Can You Weld with Nitrogen?

You can weld with nitrogen, but only in specific applications. Nitrogen isn’t typically used as a primary shielding gas like argon or helium, but it serves valuable purposes in specialized welding scenarios.

In this article, we’ll go over those scenarios to explain when you should use nitrogen in welding. We’ll also explore its advantages and limitations of nitrogen, as well as best practices for its optimal use..

Nitrogen as a Purging Gas

Nitrogen excels as a purging gas, particularly when welding stainless steel, duplex stainless steel, and other corrosion-resistant alloys. Purging removes oxygen from the internal areas of pipe and tube welds to prevent oxidation.

This process preserves the corrosion resistance of the base material by preventing the formation of oxides on the weld’s root side. Without proper purging, the heat-affected zone becomes susceptible to corrosion, potentially leading to premature failure.

Nitrogen creates an inert atmosphere that displaces oxygen, which makes it ideal for large-volume purging applications. Its lower cost compared to argon makes it economically beneficial for purging large piping systems or vessels.

Nitrogen flow rates of 15-25 liters per minute are recommended for typical stainless steel pipe welding, though this varies based on pipe diameter and configuration. Flow that’s too low won’t adequately displace oxygen, while excessive flow wastes gas and may cool the weld pool too rapidly.

To visualize proper purging, think of it like clearing smoke from a room – you need enough airflow to displace unwanted gases, but not so much that it creates turbulence and draws in more contaminants from open areas.

Nitrogen in Shielding Gas Mixtures

Pure nitrogen is rarely used as a primary shielding gas because it can cause significant problems in the weld pool. Many welding experts and organizations explicitly warn against using nitrogen in shielding gases for most metals due to the risk of nitride formation and embrittlement, which can severely compromise weld integrity. 

Still, small percentages of nitrogen in gas mixtures offer unique benefits for specific applications.

For austenitic stainless steel welding, adding 1-5% nitrogen to an argon base can increase weld penetration in some applications, but may cause rapid tungsten degradation in TIG welding and potentially increase brittleness.. The nitrogen acts as an austenite stabilizer, enhancing the mechanical properties and corrosion resistance of the final weld. However, higher nitrogen concentrations (particularly above 5%) may increase cracking risks, and nitrogen’s effects can vary significantly depending on other welding parameters. Always conduct thorough testing before implementing nitrogen-containing gas mixtures in production environments.

Nitrogen’s role in these mixtures is to increase the heat input to the workpiece without changing the welding parameters. This promotes better fusion and reduces the risk of lack-of-fusion defects.

In laser welding applications, nitrogen is a cost-effective alternative to argon or helium for certain stainless steel applications. It produces a more stable keyhole and reduces plasma formation above the weld pool.

However, too much nitrogen in the shielding gas can lead to nitrogen absorption in the weld metal. This may cause porosity and embrittlement, particularly in carbon steels and most non-ferrous metals.

AWS guidelines specifically warn against using nitrogen-rich shielding gases with titanium, zirconium, and other reactive metals. The nitrogen reacts with these materials to form brittle nitrides that compromise weld integrity.

Specialized Applications in Manufacturing

In plastic welding processes, heated nitrogen gas serves as both the heat source and the protective atmosphere. Unlike conventional hot air welding, nitrogen prevents oxidation of the plastic during the melting process.

This technique is particularly valuable for thermoplastic applications like automotive bumper repair. The absence of oxygen during welding prevents discoloration and degradation of the polymer structure.

In electronics manufacturing, nitrogen atmospheres improve soldering quality by preventing oxide formation on component leads and PCB pads. This enhances wettability of the solder and reduces defects in the final assembly.

For specialized metal joining processes like brazing copper components, nitrogen with 5-10% hydrogen provides both protection from oxidation and helps reduce existing oxides. This dual action results in higher-quality brazed joints with minimal post-process cleaning.

The hydrogen component in forming nitrogen acts much like a microscopic cleaning agent, scrubbing away oxide films that would otherwise prevent proper metal bonding – similar to how pre-cleaning dishes ensures better detergent action.

Safety Considerations and Best Practices

Working with nitrogen requires strict safety protocols due to its asphyxiation risk. Unlike toxic gases that provide warning signs through odor or irritation, nitrogen displacement of oxygen occurs silently and can be lethal.

Luckily, you can avoid incidents by following a few safety practices:

• Adequate ventilation: always ensure proper ventilation when using nitrogen for purging or welding, especially in confined spaces. Oxygen monitors should be employed whenever significant volumes of nitrogen are used in enclosed areas.
• Gas purity: for optimal results with nitrogen in welding applications, maintain gas purity levels appropriate for the application. General purging may use industrial grade nitrogen (99.5% pure), while critical applications might require 99.999% purity.
• Flow control:  use proper gas flow control equipment designed specifically for nitrogen. Standard argon regulators may not provide accurate flow rates due to the different physical properties of nitrogen gas.
• Weld testing: conduct proper weld testing when implementing nitrogen in new applications. Visual inspection, bend testing, and corrosion testing help verify that the nitrogen hasn’t negatively affected weld properties.
• Material compatibility: when using nitrogen as a backing gas, it’s generally recommended only for 300-series stainless steels. Using nitrogen with other steel grades can lead to compatibility issues and potential weld failures.

When incorporating nitrogen into shielding gas mixtures, follow manufacturer recommendations for your specific welding process and base material. Pre-mixed gases from reputable suppliers ensure consistent composition and reliable results.

Find Ways To Use Nitrogen in Welding

Nitrogen comes with valuable benefits for specific welding applications when used appropriately. Its primary strengths lie in purging applications for stainless steel and as a component in specialized shielding gas mixtures.

Understanding nitrogen’s limitations is just as important as recognizing its benefits. With proper application, safety protocols, and quality control, nitrogen can be a cost-effective addition to your welding gas arsenal.