Solidification Behaviour and Microstructural Development of Iron-based Alloys under Conditions Pertinent to Strip Casting – 200 Series Stainless Steels

Mukunthan, Kannappar; Hodgson, Peter; Strezov, L.; Stanford, Nicole

doi:10.2355/isijinternational.53.2152

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…As-cast specimens of 36 × 36 mm 2 and 1.2 mm thickness were produced using dip tester at Deakin University [25], which can simulate fast cooling during solidification between twin rolls in strip casting process [24,26]. The dip tester is used to immerse a copper substrate into molten steel for a short and controlled period of time and then immediately lift it out to simulate rapid solidification [27].…”

Section: Materials and Experimental Techniques 21 Processing Routementioning

confidence: 99%

Microstructures and mechanical properties of TRIP steel produced by strip casting simulated in the laboratory

Xiong

Kostryzhev

Saleh

et al. 2016

Materials Science and Engineering: A

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Conventional transformation induced plasticity (TRIP) steel (0.17C-1.52Si-1.61Mn-0.03Al, wt%) was produced via strip casting technology simulated in the laboratory. Effects of holding temperature, holding time and cooling rate on ferrite formation were studied via analysis of the continuous cooling transformation diagram obtained here. A typical microstructure for conventional TRIP steels consisting of ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite was obtained. However, coarse prior austenite grain size of ~80 μm led to large polygonal ferrite grain size of ~17 μm, coarse second phase regions of ~21 μm size, small amount of retained austenite (0.02-0.045) and the presence of Widmanstätten ferrite. Optimisation of the microstructure-property relationship was reached via a variation in the isothermal bainite transformation temperature. The highest retained austenite fraction of 0.045±0.003 with medium carbon content of 1.23±0.01 wt% was obtained after holding at 400 °C, resulting in the highest ultimate tensile strength of 590±35 MPa and largest total elongation of 0.27±0.05. The presence of TRIP effect in the studied steel was revealed through the analysis of strain hardening exponent and modified Crussard-Jaoul model. Effect of processing parameters on retained austenite retention and stress-strain behaviour was discussed. Conventional transformation induced plasticity (TRIP) steel (0.17C-1.52Si-1.61Mn-0.03Al, wt. %) was produced via strip casting technology simulated in the laboratory. Effects of holding temperature, holding time and cooling rate on ferrite formation were studied via analysis of the continuous cooling transformation diagram obtained here. A typical microstructure for conventional TRIP steels consisting of ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite was obtained. However, coarse prior austenite grain size of ~ 80 μm led to large polygonal ferrite grain size of ~ 17 μm, coarse second phase regions of ~ 21 μm size, small amount of retained austenite (0.02 -0.045) and the presence of Widmanstätten ferrite. Optimisation of the microstructure-property relationship was reached via a variation in the isothermal bainite transformation temperature. The highest retained austenite fraction of 0.045±0.003 with medium carbon content of 1.23±0.01 wt. % was obtained after holding at 400 °C, resulting in the highest ultimate tensile strength of 590±35 MPa and largest total elongation of 0.27±0.05. The presence of TRIP effect in the studied steel was revealed through the analysis of strain hardening exponent and modified Crussard -Jaoul model. Effect of processing parameters on retained austenite retention and stress-strain behaviour was discussed.

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Section: Materials and Experimental Techniques 21 Processing Routementioning

confidence: 99%

Microstructures and mechanical properties of TRIP steel produced by strip casting simulated in the laboratory

Xiong

Kostryzhev

Saleh

et al. 2016

Materials Science and Engineering: A

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“…Compared to hot and cold rolling, the strip casting eliminates many procedures, such as rough rolling and reheating, resulting in a decrease in gas emission, energy consumption and operation cost [15]. However, the large prior austenite grain size (PAGS) (approximately 100 -200 μm) complicates tuning of the microstructure via the adjustment of heat treatment parameters [15,16]. It is well known that the PAGS dictates the final microstructure of the transformation products at room temperature such that refining the former leads to a fine grain size of the latter [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

Xiong

Kostryzhev

Liang

et al. 2016

Materials Science and Engineering: A

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Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially. Abstract: Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially.

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“…Figure 5 shows that for the carbon-free specimen, the alloy solidified first as ferrite (the blue phase in Figure 5). This is evidenced by the large columnar grains indicative of the as-solidified structure in these strip casting simulations [14,16-18]. Upon further cooling, the specimen then underwent partial solid state phase transformation from ferrite to austenite, developing classical Widmanst¨atten shaped austenite colonies.…”

Section: Discussionmentioning

confidence: 94%

The microstructure of high manganese TWIP steels produced via simulated direct strip casting

Othman

Dorin

Stanford

et al. 2022

Materials Science and Technology

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Three TWIP steels based on the composition Fe-23Mn-3Si-3.3Al with different carbon concentrations were examined. The alloys were produced by rapid solidification in an experimental apparatus designed to simulate direct strip casting conditions. Examination of the driving force for solidification for this alloy showed the preference for BCC and FCC solidification were very close for this composition, within 10% of one another. This factor combined with the high undercooling resulted in the change in the primary solidified phase. Chemical analysis of the as-cast strip showed inter-dendritic segregation of Si and Al, but negligible segregation of Mn. A simple heat treatment was sufficient to chemically homogenise all alloys and produce microstructures comprising a fully austenitic structure, consistent with thermodynamic predictions.

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Solidification Behaviour and Microstructural Development of Iron-based Alloys under Conditions Pertinent to Strip Casting – 200 Series Stainless Steels

Cited by 8 publications

References 10 publications

Microstructures and mechanical properties of TRIP steel produced by strip casting simulated in the laboratory

Microstructures and mechanical properties of TRIP steel produced by strip casting simulated in the laboratory

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

The microstructure of high manganese TWIP steels produced via simulated direct strip casting

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