Gas for precision welding and fabrication

​Many journeyperson welders consider argon the perfect shielding gas for precision welding and fabrication. Axenics utilizes 99.9% pure argon for tungsten inert gas (TIG) welding for customers that require high-purity welds for their liquid and gas transfer systems and components.

The reasons for using argon in high-purity welding are discussed in a new article for Gasworld magazine, in which Axenics is profiled.

Benefits of argon shielding gas in TIG welding

• Argon is the third most-prominent gas in our atmosphere (behind nitrogen and oxygen). It is universal so it can be used to weld on a wide variety of metals.
• Argon stabilizes the electrical current of the welding torch. This helps with puddle control and manipulation.
• Using argon properly around the weld prevents oxidation.
• Pure argon is affordable. Mixtures of shielding gases often are costly as there is lower demand for them.

“Argon doesn’t interact with molten metal as much as other gases can,” said Ernest Coolong, a welder for Axenics. “We prefer using 99.9999% pure argon when performing TIG welds, as the higher purity rating ensures a superior weld. Argon gas envelops and stabilizes the electrical current of the welding torch to keep the metals from getting oxidized. Argon is one of the most-important elements of high-purity TIG welding.”

Precision welding and fabrication with argon result in:

• A weld quality with the bare minimum of porosity
• An optimal weld bead shape
• A strong, stable weld

Improper or misused shielding gas causes poor welds

Pure argon lowers the exposure of the molten weld pool to harmful elements. A small amount of oxygen in the weld area can jeopardize the weld, leaving holes in the bead or causing spattering. When oxygen and nitrogen get into the weld pool, you can expect defects such as cracks, reduced corrosion resistance, carbide precipitation and brittleness – in other words, a low-quality weld.

Using an improper shielding gas during welding can cause sugaring (oxidation). When the root side of a weld is exposed to oxygen, sugaring occurs. The result looks like granules of black sugar, and this portion of the weld is weaker than the rest, and at risk for a variety of weld failures.

Sugaring also adds contaminants to pure/sterile piping on stainless steel or other corrosion-resistant systems. Sugaring is typically only associated with stainless steels. While it can result in a weaker weld, the bigger concern is the rough/craggy profile and the oxidized metal releasing into the system, contaminating it.

Precision welding and fabrication using TIG

In industries that demand high-purity welding, such as semiconductor and medical devices, the oxidation/sugaring of the weld is a solid gauge to the level of weld quality. Welds with heavy oxidation, dubbed dirty welds, lead to contaminants getting into the contents of the system the tubing is servicing.

To eliminate dirty welds, Axenics welders purge them with inert argon gas on the inside and outside, which greatly reduces the oxidation levels to make cleaner welds. Weld quality and integrity are based on the penetration, oxidation and bead of the weld. A weld is at its strongest when the bead fully penetrates the inner wall of the tubing. A partially penetrated weld proves weaker.

Our expert technicians’ trained eyes look at the beading of the welded joint and quickly tell the difference between a good weld and a bad weld. A good weld is exceptionally consistent in both spacing and width throughout the entire weld. If you inspect a bad weld, you will find a wide variation in the bead width and even the length.

While pure argon is an important part of the equation for ensuring clean welds, there are a variety of other elements that go into achieving perfect high-purity welds.

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