Manual Metal Arc Welding (MMA)

Question 1

Explain the process of MMA welding briefly

Answer 1

In this process, an electric arc is formed and maintained between the work and the electrode. Intense heat from the arc melts the joint edges to form a weld pool, which solidifies to join the two parts.

Question 2

Explain the process of MMA welding in 4 steps

Answer 2

1. The operator holds an electrode holder, which clamps onto a consumable flux-coated filler electrode.
2. The stick is brought close to the metal and a hot electric arc is formed.
3. Flux and filler metal drop into the weld area from the stick.
4. Slag is created on top of the weld.

Question 3

Name the heat source for MMA welding

Answer 3

Electric arc

Question 4

What is the electrode in MMA welding?

Answer 4

The electrode is a metal wire covered by a coating.

Question 5

What happens to the flux-coated filler rod?

Answer 5

The metal is consumed in the process as a filler material, while the coating melts and performs the certain functions

Question 6

When the filler rod is melted, the coating melts and performs the following functions: List these functions

Answer 6

1. Chemicals in the coating form a gas that shields the weld pool against oxidisation.
2. The fluxing elements of the coating help the weld to form.
3. Slag forming elements in the coating combine with impurities in the weld pool to form a layer over the cooling weld run (slag).

Question 7

What does slag do? What happens to slag after cooling?

Answer 7

The slag protects against oxidisation and slows the cooling rate of the weld to prevent brittleness. It is chipped off after cooling.

Question 8

What are 3 pros of MMA welding

Answer 8

1. Easy to learn.
2. Slag layer slows down the cooling of weld to prevent brittle joints.
3. Slag layer means impurities have been removed.

Question 9

What are 4 cons of MMA welding?

Answer 9

1. Slag layer has to be chipped off after cooling.
2. Not suitable for light-gauge materials.
3. Produces a lot of fumes.
4. Welds short lengths as stick electrodes must be changed frequently.

Question 10

What must be labelled on a diagram for MMA welding?

Answer 10

power source, (flux coated consumable electrode), electrode, electrode holder, earth clamp