Chapter 15 Gas Tungsten Arc Welding
What metals were weldable only by the GTAW process before GMAW was developed?
Aluminum, magnesium, titanium, and some grades of stainless steel
What problem can a long nozzle cause to the tungsten?
Can cause higher tungsten temperature resulting in greater tungsten erosion
What is the correct color to use on the balled end of a pointed and remelted tungsten tip DCEP?
Dull red and bright red
What early advancements made the GTA Welding process more effective?
Improvements in gas compositions and the better understanding of the importance of palority, improve the effectiveness of the process, reduced its cost
What does adding thorium oxide do for the tungsten electrode?
It improves its current carrying capacity
What function regarding tungsten heat do the collet and torch play?
It is cooled by the air or water
What will happen to a water cooled torch cable if the flow of cooling water stops?
It will overheat
Why should the torch be as cool as possible?
Less erosion
Why should a grinding stone that is used for sharpening tungsten not be used for other metals?
Low level of radioactive grinding dust is recommended
Why should the grinding marks run lengthwise on the tungsten electrode end?
Reduces the amount of small particles of tungsten contamination of the weld
What are three ways of breaking off the contaminated end of a tungsten electrode?
Strike with hammer, break off tungsten with two pairs of pliers, and using wire cutters
Why does some tungsten erosion occur?
The intense heat of the arc
What holds the molten ball of tungsten in place at the tip of the electrode during DCEP welding?
The liquid tungsten surface tension with the mass above the molten ball in place
What problem can excessively large tungsten cause?
Too low a temperature for a stable arc
What materials can be used to make nozzles?
alumina, silicon nitride, or fused quartz
How can the end of a tungsten electrode be shaped?
by grinding, alkaline solution, or remelting
inert gas
do not react with any other substance and are insoluble (incapable of being dissolved) in molten metal.
Which two of tungstens properties make it the best choice for GTA welding
high melting temperature and high boiling temperature
Why must the tip of the tungsten be hot?
it will stabilize the arc to melt the tungsten
Why must shielding gas hoses not be made from rubber?
rubber hoses contain oils that can be picked up from the gas
Why must the tube of flow meter be vertical?
so the gas can flow into it.
