Welding

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Welding

• Jim Johnson
• Zach Kirsch
• Ross McKenzie

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Topics to be Covered

• Welding Topics
• MIG
• TIG
• Stick
• Diffusion
• Friction
• Explosion

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MIG Welding

• Metal Inert Gas (MIG) or Gas Metal Arc Welding
  (GMAW)
• DC or AC (rare) Electric Arc
• Consumable electrode
• Shielding Gas

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MIG - History

• Developed in 1940s to weld aluminum, magnesium,
  and other non-ferrous alloys
• Use in steel was originally limited by cost of
  Inert gas
• It the early 1950s carbon dioxide was used as
  shielding gas for steel greatly reducing the cost
• Further developments through the 1960s increased
  the versatility of the process
• Today GMAW is the most commonly used industrial
  welding process

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MIG - Equipment

• (1) Welding Torch
• Controls arc, gas, wire feed
• (2) Workpiece
• (3) Power Supply
• -Typically constant voltage DC
• (4) Wire Feed Mechanism
• (5) Electrode
• Usually similar material as workpiece
• Contains small amounts of deoxidizing metals (Si,
  Mg, Al)
• (6) Shielding Gas
• Typically argon-CO2 mix

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MIG - Process

• Arc creates weld pool to bond material
• DC Constant Voltage with positively charged
  electrode reverse polarity requires special
  electrode
• Shielding gas protects the weld pool from
  atmospheric gas effects
• Porosity and embrittlement
• Technique
• Simple electrode is fed automatically
• Torch is guided along weld area keeping a
  constant tip to workpiece distance

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MIG Capabilities

• Inexpensive machines (500)
• Required skill level is relatively low
• Can weld many ferrous and non-ferrous materials
• Different results and requirements must be
  expected (shielding gas, technique, electrode,
  etc)
• Power of machine will determine what it can weld
• More power thicker material
• GMAW can be automated more easily than other
  methods

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MIG - Industries

• Automotive
• Almost exclusive
• Pressure Vessels
• Heavy rail and construction equipment

• At Home
• Easy and inexpensive
• Automobile/Agricultural repair

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TIG - Welding

• Tungsten Inert Gas (TIG) or Gas Tungsten Arc
  Welding (GTAW)
• AC or DC Electric Arc
• Non-consumable tungsten electrode
• Shielding Gas
• Hand fed filler

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TIG - History

• Early 1900s welding non-ferrous materials was
  difficult
• Reacted with air making welds weak and porous
• Process was improved in the 1930s and 1940s
• Gas shielding increased weld quality
• AC machines allowed for high quality welds on
  aluminum and magnesium

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TIG - Equipment

• Welding Torch
• Directs shielding gas and holds electrode
• Power Supply
• AC typically used for aluminum and magnesium
• DC with a negatively charged electrode is
  typically used for steels
• Electrode
• Made from tungsten or tungsten alloys
• ISO standards for each alloy
• Filler Rod
• Shielding Gas
• Argon is most common
• Helium is sometimes used when welding aluminum
  and copper

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TIG - Process

• Arc creates weld pool to bond material
• AC or DC used depending on base material
• Shielding gas protects the weld pool from
  atmospheric gas effects
• Porosity and impurities
• Technique
• Requires two hands
• Torch is moved forward as filler rod is dipped
  into the weld pool
• Filler rod must remain inside the gas shield at
  all times
• Considered one of the most difficult welding
  methods low melt alloys increase difficulty

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TIG Capabilities

• Produces welds with very similar material
  properties of the base metal
• GTAW can produce high quality welds on materials
  such as aluminum, magnesium, titanium, copper,
  nickel, steel.
• Dissimilar materials copper and stainless at
  Zak
• Requires a skilled welder considered to be one
  of the more difficult types of welding
• Automation is possible, but not as common as GMAW
  due to the increase complexities

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TIG - Industries

• Aircraft
• Spacecraft
• Bicycles

• Crack repair
• Aluminum wheels and engine blocks

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Shielded Metal Arc Welding (Stick Welding)

• Common welding technique
• Stick is synonymous with coated electrode

http//atpwelding.com/welding.jpg
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Basic Principles

• Arc created between metal and electrode
• Metal is melted and coalesces to form weld

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Coating

• Different coatings for different applications
• Cellulosic, Rutile, and Limestone are common
• Coatings ease process through slag creation, and
  help to strengthen weld

http//www.twi.co.uk/j32k/twiimages/jk82f1.jpg
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Advantages/Disadvantages

• Advantages
• Simple
• Portable
• Versatile
• Inexpensive equipment

• Disadvantages
• Limited shielding
• Limited Deposition rates
• Usually done by hand
• Highly trained labor required

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Diffusion Welding

• Also known by diffusion bonding, solid state
  bonding
• Can be used to join metals and ceramics that
  otherwise cant be joined

http//www.turktoz.gazi.edu.tr/en_makale_files/ima
ge037.jpg
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Diffusion Welding

• Diffusion Welding is a solid-state welding
  process that produces a weld by the application
  of pressure at elevated temperature with no
  macroscopic deformation or relative motion of the
  work pieces.
• -American Welding Society description

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Basic Principles

• Two materials are heated and pressed upon one
  another
• Pressure causes heated atoms to diffuse into
  surface, creating a bond upon recrystalization
• DD0e-(Q/KT)

Messler 1999
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Equipment

• A press is needed, which can create pressure in a
  variety of ways
• Heat needs to be generated as well
• Fixturing system required

http//frisch-gmbh.de/images/sinteranlage.jpg
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Advantages/Disadvantages

• Advantages
• Perfect weld possible
• Special material properties
• Even weld properties throughout material
• Close tolerances
• Expensive materials

• Disadvantages
• Only perpendicular surfaces
• Specially designed components
• Requires inert atmosphere
• Expensive

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Friction Welding(FW)

• Solid state welding process
• Generates heat through friction between moving
  surfaces
• Heat in combination with lateral force called
  upset fuses two materials together
• First Patent for the development of FW was
  applied for in 1891

http//www.fortunecity.com/village/lind/247/weld_b
ook/fig10-79.gif
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Types of Friction Welding

• Spin Welding (inertia, rotational, inertial
  friction)
• Linear Friction Welding (LFW)
• Friction Stir Welding
• Friction Surfacing

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Spin Welding

• Involves the rotation of one surface relative to
  another while applying pressure along the axis of
  rotation
• Work pieces are held by chucks in spin welding
  machines
• Flywheel is used to store the energy produced by
  the motor
• Requires circular joining points

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Linear Friction Welding

• Lateral motion of surfaces rather than rotational
• Most surface can be joined

Image http//www.twi.co.uk/j32k/twiimages/spswkse
p99f9.gif
Image http//www.eurotradeglobal.com/content/1124
976586.jpg
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Friction Stir Welding

• A cylindrical probe rotates and constant speed
  and fed at a constant rate across the joint of
  two components
• Parts must be rigidly clamped together to prevent
  them from being forced apart from welding process

Image http//www.boeing.com/news/frontiers/archiv
e/2004/september/ photos/sept_i_tt.jpg
Image http//www.hitachi-cable.co.jp/ICSFiles/afi
eldfile/2005/12/26/1_1.gif
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Friction Surfacing

• Coating of material applied to surface of another
  material
• Rod composed of coating material is rotated under
  pressure across the surface of a separate
  material
• Closely resembles a hot forging process so
  problems associated with more traditional welding
  process are avoided

Image http//www.frictec.co.uk/frictec-whatisfr.h
tml
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Advantages/Disadvantages

• Fast joining times
• Small heat affected zones
• Joined with little preparation of surfaces
• Believed that flash carries away dirt and
  debris from surfaces
• Welding of dissimilar metals
• Aerospace - Aluminum and Steel
• Nuclear - Copper and Steel

• Uneconomical for short production runs due to
  high equipment costs
• Excludes delicate and intricate part

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Explosion Welding(EXW)

• Solid state welding process
• Plates are bonded through pressure created from a
  controlled detonation of explosive charge
• Originates from WWI when it was discovered that
  pieces of shrapnel were welded to armor plating
  on tanks
• Later development occurred in the decades
  following WWII
• Primarily used to clad inexpensive structural
  material with corrosion resistant material

Image http//www.metalwebnews.com/howto/explosive
-welding/fig1.gif
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Welding Process
Imagehttp//content.edgar-online.com/edgar_conv_i
mg/2007/03/08/0001104659-07-017391_G57151FCI001.JP
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Advantages/Disadvantages

• Large surfaces may be welded
• Produces a high quality bond
• Low cost
• Simple
• Little surface preparation required
• Dissimilar metals can be welded

• Brittle materials cannot be processed
• Only simple shapes
• - Plates and Cylinders
• Thickness of flyer plate is limited
• There are many safety concerns when storing and
  detonating explosives

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Common Bi-Metals Produced

• Copper to Steel
• Nickel to steel
• Aluminum to steel
• Tungsten to steel
• Titanium to steel
• Copper to aluminum
• Other

SS/Al Ring
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Commercially Available Combinations
Chart http//www.aps.anl.gov/Facility/Technical_P
ublications/lsnotes/ls237/Images/ls237_t2.gif
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Videos

• http//video.google.com/videoplay?docid-705111073
  5654059178qfrictionstirweldingtotal8start0
  num10so0typesearchplindex0hlen
• http//video.google.com/videoplay?docid8072096915
  190997688qfrictionweldingtotal25start0num
  10so0typesearchplindex2hlen