Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels
In the past decade, efforts have been focused on developing very fine, medium-carbon bainitic steels via the low-temperature (typically 300–400 °C) ausforming process, which not only enables shorter isothermal holding times for bainitic transformation at low temperatures, but also offers significant...
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MDPI AG
2021-01-01
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| Online Access: | https://www.mdpi.com/2075-4701/11/1/138 |
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| author | Pentti M. Kaikkonen Mahesh C. Somani Leo Pentti Karjalainen Jukka I. Kömi |
| author_facet | Pentti M. Kaikkonen Mahesh C. Somani Leo Pentti Karjalainen Jukka I. Kömi |
| author_sort | Pentti M. Kaikkonen |
| collection | DOAJ |
| description | In the past decade, efforts have been focused on developing very fine, medium-carbon bainitic steels via the low-temperature (typically 300–400 °C) ausforming process, which not only enables shorter isothermal holding times for bainitic transformation at low temperatures, but also offers significantly improved strength. This paper describes static recrystallization (SRX) characteristics of austenite in four medium-carbon 2%Mn-1.3%Si-0.7%Cr steels with and without microalloying intended for the development of these steels. The stress-relaxation method on a Gleeble simulator resulted in recrystallization times over a wide range of temperatures, strains and strain rates. Also, the occurrence of precipitation was revealed. Powers of strain (−1.7 to −2.7) and strain rate (−0.21 to −0.28) as well as the apparent activation energies (225–269 kJ/mol) were in the ranges reported in the literature for C-Mn and microalloyed steels with lower Mn and Si contents. The new regression equations established for estimating times for 50% SRX revealed the retardation effects of microalloying and Mo addition showing reasonable fits with the experimental data, whereas the previous model suggested for ordinary microalloyed steels tended to predict clearly shorter times on average than the experimental values for the present coarse-grained steels. The Boratto equation to estimate the non-recrystallization temperature was successfully modified to include the effect of Mo alloying and high silicon concentrations. |
| first_indexed | 2024-03-09T05:05:01Z |
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| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-09T05:05:01Z |
| publishDate | 2021-01-01 |
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| spelling | doaj.art-5a9ffe1b7b2840509041a833e5b284c42023-12-03T12:56:12ZengMDPI AGMetals2075-47012021-01-0111113810.3390/met11010138Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic SteelsPentti M. Kaikkonen0Mahesh C. Somani1Leo Pentti Karjalainen2Jukka I. Kömi3Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014 Oulun yliopisto, FinlandMaterials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014 Oulun yliopisto, FinlandMaterials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014 Oulun yliopisto, FinlandMaterials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014 Oulun yliopisto, FinlandIn the past decade, efforts have been focused on developing very fine, medium-carbon bainitic steels via the low-temperature (typically 300–400 °C) ausforming process, which not only enables shorter isothermal holding times for bainitic transformation at low temperatures, but also offers significantly improved strength. This paper describes static recrystallization (SRX) characteristics of austenite in four medium-carbon 2%Mn-1.3%Si-0.7%Cr steels with and without microalloying intended for the development of these steels. The stress-relaxation method on a Gleeble simulator resulted in recrystallization times over a wide range of temperatures, strains and strain rates. Also, the occurrence of precipitation was revealed. Powers of strain (−1.7 to −2.7) and strain rate (−0.21 to −0.28) as well as the apparent activation energies (225–269 kJ/mol) were in the ranges reported in the literature for C-Mn and microalloyed steels with lower Mn and Si contents. The new regression equations established for estimating times for 50% SRX revealed the retardation effects of microalloying and Mo addition showing reasonable fits with the experimental data, whereas the previous model suggested for ordinary microalloyed steels tended to predict clearly shorter times on average than the experimental values for the present coarse-grained steels. The Boratto equation to estimate the non-recrystallization temperature was successfully modified to include the effect of Mo alloying and high silicon concentrations.https://www.mdpi.com/2075-4701/11/1/138medium-carbon steelsausteniteflow stressstress relaxationrecrystallization kineticsprecipitation |
| spellingShingle | Pentti M. Kaikkonen Mahesh C. Somani Leo Pentti Karjalainen Jukka I. Kömi Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels Metals medium-carbon steels austenite flow stress stress relaxation recrystallization kinetics precipitation |
| title | Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels |
| title_full | Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels |
| title_fullStr | Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels |
| title_full_unstemmed | Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels |
| title_short | Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels |
| title_sort | flow stress behaviour and static recrystallization characteristics of hot deformed austenite in microalloyed medium carbon bainitic steels |
| topic | medium-carbon steels austenite flow stress stress relaxation recrystallization kinetics precipitation |
| url | https://www.mdpi.com/2075-4701/11/1/138 |
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