A stick welder, also called a shielded metal arc welder, joins metals by using an electric arc to melt a metal electrode and the workpiece. The arc is extremely hot, often several thousand degrees Celsius, so it can create a molten weld pool in steel within seconds. Stick welding matters because it is rugged, portable, and widely used for construction, repair, pipelines, farm equipment, and structural steel.
Understanding the machine helps students connect electricity, heat transfer, materials science, and safe workshop practice.
Key Facts
- Electrical power input is P = VI, where P is power in watts, V is voltage, and I is current.
- Heat energy delivered over time is E = Pt = VIt, ignoring losses.
- A short, steady arc length helps keep voltage and heat input stable.
- The coated electrode supplies filler metal and produces shielding gas plus slag to protect the hot weld.
- Direct current electrode positive, DCEP, usually gives deeper penetration than direct current electrode negative, DCEN.
- Duty cycle is the fraction of a 10 minute period a welder can operate without overheating, such as 60% meaning 6 minutes welding and 4 minutes cooling.
Vocabulary
- Arc
- An arc is a bright electrical discharge through ionized gas between the electrode and the workpiece.
- Electrode
- An electrode is a coated metal rod that carries current and melts to add filler metal to the joint.
- Weld pool
- The weld pool is the small region of molten metal formed where the arc heats the joint.
- Slag
- Slag is the solid protective layer formed from melted electrode coating on top of the cooling weld.
- Duty cycle
- Duty cycle is the percentage of a 10 minute interval that a welder can run at a rated current before it must cool.
Common Mistakes to Avoid
- Using too long an arc, which raises voltage, increases spatter, and makes the weld bead unstable.
- Choosing the wrong current setting, which can cause poor penetration if too low or burn-through and excess spatter if too high.
- Forgetting to clamp the work lead to clean metal, which increases electrical resistance and can make the arc hard to start.
- Removing slag before the weld has solidified, which can damage the bead and expose hot metal before it is ready.
Practice Questions
- 1 A stick welder operates at 24 V and 120 A while welding. What electrical power is being delivered to the arc, in watts?
- 2 A welder has a 40% duty cycle at 180 A. During a 10 minute interval, how many minutes can it weld and how many minutes should it cool?
- 3 A student notices that increasing the arc length makes the arc louder and the bead more uneven. Explain why a longer arc can reduce weld quality.