Laser Welding, Do You Know All About the "Gas"?

  • By:Iris Liang
  • Date:2021/12/01

Have you encountered any welding defects such as large splashes during welding, unsightly weld formation, and a large number of pores after welding? When you are still considering whether it is because of the problem of laser welding process parameter settings, do you know that the correct use of welding shielding gas is also an important factor affecting weld formation and performance. Choosing the best welding shielding gas actually improves welding quality and The efficient way.

Since welding shielding gas is so important, then: What is the role of shielding gas? How to choose the type of shielding gas? How should the shielding gas be blown in during welding? Next, Hangao Tech (SEKO Machinery) will lead everyone to learn more.

The role of protective gas

In laser welding, shielding gas will affect weld formation, weld quality, weld penetration depth and penetration width. In most cases, blowing shielding gas will have a positive effect on the weld, but it may also cause damage. Come unfavorable 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 the welding process;

3) The correct blowing of shielding gas can promote the uniform spread of the weld pool during solidification, so that the weld is formed uniformly and beautifully;

4) The correct blowing of shielding 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 shielding gas can effectively reduce the welding seam porosity.

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:

①Selecting the wrong gas type may cause cracks in the weld, and may also cause the mechanical properties of the weld to decrease;

②Selecting the wrong gas blowing 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 form unevenly;

③Selecting 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 impact on the welding seam formation;

2) 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 protective gas

Commonly used shielding gases for laser welding mainly include N2, Ar, He, and their physical and chemical properties are different, and therefore their effects on the weld are also different.

Nitrogen N2

The price is the cheapest, but it is not suitable for welding some stainless steels. 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 average, 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 have a greater adverse effect on the mechanical properties of the weld joint. Therefore, it is not recommended to use nitrogen. Aluminum alloy and carbon steel welds are protected.

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.

Argon Ar

The price is cheaper, the density is higher, and the protection effect is better. The surface of the weldment is smoother than helium gas, but it is susceptible to high-temperature metal plasma ionization. Deeply hindered. 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. 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 can better protect the weld pool, so it can be used as a conventional shielding gas.

Helium He

The price is more expensive, but the effect is the best, so that the laser can pass directly and reach the surface of the workpiece without being blocked. The ionization energy of He is the highest, 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 metal very well, and the activity of He is very low, and it basically does not chemically react with metal. 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.

Hangao Tech (SEKO Machinery) has more than 20 years of experience in the stainless steel industrial pipe production line tube making machines manufacturing industry. The mature R&D team and assembly technicians will conduct a full range of debugging and repeated verification on each production line before shipment, so as to maximize the equipment. Limit the efficiency and reduce the difficulty of later installation and debugging for customers.

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