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Arc welding:
Heat generated by electrons jumping an air gap
Causes the base metal and electrode to melt.
Shielded Metal Arc Welding:
SMAW
Uses flux covered electrodes or “sticks” to add filler metal to
The welding process.
The flux is a special coating that burns while the electrode
Is melting. This smoke keeps the atmosphere away from
The molten metal.
This type of welding is fairly inexpensive and most people
Can have some type of mastery.
SMAW works well on rusty metal.
Arc welders:
Produce a temperature of about 9,000 degrees F
Usually range from 20 –225 amperage output.
Duty cycle – refers to the number of minutes out of ten minutes
The welder can be operated continuously without the amperage
Output dropping.
Welding current produced:
Electricity or current is simply the flow of electrons. There are two
Basic types of electricity, Alternating current and Direct current
Direct Current: (DC)
The electrons flow only in one direction.
Polarity:
The direction in which the electrons flow in DC current.
60% of the heat in an electric arc is generated on the positive
Side of the air arc.
Straight: In Straight (DC-)polarity the Electrode is Negative (SEN)
The base metal is positive, deep penetration in it
Reverse: In Reverse (DC+) polarity the Electrode is Positive (REP)
The base metal is negative, shallow penetration
Alternating Current:
(AC)
Electrons flow back and forth.
Polarity:
There is no actual polarity that can be set in AC welding.
Because the electrons flow back and forth the current is made
Us of 50% DC- and 50% DC+
Some welding machines are capable of producing both AC and DC
Welding current.
Welding cables:
Large diameter copper wire with a rubber coating
They are large so there is very little voltage drop for current flow,
And so they are a better ground than you are.
Ground Clamp:
Electrode holder:
Attaches to the base metal to provide a complete
Circuit for the welding machine
Holds the stick, it has grooves made in it to hold
The electrode in different positions.
It also helps complete the welding circuit
Sometimes called the “stinger”
Welding electrodes:
The production of quality electrodes was the key to commercial arc
Welding.
The first electrodes were metal rods with string wrapped around it
Rolled in flour. As the flour burned it pushed the atmosphere away.
By the 1930’s good electrodes were being produced
Before arc welding light metal was oxy-fuel gas welded and heavy
Metal was riveted.
There are many types of electrodes available today how can we tell
The difference between them?
National electrical Manufacturers Association (NEMA) color code
A color coding system that identifies electrodes by colored dots on
The end, base surface, and flux coating.
Most manufactures use the number coding system as well as the
NEMA system as it is easier for most people to understand.
American Welding Society (AWS) numerical code.
The most popular guide to selecting electrodes.
Electrodes are given numbers that correspond to their tensile strength,
Welding position, and type of current setting or penetration.
AWS welding rod code: