Effect of transformation texture on the impact toughness of hot-rolled Ti + Nb microalloyed steel

2017 ◽  
Vol 128 ◽  
pp. 86-97 ◽  
Author(s):  
K.N. Sasidhar ◽  
T. Dhande ◽  
N. Javed ◽  
A. Ghosh ◽  
M. Mukherjee ◽  
...  
Keyword(s):  
Impact Toughness ◽  
Microalloyed Steel ◽  
Transformation Texture ◽  
Nb Microalloyed Steel ◽  
Hot Rolled ◽  
The Impact

scholarly journals Effect of Ti(C, N) Particle on the Impact Toughness of B-Microalloyed Steel

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 868 ◽  
Author(s):  
Yu Huang ◽  
Guo-Guang Cheng ◽  
Shi-Jian Li ◽  
Wei-Xing Dai ◽  
You Xie
Keyword(s):  
Impact Toughness ◽  
Microalloyed Steel ◽  
Fracture Initiation ◽  
Sem Analysis ◽  
Number Density ◽  
Size Number ◽  
Microalloying Elements ◽  
The Impact ◽  
Ti Content ◽  
Scanning Electron

Simultaneously improving the toughness and strength of B-microalloyed steel by adding microalloying elements (Nb, V, Ti) has been an extensively usedmethod for researchers. However, coarse Ti(C, N) particle will precipitate during solidification with inappropriate Ti content addition, resulting in poor impact toughness. The effect of the size, number density, and location of Ti(C, N) particle on the impact toughness of B-microalloyed steel with various Ti/N ratios was investigated. Coarse Ti(C, N) particles were investigated to act as the cleavage fracture initiation sites, by using scanning electron microscopy (SEM) analysis. When more coarse Ti(C, N) inclusions were located in ferrite instead of pearlite, the impact toughness of steel with ferrite–pearlite microstructure was lower. Meanwhile, when the size or the number density of Ti(C, N) inclusions was larger, the impact toughness was adversely affected. Normalizing treatment helps to improve the impact property of B-microalloyed steel, owing to the location of Ti(C, N) particles being partly changed from ferrite to pearlite. The formation mechanism of coarse Ti(C, N) particles was calculated by the thermodynamic software Factsage 7.1 and Thermo-Calc. The Ti(C, N) particles formed during the solidification of molten steel, and the N-rich Ti(C, N) phase precipitated first and, then, followed by the C-rich Ti(C, N) phase. Decreasing the Ti and N content is an effective way to inhibit the formation of coarse Ti(C, N) inclusions.

Effect of Grain Size and Meso-Texture on the Impact Toughness of Ti-Microalloyed Steel

2011 ◽  
Vol 702-703 ◽  
pp. 766-769 ◽  
Author(s):  
A. Ray ◽  
Debalay Chakrabarti
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Impact Toughness ◽  
Microalloyed Steel ◽  
Charpy Impact ◽  
Impact Testing ◽  
Grain Sizes ◽  
Matrix Strength ◽  
Charpy Impact Testing ◽  
The Impact

Charpy impact testing (over the transition temperature rage) on different samples of a Ti-microalloyed steel, having the same average-TiN particle size but different average-ferrite grain sizes, showed that in spite of the presence of large TiN cuboides, ferrite grain refinement can significantly improve the impact toughness, provided the meso-texture (i.e. the intensity of low-angle boundaries) and matrix strength can be restricted to low values.

Effect of Finishing Temperature on Mechanical Properties of a Nb-Microalloyed Steel Sheet

2010 ◽  
Vol 129-131 ◽  
pp. 1022-1028
Author(s):  
Daavood Mirahmadi Khaki ◽  
A. Akbarzadeh ◽  
Amir Abedi
Keyword(s):  
Mechanical Properties ◽  
Microalloyed Steel ◽  
Total Elongation ◽  
Controlled Rolling ◽  
Recrystallization Temperature ◽  
Effective Parameters ◽  
Steel Sheets ◽  
Intercritical Range ◽  
Nb Microalloyed Steel ◽  
Hot Rolled

Thermo mechanical processing and controlled rolling of microalloyed steel sheets are affected by several factors. In this investigation, finishing temperature of rolling which is considered as the most effective parameters on the final mechanical properties of hot rolled products has been studied. For this purpose, three different finishing temperatures of 950, 900 and 850 °C below the non-recrystallization temperature and one temperature of 800 °C in the intercritical range were chosen. It is observed that decreasing the finishing temperature causes increase of strength and decrease of total elongation. This is accompanied by more grain refinement of microstructure and the morphology was changed from polygonal ferrite to acicular one. Findings of this research provide suitable connection among finishing temperature, microstructural features, and mechanical properties of hot rolled Nb-microalloyed steel sheets.

scholarly journals On the Determining Role of Texture in Causing Delamination During Impact Fracture of Ti and Nb-Ti Microalloyed Steel

2019 ◽  
Author(s):  
Mingyu Sun ◽  
Xuemin Wang ◽  
R.D.K. Misra
Keyword(s):  
Impact Toughness ◽  
Fracture Surface ◽  
Impact Energy ◽  
Cleavage Fracture ◽  
Microalloyed Steel ◽  
Microalloyed Steels ◽  
Brittle Transition ◽  
High Toughness ◽  
The Impact

700 MPa grade Ti and Nb-Ti microalloyed steels produced by thermo-mechanical control rolled processes (TMCP) were studied to elucidate texture that contributes to delamination and consequent impact toughness. The microstructure of Ti and Nb-Ti steels consisted of ferrite and bainite. Compared with Ti steel, Nb-Ti steel was characterized by a microstructure with finer ferrite and more bainite. The results from tensile and impact tests indicated that there is insignificant change in tensile properties, but toughness was greater in Nb-Ti steel compared with Ti steel. More severe delamination in Nb-Ti steel is attributed to stronger α-fiber (RD ||<110>) texture than Ti steel, especially {100}<110>, {113}<110> and {112}<110> texture. Typical cleavage river patterns were not observed on delaminated fracture surface, instead the cleavage fracture surface indicated some dimples. Interestingly, the impact energy of samples with delamination was greater than samples without delamination in the ductile–brittle transition region. The study suggests that delamination in the ductile–brittle transition zone may also be representative of high toughness.

scholarly journals The influence of the oxygen equivalent in a gas-mixture on the structure and toughness of microalloyed steel weldments

2006 ◽  
Vol 71 (3) ◽  
pp. 313-321 ◽  
Author(s):  
Radica Prokic-Cvetkovic ◽  
Andjelka Milosavljevic ◽  
Aleksandar Sedmak ◽  
Olivera Popovic
Keyword(s):  
Impact Toughness ◽  
Crack Propagation ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Microalloyed Steel ◽  
Gas Mixtures ◽  
Gas Mixture ◽  
Weld Metals ◽  
Maximum Crack ◽  
The Impact

Testing were carried out on two steels. The first was microalloyed with Nb and second with Ti, Nb and V. The impact toughness of weld metals of these steels was evaluated using an instrumented Charpy pendulum. Five different gas mixtures (Ar, CO2, O2) were used to determine the optimal gas shielded metal arc process for both steels. The oxygen equivalent was used as a representative parameter of a mixture to follow, in particularly, its effect on the microstructure, toughness and crack propagation energy of the weld metal. For these investigated steels, the optimum gas mixture was established (5%CO2, 0.91%O2, balance Ar), which provided the maximum crack propagation energy, due to the microstructure which consisted dominantly of acicular ferrite.

Microstructure–Property Relationship in 22mm Thick X80 Coil Skelp

2010 ◽  
Author(s):  
M. Liebeherr ◽  
N. Bernier ◽  
D. Le`bre ◽  
N. Ilic´ ◽  
D. Quidort
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Electron Backscatter Diffraction ◽  
Bainitic Ferrite ◽  
Hot Strip Mill ◽  
Low Carbon ◽  
Welded Pipe ◽  
Hot Rolled ◽  
Backscatter Diffraction ◽  
The Impact

The progress in the development of heavy gauge X80 linepipe steel on coil at ArcelorMittal was recently rewarded with a 6000 ton commercial order for the production of 21.6mm wall thickness spiral welded pipe. The further product development is concentrating on the improvement of the impact toughness at low temperatures. Research is currently focussing on the relationship between the mechanical properties and the microstructure of the steels. In the present study, two industrially hot rolled X80 steels with thickness 21.6mm were investigated. The steels had the same chemical composition but were processed with different parameter sets in the hot strip mill. The two resulting low-carbon bainitic microstructures were composed predominantly of quasi-polygonal ferrite and globular bainitic ferrite / bainitic ferrite, respectively. Emphasis of the microstructure and property characterisation was laid on through-thickness gradients of grain size, hardness, texture, impact toughness and tensile properties. Accordingly, the materials were characterised at different positions in the thickness. Grain size and texture were determined by means of Electron Backscatter Diffraction (EBSD). Sub-size Charpy as well as sub-thickness tensile test specimens were taken at different positions in the cross section. The results show that the link between microstructure and properties is not at all obvious. The influence of mean grain size, grain size distribution and texture is discussed in detail.

Effect of Trace Boron on Low Temperature Impact Toughness of Hot-Rolled Nb-Added HSLA H-Beams

2012 ◽  
Vol 174-177 ◽  
pp. 1030-1033 ◽  
Author(s):  
Guo Tao Cui ◽  
Zuo Cheng Wang ◽  
Tao Sun ◽  
Wei Min Guo ◽  
Jun Qing Gao
Keyword(s):  
Impact Toughness ◽  
Impact Energy ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Total Oxygen ◽  
Transmission Electron ◽  
Temperature Impact ◽  
Low Temperature Impact Toughness ◽  
Hot Rolled ◽  
The Impact

In this research, trace boron (4ppm, 8ppm, 11ppm) was added into the Nb-added HSLA H-beams. The impact toughness of H-beams with/without boron was examined by Charpy impact test (V-notch). The morphologies of the microstructure and the fracture surfaces of the impact specimens were observed by metalloscope, stereomicroscope and electron probe. The experimental results prove that the absorbed impact energy at -40°C for the 4ppm, 8ppm, 11ppm boron-added steels respectively reaches up to 80J, 126J, 85J from 15J and H-beams with boron have a lower FATT than that without boron. It is also found that the total oxygen content affects the absorbed impact energy to a certain extent. It is discovered by transmission electron microscope (TEM) that boron mainly exists in solid solution state, except that a little amount of Fe23(C, B)6is formed at the grain boundaries, and the distribution of Nb(C, N) is also influenced by boron addition.

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