. F. Fundamentals of the casting formation theory. Moscow : Mashinostroenie, 1979. 335 p.
20. Thermophysical properties of substances : reference book. Edited by professor N. B. Bargaftik. Moscow; Leningrad : Gosenergoizdat, 1956. 367 p.
21. Ilyichev M. V., Mordynsky V. B., Tereshonok D. V., Tyuftyaev A. S. et al. Experimental determination of the dependence of the thermal conductivity coefficient of steel on temperature. Teplofizika vysokikh temperatur. 2015. Vol. 53. No. 2. pp. 193–198.
22. Ivanov M. A., Shvetsov V. I., Volosatova E. L., Izotov D. V. Development of the theory of crack resistance of castings. Vestnik Yuzhno-Uralskogo gosudarstvennogo universiteta. Seriya: Metallurgiya. 2011. No. 36 (253). pp. 48–50.