Laser welding introduction of metal welding processing method

Laser welding introduction of metal welding processing method

One of the metal welding processing methods is laser welding. Laser welding can be realized by continuous laser beam or pulsed laser beam. The principle of laser welding can be divided into heat conduction welding and laser deep penetration welding. When the power density is less than 104~105W/cm2, it is heat conduction welding. At this time, the penetration is deep and the welding speed is slow; when the power density is greater than 105~107W/cm2, the metal surface is concaved into "holes" under the action of heat, forming deep penetration welding , with the characteristics of fast welding speed and large aspect ratio.

Laser deep penetration welding generally uses a continuous laser beam to complete the connection of materials. The metallurgical physical process of laser deep penetration welding is similar to that of electron beam welding, that is, the energy conversion mechanism is completed through the "keyhole" structure.

Under laser irradiation with a sufficiently high power density, the material evaporates and forms pores. This small, steam-filled hole acts like a black body, absorbing almost all the energy of the incoming beam. The equilibrium temperature in the cavity is about 2500°C, and the heat is transferred from the outer wall of the high-temperature hole to melt the metal around the cavity. Under the irradiation of the light beam, the high-temperature steam generated by the continuous evaporation of the wall material fills the small holes. The hole walls are surrounded by molten metal, and liquid metal is surrounded by solid material. (In most traditional welding processes and laser conduction welding, energy is first deposited on the surface of the workpiece and then transferred to the inside.) 

The liquid flow outside the hole wall and the surface tension of the wall layer are in a dynamic equilibrium with the continuously generated vapor pressure inside the hole . The light beam enters the hole continuously, and the material outside the hole flows continuously. As the beam moves, the hole is always in a steady state of flow. That is, the molten metal around the hole and the hole wall moves forward with the speed of the guide beam. The molten metal fills the void left by the hole and solidifies, forming a weld. Briefly introduce several characteristics of laser welding:

1. It belongs to fusion welding, and the laser beam is used as energy to impact the welded joint.

2. The laser beam can be guided by a planar optical element (such as a mirror), and then the reflected focusing element or lens will project the laser beam onto the weld.

3. Laser welding is a kind of non-contact welding. It does not need to pressurize during the operation, but it needs to use inert gas to prevent oxidation of molten pool, and occasionally use filler metal.

4. It can be combined with MIG welding to form laser MIG hybrid welding to achieve large penetration depth welding, and the heat input is greatly reduced compared with MIG welding.

Laser welding is one of the technologies used in metal welding processing. Due to its wide application and good effect, it has become one of the mainstream technologies. Metal welding process In laser welding, high temperature is used to burn and bond the surface of the welded metal to form a joint. It has the advantages of high productivity, narrow weld seam, small deformation and high precision. Currently, it is a pulsed laser with high energy density and high efficiency. In the process of metal processing, metal welding processing and spraying design need attention. If we need to weld a workpiece with a narrow internal space during processing, we must consider how to reach the welding torch.