Study of austenite grain size of microalloyed steel by simulating initial solidification during continuous casting

Li, Y.; Wen, Guangrui; Luo, Lan; Liu, J.; Tang, Ping

doi:10.1179/1743281214y.0000000197

Cited by 18 publications

(6 citation statements)

References 19 publications

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“…The original austenite grain size was dependent on the cooling intensity in the mold [ 27 , 28 ], and the mold vibration formed a periodic ‘oscillation mark’ on the surface of the continuous casting shell [ 29 ], thus deteriorating the shell heat transfer. At the same time, due to the ‘oscillation mark’ in the secondary cooling zone, intermittent contact between the secondary cooling rolls and the surface of the slab, and the uneven cooling of the nozzles, abnormally coarse austenite grains were produced on the surface of the slab.…”

Section: Resultsmentioning

confidence: 99%

Bending and Straightening of a Medium Carbon Steel Continuous Casting Slab with Low Temperature End Plastic Groove

Yang

Zhang

et al. 2022

Materials

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The high temperature brittleness range of medium carbon microalloyed steel under an actual continuous casting process was determined by the high temperature tensile test. The test results revealed that only a third of the brittle temperature range from 650–825 °C was due to intergranular ferrite in the experimental steel. In addition, it was found that the plastic recovery was fast and stable when the temperature was lower than 725 °C (the lowest plastic temperature). Bending/straightening operation in this temperature range was conducive to controlling the generation of corner cracks. In order to keep the corner temperature at the low temperature end of the plastic curve when the slab was bent/straightened, the cooling water scheme of the secondary cooling zone of the continuous caster was formulated by numerical calculation. By appropriately increasing the cooling water flow in the foot roll and the secondary cooling zones 1–5, the corner temperature of slab during bending operation was 600–700 °C, avoiding the brittle temperature range. The industrial test was then carried out. The results showed that after using the optimized water volume, the corner grains of the slab were uniform and the microstructure was mainly pearlite + ferrite. In addition, the abnormally large grain size was reduced, and a large amount of ferrite was generated inside the grain, which avoided stress concentration at the corner of the slab during bending/straightening operation, and basically eliminated the corner crack of the slab.

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Section: Resultsmentioning

confidence: 99%

Bending and Straightening of a Medium Carbon Steel Continuous Casting Slab with Low Temperature End Plastic Groove

Yang

Zhang

et al. 2022

Materials

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“…12. The precipitation of NbC in the casting after solidification is the main reason for such a decrease in the as-cast grain size as the grain size and grain growth are mainly affected by the solidification cooling rate and also the pinning effect of precipitates [58].…”

Section: -2-grain Sizementioning

confidence: 99%

Computational Design of a Novel Medium-Carbon, Low-Alloy Steel Microalloyed with Niobium

Javaheri

Nyyssönen

Grande

et al. 2018

J. of Materi Eng and Perform

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The design of a new steel with specific properties is always challenging owing to the complex interactions of many variables. In this work, this challenge is dealt with by combining metallurgical principles with computational thermodynamics and kinetics to design a novel steel composition suitable for thermomechanical processing and induction heat treatment to achieve a hardness level in excess of 600 HV with the potential for good fracture toughness. CALPHAD-based packages for the thermodynamics and kinetics of phase transformations and diffusion, namely Thermo-Calc ® and JMatPro ® , have been combined with an interdendritic segregation tool (IDS) to optimize the contents of chromium, molybdenum and niobium in a proposed medium-carbon low-manganese steel composition. Important factors taken into account in the modelling and optimization were hardenability and as-quenched hardness, grain refinement, and alloying cost. For further investigations and verification, the designed composition, i.e. in wt.% 0.40C, 0.20Si, 0.25Mn, 0.90Cr, 0.50Mo, was cast with two nominal levels of Nb: 0 and 0.012 wt.%. The results showed that an addition of Nb decreases the austenite grain size during casting and after slab reheating prior to hot rolling. Validation experiments showed that the predicted properties i.e. hardness, hardenability and level of segregation for the designed composition were realistic. It is also demonstrated that the applied procedure could be useful in reducing the number of experiments required for developing compositions for other new steels.

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“…Using the Runge-Kutta method, Equation (4) can be simplified to Equation (6). Impacted by precipitation at the boundary, the driving force will be counteracted by the pinning force.…”

Section: Austenite Growthmentioning

confidence: 99%

“…However, the hot ductility of micro-alloyed steels remains very poor during continuous casting, which leads to the formation of transverse cracks during the straightening process [3,4] . The influence factors of hot ductility in the third brittle zone include the size of austenite grain, carbonitride precipitation and pro-eutectoid ferrite film [5,6] . Research concerning the impact of Ti(C,N) precipitation on the growth of austenite mainly focuses on the hot Abstract: Austenite grain size is an important influence factor for ductility of steel at high temperatures during continuous casting.…”

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confidence: 99%

Influence of Ti(C,N) precipitates on austenite growth of micro-alloyed steel during continuous casting

Yang

Xue

et al. 2017

China Foundry

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A ccording to thermal mechanical control process and relaxation-precipitation controlling phase transformation technique during hot rolling process, the microstructure of steel can be refined by the addition of Ti-Nb microalloys [1,2] . A significant improvement in strength, toughness and weldability of steel can be obtained by Ti(C,N) precipitation. However, the hot ductility of micro-alloyed steels remains very poor during continuous casting, which leads to the formation of transverse cracks during the straightening process [3,4] . The influence factors of hot ductility in the third brittle zone include the size of austenite grain, carbonitride precipitation and pro-eutectoid ferrite film [5,6] . Research concerning the impact of Ti(C,N) precipitation on the growth of austenite mainly focuses on the hot Abstract: Austenite grain size is an important influence factor for ductility of steel at high temperatures during continuous casting. Thermodynamic and kinetics calculations were performed to analyze the characteristics of Ti(C,N) precipitates formed during the continuous casting of micro-alloyed steel. Based on Andersen-Grong equation, a coupling model of second phase precipitation and austenite grain growth has been established, and the influence of second precipitates on austenite grain growth under different cooling rates is discussed. Calculations show that the final sizes of austenite grains are 2.155, 1.244, 0.965, 0.847 and 0.686 mm, respectively, under the cooling rate of 1, 3, 5, 7, and 10 ℃·s rolling process at current stage [7][8][9][10][11] . However, there has been few investigations of austenite growth during continuous casting, which affects the ductility of steel directly. The formation of coarse austenite grain during soft cooling of strand surface below oscillation marks in slabs usually deteriorates ductility and causes transverse cracks in the straightening process. Therefore, the prediction of austenite grain size in micro-alloyed steels is very important.The main challenge in the size prediction of austenite grains is the computational complexity of f(t)/r(t) in the Andersen-Grong equation, where f is the volume fraction and r the radius of the precipitates, which is related to the nucleation and growth of precipitates at each state including temperature and time. By implementing some simulation models, Miettinen et al [12] fitted the results of Yasumoto's experimental data [13] using Equation (1). For the steel grade with carbon equivalent of 0.17%, the maximum grain size was found at the highest temperature for totally austenitic structure. Bernhard et al. [14] analyzed the influence of pinning

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Study of austenite grain size of microalloyed steel by simulating initial solidification during continuous casting

Cited by 18 publications

References 19 publications

Bending and Straightening of a Medium Carbon Steel Continuous Casting Slab with Low Temperature End Plastic Groove

Bending and Straightening of a Medium Carbon Steel Continuous Casting Slab with Low Temperature End Plastic Groove

Computational Design of a Novel Medium-Carbon, Low-Alloy Steel Microalloyed with Niobium

Influence of Ti(C,N) precipitates on austenite growth of micro-alloyed steel during continuous casting

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