Chapter 12. Joining and Fastening Processes · 2018-01-30 · Fusion Welding ( ) Melting together...

M2794.001800 M A T E R I A L A N D M A N U F A C T U R I N G P R O C E S S E S

Chapter 12. Joining and Fastening

Processes

Sung-Hoon Ahn

School of Mechanical and Aerospace Engineering

Seoul National University

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Prof. Ahn, Sung-Hoon

Quiz (1)

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Quiz (2)

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Introduction (1)

Fusion Welding ( )

Melting together and coalescing

materials by means of heat, usually

supplied by electrical or high-energy

means.

Solid-state Welding ( )

Joining takes place without fusion.

Adhesive Bonding ( )

Mechanical fastening ( )

Fasteners, bolts, nuts, rivets, etc.

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Introduction (2)

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Arc-Welding Processes: Consumable Electrode (1)

Shielded metal-arc welding (SMAW, )

50A ~ 300A (~10kW)

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Submerged arc welding (SAW)

Flux - lime, silica, manganese oxide, calcium fluoride

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Gas metal-arc welding (GMAW)

Ar, He, CO2 (inert gas)

Known as metal inert gas welding (MIG)

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Flux-cored arc welding (FCAW)

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Arc-Welding Processes: Non-consumable Electrode (1)

Gas tungsten-arc welding (GTAW)

Known as TIG (Tungsten inert gas) welding

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Arc-Welding Processes: Non-consumable Electrode (2)

Plasma-arc welding (PAW)

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Laser-beam welding (LBW)

Good for high aspect ratio

Vacuum is not required.

Electron-beam welding (EBW)

Generating X-rays

High welding quality

High-Energy-Beam Welding

Nd:YAG laser with fiber-optic delivery

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Fusion-Welded Joint (1)

Base metal

Heat-affected zone (HAZ)

Fusion zone

Note that the grains form

parallel to the heat flow.

similar to the dendrite in a cast

structure

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Fusion-Welded Joint (2)

Heat-affected zone

Cold-worked base metal

Heat applied during welding recrystallizes the elongated grains.

Grains close to the weld metal grow and this grain growth will result in a

region which is softer and has less strength.

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Residual Stresses

Stress relieving

Preheating

Lower cooling rate

Lower magnitude of

thermal stresses

(by reducing the E of

metals being welded)

Reducing shrinkage &

crack

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Cold Welding & Ultrasonic Welding

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Friction Welding

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Resistance Welding (1)

Resistance spot welding

RtIH 2

(s)current theof timeflow

)( resistance

(A)current

(J) generatedheat

t

R

I

H

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Resistance Welding (2)

Resistance seam welding

Resistance projection welding

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Explosive welding (폭발용접)

Joined by high kinetic energy

Detonation speed : 2400~3600m/s

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Brazing ( )

The temperature is raised to melt the filler ( ) metal, but not the workpiece.

Filler metals generally melt above 450 C.

Fluxes( ) : in order to prevent oxidation and to remove oxide films from

workpiece surface.

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Brazed joints

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Soldering ( )

From 2006, lead cannot be used

Filler metals melt below

450 C.

Fluxes are used.

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Adhesive bonding (접착)

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Adhesives (접착제)

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Mechanical fastening (기계적이음)

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Failure modes of riveted joint

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Other methods of fastening

Seaming

Crimping

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Snap-in fasteners

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Design considerations (1)

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Chapter 12. Joining and Fastening Processes · 2018-01-30 · Fusion Welding ( ) Melting together...

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Transcript of Chapter 12. Joining and Fastening Processes · 2018-01-30 · Fusion Welding ( ) Melting together...