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

Béal, Coline; Caliskanoglu, Ozan; Sommitsch, Christof; Ilie, Sergiu; Six, Jakob; Dománková, Mária

doi:10.4028/www.scientific.net/msf.879.199

Cited by 5 publications

(10 citation statements)

References 12 publications

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“…The first evaluation of the alloy ductility was made at the usual continuous casting strain rate of 10 −3 s −1 , [ 1,8,10 ] at different temperatures, so that an overview of the hot ductility behavior could be obtained. At least two experiments have been conducted for each testing temperature.…”

Section: Resultsmentioning

confidence: 99%

“…[ 2 ] This lower ductility, and specially the ductility minimum observed in Figure 1a, is mainly associated with two phenomena, which are the formation of precipitates and ferrite films at austenite grain boundaries. [ 1,2,6,7,9,10 ] The occurrence of both is not only influenced by the temperature, but also by the deformation applied. Some of the ferrite present in the material is induced by deformation during the tensile test and is responsible for the ductility trough.…”

Section: Discussionmentioning

confidence: 99%

“…The temperature cycle used can be seen in previous studies. [ 10,14,15 ] The samples were heated until the melting point, where the surface temperature was measured around 1450 °C, and held at this temperature for 90 s to ensure that the material was evenly heated until the center and the solution of all precipitates. Then, the sample was cooled, first at a rate of 5 °C s −1 until 1250 °C, followed by a second rate of 1 °C s −1 until the desired test temperature, which was held for 10 s before the start of straining.…”

Section: Methodsmentioning

confidence: 99%

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Effect of Strain Rate on the Hot Ductility Behavior of a Continuously Cast Ti–Nb Microalloyed Steel

Gontijo

Hoflehner

Estermann

et al. 2020

steel research int.

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During the continuous casting process, alloys may be more susceptible to crack initiation under some conditions due to lower ductility. A Ti–Nb microalloyed steel is subjected to in situ melted hot tensile tests to evaluate its hot ductility behavior. The ductility is examined at different strain rates and temperatures. The samples are heated with an induction coil to the melting temperature in a vacuum atmosphere. Afterward, they are cooled to the desired test temperatures. Hot tensile tests are conducted by a thermomechanical simulator with strain rates varying from 10−5 to 10−2 s−1. The results show a ductility minimum around 800 °C for the standard strain rate of 10−3 s−1 and a significant influence of the changes in strain rate in the behavior of the alloy for all the tested temperatures. The fracture surfaces are compared for 700, 800, and 900 °C at 10−4, 10−3, and 10−2 s−1, as well as the microstructure. Computer simulations are done for the determination of the transformation temperatures, Scheil–Gulliver solidification simulation, and analysis of the precipitation kinetics during the tests. The results from simulations are discussed in comparison with the ones seen experimentally.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Effect of Strain Rate on the Hot Ductility Behavior of a Continuously Cast Ti–Nb Microalloyed Steel

Gontijo

Hoflehner

Estermann

et al. 2020

steel research int.

Self Cite

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“…This lower ductility is known to be caused by two main factors, the austenite-ferrite transformation, and the nucleation of precipitates, depending strongly on the alloying elements present [6,[9][10][11]. Due to the lower strength of ferrite in comparison to austenite, the strain that concentrates in the ferrite films formed in the austenite grain boundaries initiate cracks as a result [8,10,12]. In the context of the nucleation of precipitates, local hardening occurs, provoking stress concentration and promoting the initiation of cracks [4,12].…”

Section: Introductionmentioning

confidence: 99%

“…Due to the lower strength of ferrite in comparison to austenite, the strain that concentrates in the ferrite films formed in the austenite grain boundaries initiate cracks as a result [8,10,12]. In the context of the nucleation of precipitates, local hardening occurs, provoking stress concentration and promoting the initiation of cracks [4,12].…”

Section: Introductionmentioning

confidence: 99%

Holding Time Influence on the Hot Ductility Behavior of a Continuously Cast Low Alloy Steel

Gontijo

Hoflehner

Ilie

et al. 2020

Metals

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Cracking during the continuous casting process is undesirable and continuous work is being carried out to find further improvements and understand the mechanisms that lead to failure. Investigations on the hot ductility behavior of a continuously cast low alloyed steel using different holding times before straining were done in the present work. Samples were heated to melting temperature in a vacuum atmosphere and then cooled to one of the three test temperatures chosen: 750, 850, and 900 °C. When the desired temperature was reached, the sample was isothermally held for either 10, 90, 300, or 3600 s before the tensile test started, with a strain rate of 10−3 s−1. The reduction of area was measured, SEM images of the fractured surfaces were taken plus LOM images for the analysis of the microstructure. The results show that there was no significant change in the ductility at any of the temperatures until 300 s, with a change in behavior at 3600 s. This was further confirmed with the images and precipitation kinetics simulations. The results are described and compared.

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Hot Ductility Evolution Mechanism of Titanium‐Bearing Microalloyed Steels

Liu

Zheng

et al. 2023

steel research int.

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Titanium‐bearing (Ti‐bearing) microalloyed steels have high strength and toughness by grain refinement effect of carbonitride precipitates. However, they can induce surface cracks of continuous casting slab when the Ti alloyed content is high. A microalloyed steel with Ti content (0.10–0.15 wt%) is carried out by thermalmechanical simulator over 600–1350 °C to analyze hot ductility evolution mechanism. Fracture surface morphology, phase transition, and behavior of precipitates of the tensile samples are investigated by experimental detection and thermodynamic calculation. The ductility–temperature curves show that the third brittle temperature range is 600–890 °C, which is mainly attributed to the thin proeutectoid ferrite film and precipitated titanium carbonitride particles, widening the embrittlement temperature ranges through of steel. In addition, the tensile samples at 890–1350 °C have good hot ductility, indicating the dynamic recrystallization of deformed austenite can trigger grain boundaries migration away from cracks and avoid the side effect of the Ti (C,N) particles on hot ductility. The first brittle temperature range of 1350 °C‐melting point is mainly ascribed to the partial melting of the grain boundaries with element segregation of sulfur and phosphorus, and microporosity loose among dendrites.

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

Cited by 5 publications

References 12 publications

Effect of Strain Rate on the Hot Ductility Behavior of a Continuously Cast Ti–Nb Microalloyed Steel

Effect of Strain Rate on the Hot Ductility Behavior of a Continuously Cast Ti–Nb Microalloyed Steel

Holding Time Influence on the Hot Ductility Behavior of a Continuously Cast Low Alloy Steel

Hot Ductility Evolution Mechanism of Titanium‐Bearing Microalloyed Steels

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