Quality
Gas tungsten arc welding, because it affords greater control over the weld area than other welding processes, can produce high-quality welds when performed by skilled operators. Maximum weld quality is assured by maintaining cleanliness—all equipment and materials used must be free from oil, moisture, dirt and other impurities, as these cause weld porosity and consequently a decrease in weld strength and quality. To remove oil and grease, alcohol or similar commercial solvents may be used, while a stainless steel wire brush or chemical process can remove oxides from the surfaces of metals like aluminum. Rust on steels can be removed by first grit blasting the surface and then using a wire brush to remove any embedded grit. These steps are especially important when negative polarity direct current is used, because such a power supply provides no cleaning during the welding process, unlike positive polarity direct current or alternating current. To maintain a clean weld pool during welding, the shielding gas flow should be sufficient and consistent so that the gas covers the weld and blocks impurities in the atmosphere. GTAW in windy or drafty environments increases the amount of shielding gas necessary to protect the weld, increasing the cost and making the process unpopular outdoors.
The level of heat input also affects weld quality. Low heat input, caused by low welding current or high welding speed, can limit penetration and cause the weld bead to lift away from the surface being welded. If there is too much heat input, however, the weld bead grows in width while the likelihood of excessive penetration and spatter increase. Additionally, if the welding torch is too far from the workpiece the shielding gas becomes ineffective causing porosity within the weld. This results in a weld with pinholes, which is weaker than a typical weld.
If the amount of current used exceeds the capability of the electrode, tungsten inclusions in the weld may result. Known as tungsten spitting, it can be identified with radiography and prevented by changing the type of electrode or increasing the electrode diameter. In addition, if the electrode is not well protected by the gas shield or the operator accidentally allows it to contact the molten metal, it can become dirty or contaminated. This often causes the welding arc to become unstable, requiring that electrode be ground with a diamond abrasive to remove the impurity.
Read more about this topic: Gas Tungsten Arc Welding
Famous quotes containing the word quality:
“Talent alone can not make a writer. There must be a man behind the book; a personality which by birth and quality is pledged to the doctrines there set forth, and which exists to see and state things so, and not otherwise; holding things because they are things.”
—Ralph Waldo Emerson (1803–1882)
“Spindly branches of buttercups were secreted among gleaming stems still moist at the roots from last night’s rain that had washed and refreshed the entire wood, had dowered it in poignant transparency, the unique, inconsolable quality of rainy countries, as if all was glimpsed through tears.”
—Angela Carter (1940–1992)
“Reverence is the highest quality of man’s nature; and that individual, or nation, which has it slightly developed, is so far unfortunate. It is a strong spiritual instinct, and seeks to form channels for itself where none exists; thus Americans, in the dearth of other objects to worship, fall to worshipping themselves.”
—Lydia M. Child (1802–1880)