Precision welding, such as TIG welding, produces clean and exceptionally accurate welds. Precision welds are defined as the purest welds for joining tubes and fittings on both metals and plastics. A precision weld’s bead fully penetrates the inner wall of a tube, pipe or fitting. This results in a superior weld with zero contamination and a low chance for leaks, fissures or other faults.
TIG is ideal for precision welding
TIG is an abbreviation of tungsten inert gas, and TIG welding is also called gas tungsten arc welding (GTAW). With TIG welding, two metals join using heat from an arc created by a non-consumable tungsten electrode and a base metal. Most welders consider TIG to be the top choice for precision welding, more so than other arc welding methods, including metal inert gas (MIG) welding.
MIG welding uses a consistent wire fed to the heating element to melt metals together. It’s not as precise as TIG welding, and MIG welding basic skills are generally easier to learn than TIG welding skills.
Think of this analogy: Many humans run, but, 99.9% of them don’t run fast enough for the Olympics. The Olympics is the caliber of welds produced by TIG welding.
High-purity metals with zero contaminants are required for precision welding, though precision welding occurs on many different types of metal, including different grades of stainless steel, aluminum, Inconel and Monel. Because of TIG welding’s precise nature, it’s also possible to weld thinner metals at a lower amperage.
TIG welding has two joining methods for metals, autogenous weldments or homogenous weldments. Autogenous weldments do not rely on filler materials while homogenous weldments will use a filler material.
Precision welding uses
The pinpoint welds perfected by precision welding are essential to industries like medical device manufacturing and semiconductors, where the tolerances between two pieces of fused metal must be miniscule. Precision welds are an important factor in the advancement of semiconductors that are used in life-saving medical devices, which are constantly getting smaller while increasing functionality.
TIG precision welding is a repeatable process, which is important for semiconductor manufacturers who often need multiple, clean welds that are the same each time. Precision welds are necessary when fabricating semiconductor microchips through complex assemblies and subassemblies.
TIG welding is also the preferred method for precision, hard-to-reach weld areas. Precision welding also occurs on components used in hydrogen fuel cells in the alternative energy industry.
Precision welding should occur in a cleanroom to ensure contaminants cannot enter the welded components.
Tungsten and argon in precision welding
Tungsten is ideal for use in precision welding due to its high melting point of 3,410 degrees Celsius. TIG welding adheres metals with heat provided by an arc from a tungsten electrode. The arc develops heat to melt a base metal. When an arc and weld pool form, heat applies to a joint with the arc actively melting the areas of metal for fusing. The quality of the tungsten electrode greatly affects the stability of the arc, and the precision of the weld.
High-quality tungsten aids in the conduction of electricity and ultimately strengthens the weld. Good tungsten allows further smoothing of the arc, which makes precision welding easier. The refinement of the arc offers improvement during the coalescing of metals. The actual moment in which two metals melt together is the most important for top-quality precision welding.
Argon is often the shielding gas used in precision welding. It makes sense to use 99.9% pure argon for high-purity precision welds that become part of liquid and gas transfer systems and components, because the higher purity rating ensures a superior weld.
Benefits of argon shielding gas in precision welding:
- Argon is the third most-prominent gas in the atmosphere (after nitrogen and oxygen). Argon is universal so it can be used to weld on a wide variety of metals.
- Argon stabilizes the electrical current of the welding torch, helping 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 a lower demand.
Precision welding with pure argon results in:
- A weld quality with the bare minimum of porosity.
- An optimal weld bead shape.
- A strong, stable weld.
Precision welding challenges
Sugaring (oxidation): When the root side of a weld gets exposed to oxygen, sugaring or oxidation may occur. The result looks like the granules of sugar, which indicate this area of the weld is weak and at risk for cracking, corrosion and other faults.
Using the wrong arc length: A short arc length (not enough voltage) may cause slower melting of the tungsten electrode, which results in incomplete weld fusion and other possible issues. Long arcs (too much voltage) often result in weld porosity, which is excessive spatter of the filler metal into the weld joint.
Using dirty filler material: Filler metals containing particles or other contaminants will not produce a clean weld and may cause weld failure. Using dirty filler material goes against the basic principle of clean welding.
Creating craters: Weld craters occur when a weld pool does not contain adequate volume after cooling to overcome shrinkage stress, which can cause cracks in the weldment. Slowly reducing the current while completing the weld is one way to avoid this issue.
Creating warped or defective welds due to unbalanced heating: A frequent cause of excess heating on the tungsten is electrode positive duration, making it difficult to control the weld puddle.
One thing to keep in mind; mistakes made in precision welding generally cannot be undone. Precision welding is typically slower than other welding techniques, but the results are exceptionally high-quality, resulting in refined and superior welds.
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The demand for plastic welding services grows along with the white-hot demand for semiconductor manufacturing. Plastic welding is a specialty of Axenics’ welding experts, and their techniques are profiled in a new article in the March 2021 issue of Welding Journal...