Joining

Question 1

Challenges in liquid state welding

Answer 1

• composition changes (changing the chemical construct)
• any dirt on the metal during will introduce weakens
• porosity forming (gases bubbles forming)
• residual stresses (distortion and cracks)
• failures usually happen in HAZ not the weld its self

Question 2

What are different types of joints

Answer 2

• butt
• corner
• tee
• lap
• edge

Question 3

List solid state welding methods:

Answer 3

- forge welding
Deformation in hot condition (heat hammer)
- cold welding (ductile metals)
Localised pressure applied (no heat, in vacuum, only small parts)
- diffusion welding (super-alloys, aircraft parts)
Heat + pressure applied = bond (diffusion + –> - )
- friction welding (drive shafts)
Rotational friction = heat
- ultra sonic welding ( foils, electronic parts, plastics)
Vibration + pressure = heat
**- high (radio) frequency welding ** (to make pipes, close the loop)
Vibration + pressure = heat
- explosive welding (cladding material, corrosive resistance)
Explosion accelerates top plate into bottom welding them together