Metal vaporization from weld pools

Block-Bolten, A.; Eagar, T. W.

doi:10.1007/bf02657376

Cited by 138 publications

(49 citation statements)

References 2 publications

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“…The factor 7.5 is used to account for the diminished evaporation rate at one atmosphere pressure compared to the vaporization rate in vacuum and is based on previous experimental results. [46,47] APPENDIX II Recoil pressure exerted by the metal vapors can be given by the difference between the momentum of the vapors leaving the surface and the z-direction momentum of the liquid near the liquid-vapor interface.…”

Section: Appendix Imentioning

confidence: 99%

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A Convective Heat-Transfer Model for Partial and Full Penetration Keyhole Mode Laser Welding of a Structural Steel

Naresh

Kelly

Martukanitz

et al. 2007

Metall Mater Trans A

103

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In the keyhole mode laser welding of many important engineering alloys such as structural steels, convective heat transport in the weld pool significantly affects temperature fields, cooling rates, and solidification characteristics of welds. Here we present a comprehensive model for understanding these important weld parameters by combining an efficient keyhole model with convective three-dimensional (3-D) heat-transfer calculations in the weld pool for both partial and full penetration laser welds. A modified turbulence model based on PrandtlÕs mixing length hypotheses is included to account for the enhanced heat and mass transfer due to turbulence in the weld pool by calculating spatially variable effective values of viscosity and thermal conductivity. The model has been applied to understand experimental results of both partial and full penetration welds of A131 structural steel for a wide range of welding speeds and input laser powers. The experimentally determined shapes of the partial and full penetration keyhole mode laser welds, the temperature profiles, and the solidification profiles are examined using computed results from the model. Convective heat transfer was the main mechanism of heat transfer in the weld pool and affected the weld pool geometry for A131 steel. Calculation of solidification parameters at the trailing edge of the weld pool showed nonplanar solidification with a tendency to become more dendritic with increase in laser power. Free surface calculation showed formation of a hump at the bottom surface of the full penetration weld. The weld microstructure becomes coarser as the heat input per unit length is increased, by either increasing laser power or decreasing welding velocity.

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Section: Appendix Imentioning

confidence: 99%

“…where n is the total number of alloying elements in the alloy, DH i is the heat of evaporation of element i, and J i is the evaporation flux of element i given by the modified Langmuir equation: [46][47][48] J i ¼ a i P 0…”

Section: Appendix Imentioning

confidence: 99%

A Convective Heat-Transfer Model for Partial and Full Penetration Keyhole Mode Laser Welding of a Structural Steel

Naresh

Kelly

Martukanitz

et al. 2007

Metall Mater Trans A

103

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“…A constant electrical potential is specified along the anode surface BC because the anode is assumed to be a perfect conductor relative to the plasma. Experimental data of Bloch-Bolten and Eagar [20] and Cieslak et al [21] showed that the maximum surface temperature for steel weld pool is approximately 500 K below the boiling temperature. In this study, therefore, we set a constant temperature of 2200 K at the cathode surface as suggested by Tanaka and Lowke [26].…”

Section: Boundary Conditionsmentioning

confidence: 98%

“…Therefore, the domain for V is chosen as the smaller area ABCD, since the exact boundary condition for V along the line FA is unknown. [20,21,26] 1000 K [22] 1000 K [2,6,17] 3000 K [2,6,17] Due to symmetry, only a half of the flow domain was considered for the calculation. Along the centreline AB, symmetry conditions are used, zero velocities are specified along the solid boundaries BC and FA.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Theoretical model and experimental investigation of current density boundary condition for welding arc study

Boutaghane

Bouhadef

Valensi

et al. 2011

Eur. Phys. J. Appl. Phys.

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Abstract. This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~ 21000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/sec) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5×10 7 A.m -2 for a 1.2 mm diameter welding electrode. IntroductionIn arc welding, an electric arc is burning between a "workpiece" and an auxiliary electrode: -For gas metal arc welding (GMAW) process the auxiliary electrode is welding wire, which is usually the anode (reverse polarity). Heat transfer from the arc and Ohm's heating in the wire melt its tip forming droplets, transferred through the arc to the workpiece used as a cathode. -For gas tungsten arc welding (GTAW) process, the workpiece, which is usually the anode (straight polarity), locally melts due to heat transfer from the arc, forming a weld pool. Thermal behaviour of welding arcs and their electrodes can have significant effects on the subsequent weld quality and production rate. Hence, it is desirable to have a theoretical method which can predict the properties of both electrodes and arc plasma as functions of the arc operating conditions. The behaviour of an arc is governed by a coupled set of physical laws, i.e., Ohm's Law, Maxwell's equations and conservation equations of mass, momentum, energy and electrical charge [1,2]. The modelling of arc welding processes has been reported by a number of researchers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Most early numerical models have treated either only the arc plasma [2][3][4][5][6][7] or only the weld pool [8][9][10][11][12][13][14]. For the arc plasma, a plane surface of the solid anode has been set to be a bottom boundary for the electric potential and temperature which are given as the boundary conditions. The tungsten cathode has been assumed to be a...

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“…To realize a quantitative estimation of the weld metal composition, while varying the irradiation parameters, a comprehensive model is required. Several authors have used Longmuir equation for the calculation of the changes in weld metal composition due to various welding processes [1,2].The equation is useful for calculation of relative vaporization rates from different alloying elements in vacuum and it results to a higher absolute rate than actual values [2][3][4][5]. Mundra and T.Debroy [2] derived equations for the vaporization rate of various alloying elements in conduction mode laser welding of high-manganese stainless steel with a CW 2 CO laser.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Composition Change in Pulsed Nd:YAG Laser Welding

Torkamany¹,

Parvin²,

Jandaghi³

et al. 2010

Laser Welding

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Abstract:A numerical model based on the kinetic theory of gases and the thermodynamic laws is developed for keyhole formation in pulsed laser welding. For a single incoming pulse the spatial profile of the created keyhole was simulated as a function of time using this model. Since undesirable loss of the volatile elements affects on the weld metal composition and properties we have focused in our model to find the process conditions that minimum of these losses take place during pulsed laser welding. The major laser welding process parameters including pulse properties have been examined formerly in this model. The power density and pulse duration were the main investigated variables. The model predicts that loss of alloying elements increase at higher peak powers and longer pulse durations. The model was used for two different kinds of metals, one from the ferrous compoundsStainless Steel 316-and the other an aluminum alloy-5754 Aluminum alloy-. By running the model for SS316 it was found that concentrations of the Fe base and Nickel were increased in the weld metal region while concentrations of the chromium and manganese were decreased. Pulsed laser welding of stainless steel 316 in keyhole mode was experimentally studied too. The welding work piece was 2 mm thick SS316 sheet metal. After welding experiments, samples were cut and weld cross sections were analyzed. The concentrations of iron, chromium, nickel and manganese were determined in the weld pool by means of the Proton-Induced X-ray Emission (PIXE) and Energy Dispersive X-ray/Wavelength Dispersive X-ray (EDX/WDX) analysis. It was shown that the composition alteration, predicted by the model due to varying of the laser parameters is in well accordance to the corresponding experimental data. Al5754 was the second material used for laser welding experiments. Weld metal composition change of this alloy in keyhole mode welding, using a long pulsed Nd:YAG laser was investigated by use of the developed numerical model and supported with experimental measurements. During laser welding process, the significant variables were laser pulse duration and power density. It was predicted in the model and concurred experimentally that, the concentration of magnesium in the weld metal decreases by increasing the laser pulse duration, while the aluminum concentration increases. Moreover, the concentrations of aluminum and magnesium elements, in the weld metal were 9 www.intechopen.com Laser Welding 194determined by laser induced breakdown spectroscopy (LIBS) for different welding conditions.

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Metal vaporization from weld pools

Cited by 138 publications

References 2 publications

A Convective Heat-Transfer Model for Partial and Full Penetration Keyhole Mode Laser Welding of a Structural Steel

A Convective Heat-Transfer Model for Partial and Full Penetration Keyhole Mode Laser Welding of a Structural Steel

Theoretical model and experimental investigation of current density boundary condition for welding arc study

Estimation of Composition Change in Pulsed Nd:YAG Laser Welding

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