Physical Characteristics of Coupled Plasma and Its Influence on Weld Formation in Hybrid Laser-Double-Arc Welding

et al. 2020

Materials

In this paper, a matrix equation for the welding heat source model was proposed to calculate the fillet welds temperature distribution based on the penetration depth and molten width. A double ellipsoid heat source model of fillet weld was established firstly by physical experiment and simulation calculation, and then the orthogonal experiment was constructed based on the previous calculation methods and experimentally measured data. Finally, the matrix equation of the heat source model parameters was obtained by regression analysis based on the joint penetration and width. The experimental and numerical simulation of the temperature distribution had been performed for the fillet weld and the results show that (1) the heat flux increases in one direction, while, oppositely, it decreased in another direction; (2) simulation results were highly in accordance with experiments results. The results indicated that the double ellipsoidal heat source model calculated by the matrix equation is quite appropriate for predicting the transient temperature distribution on the fillet welds for the gas metal arc welding process.Materials 2020, 13, 1222 2 of 11 for calculating residual stress, deformation, and solidification [16,17]. First of all, the premise of obtaining an accurate temperature field was to formulate a heat source model that was consistent with the actual situation. A welding heat source model was established by Rosenthal's application of Fourier's law (that is, point, line, and surface heat sources), which could reasonably calculate the transient temperature distribution at a certain distance from the heat source. Rosenthal's analysis, however, is less accurate for the temperature in or near the fusion and heat-affected zones because the scheme defined that the physical properties of the material did not change with temperature. To overcome most of these limitations, other forms of heat source models have been proposed. It was worth mentioning that the double ellipsoid heat source model was proposed by Goldak, which could well describe the arc welding heat source model [18].Due to the development of computers, welding numerical simulations has made great progress [19]. A 3-D heat transfer model has been established by Kim et al., in which the temperature, weld pool shape, and the weld pool reinforcement surface during gas-metal arc fillet welding were analyzed. In the establishment of this model, not only the heat transfer from the welding arc was considered, but also the thermal effect of metal droplets was considered by the volume heat source [20]. By summarizing the calculation of the temperature field of the predecessors, the transient temperature analytical equation of the semi-infinite body under the three-dimensional motion heat source was obtained by Fachinotti et al. [21]. Winczek applied the bimodal heat source model to establish a temperature field analytical model, which could well analyze the temperature of the multi-pass GMAW in the infinite body model [22].Some scholars have proposed some methods...

Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Experimental Research on Temperature Distribution of Fillet Welds

Zuo

et al. 2020

Materials

“…The efficiency and quality requirements for welding in the installation of large-diameter, thick-walled pipes in harsh environments and over long distances will become more stringent. Therefore, many advanced welding methods are used for welding high-grade pipeline steel in recent years, such as laser welding [4], laser-arc hybrid welding [5,6], friction stir welding [7], and more. Laser welding has good application prospects due to its advantages such as fast welding speed, large penetration depth, and small deformation, and has been reported in many welding fields.…”

Section: Introductionmentioning

confidence: 99%

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

Wang²,

Yin

et al. 2019

Materials

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.

An Investigation of the Laser Welding Process for Dual-Phase Steel via Regression Analysis

Zhao

Ivanov

IOP Conf. Ser.: Mater. Sci. Eng.

2020

In this work, a systematic investigation was undertaken to explore the effects of welding process parameters on the mechanical performances of the welding joints in the laser welding process for DP600. Welding experiments were arranged by a uniform experimental design method with four control factors (laser power, welding speed, focal point position, and side-blowing shield gas flow). The tensile strength of the welding joints was used to quantify the welding quality. A mathematical model based on stepwise regression analysis was employed to correlate the welding process parameters and the tensile strength. The effects of the welding process parameters on the welding quality were discussed. The genetic algorithm was then employed to select the optimum welding parameters. The verification test results proved that the method proposed in this paper could effectively evaluate and optimize the welding quality within the range of process parameters, which could enhance the welding performance in the laser welding process as feasibly and effectively as possible.