Resistance & Solid State Welding Flashcards
What is Cold Welding used for?
To join small workpieces made of soft, ductile metals
What are the applications of resistance welding?
Sheet metal fabrication
Automotive body assembly
What does the shape of the welded joint depend on on Friction Welding?
Rotational speed and axial pressure applied
What is the frequency of oscillation for Ultrasonic Welding?
10 kHz - 75 kHz
What are the applications of Cold Welding?
Welding wire stock (splicing wire together)
Some electrical connections work in the same way
What are the advantages of Friction Welding?
Does not require consumable electrodes, shileding gases or flux
In friction welding, what does the size of the weld zone depend on?
The amount of heat generated
The thermal conductivity of the materials
The mechanical properties of the materials at elevated temperatures
Describe Diffusion Welding/Bonding
Occurs when surfaces are held in contact under sufficient pressure and time at elevated temperature
The bonding mechanism is atomic diffusion
List the steps required for resistance weldng
Pressure applied
Current on
Current off, pressure on
Pressure released, weld nugget produced at a lap joint
What does a solid state process mean?
No melting
What is important for an efficient operation in Ultrasonic Welding?
Proper coupling between the transducer and the tip
What causes plastic deformation at the interface of the two components and what are the effects?
Shearing stresses
Allows good contact
produces a strong solid-state bond
Breaks up oxide films and contaminants
What is friction welding also known as?
Stir Welding
Spin Welding
What are the advantages of Explosive Welding?
The bond strength is high
Ability to join numerous combinations of dissimilar metals
What does Cold Welding produce?
A weak brittle joint e.g. the bonding of aluminium and steel
Best bond is obtained with two similar metals
What does atomic diffusion promote under low pressure and elevated temperature?
Void shrinkage
Grain boundary migration to form a metallurgical bond
What are the applications of Friction Welding?
Joins wide variety of materials, in particular solid or tubular parts to provide good strength joint
Which process is Friction Welding technically a type of?
Forging because of plastic deformation
What are the applications of Diffusion Welding/Bonding?
Titanium welding in aerospace industry
Describe resistance welding
Heat required for welding is produced by electrical resistance across two components to be joined
For Ultrasonic Welding, what is the temperature of the weld zone?
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
What are the advantages of Ultrasonic Welding?
Versatile and reliable
Can be used with a wide variety of metals (dissimilar metallic workpieces, non-metallic workpieces)
What are the applications of Explosive Welding?
High strength joints between aluminium, copper and stainless steel
Corrosion resistant claddings on mild steel substrates
What are the solid state processes?
Cold Welding Ultrasonic Welding Friction Welding Explosion Welding Diffusion Welding/Bonding
What’s the disadvantage of resistance welding?
Complex and expensive equipment
What are the advantages of Diffusion Welding/Bonding?
Ability to join dissimilar metals
Furnaces with inert/protective atmospheres can be used to produce high quality joints
What is the most common resistance welding method?
Resistance Spot Welding
What are the applications of Ultrasonic Welding?
Joining of plastics
Joining dissimilar metallic workpieces
Joining non-metallic workpieces
What is Method Two of Friction Welding?
Workpiece remains stationary
Rotating tool forced onto joint area
Material plastically deforms and fuses together
Outline Explosive Welding
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
What does the quality of the bond depend on for Diffusion Welding/Bonding?
Condition of the materials
Pressure
Temperature & time at temperature
Describe the detonation in Explosive Welding
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
Describe the process of Ultrasonic Welding
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
Describe the process of Cold Welding
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
What are the advantages of resistance welding?
Does not require consumable electrodes, shielding gases or flux
What’s Method One of Friction Welding
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
What are the applications of Ultrasonic Welding?
Lap welding of sheet, foil, and thin wire (automotive and electronics industries)
Packaging with foils
Seam welding - Welding tip is replaced with rotating disk
