© pearson & gnu su-jin kim welding & joining manufacturing processes the fusion welded...
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The Fusion Welded Joint
3 distinct zones of weld are:• base metal• heat-affected zone (HAZ)• fusion zone
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Weld quality
• Discontinuities that affect weld quality are:1. Porosity• trapped gases, chemical reactions, contaminants2. Slag inclusions• Slag is trapped in the weld zone.
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Weld quality
3. Incomplete fusion and incomplete penetration
4. Weld profile• Affects the strength and appearance of the weld.
5. Cracks
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Design for Welding
http://www.youtube.com/watch?v=pVyYvcEqkcQ&feature=related
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Ex) Design frame for welding
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Ex) Welding
Gas metal arc welding
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Problem of Fusion Welding
• Composition change• Cavity, inclusion• Grain growth, phase transformation• Residual stress, crack
• Most failures start at heat affected zone• Sharpness of variation of heat affected zone may be
reduced by preheating• When C is more than 0.3%, Martensite may form
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Solid State Welding
1. Cold Welding ( 냉간압점 )2. Ultrasonic Welding ( 초음파용접 )3. Friction Welding ( 마찰용접 )4. Diffusion Bonding ( 확산접합 )
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Cold Welding ( 냉간압접 )
• Localized pressure is applied to mating faces of parts through dies or rolls.
• Used to join small workpieces made of soft and ductile metals.
Roll welding• Pressure for long pieces or continuous strips is applied
through a pair of rolls.
Rolls
Separating agent (graphite)
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Ultrasonic Welding ( 초음파용접 )• Ultrasonic vibration of transducer & Pressure
Temperature rise to 0.3~0.5 melting point.• Restricted to thin, small, delicate parts like electric
components.
Mass
Force
Couplingsystem
Tip
Workpiece
Anvil
Direction ofvibration
Powersupply
AC
Transducer DC
polarization supply
Transducer
Toolholder
Roller
Workpieces
Support
RollerWorkpiecesSupport
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Vibration Welding
• Vibrate two plastic parts to be joined by friction heat
http://ma.gnu.ac.kr/vod/Joining/Vibration_welding_plastic.MP4
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Friction Welding ( 마찰용접 )
• Heat required is generated from friction at the interface of the 2 members being joined.
http://www.youtube.com/watch?v=-aEuAK8bsQg&p=9B6D9EAE75875D9D Friction Welding
http://ma.gnu.ac.kr/vod/Joining/Friction_Welding.WMV Friction Welding
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Diffusion Bonding ( 확산접합 )
• Diffusion bonds two different materials in high pressure, elevated temperature, long time.
• High bond strength, slow process.• Good for Ti, superalloy (Aircraft components)
Copper - Stainless Aluminum - Stainless
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Brazing ( 경납접 ) & Soldering (연납접 )
• Solid base, liquid filler• Filler material: different composition, low melting point,
lower strength
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Brazing ( 경납접 )• Filler metal is placed between faying surfaces where the
temperature is raised to melt the filler metal.• Workpieces must melt in the weld area for fusion.• Clearance is important as it affects the strength of the
brazed joint.
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Soldering ( 연납접 )
• Filler metal (solder) fills the joint by capillary action.• Can be used to join various metals and to thicken parts.• Temperatures are low and have a low strength as they
are for load-bearing structural members.• Solders are tin-lead alloys.
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Soldering
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Design for Brazing
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Adhesive Bonding
• Numerous components and products can be joined and assembled.
• Adhesive are required to be strong and tough, resistance to fluids, chemicals and environmental degradation.
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Design for adhesive bonding