Selection of shielding gas for precision laser welding machine
The commonly used protective gases of precision laser welding machine are argon, nitrogen and nitrogen. If the Nd: YAG laser pulse welding, because the formation of solder joint time is short, not easy to produce plasma, plus the oxide formation tendency is small, so Nd; YAG laser spot welding generally does not use gas protection; However, oxidation film or metal vapor deposits may form on the surface of the solder joint. If repeated pulses are used for seam welding, the oxidation film or sediment formed in the first time may enter the second welding spot and affect the quality of the weld. Therefore, continuous welding for Nd: YAG laser should use gas protection. Nitrogen is suitable for cq laser welding shielding gas, its ionization energy is high, itself is not easy to form plasma, favorable to obtain a large weld depth. In addition, its density is smaller than air, in the weld is not easy to form gas.
Nitrogen is a common protective gas for welding stainless steel and titanium alloy. But helium is expensive, increasing production costs. Nitrogen also has a better protective effect, and its disadvantage is that it is easy to cause brittleness of welding seam. It is often used in the welding of general structural parts, such as the shell of household electrical equipment. Argon has good oxidation resistance, but its ionization energy is lower than helium and nitrogen, and it can form plasma under the action of high-energy density laser. In addition, ammonia gas is difficult to escape from liquid metal, easy to form pores; If a penetration weld is performed, ammonia has a chance to escape from the bottom of the weld. Sometimes, a suction device is installed in the welding line to discharge argon gas from the welding seam, avoiding the radiation of laser, and ammonia can be used without causing plasma production. It costs less than helium and can be produced in large quantities at significantly reduced production costs.