Welding Capabilities of Nanostructured Carbide-Free Bainite: Review of Welding Methods, Materials, Problems, and Perspectives

Królicka, Aleksandra; Ambroziak, Andrzej; Żak, Andrzej

doi:10.3390/app9183798

Cited by 16 publications

(8 citation statements)

References 45 publications

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“…Overall, bainitic ferrite and retained austenite during tempering processes at sufficiently high temperatures are degraded into a mixture of cementite and ferrite [19]. The LTHAZ affected by the temperature below Ac 1 can be compared to the rapid tempering processes [20]. Thus, the de-composition mechanisms should be comparable to the tempering processes.…”

Section: Resultsmentioning

confidence: 99%

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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Section: Resultsmentioning

confidence: 99%

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 microstructural state of the weld metal and the heat-affected zone is the most important factor in the mechanism of hydrogen embrittlement, cracking and reduction in impact toughness [ 5 , 6 ]. The desired fine-grained microstructure is often achieved in welding using an optimal thermal cycle [ 7 , 8 , 9 ] and through minimizing the content of impurities and segregations making the grain structure more refined [ 10 ]. Another effective metallurgical solution is to refine the microstructure using a mechanism of heterogeneous grain nucleation at non-metallic inclusions and acicular ferrite when refractory oxides, sulfides, and nitrides are formed [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Electrochemical Composite Coatings with LaF3-LaB6 Particles in Nickel–Copper Matrix on the Metallurgical Processes in Arc Welding of Low Alloy Ferrite-Pearlite Steels

et al. 2021

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Development of welding consumables with fluorides and borides of rare earth metals is a promising area for improving the weldability of low alloy steels. As lanthanum fluoride and boride dissociate, lanthanum and boron dissolve in the weld pool and the welding arc plasma is saturated with fluorine. As a result of FeO, MnO, SiO2 deoxidation and FeS, MnS desulfurization, refractory lanthanum sulfides and oxides La2O3, La2S3 are formed in the weld pool, which can be the crystallization nuclei in the weld pool and the origin of acicular ferrite nucleation. The paper proposes a model of metallurgical processes in the arc and weld pool, as well as a model of electrochemical adsorption of Ni2+ cations in colloidal electrolytes during electrostatic deposition of nano-dispersed insoluble particles of LaF3 or LaB6 on the surface of wire. The paper discusses the constructional design of the welding wire and the technology for forming electrochemical composite coatings with copper and nickel matrix. The composite wires applied in the welding of low alloy steels make it possible to refine the microstructure, increase the tensile strength by 4% and the impact toughness of welds by 20%.

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“…The high mechanical properties (tensile strength above 2000 MPa, yield strength at least 1100 MPa, and elongation up to 14% [1][2][3][4][5][6]) are determined mainly by the structural factor consisting of nanometric scale widths of the bainitic ferrite laths (below 100 nm) and film-like austenite (even 20-40 nm [3]). One of the main limitations of industrial applications of NB CFB steels as constructional material is the difficulty of the welding processes [7,8]. Carbon equivalent (CEV or CE) is the most common tool to determine the weldability of steels.…”

Section: Introductionmentioning

confidence: 99%

“…The weakest point of welded joints is the Low-Temperature Heat-Affected Zone (LTHAZ) [8,12,13], where the temperature below the lower transformation temperature (A 1 ) is affected. In this zone, the degradation of nanostructured carbide-free bainite occurs.…”

Section: Introductionmentioning

confidence: 99%

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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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Welding Capabilities of Nanostructured Carbide-Free Bainite: Review of Welding Methods, Materials, Problems, and Perspectives

Cited by 16 publications

References 45 publications

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

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

The Effect of Electrochemical Composite Coatings with LaF3-LaB6 Particles in Nickel–Copper Matrix on the Metallurgical Processes in Arc Welding of Low Alloy Ferrite-Pearlite Steels

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

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