9 El arco eléctrico
Introduction to Arc Welding with Coated Electrode
Overview of Electric Arc
- The course introduces arc welding with coated electrodes, part of the Electromechanical Engineering program at the Armed Forces University in Latacunga.
- An electric arc is defined as an electrical discharge between two conductors, creating a conductive path through ionized gas (plasma), resulting in light and heat.
Ionization Process
- Gases are normally insulators; they become conductive when ionized by separating atoms into ions and electrons.
- Atoms have equal numbers of electrons and protons. High temperatures can cause electrons to detach from atoms, leading to positive ions—a process known as ionization.
Structure of the Electric Arc
- The welding arc consists of three parts: cathode, anode, and plasma column. The cathode (negative terminal) emits electrons that become plasma.
- Both alternating current (AC) and direct current (DC) can be used for forming the electric arc. AC varies over time while DC maintains constant voltage and current.
Polarity in Welding
- In DC welding, polarity affects the connection: direct polarity connects the electrode to negative and workpiece to positive; reverse polarity does the opposite.
- Direct polarity results in narrow weld beads with high penetration but no cleaning effect on oxides; reverse polarity leads to wider beads with less penetration.
Effects of Magnetic Blow
- Alternating current reduces oxide cleaning effects due to changing polarities.