general

Question 1

Outline three methods of preventing atmospheric contamination of the weld area.

Answer 1

Granular flux
Electrode flux coating
Argon/co2 gas
Oxy/acetylene flame

Question 2

Describe multi-run welding

Answer 2

When more than one weld is done in one place.

Question 3

Describe with a diagram the main features of an automatic welding process.

Answer 3

Explain MIG, Spot welding or seam welding

Question 4

What is porosity and why can it happen?

Answer 4

Porosity is the presence of air bubbles inside a welded joint. It can be caused by;
The presence of moisture in the weld
Cylinder out of gas
Presence of paint, oil or grease
Weld nozzle is not close enough to weld
Shielding gas has been blown away due to drafts.

Question 5

What is a slag inclusion and why can it happen?

Answer 5

This refers to slag becoming entrapped in the weld pool,
When slag gets caught in the weld pool and does not rise to the surface before solidifying.
Can be caused by welding temperature not hot enough, welding too fast or failure to remove all slag from underlying weld

Question 6

What is lack of penetration and why can it happen?

Answer 6

When the weld fusion is not very deep in the joint. Caused by lack of heat in the arc

Question 7

Describe two hazards which may be encountered in underwater welding.

Answer 7

Underwater welding adds the danger of being shocked, or producing a mixture of oxygen and hydrogen together in bubbles in the arc, which can lead to an explosion.

If a diver surfaces too fast, he is always in danger of getting the bends (severe pain injoints that is caused by not properly depressurizing).

Sharks and large ocean predators are always a potential threat when welding underwater, as well as the diving suit becoming damaged or the oxygen tanks becoming loose or emptied.

The ocean current can actually carry a welder off, which can result in disastrous consequences.

Nitrogen can build up in the diver’s blood and create deposits.

Of course, there is the most common death involved with water -drowning

Question 8

What are the advantages of multi-run welds?

Answer 8

A superior weld is produced as each weld has a post-heating effect on the previous run.(Steel cooled slowly results in a tougher weld)

Multi runs are less brittle than single runs, as successive layers have redefined the weld metal and multi runs will tend to anneal the hard zones.
Multi run welds will build up T –joints for strength.

The finished weld is stronger and more refined in structure than single run welds.