Transcript INTRODUCTION TO ARC WELDING (SMAW)

INTRODUCTION TO ARC
WELDING
(SMAW)
Terms & Definitions
Welding - Joining of two or more
pieces of metal together by the
fusion process
NOTE: In arc welding, heat is produced by
the electric arc created.
SMAW - Shielded Metal Arc Welding
Electrode - Metal rod which conducts
a current from the electrode holder
to the base metal
Base Metal - Metal to be welded
Continued
Bead Weld - Made by one pass of
the electrode
Bevel – Type of edge preparation
containing an angle
Butt Joint - Weld located between
the two edges of metal.
Crater - Depression at the end of a
weld
Safety precautions in SMAW
welding
Never look at the arc with the naked
eye.
Use a welding hood that is in good
condition and has a #12 shade.
Wear suitable clothing to protect all
parts of the body. (PPE) personal
protective equipment
Long sleeved shirt
Leather gloves
Collar buttoned
Continued
Cuffs turned down
High topped shoes or boots
Do not strike an arc or weld until
you are sure those in the vicinity
have protective equipment or
will look in the other direction.
(Note) Yell “cover” before striking an arc.
Continued
Do not weld around combustible
or flammable materials.
Do not pick up hot metal with
the hands.
(NOTE) Use a pair of pliers
Do not weld in confined places
without ventilation
Continued
Always turn off main switch or
disconnect plug when checking over
a welder.
Do not leave electrode holder on the
welding table or in contact with
grounded metal.
Do not use worn or frayed cables.
Continued
Stand on dry footing when welding.
Keep area around welder clean.
Keep tools and metals in proper
location.
Types of Arc Welders
A.C. – (Alternating current) Welder
current alternates direction 120
times per second.
D.C. – (Direct current) Welder
current flows in the same direction.
TIG – (Tungsten Inert Gas) Welder
may use either A.C. or D.C. with a
non-consumable tungsten electrode
and an inert shielding gas.
Continued
MIG – (Metal Inert Gas) May use
A.C. or D.C. with a base wire filler
material that is fed automatically into
weld; also has an inert shielding gas.
Common SMAW Tools
Welder
Electrode Holder
Ground clamp
Shield or helmet
Gloves
Chipping hammer
Safety goggles or glasses
Wire brush
Electrodes
Types of Electrodes
Mild Steel
High Carbon Steel
Hard Surfacing
Alloys – special purpose
Electrode Characteristics
AWS
Class
Covering
Current
Requirements
Position
Characteristics
EXX 10
Cellulose
Sodium
DCEP
All
Deep Penetration,
With Ripples
EXX 11
Cellulose
Potassium
AC, DCEP
All
Flat Decking
Deep Penetration,
With Ripples
EXX22
Rutile
Sodium
DCEN, AC
Flat, Horiz. Fillet
Deep Penetration,
With Ripples
EXX 24
Rutile
50% Iron
Powder
Mineral
50% Iron
Powder
EXX 27
AC, DCEP, DCEN Flat, Horiz. Fillet
High Deposition
Shallow Penetration
AC,DCEP, DCEN Flat, Horiz. Fillet
High Deposition
Shallow Penetration
Electrode Characteristics continued
AWS
Class
Covering
Current
Requirements
Position
Characteristics
EXX 12
Rutile
Sodium
DCEN, AC
All
Mild to Medium Penetration
EXX 13
Rutile
Sodium
AC, DCEP, DCEN
All
Mild Penetration
EXX 14
Rutile
30% Iron
Powder
Low-Hydrogen
30% Iron
Powder
Low-Hydrogen
50% Iron
Powder
AC, DCEN
All
Medium Penetration
DCEP, AC
All
Medium Penetration
AC, DCEP
Flat, Horiz. Fillet
High Deposition
EXX 18
EXX 28
Common Sizes of Electrodes
1/8”
5/32”
Sizes of electrodes range from 1/16”
to 3/8”.
Electrode size is determined by the
diameter of the wire core.
AWS Classification
E70XX-H4R
•Electrode
Tensile in Ksi
Welding Position:
1 = All Position, 2 = Flat & Horizontal
Type of Current and Coating
*Hydrogen:
H4 = Less than 4ml/100g weld metal, H8 = Less than 8ml/100g Weld Metal
or H16 = Less than 16ml/100g weld metal
*Meets Requirements of Absorbed Moisture Test
*Optional Designators
Electrode Coating Functions
To Provide Deoxidizers & Scavengers
To Produce Shielding Gases
To Produce a Slag Covering
To Provide Mechanical and Physical
Properties
To Increase Deposit Rates
Effects of Raising & Lowering
Current
Raising current
Produces more heat
Lowering current
Produces less heat
(Note: On thicker metals more heat is
necessary in order to get penetration
of the weld.)
Methods of Establishing an Arc
Scratching
Similar to striking a match
Tapping
Straight down and up
Characteristics of Proper Arc
Length
End of electrode is the same distance
from the base metal as the diameter
of electrode.
1/8” electrode = arc length 1/8”
Correct arc length makes a steady
hum of the welder.
Correct arc length makes a “frying”
sound at the arc
Like bacon frying in a pan
Parts of the welding process
Electrode
Wire core
Coating (flux)
Arc
Gaseous shield
Weld
Slag
Parts Continued
Heat lines
Base metal
Penetration
Crater
15 – 30 degree angle
Direction of travel
Principles of the SMAW
Process
Kinds of Welds
Fillet
Groove
Bead
Fillet Weld
Groove Welds
Continued
Types of Weld Joints
Butt Joint
Lap Joint
Tee Joint
Corner Joint
Edge Joint
Square Butt Joint
Tee Joints
A- plain tee
B- single beveled
C- double beveled
D- single J
E- double J
Lap Joints
A- single lap joint,
one weld.
B- single lap joint,
two welds.
C- offset lap joint.
Corner Joints
Edge Joints
Welding Positions
Flat
1F & 1G
Horizontal
2F & 2G
Vertical
3F & 3G
Overhead
4F & 4G
Weld Positions
Reason for Poor Welds
Machine adjustment too hot or too
cold
Electrode size too large or too small
Improper movement of electrode
Improper angle of holding electrode
Improper base metal preparation
Arc length too long or too short