Guide you to understand handheld laser welding technology

With the popularity of handheld laser welding machines in the industrial field, people want to learn more about laser welding. This article introduces two different laser welding modes and the factors that affect the laser welding effect.
laser welding can be achieved through continuous or pulsed laser beams. According to the principle of laser welding, it can be divided into heat conduction welding and laser deep penetration welding. The following is a specific introduction to these two laser welding modes.



Heat conduction welding
The heat of thermal conduction welding diffuses into the interior of the workpiece through heat transfer, and by controlling laser parameters such as pulse width, energy, peak power, and repetition frequency, the workpiece is melted to form a specific molten pool. This laser welding method only produces melting on the surface of the weld seam, without complete penetration inside the workpiece, and basically does not produce vaporization. After welding, the penetration depth is shallow and the welding speed is slow. It is mainly used for welding low-speed thin-walled metal materials.

Laser deep penetration welding
Laser deep penetration welding can not only completely penetrate the material, but also vaporize the material to form a large amount of plasma. Due to high temperature, keyhole phenomenon may occur at the front end of the melt pool. Deep penetration welding can completely penetrate the workpiece and has the characteristics of high input energy, fast welding speed, and large aspect ratio. It is currently the most widely used laser welding mode. laser welding machines used for gear welding and metallurgical sheet welding mainly involve laser deep penetration welding.

 
The influence of different process parameters on the laser welding effect varies. Here are three factors that affect the effectiveness of laser welding.

Laser power 
There is a threshold for laser energy density in laser welding. Below this value, the penetration depth is very shallow. Once the value is reached or exceeded, the penetration depth will greatly increase. Plasma is only generated when the laser power density on the workpiece exceeds a threshold (depending on the material), marking the progress of stable deep penetration welding.
If the laser power is below this threshold, only surface melting of the workpiece occurs, that is, welding is carried out under stable heat conduction. When the laser power density approaches the critical condition for forming small holes, alternating between deep penetration welding and conduction welding becomes an unstable welding process, resulting in significant fluctuations in penetration depth. During laser deep penetration welding, the laser power controls both the penetration depth and welding speed simultaneously. Generally speaking, for a laser beam of a certain diameter, the penetration depth increases with the increase of beam power.

Welding speed 
The welding speed has a significant impact on the depth of penetration. Increasing the welding speed will make the depth of fusion shallower, but if the speed is too low, it will cause the material to melt excessively and weld through the workpiece. Therefore, for specific materials with a certain laser power and thickness, there should be a suitable welding speed range that can achieve maximum penetration at the corresponding speed values.


 
Protective gas
The laser welding process usually uses inert gas to protect the molten pool. When some welding materials can ignore surface oxidation, for most applications, helium, argon, nitrogen, and other gases are typically used as protection to prevent oxidation of the workpiece during the welding process.
The second function of using protective gas is to protect the focusing lens in the laser welding gun from metal vapor contamination and droplet splashing. Especially in high-power laser welding, as the spray becomes very powerful, lens protection is even more necessary at this time. The third function of protective gas is that it is very effective in dissipating the plasma shielding generated by high-power laser welding.