Fit-up refers to
Aligning and holding parts before welding
Polishing after welding
Grinding edges after welding
Painting the surface
Incorrect fit-up can cause
Misalignment and defects
More shine on weld
Less colour change
Better joint strength
Backing strips in welding are used to
Support molten metal at root
Increase welding speed
Improve surface colour
Reduce arc length
Root gap is provided to
Ensure penetration of weld metal
Reduce filler metal
Increase current
Reduce distortion
Tack welds are used to
Hold parts temporarily before final welding
Increase final weld size
Reduce arc voltage
Join plastic parts
Surface cleaning before welding removes
Rust, oil, grease, and dirt
Shape of joint
Weld bead
Paint colour
Wire brushing is used for removing
Loose rust and scale
Oil stains only
Paint completely
Deep cracks
Pickling uses
Acid solution to remove scale and rust
Sand to clean edges
Paint remover
Heat treatment
Solvent cleaning removes
Oil and grease
Mill scale
Rust
Paint
Grinding is used to
Smooth and clean edges
Increase surface hardness
Colour the surface
Decrease thickness intentionally
Moisture on plates before welding can cause
Porosity in welds
Stronger welds
Better appearance
Reduced arc length
Chipping hammer is used for
Removing slag after welding
Cutting edges before welding
Aligning plates
Cleaning with solvent
Sand blasting cleans
Large surfaces quickly
Only small edges
Paint from plastics
Moisture from steel
If oil is left on the joint surface, it may cause
Blow holes
Extra shine
More penetration
Higher strength
Proper surface cleaning ensures
Better weld quality and strength
Higher welding current
More spatter
Colour change
Arc welding works on the principle of
Resistance heating
Electric arc heat
Induction heating
Solar heat
Arc temperature in welding is about
1500°C
3500°C–4000°C
600°C
10,000°C
The unit of electric current is
Volt
Ampere
Ohm
Watt
The voltage required for SMAW is usually
6–10 V
20–30 V
50–60 V
100 V
Current in arc welding can be
AC or DC
Only AC
Only DC
Only pulsed
Ohm’s law states that
V = I × R
V = I / R
V = R / I
V = I² × R
In arc welding, higher current generally
Increases penetration
Decreases penetration
Reduces heat
Improves cooling
Open Circuit Voltage (OCV) of welding transformer is
50–100 V
10–15 V
150–200 V
500 V
Polarity in DC welding affects
Heat distribution between electrode and workpiece
Colour of weld bead
Weight of electrode
Voltage reading
In arc welding, resistance is important because
It controls current flow
It changes plate thickness
It increases electrode length
It removes slag
