The paper attempts to analyze distortions of cast iron and cast steel rings, after heat treatment cycles. The factors influencing distortion are: chemical composition of material, sample geometry, manufacturing process, hardenability, temperature and heat treatment method. Standard distortion tests are performed on C-ring samples. We selected a ring-model, which approximate the actual part, so that findings apply to gear rings. Because distortion depends on so many variables, this study followed strictly defined procedures. The research was started by specifying the appropriate geometry of the samples. Then, the heat treatment was conducted and samples were measured again. The obtained results allow to determine the value of the resulting distortion and their admissibility. The research will be used to evaluate the possibility of using the material to produce parts of equipment operated under extreme load conditions.
 Zoch, H.W. (2009). Distortion engineering: vision or ready to application? Material Science & Engineering Technology. 40(5/6), 342-348. DOI: 10.1002/mawe.200900457.
 Zoch, H.W. (2006). From Single Production Step to Entire Process Chain - the Global Approach of Distortion Engineering. Material Science & Engineering Technology. 37(1), 6-10. DOI: 10.1002/mawe.200500958.
 Clausen, B., Frerichs, F., Kohlhoff, T., Lubben, Th., Prinz, C., Rentsch, R., Solter, J., Surm, H., Stobener, D. & Klein, D. (2009). Identification of process parameters affecting distortion of disks for gear manufacture Part I: casting, forming and machining. Material Science & Engineering. 40(5-6), 354-360. DOI: 10.1002/mawe.200900459.
 Zwolak, J. & Witek, M. (2010). Selection criteria for the tooth material in the context of the applied finishing treatment of case hardened and quenched teeth. Tribologia. 234(6), 293-306. DOI: 10.1590/S1678-77572007000500012. (in Polish).
 Myszka, D. & Babul T. M. (2010). Austemperd ductile iron manufacturing in vacuum furnace with gas cooling. Archives of Mechanical Technology and Materials. 30(3), 35-42. (in Polish).
 Myszka, D. (2013). New Possibilities of Shaping the Surface Properties in Austempered Ductile Iron Castings. Archives of Foundry Engineering. 13(1), 103-106. DOI: 10.2478/afe- 2013-0020.
 Sosa, A.D., Echeverria, M.D., Moncada, O.J., Mingolo, N. & Sikora, J.A. (2009). Influence of nodule count on residual stresses and distortion in thin wall ductile iron plates of different matrices. Journal of Materials Processing Technology. 209(15-16), 5545-5551. DOI:10.1016/ j.jmatprotec.2009.05.010.
 Shin, M.W., Jang, G.H., Kim, J.K., Kim, H.Y. & Jang, H. (2013). The Effect of Residual Stress on the Distortion of Gray Iron Brake Disks. Journal of Materials Engineering and Performance. 22(4), 1129-1135. DOI: 10.1007/s11665- 012-0397-7.
 Atraszkiewicz, R., Januszewicz, B., Kaczmarek, Ł., Stachurski, W., Dybowski, K. & Rzepkowski, A. (2012). High pressure gas quenching: Distortion analysis in gears after heat treatment. Materials Science & Engineering A. 558, 550-557. DOI: 10.1016/j.msea.2012.08.047.