St. Petersburg State Mining University (St. Petersburg, Russia):

K. Yu. Shakhnazarov, Cand. Eng., Associate Prof., the Chair of Material Science and Technology of Art Objects, e-mail: karen812@yandex.ru
E. I. Pryakhin, Dr. Eng., Prof., the Chair of Material Science and Technology of Art Objects

According to the researches by G. Tamman, E. Gudremon, A. A. Bochvar, A. M. Samarin and B. G. Livshits, any property is suitable for detecting of transformation: bending or extremal value on a curve. Transformations in ferrum at the temperature below 700 °С have been discussed many times. V. S. Meskin denies transformation at the temperature below 700 °С without any references, but at the same time he refers to the data by G. N. Mekhed and A. Sover that testify about the contrary conclusions (minimal values of  and number of torsion twistings at 600 °С). The paper presents analysis of extremal values on the curves (strength of upsetting resistance, parameters of fine structure and metallographic structure) in dependence on temperature, as well as multiple literature data on anomalies of physical and mechanical properties if ferrum and steels. Based on the above-mentioned, transformation at ~650 °C is declared. Recognition of transformation at the preset temperature is one of the ways allowing to formulate the version of the nature of embrittlement of forged (P. Oberhoffer) or quenched (E. Gudremon) or cold-worked (E. Gudremon, G. A. Kashchenko) steel after tempering (annealing) at the temperature above ∼ 650 °C. Other variants of considered metal post-treatment are presented by isothermal austenite transformation (M. Gensammer) and gigantic diffusion (Yu. I. Ustanovshchikov) at the same temperature as well as a “wonderful fact” of transformation in pearlite during seconds at the temperature 670 – 630 °C (V. M. Schastlivtsev).

1. Tyrkel E. History of development of the diagram “ferrum — carbon”. Moscow : Mashinostroenie, 1968. 280 p.
2. Livshitz B. G. Physical properties of alloys. Moscow : Metallurgizdat, 1946. 320 p.
3. Savitskiy E. M. Influence of temperature on mechanical properties of metals and alloys. Moscow : Izdatelstvo AN SSSR, 1957. 294 p.
4. Malyshev K. A., Sagaradze V. V., Sorokin I. P., Zemtsova N. D., Teplov V. A., Uvarov A. I. Phase cold working of austenite alloys on Fe-Ni base. Moscow : Nauka, 1982. 260 p.
5. Vasilyeva A. G., Pogodin-Alekseev G. I. Anomaly of strength and ductility in intercritical interval. Metallovedenie i termicheskaya obrabotka metallov. 1957. No. 1. pp. 23–29.
6. Gudremon E. Special steels in 3 volumes. Vol. 1. Moscow : Metallurgizdat, 1959. 952 p.
7. Grigorovich V. K. Electronic building and thermodynamics of ferrum alloys. Moscow : Nauka, 1970. 292 p.
8. Powell R.W. Further measurements of the thermal and electrical conductivity of iron at high temperatures. The proceedings of the physical society. 1939. Vol. 51. Part 3. No. 285. pp. 407–418.
9. Mogutnov B. M., Tomilin I. A., Shvartsman L. A. Thermodynamics of ferrum-carbon alloys. Moscow : Metallurgiya, 1972. 328 p.
10. Taluts S. G., Smirnov A. L., Glagoleva Yu. V., Korshunov I. G., Gorbatov V. I., Polev V. F., Ivliev A. D. Thermal-physical properties of the alloys based on the metals of Fe subgroup at high temperatures. Ekaterinburg : Ural State Mining University, 2013. 108 p.
11. Bozort R. Ferromagnetism. Moscow : Izdatelstvo inostrannoy literatury, 1956. 784 p.
12. Oberhoffer P. Technical ferrum. Moscow, Leningrad : Metallurgizdat, 1940. 535 p.
13. Shakhnazarov K. Yu., Pryakhin E. I. Anomalies in the structure and properties near three vertical lines on the “iron-carbon” diagram by D. K. Chernov. Chernye metally. 2016. No. 10. pp. 29–32.
14. Schastlivtsev V. M., Mirzaev D. A., Yakovleva I. L., Okishev K. Yu., Tabatchikova T. I., Khlebnikova Yu. V. Pearlite in carbon steels. Ekaterinburg : UrO RAN, 2006. 311 p.
15. Shakhnazarov K. Yu. Anomalies of ferrum ductility as a sequence of transformation at ~650 °С. Zapiski Gornogo instituta. 2016. Vol. 217. pp. 150–155.
16. Schastlivtsev V. M., Tabatchikova T. I., Yakovleva I. L., Klyueva S. Yu. Influence of structure and non-metallic inclusions on intercrystallite brittleness of cast steel. Phizika metallov i metallovedenie. 2013. Vol. 114. No. 2. pp. 199–208.
17. Makarov A. V., Schastlivtsev V. M., Tabatchikova T. I., Yakovleva I. L., Khlebnikova Yu. V., Egorova L. Yu. Wear resistance of hypereutectoid carbon steels with the structure of isothermal austenite decomposition. Phizika metallov i metallovedenie. 2004. Vol. 97. No. 5. pp. 94–105.
18. Ustinovshchikov Yu. I., Bannykh O. A. Nature of tempering brittleness of steels. Moscow : Nauka, 1984. 240 p.
19. Izotov V. I. Extraction of dispersed vanadium carbides on interphase boundary during pearlite transformation of steel. Phizika metallov i metallovedenie. 2011. Vol. 111 No. 6. pp. 619–625.
20. Lozinskiy M. G. High-temperature metallography. Moscow : Mashgiz, 1956. 312 p.
21. Gaev I. S., Sheyanova E. V. Polymorphism and its influence on ferrum properties. Symposium on metallurgy and material science devoted to the 100^th anniversary of opening of ferrum polymorphism by D. K. Chernov. Moscow : Nauka, 1971. p. 26–35.
22. Dhakhnazarov K. Yu., Shalhnazarov A. Yu. 430 ± 30 °С as the noddle (critical) temperature of ferrum and carbon steel. Metallovedenie i termicheskaya obrabotka metallov. 2001. No. 11. pp. 24–25.
23. Takeuchi T. Work-hardening of iron single crystals between 25–900 °C. Japanese journal of applied physics. 1970. Vol. 9. No. 4. pp. 391–400.
24. Rudnitskiy N. P. Static mechanical properties of steel AK29 in the temperature range 290 — 1500 K. Metally. 2003. No. 1. pp. 57–62.