Conclusions
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1.
The quality of the metal in axial trepans, which was sampled from two large forgings, is satisfactory along the entire length: no cracks, flakes, or other defects that disturb the metal's continuity are detected.
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2.
Nonmetallic inclusions are observed in the metal of the trepan: sulfides, oxides, and oxysulfides, arranged in the form of chains along the grain boundaries, and small lines in the direction of deformation; this exerts an unfavorable influence on the plastic and ductile properties of the forgings.
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3.
The presence of a dendritic and banded macrostructure suggests inadequacies in plastic-deformation technology.
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4.
The level of strength, plastic, and ductile characteristics of the metal after treatment in accordance with the new regime is lower, and the critical brittleness temperature higher by 30° C than after treatment in accordance with the regime previously adopted.
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5.
The new regime for the preliminary heat treatment of large forgings ensures decomposition of the austenite in accordance with a diffusion mechanism and the production of a grain corresponding to Nos. 5–7 in the central zones; this is positively manifested in the properties of the metal after final heat treatment.
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USSR Inventor's Certificate No. 1,272,713.
Additional information
Kramatorsk Plant „Energomashspetsstal'.” Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 47–51, June, 1990.
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Sheiko, V.S., Koval'chenko, A.V., Cherednichenko, T.G. et al. Investigation of the quality of metal in large forgings formed from steel 25Kh2NMFA in the annealed state. Met Sci Heat Treat 32, 453–458 (1990). https://doi.org/10.1007/BF01100168
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DOI: https://doi.org/10.1007/BF01100168