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MEC130 > Resistance & Solid State Welding > Flashcards

Resistance & Solid State Welding Flashcards

1
Q

What is Cold Welding used for?

A

To join small workpieces made of soft, ductile metals

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2
Q

What are the applications of resistance welding?

A

Sheet metal fabrication

Automotive body assembly

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3
Q

What does the shape of the welded joint depend on on Friction Welding?

A

Rotational speed and axial pressure applied

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4
Q

What is the frequency of oscillation for Ultrasonic Welding?

A

10 kHz - 75 kHz

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5
Q

What are the applications of Cold Welding?

A

Welding wire stock (splicing wire together)

Some electrical connections work in the same way

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6
Q

What are the advantages of Friction Welding?

A

Does not require consumable electrodes, shileding gases or flux

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7
Q

In friction welding, what does the size of the weld zone depend on?

A

The amount of heat generated
The thermal conductivity of the materials
The mechanical properties of the materials at elevated temperatures

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8
Q

Describe Diffusion Welding/Bonding

A

Occurs when surfaces are held in contact under sufficient pressure and time at elevated temperature
The bonding mechanism is atomic diffusion

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9
Q

List the steps required for resistance weldng

A

Pressure applied
Current on
Current off, pressure on
Pressure released, weld nugget produced at a lap joint

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10
Q

What does a solid state process mean?

A

No melting

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11
Q

What is important for an efficient operation in Ultrasonic Welding?

A

Proper coupling between the transducer and the tip

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12
Q

What causes plastic deformation at the interface of the two components and what are the effects?

A

Shearing stresses

Allows good contact
produces a strong solid-state bond
Breaks up oxide films and contaminants

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13
Q

What is friction welding also known as?

A

Stir Welding

Spin Welding

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14
Q

What are the advantages of Explosive Welding?

A

The bond strength is high

Ability to join numerous combinations of dissimilar metals

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15
Q

What does Cold Welding produce?

A

A weak brittle joint e.g. the bonding of aluminium and steel

Best bond is obtained with two similar metals

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16
Q

What does atomic diffusion promote under low pressure and elevated temperature?

A

Void shrinkage

Grain boundary migration to form a metallurgical bond

17
Q

What are the applications of Friction Welding?

A

Joins wide variety of materials, in particular solid or tubular parts to provide good strength joint

18
Q

Which process is Friction Welding technically a type of?

A

Forging because of plastic deformation

19
Q

What are the applications of Diffusion Welding/Bonding?

A

Titanium welding in aerospace industry

20
Q

Describe resistance welding

A

Heat required for welding is produced by electrical resistance across two components to be joined

21
Q

For Ultrasonic Welding, what is the temperature of the weld zone?

A

1/3 - 1/2 of the melting points of the metal joined
Neither melting nor fusion takes place
In certain situations the temperature generated can be sufficiently high to cause metallurgical changes in the weld zone

22
Q

What are the advantages of Ultrasonic Welding?

A

Versatile and reliable

Can be used with a wide variety of metals (dissimilar metallic workpieces, non-metallic workpieces)

23
Q

What are the applications of Explosive Welding?

A

High strength joints between aluminium, copper and stainless steel
Corrosion resistant claddings on mild steel substrates

24
Q

What are the solid state processes?

A 
Cold Welding
Ultrasonic Welding
Friction Welding
Explosion Welding
Diffusion Welding/Bonding
25
Q

What’s the disadvantage of resistance welding?

A

Complex and expensive equipment

26
Q

What are the advantages of Diffusion Welding/Bonding?

A

Ability to join dissimilar metals

Furnaces with inert/protective atmospheres can be used to produce high quality joints

27
Q

What is the most common resistance welding method?

A

Resistance Spot Welding

28
Q

What are the applications of Ultrasonic Welding?

A

Joining of plastics
Joining dissimilar metallic workpieces
Joining non-metallic workpieces

29
Q

What is Method Two of Friction Welding?

A

Workpiece remains stationary
Rotating tool forced onto joint area
Material plastically deforms and fuses together

30
Q

Outline Explosive Welding

A

Pressure is applied by detonating a layer of explosive that has been placed over one of the components being joined
The bottom sheet of metal is positioned on a rigid base/anvil
The top sheet is inclined to it with a small open angle between the surfaces to be joined

31
Q

What does the quality of the bond depend on for Diffusion Welding/Bonding?

A

Condition of the materials
Pressure
Temperature & time at temperature

32
Q

Describe the detonation in Explosive Welding

A

Explosive material is detonated in a progressive fashion beginning where the two surfaces touch
A compressive stress wave sweeps across the surface of the plates
Surface films are liquefied or scarfed off the materials and are jetted out of the interface
The clean metal surfaces are joined together under high contact pressure

33
Q

Describe the process of Ultrasonic Welding

A

The surfaces of two components are subjected to a static normal force and oscillating shearing (tangential) stresses
The shearing stresses are applied by the tip of a transducer

34
Q

Describe the process of Cold Welding

A

Pressure is applied to the workpiece either through dies or rolls
Plastic deformation takes place
It is necessary that at least one, but preferably both parts be ductile
Prior to welding, the interface is thoroughly cleaned

35
Q

What are the advantages of resistance welding?

A

Does not require consumable electrodes, shielding gases or flux

36
Q

What’s Method One of Friction Welding

A

One component remains stationary
Other is placed in a chuck/collet and is rotated at a constant high speed
The two components to be joined are brought into contact under increasing force. Pressure at the interface and the resulting friction produce sufficient heat for a strong joint to form
Flashing removed by grinding

37
Q

What are the applications of Ultrasonic Welding?

A

Lap welding of sheet, foil, and thin wire (automotive and electronics industries)
Packaging with foils
Seam welding - Welding tip is replaced with rotating disk

MEC130 (8 decks)

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