Ultrahigh strength-toughness combination in Bainitic rail steel: The determining role of austenite stability during tempering

Wang, Kai‐Kai; Tan, Zhunli; Gao, Guhui; Gui, Xuchun; Misra, R.D.K.; Bai, Bin

doi:10.1016/j.msea.2016.03.043

Cited by 75 publications

(35 citation statements)

References 31 publications

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“…Compared to the steel in [16] (0.22C-2.0Mn-1.0Si-0.8Cr-0.8(Mo + Ni) (wt %)), the steel in the present work (0.22C-1.5Mn-1.6Si-1.5Cr-0.41Ni-0.37Mo (wt %)) contained more Si and Cr to suppress the formation of brittle cementite and obtain high-strength carbide-free bainite. In addition, the amount of RA in this work (maximum ~15.5 vol %) was much larger than that in [16] (maximum ~8.8 vol %), which also improved the mechanical properties of bainite steel by the TRIP effect. Moreover, the maximum tensile strength of conventional pearlite rail is below 1300 MPa with inferior impact toughness.…”

Section: Retained Austenitementioning

confidence: 98%

“…Therefore, the real bainite It is known that RA may decompose to other microstructures such as ferrite, bainite, martensite and carbides during tempering [23]. The carbon contents in RA were calculated by Equation (1) [16] according to the location of austenite peaks and results are shown in Figure 8b:…”

Section: Retained Austenitementioning

confidence: 99%

“…Some researchers focused on the optimization of chemical composition of bainite rail and the microstructure-property relationship in bainite rail [16][17][18][19]. Wang et al [16] designed a bainite rail with the chemical compositions of 0.22C-2.0Mn-1.0Si-0.8Cr-0.8(Mo + Ni) (wt %).…”

Section: Introductionmentioning

confidence: 99%

“…Wang et al [16] designed a bainite rail with the chemical compositions of 0.22C-2.0Mn-1.0Si-0.8Cr-0.8(Mo + Ni) (wt %). They found that the toughness of bainite rail steel is closely related to the stability of retained austenite [16,17]. Gui et al [18] reported that thin film-like retained austenite plays a significant role on the crack propagation of rolling contact fatigue.…”

Section: Introductionmentioning

confidence: 99%

“…In order to relieve the residual stress and further improve the toughness of bainite rail, tempering is usually necessary treatment. Wang et al [16] developed a tempered bainite rail steel with tensile strength of 1388 MPa. However, the study on the effects of tempering on the microstructure and properties of bainite rail is very limited.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Tempering on the Microstructure and Properties of a High-Strength Bainite Rail Steel with Good Toughness

Zhu

Zhou

et al. 2018

Metals

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An advanced bainite rail with high strength-toughness combination was produced in a steel mill and the effects of tempering on the microstructure and properties of the bainite rail steel were investigated by optical microscopy, transmission electron microscopy, electron back-scattering diffraction and X-ray diffraction. Results indicate that the tensile strength, elongation and impact toughness were about 1470 MPa, 14.5% and 83 J/cm 2 , respectively, after tempering at 400 • C for 200 min. Therefore, a high-strength bainite rail steel with good toughness was developed. In addition, the amount of retained austenite (RA) decreased due to bainite transformation after low-temperature tempering (300 • C) and RA almost disappeared after high-temperature tempering (500 • C). Moreover, as the tempering temperature increased, the tensile strength of the rail head first decreased due to the decreased dislocation density and carbon content in bainite ferrite and the coarseness of bainite ferrite, and then increased because of carbide precipitation at high-temperature tempering. Furthermore, RA played a significant role in the toughness of bainite rail. The elongation and toughness of the rail obviously decreased after tempering at 500 • C for 200 min because of the disappearance of RA and appearance of carbides.

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Section: Retained Austenitementioning

confidence: 98%

Section: Retained Austenitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effects of Tempering on the Microstructure and Properties of a High-Strength Bainite Rail Steel with Good Toughness

Zhu

Zhou

et al. 2018

Metals

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Role of Prior Martensite in a 2.0 GPa Multiple Phase Steel

Cui

Northwood

Liu

2018

steel research int.

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A 55Mn2SiCr steel is developed by a novel multiple-step process, which involves austenitizing at 900 C for 30 min, rapid quenching to 210 C, then holding at 170 C for 5 min, and isothermally holding at 250 C for different times, and finally cooling in air. The mixed microstructure consists of lenticular prior martensite (PM), fine needle bainitic ferrite (BF), and filmy retained austenite (RA). The results show that the highest tensile strength of 2030 MPa with a bending strength of 4000 MPa is achieved at 250 C for 120 min. This is attributed to a synergistic multiphase strengthening effect. The presence of martensite formed during the quenching process prior to the isothermal treatment, accelerates the kinetics of subsequent nano-scaled super bainitic transformation by bainitic laths nucleating quickly at the martensite-austenite interfaces. The product of austenite fraction and its carbon content is found to be another important factor for controlling the strength. In addition, the phase evolution as well as carbon partitioning mechanism during isothermal treatment is discussed.

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Effect of Intercritical Austenitizing Temperature during Quenching–Intercritical Quenching–Tempering Process on Toughness of 25Mn2Si2Cr Bainitic Steel

Tan

Zhang

et al. 2019

steel research int.

Self Cite

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An intercritical quenching process is introduced between conventional water quenching and tempering to 25Mn2Si2Cr bainitic steel. The study suggests that the quenching–intercritical quenching–tempering (Q–IQ–T) process effectively improves mechanical properties compared with conventional air cooling and tempering (Q–T). When the intercritical austenitizing temperature is 860 °C, as‐treated steel's tensile strength, yield strength, impact energy (U‐notch) is 1453 MPa, 1141 MPa, and 99 J cm−2, respectively, which is enhancement of 5.4%, 3.2%, and 20.7% compared with the conventional Q–T process. The increase of toughness is achieved without compromising strength. The improvement of toughness arises from refinement of grain size and microstructure.

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Ultrahigh strength-toughness combination in Bainitic rail steel: The determining role of austenite stability during tempering

Cited by 75 publications

References 31 publications

Effects of Tempering on the Microstructure and Properties of a High-Strength Bainite Rail Steel with Good Toughness

Effects of Tempering on the Microstructure and Properties of a High-Strength Bainite Rail Steel with Good Toughness

Role of Prior Martensite in a 2.0 GPa Multiple Phase Steel

Effect of Intercritical Austenitizing Temperature during Quenching–Intercritical Quenching–Tempering Process on Toughness of 25Mn2Si2Cr Bainitic Steel

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