Asymmetry in steel welds with dissimilar amounts of sulfur

Wei, Huiliang; Pal, Snehanshu; Manvatkar, V.; Lienert, Thomas J.; DebRoy, T.

doi:10.1016/j.scriptamat.2015.06.024

Cited by 21 publications

(6 citation statements)

References 11 publications

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“…q is the heat input from the laser beam with a Gaussian distribution, calculated using where Q is the energy power, a is the energy absorption rate, r is the radius of the laser beam, x 0 , y 0 is the initial position of the laser spot center, and u is the scanning speed of the laser beam along the positive direction of the X-axis. The main driving forces in the model include surface tension �� ⃗ F s , Marangoni stress �� ⃗ F m , recoil pressure �� ⃗ F r , damping term in the mushy zone �� ⃗ F a [47,49], and gravity �� ⃗ F g .…”

Section: Governing Equationsmentioning

confidence: 99%

In Situ Elimination of Pores During Laser Powder Bed Fusion of Ti–6.5Al–3.5Mo–l.5Zr–0.3Si Titanium Alloy

Zhang

Liao

Liu

et al. 2021

Acta Metall. Sin. (Engl. Lett.)

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The printing quality of components manufactured using laser powder bed fusion (LPBF) generally depends on the presence of various defects such as massive porosity. Thus, the efficient elimination of pores is an important factor in the production of a sound LPBF product. In this study, the efficacy of two in situ laser remelting approaches to eliminating pores during the LPBF of a titanium alloy Ti-6.5Al-3.5Mo-l.5Zr-0.3Si (TC11) was assessed both experimentally and computationally. These two remelting methods are surface remelting and layer-by-layer printing and remelting. A multi-track multi-layer phenomenological model was established to analyze the variation of pores with the temperature and velocity fields. The results showed that surface remelting with a high laser power, such as 180 W, can effectively eliminate pores within three deposited layers. However, such remelting could not reach defects in deeper regions. Layer-by-layer remelting with a 180 W laser could effectively eliminate the pores formed in the previous layer in real time. The results obtained in this study can provide useful guidance for the in situ control of printing defects supported by real-time monitoring, feedback, and operating systems of an intelligent LPBF equipment.

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Section: Governing Equationsmentioning

confidence: 99%

In Situ Elimination of Pores During Laser Powder Bed Fusion of Ti–6.5Al–3.5Mo–l.5Zr–0.3Si Titanium Alloy

Zhang

Liao

Liu

et al. 2021

Acta Metall. Sin. (Engl. Lett.)

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“…The flow of fluid in the molten pool is the main reason for the formation of various shapes of parts. The fluid in the molten pool mainly flows backward and sideways [24] . Due to the effect of Marangoni convection and surface tension on the fluid in the molten pool, the height difference between the head and tail of the deposition track gradually increases with the increase of layers [19,25] .…”

Section: Deposition Process Of Dedmentioning

confidence: 99%

Transient printing characteristics with wavy build profiles for laser additive manufacturing of small size structures

Fu-qin

Wei

et al. 2021

China Foundry

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Laser directed energy deposition (DED) is a multi-physics process that accompanies mass flow, energy transfer, and complex phase transitions. The printing characteristics of small size parts are significantly affected by the progressive variations of the temperature fields and the fluid flow within the molten pool. In this work, the deposition characteristics during multi-layer and multi-track laser DED were explored through a well-tested phenomenological model and corresponding experimental results. The variations of the build profiles and the decoupled track and layer profiles were systematically examined. Moreover, the printing characteristics of the builds with different scanning lengths were compared. Results showed that the multi-layer and multi-track transient deposition processes generated a significantly wavy surface profile. Compared with the long scanning length part, the beginning region of the short build produced an obvious bulge followed by sharply decreased height along the scanning direction. The transverse section of the short build varied significantly at different positions. Two adjacent columns of tracks were extracted from the overall build, demonstrating that the tracks tilted outwards and the angle increases along the scanning direction. The 3D numerical model was validated with corresponding experiments for builds with various layers. The scientific findings from this work can provide useful insights for the understanding of the additive mechanisms during laser DED for the precise shape control of small size parts.

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“…Lienert et al [ 26 ] observed a significant centerline shift in the molten pool during Gas Tungsten Arc (GTA) welding when two stainless steels with greatly different sulfur contents were welded, and they suggested that sulfur-influenced Marangoni convection was one of the reasons. Based on this, Wei et al [ 27 ] analyzed the offset of maximum molten depth and rotation of the molten pool shape, and they concluded that the spatial gradient of temperature and sulfur caused the centerline shift and the rotation of the molten pool. Bahrami et al [ 28 ] studied sulfur-induced driving forces at the free surface in GTA spot welding of 1018 steel and nickel 200, and they indicated that the driving forces induced by the concentration gradient of sulfur mainly affected Marangoni convection when the molten pool was just formed.…”

Section: Introductionmentioning

confidence: 99%

Role of Surface-Active Element Sulfur on Thermal Behavior, Driving Forces, Fluid Flow and Solute Dilution in Laser Linear Welding of Dissimilar Metals

Shu

Dong

et al. 2023

Materials

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Understanding heat and mass transfer and fluid flow in the molten pool is very helpful in the selection and optimization of processing parameters, and the surface-active element has an important effect on the heat and mass transfer in laser welding of dissimilar metals. A three-dimensional (3D) numerical model coupled with a sub-model of surface tension, which considers the influence of local temperature and the concentration of surface-active element sulfur at the gas/liquid surface, is used to analyze the thermal behavior, driving forces, fluid flow, and solute dilution during laser linear welding of 304SS and Ni. The relationship between surface tension, driving forces, and the temperature coefficient of surface tension with the spatial distribution of temperature and the surface-active element sulfur is quantitatively analyzed. The simulation results show that the molten pool is fully developed at 45 ms, and the collision of inward and outward convection, with the maximum velocity reaching 1.7 m/s, occurs at the isotherm with a temperature between 2200 K and 2500 K. The temperature-gradient term and concentration-gradient term of surface shear stress play different roles in different positions of the free surface. The local sulfur concentration changes the temperature sensitivity of the surface tension at different sides of the free surface and further determines the transition of convection. Complex fluid flow promotes solute dilution, and the distribution of solute becomes uniform from the front to the rear of the molten pool. The Ni element is transferred to 304SS mainly at the rear side. The work provides theoretical support for the control of joint quality by changing the content of surface-active elements in dissimilar welding.

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Asymmetry in steel welds with dissimilar amounts of sulfur

Cited by 21 publications

References 11 publications

In Situ Elimination of Pores During Laser Powder Bed Fusion of Ti–6.5Al–3.5Mo–l.5Zr–0.3Si Titanium Alloy

In Situ Elimination of Pores During Laser Powder Bed Fusion of Ti–6.5Al–3.5Mo–l.5Zr–0.3Si Titanium Alloy

Transient printing characteristics with wavy build profiles for laser additive manufacturing of small size structures

Role of Surface-Active Element Sulfur on Thermal Behavior, Driving Forces, Fluid Flow and Solute Dilution in Laser Linear Welding of Dissimilar Metals

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