Handheld laser welding machine is a new type of welding method, mainly for welding thin-walled materials and precision parts, which can realize spot welding, butt welding, lap welding, sealing welding, etc., with high depth ratio, small weld width, and low heat impact Small area, small deformation, fast welding speed, smooth and beautiful weld seam, no need to deal with or only need simple treatment after welding, high quality weld seam, no porosity, precise control, small focus spot, high positioning accuracy, easy to realize automation .
Why use shielding gas when laser welding?
1. It can protect the focusing lens from metal vapor pollution and sputtering of liquid droplets
The shielding gas can protect the focusing lens of the laser welding machine from metal vapor pollution and sputtering of liquid droplets, especially in high-power welding, because the ejection becomes very powerful, and it is more necessary to protect the lens at this time.
2. Shielding gas is very effective in dispelling plasma shielding generated by high-power laser welding
The metal vapor absorbs the laser beam and ionizes into a plasma cloud, and the protective gas around the metal vapor is also ionized due to heat. If too much plasma is present, the laser beam is somewhat consumed by the plasma. Plasma exists on the working surface as a second energy, which makes the penetration shallow and the surface of the weld pool widen. The recombination rate of electrons is increased by increasing the three-body collisions of electrons with ions and neutral atoms to reduce the electron density in the plasma. The lighter the neutral atoms, the higher the collision frequency and the higher the recombination rate; on the other hand, only the protective gas with high ionization energy will not increase the electron density due to the ionization of the gas itself.
3. The protective gas can protect the workpiece from oxidation during the welding process
The laser welding machine must use a kind of gas for protection, and the program should be set in such a way that the protective gas is emitted first and then the laser is emitted, so as to prevent the oxidation of the pulsed laser during continuous processing. The inert gas can protect the molten pool. When some materials are welded regardless of the surface oxidation, the protection may not be considered. However, for most applications, helium, argon, nitrogen and other gases are often used as protection to prevent the workpiece from being welded during welding. subject to oxidation.
In laser welding, shielding gas will affect the weld shape, weld quality, weld penetration and penetration width. In most cases, blowing shielding gas will have a positive effect on the weld, but it may also bring come to an adverse effect.
positive effects:
1) The correct blowing of shielding gas will effectively protect the weld pool to reduce or even avoid oxidation;
2) The correct blowing of shielding gas can effectively reduce the spatter generated during welding;
3) The correct blowing of the protective gas can promote the uniform spreading of the weld pool when it solidifies, making the weld shape uniform and beautiful;
4) Correct blowing of protective gas can effectively reduce the shielding effect of metal vapor plume or plasma cloud on laser, and increase the effective utilization rate of laser;
5) Correct blowing of shielding gas can effectively reduce weld porosity.
As long as the gas type, gas flow rate, and insufflation method are selected correctly, the ideal effect can be obtained. However, incorrect use of shielding gas can also have adverse effects on welding.
Negative Effects:
1) Improper insufflation of shielding gas may result in poor welds:
2) Choosing the wrong type of gas may cause cracks in the weld, and may also lead to a decrease in the mechanical properties of the weld;
3) Choosing the wrong gas blowing flow rate may lead to more serious oxidation of the weld (whether the flow rate is too large or too small), and may also cause the weld pool metal to be seriously disturbed by external forces, resulting in weld collapse or uneven forming;
4) Choosing the wrong gas injection method will cause the weld to fail to achieve the protection effect or even basically have no protection effect or have a negative impact on the weld formation;
5) Insufflation of protective gas will have a certain impact on the weld penetration, especially when welding thin plates, it will reduce the weld penetration.
The above is the reason why shielding gas is used when laser welding machine welding. Remind you that helium is generally used as the shielding gas, which can suppress the plasma to the greatest extent, thereby increasing the penetration depth and improving the welding speed; and it is light in weight and can escape, and it is not easy to cause pores. Of course, from our actual welding effect, the effect of using argon protection is not bad.