Welding

Question 1

What are the two main types of corrosion we are interested in with reference to Welding?

Answer 1

• Galvanic corrosion

- Crevice corrosion

Question 2

What are the three main considerations when designing for a welded assembly?

Answer 2

• Number of parts (should be designed with the fewest parts possible)
• Joint design (avoid forming crevices where corrosion may occur)
• Tolerancing (using weld material to fill gaps is not good practice and the parts should thus be toleranced correctly for proper fitting).
• Access (the welder or welding nozzle should be able to have proper access to the site of the weld).

Question 3

What are the four ways to avoid crevice corrosion?

Answer 3

• closed hollow profiles with small surfaces
• fully closed welds (preferably butt welds)
• slopes to avoid accumulation of deposits
• defined drainage systems

Question 4

What is the cause of welding distortion?

Answer 4

• Non-uniform expansion and contraction of the weld metal

- Microstructural change to parent metal, on solidification leading to volumetric strain

Question 5

What are four stress relieving methods?

Answer 5

• Vibratory stress relieving
• Peening (hammering)
• Post-weld treatment
• Preheating the components

Question 6

How to minimise distortion?

Answer 6

• Good fit of parts
• Try to place welds symmetrically/around neutral axis
• Equal thickness