Post on 06-Mar-2018
ACORN Pre‐employmentWP1.1Basic Shielded Metal Arc Welding
After completing this learning unit you should be able to:
Describe the principles of the process and the equipment used
Explain the functions of the electrode wire, coating and slag
Identify electrodes and the materials used in the coating
Explain the classification system for welding electrodes
Identify the usability characteristics of different types of electrodes
Describe the requirements for storage and conditioning of electrodes
Outline the advantages, limitations and applications of the process
Identify the welding process variables controlling the process
Describe the influence of the process variables on weld quality
Objectives
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WP1.1Basic Shielded Metal Arc Welding
TerminologyStandard terminology:
SMAW – Shielded Metal Arc Welding(CSA, AWS, ASME)
MMAW ‐Manual Metal Arc Welding
Non‐standard terminology:
Manual Welding
“Stick” (electrode) welding
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WP1.1Basic Shielded Metal Arc Welding
SMAW Principles
The shielded metal arc welding process.FIG. 1
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WP1.1Basic Shielded Metal Arc Welding
SMAW Principles
SMAW Equipment and set‐up.FIG. 2
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WP1.1Basic Shielded Metal Arc Welding
Power Sources Power output is constant current (CC) type – it has a drooping volt‐amp curve
With a change in the arc voltage, the accompanying change in current and therefore melt‐off rate are small
Power sources may have a different slope
Some machines allow adjustment
Adjustment of the slope allows the welder to better control the weld pool and penetration for applications such as:
Out‐of‐ position welding Root passes in a pipe with varying gap
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WP1.1Basic Shielded Metal Arc Welding
Power Sources
Constant current power source slope.FIG. 3
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WP1.1Basic Shielded Metal Arc Welding
Power Sources Direct current (DC) or Alternating
current (AC) Transformer or alternator type
used for AC Transformer/rectifier or motor
generator used for DC Some power sources can be used
for DC and AC Inverters are becoming popular
Typical power sources.FIG. 4
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WP1.1Basic Shielded Metal Arc Welding
Arc Force Control
Arc force control.FIG. 5
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WP1.1Basic Shielded Metal Arc Welding
Arc Starting Hot Start
FIG. 6 Arc Starting – “Hot Start”
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WP1.1Basic Shielded Metal Arc Welding
Depending on the size and type of electrode, the current can be AC or DC
Open circuit voltage (OCV): 50 ‐70V for AC
Arc voltage: 16 ‐ 40 volts ‐depends on the arc length
Welding current: 30 ‐ 550 amps.
Current and Voltage
Current and polarity.FIG. 7
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WP1.1Basic Shielded Metal Arc Welding
This is a sample instructor presentation, some pages have been removed