Conclusions
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1.
With air hardening from 1080–1090°C thick 500-mm-blanks of type 40Kh4MVF steels possess through pearlitic hardenability.
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2.
After hardening the structure of the investigated steels consists of a mixture of lath and lamellar martensite and a small quantity of residual austenite. At a distance of 80–100 mm from the surface a bainitic constituent is observed.
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3.
The change in phase and structural compositions of type 40Kh4MVF steels across the cross section of large parts is complex. With distance from the surface the quantity of residual austenite first decreases, then, with the formation of bainite, increases somewhat, reaches a maximum, and drops. At the same time the quantity of the bainitic constituent increases as the result of the decrease in the quantity of martensite.
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4.
With a decrease in bainite content in the structure the temper resistance of the steel increases and with an increase in the quantity of residual austenite it decreases.
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5.
The optimum combination of mechanical properties and temper resistance is obtained in type 40Kh4MVF steels with a martensitic structure and a content in it of M6C and MC carbides in a ratio of about 10∶2.
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Additional information
Izhorsk Plant Production Union. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 56–59, June, 1987.
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Sandomirskii, M.M. The properties of large-production blanks of type 40Kh4MVF die steels. Met Sci Heat Treat 29, 468–472 (1987). https://doi.org/10.1007/BF00715886
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DOI: https://doi.org/10.1007/BF00715886