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METAL JOINING

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Title: METAL JOINING


1
METAL JOINING
2
METAL JOINING
  • Even the simplest object is an assembly of
    components
  • Complex ones - greater number of parts-
    subassemblies joined to perform the function
  • METHODS-
  • WELDING,
  • BRAZING,
  • SOLDERING,
  • ADHESIVE BONDING,
  • MECHANICAL JOINING

NITC
3
WHY JOINING?
  • IMPOSSIBLE TO MAKE AS ONE PIECE
  • EASINESS AND ECONOMY IN MANUFACTURE
  • EASY IN REPAIRS AND MAINTENANCE
  • FUNCTIONAL PROPERTIES DIFFER-
  • e.g. Carbide tips of tools,corrosion
    resistant parts, tungsten carbide tip of pens,
    brake shoes to metal backing etc
  • TRANSPORTING SITE/ CUSTOMER

NITC
4
CLASSIFICATION
  • According to the STATE of the materials being
    joined
  • Extent of external heating- PRESSURE
  • Use of FILLER materials

NITC
5
NITC
Joining Processes
LIQUID
MECH. JOINING
SOLID
LIQUID- SOLID
ARC
CUTTING
CHEMICAL
RESISTANCE
CONSUMABLE
NON CONSUMABLE
Forge Cold Ultrasonic Friction Explosion Diffusion
Brazing Soldering Adhesive Bonding
SMAW SAW GMAW FCAW EGW ESW
Oxy-fuel Thermit
GTAW PAW EBW LBW
Spot Seam Projection Flash Stud percussion
Fastening Crimping Seaming Stitching
6
  • History of welding
  • And
  • American Welding Society

7
Vulcan The Roman Fire God
8
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9
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10
  • Welding Heat Exchanger

11
  • Thermite Welding Patent 729573

12
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13
  • 1948
  • The Ohio State University Board of Trustees
    established the Department of Welding
    Engineering on January 1 as the first of its kind
    for a Welding Engineering cirriculum at a
    University.  OSU pioneered the Welding
    Engineering through an emphasis in the Industrial
    Engineering Department the previous nine years. 
    The advantages of this engineering degree is
    1) Enable satisfactory administration of problems
    relating to education and research in the welding
    field. 2) Recognition is given to the Welding
    Engineer as an entity among applied sciences. 3)
    A degree is authorized which is descriptive of a
    particular discipline imposed in training for
    professional work in the field.
  • Air Reduction Company develops the Inert-Gas
    Metal-Arc (MIG) process.

14
  • SIGMA Welding (Shielded Inert Gas Metal Arc)
    was developed to weld plate greater than1/8 inch
    instead of the "Heli-Arc" welding process. The
    arc is maintained in a shield of argon gas
    between the filler metal electrode and the
    workpiece. No flux is used. Licensed by Linde Air
    Products Co.
  • 1948-1949
  • Curtiss-Wright Corporation looks at brazing as
    a strong, lightweight process for durable
    assemblies.
  • 1949
  • American Westinghouse introduces and markets
    welding machines using Selenium Rectifiers.
  • US Navy uses inert-gas metal arc welding for
    aluminum hulls of 100 feet in length.
  • 1950
  • The Kurpflaz Bridge in Germany was built as the
    first welded orthotropic deck.

15
  • 1950s
  • Electron Beam (EB) welding process developed in
    France by J. A. Stohr of the French Atomic Energy
    Commission. First Public disclosure was 1957.
  • Wave soldering is introduced to keep up with
    the demand of Printed Wiring Boards used in the
    electronics age.
  • Research on testing of brazed joint begins as
    serious endeavor for the next ten years.
  • 1950
  • Electroslag Welding (ESW) is developed at the
    E. O. Paton Welding Institute, Ukraine USSR.
  • Third Edition of the Welding Handbook is
    printed by AWS.
  • Flash Butt Welding is the standard for welding
    rail line construction.

16
  • 1951
  • Russia use Electroslag Welding (ESW) process in
    production.
  • The Philip Roden Co. of Milwaukee Wisconsin
    announces the DryRod electrode oven. This oven is
    intended to provide a controlled moisture
    environment of 0.2 moisture standard set forth
    by the government. This oven provides adjustable
    temperature control of 200-550 F, vented and
    holding 350 pounds of electrodes.
  • 1953
  • Modifying the Gas Metal Arc Welding (GMAW)
    process, Lyubavskii and Novoshilov used CO2 with
    consumable electrodes. Resulted in hotter arc,
    uses higher current, and larger diameter
    electrodes.
  • The Ohio State University established a Welding
    Engineering College curriculum out of the
    Industrial Engineering Department.

17
1957 Flux Cored-Arc Welding (FCAW) patented
and reintroduced by National Cylinder Gas Co.
Plasma Arc Welding (PAW) Process developed by
Robert M. Gage Russia, Britain, and USA
independently develop a short-circuiting transfer
for low-current low-voltage welding in a carbon
dioxide atmosphere. Braze repair process for
cracks in jet engine combustion chambers and
transition ducts. 1958 The Soviet Union
introduced the Electroslag Welding (ESW) Process
at the Brussels World Fair in Belgium. This
welding process had been used since 1951 in the
USSR which was based on the concept and work of
an American, R. K. Hopkins. Perfected at the
Paton Institute Laboratory in Kiev, Ukraine, USSR
and the Welding Research Laboratory in
Braitislava, Czechoslovakia. AWS Committee on
Brazing and Soldering is formed to develop a test
for evaluating strength of brazed joints. Robert
Peaslee proposes a test in the Welding Journal.
18
  • 1959
  • Electroslag welding process was first used at
    the Electromotive Division of General Motors in
    Chicago and was called the "Electro-Molding
    Process".
  • Development of Inside-Outside Electrode which
    did not require an external gas shielding -
    Innershield from Lincoln Electric Co.
  • 1958-1959
  • Short Arc (Micro-wire Short Arc) developed from
    refined power supplies and smaller diameter
    wires.
  • 1960s
  • Pulsed Arc Welding...(more to follow)
  • Space Program is underway...(more to follow)
  • Difficult to stabilize GTAW at below 15 amps,
    Microplasma is developed to overcome the
    limitation.

19
1960 Development of a cold wall vacuum
furnace. First laser beam produced using a
ruby crystal for the Light Amplification
Stimulated Emission Radiation (LASER).
Explosive welding is developed in USA. Hughes
Aircraft Company (Mainar) develops the first ruby
laser (springtime). Bell Telephone
Laboratories (Ali Javan) developed and presented
the first gas laser using neon and helium (fall
time) 1962 The Mercury Space Capsule is
formed using inner and outer titanium shell, seam
welded together using a three-phase resistance
welder by Sciaky. 1963 U.S.S. Thresher sinks
off the coast of New Hampshire and by December,
the U.S. Navy charters the Submarine Safety
Program (SUBSAFE) to control the fabrication,
inspection and quality control of submarine
construction. The presumed failure was with a
silver-brazed piping joint, but after the
investigation, the whole welding and brazing
program was suspect. Included was the material
properties of the welding and brazing filler
metals.
20
  • 1965-1967
  • CO2 lasers are developed for cutting and
    welding.
  • 1967
  • H. J. Clarke makes the following Predictions
    during the AWS Plummer Lecture in Houston as he
    ties the current state of technology of welding
    to the future of progress
  • World's Population would be greater than 5
    Billion.
  • Large scale farming of the ocean and
    fabrication of synthetic protein.
  • Controlled thermonuclear power as a source of
    energy.
  • General immunization against bacteria and
    virile infections, perfected and available.
  • Primitive forms of life will created in the
    lab.
  • Automation will have advance for performance of
    menial chores and complicated functions.
  • Housewives would be ordering groceries and
    everyday items from central stores linked to the
    home electronically. (!!!)

21
  • Children will be receiving education at home -
    "either by television or with personal teaching
    machines and programmed instructions"
  • Moon - mining and manufacture of propellant and
    on Mars, permanent unmanned research stations.
  • Weather manipulation by the military.
  • Effective anti-ballistic missile defense in the
    form of air-launched missiles and directed energy
    beams.
  • Libraries will be "computer-run"
  • Gravity welding is introduced in Britain after
    its initial discovery by Japan.
  • 1969
  • The Russian Welding Program in Space began by
    producing Electron Beam welds on SOYUZ-6. Welding
    an AMG6 and DM-20 aluminum alloys with the Vulkan
    process. Sponsored by the E. O. Paton Welding
    Institute Academy of Science.

22
  • 1970
  • As miniaturization developed from the pressure
    to increase component densities, Surface Mount
    Technology is developed. This required new ways
    to make soldered joints, including the
    development of vapor phase, infrared, hot gas and
    other re-flow technologies.
  • First AWS International Brazing Conference
    including 24 papers presented created much
    interest in the brazing process.
  • BP discovers oil off the coast of Scotland.
  • 1971
  • British Welding Institute (Houldcroft) adds
    oxidizing gas jet around laser beam to develop
    laser cutting.
  • 1973
  • The American Astronauts used Electron Beam
    welding process in June 1973 welding Aluminum
    Alloy 2219-T87, Stainless 304 and Pure Tantalum.
  • Welding equipment manufacturers concentrate on
    equipment refinement instead of new processes.
  • Two Supertankers, Globtik Tokyo and Globtik
    London (476025 DWT) were built for carrying 153
    million gallons (3 million barrels) of crude oil.

23
  • 1976
  • First automotive production application of
    lasers weld begins with General Motors
    Corporation, Dayton Ohio using two 1.25 kW CO2
    lasers. for welding valve assemblies for emission
    control systems.
  • 1977
  • The US Federal Highway Administration issues a
    moratorium of Electroslag Welding (ESW) when
    cracks are discovered during an inspection of a
    bridge in Pittsburgh, Pennsylvania on an
    interstate highway. Failure analysis was
    conducted by Lehigh University on Interstate 79.
  • 1980
  • The Fort McHenry tunnel contract, for 750
    Million Dollars, is awarded to begin
    construction, completing Intestate 95 through
    Baltimore, Maryland. This is the largest tunnel
    of its kind, 180 feet at the bottom with two
    separate four lane immersed tunnels removing 3.5
    million cubic yards of dredge.

24
  • 1983
  • Homopolar pulse welding variation of the upset
    welding process research begins at the University
    of Texas at Austin at the Center for
    Electromechanics.
  • 1987
  • Laser research begins a unique method for
    depositing complex metal alloys (Laser Powder
    Fusion).
  • 1991
  • TWI of Cambridge England develops the Friction
    Stir Weld (FSW) process in its laboratory. This
    process differs from conventional rotary
    technology whereby a hard, non consumable,
    cylindrical tool causes friction, plasticizing
    two metals into a Solid-State Bond. No shielding
    gas or filler metal is required. Metals joined
    successfully include, the 2XXX, 6XXX and 7XXX
    series aluminum. NASA is the first US venture
    which welded the massive fuel tank for the Space
    Shuttle.
  • Brazing Handbook (Fourth Edition) shows the
    data of the filler metal/base metal failure
    transitions between 1T and 2T overlap and is the
    key for the design data (factor of safety).

25
1996 Over 7,00,000 brazements are produced for
the aircraft industry in the US and Canada.
Over 132,010,00 units of brazed automotive parts
are produce. 1999 The Edison Welding
Institute develops a solution to obtaining deeper
penetration of a GTA weld by introducing FLUX
onto the surface of the weld. This FLUX helps
drive the welding arc heat deeper into the weld
joint and permits 300 percent more penetration.
 2000 Magnetic Pulse Welding (MPW) is
introduced by Pulsar Ltd. of Israel using
capacitive power as a solid state welding
process. Discharging 2 Million amps in less than
100 microseconds this process can create a
metallurgical, a non-metallurgical or a
mechanical lock, depending on the substrate
involved. No heat affected zone (HAZ) is created
since only a rise of 30oC occurs. Tailored
welded blanks of aluminum are used where spot
welding was once performed.
26
2000Researchers from Argonne National Laboratory
use the energy of the x-ray to weld metal-matrix
composite (Ti or Al / Al2O3 or SiC) materials.
Diode laser welding, once limited to compact
disks, laser printers, and laser pointers, are
now making their way to the manufacturing floor.
Welding Type 304 Stainless steel (0.024 inch),
Titanium foil (0.005 inch thick) and laser
brazing with a silicon-bronze brazing wire.
Conductive heat resistance seam welding (CHRSEW)
is developed. The process uses steel cover sheets
placed on top of aluminum butted together. Using
conventional seam welding, the heat generated
from the steel forms a molten interface on the
aluminum and fusion is made at the butt joint.
The steel covers are then removed.
27
  • 2001 AWS D17.1, "Specification for Fusion
    Welding for Aerospace Applications" is published
    in March.  The efforts of approximately 50
    individuals from a cross-section of the Aviation
    Industry and government produces the first
    commercial aviation welding specification.
    Flame brazing 5XXX aluminum alloys using
    non-corrosive flux. Sulzar Elbar introduces
    laser powder welding technology. Permits
    rebuilding of substrate material (High Creep
    Resistance) and reproduction of the single
    crystal structure.
  • 2002 From Linde Gas in Germany, a Diode laser
    using process gases and "active-gas components"
    is investigated to enhance the "key-holing"
    effects for laser welding. The process gas,
    Argon-CO2, increases the welding speed and in the
    case of a diode laser, will support the
    transition of heat conductivity welding to a deep
    welding, i.e., 'key-holing'. Adding active gas
    changes the direction of the metal flow within a
    weld pool and produces narrower, high-quality
    weld. CO2 Lasers are used to weld polymers.
    The Edison Welding Institute is using
    through-transmission lasers in the 230-980 nm
    range to readily form welded joints. Using
    silicon carbides embedded in the surfaces of the
    polymer, the laser is capable of melting the
    material leaving a near invisible joint line.
    2003 2004 2005 Future developments.

28
ABOUT AWS The American Welding Society (AWS) was
founded in 1919 as a multifaceted, nonprofit
organization with a goal to advance the science,
technology and application of welding and related
joining disciplines
  • The Engineering Societies Building (left) in New
    York City was the home of AWS until 1961 when the
    Society moved to the United Engineering Center,
    also in New York City.

29
From factory floor to high-rise construction,
from military weaponry to home products, AWS
continues to lead the way in supporting welding
education and technology development to ensure a
strong, competitive and exciting way of life for
all Americans.
  • The Society moved its headquarters to Miami in
    1971 (left).

30
  • The American Welding Society, in conjunction with
    the Department of Energy, has put together a
    vision that will carry the welding industry
    through 2020.

31
  • Technical Publications
  • AWS offers over 300 books, charts, videos,
    replicas, proceedings, and software. 160
    AWS-developed codes, recommended practices, and
    guides are produced under strict American
    National Standards Institute (ANSI) procedures,
    including one of the most consulted codes in the
    world, D1.1 Structural Welding Code - Steel.

32
  • Foundation
  • Founded in 1989, to support research and
    education in welding and related technologies. It
    is committed to annually awarding fellowships to
    deserving graduate students for important
    research in areas important to the requirements
    of industry. Accordingly, each year the AWS
    Foundation administers six 20,000 grants -
    matched in kind by the participating
    universities. The award of scholarships to
    vocational and undergraduate college students is
    also a high priority and a student loan program
    has also been developed to prepare students for
    welding related careers.

33
  • The Professional Program
  • The AWS Professional Program offers a broad
    spectrum of Technical Papers describing the
    latest findings in welding research, processes
    and applications. Special sessions and gatherings
    exploring the boundaries of industry issues are
    also significant features of the convention.
    Subjects cover an entire range of industry
    concerns from the joining of space age materials
    to production management techniques, testing,
    quality assurance and more.

34
Which welding process(es) will see an increase in
use and which will see a decrease in use during
the next decade?
  • There was much speculation, but almost
    unanimously the process chosen for decline was
    shielded metal arc welding (SMAW). A very few
    speculated a decline in the use of gas metal arc
    (GMAW) and gas tungsten arc welding (GTAW). A
    significant group felt the continuous wire
    processes (FCAW, GMAW) would experience the most
    use. The GTAW process was the next most
    mentioned. One of the reasons stated for its
    increase was "the need for high-quality work on
    thin materials."

35
Welding Forges into the Future
Where do you see the use of welding automation
heading in your industry?
36
  • In what areas of welding do we need more
    knowledge?
  • Safety and Health. The industry needs more
    knowledge and awareness regarding the hazards of
    welding, according to the respondents.
  • Welding of the newer grades of high-strength
    steels, high- alloy steels and heat treatable
    steels.
  • We need to "keep up the 'how to weld' information
    with the increase in 'new' alloys, which are
    becoming more difficult to weld."
  • Automation. A variety of topics relating to
    automation. These included training in
    computerization and automation information on
    short-run automation and the need to create
    standard platforms for welding equipment, robot
    controllers, sensing devices and other automation
    peripherals.
  • The basics While universities and institutions
    are doing basic research, they cannot tell you
    the best process and fastest speed for a 1Ž4-in.
    fillet weld."

37
  • What are the strengths of the welding industry?
    What are its weaknesses?
  • What business improvements during the next ten
    years would be in your company's best interests?
  • What has to be done in the future to keep the
    welding industry healthy?
  • More than 50 of the respondents believe
    improving the image of welding so top students
    will be drawn to the industry and bettering
    training methods for welders and welding
    engineers are the keys to welding's future.

38
  • Are you optimistic or pessimistic about the
    future of your particular industry?
  • 92 of respondents indicated they are at least
    optimistic about the future.
  • One respondent summed up his reasons this way
  • Metallics will be around for a long time
    and they will need to be joined.

39
  • Since time machines still exist only in the
    stories of H. G. Wells and other works of science
    fiction, no one can tell us exactly how welding
    will fare in the 21st century. However, the
    people who responded to the Welding Journal
    survey represent a cross section of fabricators
    of welded products and producers of welding
    equipment and related products. Together they
    offer a wide range of experience and knowledge.
    Answering the questions separately, in their
    respective cities, they still formed a consensus.
    They agree the future looks promising for
    welding. It remains and will continue to be a
    productive, cost-effective manufacturing method.
    However, steps must be taken to bring more
    skilled personnel into the industry, or changes
    must be made to accommodate for the lack of
    skilled personnel (e.g., welding automation).
    They also indicated the welding industry must
    embrace all of the modern-day technological tools
    to keep pace with the rest of the world. .

40
LIQUID STATE PROCESSES
  • Partial melting and fusion of joint
  • Physical and mechanical changes taking place
  • Can be with application of pressure or by
    addition of filler material
  • Prior to joining, PREPARATION TO BE DONE
  • STANDARDS- AWS ASTM-
  • TYPES OF GROOVES, JOINTS

NITC
41
Types of welds and symbols
  • FILLET, SQUARE BUTT, SINGLE V,
  • DOUBLE V, SINGLE U, DOUBLE U,
  • SINGLE BEVEL BUTT, DOUBLE BEVEL BUTT,
  • SINGLE J BUTT, DOUBLE J BUTT,
  • STUD, BEAD(EDGE OR SEAL), PLUG,
  • SPOT, SEAM, MASHED SEAM,
  • STITCH, PROJECTION,
  • FLASH, UPSET etc. (REFER sketches supplied)

NITC
42
Standard location of elements of weld symbol
G- Grind C- Chip F-File M-Machine R- Rolling
Length of weld

Unwelded length
Size
Weld all around
Finish symbol
Specification process. No tail- SMAW
L
P
S
Field weld
Reference line
Arrow connecting reference line to arrow side of
joint /to edge prepared /member or both
Other side of arrow
Near side of Arrow
NITC
43
Groove face
GROOVE ANGLE
Joint angle
  • ROOT

Root Face
NITC
44
WELD POSITIONS WELD MOVEMENTS
  • FLAT
  • HORIZONTAL
  • VERTICAL
  • OVERHEAD
  • H
  • O
  • C
  • J
  • U
  • ZIGZAG

NITC
45
WELDING TERMINOLOGY
Slide 2 of 18
46
ELECTRODE COATING INGREDIENTS
  • Slag forming ingredients- silicates of sodium,
    potassium, Mg, Al, iron oxide, China clay, mica
    etc.
  • Gas shielding- cellulose, wood, starch, calcium
    carbonate
  • De-oxidising elements- ferro manganese, ferro
    silicon- to refine molten metal
  • Arc stabilizing calcium carbonate, potassium
    silicate, titanates, Mg silicate etc.
  • .Alloying elements- ferro alloys, Mn, Mo., to
    impart special properties
  • Iron powder- to improve arc behaviour, bead
    appearance
  • Other elements - to improve penetration, limit
    spatter, improve metal deposition rates,

47
PURPOSE OF COATING
  • Gives out inert or protective gas- shields
  • Stabilizes the arc- by chemicals
  • Low rate consumption of electrode- directs arc
    and molten metal
  • Removes impurities and oxides as slag
  • Coatings act as insulators- so narrow grooves
    welded
  • Provide means to introduce alloying elements
  • Bare electrodes - carbon- more conductive- slow
    consumption in welding

48
WELDING TECHNIQUES
  • FOREHAND BACKHAND

THIN Same direction torch Heat concentrated away
from bead Even flow, rippled design
THICK Opposite direction torch Heat concentrated
on bead Broad bead
49
WELD MOVEMENTS
STRAIGHT
I
Z
L
ZIGZAG
O
50
ASME P Material Numbers Explained ASME has
adopted their own designation for welding
processes, which are very different from the ISO
definitions adopted by EN24063.  
Designation Description
OFW Oxyfuel Gas Welding
SMAW Shielded Metal Arc Welding (MMA)
SAW Submerged Arc Welding
GMAW Gas Metal Arc Welding (MIG/MAG)
FCAW Flux Cored Wire
GTAW Gas Tungsten Arc Welding (TIG)
PAW Plasma Arc Welding
Straight polarity Electrode -ve Reverse
polarity Electrode ve
51
ASME F Numbers 
F Number General Description
1 Heavy rutile coated iron powder electrodes - A5.1 E7024
2 Most Rutile consumables such as - A5.1 E6013
3 Cellulosic electrodes such as - A5.1 E6011
4 Basic coated electrodes such as A5.1 E7016 and E7018
5 High alloy austenitic stainless steel and duplex - A5.4 E316L-16
6 Any steel solid or cored wire (with flux or metal)
2X Aluminium and its alloys
3X Copper and its alloys
4X Nickel alloys
5X Titanium
6X Zirconium
7X Hard Facing Overlay
Note- X represents any number 0 to 9 
52
ASME A Numbers  These refer to the chemical
analysis of the deposited weld and not the parent
material.  They only apply to welding procedures
in steel materials.  
A1 Plain unalloyed carbon manganese steels.
A2 to A4 Low alloy steels containing Moly and Chrome Moly
A8 Austenitic stainless steels such as type 316.
53
ASME Welding Positions   Note the welding
progression, (vertically upwards or downwards),
must always be stated and it is an essential
variable for both procedures and performance
qualifications.  Welding Positions For Groove
welds-
Welding Position Test Position ISO and  EN
Flat 1G  PA
Horizontal 2G PC
Vertical Upwards Progression 3G PF
Vertical Downwards Progression 3G PG
Overhead 4G PE
Pipe Fixed Horizontal 5G PF
Pipe Fixed _at_ 45 degrees Upwards 6G HL045
Pipe Fixed _at_ 45 degrees Downwards 6G JL045
54
G for Groove Welds F for Fillet Welds
55
  • G
  • for Groove Welds
  • F
  • for Fillet Welds

56
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57
 Welding Positions For Fillet welds-
Welding Position Test Position ISO and  EN
Flat (Weld flat joint at 45 degrees) 1F PA
Horizontal  2F PB
Horizontal Rotated 2FR PB
Vertical Upwards Progression 3F PF
Vertical Downwards Progression 3F PG
Overhead 4F PD
Pipe Fixed Horizontal 5F PF
58
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59
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60
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61
Multiple-pass layers.
Weld layer sequence
62
Welding Positions QW431.1 and QW461.2 Basically
there are three inclinations involved. Flat,
which includes from 0 to 15 degrees inclination
15 - 80 degrees inclination Vertical, 80 - 90
degrees For each of these inclinations the weld
can be rotated from the flat position to
Horizontal to overhead. 
63
Effects of expansion and contraction
64
CONTROLLING DISTORTION
65
HEAT AFFECTED ZONE
66
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67
LIQUID STATE PROCESSES
  • Partial melting and fusion of joint
  • Physical and mechanical changes taking place
  • Can be with application of pressure or by
    addition of filler material
  • Prior to joining, PREPARATION TO BE DONE
  • STANDARDS- AWS ASTM-
  • TYPES OF GROOVES, JOINTS

NITC
68
OXY ACETYLENE WELDING (OAW)
69
Oxyacetylene Welding (OAW)
  • The oxyacetylene welding process uses a
    combination of oxygen and acetylene gas to
    provide a high temperature flame.

70
Oxyacetylene Welding (OAW)
  • OAW is a manual process in which the welder must
    personally control the the torch movement and
    filler rod application
  • The term oxyfuel gas welding outfit refers to all
    the equipment needed to weld.
  • Cylinders contain oxygen and acetylene gas at
    extremely high pressure.

71
Typical Oxyacetylene Welding (OAW) Station
72
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73
  • STEPS for OAW
  • PREPARE THE EDGES AND MAINTAIN PROPER POSITION-

    .(USE OF FIXTURES, CLAMPS)
  • OPEN ACETYLENE AND IGNITE
  • OPEN OXYGEN AND ADJUST FLAME
  • HOLD TORCH AT ABOUT 45O AND FILLER METAL AT 30 TO
    40 O
  • TOUCH FILLER ROD TO JOINT AND CONTROL MOVEMENT
  • SINGLE BEAD MADE

74
  • FOR DEEP JOINTS, MULTIPLE PASSES
  • CLEANING EACH WELD BEAD IS IMPORTANT
  • EQUIPMENT- WELDING TORCH- VARIOUS SIZES AND
    SHAPES
  • CYLINDERS DIFFERENT THREADS, ANCHORED AND NOT
    DROPPED

75
  • CAPABILITIES
  • LOW COST. MANUAL AND HENCE SLOW
  • PORTABLE, VERSATILE AND ECONOMICAL FOR LOW
    QUANTITY AND REPAIR WORKS
  • FOR ALL FERROUS AND NONFERROUS METALS
  • LIMITATIONS THICKNESS lt 6 MM
  • SKILL ESSENTIAL---FOR PIPE, PRESSURE VESSELS,
    LOAD BEARING STRUCTURAL MEMBERS

76
Oxygen Cylinders
  • Oxygen is stored within cylinders of various
    sizes and pressures ranging from 2000- 2640 PSI.
    (Pounds Per square inch)
  • Oxygen cylinders are forged from solid armor
    plate steel. No part of the cylinder may be less
    than 1/4 thick.
  • Cylinders are then tested to over 3,300 PSI
    using a (NDE) hydrostatic pressure test.

77
Oxygen Cylinders
  • Cylinders are regularly re-tested using
    hydrostatic (NDE) while in service
  • Cylinders are regularly chemically cleaned and
    annealed to relieve jobsite stresses created by
    handling .

78
Cylinder Transportation
  • Never transport cylinders without the safety caps
    in place
  • Never transport with the regulators in place
  • Never allow bottles to stand freely. Always chain
    them to a secure cart or some other object that
    cannot be toppled easily.

79
Oxygen Cylinders
  • Oxygen cylinders incorporate a thin metal
    pressure safety disk made from stainless steel
    and are designed to rupture prior to the cylinder
    becoming damaged by pressure.
  • The cylinder valve should always be handled
    carefully

80
Pressure Regulators for Cylinders
  • Reduce high storage cylinder pressure to lower
    working pressure.
  • Most regulators have a gauge for cylinder
    pressure and working pressure.

81
Pressure Regulators for Cylinders
  • Regulators are shut off when the adjusting screw
    is turn out completely.
  • Regulators maintain a constant torch pressure
    although cylinder pressure may vary
  • Regulator diaphragms are made of stainless steel

82
Pressure Regulators Gauges Using a Bourdon
movement
  • Gas entering the gauge fills a Bourdon tube
  • As pressure in the semicircular end increases it
    causes the free end of the tube to move outward.
  • This movement is transmitted through to a curved
    rack which engages a pinion gear on the pointer
    shaft ultimately showing pressure.

83
Regulator Hoses
  • Hoses are are fabricated from rubber
  • Oxygen hoses are green in color and have right
    hand thread.
  • Acetylene hoses are red in color with left hand
    thread.
  • Left hand threads can be identified by a grove in
    the body of the nut and it may have ACET
    stamped on it

84
Check Valves Flashback Arrestors
  • Check valves allow gas flow in one direction only
  • Flashback arrestors are designed to eliminate the
    possibility of an explosion at the cylinder.
  • Combination Check/ Flashback Valves can be placed
    at the torch or regulator.

85
Acetylene Gas
  • Virtually all the acetylene distributed for
    welding and cutting use is created by allowing
    calcium carbide (a man made product) to react
    with water.
  • The nice thing about the calcium carbide method
    of producing acetylene is that it can be done on
    almost any scale desired. Placed in
    tightly-sealed cans, calcium carbide keeps
    indefinitely. For years, miners lamps produced
    acetylene by adding water, a drop at a time, to
    lumps of carbide.
  • Before acetylene in cylinders became available in
    almost every community of appreciable size
    produced their own gas from calcium carbide.

86
Acetylene Cylinders
  • Acetylene is stored in cylinders specially
    designed for this purpose only.
  • Acetylene is extremely unstable in its pure form
    at pressure above 15 PSI (Pounds per Square Inch)
  • Acetone is also present within the cylinder to
    stabilize the acetylene.
  • Acetylene cylinders should always be stored in
    the upright position to prevent the acetone form
    escaping thus causing the acetylene to become
    unstable.

87
Acetylene Cylinders
  • Cylinders are filled with a very porous substance
    monolithic filler to help prevent large pockets
    of pure acetylene form forming
  • Cylinders have safety (Fuse) plugs in the top and
    bottom designed to melt at 212 F (100 C)

88
Acetylene Valves
  • Acetylene cylinder shut off valves should only be
    opened 1/4 to 1/2 turn
  • This will allow the cylinder to be closed quickly
    in case of fire.
  • Cylinder valve wrenches should be left in place
    on cylinders that do not have a hand wheel.

89
Oxygen and Acetylene Regulator Pressure Settings
  • Regulator pressure may vary with different torch
    styles and tip sizes.
  • PSI (pounds per square inch) is sometimes shown
    as PSIG (pounds per square inch -gauge)
  • Common gauge settings for cutting
  • 1/4 material Oxy 30-35psi Acet 3-9 psi
  • 1/2 material Oxy 55-85psi Acet 6-12 psi
  • 1 material Oxy 110-160psi Acet 7-15 psi
  • Check the torch manufactures data for optimum
    pressure settings

90
Regulator Pressure Settings
  • The maximum safe working pressure for acetylene
    is 15 PSI !

91
Typical torch styles
  • A small welding torch, with throttle valves
    located at the front end of the handle. Ideally
    suited to sheet metal welding. Can be fitted with
    cutting
  • attachment in place of the welding head shown.
    Welding torches of this general design are by far
    the most widely used. They will handle any
    oxyacetylene welding job, can be fitted with
    multiflame (Rosebud) heads for heating
    applications, and accommodate cutting attachments
    that will cut steel 6 in. thick.
  • A full-size oxygen cutting torch which has all
    valves located in its rear body. Another style of
    cutting torch, with oxygen valves located at the
    front end of its handle.

92
Typical startup procedures
  • Verify that equipment visually appears safe IE
    Hose condition, visibility of gauges
  • Clean torch orifices with a tip cleaners (a
    small wire gauge file set used to clean slag and
    dirt form the torch tip)
  • Crack (or open) cylinder valves slightly allowing
    pressure to enter the regulators slowly
  • Opening the cylinder valve quickly will Slam
    the regulator and will cause failure.

93
Typical startup procedures
  • Never stand directly in the path of a regulator
    when opening the cylinder
  • Check for leaks using by listening for Hissing
    or by using a soapy Bubble solution
  • Adjust the regulators to the correct operating
    pressure
  • Slightly open and close the Oxygen and Acetylene
    valves at the torch head to purge any atmosphere
    from the system.

94
Typical startup procedures
  • Always use a flint and steel spark lighter to
    light the oxygen acetylene flame.
  • Never use a butane lighter to light the flame

95
Flame Settings
  • There are three distinct types of oxy-acetylene
    flames, usually termed
  • Neutral
  • Carburizing (or excess acetylene)
  • Oxidizing (or excess oxygen )
  • The type of flame produced depends upon the ratio
    of oxygen to acetylene in the gas mixture which
    leaves the torch tip.

96
TYPES of FLAMES
  • Neutral- with inner cone(30400C-33000C), outer
    envelope, (21000C near inner cone, 12600C at
    tip)- high heating
  • Reducing- Bright luminous inner cone, acetylene
    feather, blue envelope
  • Low temperature, good for brazing, soldering,
    flame hardening
  • Hydrogen, methyl acetylene, propadiene also used
    as fuel.
  • Oxidising- pointed inner cone, small and narrow
    outer envelope
  • Harmful for steels, good for Cu- Cu based alloys

NITC
97
OXY ACETYLENE WELDING (OAW)Types of Flames
Neutral
Reducing
Oxidising
high heating
low temperature
good for Cu- Cu alloys
98
Pure Acetylene and Carburizing Flame profiles
99
Neutral and Oxidizing Flame Profiles
100
Flame definition
  • The neutral flame is produced when the ratio of
    oxygen to acetylene, in the mixture leaving the
    torch, is almost exactly one-to-one. Its termed
    neutral because it will usually have no
    chemical effect on the metal being welded. It
    will not oxidize the weld metal it will not
    cause an increase in the carbon content of the
    weld metal.
  • The excess acetylene flame as its name implies,
    is created when the proportion of acetylene in
    the mixture is higher than that required to
    produce the neutral flame. Used on steel, it will
    cause an increase in the carbon content of the
    weld metal.
  • The oxidizing flame results from burning a
    mixture which contains more oxygen than required
    for a neutral flame. It will oxidize or burn
    some of the metal being welded.

101
Quiz time
  • The regulator diaphragm is often made from
    _______?
  • A reinforced rubber
  • B malleable iron
  • C tempered aluminum
  • D stainless steel

102
Quiz time
  • The hose nuts for oxygen and acetylene differ
    greatly, because the acetylene hose nut has.
  • A a left hand thread.
  • B has a grove cut around it. C may have
    ACET stamped on it.
  • D All of the above.

103
Quiz time
  • An oxygen cylinder must be able to withstand a
    ________ pressure of 3300 psi (22753 kPa) to be
    qualified for service. A atmospheric
  • B hydrostatic
  • C hydroscopic
  • D vapor

104
Quiz time
  • Why is the area above 15 psig often marked with a
    red band on a acetylene low pressure regulator ?
  • Answer
  • Acetylene pressure above 15 psig is unstable and
    should not be used

105
Quiz time
  • True or False ?
  • A flint and steel spark lighter is the generally
    used to light the oxyacetylene flame.
  • Answer True

106
Quiz time
  • Acetylene cylinder fuse plugs melt at a
    temperature of ________ F or 100C
  • Answer
  • 212F

107
Quiz time
  • What is the maximum safe working gauge pressure
    for acetylene gas?
  • A 8 psig (55 kPa)
  • B 15 psig (103 kPa)
  • C 22 psig (152 kPa)
  • D 30 psig (207 kPa)

108
Quiz time
  • The color of and oxygen hose on a oxyacetylene
    welding outfit is ______?
  • Answer
  • Green/Blue

109
Quiz time
  • The type of safety device is used on a oxygen
    cylinder.
  • A A fusible plug
  • B A check valve
  • C A pressure safety disk
  • D A spring loaded plug

110
Quiz time
  • True or False ?
  • The regulator is closed when the adjusting screw
    is turned out.
  • Answer True

111
Quiz time
  • The color of acetylene hose on a oxyacetylene
    welding outfit is ______?
  • Answer
  • Red

112
Quiz time
  • No part of an oxygen cylinder walls may be
    thinner than _______?
  • A 1/4in (6.4 mm)
  • B 3/8in (9.5 mm)
  • C 3/16in (4.8 mm)
  • D 7/32in (5.6 mm)

113
Quiz time
  • To prevent the occurrence of flashbacks, a
    ________ should be installed between either the
    torch and hoses or regulators and hoses.
  • A a two way check valve.
  • B flame screen.
  • C flashback arrestor.
  • D three way check valve.

114
Quiz time
  • What type of safety device is used on a acetylene
    cylinder.
  • A A spring loaded plug
  • B A pressure safety disk
  • C A fusible plug
  • D A check valve

115
Quiz time
  • Mixing _______ and water will produce acetylene
    gas.
  • A calcium carbide
  • B potassium carbonate
  • C carbon dioxide
  • D acetylene carbide

116
LIQUID STATE PROCESS
  • PARTIAL MELTING
  • BY STRIKING AN ARC
  • AFTER THE INVENTION OF ELECTRICITY
  • HOW ARC STRUCK?
  • ARC COLUMN THEORY

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118
ARC WELDING
119
  • ARC WELDING
  • ELECTRIC ARC
  • WITHOUT ADDITIONAL
    EXTERNAL SOURCE
  • AUTOGENEOUS NONCONSUMABLE-
    CONSUMABLE
  • CARBON ARC WELDING (CAW) - OLDEST
  • METALLIC ARC WELDING (MAW)
  • COATING MATERIALS
  • ARC TO BE CREATED BY ELECTRICITY
  • WHEN? WITH THE INVENTION OF AC DYNAMO IN 1877

120
BEGINNING IN 1881- TO CONNECT PLATES OF STORAGE
BATTERY 1886- BUTT WELDING TECHNIQUE WAS
DEVELOPED
BUTTED, CLAMPED HIGH CURRENT PASSED AT THE
JOINT, RESISTANCE OF METAL TO ELECTRIC CURRENT
PRODUCES HIGH HEAT- PIECES FUSED
121
ARC WELDING- MELTING AND FUSING OF METAL BY
ELECTRODES
  • 1ST BY N.V. BERNADO USING CARBON ELECTRODES

CONSISTANTLY IMPROVED 1895 N.G. SLAVIANOFF
USED METALLIC ELECTRODES 1905 BARE ELECTRODES
COATEDSHIELDING--- (SAW) PORTABLE AND AUTOMATIC
WELDING MACHINES
122
  • ARC WELDING PROCESSES
  • USE OF CONSUMABLE ELECTRODES
  • SHIELDED METAL ARC WELDING (SMAW)
  • SIMPLEST AND MOST VERSATILE
  • ABOUT 50 OF INDUSTRIAL WELDING BY THIS PROCESS
  • CURRENT- 50 TO 300 A, lt 10 KW
  • AC/DC USED
  • FOR THICKNESSES UPTO 19 20 MM

123
SHIELDED METAL ARC WELDING (SMAW)
124
  • Shielded metal arc welding (SMAW),
  • Also known as Manual Metal Arc (MMA) welding
  • Informally as stick welding
  • is a manual arc welding process that uses
    a consumable electrode coated in flux to lay the
    weld.
  • An electric current, in the form of either
    alternating current or direct current from a
    welding power supply, is used to form an electric
    arc between the electrode and the metals to be
    joined.

125
ELECTRICAL / IONIC THEORY IONS FROM ANODE TO
CATHODE, AS METAL IONS ARE VE CHARGED
ARC COLUMN THEORY
  • TOUCH AND THEN ESTABLISH A GAP
  • TO BALANCE THE ATOMIC STRUCTURE
  • IONS COLLIDE WITH GAS MOLECULES
  • PRODUCES A THERMAL IONISATION LAYER
  • IONISED GAS COLUMN AS HIGH RESISTANCE CONDUCTOR
  • ON STRIKING CATHODE, HEAT GENERATED
  • TERMED AS IONIC THEORY
  • NOT COMPLETE IN EXPLAINING ARC COLUMN THEORY
  • THUS, ELECTRON THEORY

ANODE
DC
CATHODE -
126
ELECTRON THEORY IONS FROM ANODE TO CATHODE AS
METAL IONS ARE VE CHARGED -VELY CHARGED
ELECTRONS DISSOCIATED FROM CATHODE MOVE OPPOSITE
WITH HIGH VELOCITY
ARC COLUMN THEORY
ANODE
DC
(MASS- 9.1x 10-28 gm) CAUSES HEAT IN ARC
COLUMN RELEASES HEAT ENERGY IN STRIKING THE
ANODE CALLED ELECTRON IMPINGEMENT AND IONIC
BOMBARDMENT
CATHODE -
127
ANODE
HIGH HEAT
ELECTRON IMPINGEMENT
LOW HEAT
MEDIUM HEAT
IONIC BOMBARDMENT
CATHODE -
128
MAGNETIC FLUX THEORY
  • THE COLUMN NOT FLAIRING
  • DUE TO THE FLUX LINES AROUND THE ARC
    COLUMN.
  • (Right hand Thumb Rule)
  • THIS COMPLETES THE ARC COLUMN THEORY

129
POLARITYAC
  1. Currents higher than those of DCRP can be
    employed (400 A to 500 Afor 6 mm electrode)
  2. Arc cleaning of the base metal
  3. Normal penetration
  4. Equal heat distribution at electrode and job
  5. Electrode tip is colder as compared to that in
    DCRP
  6. Average arc voltage in argon atmosphere is 16V

130
DCRP
  1. Currents generally less than 125 amps (upto 6 mm
    dia electrodes) to avoid overheating
  2. 2/3rd heat at electrode and 1/3rd at the job
  3. Least penetration
  4. Average arc voltage on argon atmosphere is 19V
  5. Chances of electrode overheating, melting and
    losses
  6. Better arc cleaning action

131
DCSP
  1. Welding currents upto 1000 amps can be employed
    for 6 mm electrodes
  2. 33.33 heat is generated at the electrode and
    66.66 at the job.
  3. Deep penetration
  4. Average arc voltage in an argon atmsphere is 12 V
  5. Electrode runs colder as compared to AC or DCRP
  6. No arc cleaning of base metal

132
  • METALLURGY OF WELDING
  • During joining, localized heating occurs.
  • This leads to metallurgical and physical changes
    in materials welded.
  • Hence, study of
  • Nature of welded joint
  • Quality and property of welded joint
  • Weldability of metals
  • Methods of testing welds
  • Welding design
  • Process selection- important

.
133
(3) Heat Affected Zone (HAZ)

(2) Fusion Zone
(1) Base Metal
Structures (1) SMALL (2) MEDIUM (3)
LARGE Properties of (2) and (3) important
134
  • Cooling of Bead-
  • similar to a casting in mould, which is metallic
    here. Cooling is slow Hence the structure is
    coarse and Strength toughness and ductility low.
  • But use of proper electrodes improves these.
  • The purpose of coating the electrode is to
    achieve the improved properties. If without,
    nitrides and oxides of base metal form and these
    result in weak and brittle nature.
  • With coating, properties comparable with base
    metal achieved.

135








Gas shield
Arc column makes CRATER on striking the surface-
Temperature above 1500 C
Flux impurities- less dense. Floats as
SLAG Slag prevents heat loss- makes an evenly
distribution of heat radiation.
Preheating to receive the molten metal at an
elevated temperature and modify the structure.
Not for M.S. Locked in stresses due to heating
and cooling- to be relieved by PEENING, or other
heat treatment processes.
136
  • MAGNETIC ARC BLOW -- FOR AC SUPPLY.
  • Current through conductor- magnetic Flux lines
    perpendicular to current flow- apply Right hand
    Thumb Rule.
  • Three areas of magnetic field
  • Arc 2. Electrode 3. Work piece, when ground.
  • Forward pull of Arc column results, called as
    Magnetic Arc Blow.

137
EQUIPMENT
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139
  • As the weld is laid, the flux coating of the
    electrode disintegrates, giving off vapors that
    serve as a shielding gas and providing a layer of
    slag, both of which protect the weld area from
    atmospheric contamination.
  • Because of the versatility of the process and the
    simplicity of its equipment and operation,
    shielded metal arc welding is one of the world's
    most popular welding processes.

140
PURPOSE OF COATING
  • Gives out inert or protective gas- shields
  • Stabilizes the arc- by chemicals
  • Low rate consumption of electrode- directs arc
    and molten metal
  • Removes impurities and oxides as slag
  • Coatings act as insulators- so narrow grooves
    welded
  • Provide means to introduce alloying elements
  • Bare electrodes - carbon- more conductive- slow
    consumption in welding

141
ELECTRODE COATING INGREDIENTS
  • Slag forming ingredients- silicates of sodium,
    potassium, Mg, Al, iron oxide, China clay, mica
    etc.
  • Gas shielding- cellulose, wood, starch, calcium
    carbonate
  • De-oxidising elements- ferro manganese, ferro
    silicon- to refine molten metal
  • Arc stabilizing calcium carbonate, potassium
    silicate, titanates, Mg silicate etc.
  • .Alloying elements- ferro alloys, Mn, Mo., to
    impart special properties
  • Iron powder- to improve arc behaviour, bead
    appearance
  • Other elements - to improve penetration, limit
    spatter, improve metal deposition rates,

142
WELD POSITIONS
  • FLAT HORIZONTAL VERTICAL OVERHEAD

NITC
143
WELD MOVEMENTS
STRAIGHT
I
Z
L
ZIGZAG
O
144
WELDING TECHNIQUES
  • FOREHAND BACKHAND

THIN Same direction torch Heat concentrated away
from bead Even flow, rippled design
THICK Opposite direction torch Heat concentrated
on bead Broad bead
145
  • It dominates other welding processes in the
    maintenance and repair industry, used extensively
    in the construction of steel structures and in
    industrial fabrication.
  • The process is used primarily to weld iron and
    steels (including stainless steel) but aluminum,
    nickel and copper alloys can also be welded with
    this method.
  • Flux-Cored Arc Welding (FCAW) , a modification
    to SMAW is growing in popularity

146
Various welding electrodes and an electrode holder
147
SAFETY PRECAUTIONS
  • Uses an open electric arc, so risk of burns to
    be prevented by protective clothing in the form
    of heavy leather gloves and long sleeve jackets.
  • The brightness of the weld area can lead arc eye,
    in which ultraviolet light causes the
    inflammation of the cornea and can burn the
    retinas of the eyes.
  • Welding helmets with dark face plates to be worn
    to prevent this exposure

148
  • New helmet models have been produced that feature
    a face plate that self-darkens upon exposure to
    high amounts of UV light
  • To protect bystanders, especially in industrial
    environments, transparent welding curtains often
    surround the welding area.
  • These are made of a polyvinyl chloride plastic
    film, shield nearby workers from exposure to the
    UV light from the electric arc, but should not be
    used to replace the filter glass used in helmets.

149
Arc eye, also known as arc flash or welder's
flash or corneal flash burns, is a painful
condition sometimes experienced by welders who
have failed to use adequate eye protection. It
can also occur due to light from sunbeds, light
reflected from snow (known as snow blindness),
water or sand. The intense ultraviolet light
emitted by the arc causes a superficial and
painful keratitis. Symptoms tend to occur a
number of hours after exposure and typically
resolve spontaneously within 36 hours. It has
been described as having sand poured into the
eyes.
  • ARC EYE

150
SignsIntense lacrimation Blepharospasm
Photophobia Fluorescein dye staining will
reveal corneal ulcers under blue light
  • Management
  • Instill topical anaesthesia
  • Inspect the cornea for any foreign body
  • Patch the worse of the two eyes and prescribe
    analgesia
  • Topical antibiotics in the form of eye drops or
    eye ointment or both should be prescribed for
    prophylaxis against infection

151
SUBMERGED ARC WELDING (SAW)
152
CONTROL PANEL
153
Submerged Arc Welding (SAW)
  • Is a common arc welding process.
  • A continuously fed consumable solid or tubular
    (metal cored) electrode used.
  • The molten weld and the arc zone are protected
    from atmospheric contamination by being
    submerged under a blanket of granular fusible
    flux.
  • When molten, the flux becomes conductive, and
    provides a current path between the electrode and
    the work

154
  • Normally operated in the automatic or mechanized
    mode.
  • Semi-automatic (hand-held) SAW guns with
    pressurized or gravity flux feed delivery are
    available.
  • The process is normally limited to the 1F, 1G, or
    the 2F positions (although 2G position welds have
    been done with a special arrangement to support
    the flux). Deposition rates approaching 45 kg/h
    have been reported this compares to 5 kg/h
    (max) for shielded metal arc welding.
  • Currents ranging from 200 to 1500 A are commonly
    used currents of up to 5000 A have been used
    (multiple arcs).

155
  • Single or multiple (2 to 5) electrode wire
    variations of the process exist
  • SAW strip-cladding utilizes a flat strip
    electrode (e.g. 60 mm wide x 0.5 mm thick).
  • DC or AC power can be utilized, and combinations
    of DC and AC are common on multiple electrode
    systems.
  • Constant Voltage welding power supplies are most
    commonly used, however Constant Current systems
    in combination with a voltage sensing wire-feeder
    are available.

156
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157
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158
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159
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160
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161
SAW
  • Fusion Welding Process
  • Automatic / Semi Automatic
  • Arc Between Consumable Electrode And Work
  • Arc Covered Under granular Flux
  • Wire / Electrode Continuously Fed To Weld Pool
  • Wire / Arc Under Flux Moves Along The Groove
  • Wire, BM Flux Close to Arc Melt Under Flux
  • On Cooling Weld Metal Solidifies
  • Molten Flux Forms Thick Slag Coating On Weld

162
SAW
Hopper
Power Source
Flux

Wire


Slag
Weld
Flux
Base Metal
Arc


163
Flux For SAW
  • Sodium Chloride
  • Potassium Chloride
  • Titanium Dioxide
  • Sodium Silicate
  • Deoxidizing Agents

164
Types Of Flux
  • Fused Flux
  • Agglomerated Flux
  • Neutral Flux
  • Active Flux

165
Types Of Flux
  • Neutral Flux
  • -Wire compatible to base metal
  • - Single flux suitable for several material
  • Active Flux
  • Single flux suitable for specific application
  • Wire may be different from basemetal
  • To be welded within the recommended parameters

166
Function Of Flux In SAW
  • Stabilizes Arc
  • Prevents contamination of weld metal
  • Cleans the weld from unwanted impurities
  • Increases Fluidity of molten metal
  • Generates inert gas shielding while metal
    transfers
  • Forms slag after melting covers weld
  • Allows deposited metal to cool slowly
  • Compensates alloying elements Within the weld
  • Eliminates spatter generation
  • Helps in even uniform bead finish

167
Baking Requirements For Flux
  • Spread the loose Flux in a Tray Of baking Oven
  • Identify The Tray With The Quality/Grade Of Flux
  • Bake Tray in an Oven Between 300 C to 350 C
  • Baking Time 2 Hrs to 3 Hrs
  • Reduce the temperature to 100 C to 150 C
  • Hold the Flux at this temperature till use

168
Why Baking Flux?
  • To remove the moisture (H2O)
  • To avoid possible cracking of weld
  • due to H2

169
How Does Moist Flux Generate Crack Within Weld?
  • Moist Flux introduce atomic hydrogen at high
    temperature in weld
  • On cooling, atomic hydrogen try to form molecules
  • The reaction results in stresses and fine cracks
  • Cracks occur within hardened metal - HAZ
  • Known as Hydrogen Embrittlement or Under Bead
    Crack or Delayed Crack

170
Reuse Of Flux
  • Flux May Be Reused Provided
  • - Weld Not Highly Critical In Impact /
    Chemistry
  • - Reuse Limited To Maximum Twice
  • - All Slag Particles Are sieved Removed
  • - Rebaked If not Remained In Hot
  • - Minimum 50 Fresh Flux Well Mixed
  • - Customer Spec. Doesn't Prohibit The Same

171
Types Of Power Source
  • Thyrester DC
  • Rectifier DC
  • Motor Generator DC
  • Transformer - AC

172
Characteristic Of Power Source
Machine welding Machine welding
Drooping Cons. A Linear Cons. V
V V
V1
V1
V2
V2
A
A
A1
A2
A2
A1
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SAW Wire - Electrode
  • Consumable Electrode / Wire
  • Layer Wound On Spool / Coil
  • CS LAS Wires Coated with Cu
  • Conducts Current and generates Arc
  • Chemistry Compatible To Base Metal
  • Grade Of Flux Can Be Same For CS LAS
  • Wire melts deposited as filler in joint

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Typical Welding Parameter
Sr no Wire Ø mm Current A Voltage V Speed mm/min Dep. Rate Per Arc Hr Wire Flux
1 1.6 200-300 22-26 750-1500 3 4 kgs CS wire Neutral Flux
2 2 250-350 24-26 750-1250 3- 4.5 kgs CS wire Neutral Flux
4 2.5 300-350 25-27 750-1250 4 4.5 kgs CS wire Neutral Flux
5 3 400-500 28-30 500-100 5 5.5 kgs CS wire Neutral Flux
6 4 550-650 30-32 400-750 5.5 - 7 kgs CS wire Neutral Flux
7 5 600-800 30-34 350-700 6 - 8 kgs CS wire Neutral Flux
175
Important Terminology used in Critical SAW
  • Preheating
  • Post Heating or Dehydrogenation
  • Intermediate Stress leaving
  • Inter pass Temperature
  • Post Weld Heat Treatment

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What Is Preheating?
  • Heating the base metal along the weld joint to a
    predetermined minimum temperature im
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