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 Effect of High Temperature Deformation on the Hot Ductility of Nb Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 115-122 ◽  
Author(s):  
Faramarz Zarandi ◽  
Steve Yue
Keyword(s):  
Continuous Casting ◽  
High Temperatures ◽  
Microalloyed Steel ◽  
Casting Process ◽  
Temperature Deformation ◽  
Hot Ductility ◽  
Continuous Casting Process ◽  
Billet Surface ◽  
Nb Microalloyed Steel ◽  
Very High

Low hot ductility of steel at the straightening stage of the continuous casting process is a problem found in steels containing microalloying and/or certain alloying additions. The thermal schedule undergone by the billet surface in the mill has a significant effect on the hot ductility. In this work, thermomechanical processing was employed to alleviate the problem of hot ductility in the Nb-microalloyed steel. Specimens were melted in situ and subjected to the billet surface thermal schedule in order to generate a microstructure similar to that present at the straightening stage of the continuous casting process. Some deformation schedules were incorporated with the thermal schedule at very high temperatures, specifically during solidification, within the d-ferrite region, and during the d®g transformation, and the hot ductility was subsequently evaluated at the end of the thermal schedule where the straightening operation is performed. After the thermal schedule alone, the steel exhibited a very low hot ductility at the straightening stage. It was found that deformation at very high temperatures prior to the straightening stage had a considerable effect on the hot ductility, either detrimental or beneficial, depending on the region in which the deformation has been executed. The mechanisms leading to loss and improvement of hot ductility are explained in this paper.

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.

Research of Transverse Corner Crack and Optimization of Concasting Process for Bloom of Peritectic Steel Q235D

2011 ◽  
Vol 284-286 ◽  
pp. 1115-1119
Author(s):  
Cheng Gong Yao ◽  
Shou Qian Yuan ◽  
Lie Chen ◽  
Zhi Jun Wang ◽  
Hai Long Wang ◽  
...  
Keyword(s):  
Crack Formation ◽  
Cooling Water ◽  
Casting Process ◽  
Electromagnetic Stirring ◽  
Continuous Casting Process ◽  
Steel Composition ◽  
Corner Crack ◽  
Peritectic Steel ◽  
Casting Production

Q235D is one kind of peritectic steel, so the casting production inevitably encounter the universality defects of peritectic steel casting. The bloom(250mm×280mm) of Q235D is produced by 60t consteel EBT—LF(VD)—CC process at Xining Special Steel. The main problem in the production is the transverse corner crack, finally lead to occur the cracks and “triangular gaps” at surface of round bar（Φ130mm）after rolled. In order to eliminate the defects caused by transverse corner crack of bloom, the morphology and microstructure and principle of crack formation is researched. The results showed that the crack is caused by stress along the intergranular, and no obvious segregation and particles founded around the defects. The following parameters on the continuous casting process are optimized: steel composition, superheat, the choice of a various slag, the cooling water of different section, casting speed and the electromagnetic stirring parameters. Finally the cracking defects of the bloom is eliminated, and the quality of the bar is optimized.

scholarly journals Effects of Sn and Sb on the Hot Ductility of Nb+Ti Microalloyed Steels

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1679
Author(s):  
Chunyu He ◽  
Jianguang Wang ◽  
Yulai Chen ◽  
Wei Yu ◽  
Di Tang
Keyword(s):  
Laser Scanning ◽  
Microalloyed Steel ◽  
Confocal Laser Scanning Microscope ◽  
Microalloyed Steels ◽  
Confocal Laser ◽  
Hot Ductility ◽  
High Temperature Mechanical Properties ◽  
Ductility Trough ◽  
Gleeble 3500 ◽  
Fracture Morphologies

Referencing the composition of a typical Nb+Ti microalloyed steel (Q345B), two kinds of steels, one microalloyed with Sn and Sb, and the other one only microalloyed with Sb were designed to study the effects of Sn and Sb on the hot ductility of Nb+Ti microalloyed steels. The Gleeble-3500 tester was adopted to determine the high-temperature mechanical properties of the two test steels. Fracture morphologies, microstructures and interior precipitation status were analyzed by SEM, CLSM (Confocal laser scanning microscope) and EDS, respectively. Results revealed that within the range of 950–650 °C, there existed the ductility trough for the two steels, which were mainly attributed to the precipitation of TiN and Nb (C, N). Additionally, precipitation of Sn and Sb were not observed in this research and the hot ductility was not affected by the addition of Sn and Sb, as compared with the Nb+Ti microalloyed steel. Therefore, addition of a small amount of Sn and Sb (≤0.05 wt.%) to the Nb+Ti microalloyed steel is favorable due to the improvement on corrosion resistance.

scholarly journals The Influence of Ti on the Hot Ductility of Nb-bearing Steels in Simulated Continuous Casting Process.

2002 ◽  
Vol 42 (3) ◽  
pp. 273-282 ◽  
Author(s):  
Haiwen Luo ◽  
L. Pentti Karjalainen ◽  
David A. Porter ◽  
Heidi-Marja Liimatainen ◽  
Yan Zhang
Keyword(s):  
Continuous Casting ◽  
Casting Process ◽  
Hot Ductility ◽  
Continuous Casting Process ◽  
Bearing 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.

scholarly journals Hot ductility behavior of a continuously cast Ti-Nb microalloyed steel

2019 ◽  
Author(s):  
Christian HOFLEHNER ◽  
Coline BEAL ◽  
Christof SOMMITSCH ◽  
Jakob SIX ◽  
Sergio ILIE
Keyword(s):  
Microalloyed Steel ◽  
Hot Ductility ◽  
Continuously Cast ◽  
Nb Microalloyed Steel
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