In the field of welding, the main function of nitrogen is to remove oxygen during welding, increase weldability, and prevent reoxidation. Reliable and high-quality welding requires not only suitable solder, but also flux. The main function of flux is to remove oxides from the welding part before welding and prevent reoxidation of the welding part, and to form excellent wetting conditions for the solder and improve weldability. Nitrogen has become one of the most commonly used and most important reactive gases in laser welding.