Academic literature on the topic 'Bainite, steel, hot rolling, retained austenite'
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Journal articles on the topic "Bainite, steel, hot rolling, retained austenite"
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Lv, Wei, Di Wu, and Zhuang Li. "Development of Laminar Flow Cooling of Ultra-High Strength Ferrite-Bainite Dual Phase Steel." Applied Mechanics and Materials 184-185 (June 2012): 940–43. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.940.
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In the present paper, controlled cooling in different ways was performed using a laboratory hot rolling mill in ultra-high strength hot rolled ferrite-bainite dual phase (DP) steel. The results have shown that the final microstructures of DP steel comprise ferrite, bainite and a small amount of retained austenite and martensite. DP steel has a tensile strength ranging from 1010 to 1130MPa and yet retains considerable total elongation in the range of 14–17%. The addition of Mn and Nb to DP steel leads to the maximum ultimate tensile strength, yield strength and the product of ultimate tensile strength and total elongation due to the formation of retained austenite and granular bainite structure. Laminar flow cooling after hot rolling results in a significant increase in the quantity of ferrite and bainite due to the suppression of pearlite transformation, and as a result, the present steel possesses high strengths and good toughness.
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Li, Zhuang, Di Wu, Wei Lv, and Ming Fu Shao. "Phase Transformation Behavior during Continuous Cooling of Fe-C-Mn-Si Multiphase Steels." Applied Mechanics and Materials 377 (August 2013): 123–27. http://dx.doi.org/10.4028/www.scientific.net/amm.377.123.
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In the present paper, controlled cooling of Fe-C-Mn-Si multiphase steel was conducted by a laboratory hot rolling mill. The results show that polygonal ferrite, granular bainite and the stable retained austenite can be obtained through hot deformation and subsequent two steps cooling pattern. The amount of ferrite increased with the duration of intermediate air cooling during controlled cooling. The formation of the bainitic ferrite resulted in the carbon concentration enrichment in austenite further during the simulated coiling. This increases the stability of the remaining austenite. Satisfactory mechanical properties can be obtained through hot rolling process and two steps cooling pattern in this work due to the TRIP effect of the stable retained austenite.
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Li, Zhuang, Di Wu, and Ming Fu Shao. "Controlled Rolling and Controlled Cooling Technology of Fe-C-Mn-Si Multiphase Steel." Applied Mechanics and Materials 377 (August 2013): 107–11. http://dx.doi.org/10.4028/www.scientific.net/amm.377.107.
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In the present paper, controlled rolling and controlled cooling of Fe-C-Mn-Si multiphase steel was conducted by a laboratory hot rolling mill. The results show that ferrite (grey), granular bainite (black) and retained austenite (white) and/or MA islands (white) are observed in a color etched LOM micrograph. The presence of the retained austenite is confirmed by SEM observation. Controlled rolling and controlled cooling technology contributes to the improvement of the microstructure. Excellent mechanical properties for Fe-C-Mn-Si multiphase steel are attributed to the TRIP effect of the stable retained austenite.
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Kliber, Jiří, Gabriela Plestilova, Ondrej Zacek, and Mahesh C. Somani. "Effects of Thermomechanical Processing on Microstructure and Mechanical Properties Multiphase Steels Exhibiting a TRIP Effect." Materials Science Forum 539-543 (March 2007): 4357–62. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4357.
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Effects of hot-rolling conditions on these steels are much less studied than their importance for practice would suggest. It should be emphasized that bainite transformation is the key reaction to enrich non-transformed austenite with carbon. This study was carried out in order to gain understanding of the effect of thermomechanical hot rolling on final microstructure and mechanical properties of C-Mn-Si TRIP steel. Fundamental of the transformation induced plasticity effect – TRIP is the stabilization of substantial amount of retained austenite down to the ambient temperature by thermomechanical processing and its subsequent transformation into strain induced martensite as a consequence of applied plastic deformation. The special prepared stepped specimens were rolled on laboratory tandem mill. The effects of finish rolling temperature, strain and isothermal bainite transformation temperature on mechanical properties of mentioned TRIP steel were evaluated (mechanical properties were examined with tension test). Major deformation, higher finishing rolling temperature and higher temperature of bainite hold result in drop in strength. Proportionately to the drop in strength, the ductility grows in the TRIP steel. Microstructures were examined with X-ray diffraction (retained austenite). Image analysis software was used to process SEM micrographs of structure (ferrite, bainite assessment). Plastometric testing was conducted on GLEEBLE 3800 thermo-mechanical simulator. First stage of experiment yielded stress-strain curves for various temperatures and strain rates. Gleeble 1500 was used for the remaining plastometric simulation. Specimens were reheated to austenitization temperature of 1100°C and soaked. Then they were cooled to the temperature of deformation and subsequently cooled at higher rate down to the bainitic transformation temperature (400 – 550 °C). Specimens were held at the bainitic transformation temperature and then air-cooled. Final microstructures were evaluated with respect to transformation diagrams and optical microscopy findings. Higher bainite volume fraction was found in the specimens cooled at higher cooling rate as compared with more slowly cooled specimens.
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Skowronek, Adam, Dariusz Woźniak, and Adam Grajcar. "Effect of Mn Addition on Hot-Working Behavior and Microstructure of Hot-Rolled Medium-Mn Steels." Metals 11, no. 2 (February 19, 2021): 354. http://dx.doi.org/10.3390/met11020354.
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Hot plastic working behavior and microstructure evolution were investigated during a production process of four medium-Mn steels, which differed in Mn (3 and 5%) and Nb contents. The production process started with casting, followed by hot forging, rough hot-rolling and concluded with final thermomechanical processing, which was performed to obtain multiphase bainite-based alloys with some fractions of retained austenite. The rough rolling was composed of four passes with total true strain of 0.99 and finishing rolling temperature of 850 °C, whereas thermomechanical processing contained five passes and total true strain of 0.95 at a finishing rolling temperature of 750 °C. During the process, the force parameters were recorded, which showed that the rolling forces for steels containing 3% Mn are higher compared to the 5% Mn alloys. There was no significant influence of Nb on the rolling parameters. The produced as-cast microstructures were composed of dendritic bainitic-martensitic phases. A positive effect of Nb micro-addition on a refinement of the as-cast structure was noticed. The thermomechanical processed steels showed fine multiphase microstructures with some fractions of retained austenite, the fraction of which depended on the Mn content in steel. The steels containing 3% Mn generated higher forces both during rough and thermomechanical rolling, which is related to slower recrystallization softening in these alloys compared to the steels containing 5% Mn.
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Kuziak, Roman, Zofia Kania, Valeriy Pidvysots'kyy, Hans Roelofs, Monika Pernach, and Maciej Pietrzyk. "Through Process Modelling of Rolling and Controlled Cooling of TRIP Assisted Bainitic Steel Rods and Prediction of the Retained Austenite in Products." Materials Science Forum 892 (March 2017): 23–33. http://dx.doi.org/10.4028/www.scientific.net/msf.892.23.
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Simulation of the rolling and controlled cooling sequence for bainitic steel rods was the general objective of the paper. The main focus was put on exploring possibility of prediction of the retained austenite occurrence in TRIP assisted bainitic steels. Existing discrete phase transformation models require long computing times and their application to optimization of industrial processes is limited. Therefore, a model based on the modified JMAK equation was proposed. The occurrence of the retained austenite was predicted by carbon distribution calculations in the austenite during bainite transformation. This model was implemented into the FE software for simulation of cooling of rods. The model was verified by comparison of results with the physical simulations during rolling in the pilot mill and during cooling. The first part of the paper contains thermal-mechanical-microstructural simulations of rod hot rolling process. The objective of this part was to determine temperature and grain size distribution at the rod cross section at the beginning of phase transformations. FE simulations of the cooling were performed next. Correlation between cooling parameters and the volume fraction of the retained austenite in rod was determined.
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Lee, Hak Cheol, Xiao Dan Wu, Young Min Kim, and Nack J. Kim. "Effect of Second Phase on Mechanical Properties of Bainite-Base Steels." Advanced Materials Research 15-17 (February 2006): 780–85. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.780.
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Effects of acicular ferrite and retained austenite on the mechanical properties of bainite-base steels were investigated. Various morphology and volume fraction of constituent phases have been obtained by control of hot rolling conditions and alloy compositions. It has been shown that the steels containing retained austenite have better combinations of strength and ductility than the ones with no retained austenite. However, there is no noticeable change in DBTT by the incorporation of retained austenite in the microstructure since retained austenite exists as fine particles. On the other hand, DBTT of the steels are largely affected by the presence of acicular ferrite in the microstructure. EBSD analyses of fractured Charpy specimens show that cracks are deflected within the morphological packet of acicular ferrite, indicating its role in reducing the effective grain size of the steels.
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Tian, Yu, Zhunli Tan, Ji Li, Bo Gao, Min Zhang, and Bingzhe Bai. "Low Temperature Deformation Induced Microstructure Refinement and Consequent Ultrahigh Toughness of a 20Mn2SiCrNi Bainitic Steel." Metals 10, no. 1 (December 21, 2019): 19. http://dx.doi.org/10.3390/met10010019.
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In this paper, we have studied the influence of deformation on the microstructure and mechanical properties of 20Mn2SiCrNi bainitic high strength steel processed through a hot rolling route. Simulation of different temperatures and degrees of deformation was carried out via Gleeble-1500. The study suggested that grain size is refined when the deformation is carried out at lower temperature (> Ac3). When the degree of deformation was increased from 20% to 60%, grain size and microstructure were both refined and the size of retained austenite was reduced. The tensile strength increased from 1345 MPa to 1432 MPa. The impact toughness increased from 115 J/cm2 to 210 J/cm2 at room temperature, from 63 J/cm2 to 142 J/cm2 at −40 °C. Furthermore, it was observed that the microstructure after air cooling was composed of granular bainite (GB), lath bainite (LB) and martensite/austenite (MA) island for different deformation conditions. The study reveals that the impact toughness of 20Mn2SiCrNi bainitic high strength steel can be increased by increasing the degree of deformation.
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Rana, R., S. Chen, A. Haldar, and S. Das. "Mechanical Properties of a Bainitic Steel Producible by Hot Rolling." Archives of Metallurgy and Materials 62, no. 4 (December 1, 2017): 2331–38. http://dx.doi.org/10.1515/amm-2017-0342.
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AbstractA carbide-free bainitic microstructure is suitable for achieving a combination of ultra high strength and high ductility. In this work, a steel containing nominally 0.34C-2Mn-1.5Si-1Cr (wt.%) was produced via industrial hot rolling and laboratory heat treatments. The austenitization (900°C, 30 min.) and austempering (300-400°C, 3 h) treatments were done in salt bath furnaces. The austempering treatments were designed to approximately simulate the coiling step, following hot rolling and run-out-table cooling, when the bainitic transformation would take place and certain amount of austenite would be stabilized due to suppression of carbide precipitation. The microstructures and various mechanical properties (tensile properties, bendability, flangeability, and room and subzero temperature impact toughness) relevant for applications were characterized. It was found that the mechanical properties were highly dependent on the stability of the retained austenite, presence of martensite in the microstructure and the size of the microstructural constituents. The highest amount of retained austenite (~ 27 wt.%) was obtained in the sample austempered at 375°C but due to lower austenite stability and coarser overall microstructure, the sample exhibited lower tensile ductility, bendability, flangeability and impact toughness. The sample austempered at 400°C also showed poor properties due to the presence of initial martensite and coarse microstructure. The best combination of mechanical properties was achieved for the samples austempered at 325-350°C with a lower amount of retained austenite but with the highest mechanical stability.
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Kliber, Jiří, Bohuslav Mašek, Ondrej Zacek, and H. Staňková. "Transformation Induced Plasticity (TRIP) Effect Used in Forming of Carbon CMnSi Steel." Materials Science Forum 500-501 (November 2005): 461–70. http://dx.doi.org/10.4028/www.scientific.net/msf.500-501.461.
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Transformation induced plasticity (TRIP) steel combines high strength and high ductility that makes it particularly suitable for forming. Martensite within a ferrite matrix is usually obtained either by continuous casting of slabs followed by hot rolling (which is the fastest method, hence the most economical one, producing, however, relatively thick products) or by the continuous casting of slabs followed by hot rolling, cold rolling and annealing (the method used for thin products). High cooling rates, low coiling temperatures and low reduction during hot deformation were generally found to suppress the formation of polygonal ferrite and promote the presence of retained austenite. This paper focuses on development and modifications of two CMnSi-based TRIP steels with 0,23 % C;1,4 % Mn; 1,9 % Si; ( 0,08 % Nb) by means of laboratory thermomechanical processing. Description of experimental devices for the analysis of transformation plasticity under tensioncompression loading is given. Experiments were carried out on the simulator for thermaldeformation cycles SMITWELD and TANDEM was used for thermomechanical processing on the laboratory rolling mill. The maximum volume fraction of retained austenite and the resulting optimum combination of tensile strength and ductility were achieved in testing heats. Special attention was paid to volume fraction changes of single phases and to changes in morphology of phases. The results suggest that rather short isothermal bainite transformation times are sufficient to obtain TRIP microstructure. The influence of parameters of thermomechanical processing such as the amount of strain, forming temperature and austenitization time and temperature on microstructures of TRIP steels were evaluated.
Dissertations / Theses on the topic "Bainite, steel, hot rolling, retained austenite"
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Korpala, Grzegorz. "Gefügeausbildung und mechanische Eigenschaften von unlegiertem bainitischem Warmband mit Restaustenit." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-229501.
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Seit vielen Jahren wächst die Nachfrage bezüglich sparsamer Fahrzeuge; die Autohersteller konkurrieren miteinander und werben mit neuen Fahrzeugkonzepten, in denen hochmoderne Werkstoffe ihre Anwendung finden. In dieser Arbeit werden Legierungskonzepte und entsprechende Warmwalztechnologien einer ultrahochfesten bainitischen Stahlsorte mit Restaustenit vorgestellt, die der genannten Anwendung angepasst werden können. Der gewählte Werkstoff gehört zu den Stählen mit mittleren Kohlenstoffgehalten, die sich nach der - im Rahmen dieser Arbeit entwickelten - Behandlung durch hohe Zugfestigkeit bei vergleichsweise hoher Bruchdehnung auszeichnen. Es werden erweiterte Modelle zur Beschreibung der Phasenumwandlung von Stählen im Bainitgebiet vorgestellt. Die Ergebnisse aus den Experimenten wurden genutzt, um die Modelle zu ergänzen und zu evaluieren. Dabei wird nicht nur der Warmwalzprozess, sondern auch die chemische Zusammensetzung der Stähle selbst optimiert. Die hier präsentierte Arbeit erstreckt sich über die gesamte Produktionskette und zeigt geeignete Herstellungsbedingungen, die in Betriebsanlagen leicht realisierbar sind und umgesetzt wurden.
Conference papers on the topic "Bainite, steel, hot rolling, retained austenite"
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Sanchez, Nuria, Özlem E. Güngör, Martin Liebeherr, and Nenad Ilić. "Development of X80M Line Pipe Steel for Spiral Welded Pipes With Low Temperature Toughness and Excellent Weldability." In 2014 10th International Pipeline Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/ipc2014-33502.
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The unique combination of high strength and low temperature toughness on heavy wall thickness coils allows higher operating pressures in large diameter spiral welded pipes and could represent a 10% reduction in life cycle cost on long distance gas pipe lines. One of the current processing routes for these high thickness grades is the thermo-mechanical controlled processing (TMCP) route, which critically depends on the austenite conditioning during hot forming at specific temperature in relation to the aimed metallurgical mechanisms (recrystallization, strain accumulation, phase transformation). Detailed mechanical and microstructural characterization on selected coils and pipes corresponding to the X80M grade in 24 mm thickness reveals that effective grain size and distribution together with the through thickness gradient are key parameters to control in order to ensure the adequate toughness of the material. Studies on the softening behavior revealed that the grain coarsening in the mid-thickness is related to a decrease of strain accumulation during hot rolling. It was also observed a toughness detrimental effect with the increment of the volume fraction of M/A (martensite/retained austenite) in the middle thickness of the coils, related to the cooling practice. Finally, submerged arc weldability for spiral welded pipe manufacturing was evaluated on coil skelp in 24 mm thickness. The investigations revealed the suitability of the material for spiral welded pipe production, preserving the tensile properties and maintaining acceptable toughness values in the heat-affected zone. The present study revealed that the adequate chemical alloying selection and processing control provide enhanced low temperature toughness on pipes with excellent weldability formed from hot rolled coils X80 grade in 24 mm thickness produced at ArcelorMittal Bremen.
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Sharma, Udit, and Douglas G. Ivey. "Microstructure of Microalloyed Linepipe Steels." In 2000 3rd International Pipeline Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/ipc2000-125.
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The aim of this study was to characterize the microstructure of microalloyed linepipe steels. The steels investigated were X70 (0.04 wt% C - 0.02 wt% Ti - 0.07 wt% Nb) and X80 (0.04 wt% C - 0.025 wt% Ti - 0.09 wt% Nb) steels, where the numbers refer to their specified minimum yield strength (SMYS) in ksi. This class of steels has the advantage of high strength and good toughness combined with minimal wall thickness (15.5 mm for X70 steel). These attributes result in considerable cost savings when installation of several hundreds of kilometers of pipeline is required for oil and natural gas recovery and transport. The present study focused on phase identification and quantification, distribution of alloying elements and inclusions and segregation effects. Both steels were primarily composed of a mixed ferrite structure, i.e., polygonal ferrite and acicular ferrite/bainite, with characteristic low angle grain boundaries and high dislocation densities. The proportion of acicular grains was higher for the X80 steel. Pockets of retained austenite, exhibiting a Kurdjumov-Sachs orientation relationship (KS-OR) with the adjoining ferrite, were found in both steels. Five general classes of precipitates were identified in both steels: 1) Very large (2–10 μm) cuboidal TiN particles nucleated on inclusions; 2) large (0.1–1.0 μm) cuboidal TiN particles; 3) medium sized (30–50nm), irregular shaped Nb-Ti carbonitrides; 4) fine (<20nm), rounded precipitates of Nb carbonitrides with traces of Mo; 5) very fine dispersed precipitates (<5 nm in size). For X80 steels many of the large TiN precipitates were observed with Nb-rich carbonitrides precipitated epitaxially on them. Inclusion content and morphology were analyzed in both steels. The inclusions in X70 steels were found to be primarily CaS with significant amounts of Al, O, Ti, Fe and Mn. They were essentially spherical in shape with small elliptical distortions along the rolling direction and across the width of the plate. The morphology of the inclusions in the X80 steel was very similar, however, they showed higher Mn levels.