Sem 1 Midterm Review

Which of the following is true of grinding tungsten electrodes?

If the grinder is used for metals other than tungsten, 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 penetration and reinforcement and is used on automated welding.

____ is a series of ridges cut into the groove.

Knurling

The best material to use for special protective clothing is ____.

Leather

Which of the following is true of shielded metal arc welding?

Metal as thin as 1/16 inch to several feet thick can be welded using the same machine.

____ is formed when ultraviolet radiation decomposes chlorinated hydrocarbon.

Phosgene

A 60% duty cycle means that the machine can be used a total of ____ minutes out of every ten minutes at the maximum rated current.

Six

Which of the following is true of erosion of the tungsten electrode?

Slow erosion results in limited tungsten inclusions in the weld.

Which of the following is true of wire electrodes?

Some wire electrodes require storage in an electric rod oven.

In alternators the welding current is produced on the ____.

Stator

Mixtures of argon with less than ____ percent carbon dioxide may not have enough arc voltage to give desired results.

Ten

Which of the following is true of axial spray metal transfer?

There are hundreds of drops per second crossing from the wire to the base metal.

A disadvantage of the perpendicular technique is limited visibility of the weld.

True

A steep angle between the torch and the work may draw in air.

True

A strong alkaline can be used to chemically clean and point tungsten.

True

All three types of welding current can be used for GTA welding.

True

Slight changes in the welding gun angle can be used to control the weld as the groove spacing changes.

True

Sometimes the shielding gas is referred to as the shielding medium.

True

Tungsten erosion can be limited by using a water-cooled torch.

True

Tungsten is hard but brittle, and has a low impact strength.

True

Welding and cutting lead-bearing alloys or metals whose surfaces have been painted with lead-based paint can generate lead oxide fumes.

True

____ fire extinguishers are used for combustible metals such as zinc and magnesium.

Type D

____ can cause an arc to move during a weld.

Uneven flux lines

____ controls the maximum gap the electrons can jump to form the arc.

Voltage

Which of the following is true of DCEN?

With DCEN, a pointed tip concentrates the arc.

The amount of heat produced by a welding arc is determined by the ____.

amperage

The shielded metal arc welding machine's voltage output ____ as its current ____.

decreases, increases

Electrons flow through a conductor ____.

from negative to positive

In the pulsed-arc metal transfer current cycle, ____ is the peak current that flows across the arc during the high current pulse.

high pulse current

MAG is short for ____.

metal active gas welding

In FCAW, atmospheric shielding is ____.

provided by flux sealed within the tubular electrode, but extra shielding may be supplied through a nozzle as in GMAW

In a standard welding transformer, the size of the iron core is determined by ____.

the length of time it takes for the magnetic field to build up and collapse

In FCAW ____ % of the electrode is used.

Nearly 100

____ is a gas that is produced by the ultraviolet radiation in the air in the vicinity of welding operations.

Ozone

Which of the following is true of GMA spot welding?

The burning back of the thin material allows the thicker metal to be melted.

Any cold liquid you drink can be poured on a first or second degree burn.

True

Adding ____ has the same effect on the electrode characteristic as thorium, but is not radioactive.

zirconium

In GTAW, the arc temperature is around ____ degrees Fahrenheit.

11,000

FCA welding deposition rates of more than ____ lb./hr. of weld metal are possible.

25

____ all help remove oxides and/or nitrides in the weld.

Aluminum, silicon, and titanium

____ controls the size of the arc.

Amperage

____ is relatively easy to ionize and thus is suitable for alternating-current applications and easier starts.

Argon

Which of the following is a carbide former?

Chromium

An advantage of FCAW is that it is confined to ferrous metals and nickel-based alloys.

False

As much as 20% of the heat generated by a GTA welding torch does not enter the weld.

False

Both earmuffs and earplugs protect the outer ear from burns.

False

DCEP has the lowest heat concentration on the electrode tip.

False

FCAW electrodes have a mineral-based flux that becomes liquid at high temperatures.

False

FCAW represented about 20% of the total amount of welding done in 2005.

False

Fused quartz nozzles are no more expensive than ceramic nozzles, but are more easily broken.

False

Hot-rolled steel has a thin copper layer which is formed during the rolling process.

False

In semiautomatic or automatic processes, the welder is required to work harder because of the greater demands on travel speed and current.

False

To treat a third degree burn, apply ointments or antibiotic cream.

False

When first introduced, SMAW was immediately accepted because it was more productive than GTAW and produced higher quality welds than GMAW.

False

When the GTAW process was first developed, argon was the primary shielding gas used.

False

When using extension cords on portable power tools, the size of the conductors must be small enough to enable a drop in voltage.

False

Which of the following is a similarity between FCAW and GMAW?

Higher electrode feed speeds produce higher currents.

Scrap metal and electrode stubs are difficult and costly to recycle.

False

The flux within the electrode will remove or control weld quality problems caused by surface contaminators.

False

The heat produced during GMA welding is sufficient to force 100% penetration consistently, making it ideal for industrial applications.

False

The lime-based flux is acidic.

False

The lower the density of a gas, the lower the flow rate required for equal arc protection.

False

The shielding gas flow rate should be as high as possible.

False

The welding area should be ventilated and forced ventilation is best, but natural ventilation is sometimes required.

False

Which of the following is an inert gas?

Helium

____ respirators are air-purifying respirators that use a blower to force the ambient air through air-purifying elements to the inlet covering.

Powered air-purifying

The heat produced during axial spray welding using large diameter wire or high current may be intense enough to shatter the filter lens in a welding helmet.

True

The rutile-based flux is acidic.

True

Too much visible light can cause temporary night blindness.

True

Wire should not be discarded on the floor because it can work its way into a filter screen on the welding power source.

True

A(n) ____ produces AC, and a(n) ____ produces DC.

alternator, generator

In the flux classification system, the letter "G" is used to indicate ____.

an unspecified classification

In generators the welding current is produced on the ____.

armature

Atmospheric contamination of molten weld metal occurs ____.

as it travels across the arc gap and within the pool before it solidifies

General work clothing should ____.

be tightly woven and a dark color

A ____ is the symbol for a Type C fire extinguisher.

blue circle

The shielding gas used on carbon steel is ____.

carbon dioxide, or a mixture of carbon dioxide and argon

The correct flow rate of a shielding gas can be set by ____.

checking welding guides

Resistance to the flow of electrons produces ____.

heat

Open circuit voltage ____.

is the voltage at the electrode before striking an arc

The major classifications of welding machines are ____.

multiple coil, movable coil, movable core, and inverter

The ____ machine allows the selection of different current settings by tapping into the secondary coil at a different turn value.

multiple-coil

Stored oxygen and fuel gas cylinders ____.

must be separated by 20 feet

A ____ gap may require ____.

narrow, more penetration

Welding cables made of aluminum wire must be ____ would be required for copper.

one size larger than

The base of a ladder should be set out a distance equal to ____ the height to the point of support.

one-fourth of

The heat produced by a rectifier ____.

reduces the power efficiency of the welding machine

A transformer with more turns of wire in the primary winding than in the secondary winding is known as a ____.

step-down transformer

To test a grinding stone for cracks ____.

tap the stone in four places and listen for a ring

In general the current-carrying capacity at DCEN is about ____ than that at DCEP.

ten times greater

The improved electron emission of the ____ allows it to carry approximately 20% more current than pure tungsten.

thoriated tungsten

The temperature of a welding arc is dependent on the ____, arc length, and atmosphere.

voltage

The most popular electrode diameters range from ____ to ____.

.035 inch, 3/32 inch

DCEP concentrates ____ of the arc heat on the plate, and ____ of the heat on the electrode.

1/3, 2/3

Burns can be caused by ultraviolet light rays.

True

Constant-potential and voltage are terms that have the same meaning.

True

Damage to your hearing caused by high sound levels is permanent and may not be detected until later in life.

True

In the beginning, the GMAW process was used to weld aluminum using argon gas for shielding.

True

The FCA welding power supply is the same type that is required for GMAW.

True

The amount of reactive gas required to produce the desired effects is quite small.

True