SMAW Equipment
(Shielded Metal Arc Welding- commonly
called “stick welding”, or “arc welding”)
How a “Buzz Box” works:
Terms and Theory
• Typical SMAW machine
(arc welder, buzz box)
Electrons- what we need for Electricity!
Electrons are
negative.
And remember… opposites attract.
Electrons- defined
Electron- electrons are negatively charged particles that move through
a conductor when current is flowing. Because electrons carry a
negative charge, electron theory states that they are attracted by
positively charged bodies and therefore move from negative to positive.
Circuits- defined
Circuit- Any system of conductors that is designed to
complete the path of an electric current is called a
circuit. Current flows in the conductor when voltage is
applied to it.
Circuits – power via wall outlet
Current Flow- Measured in Amperes (Amps)
Current flow is the movement of electrons.
The greater the number of electrons, the higher the measure of
Amps.
Amperage- defined
Amperage (heat setting) - the strength of a current of electricity
measured in amperes. This is the electrical property that causes
the electrode, the parent metal, or both, to be melted.
High Amps= quick metal deposit and deep penetration
Low Amps = slower deposit rate and less penetration
Voltage- defined
Voltage- Voltage is the electrical pressure or force that causes
current to flow in a conductor, or to cross a gap, as occurs in
welding. Voltage is often called EMF, which stands for electromotive
force. (Battery example)
Voltage in arc welding is responsible for the following:
- Starting the arc
- Maintaining the arc
- Puddle fluidity and puddle flow (the amount of voltage is
determined by the type and size of electrode being used)
Voltage-Amperage relationship..
Voltage pushes Amperage through resistors
(Ohms Law)
Arc- In welding, an arc is created when there is enough
amperage and voltage available at the electrode tip to
overcome the natural resistance to the flow of electricity.
This resistance is usually caused by the air gap between the
electrode and the work.
Resistance- defined
Resistance- Resistance is the property of an electrical
conductor to oppose the flow of current, causing electrical
energy to be turned into heat. Resistance is measured in
ohms.
The air gap offers resistance to current flow. It is this
resistance to the flow of current across the arc that creates
the heat needed for welding.
Alternating Current- Defined
Alternating Current (AC) - Current that flows in one
direction during any half cycle, then reverses and flows in
the opposite direction during the next half cycle. The rate
at which this alternating occurs is measured as cycles per
second (60 cycle AC is common).
Frequency- Frequency relates to the speed at which
alternating current changes its direction of flow. A high
frequency current is used in some welding processes to
allow for non-touch arc starting or to provide a path for
the weld current to follow.
Direct Current (DC)
Direct Current (DC) - Electric current that flows in one direction only and has
either a positive or negative value. There is no change of direction as there is
with AC. The electron theory states that current flows from negative to
positive since that is the direction that electrons flow in.
Polarity
Straight Polarity- In a SMAW DC welding circuit, straight polarity
occurs when the electrode cable is connected to the negative
terminal of the welding machine, thus making the electrode
negative, in relation to the work-piece.
Reverse Polarity- In a SMAW DC welding circuit, reverse
polarity occurs when the electrode cable is connected to the
positive terminal of the welding machine, thus making the
electrode positive, in relation to the work-piece.
SMAW Welding Machine (Buzz Box)
Components
Primary Coil- The primary coil on a welding transformer takes power directly
from the AC input power line. The current flowing into the primary coil
causes a magnetic field to form.
Secondary Coil- the secondary coil is located on the main transformer core
of an AC welding machine. The energy created in the magnetic field by the
primary coil is induced into the secondary coil.
Inductance- Inductance is the ability of a conductor to transfer
current onto a neighboring body without physical contact. For
example, in a transformer welder, current is brought to the
primary coil where a magnetic field is created due to the iron
core. The magnetic field induces current flow into the
secondary coil without physical contact.
Magnetic Field- A magnetic field is created when current is
forced to flow through a coil that is wrapped around an iron
core. The strength of the magnetic field determines the power
capacity of welding machines.
Movable shunt in relation to primary and secondary coils..
Core- The core is the magnetic link between the primary and the secondary
coils of a welding transformer. The core can be moved into or out of the coil
as a method of current control. This type of current control is called movable
shunt. A movable shunt means that the core can be moved into different
positions thus influencing the magnetic link between the primary and
secondary coils. The shunt is usually moved mechanically by an external
hand crank that controls its movement on a slide assembly. This allows for
any setting between minimum and maximum of the machine’s output
potential.
Duty Cycle- All welding machines are rated based on maximum
output over a ten-minute time period. This rating is expressed as
a percentage of time that the machine can run at maximum
rated output current before it must be allowed to cool down.
Exceeding duty cycle ratings can damage or ruin a welding power
source.