MECHENG236 - Welding

Question 1

Pros and Cons of welding

Answer 1

Advantages are: Can fabricate complex designs that are difficult to produce with any other process.
Relatively quick.
Virtually no limit to the size of components that can be produced.
Can join dissimilar parts where either side of the interface has unique and different properties, e.g. * Dissimilar steels
Disadvantages are:
Can be difficult or time consuming to inspect quality.
Skilled labour required when applied manually.
Disassembly difficult or impossible.
Heat can induce distortion in parts and/or affect composition of the material.
Parts may need post-welding heat treatment.

Question 2

Weld joint types

Answer 2

• Butt
• Tee
• Lap
• Corner
• Edge

Question 3

Designers main issues with welding

Answer 3

• Getting stress analysis right
• Communicating design intent fully and accuracy
• Ensuring finished product meets your specification
  o Main issues:
   Quality of the weld bead
   The metallurgy of the heat affected zone

Question 4

Effects of HAZ:

Answer 4

1. Localized hardening. 2. Residual stresses. 3. Reduction in mechanical properties. 4. Decreased resistance to corrosion and cracking. 5. Change in shape after welding.

Question 5

Welding distortion is caused by

Answer 5

the non-uniform expansion and contraction

Question 6

The extent of welding distortion will depend on various factors such as:

Answer 6

• Geometryof the joint. * Type of weld preparation. * Width or volume of the beam web/section. * Rate of heat input during welding process. * Volume of weld deposited.

Question 7

Factors to consider in weld design

Answer 7

Minimise number of parts to reduce preparation, assembly time, alignment issues and heat transfer.
Also ensure the welder can physically reach the weld!
-for avoiding crevice corrosion
-for galvanizing
-for alleviating distortion

Question 8

Welding Design for Galvanising

Answer 8

Components should not contain confined gas spaces – heating these gas volumes will cause sudden expansion and can destroy the part
Galvanising uses corrosive solutions, areas that cannot be drained during the process may remain contaminated and accelerated corrosion can start in these areas

Question 9

Designing to alleviate distortion

Answer 9

• Intermittent welding
• Minimum number of passes
• Welding near neutral surface
• Balancing welds around neutral axis