Arc Welding
By: John Templeton
Objectives
Identify and explain safety practices and
procedures as related to electric and oxyfuel welding
Identify equipment used in SMAW welding
Explain the SMAW process
Identify the 2 types of welding current and
machines
Arc Welding
The process of fusing two or more pieces of
metal together by using the heat produced from
an electric arc welding machine.
Otherwise known as SMAW (shielded metal arc
welding)
– The electrode produces a gas which shields the arc
from the atmosphere as the electrode melts.
SMAW Advantages
Scrap metal can used make repairs
Repairs can be made quickly before a problem
becomes severe
Metal repair and construction can be
accomplished more economically
Arc welders can be used to accomplish jobs like
cutting, piercing, gouging and beveling
Welding Equipment
Welding hood
Welding gloves
Electrodes
Welding machine
Chipping hammer
Wire brush
Welding Equipment
Welding leads
Electrode holder
Ground clamp
Alternating Current Welding
AC (alternating
current)
– Most common
– 180 Ampere or 225
Ampere between 220240 volts
– Can handle most
agriculture and
construction jobs
– Alternating flow of
electrons
SMAW
Direct Current Welding
DC (direct current)
– Can produce direct current of both straight
(negative) and reverse (positive) polarity.
– Polarity is the direction in which the current
flows across the arc.
– Makes a continuous flow of electrons
Straight/Reverse Polarity
Straight Polarity (DC-)
– Work is positive and
electrode is negative
– Used to weld thinner
metals
– Shallow penetration
Reverse Polarity (DC+)
– Work is negative and
electrode is positive
– Used to weld thicker metals
– Deeper penetration
Types of Welding Machines
AC machine
– Only works on
alternating current (+-)
Types of Welding Machines
AC/DC
– Can run on three different types of current
Alternating
Direct current + (reverse polarity)
Direct current – (straight polarity)
This machine will have a rectifier switch which
will allow it to switch between the three
Or the leads will need to be placed in certain
parts of the machine.
Types of Welding Machines
AC/DC Machines
– Are capable of
handling most
agriculture and
construction.
– Are the most popular.
– Allow the operator to
weld metal of all
thickness.
Types of Welding Machines
Machines can either
be gasoline engine
driven or they can be
powered be
electricity.
Duty Cycle
Tells the operator how long his machine
can operate without causing damage to
the machine.
It is how long a machine can run in ten
minute intervals, and is measured by a
percentage.
Duty Cycle
If a machine has a duty cycle of 25%, for
every ten minutes the machine is operated
you can only weld for 2.5 minutes.
The remaining 7.5 minutes must be spent
letting the machine idle.
Electrodes
All major manufacturers of welding
electrodes use the American Welding
Society (AWS) code of specifications.
Each company makes basically the same
quality which is established by the AWS.
Electrodes
Electrodes are classified according to type
of coating, composition of the weld metal
and operating characteristics.
The numbering system is started with “E”
for electrode and then followed by a four
digit number
Electrodes
Each number in the four number sequence has a
specific meaning.
60XX = Tensile Strength in pounds (X 1,000)
60,000 lbs per square inch
XX1X = Welding Position
1 =All
2 = Flat and Horizontal
XXX1 = Polarity
1,3,4,8=AC or DC Reverse
2 = AC or DC straight
0 = DC Reverse
3 = Flat
Electrodes
What is the classification of an E 7018?
–E
– 70
–1
–8
Electrode Diameter
Electrodes are also measured by their diameter
(the diameter of the electrode without including
the flux.
The diameter is measured in thirty-seconds of
an inch.
Always use an electrode ½ the size of you base
metal
– What does this mean?
Electrodes
What diameter electrode should you use if
your base metal is ½ in thick?
1/8 inch?
¼ inch?
Electrodes
When selecting an electrode you need to
consider the following:
– How thick is your base metal?
– What condition is your metal in?
– What type of machine do you have access to?
– Welding position?
Welding Safety
Electrical shock
– Make sure the machine is grounded.
– Make sure the cables are not cut or frayed.
– Do not stand in wet surfaces.
– Wear leather gloves.
– Wear rubber-soled shoes
Radiant Energy
Radiant Energy can cause burn
– Make sure you helmet is in good repair and
lenses are not cracked.
– Make sure all skin is covered with cotton
material
– Say cover before welding, so that everyone
can protect themselves from radiant energy
Eye Protection
Make sure you are welding with a shade of
12-14 lens
Make sure your helmet has a Z87 clear
lens with a shaded 12-14 lens on top.
Ventilation
Make sure you are
welding in a well
ventilated area
If you become sick do
not continue and drink
milk.
Use fans to blow out
smoke
General Safety
Keep work area clean and free from
hazards.
– Welding leads
– Flammables
– Cover eyes while chipping slag
What to do and what not to do
Review
What are the types of welding current?
What are the types of welding machines?
Describe proper ventilation when welding.