Factors Affecting the Inclusion Potency for Acicular Ferrite Nucleation in High-Strength Steel Welds

Kang, Yongjoon; Jeong, Seonghoon; Kang, Jun-Koo; Lee, Changhee

doi:10.1007/s11661-016-3456-0

Cited by 70 publications

(28 citation statements)

References 38 publications

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“…Em aços baixo carbono, maiores taxas de resfriamento do metal de solda podem favorecer a nucleação de ferrita no interior do grão, em forma de placas finas, sobre as inclusões formando a ferrita acicular [15,16]. Como os parâmetros de soldagem (temperatura de pré-aquecimento, espessura da peça e eficiência térmica do processo de soldagem) são os mesmos para os dois chanfros, a maior proporção de ferrita acicular no chanfro ½ V comparada à junta com chanfro V é explicada considerando o tipo de chanfro [5].…”

Section: Junta 1/2v Fa (%) Fp(g) (%) Fp (I) (%) Fs (A) (%) Fs (Na) (%unclassified

Características Microestruturais e Mecânicas ao Longo da Seção Transversal de Juntas Soldadas em Multipasses pelo Processo GMAW de um Aço API 5L X65Q

et al. 2017

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Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado.Recebido: 09 Abr., 2017 Aceito: 08 Ago., 2017 E-mail: vicentebraz@yahoo.com.br (VBT) Resumo: Características microestruturais e mecânicas foram avaliadas ao longo da seção transversal de juntas obtidas por soldagem (GMAW), de tubos sem costura de aço API 5L X65Q. Dois tipos de juntas foram obtidas a partir da confecção de chanfro V e ½ V. Dividindo-se as chapas soldadas em 8 camadas espaçadas de 3mm, no sentido transversal, corpos de prova foram confeccionados para ensaios de tração, microdureza Vickers e análise química. Foi realizada ainda caracterização metalográfica no metal base e nas juntas soldadas. Observou-se pequena alteração na composição química do metal de solda entre as camadas da junta V e junta ½ V. A maior taxa de resfriamento promoveu maior fração de ferrita acicular no chanfro ½ V. Alguns corpos de prova de tamanho reduzido não atenderam aos limites mínimos de escoamento e de resistência especificados na Norma API 5L, resultado atribuído à presença de descontinuidades em algumas regiões da solda. A maior microdureza Vickers da junta ½ V foi atribuída à maior presença de ferrita acicular. A adoção de chanfro estreito para aumento de produtividade na soldagem do aço em estudo não impactou negativamente as propriedades da junta, entretanto, aumentou a ocorrência de falta de fusão na face do bisel. Palavras-chave:Tubos sem costura; Aços API 5L X65Q; GMAW; Chanfro ½ V. Microstructural and Mechanical Characterization Across the Cross Section of Multipass GMAW Weld Joints of an API5L X65QAbstract: Microstructural and mechanical characteristics were evaluated along the cross section of joints obtained by (GMAW) of seamless API 5L X65Q steel pipes. Two types of joints were obtained from the bevel V and ½ V. By the division of the welded plates into 8 layers spaced 3 mm in the transverse direction, specimens were prepared for tensile tests, Vickers microhardness and chemical analysis. In addition, metallographic characterization was performed on the base metal samples and welded joints. It was observed a small change in the chemical composition of the weld metal between the 1st and 8th layer of the V joint and ½ V joint. The higher cooling rate of the ½ V bevel promoted higher acicular ferrite content. Some specimens of reduced size did not meet the minimum tensile properties limits specified in API 5L, a result attributed to the presence of discontinuities in some regions of the weld. The highest Vickers microhardness of the ½ V joint was attributed to the greater presence of the acicular ferrite. The adoption of narrow groove to improve the welding productivity did not negatively impact the properties of the joint, however, increased the occurrence of lack of fusion in the bevel face.Key-words: Seamless pipe; API 5L X65Q steel ...

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Section: Junta 1/2v Fa (%) Fp(g) (%) Fp (I) (%) Fs (A) (%) Fs (Na) (%unclassified

Características Microestruturais e Mecânicas ao Longo da Seção Transversal de Juntas Soldadas em Multipasses pelo Processo GMAW de um Aço API 5L X65Q

et al. 2017

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“…For the purpose of improving steel performance by AF transformation, the formation of effective inclusions and microstructural evolution behaviors have been two main study points. With respect to inclusion formation, studies have been concentrated on the deoxidation process and inclusion characterization [14,15], while research on microstructure transformation has mainly been carried out under static thermal treatment conditions without deformation processing. At present, the evaluation of the effect of inclusions on steel microstructure and properties under hot rolling and controlled cooling conditions is insufficient.…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermomechanical Treatment on Acicular Ferrite Formation in Ti–Ca Deoxidized Low Carbon Steel

Wang

Kang

et al. 2019

Metals

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Transformation behaviors and mechanical properties under thermomechanical treatment conditions of Ti–Ca deoxidized low carbon steel were studied in comparison to Al–Ca treated steel. A thermomechanical simulation and a hot rolling experiment were carried out. Inclusions and microstructures were characterized, and the transformation mechanism was analyzed. The results indicated that typical inclusions in Ti–Ca deoxidized steel were TiOx-MnS-Al2O3-CaO, TiOx-MnO-Al2O3-CaO, and TiOx-MnS, which were effective for acicular ferrite (AF) nucleation. Acicular ferrite formation temperature decreased with an increase in cooling rate. A fine AF dominant microstructure was formed under a high driving force for the transformation from austenite to ferrite at lower temperatures. A high deformation of 43–65% discouraged the formation of acicular ferrite because of the increase in austenite grain boundaries serving as nucleation sites. The fraction of high-angled grain boundaries that acted as obstacles to cleavage cracks was the highest in the sample cooled at 5 °C/s because of full AF structure formation. The hardness increased significantly as the cooling rate increased from 2 to 15 °C/s, whereas it decreased under the condition of deformation because of the formation of (quasi-)polygonal ferrite. By applying accelerated water cooling, the mechanical properties, particularly impact toughness, were significantly improved as a result of fine AF microstructure formation.

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“…Regarding Mn depletion region, however, Kang et al proposed another entirely different viewpoint based on the investigation about Mn depletion behavior in high‐strength low‐alloy steel weld metals. Their works demonstrate no MDZ formation around inclusions mainly composed of Ti 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti‐Containing Weld Metals of X70 Pipeline Steel

Wang

2017

steel research int.

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The X70 steel weld metals with Ti content of 0.003-0.13% are prepared by single pass submerged-arc welding process. The effects of Ti content in weld metals on the constituent phases of inclusions and potential of acicular ferrite nucleation on the inclusions are in detail investigated by means of electron probe micro-analysis, scanning transmission electron microscopy, and thermodynamic calculation. The obtained results show that with an increase of Ti content, primary constituent phases of inclusions are changed from (Mn-Al-Si-O) compound to a mixture of spinel and pseudobrookite solid solutions, eventually to pseudobrookite. The spinel solid solution is characterized by MnTi 2 O 4 constituent. The proportion of Ti 3 O 5 in pseudobrookite is increased remarkably with an increase in Ti content at the expense of MnTi 2 O 5 constituent. Compared with pseudobrookite, spinel has lower Ti concentration, but significantly higher Mn content regardless of Ti content in the weld metals. In the case of presence of a considerable amount of spinel primarily composed of MnTi 2 O 4 , Mn element is enriched strongly in the inclusions, resulting in the development of Mn-depleted zone in matrix around the inclusions, which enhances the capability of inclusions nucleating intragranular acicular ferrite.

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Factors Affecting the Inclusion Potency for Acicular Ferrite Nucleation in High-Strength Steel Welds

Cited by 70 publications

References 38 publications

Características Microestruturais e Mecânicas ao Longo da Seção Transversal de Juntas Soldadas em Multipasses pelo Processo GMAW de um Aço API 5L X65Q

Características Microestruturais e Mecânicas ao Longo da Seção Transversal de Juntas Soldadas em Multipasses pelo Processo GMAW de um Aço API 5L X65Q

Effect of Thermomechanical Treatment on Acicular Ferrite Formation in Ti–Ca Deoxidized Low Carbon Steel

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti‐Containing Weld Metals of X70 Pipeline Steel

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