Can N2 be used as a substitute for argon in TIG welding?

Strictly speaking, a welding procedure qualification should be carried out to determine whether the results obtained from weld appearance inspection, non-destructive testing, tensile testing, bending testing, and impact testing are acceptable. However, on-site we often use nitrogen instead of argon for filling the tube as a protective measure. The main purpose of filling the tube with gas is to remove all the air from it in order to prevent oxidation of the metal during welding. Since nitrogen has a higher density than air and far exceeds that of argon, it is not possible to completely remove all the air from the tube; this is especially true when welding at fixed joints, where the protection of the upper welds is somewhat weaker. Therefore, I personally believe that it is feasible to use nitrogen as a substitute in some ordinary pipelines that are not ultra-low carbon and operate under moderate pressure and temperature conditions.

Let me tell you something – it’s not possible. TIG welding has strict technical requirements. Argon is an inert gas, while nitrogen is not; chemical reactions occur at high temperatures, but this does not happen with argon. If you really don’t need argon, then isn’t it better to use electric welding? Never use nitrogen as a substitute!

Agree with the view from the third floor. It cannot replace it! Tungsten inert gas welding makes use of the fact that argon is an inert gas; it employs argon as a shielding gas to prevent the metal from oxidizing. It involves passing argon gas around the area where arc welding takes place as a protective shield, thereby keeping air out of the welding zone and preventing oxidation there. 　　TIG welding is divided into two types based on the electrode used: gas tungsten arc welding with a consumable electrode and gas tungsten arc welding without a consumable electrode. 　　1. Working principle and characteristics of gas tungsten arc welding Gas tungsten arc welding involves an arc burning between a non-melting electrode (usually a tungsten electrode) and the workpiece. An inert gas that does not react chemically with metals (often argon) flows around the welding arc, creating a protective gas shield that prevents the tungsten tip, the arc, the molten pool, and the metal at high temperatures from coming into contact with air, thereby preventing oxidation and the absorption of harmful gases. Thus, a dense weld joint is formed, which has excellent mechanical properties. 　　2. Working principle and characteristics of gas metal arc welding with a melting electrode The weld wire is fed in through a wire feed wheel; the electrode tip conducts electricity, creating an arc between the base material and the weld wire, which melts both the weld wire and the base material. An inert gas, argon, is used to protect the arc and the molten metal during the welding process. The difference between it and TIG welding is that in the former, the welding wire serves as the electrode, which is continuously melted and fed into the weld pool; after cooling, it forms the weld seam ； The other is the shielding gas; with the application of gas metal arc welding technology, shielding gases have evolved from pure argon to a wide range of mixed gases, such as an argon-rich shielding gas composed of 80% Ar and 20% CO2. Usually, the former is called MIG, and the latter is called MAG. In terms of their operation methods, the most widely used ones at present are semi-automatic GMAW and welding with an argon-enriched gas shield, followed by automatic GMAW. 　　Compared with tungsten inert gas welding, gas metal arc welding has the following characteristics. 　　(1) High efficiency: due to its high current density, heat is concentrated, resulting in a high deposition rate and fast welding speed. Additionally, it is prone to arcing. 　　(2) Enhanced protection is required. Due to the intense arc light and large amount of smoke, enhanced protection measures are necessary. 　　3. Protective Gas 　　(1) The most commonly used inert gas is argon. It is a colorless, odorless gas; its concentration in air is 0.935% by volume. Argon has a boiling point of -186°C, which lies between the boiling points of oxygen and helium. Argon is a by-product of oxygen production in oxygen plants, which is obtained through the distillation of liquid air. 　　Bottled argon is used for welding in our country, with a filling pressure of 15 MPa at room temperature. The gas cylinder is painted gray and marked with the word “Argon”. The chemical composition requirement for pure argon is: Ar≥99.99% ； He≤0.01％ ； O2≤0.0015% ； H2≤0.0005% ； Total carbon content ≤ 0.001% ； Moisture content ≤ 30 mg/m3. 　　Argon is an ideal shielding gas; it is 25% denser than air, which helps to protect the welding arc during flat welding and reduces the consumption of shielding gas. Argon is a gas with extremely low chemical reactivity; it does not react chemically with metals even at high temperatures, thereby avoiding oxidation and burnout of alloying elements as well as the various problems that arise from this. Argon is also insoluble in liquid metal, so it does not cause porosity. Argon is a monatomic gas that exists in atomic form; at high temperatures, there is no molecular decomposition or atomic heat absorption. Argon has a low specific heat capacity and thermal conductivity, which means it absorbs little heat itself and also transfers little heat outward. As a result, the heat in the arc is not easily dissipated, allowing the welding arc to burn steadily with heat concentrated, which facilitates the welding process. 　　The disadvantage of argon is its high ionization potential. When the arc space is filled with argon, it is more difficult to ignite the arc, but once ignited, the arc remains very stable. 　　4. Disadvantages of TIG welding: (1) Due to the large heat-affected zone, TIG welding often results in defects such as deformation of the workpiece after repair, reduced hardness, porosity, local annealing, cracking, pinholes, wear, scratches, undercutting, as well as insufficient adhesion and internal stress damage. This is particularly evident in the process of repairing small defects in precision castings, where it appears on the surface. In the field of repairing defects in precision castings, a cold welding machine can be used as a substitute for TIG welding. Due to its low heat generation, the cold welding machine overcomes the disadvantages of TIG welding and addresses the challenges associated with repairing precision castings. 　　Compared to shielded metal arc welding, TIG welding causes greater harm to the human body. TIG welding has a higher current density and emits more intense light; the ultraviolet radiation generated by its arc is about 5 to 30 times that of conventional shielded metal arc welding, while the infrared radiation is about 1 to 1.5 times that of shielded metal arc welding. The level of ozone produced during welding is also high. Therefore, it is advisable to carry out welding in areas with good air circulation, as failing to do so can cause serious harm to the body. For reference only!

It’s still not clear whether it can be used or not

Nitrogen cannot be used as a substitute; otherwise, it would become nitrogen arc welding. The purity of nitrogen has a direct impact on the hardness and toughness of the welds made from pure titanium, and it also significantly affects the occurrence of welding cracks. When welding, the argon gas used must be high-purity argon (Argon 99.99% enriched), with a dew point below –40°C and a H2O content of less than 0.001 mL/L.

To correct that, TIG welding generates more heat than electric welding, so the heat-affected zone should be narrower than that in electric welding.

No, nitrogen is oxidizing at high temperatures, and it’s more readily available than argon; so why use argon from the start? Surely others have tried it before (non-professional perspective)

I’ve heard of TIG welding, but I’m not familiar with nitrogen welding: lol

No. Adding about 2% N2 to argon gas can be used to weld certain duplex stainless steels, as it helps to supplement the nitrogen content in the weld metal. Pure N2 can be used as a back shielding gas in TIG welding to prevent the back side of the metal from oxidizing.

It’s not possible; argon is an inert gas, but nitrogen isn’t. During welding, it reacts with the metal in the molten pool, and an excess of nitrogen in the weld metal can lead to the formation of nitrogen pores.