scholarly journals Determination of Non-Recrystallization Temperature for Niobium Microalloyed Steel

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2639
Author(s):  
Mohammad Nishat Akhtar ◽  
Muneer Khan ◽  
Sher Afghan Khan ◽  
Asif Afzal ◽  
Ram Subbiah ◽  
...  
Keyword(s):  
Microalloyed Steel ◽  
Casting Process ◽  
Rolling Process ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Nb Microalloyed Steel ◽  
Niobium Microalloyed Steel ◽  
Multiple Hit ◽  
Deformation Tests

In the present investigation, the non-recrystallization temperature (TNR) of niobium-microalloyed steel is determined to plan rolling schedules for obtaining the desired properties of steel. The value of TNR is based on both alloying elements and deformation parameters. In the literature, TNR equations have been developed and utilized. However, each equation has certain limitations which constrain its applicability. This study was completed using laboratory-grade low-carbon Nb-microalloyed steels designed to meet the API X-70 specification. Nb- microalloyed steel is processed by the melting and casting process, and the composition is found by optical emission spectroscopy (OES). Multiple-hit deformation tests were carried out on a Gleeble® 3500 system in the standard pocket-jaw configuration to determine TNR. Cuboidal specimens (10 (L) × 20 (W) × 20 (T) mm3) were taken for compression test (multiple-hit deformation tests) in gleeble. Microstructure evolutions were carried out by using OM (optical microscopy) and SEM (scanning electron microscopy). The value of TNR determined for 0.1 wt.% niobium bearing microalloyed steel is ~ 951 °C. Nb- microalloyed steel rolled at TNR produce partially recrystallized grain with ferrite nucleation. Hence, to verify the TNR value, a rolling process is applied with the finishing rolling temperature near TNR (~951 °C). The microstructure is also revealed in the pancake shape, which confirms TNR.

New Trends and Technologies in Thin-Slab Direct Rolling: Improved Microstructure & Mechanical Behavior

2012 ◽  
Vol 706-709 ◽  
pp. 2752-2757 ◽  
Author(s):  
Christian Klinkenberg ◽  
C. Bilgen ◽  
J.M. Rodriguez-Ibabe ◽  
Beatriz López ◽  
P. Uranga
Keyword(s):  
Rolling Process ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Thin Slab ◽  
Present Contribution ◽  
Thin Slab Casting ◽  
Finishing Mill ◽  
Direct Rolling ◽  
Cast Microstructure

The use of CSP®thin slab casting followed by direct thermomechanical rolling is well placed for the production of low-carbon Nb microalloyed steels. In this process thin slabs of between 48 and 90 mm thickness are cast and directly hot rolled to hot strip typically between 1 and 12 mm thick. To obtain optimum strength and toughness property combinations in a direct rolling process, hot rolling has to compact the dendritic as-cast microstructure and to achieve a fine-grained microstructure. This affords a two-stage rolling strategy with start rolling above the recrystallization stop temperature and finish rolling in the non-recrystallization temperature range. Temperature and deformation in the first stand should be as high as possible in order to delete the initial as-cast microstructure by complete recrystallization. Based on these considerations, SMS Siemag further developed the CSP®concept including features allowing isothermal rolling in the first stands of the finishing mill. The present contribution gives the results of a laboratory study of this innovative approach. The report concludes with resulting new plant configurations for improved high strength and API linepipe grade production.

Influence of Thermal History on the Hot Ductility of Ti-Nb Microalloyed Steels

2016 ◽  
Vol 879 ◽  
pp. 199-204 ◽  
Author(s):  
Coline Beal ◽  
Ozan Caliskanoglu ◽  
Christof Sommitsch ◽  
Sergiu Ilie ◽  
Jakob Six ◽  
...  
Keyword(s):  
Thermal Cycle ◽  
Crack Formation ◽  
Microalloyed Steel ◽  
Casting Process ◽  
Testing Temperature ◽  
Microalloyed Steels ◽  
Hot Ductility ◽  
Thermal Treatments ◽  
Continuous Casting Process ◽  
Nb Microalloyed Steel

The hot ductility of Ti-Nb microalloyed steel has been investigated to evaluate the sensitivity to surface crack formation during the continuous casting process. Tensile samples were subjected to different thermal treatments and were tested at deformation temperatures ranging from 650°C to 1000°C using a strain rate of 10-3s-1. It has been found, that the investigated steel evinced poor ductility over almost the whole testing temperature range characterized by marked grain boundary cracking, irrespective of which thermal cycle has been utilized or whether the samples have been melted or only reheated. Microstructural examinations and supplementary thermo-kinetic computer simulations revealed distinct Ti-Nb precipitation throughout the microstructure being responsible for the deteriorated materials hot ductility.

scholarly journals Application of Taguchi Method for Investigating the Mechanical Properties of a Microalloyed Steel

2014 ◽  
Vol 59 (3) ◽  
pp. 853-858 ◽  
Author(s):  
M. Ayaz ◽  
N. Banimostafa Arab ◽  
D. Mirahmadi Khaki
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Taguchi Method ◽  
Microalloyed Steel ◽  
Rolling Process ◽  
Processing Parameters ◽  
Microalloyed Steels ◽  
Strain Hardening Exponent ◽  
Coiling Temperature ◽  
Nb Microalloyed Steel

Abstract In the present investigation, the effects of processing parameters, such as roughing, finishing and coiling temperatures, on the strain hardening exponent and yield strength of a Nb-microalloyed steel has been studied by Taguchi method. In order to achieve maximum n-value and yield strength, tests were done in a laboratorial pilot considering a L16 orthogonal array of Taguchi method under following condition: roughing temperature of 1000, 1050, 1100, 1150 °C, finishing temperature of 800, 850, 900, 950 °C, coiling temperature of 550, 600, 650, 700 °C. Then, analysis of variance and signal to noise ratios are performed on the measured data. The results indicated that the finishing and coiling temperatures were the major factor affecting the mechanical properties. The confirmation tests at optimal conditions approve the effectiveness of this robust design methodology in investigating the hot rolling process of the microalloyed steels.

Precipitation Strengthening in a Low Carbon Nb-Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 481-488 ◽  
Author(s):  
D.Q. Bai ◽  
F. Hamad ◽  
J. Asante ◽  
S. Hansen
Keyword(s):  
Mechanical Properties ◽  
Microalloyed Steel ◽  
High Strength Steels ◽  
Aging Treatment ◽  
High Strength ◽  
Precipitation Strengthening ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Nb Microalloyed Steel ◽  
Carbon Microalloyed

Among modern weldable high strength steels, low carbon microalloyed steels have been widely used for linepipe, construction, and automobile industries. One of the major technical components to successfully produce these steels is to effectively use precipitation strengthening. In the present paper, the effect of an aging treatment on the microstructure and mechanical properties of a low carbon Nb-microalloyed steel is analyzed.

Studies on Softening Kinetics of Niobium Microalloyed Steel Using Stress Relaxation Technique

2012 ◽  
Vol 715-716 ◽  
pp. 794-799 ◽  
Author(s):  
Cheng Liang Miao ◽  
Cheng Jia Shang ◽  
Guo Dong Zhang ◽  
Guo Hui Zhu ◽  
Hatem S. Zurob ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Microalloyed Steels ◽  
Distinct Advantage ◽  
Low Carbon ◽  
Shape Processing ◽  
Physically Based ◽  
Near Net Shape ◽  
Niobium Microalloyed Steel ◽  
Relaxation Curves ◽  
Kinetics Of

Stress relaxation was studied in a series of low carbon, high Mn microalloyed steels containing 0.012, 0.06 and 0.1 wt% Nb. The stress-relaxation curves were modeled using a physically-based model that takes into account the time evolution of precipitation, recovery and recrystallization as well as their interactions. The results confirm that high Mn-high Nb design can offer distinct advantage over the low-Mn design for the application of near net shape processing.

Static Softening Behavior of Low Carbon High Niobium Microalloyed Steel

2020 ◽  
Vol 990 ◽  
pp. 36-43
Author(s):  
Dian Xiu Xia ◽  
Heng Ke Du ◽  
Xin En Zhang ◽  
Xiu Cheng Li ◽  
Ying Chao Pei
Keyword(s):  
Deformation Temperature ◽  
Static Recrystallization ◽  
Microalloyed Steel ◽  
Testing Machine ◽  
Low Carbon ◽  
High Deformation ◽  
Softening Behavior ◽  
Test Steel ◽  
Static Softening ◽  
Niobium Microalloyed Steel

The MMS-200 thermal simulation testing machine was used to study the static softening behavior of low carbon high niobium microalloyed steel. The effect of niobium to the static recrystallization softening behavior of the microalloy steel had been analyzed by establishing the kinetics model of static recrystallization and the micro-morphology of precipitates. The results indicated that: the static softening behavior of the tested steel significantly influenced by the deformation temperature and the interval pass time of the rolling processing. At relatively high deformation temperature and long interval pass time, the ratio of static softening was increased. Then the deformation temperature was lower to 950°C, and the static softening behavior of the test steel was ceased. But when the deformation temperature was higher than 1000°C, the static softening behavior of the test steel completely occurred. The activation energy of the test steel was 325·mol-1 by the established model calculated.

Effect of the Coupling of Recovery and Precipitation on the Recrystallization Behavior of Ti-Stabilized Extra Low Carbon Steels

2004 ◽  
Vol 467-470 ◽  
pp. 299-304 ◽  
Author(s):  
Eun Hye Na ◽  
Jae Young Choi ◽  
Baek-Seok Sung ◽  
Hu Chul Lee
Keyword(s):  
Annealing Treatment ◽  
Rolling Process ◽  
Carbon Steels ◽  
Recrystallization Temperature ◽  
Chemical Extraction ◽  
Recrystallization Behavior ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Alloy Chemistry ◽  
Relaxation Curves

The effect of carbo-nitride precipitation on the recrystallization behavior of Ti-stabilized extra low carbon steels was investigated. The precipitation behavior of titanium carbo-nitride was analyzed using transmission electron microscopy (TEM), a chemical extraction method, and the small angle neutron scattering (SANS) method. The recrystallization temperature was varied from 590°C to 680°C depending on the alloy chemistry and hot rolling process. The total amount of precipitates in the hot bands did not significantly affect the recrystallization temperature of the alloys. Isothermal annealing treatment showed a plateau in the stress relaxation curves, i.e. a delay in the recovery, when precipitation occurred during the annealing treatment. A model developed to explain the dynamic interaction of the precipitation with the recovery in the microalloyed austenite was successfully adopted to simulate the delay of the recovery during the recrystallization treatment of the cold rolled Ti-stabilized extra low carbon steels.

On the Effect of Strain Reversal on Static Recrystallisation and Strain-Induced Precipitation Process Kinetics in Microalloyed Steels

2012 ◽  
Vol 715-716 ◽  
pp. 655-660 ◽  
Author(s):  
K. Muszka ◽  
Lin Sun ◽  
Bradley P. Wynne ◽  
Eric J. Palmiere ◽  
W.M. Rainforth
Keyword(s):  
Dislocation Density ◽  
Strain Path ◽  
Microalloyed Steel ◽  
Microalloyed Steels ◽  
Precipitation Process ◽  
Flow Curves ◽  
Process Kinetics ◽  
Nb Microalloyed Steel ◽  
Strain Reversal ◽  
The Difference

Recent observations show that the strain reversal affects significantly and in a complex way both the static recrystallisation (SRX) and strain-induced precipitation (PPT) kinetics in Nb-microalloyed steel. It is already known that the recrystallisation stagnation is a consequence of the competition between the driving pressure for recrystallisation and the pinning pressure caused by the strain-induced precipitation of Nb (C,N) precipitates. Both of these parameters depend in turn on the local dislocation density. Thus, it is expected that a variation of the local dislocation density due to reversal of the strain will affect at the same time the local driving and the pinning pressures, which will cause the difference in the hardening levels. In the present paper, the influence of strain path change on microstructure evolution and mechanical behaviour in Nb-microalloyed steel (API X-70 grade) was studied. The deformation schedules were designed in order to investigate an effect of strain reversal on both static recrystallisation and strain-induced precipitation process kinetics. Flow curves recorded during deformation of X-70 steel showed clear influence of applied strain path on both static recrystallisation kinetics and strain-induced precipitation process.

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.

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