Welding

6/1/2009

Welding Jim Johnson Zach Kirsch Ross McKenzie

Topics to be Covered Welding Topics: „ MIG „ TIG „ Stick „ Diffusion „ Friction „ Explosion

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6/1/2009

MIG Welding „

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

MIG - History „

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Developed in 1940’s to weld aluminum, aluminum magnesium, and other non--ferrous alloys non Use in steel was originally limited by cost of Inert gas

– It the early 1950’s carbon dioxide was used as shielding gas for steel greatly reducing the cost

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Further developments through the 1960’s 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 –

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Controls C t l arc, gas, wire i feed f d

(2) Workpiece (3) Power Supply

-Typically constant voltage DC

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(4) Wire Feed Mechanism (5) Electrode – –

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Usually similar material as workpiece Contains small amounts of deoxidizing metals (Si, Mg, Al)

(6) Shielding Gas –

Typically argonargon-CO2 mix

MIG - Process „

Arc creates weld p pool to bond material – DC Constant Voltage with positively charged electrode – reverse polarity requires special electrode

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Shielding gas protects the weld pool from atmospheric gas effects g – Porosity and embrittlement

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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) R Required i d skill kill level l l is i relatively l ti l low Can weld many ferrous and non non-ferrous materials – Different results and requirements must be expected (shielding gas, technique, electrode, etc)

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Power of machine will determine what it can weld – More power – thicker material

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GMAW can be automated more easily than other methods

MIG - Industries „

Automotive – Almost exclusive

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Pressure Vessels Heavy rail and construction equipment

At Home – Easy and inexpensive

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Automobile/Agricultural repair

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TIG - Welding „

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T Tungsten t IInertt G Gas (TIG) or Gas Tungsten Arc Welding (GTAW) AC or DC Electric Arc Non--consumable Non tungsten electrode l d Shielding Gas Hand fed filler

TIG - History „

Early 1900’s 1900 s welding non--ferrous materials non was difficult – Reacted with air making welds weak and porous

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Process was improved in the 1930’s and 1940’s 1940 s – Gas shielding increased weld quality – AC machines allowed for high quality welds on aluminum and magnesium

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TIG - Equipment Welding Torch

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Di t shielding Directs hi ldi gas and d holds h ld electrode

Power Supply

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AC typically used for aluminum and magnesium DC with a negatively charged electrode is typically used for steels

Electrode

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Made from tungsten or tungsten alloys ISO standards for each alloy

Filler Rod Shielding Gas

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Argon is most common Helium is sometimes used when welding aluminum and copper

TIG - Process „

Arc creates weld pool to bond material – AC or DC used depending on base material

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Shielding gas protects the weld pool from atmospheric gas effects – Porosity and impurities

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Technique

– Requires q 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 „ „

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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

TIG - Industries „ „ „

Aircraft Spacecraft Bicycles

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Crack repair

– Aluminum wheels and engine blocks

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Shielded Metal Arc Welding (Stick Welding) „

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Common welding technique Stick is synonymous with coated electrode

http://atpwelding.com/welding.jpg

Basic Principles „

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

http://www.twi.co.uk/j32k/protected/band_3/jk2.html

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Coating „

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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

Advantages/Disadvantages Advantages: „ „ „ „

Simple Portable Versatile Inexpensive equipment q p

Disadvantages: „ „ „ „

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

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Diffusion Welding „

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Also known by: diffusion bonding, solid state bonding Can be used to join metals and ceramics that otherwise can’t be joined

http://www.turktoz.gazi.edu.tr/en_makale_files/image037.jpg

Diffusion Welding “Diffusion Diffusion Welding is a solid 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 „

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Two materials are heated and pressed upon one another Pressure causes heated atoms to diffuse into surface, creating a bond upon recrystalization D=D0e-(Q/KT)

Messler 1999

Equipment „

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A press is needed, 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 „ „

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“Perfect” weld possible Special material properties Even weld properties throughout material Close tolerances Expensive materials

Disadvantages „

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Only perpendicular surfaces Specially designed components Requires inert atmosphere Expensive

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_book/fig10-79.gif

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Types of Friction Welding „ „ „ „

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

Spin Welding „

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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 gy produced p byy the motor Requires circular joining points

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Linear Friction Welding „

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

Image: http://www.twi.co.uk/j32k/twiimages/spswksep99f9.gif Image: http://www.eurotradeglobal.com/content/1124976586.jpg

Friction Stir Welding „

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A cylindrical probe rotates and constant speed d and d fed f d 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/archive/2004/september/ photos/sept_i_tt.jpg

Image: http://www.hitachi-cable.co.jp/ICSFiles/afieldfile/2005/12/26/1_1.gif

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Friction Surfacing „

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Coating g of material applied pp 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 g g process p so problems associated with more traditional welding process are avoided

Image: http://www.frictec.co.uk/frictec-whatisfr.html

Advantages/Disadvantages „ „ „

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Fast jjoining g 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

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

Aerospace - Aluminum and Steel Nuclear - Copper and Steel

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Explosion Welding (EXW) „ „

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Solid state welding g process p 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 p g 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

Welding Process

Image:http://content.edgar-online.com/edgar_conv_img/2007/03/08/0001104659-07-017391_G57151FCI001.JPG

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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

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Brittle materials cannot be processed Only simple shapes - Plates and Cylinders

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Thickness of flyer plate is limited There are many safety concerns when storing and detonating explosives

Common BiBi-Metals Produced „ „ „ „ „ „ „

Copper pp 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_Publications/lsnotes/ls237/Images/ls237_t2.gif

Videos „

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http://video.google.com/videoplay?docid=http://video.google.com/videoplay?docid= p // g g / p y 7051110735654059178&q=friction+stir+welding&total=8&sta rt=0&num=10&so=0&type=search&plindex=0&hl=en http://video.google.com/videoplay?docid=8072096915190997 688&q=friction+welding&total=25&start=0&num=10&so=0&t ype=search&plindex=2&hl=en

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