scholarly journals Effect of Thermomechanical Treatment on Acicular Ferrite Formation in Ti–Ca Deoxidized Low Carbon Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 296 ◽  
Author(s):  
Chao Wang ◽  
Xin Wang ◽  
Jian Kang ◽  
Guo Yuan ◽  
Guodong Wang
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Thermomechanical Treatment ◽  
Acicular Ferrite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Transformation Mechanism ◽  
Ferrite Formation

Transformation behaviors and mechanical properties under thermomechanical treatment conditions of Ti–Ca deoxidized low carbon steel were studied in comparison to Al–Ca treated steel. A thermomechanical simulation and a hot rolling experiment were carried out. Inclusions and microstructures were characterized, and the transformation mechanism was analyzed. The results indicated that typical inclusions in Ti–Ca deoxidized steel were TiOx-MnS-Al2O3-CaO, TiOx-MnO-Al2O3-CaO, and TiOx-MnS, which were effective for acicular ferrite (AF) nucleation. Acicular ferrite formation temperature decreased with an increase in cooling rate. A fine AF dominant microstructure was formed under a high driving force for the transformation from austenite to ferrite at lower temperatures. A high deformation of 43–65% discouraged the formation of acicular ferrite because of the increase in austenite grain boundaries serving as nucleation sites. The fraction of high-angled grain boundaries that acted as obstacles to cleavage cracks was the highest in the sample cooled at 5 °C/s because of full AF structure formation. The hardness increased significantly as the cooling rate increased from 2 to 15 °C/s, whereas it decreased under the condition of deformation because of the formation of (quasi-)polygonal ferrite. By applying accelerated water cooling, the mechanical properties, particularly impact toughness, were significantly improved as a result of fine AF microstructure formation.

Crystallographic analysis for acicular ferrite formation in low carbon steel weld metals

2014 ◽  
Vol 29 (4) ◽  
pp. 254-261 ◽  
Author(s):  
Atsushi Takada ◽  
Yu-Ichi Komizo ◽  
Hidenori Terasaki ◽  
Tomoyuki Yokota ◽  
Kenji Oi ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Acicular Ferrite ◽  
Low Carbon Steel ◽  
Crystallographic Analysis ◽  
Steel Weld ◽  
Low Carbon ◽  
Ferrite Formation ◽  
Weld Metals

Influence of Copper on Redistribution Behaviour of Boron in Titanium Stabilized and Low Carbon Steel as Observed by Neutron Induced Alpha Autoradiography

2013 ◽  
Vol 794 ◽  
pp. 502-506 ◽  
Author(s):  
Bharat B. Shriwastwa ◽  
Arun Kumar
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Grain Boundaries ◽  
Creep Strength ◽  
Nuclear Reactor ◽  
Low Carbon Steel ◽  
Carbon Steels ◽  
Low Carbon ◽  
Carbon Corrosion ◽  
Void Swelling

Boron content and its distribution play a significant role in modifying the metallurgical and mechanical properties of many steels and alloy at lower level of concentration. Precipitation of boron at the grain boundaries, have shown to improve the creep strength in titanium stabilized steel, high temperature ductility in low carbon corrosion resistant steel and the hardenability in low carbon steel in general. Titanium-stabilized steel (DIN 1.4970), was developed as a possible material for fast breeder sodium-cooled nuclear reactor core components for its superior creep strength, high micro-structural stability and elevated void swelling resistance. It is well known that, helium produced during neutron irradiation through the 10B(n,α)Li7 reaction, affects the mechanical properties and the amount of void swelling in nuclear reactor materials. Two nos. of Ti-stabilized steel samples with 40ppm boron and 2ppm boron (DIN 1.4970 & DIN1.4970LB steel) were analyzed for boron re-distribution behavior during different thermo-mechanical treatment using a technique known as Neutron Induced Alpha Autoradiography (NIAA). This technique is a well known technique, and widely used for revealing the spatial distribution of boron in the materials with a resolution approaching to ppm level. This technique has also been used to detect the influence of copper addition on boron distribution pattern in steel specimen. Mapping of boron autoradiography of Low carbon steels containing 20ppm of boron with and without copper was able to demonstrate this behavior. Boron track mapping of Low carbon steel without copper, in solution annealing treatment, show the uniform distribution of boron throughout the matrix, whereas when the similar steel with 1.48% copper was mapped, it shows the precipitation of boron at the grain boundaries.

scholarly journals Crystallographic Analysis for Acicular Ferrite Formation in Low Carbon Steel Weld Metals

2013 ◽  
Vol 31 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Atsushi TAKADA ◽  
Yu-ichi KOMIZO ◽  
Hidenori TERASAKI ◽  
Tomoyuki YOKOTA ◽  
Kenji OI ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Acicular Ferrite ◽  
Low Carbon Steel ◽  
Crystallographic Analysis ◽  
Steel Weld ◽  
Low Carbon ◽  
Ferrite Formation ◽  
Weld Metals

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.

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