Views: 0 Author: Site Editor Publish Time: 2025-02-24 Origin: Site
Additional protective gas is usually required during welding, which mainly functions to prevent metal droplets, welding pools, and high-temperature metals in the welding area from being invaded by harmful gases from the outside, prevent oxidation of the weld seam during the welding process, prevent the formation of pores, and ensure the integrity of the weld seam; It can also protect the focusing lens from metal vapor pollution and splashing of liquid droplets. However, there are also some welding methods that do not require shielding gas, such as self shielded flux cored wire arc welding. The flux core inside the welding wire will generate shielding gas and slag during the welding process to protect the welding area; There are also some resistance welding methods such as spot welding, which usually do not require additional protective gas.
As for whether to choose argon or nitrogen, it depends on the different welding materials and processes. The following are the specific situations:
Welding stainless steel: Argon gas is a commonly used protective gas in stainless steel welding. Pure argon is suitable for tungsten inert gas welding (TIG) of stainless steel, but in gas metal arc welding (MIG) using pure argon alone, the surface tension of stainless steel droplets and molten pool is high, the fluidity of liquid metal is poor, and the weld formation is not good. Usually, 1-2% oxygen is added to argon gas to reduce surface tension, enhance fluidity, and make the weld seam form aesthetically pleasing; By adding 2-5% CO ₂, the arc stability is good, oxidation is reduced, the alloy elements are burned less, and there is no tendency to increase carbon. It is suitable for TIG bottom welding and MAG filling cover welding combination processes for stainless steel pipelines.
Welding aluminum alloys: Aluminum alloy GMAW usually uses Ar as a protective gas, which requires high gas purity, otherwise black oxides will appear on both sides of the weld. If you want to increase the welding penetration and speed, you can add a certain proportion of He to Ar, but if the proportion of He is too large, there will be more splashing.
Welding copper and copper alloys: Pure Ar can be used as the welding shielding gas.
Welding nickel and nickel alloys: In addition to using pure Ar and Ar+He as welding shielding gases, a small amount of hydrogen can also be added to Ar gas to improve welding efficiency.
Welding titanium and titanium alloys: Due to the strong bonding between titanium and N, H, and O, pure Ar and Ar+He can only be used as welding shielding gases for GMAW of titanium and titanium alloys.
Welding stainless steel: Nitrides produced by the chemical reaction between nitrogen and stainless steel can improve the strength of the weld joint and enhance the mechanical properties of the weld. Therefore, nitrogen can be used as a protective gas when welding stainless steel, but it is generally not used alone and is mixed with argon and other gases.
Welding copper and copper alloys: When welding copper and copper alloys, a certain proportion of nitrogen can be added to Ar gas to reduce production costs, but there may be some splashing and smoke, resulting in poor forming.
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