How to use auxiliary gas correctly in laser welding
The role of auxiliary gas
In laser welding , auxiliary gas will affect weld formation, weld quality, weld penetration depth and penetration width. In most cases, blowing auxiliary gas will have a positive effect on the weld, but it may also cause damage. Come unfavorable effect.
Positive effects of auxiliary gas
1) The correct blowing of auxiliary gas will effectively protect the weld pool to reduce or even avoid oxidation;
2) The correct blowing of auxiliary gas can effectively reduce the spatter generated during welding;
3) The correct blowing of auxiliary gas can promote the uniform spread of the weld pool during solidification, making the weld shape uniform and beautiful;
4) The correct blowing of auxiliary gas can effectively reduce the shielding effect of the metal vapor plume or plasma cloud on the laser , and increase the effective utilization rate of the laser;
5) The correct blowing of auxiliary gas can effectively reduce weld pores.
As long as we choose the correct gas type, gas flow rate, and blowing method, we can get the perfect effect. However, improper use of auxiliary gas will also adversely affect welding.
Negative Effects of auxiliary gas
1) Incorrect blowing of auxiliary gas may cause deterioration of welds:
2) Choosing the wrong gas type may cause cracks in the weld, and may also reduce the mechanical properties of the weld;
3) Choosing the wrong gas blowing flow rate may cause more serious weld oxidation (whether the flow rate is too large or too small). It may also cause the weld pool metal to be seriously interfered by external forces and cause the weld to collapse or form unevenly;
4) Choosing the wrong gas blowing method will cause the welding seam to fail to achieve the protection effect or even basically no protection effect or have a negative influence on the welding seam formation;
5) Blowing in shielding gas will have a certain effect on the weld penetration, especially when welding thin plates, it will reduce the weld penetration.
Types of auxiliary gas
Commonly used auxiliary gases for laser welding are mainly N2, Ar, He, and their physical and chemical properties are different, and therefore their effects on the weld are also different.
1. Nitrogen N2
The ionization energy of N2 is moderate, higher than that of Ar and lower than that of He. Under the action of laser, the ionization degree is moderate, which can reduce the formation of plasma cloud and increase the effective utilization rate of laser. Nitrogen can chemically react with aluminum alloy and carbon steel at a certain temperature to produce nitrides, which will increase the brittleness of the weld, reduce the toughness, and will have a greater adverse effect on the mechanical properties of the weld joint. Therefore, we don’t suggest to use nitrogen to protect aluminum alloy and carbon steel when welding.
The nitride produced by the chemical reaction between nitrogen and stainless steel can increase the strength of the weld joint, which will help improve the mechanical properties of the weld. Therefore, nitrogen can be used as a shielding gas when welding stainless steel.
2. Argon Ar
The ionization energy of Ar is relatively low, and the ionization degree is high under the action of laser, which is not conducive to controlling the formation of plasma cloud, and will have a certain impact on the effective utilization of laser. However, the activity of Ar is very low and it is difficult to chemically interact with common metals. Besides, the cost of Ar is not high. In addition, the density of Ar is higher. It is beneficial for sinking to the top of the weld pool and can better protect the weld pool, so it can be used as a conventional shielding gas.
3. Helium He
He has the highest ionization energy, and the ionization degree is very low under the action of laser, which can well control the formation of plasma cloud. The laser can act on metals very well. And it has very low activity and basically does not chemically react with metals. It is a good shielding gas for welding seams, but the cost of He is too high. Generally, mass production products will not use this gas. He is generally used for scientific research or products with very high added value.