Microstructural evolutions and impact toughness in simulated welding heat affected zones for a high-strength carbide-free bainitic rail steel

Bai, Wei; Xu, Xiaojun; Liu, Yaling; Liang, Yunxiao; Shen, Yanjun; Han, Zhi‐Yong; Sheng, Zhendong; Chen, Rong; Zhu, Minhao

doi:10.1016/j.msea.2023.145325

Cited by 5 publications

(2 citation statements)

References 52 publications

(60 reference statements)

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“…Alternating layers of ferrite and cementite in a lamellar structure, having a fully pearlitic microstructure. Carbon steels having a pearlitic microstructure are commonly used for railways [26]. In a softer ferrite matrix, oriented cementite lamellae make up the lamellar microstructure known as pearlite [27].…”

Section: Optical Microscopymentioning

confidence: 99%

Influences of preheating parameters on the quality of weld by thermite rail welding

Burapa,

Oo,

Sangwiman

et al. 2024

Mater. Res. Express

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The major goal of this study is to enhance the mechanical and metallurgical characteristics of rail steel grade R260 joined by thermite welding under various preheating conditions, including preheating time and gas pressure. Mainly two conditions, referred to as the normal condition and improved condition, are carried out for experiments. Prior to welding, the normal condition was preheated using liquefied petroleum gas (LPG) and oxygen gas pressures of 1 bar and 4.5 bar for 3 minutes, and the improved condition was preheated using liquefied petroleum gas and oxygen gas pressures of 1.2 bar and 4.5 bar for 6 minutes and 30 seconds. To investigate the mechanical and physical properties, micro-Vickers hardness tests, tensile tests and slow bending tests were also carried out. Welded metal in normal condition has many defects, including gas holes and shrinkage cavities. When comparing the Normal Condition to the Improved Condition, the Improved Condition demonstrates significantly more bending load and deflection. Specifically, the thermite welded rail sample of Improved Condition demonstrated a remarkable ability to endure bending loads of 108 tonnes and a deflection of 16 mm, and this sample remained unbroken until it exceeded 50% of the standardized deflection limit (10 mm). In addition, the average hardness values for the Improved Condition of the weld metal zone and the heat-affected zone were 331 HV and 289 HV, respectively. The normal condition produced an unsatisfactory fracture surface after slow bending test. This was caused by weld defects at the thermite weld due to inappropriate preheating.

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Section: Optical Microscopymentioning

confidence: 99%

Influences of preheating parameters on the quality of weld by thermite rail welding

Burapa,

Oo,

Sangwiman

et al. 2024

Mater. Res. Express

View full text Add to dashboard Cite

show abstract

“…In the past 40 years, many research, development and production practices on steel have proved that the online accelerated cooling process is an important means to improve the mechanical properties of hot-rolled steels [1][2][3][4][5][6][7][8] . Online accelerated cooling equipments were used widely in the production of heavy plate, strip, bars, wires, H-beams and rail, which made the application of microalloying technology and TMCP possible [9][10][11][12][13][14][15][16][17] . Unlike the above products, the seamless steel pipes are hollow structures, making it difficult to develop equipment that can simultaneously cool the inner and outer surfaces of steel pipe.…”

Section: Introductionmentioning

confidence: 99%

A New Type of Online Accelerated Cooling Equipment for Seamless Steel Pipe and Its Application Experiments

Tao,

Liu

2024

ISIJ Int.

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A new type of online accelerated cooling equipment for seamless steel pipe and its application experiments were introduced in the present work. The equipment can simultaneously cool the inner and outer surface of seamless steel pipes. By using online accelerated cooling process, the mechanical properties of the test steel pipe made of Q345B composition meet the requirements of Q460E steel grade index, with the yield strength of 460~475MPa, the tensile strength of 601~603MPa, the elongation of 21.5~26.5%, and the -40℃impact energy of 136J.

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The Low‐Temperature Toughness Improvement of High‐Strength Low‐Alloy Steel Due to the Microstructural Changes Caused by the Reheating/Rolling Temperature

Liu,

Zhao,

Tian

et al. 2024

steel research int.

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Herein, the microstructure, low‐temperature toughness, and fracture characteristics of high‐strength low‐alloy (HSLA) steel prepared by various thermomechanical control processes are systematically studied. Three different reheating/rolling temperatures are designed to obtain microstructures with different prior austenite grain sizes: 20.12 μm (S810), 27.58 μm (S910), and 35.19 μm (S1010). After hot rolling, S810 steel with smaller prior austenite grain size can provide high‐density deformed grain boundaries that promote ferrite phase transformation. The S910 and S1010 steels predominantly undergo bainite transformation as the prior austenite grain size and rolling temperature increase. Also, excellent low‐temperature toughness is obtained by reducing the reheating/rolling temperature (i.e., S810 steel), reflecting that Charpy impact energy of the core of the steel plate is 118.53 J at −120 °C. High performances is mainly attributed to the higher ferrite content, grain refinement, lower dislocation density, and higher proportion of high‐angle grain boundaries. Furthermore, fracture morphology analysis demonstrates that the S810 steel exhibits ductile fracture and noticeable plastic deformation at −120 °C, while S910 and S1010 steels exhibit brittle fracture and rapid crack propagation. These findings manifest the applicability of the suggested technique in preparing HSLA steel with excellent low‐temperature toughness.

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Microstructural evolutions and impact toughness in simulated welding heat affected zones for a high-strength carbide-free bainitic rail steel

Cited by 5 publications

References 52 publications

Influences of preheating parameters on the quality of weld by thermite rail welding

Influences of preheating parameters on the quality of weld by thermite rail welding

A New Type of Online Accelerated Cooling Equipment for Seamless Steel Pipe and Its Application Experiments

The Low‐Temperature Toughness Improvement of High‐Strength Low‐Alloy Steel Due to the Microstructural Changes Caused by the Reheating/Rolling Temperature

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