transcript
- Slide 1
- Unit Objective: SWBAT Identify and explain SMAW equipment.
- Slide 2
- Shielded metal arc welding (SMAW) is often referred to as stick
welding. This welding process can use either alternating current
(AC) or direct current (DC). The electrodes (rods) that are used
have a coating called flux. During the welding process the flux
forms a gas shield that protects the weld puddle from atmospheric
contamination. SMAW is currently used in a wide variety of industry
applications.
- Slide 3
- What does SMAW stand for? A.) Shielded Metal Arc Welding B.)
Strong Metal Attaching Weld C.) Shielded Material Air Welding D.)
Safe Metal Arc Welding
- Slide 4
- Welding can be a dangerous profession, not so much because of
the welding itself, but because of the work environment where the
work is often performed. SMAW has its own safety precautions that
need to be taken when it is used. UV Radiation Hot metal and slag
Flying sparks Smoke and fumes Electrical hazards PPE for SMAW
includes but is not limited to: Safety glasses Welding helmets
shade 10-12 Gloves Welding Jacket
- Slide 5
- ARC Welding machines use electrical power. Most machines
operate on 110V, 120V, 240V, or 480V power levels. Regardless of
the voltage level, it is important to be aware of the electrical
power source used by your machine. Another concern wile using
electricity is moisture, especially water. Electricity, water, and
the human body are a dangerous mix. Make sure that your welding
cables are in good condition and that your work piece clamp is
properly installed.
- Slide 6
- Welding machines operate on which voltages? A.) 110V B.) 240V
C.) 480V D.) All of the above
- Slide 7
- When the term current is used as a noun, in means a flow or a
stream. In electrical terms current is the flow of electricity from
one point to another. One point being a ground and the other being
a source of electricity. In welding there must be current flow
between the work piece and the welding machine. The arc that is
produced during SMAW is an electrical current that jumps the gap
from the tip of the electrode to the surface of the work, as long
as the work piece lead from the machine is attached to the work. If
the electrode is held against the work piece instead of allowing
for a gap the electricity will pass directly from the electrode to
the work without creating an arc. No welding can take place with
out an arc across the gap to create the heat necessary to melt the
electrode and the work piece.
- Slide 8
- There are two types of welding current used. Alternating
Current (AC) Direct Current (DC)
- Slide 9
- The most commonly used form for SMAW is Direct Current (DC). In
which the current always flows in one direction, from negative to
positive. With DC we have polarity. Polarity is determined by the
way the welding leads are connected to the machine and work. By
swapping the electrode and work leads we can change the polarity.
SMAW is most often done with Direct Current Electrode Negative
(DCEN), but can also be used with Direct Current Electrode Positive
(DCEP).
- Slide 10
- The other and more seldom used is Alternating Current (AC). In
AC the current still flows from negative to positive, but the
positive and negative poles alternate back and forth. A cycle is
when the pole switches from positive to negative and back to
positive. The number of cycles per second is called the frequency
and is measured in Hertz. The frequency of AC is determined by the
generator producing the current. In the United States the standard
frequency of AC is 60 Hertz.
- Slide 11
- What are the two types of welding current? A.) Amperage and
Voltage B.) Negative and Positive C.) Direct and Alternating D.)
Polarity and Frequency
- Slide 12
- If the tip of the electrode is held directly against the work
piece, A.) Welding will take place. B.) No welding will take place.
C.) The arc will be twice as hot. D.) The electrode will not get
hot.
- Slide 13
- When the SMAW machine is set to DCEN, the current flows A.)
From the work to the electrode. B.) From the electrode to the work.
C.) Both to and from the electrode. D.) Depends on the electrode
used.
- Slide 14
- SMAW machines can come in many different shapes and sizes. The
size of a welding machine is determined by its duty cycle. The duty
cycle of a welding machine is based on its ability to produce its
rated amperage over a 10 minute period without over heating.
Example, a 200amp machine that has a 60% duty cycle can produce
200amps for 6 minutes out of 10 without over heating. Running a
machine above its rated amperage will reduce its duty cycle.
- Slide 15
- Work piece clamps often called ground clamps establish the
connection between the work and the work piece lead that runs to
the machine. Work piece clamps are selected based on the amount of
current it can carry without overheating. Electrode holders grasp
the electrode and provide electrical contact between the electrode
and the welding cable. Electrode holders are also rated and
selected based on the amount of current it can carry without
overheating.
- Slide 16
- What does Duty Cycle refer to? A.) The % of time in a 24 hr
period that a machine can run at rated output. B.) The % of time in
a 10 min period a machine can run at rated output. C.) Length of
time a machine can work doing the work it was designed for. D.)
Life cycle of the machine before it needs to be serviced.
- Slide 17
- SMAW cannot take place without electrodes, often called sticks.
SMAW electrodes have a metal wire core coated with a flux. The wire
core conducts the welding current from the electrode holder to the
work. The arc at the end of the electrode melts the wire core, the
flux coating, and the base metal at temperatures exceeding 6,000 o
F.
- Slide 18
- The flux coating on the electrodes creates a slag coating that
must be cleaned from the weld. Chipping hammers, hand files, and
wire brushes are a few of the hand tools that can be used for post
weld cleaning.
- Slide 19
- SMAW is often referred to as stick welding. SMAW remains one of
the most widely used forms of welding in the industry because of
its simplicity and a relatively low cost. SMAW is the basis on
which all other welding processes have been developed.
Understanding the SMAW process and its techniques is crucial for
achieving success with other welding processes.