laser penetration

1. Metallurgical Process and Technology Theory

The metallurgical physical process of laser deep penetration welding is very similar to electron beam welding, that is, the energy conversion mechanism is achieved through a "small hole" structure. Under sufficiently high power density beam irradiation, the material evaporates to form small pores. This small hole filled with steam is like a blackbody, absorbing almost all the energy of incident light, and the equilibrium temperature inside the hole reaches around 25000 degrees. Heat is transferred from the outer wall of this high-temperature cavity, causing the metal surrounding the cavity to melt. The small hole is filled with high-temperature steam generated by the continuous evaporation of the wall material under the irradiation of the light beam. The four walls of the small hole surround the molten metal, and the liquid metal is surrounded by the solid material. The flow of liquid outside the pore wall and the surface tension of the wall layer are in dynamic equilibrium with the continuously generated vapor pressure inside the pore cavity. The light beam continuously enters the small hole, and the material outside the small hole flows continuously. As the light beam moves, the small hole remains in a stable state of flow. That is to say, the small hole and the molten metal surrounding the hole wall move forward with the speed of the leading beam, and the molten metal fills the gap left by the small hole moving away and condenses accordingly, thus forming a weld seam.

2. Influencing factors

The factors that affect laser deep penetration welding include: laser power, laser beam diameter, material absorption rate, welding speed, shielding gas, lens focal length, focal position, laser beam position, and laser power gradient control at the starting and ending points of welding.

3. Characteristics and advantages of laser deep penetration welding

Feature:

(1) High aspect ratio. Because molten metal surrounds the cylindrical high-temperature steam chamber and extends towards the workpiece, the weld seam becomes deep and narrow.

(2) Minimum heat input. Due to the high temperature of the source chamber, the melting process occurs extremely quickly, the input heat of the workpiece is extremely low, and the thermal deformation and heat affected zone are very small.

(3) High density. Because the small holes filled with high-temperature steam are conducive to stirring the welding pool and gas escape, resulting in the formation of pore free fusion welding. The high cooling rate after welding can also easily refine the microstructure of the weld seam.

(4) Strong weld seam.

(5) Precise control.

(6) Non contact, atmospheric welding process.

Advantages:

(1) Due to the much higher power density of the focused laser beam compared to conventional methods, the welding speed is faster, the heat affected zone and deformation are smaller, and difficult to weld materials such as titanium and quartz can also be welded.

(2) Because the beam is easy to transmit and control, and does not require frequent replacement of welding torches and nozzles, it significantly reduces downtime and auxiliary time, resulting in high load factor and production efficiency.

(3) Due to its purification effect and high cooling rate, the weld seam is strong and the overall performance is high.

(4) Due to low balanced heat input and high processing accuracy, it can reduce the cost of reprocessing. In addition, the operating cost of laser welding is relatively low, which can reduce production costs.

(5) It is easy to achieve automation and can effectively control the beam intensity and fine positioning.