Views:17 Author:Crystal Publish Time: 2021-05-24 Origin:Site
Shielding gas is used in industrial laser welding machine. Shielding gas will affect weld formation, weld quality, weld penetration, etc. In most cases, blowing in shielding gas will have a positive effect on the weld, but it may also have an adverse effect.
Positive effect of blowing in protective gas correctly
1) Effectively protect the weld pool from being reduced to avoid oxidation;
2) It can effectively reduce the spatter generated in the welding process;
3) Promote the uniform spread of the weld pool during solidification, and the weld shape is uniform and beautiful;
4) Increase the effective utilization rate of the laser;
5) Effectively reduce the weld pores.
As long as the gas type, gas flow rate, and blowing method are selected correctly, the desired effect can be obtained. However, incorrect use of shielding gas will also have an adverse effect on welding.
1) Incorrect blowing of shielding gas may cause deterioration of the weld:
2) Choosing the wrong gas may cause cracks in the weld, and may also reduce the mechanical properties of the weld;
3) Choosing the wrong gas flow rate may cause more serious oxidation of the weld (whether the flow is too large or too small), and may also cause the weld pool metal to be seriously interfered by external forces and cause the weld to collapse or unevenly form;
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, which will have a negative impact on the welding seam formation;
5) Blowing in shielding gas will have a certain impact on the weld penetration, especially when welding thin plates, it will reduce the weld penetration.
Commonly used shielding gases for laser welding are mainly N2, Ar, He, and their physical and chemical properties are different, and their effects on welds are also different.
The ionization energy of N2 is moderate, higher than that of Ar and lower than that of He. Under the action of laser, the degree of ionization is general, which can reduce the formation of plasma 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 have a greater adverse effect on the mechanical properties of the weld joint. Therefore, it is not recommended to use nitrogen.Therefore, when use 1kw laser welding machine,it is not recommended to use nitrogen to protect aluminum and carbon steel welds.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.So nitrogen can be used as a shielding gas when welding stainless steel.
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 affect the effective utilization of the laser. However, the activity of Ar is very low and it is difficult to chemically react with common metals. The cost of Ar is not high. In addition, the density of Ar is higher, which is beneficial to sink to the top of the weld pool and better protect the weld pool, so it can be used as a conventional shielding gas.
He has the highest ionization energy, and the ionization degree is very low under the action of laser, which can control the formation of plasma cloud. The laser can act on metals very well, and He has very low activity and basically does not chemically react with metals.However, the cost of He is too high, and the gas will not be used in mass production. He is generally used for scientific research or products with very high added value.
At present, during the use of industrial laser welding machines,there are two main ways of blowing in shielding gas: one is to blow the shielding gas on the side shaft side, and the other is the coaxial shielding gas.Generally, it is recommended to use side blowing protective gas.The selection of shielding gas directly affects the quality, efficiency and cost of welding production. Due to the variety of welding materials, the selection of welding gas is also complicated in the actual welding process, which requires comprehensive consideration of welding materials, welding methods, welding positions and required welding effects.Only through welding test can a more suitable welding gas be found to achieve better welding results.
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