Effect of Cr and isothermal holding temperature on microstructure and properties of complex phase steel with high formability (CH steel)

Chu, Xiaohong; Gao, Pengfei; Chen, Weijian; Li, Feng; Kang, Tao; Zhao, Yan; Yin, Xiandong; Zhao, Zhengzhi

doi:10.1007/s42243-022-00813-4

Cited by 4 publications

(7 citation statements)

References 32 publications

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“…The precipitates in each test steel are spherically or nearly spherically, and EDS analysis revealed that the precipitates are composed of (Nb, Ti) C. Precipitates were also analyzed in our other studies. [ 25 ] When the QT is low, a considerable number of small‐sized precipitates are present in the QT140 sample, as shown in Figure 6a,e. The fraction of large‐sized precipitates rises continuously as the QT increases (from 140 to 300 °C), whereas that of small‐sized precipitates drops.…”

Section: Resultsmentioning

confidence: 99%

Effect of Quenching Temperature on the Strengthening Mechanism of Low‐Carbon Microalloyed Quenching and Partitioning Steel

Chu

Chen

Liu

et al. 2022

steel research int.

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Herein, the microstructures of the low‐carbon microalloyed quenching and partitioning (Q–P) steels are multiphase with ferrite (F), martensite (M), and retained austenite (RA) at different quenching temperatures (QTs), i.e., 140, 180, 240, and 300 °C. The volume fraction of fresh martensite (FM) increases from 8.6% to 61.4%, but the tempered martensite (TM) decreases from 49.7% to 0% with the QT increase. Meanwhile, the size of the precipitates (Nb, Ti)C tends to increase, whereas the fraction of the precipitates decreases first and then increases. With the increase of the QT, the yield strength (YS) decreases, the tensile strength (TS) increases, and the elongation first increases and then decreases. Additionally, the strengthening mechanism of Q–P steel is quantitatively analyzed in terms of F, M, RA, and precipitation strengthening. This study shows that F makes the same contribution to YS for the tested steels. The major strengthening mechanism of the Q–P steel is contributed by M, which accounts for about 43.7% to 56.0% of total YS. RA greatly influences the plasticity of Q–P steel and provides little to YS. With an increase in QT, the precipitation strengthening values first decrease and then increase.

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Section: Resultsmentioning

confidence: 99%

Effect of Quenching Temperature on the Strengthening Mechanism of Low‐Carbon Microalloyed Quenching and Partitioning Steel

Chu

Chen

Liu

et al. 2022

steel research int.

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“…The chemical composition of the test steel is Fe-0.17C-1.60(Si+Al)-2.65Mn-0.30Cr-0.20Mo-0.08(Nb+Ti) (wt.%) and the quenching device dilatometer Bähr DIL805A (Thermoanalyse GmbH, Hüllhorst, Germany) was used to test the austenite transformation start temperature (A c1 ), which was 704 • C, and the austenite transformation end temperature (A c3 ), which was 972 • C [9,10]. After smelting, forging, and hot rolling, a hot-rolled sheet with a thickness of 4 mm was obtained after five rolling passes.…”

Section: Materials and Heat Treatmentmentioning

confidence: 99%

“…In order to quantify each phase, XRD was used to test the volume fraction of retained austenite and its carbon content, and dilatometry was used to test the bainite content. The bainite contents were approximately estimated by the change in the linear thermal expansion coefficient (LTEC) due to the LTEC of each phase in the steel being different, and we also used this method in previous studies [9,10,17]. The XRD test results, dilatometry changes in the isothermal bainite zone, and the quantitative analysis results are shown in Figures 3 and 4.…”

Section: Effect Of Annealing Temperature On Microstructure Of Ch Steelmentioning

confidence: 99%

“…Cr retards the bainite transformation and refines the grain size of CH steel, and Cr promotes the precipitation of (Nb, Ti)C in the high-temperature austenite region. The strength has an increasing tendency and the total elongation has a decreasing tendency with the increase in isothermal temperature [9]. The lower recrystallization rate promotes bainite transformation and increases the dislocation strengthening, grain refinement strengthening, and precipitation strengthening of CH steel [10].…”

Section: Introductionmentioning

confidence: 98%

“…However, with the trend of improving strength and achieving lightweight automobile parts, CH steel with its wide application is urgently needed to achieve high strength and formability. In existing studies, the effects of composition, isothermal temperature, and precursors on the microstructure and properties of CH steel have been explored [9,10]. Cr retards the bainite transformation and refines the grain size of CH steel, and Cr promotes the precipitation of (Nb, Ti)C in the high-temperature austenite region.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Chu,

Zhou,

Liu

et al. 2024

Metals

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In recent years, with the continuous improvement in the requirements for automobile steel formability, complex phase steel with high formability (CH steel) has been widely used. In the present study, the microstructure of CH steel was regulated using the actual production process as a basis and annealing temperature as a variable, and the effects of annealing temperature on the microstructure, properties, and fracture behavior of CH steel were analyzed. As the annealing temperature increases, the ferrite content decreases from 36.3% to 0, the martensite content decreases from 49.3% to 8.8%, the bainite content increases from 11.9% to 87.1%, and the retained austenite content first increases and then decreases within the range of 2.5~5.1%. Consequently, the tensile strength shows a decreasing trend, the yield strength first decreases and then increases, and the total elongation and the hole expansion ratio first increase and then decrease. The deformation coordination of each phase gradually becomes better, and the voids and cracks in the tensile and hole expansion samples expand along the ferrite and martensite or martensite/austenite (M/A) island interface, transforming into the bainitic ferrite and martensite or M/A islands. The test steel’s best tensile and hole expansion properties occur at annealing temperatures of 940 °C.

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Enhanced strength–ductility synergy of multiphase steels via regulation of austenite decomposition during annealing

et al. 2023

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Effect of Cr and isothermal holding temperature on microstructure and properties of complex phase steel with high formability (CH steel)

Cited by 4 publications

References 32 publications

Effect of Quenching Temperature on the Strengthening Mechanism of Low‐Carbon Microalloyed Quenching and Partitioning Steel

Effect of Quenching Temperature on the Strengthening Mechanism of Low‐Carbon Microalloyed Quenching and Partitioning Steel

Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Enhanced strength–ductility synergy of multiphase steels via regulation of austenite decomposition during annealing

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