acorn pre employment basic metal arc welding shielded metal arc welding terminology standard...

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

Copyright © 2014 CWB Group Industry Services

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



SMAW Principles

The shielded metal arc welding process.FIG. 1



SMAW Principles

SMAW Equipment and set‐up.FIG. 2



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



Power Sources

Constant current power source slope.FIG. 3



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



Arc Force Control

Arc force control.FIG. 5



Arc Starting Hot Start

FIG. 6 Arc Starting – “Hot Start”



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



This is a sample instructor presentation, some pages have been removed

acorn pre employment basic metal arc welding shielded metal arc welding terminology standard...

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