Difference in weld appearance quality
Argon arc welding
The weld appearance of argon arc welding is usually more beautiful. In non-melting electrode argon arc welding (TIG), because the tungsten electrode does not melt, the arc is stable and concentrated, and the shape and size of the molten pool can be accurately controlled. Its droplet transition is achieved by electromagnetic force and surface tension, and the transition process is uniform and smooth. This makes the weld surface smooth and flat, the fish scale pattern is fine and regular, and there is almost no spatter. For example, when welding stainless steel sheets, the appearance quality of the weld is very high, which can meet the occasions with strict requirements on appearance, such as welding of stainless steel kitchenware, decorations, etc.
Although there is a certain droplet transition in melting electrode argon arc welding (MIG), the appearance of the weld is still excellent due to the good protection of argon gas and the stable arc. However, compared with TIG welding, MIG welding may produce slightly more spatter due to the different ways of droplet transfer, but these spatters are still less than gas shielded welding (especially carbon dioxide gas shielded welding), and can be effectively controlled by adjusting the appropriate welding parameters.
Gas shielded welding
The appearance quality of the weld of carbon dioxide gas shielded welding (a typical representative of gas shielded welding) is slightly inferior. Carbon monoxide (CO) and oxygen (O₂) produced by the decomposition of carbon dioxide under high temperature of the arc will cause a more intense oxidation reaction between the droplet and the molten pool metal. This oxidation reaction causes unstable droplet transfer and produces more spatter. Spatter will adhere to the surface of the weld, affecting the flatness and smoothness of the weld. Although spatter can be reduced by adding deoxidizers (such as silicon, manganese, etc.) to the welding wire, it is difficult to completely eliminate it. However, when welding some structural parts that do not have particularly high requirements for appearance, such as building steel structures, the appearance of the weld is still acceptable.
Differences in internal quality of welds
Tendency to form pores
Argon arc welding: Argon used in argon arc welding is an inert gas, which can effectively prevent air from entering the molten pool during welding. Therefore, the possibility of pores in argon arc welding welds is relatively low. Especially when welding non-ferrous metals (such as aluminum, magnesium) and high-alloy steels, since these materials are more sensitive to pores, the inert gas protection of argon arc welding can well meet the welding requirements. For example, when welding aluminum alloys, argon can prevent harmful gases such as hydrogen (H₂) from dissolving into the molten pool, thereby reducing the generation of pores.
Gas shielded welding: In carbon dioxide gas shielded welding, carbon dioxide gas itself has a certain oxidizing property. Under the high temperature of the arc, carbon dioxide will decompose to produce carbon monoxide (CO). If the molten pool solidifies too quickly, CO will not have time to escape and pores will form in the weld. Moreover, if the protective gas flow is insufficient or there is wind in the welding environment, air can easily enter the molten pool, which will also increase the probability of pore formation. However, by optimizing welding parameters (such as adjusting welding speed, gas flow, etc.) and taking appropriate wind protection measures, the risk of pores can be reduced to a certain extent.
Purity of weld metal and burning of alloy elements
Argon arc welding: The inert nature of argon makes the purity of weld metal higher. During the welding process, alloy elements are not easily oxidized and burned, and can be well retained in the weld metal. For example, when welding stainless steel, alloy elements such as chromium (Cr) and nickel (Ni) can maintain their original content under argon protection, thereby ensuring that the corrosion resistance and other properties of the weld are similar to those of the parent material.
Gas shielded welding: Due to the oxidizing nature of the shielding gas, alloy elements in the weld metal are easily oxidized in carbon dioxide gas shielded welding. For example, when welding alloy steel, some alloy elements may react with oxygen, resulting in a decrease in their content in the weld and affecting the performance of the weld. However, by adding appropriate alloy elements to the welding wire for supplementation, this loss can be compensated to a certain extent.
Differences in mechanical properties and corrosion resistance of welds
Argon arc welding: Due to the high purity of weld metal and less burnout of alloy elements, the mechanical properties and corrosion resistance of argon arc welding welds are usually better. When welding non-ferrous metals and alloy steels, the strength, toughness and other mechanical properties of the weld can be well matched with the parent material. Moreover, for materials that require corrosion resistance (such as stainless steel and aluminum alloys), the corrosion resistance of argon arc welding welds can reach a higher level and can meet the requirements of long-term use in harsh environments.
Gas shielded welding: The mechanical properties of carbon dioxide gas shielded welding welds can also reach a better level under reasonable welding parameters and welding wire selection. However, due to the possibility of alloy element burnout and slightly higher oxygen content in its weld metal, it may be slightly insufficient in some occasions with extremely high requirements for mechanical properties and corrosion resistance. However, when welding ordinary structural parts of carbon steel and low alloy steel, as long as the welding process is well controlled, its mechanical properties and corrosion resistance can still meet the use requirements.
