Effect of Strain-Induced Precipitation on the Austenite Non-recrystallization (Tnr) Behavior of a High Niobium Microalloyed Steel

Rajinikanth, V.; Kumar, T. V. Vineeth; Mahato, B.; Chowdhury, Sandip Ghosh; Sangal, S.

doi:10.1007/s11661-019-05488-3

Cited by 9 publications

(8 citation statements)

References 33 publications

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“…Boratto test [24] was inspired by the industrial practice and designed to determine Tnr temperature, as the lowest temperature above which full static recrystallization takes place. Therefore, Tnr temperatures are, in all cases, related to an equal amount of recrystallized fraction, enabling plotting lnt vs.1/Tnr dependence [39][40][41]. Fig.…”

Section: Static Recrystallizationmentioning

confidence: 99%

Some aspects of physical metallurgy of microalloyed steels

Radović

Vukicevic²,

Glišić

et al. 2020

Metall Mater Eng

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Some aspects of deformation, precipitation, and recrystallization behavior in medium carbon V-microalloyed and low carbon Nb/Ti-microalloyed steels are presented in the paper. Changes in microstructure are explained together with methods of quantification. The temperature of No-recrystallization (Tnr) is defined as a milestone to show the onset of retardation of recrystallization while the apparent activation energy for hot working shows the extent of this retardation. In the case of high cooling rates, this method is not sufficiently sensitive and Trl (recrystallization limit temperature) and Trs (recrystallization stop temperature) must be evaluated from softening data. Paper presented the possibility to estimate Tnr temperature on six stands finishing train at Hot Strip Mill in HBIS Iron and Steel Serbia, Smederevo as well as the activation energy for static recrystallization, QSRX, derived from Tnr temperatures.

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Section: Static Recrystallizationmentioning

confidence: 99%

Some aspects of physical metallurgy of microalloyed steels

Radović

Vukicevic²,

Glišić

et al. 2020

Metall Mater Eng

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“…Several techniques are cited in the literature for obtaining fractional softening from the true stress–true strain data including the offset method 16 , 18 , 19 , the 0.05 true strain method 29 , the mean flow stress method 30 , and the back-extrapolation method 31 . For the present work, the 0.05 true strain method was selected to calculate fractional softening based on its extensive use in the literature and evidence suggesting that it correlates well with the recrystallized fraction 2 , 15 – 17 , 29 . Using the 0.05 true strain method, fractional softening at each temperature was calculated according to Eq.…”

Section: Methodsmentioning

confidence: 99%

“…From the double-hit compression test, T nr is defined as the temperature corresponding to a fractional softening of 0.2 as determined from Eq. ( 1 ) 2 , 17 . This definition of T nr is based on the consideration that 20 pct of the total softening is typically attributed to recovery rather than recrystallization 18 .…”

Section: Introductionmentioning

confidence: 99%

Double twist torsion testing to determine the non recrystallization temperature

Ballard

Speer

Findley

et al. 2021

Sci Rep

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A double-twist torsion testing technique has been developed using a 316 stainless steel as an exemplar material to experimentally assess recrystallization behavior and determine the non-recrystallization temperature (Tnr). This new method was compared to the traditional methods of double-hit compression and multi-step hot torsion testing. The double-twist torsion test allows Tnr to be related to the extent of austenite recrystallization through measurements of fractional softening while accommodating multiple deformation and recrystallization steps with a single specimen. The double-twist torsion test resulted in average Tnr values similar to those determined with multi-step hot torsion, and a partially recrystallized microstructure was observed in the vicinity of the calculated Tnr for all three methods. The ability of the double-twist torsion test to relate the experimental Tnr to the evolution of austenite recrystallization via fractional softening measurements while incorporating effects of multiple deformation steps offers an advantage over traditional methods for quantifying changes in austenite recrystallization during thermomechanical processing.

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“…The nose of the C-curve for this precipitation in austenite is around 900 • C for 0.04 wt.% Nb, but is raised to 950 • C or higher at larger levels of Nb [3,13]. As mentioned above, studies of the recrystallization-stop-temperature, T 5% or T nr , indicate that this temperature increases with Nb content and can reach or exceed 1050 • C in typical pipe steels containing 0.1% Nb [6,14]. Since the last roughing passes occur in this temperature range, it is quite possible that there might be strain-induced precipitation of NbC, even in the late roughing passes.…”

Section: Introductionmentioning

confidence: 91%

Rational Alloy Design of Niobium-Bearing HSLA Steels

Almatani

DeArdo

2020

Metals

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In the 61 years that niobium has been used in commercial steels, it has proven to be beneficial via several properties, such as strength and toughness. Over this time, numerous studies have been performed and papers published showing that both the strength and toughness can be improved with higher Nb additions. Earlier studies have verified this trend for steels containing up to about 0.04 wt.% Nb. Basic studies have shown that the addition of Nb increases the recrystallization-stop temperature, T5% or Tnr. These same studies have shown that with up to about 0.05 wt.% of Nb, the T5% temperature increases in the range of finish rolling, which is the basis of controlled rolling. These studies also have shown that at very high Nb levels, exceeding approximately 0.06 wt.% Nb, the recrystallization-stop temperature or T5% can increase into the temperature range of rough rolling, and this could result in insufficient grain refinement and recrystallization during rough rolling. However, the question remains as to how much Nb can be added before the detriments outweigh the benefits. While the benefits are easily observed and discussed, the detriments are not. These detriments at high Nb levels include cost, undissolved Nb particles, weldability issues, higher mill loads and roll wear and the lessening of grain refinement that might otherwise occur during plate rough rolling. This loss of grain refinement is important, since coarse grained microstructures often result in failure in the drop weight tear testing of the plate and pipe. The purpose of this paper is to discuss the practical limits of Nb microalloying in controlled rolled low carbon linepipe steels of gauges ranging from 12 to 25 mm in thickness.

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Effect of Strain-Induced Precipitation on the Austenite Non-recrystallization (Tnr) Behavior of a High Niobium Microalloyed Steel

Cited by 9 publications

References 33 publications

Some aspects of physical metallurgy of microalloyed steels

Some aspects of physical metallurgy of microalloyed steels

Double twist torsion testing to determine the non recrystallization temperature

Rational Alloy Design of Niobium-Bearing HSLA Steels

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