A study of laser welding modes with varying beam energy levels

Abstract

The energy of a laser beam is generally calculated based on the laser power and its processing speed. In this work, the laser welding modes such as conduction, conduction—penetration, and keyhole welding of thickness 1.6, 2, and 2.5 mm AISI304 stainless steel sheets, respectively, are studied at different beam energy levels. A series of bead-on-plate trials are conducted using a 500 W continuous wave Nd:YAG laser source to study the beam—material interaction and the influence of laser power and welding speed on the formation of weld pool. In addition to the experimental study, a three-dimensional finite-element model is developed to analyse the transient heat flow and to predict the formation of the weld pool. The correlation among the parameters including laser power, welding speed, beam incident angle, and the characteristic geometry of weld pool are established. Temperature-dependent thermal properties of AISI304 stainless steel, the effect of latent heat of fusion, and the convective and radiative aspects of boundary conditions are considered in the model. The heat input to the developed model is assumed to be a three-dimensional conical Gaussian heat source. Finite-element simulations are carried out by using finite-element code, SYSWELD, and FORTRAN subroutines available within the code are used to obtain the numerical results. The result of the numerical analysis provides the shape of the molten pool with different beam energy levels, which is then compared with the results obtained through experimentation. It is observed that the results obtained from finite-element simulation and the experimental trials are in good agreement.

Interaction time and beam diameter effects on the conduction mode limit

“…The unstable mode welding had been previously identified by Chen [13] and Zhang [14] and it was attributed to thermal focusing [15,16] , to an incorrect selection of welding parameters or to welding mode fluctuation. More studies have shown the presence of a regime between conduction mode and keyhole mode [1,[17][18][19][20], while other studies just take into account two welding modes [21,22] . The transition between conduction mode and keyhole mode is somewhat unclear, not only in terms of which and how the different process parameters will influence this transition but also related to the presence or not of a transition mode.…”

Conduction laser welding

“…6.9). 23 Sibillano et al also identified a mixed mode in laser welding. The authors defined this regime as having properties of both conduction and keyhole.…”

“…At a welding speed of 1,000 mm/min, it was concluded that the transition from conduction to keyhole mode took place with 400 W of laser power. 23 In this work, despite concluding that there was a range of power densities where conduction mode takes place, no relation between the parameters and the welding mode was made and just a set of parameters was given as an example of where conduction would transit to keyhole mode.…”

Controlled Crystallographic Texture Orientation in Structural Materials Using the Laser Powder Bed Fusion Process—A Review

“…[24] This threshold or region is referred to as the transition region. [25,26] At this threshold, the induced recoil pressure is inadequate to overcome the surface tension on the molten pool, leading to insufficient penetration. Most of the applied laser energy in the transition mode or region, therefore, goes into increasing vaporization rates till a deep penetration (keyhole) forms.…”