© pearson & gnu su-jin kim welding & joining manufacturing processes the fusion welded...

© Pearson & GNU Su-Jin Kim© Pearson & GNU Su-Jin Kim

Welding & JoiningWelding & JoiningManufacturing ProcessesManufacturing Processes

The Fusion Welded Joint

3 distinct zones of weld are:• base metal• heat-affected zone (HAZ)• fusion zone



Weld quality

• Discontinuities that affect weld quality are:1. Porosity• trapped gases, chemical reactions, contaminants2. Slag inclusions• Slag is trapped in the weld zone.



Weld quality

3. Incomplete fusion and incomplete penetration

4. Weld profile• Affects the strength and appearance of the weld.

5. Cracks



Design for Welding

http://www.youtube.com/watch?v=pVyYvcEqkcQ&feature=related



Ex) Design frame for welding



Ex) Welding

Gas metal arc welding



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



Solid State Welding

1. Cold Welding ( 냉간압점 )2. Ultrasonic Welding ( 초음파용접 )3. Friction Welding ( 마찰용접 )4. Diffusion Bonding ( 확산접합 )



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)



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

© 정하림 GNU



Vibration Welding

• Vibrate two plastic parts to be joined by friction heat

http://ma.gnu.ac.kr/vod/Joining/Vibration_welding_plastic.MP4



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



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



Brazing ( 경납접 ) & Soldering (연납접 )

• Solid base, liquid filler• Filler material: different composition, low melting point,

lower strength



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.



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.



Soldering



Design for Brazing



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.



Design for adhesive bonding

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