TITLE: LW1: SHIELDED METAL ARC-WELDING (SMAW) 1.0 INTRODUCTION 1.1 THEORY 1.1.1 Definition Shielded metal arc-welding (SMAW) is one of the oldest, simplest and most versatile joining process. Nearly half of all industrial and maintenance welding currently is performed by this process. The electric arc is generated by touching the tip of a coated electrode against workpiece and withdrawing it quickly to a distance sufficient to maintain the arc. The heat generated melts a portion of the electrode tip, its coating and the base metal in the immediate arc area. The Stick welding power source provides constant current (CC) and may be either alternating current (AC) or direct current (DC), depending on the electrode being used. The best welding characteristics are usually obtained using DC power sources. 1
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TITLE: LW1: SHIELDED METAL ARC-WELDING (SMAW)
1.0 INTRODUCTION
1.1 THEORY
1.1.1 Definition
Shielded metal arc-welding (SMAW) is one of the oldest, simplest
and most versatile joining process.
Nearly half of all industrial and maintenance welding currently is
performed by this process.
The electric arc is generated by touching the tip of a coated
electrode against workpiece and withdrawing it quickly to a
distance sufficient to maintain the arc.
The heat generated melts a portion of the electrode tip, its coating
and the base metal in the immediate arc area.
The Stick welding power source provides constant current (CC)
and may be either alternating current (AC) or direct current (DC),
depending on the electrode being used. The best welding
characteristics are usually obtained using DC power sources.
The electrode coating deoxidizes the weld area provides a shielding
gas to protect it from oxygen in the environment.
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1.1.2 Advantages and Limitations
Advantages Limitations1. Ability to weld in all
position.1. High potential for weld contamination.
2. Easy in welding many different metals & alloys.
2. Frequent interruptions due to electrode length.
3. Ability to weld thin & very thick metals.
3. Need to remove spatter, smoke & Slag.
4. Very portable and good for field work.
4. Unsuitability for very thin material.
5. Good choice for repair work. 5. Poor choice for aluminum & bronze. 6. Low cost, low maintenance
equipment.6. Electrode requires special care to Prevent moisture pickup.
7. Good arc visibility.8. Fairly tolerant of different
environment.9. Good accessibility in
restricted areas.
1.2 OBJECTIVES
To perform on of the welding techniques that has learnt in Chapter 2.
To use the skill to do the welding, used the knowledge and understanding of
the theories, and also techniques discussed within the topics into the practical
application.
To analyze the outcome from the practical task that have been doing and
write the report.
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2.0 RESOURCE & FACILITIES
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POWER SUPPLY
Two types of supply: Alternating current (AC) welders. Direct current (DC) welder.
Wider variety of electrode available. Better for welding thin metals. DC straight polarity (DC-EP) has
electrode negative and workpiece positive. Produce high electrode melting rate.
o DC reverse polarity (DC-EP) has electrode
WORKTABLE
Place where all welding activity is completed. The workpiece will be placed on the table so
that welding process can be done.
ELECTRODE HOLDER
Grips the electrode.
Handles and clamp are insulated.
Grooves in the clamp enable changing the
position of electrode.
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PLIER
Hand tool used to hold objects firmly or for cutting and bending tough materials.
WORKPIECE CLAMP
Complete the electric circuit from power supply, through the electrode across the arc through the workpiece and back to the power supply.
Should be firmly attached to workpiece or worktable.
PROTECTIVE SHIELD
Provides full facial protection from: Sparks and flying metals. Intense light from arc. Ultra-violet light. Infrared red.
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WIRE BRUSH & HAMMER
Wire brush is used for cleaning rust and
removing paint.
It is also used to clean surfaces and to
create a better conductive area for
attaching electrical connections.
GLOVE
To protect hand from: Spark and flying metals. Hot metal during and after