Ferrite-Bainite Dual Phase Structure and Mechanical Characterization of AISI 4340 Steel

B. M. Gurumurthy, Sathya Shankar Sharma, Achutha Kini

Research output: Contribution to journalConference article

2 Citations (Scopus)

Abstract

AISI 4340 steel is a medium hardness and moderate strength alloy, finds application in different heat treatment conditions. Commercially available AISI 4340 steel can be subjected to special heat treatment to obtain duplex structures (ferrite-martensite or ferrite-bainite) with different intercritical austenitisation temperatures for mechanical property enhancement and serves as a platform to discuss the property deviation. In the present work dual phase structure (ferrite-bainite) is odtained by partial austenitization of room temperature structure followed by isothermal quenching (austempering) in the lower bainite temperature range. Since it is medium carbon steel, the dual phase contains well dispersed bainite phase in the continuous ferrite matrix. Accordingly, specimen are heated to intercritical temperatures (750, 770, 790°C) for 2 hours, rapid quenching in the salt bath containing sodium nitrate and nitrite mixture maintained in the lower bainite temperature range (350°C) for two time durations 24 minutes (optimum) and 24 hours (prolonged holding) followed by air cooling. Dual phase obtained in optimum soaking duration shows moderate hardness, strength, ductility and toughness values whereas prolonged duration shows improved values of ductility and toughness if the austenitising temperature is selected suitably so that the data may be employed for machinability improvement.

Original languageEnglish
Pages (from-to)24907-24914
Number of pages8
JournalMaterials Today: Proceedings
Volume5
Issue number11
DOIs
Publication statusPublished - 01-01-2018
Event2017 International Conference on Advances in Materials and Manufacturing Applications, IConAMMA 2017 - Bengaluru, India
Duration: 17-08-201719-08-2017

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Bainite
Steel
Phase structure
Ferrite
Temperature
Toughness
Ductility
Hardness
Heat treatment
Sodium Nitrite
Rapid quenching
Machinability
Martensite
Carbon steel
Quenching
Nitrates
Salts
Sodium
Cooling
Mechanical properties

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Cite this

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title = "Ferrite-Bainite Dual Phase Structure and Mechanical Characterization of AISI 4340 Steel",
abstract = "AISI 4340 steel is a medium hardness and moderate strength alloy, finds application in different heat treatment conditions. Commercially available AISI 4340 steel can be subjected to special heat treatment to obtain duplex structures (ferrite-martensite or ferrite-bainite) with different intercritical austenitisation temperatures for mechanical property enhancement and serves as a platform to discuss the property deviation. In the present work dual phase structure (ferrite-bainite) is odtained by partial austenitization of room temperature structure followed by isothermal quenching (austempering) in the lower bainite temperature range. Since it is medium carbon steel, the dual phase contains well dispersed bainite phase in the continuous ferrite matrix. Accordingly, specimen are heated to intercritical temperatures (750, 770, 790°C) for 2 hours, rapid quenching in the salt bath containing sodium nitrate and nitrite mixture maintained in the lower bainite temperature range (350°C) for two time durations 24 minutes (optimum) and 24 hours (prolonged holding) followed by air cooling. Dual phase obtained in optimum soaking duration shows moderate hardness, strength, ductility and toughness values whereas prolonged duration shows improved values of ductility and toughness if the austenitising temperature is selected suitably so that the data may be employed for machinability improvement.",
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Ferrite-Bainite Dual Phase Structure and Mechanical Characterization of AISI 4340 Steel. / Gurumurthy, B. M.; Sharma, Sathya Shankar; Kini, Achutha.

In: Materials Today: Proceedings, Vol. 5, No. 11, 01.01.2018, p. 24907-24914.

Research output: Contribution to journalConference article

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N2 - AISI 4340 steel is a medium hardness and moderate strength alloy, finds application in different heat treatment conditions. Commercially available AISI 4340 steel can be subjected to special heat treatment to obtain duplex structures (ferrite-martensite or ferrite-bainite) with different intercritical austenitisation temperatures for mechanical property enhancement and serves as a platform to discuss the property deviation. In the present work dual phase structure (ferrite-bainite) is odtained by partial austenitization of room temperature structure followed by isothermal quenching (austempering) in the lower bainite temperature range. Since it is medium carbon steel, the dual phase contains well dispersed bainite phase in the continuous ferrite matrix. Accordingly, specimen are heated to intercritical temperatures (750, 770, 790°C) for 2 hours, rapid quenching in the salt bath containing sodium nitrate and nitrite mixture maintained in the lower bainite temperature range (350°C) for two time durations 24 minutes (optimum) and 24 hours (prolonged holding) followed by air cooling. Dual phase obtained in optimum soaking duration shows moderate hardness, strength, ductility and toughness values whereas prolonged duration shows improved values of ductility and toughness if the austenitising temperature is selected suitably so that the data may be employed for machinability improvement.

AB - AISI 4340 steel is a medium hardness and moderate strength alloy, finds application in different heat treatment conditions. Commercially available AISI 4340 steel can be subjected to special heat treatment to obtain duplex structures (ferrite-martensite or ferrite-bainite) with different intercritical austenitisation temperatures for mechanical property enhancement and serves as a platform to discuss the property deviation. In the present work dual phase structure (ferrite-bainite) is odtained by partial austenitization of room temperature structure followed by isothermal quenching (austempering) in the lower bainite temperature range. Since it is medium carbon steel, the dual phase contains well dispersed bainite phase in the continuous ferrite matrix. Accordingly, specimen are heated to intercritical temperatures (750, 770, 790°C) for 2 hours, rapid quenching in the salt bath containing sodium nitrate and nitrite mixture maintained in the lower bainite temperature range (350°C) for two time durations 24 minutes (optimum) and 24 hours (prolonged holding) followed by air cooling. Dual phase obtained in optimum soaking duration shows moderate hardness, strength, ductility and toughness values whereas prolonged duration shows improved values of ductility and toughness if the austenitising temperature is selected suitably so that the data may be employed for machinability improvement.

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