1. Welding Course 1 Arc Welding Processes By: M. Seidi Oct. 2007
“In The Name of God”
Welding Course 1
Arc Welding Processes
The first series of welding processes that we will investigate are the arc welding processes.
By: M. Seidi
Oct. 2007

2. Joining Processes Introduction Chemical Mechanical Metallurgical
Welding
Mineral & Organic
Glue
Screw & Rivet
Nail & Peen
Brazing

3. Other Fastening Methods
Introduction: 1. Mechanical Joining Processes
Mechanical Fastening
Threaded Fasters
Bolts
Screws
Nuts
Other Fastening Methods
Stapling
Crimping
Snap-in Fasteners
Shrink and press fits

4. c) Split (bifurcated) d) compression
Introduction: 1. Mechanical Joining Processes
Rivets
a) Solid b) Tubular
c) Split (bifurcated) d) compression

5. Design guidelines for riveting
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

6. Design guidelines for riveting
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

7. Products are joined and assembled by the use of Adhesives
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

8. Introduction: 2. Chemical Joining Processes
Types of adhesives
Property

9. Adhesive Peeling Test Introduction: 2. Chemical Joining Processes
Peeling Force
(a)
(b)
Characteristic behavior of adhesive in a peeling test :
(a) brittle adhesive (b) tough adhesive

10. Joint Design in Adhesive Bonding
Introduction: 2. Chemical Joining Processes
Joint Design in Adhesive Bonding
a. Poor
Adhesive
b. Good
c. Very Good
d. Combination Joints
Adhesive
Adhesive
Spot Weld
Rivet

11. Configurations for adhesive bonds
Introduction: 2. Chemical Joining Processes
Configurations for adhesive bonds
(a) Single lap (b) Double lap

12. Configurations for adhesive bonds
Introduction: 2. Chemical Joining Processes
Configurations for adhesive bonds
(c) Scarf (d) Strap

13. Non consumable electrode
Introduction: 3. Metallurgical Joining Processes
Joining
Solid state welding
Fusion welding
Soldering and brazing
Resistance welding
Cold welding
Friction welding
Diffusion welding
Flash welding
Ultrasonic welding
Explosion welding
Soldering
Brazing
Arc energy
Chemical energy
Oxyacetylene welding
Oxyfuel gas welding
Consumable electrode
Non consumable electrode
Other processes
Gas metal arc welding
Shielded metal arc welding
Submerged arc welding
Flux cored arc welding
Electrogas welding
Electroslag welding
Gas tungsten arc welding
Atomic hydrogen welding
Plasma arc welding
Laser beam welding
Thermit welding
Electron beam welding …

14. 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

15. 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

16. Additional Electric Arc Welding Processes
FCAW (Flux Core Arc Welding)
ESW (Electroslag Welding)
EGW (Electrogas Welding)
PAW (Plasma Arc Welding)
ASW (Arc Stud Welding)

17. Safe Practices Protection from : Arc’s rays Welding fumes Sparks
Contact with hot metal

18. Arc Welding Power Supplies
The current for arc welder can be supplied by line current or an alternator/generator.
Line current must be transformed:
High voltage--Low amperage High amperage--low voltage
The type of and polarity of the welding current is one of the differences between the different arc welding processes.
SMAW Constant current (CC), AC, DC+ or DC-
GMAW Constant voltage (CV) DC+ or DC-
GTAW Constant Current (CC) ), AC, DC+ or DC-
Welding current differences can include:
Amperage
Voltage
Polarity
High frequency current
Wave form

19. Considerations When Selecting an Arc Welding Power Supply
Maximum Amperage
Duty cycle
Amperage range
Amperage adjustment mechanism
Input power requirements
Initial cost and operating cost
Size and portability
Future needs for a power supply
Available skills
Safety
Manufacturer's support
Open circuit voltage

20. Arc Welding Requirements
Process
Heat
Shielding
Filler Material
MMAW
Electric Arc
Flux
Stick Electrode
GMAW
Inert Gas
(Cylinder)
Spool Wire
GTAW
Straight Rod
SAW
Coil Wire

21. 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.

22. Five Common Output Currents
1. AC
2. DC
3. ACHF
4. PC
5. Square wave
(Alternating Current)
(Direct Current)
(Alternating Current-High Frequency)
(Pulsed Current)

23. Addition Features Available on Some Electric Arc Power Supplies:
1. Remote control
2. High frequency
3. Wave balancing
4. Voltage control

24. Electric Arc Welding Electrical Terms
Electrical Circuit
Direct current (DC)
Alternating current (AC)
Ampere
Volt
Resistance
Ohms Law
Constant potential
Constant current
Voltage drop
Open circuit voltage
Arc voltage
Polarity
Dual Control

25. An electrical circuit is a complete path for electricity.
When the arc is established, an electrical circuit is also completed.

26. 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.

27. 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.

28. Ampere
Amperes: the unit of measure for current flow.
One ampere is equal to ×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.

29. 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.

30. Measured in units of Ohm’s (  )
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.

31. Commonly expressed as: E=I.R
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: E=I.R
Can also be used to teach electrical safety.
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.

32. Constant current Constant potential
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.

33. 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.

34. 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%).

35. Constant Potential Power Supply
The constant potential power supply is modified to produce a relatively constant voltage as the amperage changes.
Characteristic of GMAW power supplies.

36. Primary cause is resistance.
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.

37. 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.

38. Joints, Welds & Positions
Electric arc welding uses five types of joints, five types of welds and five positions.
Five Joints:
Butt
Corner
Lap
Edge T

39. Surface Welds Groove Welds Fillet Welds Plug Welds Slot Welds
Five types of welds
Surface Welds
Groove Welds
Fillet Welds
Plug Welds
Slot Welds

40. 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.

41. The primary use of groove welds is to complete butt joints.
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.

42. 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

43. 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.

44. They are complete the same as plug welds.
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.

45. Joints, Welds & Positions
Flat
Horizontal
Vertical Up
Vertical Down
Overhead

46. Weld Nomenclature Bead Penetration Base metal Reinforcement
Joint Angle
Bead
Root Face
Excessive
Penetration
Root Opening

47. Weld Nomenclature-cont.
Reinforcement
Toe
Face
Leg
Throat
Toe
Root
Leg

48. Weld Nomenclature-cont.
In multiple pass welds, each pass has a specific function.
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.
Cover Pass
Filler Pass
The root pass is used to fuse the root of the weld.
If the root pass does not have adequate penetration, it must be cut or gouged out before the weld is completed.
Root Pass
Tack Weld
The filler pass is used to fill in the joint.
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.

49. Pattern beads are used whenever a wider bead is needed.
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

50. 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.
Contamination of the weld pool, by the atmosphere, can cause weld defects. These defects can have an adverse effect on the joint efficiency, which may lead to failure. Therefore, the weld pool should be protected from the atmosphere until it has completely solidified.
A variety of fluxes and shielding gases are employed by the arc welding process to provide atmospheric shielding.

51. Fluxes melt to form a protective slag over the weld pool
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
Welding fluxes have three forms. Flux can be poured over the weld pool in a granular form as in submerged arc welding, it can be coated on the exterior of the electrode as in shielded arc welding, or it can be placed in the interior core of the electrode as in flux-cored arc welding.
During the process, the flux melts or vaporizes. The vaporized flux forms a protective atmosphere around the molten pool. The melted flux flows over the surface of the weld pool, further protecting it from atmosphere contamination. This molten flux is referred to as slag, and solidifies upon cooling as a hard covering over the weld pool.
Slag must be removed after each pass of a multi-pass weld. Any trapped slag is one of many welding defects, and can degrade joint properties. Flux compositions can be designed so that the slag peels away from the weld during cooling. This occurs because of the thermal contraction mismatch between the weld metal and slag.

52. 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.
Shielding gas can be a single pure gas or a mixture of two or more gases.
Inert gases, as the name implies, do not react with the weld metal. Argon is often used in the flat and horizontal position, since it is heavier than air. Helium can be used in the overhead position, since it is lighter than air. Helium has a characteristic of producing a “hotter” arc than argon.
Active gases, such as oxygen and carbon dioxide, are often added to inert gases in order to improve arc properties. These properties include arc stability and spatter reduction.
Shielding gases should be free of moisture, which decompose to hydrogen and oxygen in the arc. Moisture in the gas can result in porosity, and in steels, hydrogen can lead to cracking..
The gas is regulated and measured as a flow rate in cubic feet per hour or liters per minute as it passes over the weld pool.
Argon
Helium
Oxygen
Carbon Dioxide

53. Questions?
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?

54. Shielded Metal Arc Welding (SMAW)
The arc is struck between the tip of the electrode and the workpiece. The arc is moved over the work at the appropriate arc length and travel speed, melting and fusing a portion of the base metal and continuously adding filler metal. Electrode types and sizes, (with predetermined coating compositions) are selected to correspond to the required strength levels of base metal, the types of welding power supplies utilized and depth of penetration and amount of weld metal fill required.

55. Shielded Metal Arc Welding Equipments

56. Conductor Magnetic flux lines
Magnetic Flux Motion
Conductor
Magnetic flux lines

57. AWS SMAW Electrode Identification System
Electrode Strength Position
E X X X X
Coating/Operating Characteristics

58. AWS SMAW Electrode Identification System
E XX YY نشاندهنده الكترود
E XX YY نشاندهنده مينيمم استحكام كششي فلزجوش
E XX YY نشاندهنده وضعيت جوشكاري
Y=1 قابل كاربرد در تمام وضعيت هاي جوشكاري
Y=2 قابل كاربرد در وضعيت هاي تخت و افقي
Y=4 قابل كاربرد در تمام وضعيت هاي جوشكاري و عمودي رو به پائين
E XX YY نشاندهنده نوع پوشش الكترود جوشكاري
Y=0, 1 پوشش سلولزي
Y=2, 3, 4 پوشش روتيلي محتوي اكسيد تيتانيوم
Y=5, 6, 8 پوشش قليايي كم هيدروژن
Y=7 پوشش اكسيدي
Y=9 پوشش خاص

59. Steel Alloy Suffixes for SMAW Electrodes
Suffix Major Alloy Element(s)
A1 0.5% Molybdenium
B1 0.5% Molybdenium + 0.5% Chromium
B2 0.5% Molybdenium % Chromium
B3 1.0% Molybdenium % Chromium
B4 0.5% Molybdenium + 2.0% Chromium
C1 2.5% Nickel
C2 3.5% Nickel
C3 1.0% Nickel
D1 0.3% Molybdenium + 1.5% Manganese
D2 0.3% Molybdenium % Manganese
G 0.2% Molybdenium + 0.3% Chromium + 0.5% Nickel % Manganese + 0.1% Vanadium
W Weathering Steel

60. AWS SMAW Electrode Classification Example
E indicates electrode
70 indicates 70,000 psi tensile strength
1 indicates use for welding in all positions
8 indicates low hydrogen
This slide illustrates the American Welding Society Electrode Classification System found in Code A The E7018 electrode is probably one of the most commonly used. The E indicates that this is an electrocde, the 70 indicates that the weld metal deposited has at least 70,000 pounds per square inch tnesile strength, the 1 indicates that the electorde can be used in all positions, and the 8 indicates that it is a low hydrogen electrode.
Additional information May be given by a series of suffixes separated by dashes. In the second example, the “A1” indicates Chemical composition for undiluted weld metal. “H8” indicates conformity to the diffusable hydrogen test. (8 ml of H2 per 100g of deposited metal). Finally, the “R” indicates conformity to an absorbed moisture test (less than 0.4% Moisture Content).
E7018-A1-H8 = ?

61. AWS Carbon and Low Alloy Steel Electrodes

62. AWS: American Welding Society
ANSI/AWS :
Specification for Covered Carbon Steel
ANSI/AWS :
Specification for Low Alloy Steel
ANSI/AWS :
Specification for Corrosion Resistant Steel
Common electrode specification can become confusing to the user and manufacturer, depending upon the number of special requirements desired for an application. Some common American Welding Society SMAW specifications for electrode classifications are presented here. You are urged to examine these. They can be obtained from AWS at the website listed.
AWS Website:

63. 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

64. British Standard (BS) SMAW Electrode Identification System
i. Mandatory Part :
E AA BB C(C)
E Indicate Covered MMAW Electrode
AA Indicate Yield Strength of Electrode Core (MPa)
BB Indicate Electrode Elongation Percent
C(C) Indicate Type of Covering:
A Acidic O Oxide
AR Routile Acidic R Routile (Medium Cover)
B Basic RR Routile (Thick Cover)
C Cellulosic S Other Type

65. British Standard (BS) SMAW Electrode Identification System
ii. Arbitrary Part :
DDD X Y H
DDD Indicate Nominal Electrode Recovery
X Indicate Electrode Usability:
3. Y Indicate Recommended Polarity and Voltage (Next Slide)
4. H Low Hydrogen Electrodes
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

66. British Standard (BS) SMAW Electrode Identification System
Recommended Ampere and Voltage Table
Code
Polarity
Minimum Voltage 1
DCEN & DCEP 50 2
DCEN 3
DCEP 4 70 5 6 7 90 8 9

67. British Standard (BS) SMAW Electrode Identification System
Example: E B H
E Covered MMAW Electrode
51 Yield Strength (MPa)
33 Elongation Percent
B Basic Cover
160 Electrode Recovery
2 All Positions Expect V-Down
0 DCEN With Minimum 50 Volts
H Low Hydrogen Cover

68. European Norm (EN) SMAW Electrodes
Chemical Composition:

69. 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

70. European Norm (EN) SMAW Electrodes
Mechanical Properties:

71. European Norm (EN) SMAW Electrodes
Symbols for Weld Metal Recovery:

72. 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 :
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.

73. European Norm (EN) SMAW Electrodes
Symbols for Hydrogen Content:

74. European Norm (EN) SMAW Electrode Identification System
Example: E CrMo1 B 4 4 H5
E Covered MMAW Electrode
CrMo1 Chemical Composition (Table 1)
B Type of Covering (Basic Cover)
4 Recovery and Type of Current (Table 3)
4 Welding Position (F Butt & F Fillet Welds)
H5 Hydrogen Content (5 ml/100 gr. Weld Metal)

75. 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 Clay , Talc, Glycerin Aid Extrusion
f. Binding Agents Sodium Silicate , Asbestos , Starch , Sugar
g. Alloying and Deoxidizing Si, Al, Ti, Mn, Ni, Cr Elements

76. Materials Used in Coverings on Steel Electrodes for SMAW
a. Arc Stabilizers:
. Common Name Technical Name Remarks
1. Titania TiO2 Frequently used from purified titanium oxide
2. Potassium oxalate K2C2O4 Infrequently used
3. Lithium carbonate Li2CO3 Infrequently used

77. b. Gas-Forming Materials:
Materials Used in Coverings on Steel Electrodes for SMAW
b. Gas-Forming Materials:
. Common Name Technical Name Remarks
1. Cellulose Purified wood pulp Principle ingredient in C6H10O5 “cellulosic” electrodes
2. Wood flour Raw wood pulp CnHnOn
3. Limestone CaCO3 Produces CO and CO during welding and forms basic slag

78. 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 Strong fluxing agent CaF2

79. d. Slag Forming Materials:
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-KnNanAlSi3O Plagioclases-CaAl2Si2O8
3. Fluospar Fluorite Markedly decreases CaF2 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

80. d. Slag Forming Materials-Cont.:
Materials Used in Coverings on Steel Electrodes for SMAW
d. Slag Forming Materials-Cont.:
. Common Name Technical Name Remarks
6. Silica Flour Cristobolite Strong acid slag former
7. Wollastonite Calcium 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 Infrequently used ZrO2

81. d. Slag Forming Materials-Cont.:
Materials Used in Coverings on Steel Electrodes for SMAW
d. Slag Forming Materials-Cont.:
. Common Name Technical Name Remarks
10. Magnetite Iron oxide Magnetic iron oxide Fe3O4
11. Periclase Magnesium oxide Raises melting temp and increases viscosity of molten slag
12. Pyrolusite Manganese dioxide MnO2

82. e. Slipping Agents to Aid Extrusion:
Materials Used in Coverings on Steel Electrodes for SMAW
e. Slipping Agents to Aid Extrusion:
. Common Name Technical Name Remarks
1. Bentonite clay Montmorillonite Used where water of constitution can be tolerate
2. Kaoline clay Kaolinite Al2Si2O5(OH)
3. Mica Musovite KAl2(Si3Al)O10(OH)2
4. Talc Soapstone Mg3Si4O10(OH)2
5. Glycerine Glycerol Trihydric alchol C3H5(OH)3

83. Materials Used in Coverings on Steel Electrodes for SMAW
f. Binding Agents:
. Common Name Technical Name Remarks
1. Sodium silicate Water glass Agent most often used Na2OnSiO2(OH)n
2. Potassium silicate K2OnSiO2(OH)n
3. Asbestos Crysotile Improves durability baked covering and mixes with slag when melted during welding
4. Dextrine Starch (C6H10O5)
5. Gum arabic Acacia (CnOnHn)
6. Sugar Cn(OH)n

84. g. Alloying and Deoxidizing Elements:
Materials Used in Coverings on Steel Electrodes for SMAW
g. Alloying and Deoxidizing Elements:
. Common Name Technical Name Remarks
1. Ferrosilicon Usually Silicon is deoxidizer % Si + Fe and alloying element
2. Ferroaluminum Usually Strong deoxidier % Al + Fe
3. Ferrotitanium Usually Strong deoxidier and % Ti + Fe grain refining agent
4. Zirconium alloy 40% Zr + Deoxidier % Si + Fe
5. Electro Mn = 100% Most common alloying manganese element
6. Chromium metal Cr = 100%
7. Ferromanganese Std. type (80%Mn + Fe)

85. Typical Covering Formulas for Steel SMAW Electrodes
Part I: Material Formulas (Parts by Weight Percent)
E 6010
E 6012
E 6020
E 7015
E 7018
Cellulose 25 5
Limestone 40 30
Fluorspar 15 10
Rutile 55 20
Titania 12
Asbestos 8
Iron oxide 1
Clay 2
Iron Powder 35
Ferrosillicon
Ferromanganese 4 6
Sodium silicate 60 70
Potassium silicate

86. Typical Covering Formulas for Steel SMAW Electrodes
Part II: Chemical Composition (Percent After Baking)
E 6010
E 6012
E 6020
E 7015
E 7018
CaO
25.5
14.4
TiO2
10.1
46.0
15.4
CaF2
15.2
11.0
SiO2
47.0
23.6
40.0
20.0
20.5
Al2O3
5.0
2.3
2.8
2.0
MgO
3.2
1.2
Na3AlF3
5.7
FeO
1.3
7.0
30.7
Na2O
5.1
2.4
3.3
1.7
K2O Si
1.5
1.0
2.5 Mn
4.0
1.8 Fe
28.5
CO & CO2
20.2
12.0
Volatile Matter
25.0
Moisture
0.5
0.1

87. Not as sensitive to part fit-up variances
SMAW Advantages
Easily implemented
Inexpensive
Flexible
Not as sensitive to part fit-up variances
An additional advantage is the familiarity most welders have with the process. This process is usually the first one taught to welders. From a cost standpoint, initial investment in the process is low in comparison to other welding processes such as gas metal arc welding. SMAW’s flexibility is unprecedented in narrow access applications and, as the above photograph shows, even in underwater welding.

88. Equipment relatively easy to use, inexpensive, portable
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
Shielded Metal Arc Welding (SMAW) is by far the most widely used arc welding process. It is very popular because of it’s many advantages. The equipment is relatively easy to use, inexpensive, and portable. The filler metal and means for protecting the weld puddle are provided by the covered electrode. It is a versatile process in that it can be used on carbon steels, low alloy steels, stainless steels, cast irons, copper, nickel, and aluminum.

89. Other possible effects on quality are porosity, and hydrogen cracking
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
Aspects of the SMAW process present disadvantages from a quality standpoint; these include a dependence on operator technique, as well as the starting and stopping of the arc to change electrodes. Slag entrapment and lack of fusion to the basemetal or previous passes can occur during welding as a result of improper torch manipulation by the welder. Improper cleaning can also cause slag inclusion defects.
In addition, at each start and stop there is a possibility of porosity being formed since it takes some time for the slag to melt and form a protective gas over the molten weld pool.

90. Low Deposition Rates Low Productivity Operator Dependent Limitations
SMAW has a low weld metal deposition rate compared to other processes. This is because each welding rod contains a finite amount of metal. As each electrode is used, welding must be stopped and a new rod inserted into the holder. A 12-inch electrode may be able to deposit a bead 6-8 inches long.
The overall productivity of the process is impeded by:
Frequent changing of electrodes,
Interpass cleaning (grinding, brushing, etc.),
Grinding of arc initiation points and stopping points,
Slag inclusions which require removal of the defect and rewelding of the defective area.

91. Heat of welding too high for lead, tin, zinc, and their alloys
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
There are other limitations of the SMAW process as well. The heat of the welding arc is too high for some lower melting metals. And the shielding of metals that react aggressively with the atmosphere is inadequate.

92. Questions?
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?

93. Electrode Required Test According to AWS

94. 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.

95. Electrode Required Test: Chemical Analysis
Weld Block for Chemical Analysis

96. Electrode Required Test: Chemical Analysis
Chemical Composition Requirements for Weld Metal

97. Electrode Required Test: Tension & Impact
Test Assembly Showing Location of Test Specimen
E7018M
Orientation and Location of Impact Test Specimen
Orientation and Location of All-Weld Metal Tension Test Specimen

98. Electrode Required Test: Tension & Impact
Tension Test Specimen:
Tension Test Specimen for E 6022:

99. Electrode Required Test: Tension & Impact
Tension Test Requirements:

100. Electrode Required Test: Tension & Impact
Impact Test Specimen:
Impact Test Requirements:

101. Electrode Required Test: Fillet Weld Test
Positions of Test Plates for Welding Fillet Weld Test Specimens

102. Electrode Required Test: Fillet Weld Test
Requirements for Preparation of Fillet Weld Test Assemblies
Dimensional Requirements for Fillet Weld Usability Test Specimen

103. Electrode Required Test: Fillet Weld Test
Alternative Methods for Facilitating Fracture of the Fillet Weld

104. Electrode Required Test: Transverse Tension Test

105. Electrode Required Test: Bend Test

106. Electrode Required Test: Radiographic Test
Grade Grade 1
Radiographic Soundness Requirements

107. Percent Moisture=(A-B)/Weight of Sample
Electrode Required Test: Moisture Content Test
Percent Moisture=(A-B)/Weight of Sample
A: Final Weight of Moisture Absorb System
B: Primary Weight of Moisture Absorb System

108. Electrode Required Test: Moisture Content Test
Moisture Content Limits in Electrode Coverings
T=27°C
Relative Humidity=80%
T=9hr

109. SMAW Technical Points