Solid state welding

What is solid-state welding?

A joining process where coalescence occurs due to pressure alone or a combination of heat (below melting point) and pressure, with no filler metal.

What are the advantages of solid-state welding (SSW)?

No melting or HAZ

minimal defect

entire interface bonding

good for dissimilar metals

preservation of material properties

What are the disadvantages of solid-state welding (SSW)?

Expensive equipment

significant surface preparation

limited to specific joint designs

thin materials

What are common solid-state welding processes?

Roll welding

friction welding

diffusion welding

ultrasonic welding

explosion welding

What is roll welding (cladding)?

A process where sheets are pressed through rolls under high pressure to produce solid-state welds through plastic deformation.

Why is surface preparation critical in roll welding?

To remove contaminants and oxides, allowing formation of nascent surfaces necessary for bonding.

What is the theory behind roll bonding?

Plastic deformation creates fresh, nascent surfaces by collapsing asperities and breaking oxides, promoting strong bonding.

What is friction welding (FRW)?

A solid-state welding process where heat is generated by friction between components followed by pressure application.

What are advantages of friction welding?

No melting

repeatable

no consumables

good mechanical properties

suitable for production

What are disadvantages of friction welding?

High equipment cost

one part must rotate

flash removal needed

upsetting reduces part length

limited to symmetric joints

What is friction stir welding (FSW)?

A variation of FRW using a rotating non-consumable probe to generate heat and stir materials without melting.

What is diffusion welding?

A process where welding occurs through diffusion of atoms across joint interface under heat and pressure.

What conditions affect diffusion welding?

Cleanliness

surface finish

temperature

pressure

time

plastic flow of at least one component

What are advantages of diffusion welding?

High strength joints

works with dissimilar metals and ceramics

minimal distortion

no degradation of base metal

What are disadvantages of diffusion welding?

High cost

long weld times

significant surface prep

doesn't work well with all metals (e.g. Ni).

What is ultrasonic welding (USW)?

A process using high-frequency vibration and moderate pressure to generate heat and weld at the interface.

What are advantages of ultrasonic welding?

Fast

low heat input

no consumables

minimal distortion

good for automation and soft metals

What are disadvantages of ultrasonic welding?

One part must be thin

limited to lap joints

mostly for soft metals

high equipment cost

What is explosion welding (EXW)?

A process where one metal plate is accelerated at high speed into another using an explosive, causing bonding through plastic deformation.

What are features of explosion welding?

No filler

no external heat

no diffusion; bonding occurs through metallurgical and mechanical interlocking at wavy interface.

What are advantages of explosion welding?

Strong bonds

low HAZ

can join almost any dissimilar metals

cost-effective for certain applications.

What are disadvantages of explosion welding?

Not suited for production

limited joint types

intensive surface prep

safety

licensing requirements for explosives.

What is the key difference between fusion and solid-state welding?

Fusion welding involves melting of materials; solid-state welding does not melt the base metals.

Why is surface preparation important in solid-state welding?

Clean, oxide-free surfaces are essential to form strong metallic bonds without melting.