scholarly journals Accelerated Ferrite-to-Austenite Transformation During Intercritical Annealing of Medium-Manganese Steels Due to Cold-Rolling

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 926 ◽  
Author(s):  
Josh Mueller ◽  
David Matlock ◽  
John Speer ◽  
Emmanuel De Moor
Keyword(s):  
Phase Field ◽  
Volume Fraction ◽  
Intercritical Annealing ◽  
Cold Deformation ◽  
Low Carbon Steel ◽  
Austenite Formation ◽  
Low Carbon ◽  
Heating Rates ◽  
Nucleation Sites ◽  
Ultra Low Carbon Steel

Prior cold deformation is known to influence the ferrite-to-austenite (α → γ) transformation in medium-manganese (Mn) steels that occurs during intercritical annealing. In the present study, a 7Mn steel with ultra-low residual carbon content and varying amounts of prior cold deformation was intercritically annealed using various heating rates in a dilatometer. The study was conducted using an ultra-low carbon steel so that assessments of austenite formation during intercritical annealing would reflect the effects of cold deformation on the α → γ transformation and Mn partitioning and not effect cementite formation and dissolution or paraequilibrium partitioning induced austenite growth from carbon. Increasing prior cold deformation was found to decrease the Ac1 temperature, increase austenite volume fraction during intercritical annealing, and increase the amount of austenite nucleation sites. Phase field simulations were also conducted in an attempt to simulate the apparent accelerated α → γ transformation with increasing prior cold deformation. Mechanisms for accelerated α → γ transformation explored with phase field simulations included an increase in the amount of austenite nucleation sites and an increased Mn diffusivity in ferrite. Simulations with different amounts of austenite nucleation sites and Mn diffusivity in ferrite predicted significant changes in the austenite volume fraction during intercritical annealing.

Effect of Intercritical Annealing Temperature and Holding Time on Microstructure and Mechanical Properties of Dual Phase Low Carbon Steel

2014 ◽  
Vol 493 ◽  
pp. 721-726 ◽  
Author(s):  
Alfirano ◽  
Wibawa Samdan ◽  
Hidayat Maulud
Keyword(s):  
Carbon Steel ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Intercritical Annealing ◽  
Low Carbon Steel ◽  
Growth Rate Constant ◽  
Dual Phase ◽  
Initial Condition ◽  
Low Carbon ◽  
Intercritical Annealing Temperature

Dual phase steels are an important advanced high strength steel, which have been widely used in the automotive industry for vehicle components requiring light weight and safety. In this study, the formation of dual phase structure with various volume fraction of martensite in a low carbon steel SS400 during intercritical annealing were investigated. It was found that intercritical annealing temperature and holding time affected the microstructure and mechanical properties of dual phase low carbon steel. The specimens were heated at intercritical annealing temperature of 750°C, 775°C, 800°C and 825°C, for holding periods of 6-18 minutes, followed by water quenching in order to get a dual phase ferrite and martensite. After quenching, it was obtained the optimal annealing conditions at 800°C with a holding periods of 10 minutes. In this condition, the tensile strength was increased up to 621 N/mm2or 39.24% higher than the initial condition, while the elongation decreased up to 13.8%. The hardness of specimens increased from 127.7 to 235.83 HVN or up to 84.67% higher than the initial condition. Meanwhile the volume fraction of martensite was 24.08%. The higher the temperature of the heating value of grain growth rate constant (K) increases. In addition, at the optimal poin, the value ofK(grain growth rate constant) andn(Avramis exponent) were 0.263 and 0.318, respectively, with activation energy (Q) of 3.98 J/mol.

scholarly journals A study of isochronal austenitization kinetics in a low carbon steel

2014 ◽  
Vol 67 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Maximiano Maicon Batista Lopes ◽  
André Barros Cota
Keyword(s):  
Carbon Steel ◽  
Heating Rate ◽  
Low Carbon Steel ◽  
Carbon Diffusion ◽  
Austenite Formation ◽  
Low Carbon ◽  
Heating Rates ◽  
Initial Microstructure ◽  
Ferrite Structure ◽  
Kinetics Of

The austenite formation under isochronal conditions in Nb microalloyed low carbon steel was studied by means of dilatometric analysis and the data was adjusted to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation, for different heating rates and for three initial microstructures. It was shown that the kinetics of austenitization of a pearlite+ferrite structure is faster than that of martensite (tempered martensite) at a heating rate of 0.1ºC/s. For heating rates higher than 0.1ºC/s, the kinetics of austenitization of a martensite structure is faster than of pearlite+ferrite one. The K parameter of the JMAK equation increases with the heating rate for the three previous microstructures and it is greater for the initial microstructure composed of ferrite+pearlite. At lower heating rates, the formation of austenite in this steel is controlled by carbon diffusion, independently of the initial microstructure. At higher heating rates, the formation of austenite from an initial microstructure composed of pearlite and ferrite is controlled by interface-controlled transformation.

Phase Field Modelling of Austenite Formation in Low Carbon Steels

2011 ◽  
Vol 172-174 ◽  
pp. 1050-1059 ◽  
Author(s):  
Matthias Militzer ◽  
Hamid Azizi-Alizamini
Keyword(s):  
Phase Field ◽  
Intercritical Annealing ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Steels ◽  
Austenite Formation ◽  
Low Carbon ◽  
Advanced High Strength Steels ◽  
Robust Processing ◽  
Multi Phase

There is renewed interest in the investigation of austenite formation due to the development and increased use of advanced high strength steels for automotive applications. Intercritical annealing is an essential processing step for cold rolled and coated steel products with multi-phase microstructures. During intercritical annealing the initial ferrite-pearlite microstructure transforms partially to austenite. Models for the austenite formation are critical to predict the austenite fraction as a function of the thermal cycle thereby facilitating the design and control of robust processing paths. Modelling the austenite formation is challenging because of the morphological complexity of this transformation. Phase field models are a powerful tool to describe the evolution of microstructures with complex morphologies, e.g. formation of finger-type features during austenite formation. The present paper gives an overview of model approaches for the austenite formation. Phase field simulations are presented for two scenarios: (i) austenite formation from a fully pearlitic structure with a lamellar arrangement of carbide aggregates and (ii) austenite formation from ferrite-pearlite microstructures. Simulation results are compared with experimental observations for pearlitic steels. The challenges are delineated for the development of austenite formation models with predictive capabilities.

Development of trimming technology for hot rolled ultra-low carbon steel

1993 ◽  
Vol 90 (7-8) ◽  
pp. 917-922
Author(s):  
Y. Matsuda ◽  
M. Nishino ◽  
J. Ikeda
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Ultra Low Carbon Steel ◽  
Hot Rolled

Effect of trace Si on MgO·Al2O3 inclusion in ultra-low-carbon steel

2021 ◽  
Author(s):  
Lei Cao ◽  
De-li Shang ◽  
Xin-gang Ai ◽  
Peng-liang Jin ◽  
Yuan-you Xiao ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Ultra Low Carbon Steel

Precipitate/austenite equilibrium in a titanium-niobium ultra low carbon steel

Calphad ◽  
1986 ◽  
Vol 10 (2) ◽  
pp. 117-128 ◽  
Author(s):  
M. Grujicic ◽  
I. Wang ◽  
W.S. Owen
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Ultra Low Carbon Steel
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