Volgograd State Technical University (Volgograd, Russia):

N. I. Gabelchenko, Cand. Eng., Associate Prof., Dept. “Machines and technology of casting production”
A. A. Belov, Senior Lecturer, Dept. “Machines and technology of casting production”, E-mail: aa-belov@bk.ru
N. A. Kidalov, Dr. Eng., Prof., Head of Dept. “Machines and technology of casting production”, E-mail: mitlp@vstu.ru

Lomonosov Moscow State University (Moscow, Russia):
A. I. Gabelchenko, Junior Scientific Researcher

The work is devoted to improvement of mechanical properties of iron castings via adjusting of the cooling rate without introduction of alloying additives. The new technological solution is suggested; it can be easily adapted to a casting technology. This solution is based on variation of the cooling rate of iron castings within structurally sensitive solidification intervals. For this purpose, the casting mould was initially cooled after pouring, then heated and cooled again. Cooling of the mould during the period of primary austenite crystal forming led to increase of dendrite crystallization rate and was executed using compressed air. Retarding of the cooling rate during the period of eutectic transformation was provided by the mould heating via burning of exothermic carbon-containing additives introduced in a facing layer of sand-clay moulding mix. Burning reaction is accompanied by heat extraction, what steeply retarded the cooling rate within the interval of eutectic transformation. Consequent acceleration of castings cooling within the interval of eutectoid transformation was achieved via repeated air blowing through a worked reaction layer. Adjusted cooling of iron castings allowed to provide the most favourable solidification conditions, taking into account strictly individual requirements for each structurally sensitive temperature intervals. It led to increase of a volumetric part of primary austenite dendrite crystals, to decrease of eutectic transformation overcooling degree, to forming of graphite eutectics and enlargement of dispersity of pearlite component in iron. Consequently, lowering of widespread iron castings rejects takes place, among them chilling, with simultaneous improvement of metal mechanical properties. As a result, the primary and real structures were varied, what had a positive effect on mechanical properties of casting metal. It is shown that use of solidification rate adjustment led to essential increase of metal tensile strength for the experimental casting.

1. Zhukov A. A., Silman G. I., Levi L. I. et al. Directory on iron casting. Edited by Girshovich N. G. 3rd edition. Leningrad., Mashinostroenie. 1978. 758 p.
2. Leushin I. O., Korovin V. A. Relation between modification and graphitization processes in cast iron. Chernye metally. 2010. No. 7. pp. 30–32.
3. Stefan E., Riposan I., Chisamera M. Application of thermal analysis in solidification pattern control of La-inoculated grey cast irons. J. Therm. Anal. Calorim. 2019. Vol. 138. pp. 2491–2503.
4. Kolokoltsev V. M., Petrochenko E. V., Molochkova O. S. Effect of niobium addition on the structural-phase composition, mechanical and special properties of cast irons based on the Cr–Mn–Ni–Ti-system. Chernye metally. 2019. No. 2. pp. 18–24.
5. Girshovich N. G. Crystallization and iron properties in castings. M., Metallurgiya. 1979. 562 p.
6. Kolokoltsev V. M., Petrochenko E. V., Molochkova O. S. Influence of complex V, Cu, Ti and B alloying on structural and phase state, mechanical properties and wear resistance of white cast iron. CIS Iron and Steel Review. 2016. Vol. 11. pp. 23–29.
7. Bunin K. P., Taran Yu. N. Cast iron structure. M., Metallurgiya. 1972. 160 p.
8. Bogachev I. N., Dubinin N. P., Egorenkov I. P. et al. Directory of a caster. Iron casting. Edited by Rubtsov N. N. M., Mashgiz. 1961. 774 p.
9. Glicksman M. E. Principles of solidification, an introduction to modern casting and crystal growth concepts. 2010. New York, Springer Verlag.
10. Christian J. W. The theory of transformations in metals and alloys. Oxford, Elsevier Science Ltd. 2002. 1200 p.
11. Hong Nga P. T., Ngoc Thien T., Josepha Pritadewi P., Phuong V. N. Y. Research on Factors Influencing the Formation Graphite and Effect of Graphite on Mechanical Properties of Grey Cast Iron. International Conference on System Science and Engineering (ICSSE), Dong Hoi, Vietnam. 2019. pp. 619–629.
12. Mingguo X., Changan Z., Jianxin Z. Bidirectional impact of undercooling on eutectic structural formation of hypoeutectic grey iron and its physical connotation. Materials Research Innovations. 2015. Vol. 19. pp. S5157–S5162.
13. Górny M., Tyraa E. Effect of cooling rate on microstructure and mechanical properties of thin-walled ductile iron castings. J. Mater. Eng. Perform. 2013. Vol. 22 (1). pp. 300–305.
14. Ilyinskiy V. A., Gulevskiy V. A., Kostyleva L. V., Gabelchenko N. I., Pozharskiy A. V. RF Patent 2156673 RF, МPК 7 В 22 D 27/04. Volgograd State Technical University. 2000.
15. Kostyleva L. V., Ilyinskiy V. A., Gabelchenko N. I., Pozharskiy A. V., Gulevskiy V. A. Study of the cooling modes of iron castings. Liteinoe proizvodstvo. 1999. No. 2. pp. 9–11.
16. Gabelchenko N. I., Belov A. A. Meshcheryakova O. A. Production of High-Quality Castings from Gray Iron by Differentiated Cooling in Iron Mould. Materials Science Forum. 2019.
Vol. 973 : Proc. of IX Int. Sci. and Techn. Conf. on Engineering – Innovation Technol. in Eng.: From Design to Production of Competitive Products (Volgograd, Sept. 2017). Volgograd St. Techn. Univ. pp. 15–20.
17. Gabelchenko N. I., Khantimirova S. B., Shtepina E. V. Study of local intervals of steel and iron crystallization process via the method of differential thermal analysis. Izvestiya VolgGTU. Series “Problems of material science, welding and strength in machine-building”. 2016. No. 9 (188). pp. 113–116.
18. Kidalov N. A., Gabelchenko N. I., Belov A. A., Savchenko A. Selection of exothermic carbon-containing additives for regulating the cooling mode of iron castings. Chernye metally. 2020. No. 7. pp. 23–27.
19. Sofroni L., Riposan I., Brabie V., Chisamera M. Cast iron. Bucharest, Romania: Editura Didactica si Pedagogica Publisher [Romanian language]. 1985. p. 36–49.
20. Kovalenko V. S. Metallographic reaction agents. Directory. 3rd edition. M., Metallurgiya. 1981. 121 p.
21. GOST 3443-87. Iron castings with different graphite form. Methods of structure determination. Intr. 01.07.1988.