In laser welding processes, power is a critical parameter. The power directly influences the energy density of the laser beam in the welding zone, thereby affecting the formation, quality, and efficiency of the weld seam. Here are some key factors and considerations regarding power selection:
Energy Density and Penetration Depth: Welding power determines the energy density of the laser within the weld area, which is the distribution of laser energy per unit area. Higher power levels typically result in higher energy densities, leading to deeper weld penetration.
Control of the Weld Pool: Proper selection of power levels helps control the formation and stability of the weld pool in the welding zone. Insufficient power may result in an inadequate or unstable weld pool, while excessive power can lead to excessive penetration or a larger heat-affected zone.
Speed and Weld Quality: Power is closely related to welding speed. Optimal power allows for higher welding speeds while maintaining good weld quality. Insufficient power may require lower welding speeds to ensure weld quality, while excessive power may restrict welding speed or cause welding defects.
Material Selection: Different materials require different welding powers. Material properties such as reflectivity, thermal conductivity, and melting point influence the choice of power.
Equipment Capability: Ensure that the selected power falls within the rated operating range of the welding equipment to avoid issues such as equipment overload or reduced efficiency.
In practical applications, selecting the appropriate welding power involves considering these factors comprehensively. Experimentation and adjustments are often necessary to optimize welding parameters and achieve the desired welding quality and efficiency.
In laser welding, energy input is typically described using two parameters: energy density (laser power divided by spot area, expressed in W/cm²) and heat input (laser power divided by welding speed, expressed in J/cm).
Energy density refers to the intensity of laser energy within a spatial area, indicating how concentrated the laser energy is on the workpiece surface. It is calculated by dividing the laser power by the area of the laser spot on the material.
Heat input, on the other hand, describes the cumulative amount of laser energy delivered over time. It is calculated by dividing the laser power by the welding speed, providing a measure of how much energy is inputted per unit length of the weld seam.
These parameters are crucial for optimizing laser welding processes, as they directly affect weld penetration depth, heat affected zone size, and overall weld quality. Adjusting energy density and heat input allows welders to control the process to achieve desired outcomes such as strong joints and minimal distortion.
In industrial applications, waveform editing directly programs the settings for energy, but there's a consideration of energy losses between the set energy, the detected energy at emission, and the final power output from the welding head. It's important to focus on energy rather than power in this context. Different welding scenarios require different waveform power settings, but energy is relatively accurate and provides valuable comparisons. Accumulating melting energy for different materials facilitates rapid process window design for new products, quickly pinpointing suitable parameters.
The relationship between simple power and weld penetration and width is generally as depicted in the diagram: higher power typically increases both weld penetration and width. Laser welding features an energy node where below it is conduction welding, and above it is deep penetration welding. The distinction lies in deep penetration welding, which involves keyhole formation, a topic we will explore further.
Common defects caused by insufficient power include: incomplete fusion, shallow penetration, and unclear weld imprints. On the other hand, defects associated with excessive power include: burn-through, excessive spatter, wavy edges, and undercutting.
