What is Laser Welding Process?

 

The impact of manufacturing activities on the global environment is becoming noteworthy, and effective waste reduction and energy conservation technologies are urgently needed in manufacturing processes to achieve sustainable development. The majority of manufacturing processes involve welding processes ranging from traditional to recent manufacturing technologies.

Nowadays, laser welding is the most popular method in the manufacturing industry, and it is used on a wide range of materials and products. Laser welding is the most advanced process. Very low heat input to the weld, low distortion and the ability to weld heat-sensitive components are the advantages of laser welding. The selection of input parameters is critical for obtaining good weld bead geometry.

Laser Beam Welding

The joining technique is one of the vital manufacturing techniques that may be utilized to enhance product design and reduce production costs. Laser beam welding uses gas tungsten arc welding (GTAW). Welding is the process the accurate, reliable, and economical process of joining the two work-pieces together. Also, it has below  characterizations,

Excellent quality

High performance

High precision

High speed

Good flexibility

Minimal distortion

The power density of the laser beam is shown below,

There are many principal characteristics related to the laser beam welding process (LBW),

Characteristic	Note
The high density of energy	Minimum distortion
Speedy processing	Economical (if fully utilized)
Sudden start/stop	Because this process is operated by a CNC programme
Atmospheric pressure welds	Compared to arc procedures and electron beam welding
No X-rays are produced	Versus welding with an electron beam
No need for filling (Autogenous weld)	Failing to remove the flow
Confined weld	Minimal distortion
Zone with very little Heat Affected	Weld is performed near heat-sensitive materials
It is possible to weld quite precisely	Weld can be done from low to high workpiece
Excellent weld bead profile	There is no need to clean up
In a magnetic field, a beam cannot stray	As opposed to electron beam welding
Without contamination	Relying on gas obscuration
Rarely can difficult materials be welded	General benefit

Laser Welding Types

CO2 Laser

The process has little heat input and excessive density of energy which is generated using the continuous wave of CO2. This type of laser welding produces a tiny heat-affected zone (HAZ), which cools more speedily with less disfigurement and has a high depth/width ratio for the fusion area.

The primary outcome of the procedure is the CO2 laser strengthens the plume of the welding above the joint by diffusing the power density of the beam, reducing the weld depth and enhancing the weld joint’s surface breadth. Traditionally, CO2 lasers have been used for applications related to automobiles.

There are a number of benefits, 

Quick
Repeatable
Long weld with high-quality
Straight seams
Can weld axisymmetric components

Neodymium yttrium aluminium garnet (Nd:YAG) Laser

The solid-state laser crystal known as neodymium-doped yttrium aluminium garnet, or Nd: YAG, is extensively employed in a variety of applications. This laser gets its name from the dopant (neodymium) and the host crystal (YAG). Recent developments in Nd: YAG laser technology have made it possible to transmit beam energies of at least 2 kW across fibre optic cables. Particularly beneficial for robotic operations where the laser beam must be manipulated around a stationary part.

Nd: YAG laser beam welding is a high energy density and low heat input process that causes a small heat-affected zone (HAZ), which has a high ratio between depth and width for the fusion zone and cools more quickly with minimum distortion.

Fibre Laser Welding

The fibre laser welding process is a modern efficient, versatile and precise method to use to join material together. Fibre laser welding produces a smaller heat-affected zone, therefore, fibre laser welding can reduce the risk of distortion and damage to the surrounding material. This process has a few benefits, such as

High weld quality

Non-contact welding process

Automation capability

Low maintenance

Diode Lasers

Diode lasers have a wavelength that is near to the spectrum of infrared. As an example, it is about 808 nm. On the other hand, the relevant equipment size is quite compact. It is about a box of shoes for laser heads with kW capacities. Diode lasers have a significant advantage over traditional CO2 and Nd: YAG lasers in terms of weight and compact size; in addition to that, diode lasers are mounted to equipment with robot to move easily. Less cooling and higher life are the most important parameters.

Weld defects

Weld pool pores

This happens due to falling down the keyhole quickly. preventing molten metal from flowing into the centre of the keyhole before solidification. They are most common at the weld's root. In some Al alloys, macro-porosity (holes greater than 0.2 mm in diameter) is mostly caused by keyhole formation instability. This weld defect increases when increasing the power density and duration between pulses while performing the weld.

Undercutting

Undercutting is a major defect and it happens when the weld edge is below the weld center. The difference between the maximum and minimum points of the weld surface is considered the undercutting. Undercutting may occur irregularly while increasing the speed of the weld using the pulsed laser.

Humping

This is a longitudinal weld defect and can be identified as Consistent bumping and limitation of the face of the weld. The metal from the weld develops humps above the workpiece's surface. This defect may occur at high velocities and the weld pool shape is important in the formation of the lift of the weld.

Blow-holes

Keyhole instabilities can cause blow-holes to emerge in the top weld bead, most at very high welding speeds.

Cracks

Welding cracks can be seen in the top part of the weld and it forms primarily.

Non-uniformity and surface roughness

The surface roughness of the weld surface depends on the speed of welding, power of the laser beam, duration of pulse, and average peak power density. The optimum speed of the weld helps to obtain the lowest roughness on the surface. Furthermore, roughness rises dramatically while having the very low power of the laser beam.

Limitation of Laser Welding Process

Only applicable to metals and alloys

Less effective on highly reflective materials

Commonly used for materials with moderate thickness

Gaps or misalignment affect negatively weld quality

Cost is high

Require regular maintenance

Need skill operators

safety concerns

Application of Laser Welding Process

Automotive Industry for body, chassis, exhaust system, powertrain components weld

Aerospace Industry for turbine blades and aircraft components weld

Laser diode assembly

surgical instruments and implantable devices manufacturing

Jewelry manufacturing

shipbuilding

consumer electronic manufacturing

Load cell manufacturing process