scholarly journals The Evolution and Distribution of Microstructures in High-Energy Laser-Welded X100 Pipeline Steel

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1762 ◽  
Author(s):  
Gang Wang ◽  
Limeng Yin ◽  
Zongxiang Yao ◽  
Jinzhao Wang ◽  
Shan Jiang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Laser Welding ◽  
Grain Boundaries ◽  
Welded Joints ◽  
Pipeline Steel ◽  
High Energy ◽  
Electron Backscattered Diffraction ◽  
Boundary Density ◽  
Energy Beam ◽  
X100 Pipeline Steel

High-energy beam welding was introduced for pipeline steel welding to reduce pipeline construction costs and improve the efficiency and safety of oil and gas transportation. Microstructures and their distribution in X100 laser-welded joints, which determine the joints’ strength and toughness, are discussed in this paper. Welded joints were prepared by an automatic 10,000-watt robot-based disc laser-welding platform for 12.8 mm thick X100 pipeline steel. Then, the grain, grain boundary, orientation, and distribution pattern of each zone of the welded joints were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electron backscattered diffraction (EBSD) analysis techniques. The results showed that the grain boundary density, contents of the high-angle and low-angle grain boundaries, distribution states, and evolution trends of coincident site lattice (CSL) grain boundaries were essentially the same in each zone from the base metal (BM) to the weld of the X100 pipeline steel laser-welded joint. The relative content of grain boundaries above 55°, which were composed of the Σ3 type CSL grain boundary, showed a considerable impact on the mechanical properties of the joint. The content of twin grain boundaries was closely related to the thermal cycles of laser welding, and the effect of the cooling rate was greater than that of the process of austenization.

scholarly journals Quantitative Correlation between Thermal Cycling and the Microstructures of X100 Pipeline Steel Laser-Welded Joints

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 121 ◽  
Author(s):  
Gang Wang ◽  
Jinzhao Wang ◽  
Limeng Yin ◽  
Huiqin Hu ◽  
Zongxiang Yao
Keyword(s):  
Temperature Field ◽  
Laser Welding ◽  
Oil And Gas ◽  
Welded Joint ◽  
Pipeline Steel ◽  
High Energy ◽  
Welding Temperature ◽  
Energy Beam ◽  
Quantitative Correlation ◽  
X100 Pipeline Steel

Due to the limitations of the energy density and penetration ability of arc welding technology for long-distance pipelines, the deterioration of the microstructures in the coarse-grained heat-affected zone (HAZ) in welded joints in large-diameter, thick-walled pipeline steel leads to insufficient strength and toughness in these joints, which strongly affect the service reliability and durability of oil and gas pipelines. Therefore, high-energy-beam welding is introduced for pipeline steel welding to reduce pipeline construction costs and improve the efficiency and safety of oil and gas transportation. In the present work, two pieces of X100 pipeline steel plates with thicknesses of 12.8 mm were welded by a high-power robot laser-welding platform. The quantitative correlation between thermal cycling and the microstructure of the welded joint was studied using numerical simulation of the welding temperature field, optical microscopy (OM), and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The results show that the heat-source model of a Gaussian-distributed rotating body and the austenitization degree parameters are highly accurate in simulating the welding temperature field and characterizing the austenitization degree. The effects of austenitization are more significant than those of the cooling rate on the final microstructures of the laser-welded joint. The microstructure of the X100 pipeline steel in the HAZ is mainly composed of acicular ferrite (AF), granular bainite (GB), and bainitic ferrite (BF). However, small amounts of lath martensite (LM), upper bainite (UB), and the bulk microstructure are found in the columnar zone of the weld. The aim of this paper is to provide scientific guidance and a reference for the simulation of the temperature field during high-energy-beam laser welding and to study and formulate the laser-welding process for X100 pipeline steel.

Grain Boundary-Dependent Selection Criteria for Nucleation of Gamma-Massive Grains in TiAl-Based Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 2338-2341 ◽  
Author(s):  
A. Sankaran ◽  
Emmanuel Bouzy ◽  
Matthew R. Barnett ◽  
Alain Hazotte
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Selection Criteria ◽  
Three Dimensional ◽  
Massive Transformation ◽  
Three Dimensions ◽  
Variant Selection ◽  
Electron Backscattered Diffraction ◽  
Resolution Electron ◽  
Nucleation Mechanisms

Rapid cooling of TiAl-based alloy from α phase (disordered hexagonal, A3) generates  phase (ordered tetragonal, L1o) grains through massive transformation nucleating mostly over the α/α grain boundaries. This current work deals with the identification and the validation of different nucleation mechanisms during  massive transformation in TiAl-based alloys. Special attention has been given to the variant selection criteria for the nucleation of the massive structures along different types of α/α grain boundaries. The  massive domains formed along the grain boundaries were analysed using high resolution electron backscattered diffraction (EBSD). Statistical studies were made on different nucleation sites and different mechanisms are proposed. Two–dimensional studies of the nucleation mechanism suggest that the minimization of the interfacial energy could be the predominant criteria during the grain boundary nucleation. In order to verify this nucleation criterion in three-dimensions, serial sections were made and EBSD maps were taken and analysed in each section. The variant selection observed during the nucleation and the growth of the  massive grains is further discussed after getting a broader view under three-dimensional investigations.

scholarly journals Influence of Laser-Welding on Microstructure and Corrosion Properties of Twinning-Induced Plasticity (TWIP) Steel

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4315 ◽  
Author(s):  
Chengcheng Xu ◽  
Youkang Zhang ◽  
Wanlei Liu ◽  
Ying Jin ◽  
Lei Wen ◽  
...  
Keyword(s):  
Laser Welding ◽  
Welding Speed ◽  
Welded Joints ◽  
Twip Steel ◽  
Coincidence Site Lattice ◽  
Kelvin Probe ◽  
Electron Backscattered Diffraction ◽  
Corrosion Properties ◽  
Superior Corrosion Resistance ◽  
Mechanical Properties And Corrosion

The effect of welding speed on microstructure, mechanical properties, and corrosion properties of laser-assisted welded joints of a twinning-induced plasticity (TWIP) steel was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) analysis, electrochemical test, and micro-area scanning Kelvin probe test (SKP). The results reveal that the welded joints, with a fully austenitic structure, are obtained by laser welding. In addition, the preferred orientation of grains in fusion zone (FZ) increased with the increase of welding speed. Additionally, the coincidence site lattice (CSL) grain boundaries of FZ decreased with increasing welding speed. However, potentiodynamic polarization and SKP results demonstrated that the welding speed of 1.5 m/min renders superior corrosion resistance. It can also be inferred that the corrosion properties of the welded joints are related to the grain size and frequency of CSL grain boundary in FZ.

Microstructures and Properties of X100 Pipeline Steel Joints by Fiber Laser Welding

2017 ◽  
Vol 44 (12) ◽  
pp. 1202003
Author(s):  
郭鹏飞 Guo Pengfei ◽  
王晓南 Wang Xiaonan ◽  
朱国辉 Zhu Guohui ◽  
赵艳君 Zhao Yanjun ◽  
张敏 Zhang Min ◽  
...  
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
Pipeline Steel ◽  
Fiber Laser Welding ◽  
X100 Pipeline Steel ◽  
Steel Joints

Microstructural Evolution and Precipitation Mechanism of α-Phase in Ti-55531 Alloy Aged at High Temperature

2013 ◽  
Vol 747-748 ◽  
pp. 912-918 ◽  
Author(s):  
Xue Zhang ◽  
Yi Chen ◽  
Feng Shou Zhang ◽  
Jun Ting Yang ◽  
Yun Jin Lai ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Boundary Energy ◽  
High Energy ◽  
Ageing Temperature ◽  
Α Phase ◽  
Temperature Ageing ◽  
Annealing Heat Treatment

After two-stage annealing heat treatment process, the near β-Titanium alloys reveal a mixed microstructure containing lath-like α phase and finer acicular α phase in β matrix, leading to the improvement of strength-ductility balance. In this paper, the microstructural evolution and the behaviour of α precipitate during high temperature ageing process were investigated by SEM in a near β-Titanium alloy called Ti-55531.The relationship between α precipitates and the β grain orientation in high temperature was investigated by EBSD. The results show that the α-phase precipitated only at some places of the β grain boundaries at higher ageing temperature (~780 °C); the amount of grain boundary α increased with the decreased of the ageing temperature; after ageing at 720 °C for 45 min, we found that the α-phase precipitated not only at grain boundaries but also within the grains. It seems that the precipitation of grain boundary α is strongly influenced by β grain boundary energy which means that grain boundary α tends to form preferentially at high energy grain boundaries (high-angle grain boundaries); The α-phase precipitates more easily at the grain boundaries where the {110} plane of adjacent β grains have the same orientation.

Structure and Properties of Polycrystalline Materials From Simulation: An Interfacial Perspective

1999 ◽  
Vol 586 ◽  
Author(s):  
S. R. Phillpot ◽  
P. Keblinski ◽  
D. Wolf ◽  
F. Cleri
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Simulation Method ◽  
High Energy ◽  
Grain Boundary Diffusion ◽  
Dynamics Simulation ◽  
Polycrystalline Materials ◽  
Diffusion Creep ◽  
Fcc Metals

ABSTRACTWe have recently developed a novel molecular-dynamics simulation method to grow polycrystals from a melt containing randomly oriented crystalline seeds. The resulting microstructures contain only randomly oriented (i.e., high-energy) grain boundaries. We find that these grain boundaries, which are highly constrained by their close proximity to grain junctions, are highly disordered in fcc metals and amorphous in silicon. From simulations of infinitely extended high-energy grain boundaries in bicrystals, we find that such highly disordered and amorphous grain boundaries are actually the thermodynamic ground state; by contrast, low-energy grain boundaries are crystalline. High-energy grain boundaries in diamond, however, are structurally ordered at the expense of a significant amount of graphite-like bonding. We show that these complex grain boundary structures have important effects on properties including grain boundary diffusion (fcc metals and silicon), grain boundary diffusion creep (silicon) and grain boundary electrical activity and strength (diamond). The implications for engineering materials with prescribed properties are discussed.

Sub-grain Boundary Spacing in Directionally Crystallized Si Films Obtained via Sequential Lateral Solidification

2000 ◽  
Vol 621 ◽  
Author(s):  
M. A. Crowder ◽  
A. B. Limanov ◽  
James S. Im
Keyword(s):  
Energy Density ◽  
Grain Boundary ◽  
Film Thickness ◽  
Grain Boundaries ◽  
Directionally Solidified ◽  
Boundary Density ◽  
Straight Line ◽  
Preliminary Model ◽  
Sequential Lateral Solidification ◽  
Si Films

ABSTRACTIn this paper, we report on the average linear density of sub-grain boundaries that are found in directionally solidified microstructures obtained via sequential lateral solidification of Si thin films. Specifically, we have characterized the dependence of the sub-grain boundary density on the film thickness, incident energy density, and per-pulse translation distance. The investigation was confined to analyzing directionally solidified microstructures obtained using straight-line beamlets. It is found that the average spacing of the sub-grain boundaries depended approximately linearly on the film thickness, where it varied from 0.28m at a thickeness of 550Å to ∼0.75μm at 2,000 Å. In contrast, variations in either the energy density or the per-pulse translation distance within the investigated SLS process parameter domain were found to have a negligible effect on the spacing. Discussion is provided on a preliminary model that invokes polygonization of thermal-stress generated dislocations, and on implications of the dependence of device performance on the film thickness.

The Micro Structural Characteristic Parameters of High Grade Pipeline Steel and its Mechanical Properties

2006 ◽  
Author(s):  
Xiaoli Zhang ◽  
Chuanjing Zhuang ◽  
Lingkang Ji ◽  
Yaorong Feng ◽  
Wenzhen Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Structural Parameters ◽  
Large Angle ◽  
Lower Bainite ◽  
Granular Bainite ◽  
High Grade ◽  
Pipeline Steels

The microstructure of high grade pipeline steels, including X65, X70, X80, X100, were studied by SEM and EBSD, respectively. It was found that the microstructures of high grade pipeline steels were composed of lower bainite, granular bainite and acicular ferrite. The phases of kinds of pipeline steels were composed of Fe3C, retained austenite and ferrite. And their percentage content, grain size and its distribution were studied respectively also. These micro structural parameters were correlated to the mechanical properties of kinds of pipeline steels. Furthermore, all kinds of angles of grain boundaries were studied, and the relationship between the angles of grain boundaries and mechanical properties was obtained. It was shown that as the improving of the steel grade, the grain boundary including small angle and large angle increased. And only when grain boundary was greater than 15 degree, it was effective to the toughness behavior.

Microstructure and Mechanical Properties of Nd:YAG Laser Welded Invar 36 Alloy

2011 ◽  
Vol 675-677 ◽  
pp. 739-742 ◽  
Author(s):  
Yue Zhao ◽  
Ai Ping Wu ◽  
Wei Yao ◽  
Zhi Min Wang ◽  
Yutaka S. Sato ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Nd:Yag Laser ◽  
Arc Welding ◽  
Welding Process ◽  
High Energy ◽  
High Susceptibility ◽  
Energy Beam ◽  
Microstructure And Mechanical Properties ◽  
And Storage

Invar 36 alloy is increasingly used as a structural material for manufacture of liquefied natural gas (LNG) transporters and storage tanks. However, the conventional arc welding of Invar 36 alloy has high susceptibility of hot-cracking. As a high-energy-beam welding process, laser welding could be effective for producing defect-free Invar 36 weld. In the present study, defect-free Invar 36 weld was successfully produced by Nd:YAG laser welding. The microstructure and mechanical properties of weld were also tested.

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