Microstructure-based approach to the evaluation of welded joints of bainitic rails designed for high-speed railways

Królicka, Aleksandra; Radwański, Krzysztof; Kuziak, R.; Zygmunt, Tomasz; Ambroziak, Andrzej

doi:10.1016/j.jcsr.2020.106372

Cited by 15 publications

(13 citation statements)

References 46 publications

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“…A high fraction of the LABs were identified, which proves the processes of cementite precipitation in ferrite subgrains. A similar distribution of misorientation angles was also found in the LTHAZ of the bainite rail after the welding process [33]. high temperature for early degradation of the structure.…”

Section: Low-temperature Heat-affected Zone and Base Materialssupporting

confidence: 78%

Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

et al. 2020

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One of the main limitations in application of nanostructured carbide-free bainite as a construction material is the difficulty of joining. This research presents a structural characterization of welded joints of medium carbon 55Si7 grade steel after the welding process with a regeneration technique as well as post welding heat treatment (PWHT). The hardness distribution of the welded joint with regeneration exhibit an overall decrease in hardness when compared to the base material and a significant decrease in hardness was observed in the heat-affected zone (HAZ). Unfavorable hardness distribution was caused by the presence of diffusion-type transformations products (pearlite) in the HAZ and bainite degradation processes. On the other hand, welding with the PWHT promotes the achievement of a comparable level of hardness and structure as in the base material. However, a slight decrease in hardness was observed in the weld zone due to the micro-segregation of the chemical composition caused by the indissoluble solidification structure. Based on the structural analysis, it was found that steel with relatively low hardenability (55Si7) should be welded using PWHT rather than a regeneration technique.

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Section: Low-temperature Heat-affected Zone and Base Materialssupporting

confidence: 78%

Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

et al. 2020

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“…[99] In turn, the misorientation angles of the materials after cyclic deformation were in the range of 55 to 60 deg, increasing with increased strain amplitude. Based on the previously reported results, [100][101][102] this range corresponds to the presence of martensite packages. This microstructure is characterised by ferrite/martensite crystallographic packets with austenite in the K-S orientation.…”

Section: B After Lcfmentioning

confidence: 92%

Studies of Bainitic Steel for Rail Applications Based on Carbide-Free, Low-Alloy Steel

Adamczyk‐Cieślak

Koralnik

Kuziak

et al. 2021

Metall Mater Trans A

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This paper describes the development and characterisation of bainitic steel for rail applications based on carbide-free, low-alloy steel. The results show that after rolling and subsequently cooling, the designed carbide-free bainitic steel exhibits better mechanical performance than standard pearlitic steel. This is because of its fine, carbide-free bainitic microstructure, which consists of bainitic ferrite and retained austenite laths. Microstructural and mechanical property analysis was carried out using scanning and transmission electron microscopy, X-ray diffraction, hardness measurements, tensile and low-cycle fatigue tests. The obtained results demonstrate that during low cyclic deformation, a partial transformation of the retained austenite into deformed martensite α′ takes place, and strain-induced martensitic transformation occurs. The initial strengthening of the material during low-cycle fatigue was caused by the transformation of austenite into martensite and the increase in the dislocation density of the steel. In addition, an optimal amount of retained austenite in the form of thin layers and islands (dimensions not exceeding 1 µm) made it possible to obtain a high yield while maintaining the high plasticity of the steel. These microstructural features also contributed to the high crack resistance of the tested carbide-free bainitic steel.

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“…An industrial resistance welding machine was utilized to perform welding process. The detailed welding process parameters are provided in Królicka et al [9]. It should be mentioned that the performed welding process was conducted in the field, with industrial conditions being in accordance with the standard joining conditions.…”

Section: Methodsmentioning

confidence: 99%

“…In just 2 years, significant research reports have been published in terms of low-carbon bainitic steels intended for applications in railway infrastructure. The latest investigations cover a wide range of issues including microstructure optimization considering alloying additives [1] and processing techniques [2]; manufacturing process [3]; heat treatments methods [4]; wear resistance [5]; rolling contact fatigue [6]; lowcycle fatigue performance [7]; fatigue crack growth rate [8]; and analysis of welding processes [9]. The mechanical properties of bainitic steels, compared with those of conventional ones, are promising and * E-mail: aleksandra.krolicka@pwr.edu.pl indicate the possibility of enhancing the durability of railway tracks, especially under heavy loads.…”

Section: Introductionmentioning

confidence: 99%

“…The welding of bainitic rails is relatively poorly known in terms of the metallurgical changes occurring during this process. In a previous work [9], the authors analyzed the changes in the microstructure occurring in the flash-butt welded joint of low-carbon, continuous cooled bainitic steel. It should be emphasized that this welding method is typical for conventional rail joining.…”

Section: Introductionmentioning

confidence: 99%

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Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Królicka

Żak

Kuziak

et al. 2021

Materials Science-Poland

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The joining process of bainitic rails is significant in terms of their industrialization in high-speed and heavy-loaded railways. This paper demonstrates the microstructure changes in the critical zone of the welded joint, which is responsible for the greatest deterioration in mechanical properties. Extensive progress in the decomposition of the retained austenite and bainitic ferrite occurs in the low-temperature heat-affected zone (LTHAZ) of the flash-butt welded joint of low-carbon bainitic rail. The decomposition products of the retained austenite were mainly a mixture of cementite and ferrite. The cementite was mainly precipitated at the boundary of the bainitic ferrite laths, which indicates lower thermal stability of the filmy austenite. Moreover, it was found that a part of the refined blocky retained austenite was decomposed into the ferrite and nanometric cementite, while another remained in the structure. The decomposition mechanisms are rather heterogeneous with varying degrees of decomposition. A relatively high proportion of dislocations and stress fields prove the occurrence of residual stresses formed during the welding process.

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Microstructure-based approach to the evaluation of welded joints of bainitic rails designed for high-speed railways

Cited by 15 publications

References 46 publications

Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

Studies of Bainitic Steel for Rail Applications Based on Carbide-Free, Low-Alloy Steel

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

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