In laser welding, protective gas will affect weld forming, weld quality, weld depth and weld width. In most cases, blowing protective gas will have a positive effect on the weld, but it may also bring adverse effects.
1. Correct blowing into the protective gas will effectively protect the weld pool to reduce or even avoid oxidation;
2. Correct blowing into the protective gas can effectively reduce the splash generated in the welding process;
3. The correct blowing into the protective gas can make the weld pool solidification evenly spread, make the weld forming uniform and beautiful;
4. Proper 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. Proper blowing of protective gas can effectively reduce the porosity of weld.
As long as the type of gas, gas flow and blowing mode are selected correctly, the ideal effect can be obtained.
However, improper use of protective gas can also adversely affect welding.
The adverse effects
1. Incorrect blowing of protective gas may lead to poor weld:
2. Choosing the wrong kind of gas may lead to cracks in the weld and reduce the mechanical properties of the weld;
3. Choosing the wrong gas blowing flow rate may lead to more serious weld oxidation (whether the flow rate is too large or too small), and may also cause the weld pool metal to be seriously disturbed by external force, resulting in weld collapse or uneven molding;
4. Choosing the wrong gas blowing way will lead to the failure of the protection effect of the weld or even basically no protection effect or have a negative impact on the weld forming;
5. Blowing in protective gas will have a certain impact on the weld depth, especially when the thin plate is welded, it will reduce the weld depth.
Type of protection gas
The commonly used laser welding protection gases are mainly N2, Ar, He, whose physical and chemical properties are different, so the effect on the weld is also different.
1. N2
The ionization energy of N2 is moderate, higher than that of Ar and lower than that of He. The ionization degree of N2 is general under the action of laser, which can better reduce the formation of plasma cloud and thus increase the effective utilization rate of laser.Nitrogen can react with aluminum alloy and carbon steel at a certain temperature, producing nitride, which will improve the brittleness of the weld, and reduce toughness, which will have a great adverse effect on the mechanical properties of the weld joint, so it is not recommended to use nitrogen to protect aluminum alloy and carbon steel welds.
The nitrogen produced by the chemical reaction of nitrogen and stainless steel can improve the strength of the weld joint, which will be conducive to the improvement of the mechanical properties of the weld, so nitrogen can be used as a protective gas when welding stainless steel.
2. Ar
Ar ionization energy relative to the minimum, under the effect of laser ionization degree is higher, is not conducive to control the formation of plasma cloud, can effective utilization of laser produce certain effect, but the Ar activity is very low, it is difficult to react with common metals, and Ar cost is not high, in addition, the density of Ar is bigger, is advantageous to the sink to the weld molten pool above,It can better protect the weld pool, so it can be used as a conventional protective gas.
3. He
He has the highest ionization energy, under the effect of laser ionization degree is low, can very good control the formation of plasma cloud, laser can be work well in the metal, WeChat public number: micro welder, activity and He is very low, basic does not react with metals, is a good welding protective gas, but He is too costly,The gas is not used for mass production products, and He is used for scientific research or very high value-added products.
Post time: Sep-01-2021
