Transcript Unit 7 review

NCCER Unit 7
 SMAW is known as stick welding as we know.
 SMAW can use either ________ current (AC) or _________ current (DC)
 This unit gives an overview of the different types of equipment used for SMAW
welding, characteristics of SMAW welding, and accessories needed for SMAW
welding.
 Welding machines use _________ power. Most operate on 110, 120, ____, or
_____volt levels.
 Regardless of voltage levels, be aware of any electrical power source associated
with your welding machine.
 Use rigging or lifting devices whenever possible.
 Get help if you must move something heavy by hand.
 Always use __________ when hoisting heavy objects that tend to spin or swing.
 Can be either AC or DC current. Current is the flow of an electrical charge from
one point to another. One of those points must be the grounded earth and the other
can be the metal or whatever we are welding.
 SMAW power supplies are designed to produce an output that has a nearly
___________________.
 If the electrode tip is touched and held against the workpiece instead of allowing
for a gap between the two,
____________________________________________________________________________
______________________________________-.
 AC power is most commonly used in SMAW welding. Alternates between positive
and negative charges and looks like a wave on a graph.
 The top part of the wave is a positive charge and the bottom part is a negative
charge.
 The standard frequency in the United States is set at ___________________.
 Direct current has no frequency. It does not travel from positive to negative so the
waveform resembles a straight line on a graph.
 ____________ only applies to DC current. It is determined by the way the welding
leads are connected either to the welding machine or to the workpiece.
 ____________ is a measurement of the electrical current flowing in a circuit. Its unit
of measurement is the ampere (amp, or A)
 Number of amps produced by the welding machine determine the amount of heat available to
melt the work and the electrode.
 Welding machines have specific classifications and rated rated capacities.
 SMAW welding machines are classified by the type of welding current they
produce: AC, DC, or AC/DC.
 The primary current required for welding machines can be _____V or _____V
single phase or _____V three phase.
 Transformer welding machines produce AC current.
 They use a voltage step down transformer , which converts
____________________________________________________________________________
__________________________________.
 A rectifier is a device that converts AC current to DC current.
 Transformer-rectifier type welding machines use a transformer to reduce the primary
voltage to welding voltage and then rectifies the current to change it from AC to DC
current.
 The size of a welding machine is determined by the ____________ of the machine
and the _____________.
 Duty cycles of a welding machine is based on a 10 minute period. It’s a percentage
based on how long the machine can run in those 10 minutes without overheating.
 Most typical machines have a 60 percent duty cycle.
 If no welding is required for ______ minutes, stop the machine or engine by turning
off the ignition switch
 Cables that carry the current are designed for strength and _____________.
 The conductors inside the cable are made of fine strands of _______________
surrounded by a rubber cord.
 When selecting welding cable size, the amperage load and and the distance to
travel must be considered.
 The longer the distance that current must travel, the _______________the size of the cable
needs to be.
 Welding cables must be strung overhead on a job site to eliminate tripping
hazards and the risk of traffic damaging them.
 When stringing welding cable overhead or between floors, use __________ to tie
off the cables.
 Engine driven welding machines require regular preventative maintenance to
keep the equipment operating properly.
 Most engine driven welders have a preventative maintenance schedule based on
the ________________________.
HAND TOOLS
 It is very important that base metals are cleaned before welding.
 Also, before any additional weld beads can be applied, the previous weld beads
must be cleaned of any slag to ensure a quality weld.
 Some common hand tools used in the SMAW welding process include __________
_____________________________________.
 Weld slag hammers and needle scalers are_______________________.
 They are used to clean surfaces and remove slag from cuts and welds.
 Pneumatically powered simply means powered by ________.