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WELDING TECHNOLOGY
Dr. S.Thiru PhD.,
ENME 102Full Lectures
Mechanical engineering department
Copyright © 2020 University of Jeddah
http://www.uj.edu.sa/Home.aspx
CONTENTS
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➢ Fundamentals of Welding.
➢ Safety and Health of Welders.
➢ Arc Welding with a Consumable Electrode.
➢ Electrodes and Filler Materials.
Introductions
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Reasons for and benefits of joining (by design goals)
Achieve functionality
Facilitate manufacturability
Minimize costs
Allow complex shapes to be formed
joining Processes and Equipment
Overview:
Joining processes fall into three major categories：
1. Welding
2. Adhesive bonding
3. Mechanical fastening
Welding processes, classified into three basic
categories:
1. Fusion welding
2. Solid-state welding
3. Brazing and soldering.
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AWS Master chart of welding and allied
processes
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Major categories
Allied processes, which use similar energy sources
AWS designation
AMERICAN WELDING SOCIETY
Welding Processes Listed by Energy Source
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Electric Arc Fusion Welding
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Arc welding ▪ For workpieces that are electrical conductors, it can be made part of the
electric circuit with an electric power supply. ▪ As part of the electric circuit, electric current is passed to the conductive
workpiece through an arc from an electrode across a gap in a gas
Resistance welding If the electric current can be passed directly through the workpiece as an integral part of the circuit.
High Energy beam welding A beam of intense, high-density electrons are applied to heat a workpiece (whether an electrical conductor or not).
Advantages and Disadvantages of Welding
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Advantages Joints are permanent,
precluding accidental (or even intentional) disassembly and loosening
Wide variety of process embodiments
Applicability to many materials within fundamental class
Allows manual or automated operation
Can be portable
Reasonable overall cost, usually
Provides leak tightness with continuous welds
Disadvantages Prevents/precludes disassembly for any
purpose
Heat of some welding (especially involving fusion) disrupts base material properties
Precludes joining between materials from different classes
Unbalanced heat input leads to distortion or residual stresses
Requires considerable operator skill
Can be expensive due to skilled labor rates or due to labor intensity for thick, long, or critical welds
Capital equipment can be expensive, especially for some automated processes
Modes of Arc Welding
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Direct current straight polarity (DCSP): Arc heating when the workpiece is positive and the welding electrode is negative. Also called as dc electrode negative (EN) or dc-.
Direct current reverse polarity (DCRP): Arc heating when the workpiece is negative and the welding electrode is positive. Also called as dc electrode positive (EP) or dc+.
AC mode: One-half of the voltage cycle operates as dc-/DCSP, while the other half operates as dc+/DCRP.
Arc Welding Processes
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Nonconsumable Electrode Arc Welding
Gas tungsten arc welding (GTAW)
Plasma arc welding (PAW)
Stud arc or simply stud welding (SW)
Magnetically-impelled arc butt welding (MIAB)
Consumable Electrode Arc Welding Processes
Shielded metal arc welding (SMAW)
Flux-cored arc welding (FCAW)
Gas metal arc welding (GMAW)
Submerged arc welding (SAW)
Electrogas welding (EGW)
Electroslag welding (ESW)
GTAW PAW
SMAW FCAWSAW
https://www.youtube.com/watch?v=4hqTJHFOHY8
https://www.youtube.com/watch?v=jRmqrqIGOIY
https://www.youtube.com/watch?v=LXBz2ZPeGnY
https://www.youtube.com/watch?v=LcqbmywaLxA
https://www.youtube.com/watch?v=QMFDpZwbPwg
https://www.youtube.com/watch?v=pVyYvcEqkcQ
https://www.youtube.com/watch?v=twUAa5LWUvk
https://www.youtube.com/watch?v=H6QGLGJ-BOE
https://www.youtube.com/watch?v=SlJBLNVLAOA
CODES, STANDARDS AND PRACTICE
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American Welding Society
The AWS multi-volume Welding Handbook is a comprehensive treatment of the art and technology of welding [AWS].
It includes: Volume 1 - Fundamentals of Welding
Volumes 2 and 3 - Welding Processes
Volume 4 - Engineering Applications - Materials
Volume 5 - Engineering Applications - Design
The welding of structural (non-pressure boundary) members typically complies with either AWS D l.l or AWS D1.6. The American Welding Society (AWS) standards of interest to welding piping and pipelines include:
AWS A 3.0 - Welding terms and definitions, including terms for brazing, soldering, thermal spraying and thermal cutting.
AWS A 5.01 - Filler metal procurement guidelines.
AWS A 5.XX - Series of filler metal specifications.
AWS Dl.l - Structural welding code – steel.
General Requirements
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Welder’s protective clothing
General Requirements
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Minimum warning label for Arc welding processes and equipment
Protection in the general area
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Protective screens Persons adjacent to welding and cutting must be
protected from radiation and hot spatter by flame resistant shields or screens with suitable eye and face protection clothing.
Wall reflectivity Where arc welding or cutting is regularly carried out
adjacent to painted walls, the walls should be painted with low reflective pigments for UV radiation such as Titanium dioxide or Zinc oxide.
Fire Open flames, electric arcs, spatter, hot metal and sparks
are the potential fire igniting elements related to welding.
The risk of fire is greatly increased by combustible floor, partitions, ceiling etc and also by the presence of combustibles in the working area such as wood, paper, trash, cotton, textiles, chemicals, paints, and flammable liquids and gases. For outdoor, dry grass and brushes highly ignite potential to welding.
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