With the popularity of handheld laser welding machines in the industrial field, people want to know 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 by 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 the specific introduction of these two laser welding modes.

The heat of heat conduction welding diffuses to the inside of the workpiece through heat transfer, and the workpiece is melted to form a specific molten pool by controlling the laser parameters such as the width, energy, peak power and repetition frequency of the laser pulse. This laser welding mode only produces melting on the surface of the weld, and the inside of the workpiece is not completely penetrated, and basically does not produce vaporization. After welding, the depth of penetration is shallow and the welding speed is slow. It is mostly used for welding low-speed thin-walled metal materials.

Laser deep penetration welding not only completely penetrates the material, but also vaporizes the material to form a large amount of plasma. Due to the high heat, a keyhole phenomenon will appear at the front end of the molten pool. Deep penetration welding can thoroughly penetrate the workpiece, and has the characteristics of large input energy, fast welding speed, and large depth-to-width ratio. It is currently the most widely used laser welding mode. The laser welding machine used for gear welding and metallurgical thin plate welding mainly involves laser deep penetration welding.

 

Different process parameters have different effects on the effect of laser welding. Here are three factors that affect the effect of laser welding.

There is a threshold value of laser energy density in laser welding. Below this value, the penetration depth is very shallow. Once this value is reached or exceeded, the penetration depth will be greatly increased. Plasma is generated only when the laser power density on the workpiece exceeds a threshold value (depending on the material), which marks the progress of stable deep penetration welding.

If the laser power is below this threshold, only surface melting of the workpiece occurs, i.e. welding takes place with stable heat conduction. When the laser power density is near the critical condition for the formation of small holes, deep penetration welding and conduction welding are performed alternately, which becomes an unstable welding process, resulting in large fluctuations in penetration depth. During laser deep penetration welding, the laser power controls the penetration depth and welding speed at the same time. In general, for a laser beam of a certain diameter, the depth of penetration increases as the beam power increases.

The welding speed has a great influence on the penetration depth. Increasing the welding speed will make the penetration shallower, but if the speed is too low, it will cause excessive melting of the material and welding through the workpiece. Therefore, there should be a suitable welding speed range for a specific material with a certain laser power and a certain thickness, and the maximum penetration depth can be obtained at the corresponding speed value.

The laser welding process often uses inert gas to protect the molten pool. When some welding materials can be ignored when the surface oxidation is not considered, but for most applications, helium, argon, nitrogen and other gases are often used as protection to make the workpiece Protected from oxidation during soldering.

Helium gas is not easy to ionize, which allows the laser to pass through smoothly, and the beam energy reaches the surface of the workpiece without hindrance. This is the most effective shielding gas used in laser welding, but it is more expensive. Argon gas is cheaper and denser, so the protection effect is better. However, it is susceptible to high-temperature metal plasma ionization, which shields part of the beam from hitting the workpiece, reduces the effective laser power for welding, and also damages the welding speed and penetration. Nitrogen is the cheapest shielding gas, but it is not suitable for welding some types of stainless steel. This is mainly due to metallurgical aspects such as absorption, which sometimes creates porosity in the overlapping areas.

The second function of using shielding gas is to protect the focusing lens in the laser welding gun from metal vapor contamination and sputtering of liquid droplets. Especially in high-power laser welding, because the ejection becomes very powerful, it is more necessary to protect the lens at this time. The third function of the shielding gas is that it is very effective in dissipating the plasma shield produced by high-power laser welding.

 

From the above information, we can know that setting the laser welding parameters correctly can obtain better welding quality of the workpiece. Follow ACCTEK LASER to learn more about laser welding system.