Fusion Welding part 2

What are the three main methods of shielding a weld?

Fluxes

separate flux feed (e.g., SAW)

gas shielding (e.g., GTAW, GMAW).

Why is weld protection important?

Hot metals react with oxygen, nitrogen, and hydrogen, which can weaken or embrittle the weld.

What is hydrogen cracking?

A defect caused by hydrogen absorption in the weld, especially in steels, leading to delayed cracking.

What types of energy sources are used in fusion welding?

Electrical

chemical

gas

radiation.

What are consumable electrode processes?

SMAW, SAW, GMAW, FCAW, EGW, ESW.

What are non-consumable electrode processes?

GTAW (gas-tungsten arc welding)

plasma arc welding

carbon arc welding

stud welding

What is Shielded Metal Arc Welding (SMAW) or stick welding?

A manual welding process using a flux-coated consumable electrode

What are advantages of SMAW?

Portable

low cost

works on many metals

no shielding gas needed

What are disadvantages of SMAW?

Requires high skill

slow due to frequent electrode changes not ideal for thin materials.

What is Gas Metal Arc Welding (GMAW) or MIG/MAG?

A semi-automatic or automatic process using a wire electrode and shielding gas

What are advantages of GMAW?

Fast

produces little slag

high-quality welds

suitable for automation.

What are disadvantages of GMAW?

Expensive equipment

bulky torch

requires surface preparation

What is Flux-Cored Arc Welding (FCAW)?

A process using a tubular wire filled with flux; can be self-shielded or gas-shielded.

What are advantages of FCAW?

High deposition rates, tolerant to drafty conditions, good for steels and structural work.

What are disadvantages of FCAW?

High fume production, slag removal required, expensive filler wire.

What is Submerged Arc Welding (SAW)?

A process where the arc is submerged under a blanket of granular flux; used for large structural welds.

What are advantages of SAW?

Very high deposition rate

minimal fumes

no arc flash

customisable welds

What are disadvantages of SAW?

Limited positions (mostly flat)

complex equipment

not suitable for thin materials

What is Gas Tungsten Arc Welding (GTAW) or TIG?

uses a non-consumable tungsten electrode and inert gas for shielding

What are advantages of GTAW?

High-quality

clean welds

good for thin materials

complex geometries

What are disadvantages of GTAW?

Slow

expensive

requires skilled operator

risk of tungsten inclusions

What is Resistance Welding (RW)?

A fusion welding process using heat from electrical resistance and pressure to form a weld.

What is Resistance Spot Welding (RSW)?

A resistance welding process where fusion occurs at a single point using opposing electrodes.

What are advantages of Resistance Welding?

No filler metal

high production rate

easy to automate

consistent results.

What are disadvantages of Resistance Welding?

High initial cost, limited to lap joints, not suitable for all materials or thicknesses.

What considerations are important in fusion welding?

Shielding protection

HAZ microstructure

residual stresses

need for pre/post heat treatment

What is the Heat Affected Zone (HAZ)?

The area near the weld that did not melt but underwent microstructural changes due to heat.

What is an electrical arc in welding?

A sustained electrical discharge between two electrodes, generating intense heat to melt metals.

What are the principal process groups in fusion welding?

Arc welding

resistance welding

gas welding

radiation welding

How are arc welding electrodes categorised?

Consumable (e.g., SMAW, GMAW)

non-consumable (e.g., GTAW).

what is an electrical arc?

sustained electrical discharge through ionised gas between two electrodes

the primary heat source in most arc welding processes

occurs when voltage is high enough to ionise gas

produces extremely high temperatures