Why does Laser Welding Cause Black Solder Joints?

  • By:Iris Liang
  • Date:2021/11/24

Fiber laser welding machine has the advantages of small welding seam, high strength and easy automation. Since its launch on the market, it has been well received by users. At the same time, some users reported that they would encounter oxidation problems with fiber laser welding machines.

The main reasons for blackening are as follows:

The solder joints of the fiber laser welding machine were originally white, but turned black after oxidation. However, when nitrogen is blown into the position of the solder joint, the solder joint will not turn black. Because it is too troublesome to send nitrogen gas, besides nitrogen, is there any other way to make the solder joints white?


The reason for the blackening of the solder joints of the laser welding machine is that the material (usually iron, steel, etc.) is heated and oxidized by the air to form black oxides, such as iron oxide. If you don't want to turn black, it is to prevent the oxidation process. Inert shielding gas is usually blown to prevent oxygen from contacting the welding surface. Argon is common, but nitrogen can also be used. Other methods, vacuum is also possible, but it is more difficult to implement and requires high equipment. Hangao Tech(SEKO Machinery) proposes a cost-effective method: add a welding protective box to the working position of the welding torch. When the welding torch is working, you can continuously inject protective gas into the box to create a protective gas atmosphere and exhaust air, so that the welding point can reduce the contact with air. If customers have requirements in this regard, they can communicate with us directly. Or when communicating the technical details of the stainless steel welded pipe laser welding machine line in the early stage, explain what kind of pipe manufacturing standards your welded pipe products need to pass, and we can also give corresponding design suggestions.


It should also be reminded here that the light produced by a laser welding machine is like sunlight. If it is injected into the human eye, it will accidentally damage the retina of the eye. If it takes a long time to work, it may cause vision loss, which can lead to blindness. Therefore, pay attention to protecting your eyes during work. When you feel a little uncomfortable in your eyes, stop and close your eyes immediately, and then take a break. Don't forget to wear sunglasses, it can also protect your eyes.


Are there other reasons for blackening ?

(1) The temperature between layers is too high. This is the most common, because the temperature between stainless steel welding layers is generally controlled at about 100 degrees. If the weldment is very small, the welds of several layers will reach more than 100 degrees. High attention, will not stop at all to let the temperature of the weldment drop before welding, so the weld will be black.

(2) The current is too large and the welding speed is too slow, resulting in excessive heat input and blackening. Similar to the first reason, it is a problem caused by high temperature.

(3) If gas shielded welding is used, it is possible that the gas is impure and the gas is not well protected.

(4) There is a problem with the quality of the welding consumables, but if the welding consumables we use are from regular manufacturers, this reason can basically be ruled out.




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