Welding Fundamentals

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PowerPoint to accompany

WeldingPrinciples and PracticesThird Edition

Sacks and Bohnart

History of Welding

Chapter 1

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Overview

• Welding is joining two pieces of metal by:– Heating to temperature high enough to cause

softening or melting– With or without application of pressure– With or without use of filler metal

• Melting point same as metals beginning joined or melting point below metals but about 800º F

• New methods, applications and systems – Tremendous progress in short time

• Usually best method to use when fastening metal

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History of Metalworking

• Began when people found they could shape rocks by chipping them with other rocks

• Copper probably first metal to be worked– Ductile (easily hammered, bent or drawn)– In Egypt as early as 4000 B.C. and USA before

2000 B.C.

• Welding began more than 3000 years ago– Hot or cold metals hammered to obtain forge weld– Forged metals, bronze and iron mentioned in Old

Testament

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• Bronze developed between 3000 and 2000 B.C.

• Iron became known to Europe about 1000 B.C.– Several thousand years after use of copper– Philistines had four iron furnaces about 1300 B.C.

• Produced swords, chisels, daggers, and spearheads

– Egyptians began making iron tools during period of 900 to 850 B.C.

– Replaced bronze as metal used in manufacture of utensils, armor and other applications after 800 B.C.

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• Famous Damascus swords and daggers made in Syria about 1300 B.C.– Sought because of their strength and toughness– Made by forge-welding iron bars of different

degrees of hardness, drawing them down, and repeating process many times

• Working of metals followed one another in great ancient civilizations– Copper, bronze, silver, gold, and iron

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• Time of Roman Empire– Iron use common in Europe, Near East and Far East

• Chinese developed ability to make steel from wrought iron in 589 A.D.

• Belgians responsible for progress with steel in Europe

• Japan manufactured steel by repeated welding and forging and controlling amount of carbon by use of fluxes– Produced famous Samurai sword

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• Blast furnace developed for melting iron about 1000 to 1200 A. D.

• Fourteenth and fifteenth centuries saw great improvements in design of blast furnaces

• First cast iron cannon produced in early 1600s

• Industrial Revolution in the middle of the eighteenth century brought many improvements

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• Present factory system of mass production introduced– American, Eli Whitney, developed idea of

interchanging parts in manufacture of arms

• Working of dies and molds became commonplace by beginning of nineteenth century

• Henry Ford involved in developing assembly line method for manufacturing automobiles early in twentieth century

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Early Developments in Welding

• Edmund Davy discovered acetylene at beginning of nineteenth century

• Sir Humphrey Davy discovered the electric arc in 1801– Concerned with use of arc for illumination– Demonstrated possible to maintain high voltage arc

for varying periods of time by 1809

• Workable electrical generating devices invented and developed on practical basis by 1850

These inventions were forerunner of present arc welding process.

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History of Fusion Welding

• First documented instance done by Auguste de Meritens in 1881– Welded lead battery plates together with carbon

electrode

• Two of Auguste's pupils, N. Benardos and S. Olszewski continued work and issued patent for welding process using carbon electrodes and electric power source four years later– Primary goal was repair welding

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Bare Metal Electrode Welding

• Introduced in 1888 by N. G. Slavianoff (Russian)– Discovery first recognized in western Europe in 1892

• C. L. Coffin was pioneer of welding industry in United States– 1889 received patent on equipment and process for

flash-butt welding– 1890 received additional patents for spot welding– 1892 received patent for bare metal electrode arc

welding process • Without knowledge of Slavianoff's work

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• Foresche and Picard developed first commercial oxyacetylene welding torch at turn of the century

• Electric arc welding method used in US until about 1920– Handicapped because of welds produced by these

electrodes not as strong as metal being welded• Welding arc very unstable

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• In 1907 Kjellberg (Swedish engineer) received patent covering electrode-coating process– Coating thin and acted only as stabilizer of arc– Produced welds little better than bare electrodes

• In 1912 Kjellberg received another patent for electrode with heavier coating made of asbestos with binder of sodium silicate

• In 1908, Benardos patented electroslag process of welding thick plates in one pass

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• Technology of welding progressed slowly until World War I– Demands of war called for improved methods of

fabrication– End of war, welding widely accepted

• Research on coated electrodes through 1920s resulted in electrode coatings and improved core wire

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Multipass Welds

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Ability to make multipass welds such as this one, on plate and pipe, led to growth of industry. Welds are sound and have uniform appearance.

Pass 1

Pass 2

Pass 3

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• Stick welding process– Advanced rapidly due to electrode coatings and

improved core wire– Now called shielded metal arc welding (SMAW)

• X-ray development– Possible to examine internal soundness of welded

joints

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Shipbuilding

• 5,171 vessels constructed to American Bureau of Shipping standard– Through 1945

– During Maritime Commission wartime shipbuilding program

• Welding was replacing riveting as main method of assembly

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Development of Modern Welding

• Design of welding machines changed very little during postwar period– Done with d.c. current from batteries

• Use of a.c. welding machines occurred in late 1920 and increased in the early 1930s– First high frequency a.c. industrial machine

introduced in 1936 by Miller Electric Manufacturing Company

– High rate of metal deposition and absence of arc blow

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Inert Gas Welding

• World War II spurred development

• Possible to produce welds of high purity and critical application

• Patent issued in 1930 to Hobart and Devers for use of electric arc within inert gas atmosphere– Not well received because high cost of argon and

helium and lack of suitable torch equipment

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GTAW Welding

• Tungsten electrode replace magnesium procedure– Patent issue in 1942

• Linde Company developed gas tungsten arc welding (GTAW)– Also called tungsten inert gas (TIG) process or

HELIARC– Perfected water-cooled torch capable of high

amperage

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Tungsten Inert Gas (TIG) Process


An aluminum weld made using the TIG process. The welding

of aluminum is no longer a problem and can be done with the same ease as that of steel.

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GTAW Welding

• First done with rotating d.c. welding machines• Later a.c. units developed• In 1950s

– Selenium rectifier type d.c. welding machines– a.c.-d.c. rectifier welding machines with built-in

frequency for GTAW welding became available

• Miller Electric Manufacturing Company developed Miller controlled-wave a.c. welder for critical welds on aircraft and missiles

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Development of Modern Welding (continued)

• Use of aluminum and magnesium increased– Development of GTAW welding– Desirable characteristics of reduced weight and

resistance to corrosion

• Thicker materials in construction, which required preheating using GTAW welding

• U.S. patent issued in 1948 for gas metal arc welding (GMAW) process– Superseded earlier terms of metal inert gas (MIG)

and metal active gas (MAG)

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GMAW Process

• Concentrates high heat at a focal point• Produces

– Small heat-affected zone– Narrow bead width– Deep penetration– Faster welding

speed

• Now used in allindustries


Responsible for over70 percent of welds

being performed today.

St Louis Car. Co.

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Development of Modern Welding (continued)

• Rapid changes occurred in 1980s and 1990s– Exotic multiple gas mixes– State-of-art electrodes– Onboard computers– Robotic welding

• Methods developing that may change way welds made in future

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Processes Involving Use of the Electric Arc

• Arc spot welding

• Atomic-hydrogen welding

• Electrogas

• Plasma arc welding

• Stud welding

• Submerged arc welding

• Underwater arc welding

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Specialized Processes Involving Use of the Electric Arc

• Cold welding

• Electron beam welding

• Explosive welding

• Force welding

• Friction welding

• Friction stir welding

• Laser welding

• Oxyhydrogen welding

• Thermit welding

• Ultrasonic welding

• Welding of plastics

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Industry Demand

• Over 90 welding processes

• Force new and improved developments in machines, gases, torches, electrodes, procedures, and technology

• Constant research for new metals done by shipbuilding, space and nuclear industries– Spurs research in welding

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Welding Associations

• American National Standards Institute (ANSI)• American Petroleum Institute (API)• American Society of Mechanical Engineers

(ASME)• American Welding Society (AWS)• American Bureau of Shipping (ABS)

Provide guidance and standards relating to the welding industry.

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Welding as an Occupation

• Can be certified by AWS, ASME and API– Tests difficult and require many hours of practice

• Key positions in major industries– Important to economic welfare of country

• Gender friendly• Done in every civilized country in the world• Offer prestige and security• Chances for advancement excellent

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Industrial Welding Applications

• More than 90 different welding processes

• Divided into three major types– Arc– Gas– Resistance

• Number of other types used to lesser extent– Induction, forge, thermit, flow, and brazing

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Resistance Welding

• Includes spot welding, seam welding, flash welding, projection welding, and other similar processes performed on machines

• Operators usually taught on job– Semiskilled workers do not need specific hands-on-

welding skills

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Arc and Gas Welding

• Focus of this text

• Combine art and science

• Welders have almost complete control of the process– Must know properties of metals to weld; which

weld process to use; and how to plan, measure, and fabricate

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Welding Positions

As well as flat and horizontal

Vertical


Miller Electric Mfg. Co.

Overhead

General Electric Corp.

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Qualifications and Personal Characteristics

• Welders certified for ability to do work and work is inspected

• Required to pass periodic qualification tests

• Certifications issued according to kind and gauge of metal and specific welding process

• Can hold several different certifications simultaneously

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Example of Magnetic-Particle Testing in Building

Weld testing andinspection give

proof of the soundness of welds.


Circlesafe Aerosol/Circle Systems, Inc.

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Basic Tasks

• Gas weld– Attaching proper tip and adjusting welding

regulators for proper volume and gas pressures

• Electric arc welding– Regulate welding machine for proper welding

current, select proper electrode size and type, and right shielding gas

• Need steady hand and have good visualization skills

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Master Welder Job Examples

Welds in these tanks mustmeet X-ray requirementsand pass a dye penetrant

test. Tanks are often linedwith a very thin layer of

pure silver.


Nooter Corp Creating Art!Enrique Vega

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Master Welder

• Master craftsperson

• Able to weld all steels and alloys– Plus nickel, aluminum, tantalum, titanium,

zirconium, and their alloys and claddings

• Welds of highest quality

• Welds meet requirement of job– Delicate welding of silver and gold– Heavy pressure vessels requiring 4-inch plate

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Welding Occupations Requiring a High School Education

• Welding operator• Welding fitter• Combination welder• Master welder• Welding supervisor• Welding analyst• Inspector• Welding foreman

• Welding superintendent• Equipment sales• Sales demonstrator• Sales troubleshooter• Welding instructor• Robotics welder operator• Jog or fabrication shop

owner

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Welding Occupations Requiring a College Education

• Welding engineer(metallurgical)

• Welding development engineer

• Welding research engineer

• Welding engineer

• Technical editor• Welding professor • Certified welding inspector

(AWS/CWI)• Corporation executive• Owner of welding business• Sales engineer

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Safety and Working Conditions

• Indoors or outdoors• Noisy

– Hearing protection needed

• Awkward positions• Spacious surroundings or

cramped quarters• High off ground in

scaffolds with safety harness


The Lincoln Electric Corp.

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Job Hazards

• Fire danger

• Burns (including "sunburn" from electric arcs)

• Noxious fumes from materials vaporized at high temperatures

• Eyestrain

• Welders flash

• Electric shock

Hazards can be minimized or eliminated by use of proper protective

clothing and equipment.

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Ways to Stay Current

1. Read trade journals, service manuals, textbooks, and trade catalogs

2. Join associations such as the American Welding Society

3. Research topics on the Internet

4. Trade trips with your peers

Welding Fundamentals

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