Laser welding is widely used in various industries with the advantages of energy concentration, high precision and good effect.
Laser welding machine will not only bring us convenience, but also produce many uncertain factors.
When using the laser welding machine, if the operation is improper or the process is not perfect, there are often pores in the welding process.
To solve this problem, first analyze the causes of pores, and then give the corresponding solutions according to the causes.
Why do pores occur during welding?
Porosity is caused by the capture of gas in the solidification process of weld metal.
The cooling rate of weld metal in laser welding is much faster than that in conventional welding, so gas is not easy to escape from the weld and stay in the weld to form pores.
Causes of pores:
On the one hand, due to the limitation of sintering and pressing conditions, powder metallurgy materials can not achieve the same compactness as smelting materials;
On the other hand, porosity is also the most common defect in the process of laser welding.
In the process of photoplasma control, the dynamic pressure of auxiliary gas affects the flow of molten pool and the escape of gas in the small hole, which is a direct result of deep penetration welding.
Weld formation process
The relationship between the number of pores and the size of laser power shows that the number of pores increases with the increase of laser power.
It is speculated that the increase of power will heat the molten metal to a very high temperature, produce metal vapor, make the liquid metal in the molten pool unstable and produce turbulence.
Reducing the laser power and increasing the welding speed can reduce the formation of metal vapor and inhibit the formation of pores.
Method for preventing laser welding from producing air hole
Based on the principle of metallurgy, active gas is used to make the gas dissolve in the weld or react with the molten pool metal to form compounds;
Pulse laser welding is used to change the behavior of the small hole and reduce the shielding gas being drawn into the small hole.
At present, this method can not completely eliminate pores;
The method of beam swing is used to reduce or eliminate the pores in laser deep penetration welding.
Due to the addition of swing in welding, the reciprocating swing of beam on the weld, on the one hand, makes some welds remelt repeatedly, prolonging the residence time of liquid metal in the welding pool.
At the same time, the deflection of beam also increases the input heat per unit area, reduces the depth width ratio of weld, and is conducive to the emergence of bubbles, so as to eliminate pores;
On the other hand, the oscillation of beam flow leads to the oscillation of small holes, which can provide a stirring force for the welding pool, increase the convection and stirring of the welding pool, and play a favorable role in eliminating pores;
With the help of surface cleanliness meter and RFU unit, the relevant data of parts cleanliness can be quickly detected, quantified and recorded.
Based on this data, it can avoid the impact of human subjective judgment, more effectively review the production steps and cleaning procedures, and then optimize the cleaning process, which can greatly improve the work efficiency, reduce the rework rate and reduce the production cost.