The Nanohardness of Acicular Ferrite and Bainitic Ferrite in Low Carbon Microalloying Steel

2007 ◽  
pp. 65-68
Author(s):  
Cheng Jia Shang ◽  
X. Liang ◽  
Xue Min Wang ◽  
Xin Lai He ◽  
H. Liu
Keyword(s):  
Acicular Ferrite ◽  
Bainitic Ferrite ◽  
Low Carbon

FIB and TEM Studies on the Bainitic Microstructure in Low Carbon HSLA Steels

2007 ◽  
Vol 26-28 ◽  
pp. 73-76 ◽  
Author(s):  
J.S. Kang ◽  
S.S. Ahn ◽  
C.Y. Yoo ◽  
Chan Gyung Park
Keyword(s):  
Acicular Ferrite ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Bainitic Ferrite ◽  
Granular Bainite ◽  
Low Carbon ◽  
3 Dimensional ◽  
Hsla Steels ◽  
Bainitic Microstructure ◽  
Lath Structure

In the present study, focused ion beam (FIB) technique was applied to make site-specific TEM specimens and to identify the 3-dimensional grain morphologies of bainitic microstructure in low carbon HSLA steels such as granular bainite, acicular ferrite and bainitic ferrite. Granular bainite consisted of fine subgrains and 2nd phase constituents like M/A or pearlite located at grain and subgrain boundaries. Acicular ferrite was characterized by an aggregate of ramdomly orientated and irregular shaped grains. The high angle boundaries between adjacent acicular ferrite grains caused by intragranular nucleation during continuous cooling process. Bainitic ferrite revealed uniform and parallel lath structure within the prior austenite grain boundaries and its’ packet size could effectively decreased by the formation of intragranular acicular ferrite.

Weldability of a Low Carbon High Strength Ti-Containing Bainitic Steel Produced by CSP

2010 ◽  
Vol 652 ◽  
pp. 275-278
Author(s):  
Ran Wei ◽  
Lin Cheng ◽  
Kai Ming Wu
Keyword(s):  
Heat Affected Zone ◽  
Acicular Ferrite ◽  
Gas Metal Arc Welding ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Bainitic Steel ◽  
Low Carbon ◽  
Fine Grained ◽  
Metal Arc Welding ◽  
Strip Production

The weldability of a 700 MPa grade low carbon Ti-containing microalloyed bainitic steel produced by compact strip production (CSP) has been investigated by gas metal arc welding. Microstructural features of the welded joint of the investigated steel have been investigated utilizing optical and scanning electron microscopy (SEM). The microstructures in the heat affected zone (HAZ) consist of a predominantly bainitic ferrite and a proportion of acicular ferrite which formed on Ti-oxide and/or nitride particles. The acicular ferrite formed earlier effectively partitions prior austenite grains into smaller separate regions. The bainite transformed at lower temperatures is thus restricted in the smaller regions so that fine-grained mixed microstructures are obtained. The superior toughness of the weld joint of the investigated steel is attributed to the prior formation of acicular ferrite in the heat-affected zone.

CHARACTERIZATION OF BAINITIC MICROSTRUCUTRES IN LOW CARBON HSLA STEELS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5965-5970 ◽  
Author(s):  
JU SEOK KANG ◽  
CHAN GYUNG PARK
Keyword(s):  
Acicular Ferrite ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Bainitic Ferrite ◽  
Carbon Steels ◽  
Granular Bainite ◽  
Low Carbon ◽  
High Angle ◽  
Rate Condition ◽  
Hsla Steels

The austenite phase of low carbon steels can be transformed to various bainitic microstructures such as granular bainite, acicular ferrite and bainitic ferrite during continuous cooling process. In the present study site-specific transmission electron microscope (TEM) specimens were prepared by using focused ion beam (FIB) to identify the bainitic microstructure in low carbon high strength low alloy (HSLA) steels clearly. Granular bainite was composed of fine subgrains and 2nd phase constituents like M/A or pearlite located at grain and/or subgrain boundaries. Acicular ferrite was identified as an aggregate of randomly orientated needle-shaped grains. The high angle relations among acicular ferrite grains were thought to be caused by intra-granular nucleation, which could be occur under the high cooling rate condition. Bainitic ferrite revealed uniform and parallel lath structure within the packet. In some case, however, the parallel lathes showed high angle relations due to packet overlapping during grow of bainitic ferrite, resulting in high toughness properties in bainitic ferrite based steels.

The Nanohardness of Acicular Ferrite and Bainitic Ferrite in Low Carbon Microalloying Steel

2007 ◽  
Vol 561-565 ◽  
pp. 65-68
Author(s):  
Cheng Jia Shang ◽  
X. Liang ◽  
Xue Min Wang ◽  
Xin Lai He ◽  
H. Liu
Keyword(s):  
Acicular Ferrite ◽  
Bainitic Ferrite ◽  
Low Carbon ◽  
Stiffness Measurement ◽  
The Matrix ◽  
Continuous Stiffness Measurement ◽  
Matrix Hardness

Dynamic continuous stiffness measurement (CSM) nanoindentation method was applied to measure nanohardness in low carbon microalloying steel. The matrix hardness for quenched phase and acicular ferrite calculated through analysis of curves is less fluctuated than the raw results, which shows that the analysis of the curves is helpful for determining matrix hardness.

Formation and Control of the Acicular Ferrite in Low Carbon Microalloying Steel

2005 ◽  
Vol 475-479 ◽  
pp. 85-88 ◽  
Author(s):  
Cheng Jia Shang ◽  
Y.T. Zhao ◽  
Xue Min Wang ◽  
L.J. Hu ◽  
Shan Wu Yang ◽  
...  
Keyword(s):  
Acicular Ferrite ◽  
Phase Structure ◽  
Bainitic Ferrite ◽  
Processing Parameters ◽  
Dual Phase ◽  
Low Carbon ◽  
Cooling Process ◽  
Ferrite Fraction ◽  
Multi Phase ◽  
And Control

The influence of processing parameters on the acicular ferrite formation for the low carbon microalloying steel was studied. The results showed that the fraction of acicular ferrite could be controlled by the cooling process. The acicular ferrite/ bainitic ferrite dual phase structure can be formed. The multi-phase microstructure is ultra fine. The hardness is sensitively affected by the acicular ferrite fraction.

scholarly journals A Comparative Study of Acicular Ferrite Transformation Behavior between Surface and Interior in a Low C–Mn Steel by HT-LSCM

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 699
Author(s):  
Xiaojin Liu ◽  
Guo Yuan ◽  
Raja. Devesh Kumar Misra ◽  
Guodong Wang
Keyword(s):  
Grain Boundaries ◽  
Cooling Rate ◽  
Acicular Ferrite ◽  
Laser Scanning ◽  
Sample Surface ◽  
Surface Microstructure ◽  
In Situ Observation ◽  
Low Carbon ◽  
Transformation Behavior ◽  
Ferrite Transformation

In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved by HT-LSCM. The microstructure between the surface and interior of the HT-LSCM sample was compared. The results showed that Ti–Ca oxide particles were effective sites for acicular ferrite (AF) nucleation. The start transformation temperature at grain boundaries and intragranular particles decreased with an increase in cooling rate, but the AF nucleation rate increased and the surface microstructure was more interlocked. The sample surface microstructure obtained at 3 °C/s was dominated by ferrite side plates, while the ferrite nucleating sites transferred from grain boundaries to intragranular particles when the cooling rate was 15 °C/s. Moreover, it was interesting that the microstructure and microhardness of the sample surface and interior were different. The AF dominating microstructure, obtained in the sample interior, was much finer than the sample surface, and the microhardness of the sample surface was much lower than the sample interior. The combined factors led to a coarse size of AF on the sample surface. AF formed at a higher temperature resulted in the coarse size. The available particles for AF nucleation on the sample surface were quite limited, such that hard impingement between AF plates was much weaker than that in the sample interior. In addition, the transformation stress in austenite on the sample surface could be largely released, which contributed to a coarser AF plate size. The coarse grain size, low dislocation concentration and low carbon content led to lower hardness on the sample surface.

The Influence of Oxide Inclusion on the Refinement of Bainite and Toughness in HAZ for Low Carbon Steels

2013 ◽  
Vol 651 ◽  
pp. 163-167
Author(s):  
Shu Rui Li ◽  
Xue Min Wang ◽  
Xin Lai He
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Oxide Inclusion ◽  
Optical Microscope ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
The Core ◽  
Ti Oxides ◽  
Bainitic Steels

The influence of Ti oxide on the toughness of heat affected zone for low carbon bainitic steels has been investigated. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the microstructure and mechanical properties after welding thermal simulation were also investigated. The effect of Ti oxide inclusion on the transformation of acicular ferrite has also been studied. The results show that after the melting with Ti dioxide technique the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. It has been found the acicular ferrite can nucleate at the inclusions and the Ti oxide inclusion will promote the nucleation of acicular ferrite, and the acicular ferrite will block the growth of bainite. Therefore by introducing the Ti oxide in the steels the microstructure of HAZ could be refined markedly therefore the toughness of HAZ can be improved evidently.

In situ observation of growth behaviour of acicular ferrite in low-carbon steel containing 13 ppm magnesium

2017 ◽  
Vol 46 (2) ◽  
pp. 176-183 ◽  
Author(s):  
Chi-Kang Lin ◽  
Yan-Chi Pan ◽  
Weng-Sing Hwang ◽  
Ying-Chien Fang ◽  
Yen-Hao Su ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Acicular Ferrite ◽  
Low Carbon Steel ◽  
In Situ Observation ◽  
Low Carbon ◽  
Growth Behaviour

Isothermal Transformation, Microstructure and Mechanical Properties of Ausformed Low-Carbon Carbide-Free Bainitic Steel

2018 ◽  
Vol 941 ◽  
pp. 329-333 ◽  
Author(s):  
Jiang Ying Meng ◽  
Lei Jie Zhao ◽  
Fan Huang ◽  
Fu Cheng Zhang ◽  
Li He Qian
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Isothermal Transformation ◽  
Bainitic Transformation ◽  
Isothermal Treatment ◽  
Bainitic Steel ◽  
Low Carbon ◽  
Microstructure And Mechanical Properties

In the present study, the effects of ausforming on the bainitic transformation, microstructure and mechanical properties of a low-carbon rich-silicon carbide-free bainitic steel have been investigated. Results show that prior ausforming shortens both the incubation period and finishing time of bainitic transformation during isothermal treatment at a temperature slightly above the Mspoint. The thicknesses of bainitic ferrite laths are reduced appreciably by ausforming; however, ausforming increases the amount of large blocks of retained austenite/martenisite and decreases the volume fraction of retained austenite. And accordingly, ausforming gives rise to significant increases in both yield and tensile strengths, but causes noticeable decreases in ductility and impact toughness.

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