Download 1. Mechanical Joining Processes

“In The Name of God”
Welding Course 1
Arc Welding Processes
By: M. Seidi
Oct. 2007
Introduction
Joining Processes
Metallurgical
Welding
Brazing
Chemical
Mineral & Organic
Glue
Mechanical
Screw & Rivet
Nail & Peen
Introduction: 1. Mechanical Joining Processes
Mechanical Fastening

Threaded Fasters




Bolts
Screws
Nuts
Other Fastening Methods




Stapling
Crimping
Snap-in Fasteners
Shrink and press fits
Introduction: 1. Mechanical Joining Processes
Rivets
a) Solid
b) Tubular
c) Split (bifurcated)
d) compression
Introduction: 1. Mechanical Joining Processes
Design guidelines for riveting
(a) Exposed shank is too long; the result is buckling instead of
upsetting
(b) Rivets should be placed sufficiently far from edges to avoid
stress concentrations
Introduction: 1. Mechanical Joining Processes
Design guidelines for riveting
(c)Joined sections should allow ample clearance for
riveting tools
(d) section curvature should not interfere with the
riveting process
Introduction: 2. Chemical Joining Processes
Adhesive Bonding

Products are joined and assembled by the use
of Adhesives

Adhesives properties to be considered

Strength

Toughness

Resistance to various fluids

Ability to wet the surface to be bonded
Introduction: 2. Chemical Joining Processes
Types of adhesives
Property
Introduction: 2. Chemical Joining Processes
Adhesive Peeling Test
Peeling Force
(a)
(b)
Characteristic behavior of adhesive in a peeling test :
(a) brittle adhesive
(b) tough adhesive
Introduction: 2. Chemical Joining Processes
Joint Design in Adhesive Bonding
a. Poor
Adhesive
b. Good
c. Very Good
d. Combination Joints
Adhesive
Rivet
Adhesive
Spot Weld
Introduction: 2. Chemical Joining Processes
Configurations for adhesive bonds
(a) Single lap
(b) Double lap
Introduction: 2. Chemical Joining Processes
Configurations for adhesive bonds
(c) Scarf
(d) Strap
Introduction: 3. Metallurgical Joining Processes
Joining
Solid state welding
Resistance welding
Cold welding
Friction welding
Diffusion welding
Flash welding
Ultrasonic welding
Explosion welding
Consumable electrode
Gas metal arc welding
Shielded metal arc welding
Submerged arc welding
Flux cored arc welding
Electrogas welding
Electroslag welding
Fusion welding
Soldering and brazing
Soldering
Brazing
Arc energy
Chemical energy
Oxyacetylene welding
Oxyfuel gas welding
Non consumable electrode
Gas tungsten arc welding
Atomic hydrogen welding
Plasma arc welding
Other processes
Laser beam welding
Thermit welding
Electron beam welding
…
Introduction: Arc Welding Processes


Electric arc welding refers to a group of fusion
welding processes that use an electric arc to produce
the heat required for melting the metal.
Advantages:








Inexpensive power source
Relatively inexpensive equipment
Welders use standard domestic current.
Portable equipment is available
Process is fast and reliable
Short learning curve
Equipment can be used for multiple functions
Electric arc heat is about 5,000 oC
Introduction: Arc Welding Processes

All fusion welding process have thee requirements:





Heat
Shielding
Filler metal
The method used to meet these three requirements is
the difference between arc welding processes.
In this class you will have the opportunity to use four
arc welding processes:




SMAW
GMAW
GTAW
SAW
Additional Electric Arc Welding Processes
1. FCAW (Flux Core Arc Welding)
2. ESW (Electroslag Welding)
3. EGW (Electrogas Welding)
4. PAW (Plasma Arc Welding)
5. ASW (Arc Stud Welding)
Safe Practices
Protection from :

Arc’s rays

Welding fumes

Sparks

Contact with hot metal
Arc Welding Power Supplies

The current for arc welder can be supplied by line current
or an alternator/generator.


The type of and polarity of the welding current is one of the
differences between the different arc welding processes.




Line current must be transformed:
High voltage--Low amperage High amperage--low voltage
SMAW
GMAW
GTAW
Constant current (CC), AC, DC+ or DCConstant voltage (CV) DC+ or DCConstant Current (CC) ), AC, DC+ or DC-
Welding current differences can include:





Amperage
Voltage
Polarity
High frequency current
Wave form
Considerations When Selecting an Arc Welding Power Supply
1. Maximum Amperage
7. Size and portability
2. Duty cycle
8. Future needs for a
3. Amperage range
4. Amperage adjustment
mechanism
power supply
9. Available skills
10. Safety
5. Input power requirements
11. Manufacturer's support
6. Initial cost and operating cost
12. Open circuit voltage
Arc Welding Requirements
Process
Heat
Shielding
Filler Material
MMAW
Electric Arc
Flux
Stick Electrode
Electric Arc
Inert Gas
(Cylinder)
Spool Wire
GTAW
Electric Arc
Inert Gas
(Cylinder)
Straight Rod
SAW
Electric Arc
Flux
Coil Wire
GMAW
Amperage Output & Duty cycle


Optimum output amperage is
determined by:
 thickness of the metal,
 type of joint,
 welding position
 type of electrode.
The amount of continuous
welding time a power supply
can be used is determined by
the duty cycle of the power
supply.
– Duty cycle is based on a 10
minute interval.
– Many power supplies have a
sloping duty cycle.
Five Common Output Currents
1. AC
(Alternating Current)
2. DC
(Direct Current)
3. ACHF
(Alternating Current-High Frequency)
4. PC
(Pulsed Current)
5. Square wave
Addition Features Available on Some
Electric Arc Power Supplies:
1.
Remote control
2.
High frequency
3.
Wave balancing
4.
Voltage control
Electric Arc Welding Electrical Terms

Electrical Circuit

Constant potential

Direct current (DC)

Constant current

Alternating current (AC)

Voltage drop

Ampere

Open circuit voltage

Volt

Arc voltage

Resistance

Polarity

Ohms Law

Dual Control
Electrical Circuit

An electrical circuit is a
complete path for electricity.

When the arc is established,
an electrical circuit is also
completed.
Alternating Current

The type of current where the flow of electrons reverses direction (polarity) at
regular intervals.

Recommended current for general purpose electrodes and flat position.
Direct Current
• The type of current where
the flow of electrons
(polarity) is in one
direction.
• Controlling the polarity
allows the welder to
influence the location of
the heat.
• When the electrode is
positive (+) DCRP or
DCEP it will be slightly
hotter than the base metal.
• When the base metal is positive
(+), DCSP or DCEN, the base
metal will be slightly hotter than
the electrode.
• DC current is required for some
electrodes and recommended for
out of position welding.
Ampere
• Amperes: the unit of measure
for current flow.
• One ampere is equal to
6.24150948×1018
electrons
passing by a point per second.
• Electricity passing through a
resistance causes heat.
• An air gap is a high resistance
• The greater the amperage flowing through the
resistance (air gap)--the greater the heat.
• The electrode also has resistance.
• Excessive amperage for the diameter of the
electrode over heats the electrode.
• Insufficient amperage for the diameter of electrode
makes electrode hard to start.
Volt

The volt is the measure of electromotive force.

It is defined as the potential difference across a
conductor when a current of one ampere dissipates
one watt of power.

The
voltage
at
the
electrode
determines the harshness of the arc.

Voltage is only adjustable in dual
control machines.
Resistance





That characteristic of a material that
impedes the flow of an electrical current.
Measured in units of Ohm’s (  )
When ever an electrical current passes
through a resistance heat is produced.
Air is a high resistance
Electrical current passing through air
produces a lot of heat.
Ohm’s Law

Ohm's law states that, in an electrical circuit, the
current passing through a material is directly
proportional to the potential difference applied
across them.

Commonly expressed as:

Can also be used to teach electrical safety.



E=I.R
Amperage is the harmful portion of electrical current.
Rearranging Ohm’s Law for amperage shows that
amperage (current flow) is determined by the voltage
divided by the resistance:
I=E/R
The higher the resistance, the less current that will flow
for a given voltage.
Power Supply
There are 2 different types of power supplies:
Constant current
 Constant potential

•
In a constant current power supply, the
current (amperage) stays relatively constant
when the voltage is changed.
•
In a constant potential power supply, the
voltage stays relatively constant when the
amperage is changed.
Constant Current Power Supply
Characteristics of constant current power supply:
• The machine provides a high voltage for
striking the arc.
• Open circuit voltage (OCV)
• OCV is not adjustable for most machines
• When the arc is struck the voltage drops to the
welding voltage.
• Arc voltage
• Arc voltage varies with the arc length.
• As the welding proceeds the current will not
vary much as the arc length changes.
Constant Current Power Supply-Cont.
Increasing the
voltage from
20 to 25 volts
(25%) only
decreases the
amperage from
113 to 120 Amp
(5.8%).
Constant Potential Power Supply

The constant potential power supply is modified to
produce a relatively constant voltage as the amperage
changes.
80
70
60
Volts
50
40
30
20
10
0
0
50
100
150
200
Anperes

Characteristic of GMAW power supplies.
250
Voltage Drop

Voltage drop is the reduction in voltage in an
electrical circuit between the source and the load.

Primary cause is resistance.

When an excessive voltage drop exists, the
electrical circuit will not perform as designed.


Localized resistance (connection) can cause excessive
heat.

Excessive heat can cause component failure.
When extra long welding loads are used, the
amperage must be increased to have the same
heat at the weld.
Dual Control


Some weldors have controls for both the voltage and the
amperage.
Operator can set the harshness of the arc (voltage) and the
amount of heat (amperage) independent of each other.
Joints, Welds & Positions
Electric arc welding uses five
types of joints, five types of
welds and five positions.
Butt
Five Joints:
Corner
Lap
Edge
T
Five types of welds
1. Surface Welds
2. Groove Welds
3. Fillet Welds
4. Plug Welds
5. Slot Welds
1. Surface Welds
• Surface welds are welds were a material has been
applied to the surface of another material.
 May or may not be blended with the work piece.
• Two
common
applications are
for hard surfacing
and padding.
2. Groove Welds
Groove welds are used to fuse the sides or
ends of two pieces of metal.
The primary use of groove welds is to
complete butt joints.
3. Fillet Welds
Fillet welds have a triangular cross section and
are used to fuse two faces of metal that are at a
90 degree angle to each other.
T Joint
Outside Corner
Lap Joint
4. Plug Welds
Plug welds are used to
attach
two
surfaces
together when a complete
joint is not required and
the design does not allow
for any weld bead outside
the dimensions of the
metal.
The holes can be made with a drill bit or punch.
The weld is completed by establishing the arc on the
bottom plate and then continuing to weld until the hole
is full.
5. Slot Welds
Slot welds are identical to plug welds except for
the shape of the holes. For slot welds, slots are
machined or stamped in the upper plate.
They are complete the same as plug welds.
Joints, Welds & Positions
Flat
Horizontal
Vertical Up
Vertical Down
Overhead
Weld Nomenclature
Bead
Penetration
Base metal
Joint Angle
Reinforcement
Bead
Root Face
Root Opening
Excessive
Penetration
Weld Nomenclature-cont.
Reinforcement
Toe
Face
Throat
Toe
Leg
Root
Leg
Weld Nomenclature-cont.

In multiple pass welds, each pass has a specific function.

Cover Pass
A tack weld is used to hold
the joint at the desired gap.

If it is not used, the heat of the
weld will cause the joint to close.
Filler Pass

Root Pass
The root pass is used to fuse
the root of the weld.

Tack Weld

The filler pass is used to fill in the joint.


If the root pass does not have
adequate penetration, it must be
cut or gouged out before the weld
is completed.
A pattern bead or multiple stringer beads will be used.
The cover pass doesn’t add very much strength to the weld. It is
used for appearance and to fill in surface voids.
Bead Patterns


Pattern beads are used whenever a wider bead is
needed.

Hard Surfacing

Filler pass

Cover pass

Reduce penetration
Common patterns:

Circle

Crescent

Figure 8
Protection of the Molten Weld Pool


Molten metal reacts with the atmosphere:

Oxides and nitrides are formed

Discontinuities such as porosity

Poor weld metal properties
All arc welding processes employ some
means of shielding the molten weld pool
from the air.
Welding Flux

Three forms





Granular
Electrode wire coating
Electrode core
Fluxes melt to form a protective slag over the
weld pool
Other purposes




Contain scavenger elements to purify weld metal
Contain metal powder added to increase
deposition rate
Add alloy elements to weld metal
Decompose to form a shielding gas
Shielding Gas



Shielding gas forms a protective
atmosphere over the molten weld pool to
prevent contamination.
Inert shielding gases, argon or helium,
keep out oxygen, nitrogen, and other gases
Active gases, such as oxygen and carbon
dioxide, are sometimes added to improve
variables such as arc stability and spatter
reduction.
Argon
Helium
Oxygen
Carbon Dioxide
Turn to the person sitting next to you and
discuss (1 min.):
• What would happen if there was no flux on
the wire to decompose into gas or no inert
shielding gas was provided?
• What would the weld metal look like?
Shielded Metal Arc Welding (SMAW)
Shielded Metal Arc Welding Equipments
Magnetic Flux Motion
Conductor
Magnetic
flux lines
AWS SMAW Electrode Identification System
Electrode
Strength
Position
E XXXX
Coating/Operating Characteristics
‫‪AWS SMAW Electrode Identification System‬‬
‫‪E XX YY‬‬
‫‪E XX YY‬‬
‫‪E XX YY‬‬
‫‪Y=1‬‬
‫‪Y=2‬‬
‫‪Y=4‬‬
‫‪E XX YY‬‬
‫‪Y=0, 1‬‬
‫‪Y=2, 3, 4‬‬
‫‪Y=5, 6, 8‬‬
‫‪Y=7‬‬
‫‪Y=9‬‬
‫نشاندهنده الكترود‬
‫نشاندهنده مينيمم استحكام كشش ي فلزجوش‬
‫نشاندهنده وضعيت جوشكاري‬
‫قابل كاربرد درتمام وضعيت هاي جوشكاري‬
‫قابل كاربرد دروضعيت هاي تخت و افقي‬
‫قابل كاربرد درتمام وضعيت هاي جوشكاري و عمودي رو به پائين‬
‫نشاندهنده نوع پوشش الكترود جوشكاري‬
‫پوشش سلولزي‬
‫پوشش روتيلي محتوي اكسيد تيتانيوم‬
‫پوشش قليايي كم هيدروژن‬
‫پوشش اكسيدي‬
‫پوشش خاص‬
Steel Alloy Suffixes for SMAW Electrodes
Suffix
Major Alloy Element(s)
1) A1
2) B1
3) B2
4) B3
5) B4
6) C1
7) C2
8) C3
9) D1
10) D2
11) G
0.5% Molybdenium
0.5% Molybdenium + 0.5% Chromium
0.5% Molybdenium + 1.25% Chromium
1.0% Molybdenium + 2.25% Chromium
0.5% Molybdenium + 2.0% Chromium
2.5% Nickel
3.5% Nickel
1.0% Nickel
0.3% Molybdenium + 1.5% Manganese
0.3% Molybdenium + 1.75% Manganese
0.2% Molybdenium + 0.3% Chromium + 0.5%
Nickel + 1.0% Manganese + 0.1% Vanadium
Weathering Steel
12) W
.
AWS SMAW Electrode Classification Example
E7018
• E indicates electrode
• 70 indicates 70,000 psi tensile strength
• 1 indicates use for welding in all positions
• 8 indicates low hydrogen
E7018-A1-H8 = ?
AWS Carbon and Low Alloy Steel Electrodes
AWS: American Welding Society
ANSI/AWS - 5.1 :
Specification for Covered Carbon Steel
ANSI/AWS - 5.5 :
Specification for Low Alloy Steel
ANSI/AWS - 5.4 :
Specification for Corrosion Resistant Steel
AWS Website:
http://www.aws.org
British Standard (BS) SMAW Electrode Identification System
Electrode Classification:
1. Mandatory Part
2. Arbitrary Part
Mandatory
E AA BB C(C) DDD X Y (H)
Arbitrary
British Standard (BS) SMAW Electrode Identification System
i. Mandatory Part :
E AA BB C(C)
1. E
Indicate Covered MMAW Electrode
2. AA
Indicate Yield Strength of Electrode
Core (MPa)
3. BB
Indicate Electrode Elongation Percent
4. C(C) Indicate Type of Covering:
A
AR
B
C
Acidic
Routile Acidic
Basic
Cellulosic
O
R
RR
S
Oxide
Routile (Medium Cover)
Routile (Thick Cover)
Other Type
British Standard (BS) SMAW Electrode Identification System
ii. Arbitrary Part :
DDD X Y H
1. DDD Indicate Nominal Electrode Recovery
2. X
Indicate Electrode Usability:
1. All Positions
2. All Positions Expect V-Down
3. F for Groove and F, H, V for Fillet
Welds
4. F
5. F, V-Down for Groove and H, V
for Fillet Welds
6. Other Position Usability
3. Y
Indicate Recommended Polarity and
Voltage (Next Slide)
4. H
Low Hydrogen Electrodes
British Standard (BS) SMAW Electrode Identification System
Recommended Ampere and Voltage Table
Code
Polarity
Minimum Voltage
1
DCEN & DCEP
50
2
DCEN
50
3
DCEP
50
4
DCEP
70
5
DCEN
70
6
DCEP
70
7
DCEN & DCEP
90
8
DCEN
90
9
DCEP
90
British Standard (BS) SMAW Electrode Identification System
Example:
E
51
33
B
160
2
0
H
E 51 33 B 160 2 1 H
Covered MMAW Electrode
Yield Strength (MPa)
Elongation Percent
Basic Cover
Electrode Recovery
All Positions Expect V-Down
DCEN With Minimum 50 Volts
Low Hydrogen Cover
European Norm (EN) SMAW Electrodes
Chemical Composition:
European Norm (EN) SMAW Electrodes
Symbols for Type of Electrode Covering:
The type of covering of the electrodes
determines to a large extent the usability
characteristics of the electrode and the
properties of the weld metal. Two symbols
are used to denote the type of covering:
- R : rutile covering
- B : basic covering
European Norm (EN) SMAW Electrodes
Mechanical Properties:
European Norm (EN) SMAW Electrodes
Symbols for Weld Metal Recovery:
European Norm (EN) SMAW Electrodes
Symbols for Welding Position:
The symbol below for welding positions
indicates the positions for which the electrode
is tested in accordance with EN 1597-3:
1:
all positions;
2:
all positions, except vertical down;
3:
flat butt weld, flat fillet weld, horizontal
vertical fillet weld;
4:
flat butt weld, flat fillet weld;
5:
vertical down and position according to
symbol 3.
European Norm (EN) SMAW Electrodes
Symbols for Hydrogen Content:
European Norm (EN) SMAW Electrode Identification System
Example:
E CrMo1 B 4 4 H5
E
CrMo1
B
4
4
Covered MMAW Electrode
H5
Hydrogen Content (5 ml/100 gr. Weld
Metal)
Chemical Composition (Table 1)
Type of Covering (Basic Cover)
Recovery and Type of Current (Table 3)
Welding Position (F Butt & F Fillet
Welds)
Coating Materials -Partial List
a. Arc Stabilizers
Titania TiO2
b. Gas-Forming Materials
Wood Pulp,
Limestone, CaCO3
c. Fluxing agents
Cryolite, Witherite,
Flurspar
d. Slag-Forming Materials
Alumina Al2O3 , TiO2 ,
SiO2 , Fe3O4
e. Slipping Agents to
Aid Extrusion
Clay , Talc, Glycerin
f. Binding Agents
Sodium Silicate , Asbestos ,
Starch , Sugar
g. Alloying and Deoxidizing
Elements
Si, Al, Ti, Mn, Ni, Cr
Materials Used in Coverings on Steel Electrodes for SMAW
a. Arc Stabilizers:
. Common Name
1. Titania
Technical Name
TiO2
Remarks
Frequently used from
purified titanium oxide
2. Potassium oxalate
K2C2O4
Infrequently used
3. Lithium carbonate
Li2CO3
Infrequently used
.
Materials Used in Coverings on Steel Electrodes for SMAW
b. Gas-Forming Materials:
. Common Name
1. Cellulose
2. Wood flour
Technical Name
Remarks
.
Purified wood pulp
Principle ingredient in
C6H10O5
“cellulosic” electrodes
Raw wood pulp
CnHnOn
3. Limestone
CaCO3
Produces CO and CO2
during welding and
forms basic slag
Materials Used in Coverings on Steel Electrodes for SMAW
c. Fluxing Agents:
. Common Name
Technical Name
Remarks
1. Cryolite
Na3AlFe6
Strong fluxing agent
2. Barium fluoride
BaF2
3. Lithium fluoride
LiF
Very effective flux
4. Lithium chloride
LiCl
Infrequently used
5. Witherite
BaCO3
Generates CO and
CO2 gases, but then
becomes strong flux
6. Flurspar
Fluorite
CaF2
Strong fluxing agent
.
Materials Used in Coverings on Steel Electrodes for SMAW
d. Slag Forming Materials:
. Common Name
Technical Name
Remarks
1. Bauxite
Alumina
Raises melting
temp. and increases
viscosity of slag
2. Feldspar
Alkali type-KnNanAlSi3O8
Plagioclases-CaAl2Si2O8
3. Fluospar
Fluorite
CaF2
Markedly decreases
viscosity of slag
4. Limenite
FeTiO3
Impure from of
titanium oxide
5. Rutile
TiO2(10%Fe)
Unrefined form of
titanium oxide.
Mainstay of “rutile”
elctrodes
.
Materials Used in Coverings on Steel Electrodes for SMAW
d. Slag Forming Materials-Cont.:
. Common Name
Technical Name
6. Silica Flour
Cristobolite
Remarks
.
Strong acid slag
former
7. WollastoniteCalcium silicate
CaSio3
8. Dolomite
Magnesite
Often used for forming
slag when melting steel
in furnace, but seldom
included in electrodes
coverings
9. Zirconia
Zirconium oxide
ZrO2
Infrequently used
Materials Used in Coverings on Steel Electrodes for SMAW
d. Slag Forming Materials-Cont.:
. Common Name
Technical Name
Remarks
10. Magnetite
Iron oxide
Fe3O4
Magnetic iron oxide
11. Periclase
Magnesium oxide
Raises melting temp.
and increases viscosity
of molten slag
12. Pyrolusite
Manganese dioxide
MnO2
.
Materials Used in Coverings on Steel Electrodes for SMAW
e. Slipping Agents to Aid Extrusion:
. Common Name
Technical Name
1. Bentonite clay
Montmorillonite
2. Kaoline clay
Kaolinite
Al2Si2O5(OH)
3. Mica
Musovite
KAl2(Si3Al)O10(OH)2
4. Talc
Soapstone
Mg3Si4O10(OH)2
5. Glycerine
Glycerol
C3H5(OH)3
Remarks
Used where water of
constitution can be
tolerate
Trihydric alchol
.
Materials Used in Coverings on Steel Electrodes for SMAW
f. Binding Agents:
. Common Name
1. Sodium silicate
Technical Name
Water glass
Na2OnSiO2(OH)n
Remarks
Agent most often used
2. Potassium silicate K2OnSiO2(OH)n
3. Asbestos
Crysotile
4. Dextrine
Starch (C6H10O5)
5. Gum arabic
Acacia (CnOnHn)
6. Sugar
Cn(OH)n
Improves durability
baked covering and
mixes with slag when
melted during welding
.
Materials Used in Coverings on Steel Electrodes for SMAW
g. Alloying and Deoxidizing Elements:
. Common Name
Technical Name
Remarks
1. Ferrosilicon
Usually
50% Si + Fe
Silicon is deoxidizer
and alloying element
2. Ferroaluminum
Usually
85% Al + Fe
Strong deoxidier
3. Ferrotitanium
Usually
40% Ti + Fe
Strong deoxidier and
grain refining agent
4. Zirconium alloy
40% Zr +
40% Si + Fe
Deoxidier
5. Electro
manganese
Mn = 100%
Most common alloying
element
6. Chromium metal
Cr = 100%
7. Ferromanganese
Std. type (80%Mn + Fe)
.
Typical Covering Formulas for Steel SMAW Electrodes
Part I: Material Formulas (Parts by Weight Percent)
E 7015
E 7018
Limestone
40
30
Fluorspar
15
10
10
8
5
2
Cellulose
E 6010
E 6012
25
5
Rutile
E 6020
55
20
10
15
Iron oxide
1
30
Clay
10
5
Titania
12
Asbestos
15
Iron Powder
35
Ferrosillicon
2
2
2
5
5
Ferromanganese
4
4
6
4
4
Sodium silicate
60
40
70
25
Potassium silicate
25
Typical Covering Formulas for Steel SMAW Electrodes
Part II: Chemical Composition (Percent After Baking)
E 6010
E 6012
E 6020
CaO
TiO2
10.1
46.0
47.0
Al2O3
MgO
3.2
E 7018
25.5
14.4
15.2
11.0
15.4
CaF2
SiO2
E 7015
23.6
40.0
20.0
20.5
5.0
2.3
2.8
2.0
2.0
2.8
1.2
2.0
5.7
5.0
Na3AlF3
FeO
1.3
7.0
30.7
Na2O
5.1
2.4
3.3
1.7
K2O
1.2
Si
1.5
1.5
1.0
2.8
2.5
Mn
2.8
2.5
4.0
2.0
1.8
Fe
2.8
28.5
CO & CO2
20.2
12.0
0.1
0.1
Volatile Matter
25.0
5.0
Moisture
4.0
2.0
0.5
SMAW Advantages

Easily implemented

Inexpensive

Flexible

Not as sensitive to
part fit-up variances
Advantages

Equipment relatively easy to use, inexpensive,
portable

Filler metal and means for protecting the weld
puddle are provided by the covered electrode

Less sensitive to drafts, dirty parts, poor fit-up

Can be used on carbon steels, low alloy steels,
stainless steels, cast irons, copper, nickel,
aluminum
Quality Issues

Discontinuities
associated with manual
welding process that
utilize flux for pool
shielding



Slag inclusions
Lack of fusion
Other possible effects on
quality are porosity, and
hydrogen cracking
Limitations

Low Deposition
Rates

Low Productivity

Operator Dependent
Other Limitations

Heat of welding too high for lead, tin,
zinc, and their alloys

Inadequate weld pool shielding for
reactive metals such as titanium,
zirconium, tantalum, columbium
Turn to the person sitting next to you and
discuss (1 min.):
• Wood (cellulose) and limestone are added to
the coating on SMAW Electrodes for gas
shielding. What gases might be formed?
• How do these gases shield?
Electrode Required Test According to AWS
Electrode Required Test: Chemical Analysis
Note 9:
The minimum completed pad size shall be at
least four layers m height (H) with length (L)
and width (W) sufficient to perform analysis,
The sample for analysis shall be taken at least
1/4 in. (6.4 mm) above the original base metal
surface.
Electrode Required Test: Chemical Analysis
Weld Block for Chemical Analysis
Electrode Required Test: Chemical Analysis
Chemical Composition Requirements for Weld Metal
Electrode Required Test: Tension & Impact
Test Assembly Showing Location of Test Specimen
E7018M
Orientation and Location of
Impact Test Specimen
Orientation and Location of AllWeld Metal Tension Test Specimen
Electrode Required Test: Tension & Impact
Tension Test Specimen:
Tension Test Specimen for E 6022:
Electrode Required Test: Tension & Impact
Tension Test Requirements:
Electrode Required Test: Tension & Impact
Impact Test Specimen:
Impact Test Requirements:
Electrode Required Test: Fillet Weld Test
Positions of Test Plates for Welding Fillet Weld Test Specimens
Electrode Required Test: Fillet Weld Test
Requirements for Preparation of Fillet Weld Test Assemblies
Dimensional Requirements for Fillet Weld Usability Test Specimen
Electrode Required Test: Fillet Weld Test
Alternative Methods for Facilitating Fracture of the Fillet Weld
Electrode Required Test: Transverse Tension Test
Electrode Required Test: Bend Test
Electrode Required Test: Radiographic Test
Grade 1
Radiographic
Soundness
Requirements
Grade 2
Electrode Required Test: Moisture Content Test
Percent Moisture=(A-B)/Weight of Sample
A:
B:
Final Weight of Moisture Absorb System
Primary Weight of Moisture Absorb System
Electrode Required Test: Moisture Content Test
Moisture Content Limits in Electrode Coverings
T=27°C
Relative Humidity=80%
T=9hr
SMAW Technical
Points