Intro to Arc Final
Why should the torch be as cool as possible?
80% of the heat does not enter the weld stays in the torch and must be removed
The shielding gas gas mixture for axial spray
95% to 98% argon and 2% to 5% oxygen
In ______ the high heat input to the tungsten indicates that a large-size tungsten is required and the end shape with a ball must be used.
DCEN
Explain how to measure the wire-feed ipm.
Hold the trigger for 6 seconds, measure the length and times that by 10
GMA is almost free from spatter because it uses a mode of metal transfer called _______ metal transfer
axial spray
The shielding gas used on carbon steel is ____.
carbon dioxide, or a mixture of carbon dioxide and argon
What makes helium difficult to use for manual welding?
lighter that air preventing good shielding, difficult to ionize and needs higher voltage to support the arc making it difficult to ignite
The ______ directs the shielding has directly on the welding zone.
nozzle cup
What are three ways of breaking off the contaminated end of a tungsten electrode?
on a sharp corner with a hammer, using two pairs of pliers, and wire cutters
Building up a metal's surface is known as______.
padding
_____ has good balance between penetration and reinforcement and is used on automated welding.
perpendicular welding
______ is the time during which the gas continues flowing after the welding current has stopped.
post flow
The _____ is the time during which gas flow to clear out any air in the nozzle or surround the weld zone.
pre flow
Globular transfer is used more commonly in combination with _____
pulsed spray transfer
In the______ feed system, the electrode must have enough strength to be pushed through the conduit without kinking.
push-type
_______is a function of the time it takes the magnetic field in the transformer to collapse once the coil is de-energized
ramp down
___ refers to how the electric current in a transformer takes a few milliseconds to build up the magnetic field to full strength once the coil is energized.
ramp up
What holds the molten ball of tungsten in place at the tip of the electrode during DCEP welding?
surface tensions with the larger mass above the molten ball holds it in place
Shielding gas used in pulse arc metal transfer on steel.
99% argon and 1% oxygen
Which of the following is true of DCEP?
DCEP has the highest heat concentration on the electrode tip
______ electrodes have a forceful arc with little slag left on the weld bead.
E6010 and E6011
What problems can an excessively large tungsten cause?
Excessively large sizes may result in to low of a temperature for a stabilized arc.
What functions regarding heat do the collet and torch play?
Heat from both the arc and the tungsten electrode resistance to the flow of current must be absorbed by the collet and the torch
Which of the following is true of grinding tungsten electodes?
If the grinder is used for metals other than tunsten, particles of these metals may become trapped on the tungsten as it is ground, resulting in contamination when the arc is started
Which of the following is true of perpendicular welding technique?
It has a good balance between penetrations and reinforcement and is used on automated welding.
______ is a series of ridges cut into the groove.
Knurling
MAG is short for_____.
Metal active gas welding.
_____ is an extremely modified version of ______ and has a very sophisticated computer controlled welding machine.
Modulated current metal transfer, Short circuiting transfer
When should a welder change their body position?
Only during the time an electrode is being changed.
In the pulsed-arc metal transfer current cycle, ______refers to the surging electrical current passing through the transformer like a wave on water.
Overshoot
Which of the following is true of erosion of tunsten electrode?
Slow erosion results in limited tunsten inclusions in the weld.
What will happen to a water-cooled torch cable if the flow of the cooling water stops?
The cable quickly overheats and melts through the hose.
What is the most likely explanation for why DCEP has a cleaning action?
The electrons accelerated from the cathode surface lift the oxides that interfere with their movement. The positive ions accelerated to the metals surface provide addition energy. In combination the electrons and ions cause the surface erosion needed to produce the cleaning
Which 2 tungsten properties makes it the best choice for GTA welding?
The high melting temperature, and good electrical conductivity
Why would a welder need extra burn protection from their eyes when making an axial spray weld.
The high welding current produces a great deal of UV light.
What problems can a long nozzle cause to the tungsten?
The longer a nozzle, the longer the tungsten must be extended from the collect. This can cause higher temperatures resulting in erosion.
Why are argon and helium known as inert gases?
They will not combine chemically with any other material
Why is inert shielding gas required from GTA welding
To keep air away from the hot tungsten and molten weld metal.
Which of the following is a way to minimize erosion of tungsten electrode?
Use DCEN current
what is a way to minimize erosion of the tungsten electrode?
Use DCEN current
Which of the following is true of DCEN?
With DCEN, a pointed tip concentrates the arc
In order to get a good GTA welding on thicken sections of metal, especially _______, you will need to preheat it.
aluminum
What materials were only weldable only by GTAW before GMAW was developed?
aluminum, magnesium, titanium, and some grades of stainless steel
The amount of heat produces by a welding arc is determined by the_____.
amperage
In modulated current metal transfer the wire speed is _______
constant
GMAW power supplies are ____ type machines.
constant-voltage constant-potential
The useful life of a ceramic nozzle if affected by the ______
current level and proximity to the work
Why are the benefits of adding hydrogen to argon for welding?
deep penetration at high welding speeds, weld cleanliness, and bead profile
The _____ rate is the measure of the weld metal deposited.
deposition
What is the correct color to use on the balled end of a pointed and re-melted tungsten tip on DCEP
dull red and bright red
The ______is the distance from the contact tube to the arc measure along the wire.
electrode extension (stick out)
The purpose of the _____ is to provide a steady and reliable supply of wire to the weld.
electrode feeder
The ________ at which the current cycles is the rate at which it makes a full change in direction.
frequency
Electrons flow through the conductor _____.
from negative to positive
How can the end of a tungsten be shaped?
grinding, breaking, re-melting the end, or using chemical compounds
Resistance to the flow of electrons produces.
heat
What two terms do welders often use interchangeably when speaking about welding current?
heat and amperage
_______ is a by-product of the natural gas industry that is removed from natural gas as the gas undergoes separation for purification or refinement.
helium
_____ is the peak current that flow across the arc during the high current pulse. The higher the peak current is the greater the weld penetration
high pulse current
Explain how to measure the wire-fee ipm.
hold the trigger for 6 seconds, measure the length and multiply that by 10
What early advancements made the GTA welding process more effective and reduced costs?
improvements in gas composition and a better understanding of the importance of polarity.
What does adding thorium oxide do for the tungsten electrode?
improves current-carrying capacity, helps with electron emissions, provides a much easier arc start, increases the life
which of the following is True of breaking and remelting tungsten?
it should be broken squarely
THE GTAW gas lens ____
reduce the turbulence in the shielding gas as it leaves the nozzle.
If high frequency is not used, it will be necessary to use the _______ technique to start the arc.
scratch start/ lift arc
A 60% duty cycle means that the machine can be used a total ___ minutes out of every ten minutes at the maximum rated current.
six
The rate of voltage decrease as the amperage increases within the working range is known as _______ .
slope
____ of the electrode results in limited tungsten inclusions in the weld, which are acceptable
slow erosion
Why must the tube of a flowmeter be vertical?
so the ball will flow freely inside the tube
What functions can a remote control provide the welder?
start the weld, increase or decrease the current, and stop the weld
The ______ wire feed system has the advantage of being enclosed in a case.
suit-case style
Why is argons ease of ionization a benefit?
suitable for alternating-current and easier starts
An arc will jump ____.
the closest metal conductor
To change between short-circuiting, axial spray, globular, or buried arc transfer methods, for the most part, all you have to do is make changes in____.
the welding machine's voltage and amperage settings.
Due to its hardness, when hand grinding tungsten it will become hot, and its high ______ means that the heat will be transmitted quickly to your fingers.
thermal conductivity
Why must AC welding power use high frequencies in order to work?
to maintain the arc during DCEP and the stabilize the arc
When the shielding gas flow rate is high, air is drawn into the gas envelope by a _______ effect around the edge of the nozzle.
venturi
How must tub-and ball-type flowmeters be mounted?
vertically
_________is a measure of electric pressure
voltage
_____controls the maximum gap the electrons can jump to form the arc.
voltage
The terms welding cables and _______ mean the same thing.
welding lead
The _______ rate, measure in inches per minute or pounds per hour, is the rate at which the arc consumes the wire.
wire melting
Adding _____has the same effect on the electrode characteristic as thorium, but is not radioactive.
zirconium
GMA welding machines have ____ duty cycle.
100%
Shielding gas used in pulse arc metal transfer on any metal other than steel.
100% argon
in GTAW, the arc temperature is around ______ fahrenheit.
11,000
What is the heat distribution of DCEN welding current?
2/3 on work, 1/3 on tungsten
When the GMAW-S process is properly tuned, what is the approximate rate of its cycling?
20 to 200 times per second
Shielding gas for carbon steel in short circuit
25% CO2, 75 % argon
DCEP concentrates _____ of the heat on the plate, and _____ of the heat on the electrode.
1/3, 2/3
Why must shielding gas hoses not be made from rubber?
Contain oils that can be picked up by the gas, resulting in weld contamination
The GMAW-S process does not produce enough heat to make quality welds in sections much thicker than ______________ unless it is used for the root pass on a grooved weld or to fill gaps in joints.
1/4
AC concentrates about _____ of its welding heat on the work and ______ on the tungsten.
1/2,1/2
The tungsten point angle can be set between a range of ______
10-60
Why must the tip of the tungsten be hot?
As the tungsten electrode become hot, the arc between the electrode and the work will stabilize.
Why does some tungsten erosion occur?
Because of the intense heat from the arc.
What happens to tungsten over time and how do you re-melt it.
Because of the intense heat of the arc, some erosion of the electrode will occur. The desired shape of the electrode can be obtained by grinding, breaking, re-melting the end, or using chemical compounds. The tapered tungsten with a balled end, is made first by grinding or chemically pointing the electrode. To re-melt use DCEP strike and arc on some copper using argon shielding gas and slowly increase the current until a ball starts to form on the tungsten.
Why is the travel and work angle important?
Because of the jetting force of the electrode end
Flowmeters measure the flow rate of a shield gas in _______ units.
CFH or L/min
What materials can be used to make nozzles?
Ceramic such as Alumina or Silicon Nitride (opaque) Fused Quartz (clear)
