Transcript Shielded Metal Arc Welding (SMAW)

Shielded Metal Arc Welding
(SMAW)
What is SMAW?
• SMAW often referred to as “stick” or “manual”
welding.
• Metal rod covered with flux that provides the
shielding to protect the weld.
• Uses constant current power sources.
• Most widely used form of welding in the world.
• Used for fabrication of ships, pressure vessels,
tanks, automobiles, and appliances.
SMAW Safety
• Eye Protection
– Safety Glasses, welding helmet
• Proper Work Clothing
– Jacket, Coveralls, gloves
• Electrical equipment hazard
– Frayed connections, water, protecting yourself
from becoming part of the circuit
SMAW Overview
• SMAW utilizes an arc welding machine to
join 2 pieces of metal together.
• Electric Arc established between flux
covered electrode and base metal.
• Heat from the arc melts metal and mixes
with deposits of electrode.
SMAW Electrical Principles
• When welding SMAW, an electrical circuit
is created.
• Electrical circuit; path taken by electrical
current flowing from one terminal of the
machine, through a conductor to the other
terminal.
• Current; amount of electron flow through
an electrical circuit
• Conductor; any material through which
electricity flows easily.
• Resistance; opposition of the material in a
conductor to the passage of electrical
current causing heat.
• Heat is caused in SMAW by an air/gas gap
between the electrode and base metal
SMAW Electrical Terms Revisited
• Ampere (amp, or A): Unit of measuring
electricity/ electron flow.
• Amperage: Quantity of electricity (amps)
measured.
• Voltage: Electrical pressure that causes
current to flow
Current Flow
• Alternating Current- electrical current
where electrons flow in both positive and
negative values
• Direct Current- electrical current that flows
in only one direction. Polarity refers to the
direction in which electricity is flowing.
– DCEP; Direct Current Electrode Positive
– DCEN; Direct Current Electrode Negative
SMAW Equipment
• Power Supply
– Must maintain constant current with only a
light change in voltage
– Varying voltage and current will result in an
uneven arc that creates spatter and uneven
welds
– Multiple types of power supplies (generators,
transformers, rectifiers, inverters)
SMAW Equipment
• Welding Leads: conduct
current to and from the
work piece.
– Lead with the electrode
holder attached is called
the electrode lead
– Lead with the workpiece
connector attached is
called the workpiece lead.
Commonly but incorrectly
referred to as the ground
clamp.
SMAW Equipment
• Electrode Holders
– Handle-like tool that
holds the electrode
during welding.
– Receives amperage
and directs it through
the electrode to form
an arc.
– Should be well
insulated and free
from defect.
SMAW Equipment
• Work Piece
Connection
– Must be connected to
work piece or bench to
complete electrical
circuit.
– Connections are made
to be removable for
easy mobility
SMAW Equipment
• Electrodes
– Consists of internal
metal core, and an
outer coating called
flux.
– Metal core melts into
molten base metal.
– Flux is turned into gas
shield as it burns
away.
– Several types and
sizes of electrodes.
SMAW Equipment
• Welding Helmet
– Used to filter the intense
UV light produced from the
arc welding process.
– Needs to be at least a #10
shade
– Auto shade helmets can be
set to a particular shade
number and don’t need to
manually change the filter
lens
SMAW Equipment
• Clothing
– Pants and Jackets
need to be thick to
help protect skin and
body from the heat
and UV light produced
from welding
– Gloves need to be
thick and insulated
– Arms and legs must
be covered at all times
while using SMAW
Electrodes
•
•
Electrodes are coated metal wire with the
same composition as the base metal to
be welded.
5 main classification groups
1.
2.
3.
4.
5.
Mild steel
High carbon
Special alloy steel
Cast iron
Nonferrous
Electrodes
•
•
Flux coating contains various substances
Components of flux serve multiple
purposes
1. Cleansing and deoxidizing agent in molten
crater
2. Release Carbon Dioxide to protect molten
metal
3. Form slag over deposited weld bead
4. Provide easier arc starting, stabilization,
reduce spatter
5. Improve weld penetration
Electrodes
• Electrode Identification-AWS standardized
numbering system
• Example= E6013
• What does this number mean?
E6013
• E= Electric Arc Welding
• 60 (first 2 digits)=Tensile strength in
1000/lbs
• 1 (third digit)= Welding Position
• 3 (fourth digit)= Type of flux/ welding
current