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SAMPLE_Topic1_247358
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Topic 1.
Welding Process Training Series
Introduction To Welding
SAFETY
Standard for Fire Prevention During Welding, Cutting, and Other Hot
Work, NFPA Standard 51B, from National Fire Protection Association,
Quincy, MA 02269 (Phone: 1-800-344-3555, website: www.nfpa.org.)
OSHA, Occupational Safety and Health Standards for General Industry, Title 29, Code of Federal Regulations (CFR), Part 1910, Subpart
Q, and Part 1926, Subpart J, from U.S. Government Printing Office, Superintendent of Documents, P.O. Box 371954, Pittsburgh,
PA 15250-7954 (Phone: 1-866-512-1800) (There are 10 OSHA Regional Offices—phone for Region 5, Chicago, is 312-353-2220,
website: www.osha.gov).
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As in all occupations, safety is paramount. Because there are
numerous safety codes and regulations in place, we recommend
that you always read all labels and the Owner’s Manual carefully
before installing, operating, or servicing the unit. Read the safety
information at the beginning of the manual and in each section.
Also read and follow all applicable safety standards, especially
ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes.
Safe Practice For Occupational And Educational Eye And Face Protection, ANSI Standard Z87.1, from American National Standards Institute, 25 West 43rd Street, New York, NY 10036 (Phone: 212-642-4900,
website: www.ansi.org).
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Arc
Welding
and Cutting
the
Safe Way!
Safety in Welding, Cutting, and Allied Processes, CSA Standard
W117.2, from Canadian Standards Association, Standards Sales, 5060
Spectrum Way, Suite 100, Ontario, Canada L4W 5NS (Phone: 800-4636727, website: www.csa-international.org).
ANSI Z49.1:, Safety in Welding, Cutting, and Allied Processes is
available as a free download from the American Welding Society
at: http://www.aws.org
Towing a Trailer − Being Equipped for Safety, Publication from U.S. Department of Transportation, National Highway Traffic Safety Administration, 400 Seventh Street, SW, Washington, D.C. 20590
U.S. Consumer Product Safety Commission (CPSC), 4330 East
West Highway, Bethesda, MD 20814 (Phone: 301-504-7923,
website: www.cpsc.gov).
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Here is a list of additional safety standards and where to get
them.
Booklet, TLVs, Threshold Limit Values, from American Conference of Governmental Industrial Hygienists (ACGIH), 1330 Kemper Meadow Drive, Cincinnati, OH 45240 (Phone: 513−742−3355,
website: www.acgih.org).
Safe Practices for the Preparation of Containers and Piping for Welding and Cutting, American Welding Society Standard AWS F4.1, from
Global Engineering Documents (Phone: 1-877-413-5184, website:
www.global.ihs.com).
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National Electrical Code, NFPA Standard 70, from National Fire Protection Association, Quincy, MA 02269 (Phone: 1-800-344-3555, website:
www.nfpa.org and www. sparky.org).
Applications Manual for the Revised NIOSH Lifting Equation, The
National Institute for Occupational Safety and Health (NIOSH), 1600
Clifton Rd, Atlanta, GA 30333 (Phone: 1-800-232-4636, website:
www.cdc.gov/NIOSH).
Safe Handling of Compressed Gases in Cylinders, CGA Pamphlet P-1,
from Compressed Gas Association, 4221 Walney Road, 5th Floor,
Chantilly, VA 20151 (Phone: 703-788-2700, website:www.cganet.com).
Prepared by the Miller Electric Mfg. Co. Training Department.
©2014 Miller Electric Mfg. Co.
The contents of this publication may not be reproduced without permission of Miller Electric Mfg. Co. , Appleton Wisconsin, U.S.A.
WARNING
This document contains general information about the topics discussed herein. This document is not an application manual and does not contain a
complete statement of all factors pertaining to those topics.
The installation, operation, and maintenance of arc welding equipment and the employment of procedures described in this document should be conducted only by qualified persons in accordance with applicable codes, safe practices, and manufacturer’s instructions.
Always be certain that work areas are clean and safe and that proper ventilation is used. Misuse of equipment and failure to observe applicable codes and
safe practices can result in serious personal injury and property damage.
Introduction To Welding
Welcome to the Welding Process and Filler Metals Training
Series. This training series was developed for the purpose of
providing a basic set of educational materials that can be used
individually or in a classroom setting.
The topics covered in the series are:
Welding Processes
• Topic 1. Introduction To Welding
• Topic 3. Basic Electricity For Welding
• Topic 4. Welding Power Source Design
1
Methods of Arc Welding
1
Electrical Terms for Welding
2
Mechanical Fastening��������������������������������������������������1
Adhesive Bonding ������������������������������������������������������1
Welding��������������������������������������������������������������������1
Semiautomatic Welding����������������������������������������������2
Automatic Welding������������������������������������������������������2
Robotic Welding (Programmable Automation) ����� 2
Primary Voltage����������������������������������������������������������2
Welding Current Types������������������������������������������������3
Types of Power Sources ����������������������������������������������4
• Topic 6. Shielded Metal Arc Welding
• Topic 7. Gas Tungsten Arc Welding
• Topic 8. Gas Metal Arc Welding
• Topic 9. Flux Cored Arc Welding
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• Topic 11. Troubleshooting Welding Processes
• Topic 12.Submerged Arc Welding
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• Topic A. Introduction To Metals
• Topic B. Tubular Wires
• Topic C. Low Alloy Steel
• Topic D. Stainless Steel
• Topic E. Aluminum
• Topic F. Hard Surfacing
Please note, this series was not developed to teach the skill of
welding or cutting, but rather to provide a foundation of general
knowledge about the various processes and related topics.
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Shielded Metal Arc Welding (SMAW)����������������������������5
SMAW Equipment�������������������������������������������������������5
SMAW Filler Metal and Electrodes��������������������������������6
Gas Metal Arc Welding (GMAW)���������������������������������� 10
Flux Cored Arc Welding (FCAW)���������������������������������� 14
Submerged Arc Welding (SAW)���������������������������������� 15
Welding Joint Types�������������������������������������������������� 17
Edge Joints�������������������������������������������������������������� 18
Butt Joints���������������������������������������������������������������� 18
Lap Joints���������������������������������������������������������������� 19
Corner Joints������������������������������������������������������������ 19
T-Joints ������������������������������������������������������������������ 19
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• Topic 5. Engine Driven Power Sources
Filler Metals
Material Joining Processes
Electrical Arc Welding Processes
• Topic 2. Welding Safety
• Topic 10. Metal Cutting
Table of Contents
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Welding Process and Filler Metals
Training Series:
Weld Types and Positions 20
Fillet Welds�������������������������������������������������������������� 20
Groove Welds���������������������������������������������������������� 20
Weld Positions �������������������������������������������������������� 20
Welding Symbols
21
Eight Factors to Consider When Selecting Filler
23
Metal or Electrodes
Welding Position������������������������������������������������������ 23
Welding Current�������������������������������������������������������� 23
Joint Design and Fit-up���������������������������������������������� 24
Thickness And Shape of Base Metal���������������������������� 24
Service Condition And/or Specifications���������������������� 24
Production Efficiency And Job Conditions �������������������� 24
Preparation for Arc Welding
Arc Welding Markets
24
25
Terms and Definitions
26
Home and Hobby������������������������������������������������������ 25
Farm and Ranch�������������������������������������������������������� 25
Fabrication�������������������������������������������������������������� 25
Maintenance and Repair�������������������������������������������� 25
Education���������������������������������������������������������������� 25
Construction������������������������������������������������������������ 25
Manufacturing���������������������������������������������������������� 25
Automotive Repair���������������������������������������������������� 25
Many products made today by manufacturing and construction companies require some type of joining process be used in
the production of that product. There are three main categories
of material joining processes; mechanical fastening, adhesive
bonding, and welding.
Operation
Joining
Method
Mechanical
Fastening
Materials
Joining
Welding
Figure 1 – Material Joining Processes
Mechanical Fastening
The term Arc Welding (AW) is defined by the American Welding
Society (AWS) as a group of welding processes that produces
coalescence of work pieces by heating them with an arc. The
processes are used with or without filler metal.
The heat needed for welding is created by establishing an electric arc between an electrode and the metal to be welded. The
type of current used may be either direct current (DC) or alternating current (AC).
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Mechanical fastening joins two materials together by using a clamping
force. Screws, bolts, nails, and rivets
are examples of different types of
mechanical fasteners. This method
allows for the materials to be disassembled if necessary.
There are as many as 94 different
types of welding processes recognized by the AWS that use different sources of energy to join
metals. The welding processes
covered in this book are some of
the most commonly used electric arc welding processes today.
These processes are Shielded
Metal Arc Welding (SMAW), Gas
Tungsten Arc Welding (GTAW),
Gas Metal Arc Welding (GMAW),
Flux-Cored Arc Welding (FCAW),
and Submerged Arc Welding (SAW).
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Adhesive
Bonding
Welding differs from the other joining processes in that the joint
created by welding is very strong and permanent. Parts that
have been welded together cannot be easily separated. Welding
is fast and is one of the most economical ways to join metal
together permanently.
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Material Joining Processes
Adhesive Bonding
Adhesive bonding joins materials together using a nonmetallic material.
Adhesives are available in several different forms including gels, liquids,
pastes, and drops. This process is especially useful when joining dissimilar
materials.
Welding
The American Welding Society (AWS) defines welding as a joining process that produces coalescence of materials by heating
them to the welding temperature, with or without the application
of pressure or by the application of pressure alone, and with or
without the use of filler metal.
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The puddle of liquid metal created while welding must be protected from air to keep it from oxidizing (becoming brittle). This
can be accomplished through the use of a flux contained on or
inside the electrode, or by the use of an external shielding gas.
In some cases, both flux and shielding gas are used.
In most cases, simply melting the pieces of metal together will
not create a strong enough weld. For this reason, filler metal is
typically added to increase the overall strength of the weld. Depending on the welding process being used, the filler metal may
also be the electrode or is added separately.
Success in welding is achieved not only by the skill of the person
performing the welding process, but also by carefully matching
the filler metal chemistry to the base metal. This insures that
the resulting weld will have the required physical and chemical
properties to meet the service requirements of the part being
welded.
Methods of Arc Welding
In manufacturing, the welding processes may be performed using the manual, semi-automatic, automatic, and robotic methods. In manual welding all aspects of the arc and weld deposit
are controlled by hand.
Introduction To Welding
Semiautomatic Welding
Semiautomatic welding is defined by the American Welding Society (AWS) as manual welding with equipment that automatically controls one or more of the welding conditions.
The wire feeder and the constant voltage aspect of the power
supply make the continuous wire processes such as GMAW and
FCAW semiautomatic. The wire feeder controls the filler metal
addition and the arc voltage controls the arc length, hence two
parts are being controlled automatically. The operator physically
manipulates the gun or torch angles and travel speeds while
welding.
Automatic welding can be performed
with a number of welding processes
in three basic ways: Fixed Automation, Flexible Automation and Robotic
Welding (Programmable Automation).
Figure 3 – A Robotic Arc Welding Cell
Robots offer quick movement over a work envelope to weld
small component parts or large part assemblies. The robot can
make the proper sized weld accurately and consistently with optimal speed and repeatability.
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Automatic Welding is defined by the
American Welding Society (AWS) as
welding with equipment that requires
only occasional or no observation of
welding, and no manual adjustment
of the equipment controls.
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Automatic Welding
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Figure 2 – A Seam
Fixed Automation utilizes a dedicated
Welding System
machine specifically designed for arc
welding the same specific parts on a continuous production basis. An operator loads a part into a fixture, presses a Start button
and the part is automatically welded. The operator will unload
the welded part, inspect the part, load a new part, and start the
process again (typically GMAW or GTAW processes).
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The parts to be welded may be rotated under the welding torch
or the welding torch may move across or around the part, usually in just one axis of movement. Parts to be welded are usually
of a simple design requiring a single weld These welding methods are often used:
• Arc spot weld
Robots offer the capability of making small production runs that
can quickly be retooled for changeovers, or they can be dedicated to making large volume production runs operating 24 hours
a day / 7 days a week.
Robotic Welding offers the following advantages:
• Minimizes hazards to the operator.
• Minimizes labor and material waste, through greater accuracy and consistency.
• Faster part cycle times.
• Capable of welding in all positions.
• Capable of quickly adapting to welding a variety of production parts as needed and/or parts changes.
Robotic welding is programmable and highly flexible to adapt
and quickly change the movement of the welding arc to produce
high quality welds on complex part designs.
• Plug or slot weld
Electrical Terms for Welding
• Linear weld
Primary Voltage
• Circumferential weld
Flexible Automation is simply a variation of Fixed Automation
but allows for some part variation such as a diameter change on
a circumferential weld or a length adaptation on a longitudinal
weld.
Robotic Welding (Programmable Automation)
Robotic welding is defined by the American Welding Society
(AWS) as welding that is performed and controlled by robotic
equipment.
Primary voltage is the voltage input to the machine that is supplied by the power company, or by an auxiliary electrical power
generator unit. This voltage has a constant voltage or potential
at every receptacle. This voltage could be 120 (110/115), 208
(200), 230 (220/240), 460 (440/480), 575 (600), etc, VAC (volts
of alternating current) with a frequency of 50 or 60 Hz. Welding power source transformers are designed to work with these
voltages.
Primary voltage may be single or three-phase (Figure 4 and
Figure 5). Primary Voltage is measured at the electrical panel
or line disconnect device, receptacle, or the terminal strip inside
the welding machine.
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Polarity
Single Phase
Two Fuses
Green = Earth
Ground
Single Phase AC
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Figure 4 – Single Phase Primary Power (1Ø)
The polarity of the direct current welding arc, or the direction of
electrical current flow, is very important. The shielded metal arc
welding (SMAW) process was first used with bare or lightly fluxcoated metallic electrodes connected to the negative (-) terminal
(pole). The work connection was then made to the positive (+)
terminal (pole) of the welding power source. This is Electrode
Negative and is also called “Straight Polarity” (Figure 7). When
the electrode is connected to the positive (+) terminal (Electrode
Positive) and the work cable to the negative (-) terminal, the
connection is referred to as Electrode Positive or “Reverse Polarity” (Figure 8). It is important to make the connections so the
current flow is in the correct direction for the specific welding
process and procedure.
Welding Power Source
er.
+
L1 L2 L3
Mill
-
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Three Phase
Three Fuses
Green = Earth
Ground
Three Phase Primary Power
Figure 5 – Three Phase Primary Power (3Ø)
Figure 7 – Direct Current Electrode Negative (DCEN)
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0
0
Alternating Current
Welding Power Source
Alternating Current That Has Been
Rectified To Direct Current
+
er.
Mill
-
Figure 6 – Alternating Current Converted to Direct Current
Welding Current Types
+
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There are two types of Electrical Current: direct current (DC) and
alternating current (AC).
-
Direct Current
Direct current is an electrical current that flows in one direction
and has either a negative or positive polarity. A battery, either a
flashlight (dry cells) or an automobile (wet cells ), is a source of
Direct Current and has a positive and a negative terminal (pole).
The conventional theory of electrical current flow, credited to
Benjamin Franklin, states that electrons flow from the positive
(+) terminal to the negative (–) terminal.
A Direct Current output welding machine also has a positive and
a negative terminal. Polarity of the electrical current (or the direction of current flow) is selected by connecting the electrode
cable, holder, and an electrode to either the positive or negative
terminal. The work cable, and its clamp, is connected to the opposite terminal. The current flows from the negative (–) terminal
to the positive (+) terminal in a single direction. This is the electron theory that is credited to Thomas Edison and is used in arc
welding theory.
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Figure 8 – Direct Current Electrode Positive (DCEP)
30%
70%
70%
30%
DCEN (DCSP)
DCEP (DCRP)
Figure 9 – Direct Current Heat Distribution
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