welding

A typical fusion weld joint consists of fusion zone, weld Fusion zone

HAZ UBMZ

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1. Arc Welding (AW)

? A fusion welding where the coalescence of the metals (base metals and filler) is achieved by the heat from electric arc.

?Productivity: Arc time ?Technical issues

–Electrodes –consumable and non-consumable electrodes

–Arc Shielding –To shield the arc

from the surrounding gas. Helium

and argon are typically used. Flux

does a similar function.–Power source –dc for all metals or

ac for typically steels

?Heat loss due to convection, conduction and radiation

melted

volume metal the is generated heat total the is efficiency melting the is efficiency

heat the is where 2121V H f f V U H f f H m w ==0.7

Gas Tungsten Arc Welding 0.95Submerged Arc Welding 0.9Flux-cored Arc Welding

0.9Gas Metal Arc Welding

0.9Shield Metal Arc Welding

f 1Arc Weldin

g Process 12

AW with Consumable Electrodes

?

Shielded Metal Arc Welding (SMAW)

– A consumable electrode –a filler metal rod coated with chemicals for flux and shielding (230-460mm long and 2.5-9.4mm in diameter)

–The filler metal must be comparable with base metals.

–Current: 30-300A and Voltage: 15-45V –Cheaper and portable than oxyfuel welding –Less efficient and variation in current due to the change in length of consumable electrodes during the process.

?Gas Metal Arc Welding (GMAW)

–Use a bare consumable electrode

–Flooding the arc with a gas which depends on the metal

–No slag build-up and higher deposition rate than SMAW

–Metal Inert Gas (MIG) or CO 2welding

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AW with Consumable Electrodes

?Flux-cored Arc Welding (FCAW)

–Use a continuous consumable tube with flux and others such as deoxidizer and alloying elements –Two types

?Self-shielded –flux has an ingredient for shielding

?Gas-shielded –external gas

–Produce high quality weld joint

?Electrogas Welding (EGW)

–Flux-cored or bare electrode with external shield gas and water-cooled molding shoes.

–Used in shipbuilding

?Submerged Arc welding (SAW)

–Shielding is provided by the granular flux

–Large structures

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AW with non-consumable Electrodes

?

Gas Tungsten Arc Welding (GTAW)

–Tungsten (Wolfram) Inert Gas (TIG) Welding –With or without a filler metal –Tungsten melts at 3410°C

–Shielding gas: argon, helium or a mixture

–

All metals (commonly Al and Stainless steels) in a wide range of thickness

–Slow and costly but high quality weld for thin sections

?Plasma Arc Welding (PAW) –a special form of GTAW but with a constricted plasma gas to attain a higher temperature

?Carbon Arc Welding –Graphite is used as electrode

?

Stud Welding –for cookware, heat radiation fin.

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2. Resistance Welding Power source: heat generated:Resistance Welding Processes

Resistance spot welding (RSW)

Resistance seam welding (RSEW)Resistance projection welding (RPW)Heating by ?similar to FW but pressed ?High-frequency (induction and resistance) Rt I H =Force

-electrode Weld nugget

+ electrode 17

3. Oxyfueld gas Welding

?Oxyfuel gas weldings (OFW) –Use various fuels mixed with oxygen

?Oxyacetylene welding –A mixture of acetylene and oxygen

–Total heat: 55x106J/m 3

–Acetylene: odorless but commercial acetylene has a garlic order.

–Unstable at 1atm thus dissolved in acetone.

?Other gases

–MAPP (Dow), Hydrogen,

Propylene, Propane and Natural gas

Outer Envelope (1260°C)

Acetylene feather

(2090°C)Inner cone

(3480°C)

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Solid-state Welding Processes

Samurai sword high pressure Hot-pressure welding

Diffusion welding at 0.5T m

mechanical locking commonly used to bond two dissimilar metals, in particular to clad one metal 21Explosive, Friction & Ultrasonic

Welding

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37

Multiple lead wires on a printed circuit board(PCB)

A solder paste consists of solder powders in a flux binder, which is heated either using vapor phase reflow or infrared Tension

Shear

cleavage

peeling