1. SMAW Welding

2. Definition
Shield Metal Arc Welding is an arc welding process that uses a consumable electrode to initiate the arc and provide the filler material.

3. Arc Welding Safety
What are the principle hazards associated with SMAW?
What can be done to manage the hazards associated with SMAW?
Hot metal.
Harmful rays
Fire
Burns
Explosion
tripping/falling
_______
Use appropriate PPE
Inspect equipment
Pliers
shaded lens
welding apparel

4. What’s the purpose of slag?
SMAW Process
The arc temperature over 9,000 oF melts the base metal, the wire core and the coating on the electrode.
The high temperature causes some of the ingredients in the flux to form a gaseous shield.
The electric energy is provided by a power source.
As the weld cools slag forms on top of the weld puddle.
The slag contains the impurities that were in the weld pool and it retards the cooling rate.
What’s the purpose of slag?

5. Equipment Polarity switch Power cord Electrode holder Electrode
Base metal
Ground clamp
Electrode lead
Ground lead
Amperage scale
Amperage adjustment
On/Off switch
Welder case

6. Six (6) Common SMAW Power Supplies
What welding current is available from each of these power supplies?
Type
Current
Transformer
Transformer with rectifier
Generator
Alternator
Alternator with rectifier
Inverter
Transformer Ac
Transformer-rectifier AC & DC
Generator DC
Alternator AC
Alternator-rectifier AC and DC
Inverter AC and DC

7. Initiating The Arc List the six (6) steps for initiating the arc.
Select the best electrode
Set the welder current
Turn on welder
Warn bystanders
Lower helmet
Start arc (two methods)
Brushing
Tapping

8. Brushing Method
Hold end of electrode about 1/4 - 1/2 inch above the surface.
Lower helmet
Gently brush surface of the metal with the end of the electrode.
When arc starts, lift electrode 1/8 inch.
If electrode sticks, twist it back and forth. If it does not break loose, release electrode from electrode holder.
Do not shut off the welder with the electrode stuck to the metal.
Burn out the switch
Why?

9. Tapping Method Set up welder
Hold the electrode at the travel angle and 1/4 - 1/2 inch above the metal.
Quickly lower the electrode until it touches the metal and then lift it 1/8 inch.
Recommended method for E7018 electrode because the flux must be broken off before the arc will start.

10. Five (5) Factors Controlling the Quality of SMAW Welds
Heat
Electrode
Electrode angle
Arc length
Speed of travel

11. Five (5) Factors 1. Heat
The arc welder must produce sufficient heat (BTU’s) to melt the electrode and the base metal to the desired depth.
How is the amount of heat at the weld controlled?
What factors determine the amount of heat required for a weld?
Adjusting the amperage
Thickness of the metal
Type of joint,
Electrode type
Electrode diameter
Weld position

12. Five (5) Factors 1. Heat – cont.
What are the characteristics of excessive heat when completing a SMAW joint?
What are the characteristics of insufficient heat when completing a SMAW weld?
Electrode easier to start
Excessive penetration (burn through)
Excessive bead width
Excessive splatter
Electrode overheating
Hard to start
Reduced penetration
Narrow bead
Coarse ripples

13. Five (5) Factors 2. Electrodes
What are the two (2) primary requirements for an SMAW electrode?
What metals can be welding with the SMAW process?
How are SMAW electrodes classified?
Must be compatible with base metal
Must be correct size.
Carbon steels
Low alloy steels
Corrosion resisting steels
Cast irons
Aluminum and alloys
Copper and alloys
Nickel and alloys
American Welding Society system and grouping

14. American Welding Society (AWS) Classification System
The AWS system designates:
tensile strength,
weld position
coating (flux)
current.
The primary difference in the performance of electrodes is the flux.
Manufactures may and do use their own numbering system and sell electrodes that do not use the AWS system.

15. Arc Welding Electrode Flux
Flux: A material used during arc welding, brazing or braze welding to clean the surfaces of the joint chemically, to prevent atmospheric oxidation and to reduce impurities and/or float them to the surface. (British Standard 499)
SMAW fluxes are naturally occurring minerals.
The quality, and cost, of the flux is directly related to the amount of resources the manufacture invests purifying the minerals for the flux.

16. Seven (7) Classifications of Flux constituents
calcium, manganese, calcium fluoride and cellulose
Protection from atmospheric contamination & slag formers
Fluxing agents
Arc initiators and stabilizers
Deoxidizes
Physical properties of the flux
Fillers and metallic additions
Binders and flux strength improvers
calcium carbonates, rutile, silica, talc
nickel and iron powders, sodium, feldspar, clay, talc
ferroalloys, ferrosilicon, iron powder
manganese, iron, rutile, alumina, silica, calcium fluoride
waterglass, mica organic binders
ferrow alloys, iron and nickel powders

17. Electrode Performance Groups
Fast-freeze
Mild steel
Quick solidification of weld pool
Deep penetrating
Recommended for out of position welds
Deep penetrating arc
Fast-fill
Highest deposition rate
Stable arc
Thick flux
Flat position and horizontal laps only
Fill-freeze
General purpose electrodes
Characteristics of fast-freeze and fast-fill
Low hydrogen
Welding characteristics of fill-freeze
Designed for medium carbon and alloy steels

18. Selecting Electrode Size
What factors determine the optimum diameter of electrode that should be used?
Is it permissible to use more than one diameter of electrode to complete a joint?
Yes
Explain!
thickness of the base metal,
welding position
capacity of the welding power supply
Small diameter for route pass—larger for filler passes.
ROT: the diameter of the electrode should not exceed the thickness of the metal.

19. Electrode Storage
Electrodes are damaged by rough treatment, temperature extremes and moisture.
The should be kept in their original container until used.
They should be stored in a heated cabinet that maintains them at a constant temperature.
The storage of low hydrogen electrodes is very critical.
Designed to reduce underbead cracking in alloy and medium carbon steels by reducing the the amount of hydrogen in the weld pool.
The flux is hydroscopic--
Moisture in the flux also causes excessive gasses to develop in the weld pool and causes a defect in the weld called worm holes.
What is the primary source of hydrogen in the weld pool?
What does that mean?
Water
attracts moisture (H2O).

20. Five (5) Factors 3. Electrode Angle
Two angles are important:
Travel
Work
The travel angle is the angle of the electrode parallel to the joint.
The correct travel angle must be used for each joint.
Beads = 15o from vertical or 75o from the work.
Butt joint = 15o from vertical or 75o from the work.
Lap joint = 45o.
T joint = 45o.
Corner = 15o from vertical or 75o from the work.
Excessive—poor puddle geometry
Insufficient—reduced penetration, tall narrow bead
What is the effect of incorrect travel angle?

21. Five (5) Factors Electrode Angle-cont.
The work angle is the angle of the electrode perpendicular to the joint.
The appropriate angle must be used for each joint.
Beads = 90o
Butt joint = 90o
Lap joint = 45o
T joint = 45o
Corner = 90o
Can you think of a situation where the travel angle should be modified?
When completing a joint with metal of different thickness.

22. Five (5) Factors 4. Arc Length
The arc length is the distance from the metal part of the electrode to the weld puddle.
The best arc length is not a fixed distance, but should be approximately equal to the diameter of the electrode.
What are the characteristics of a weld completed with excessive arc length?
Excessive length
Excessive spatter
Reduced penetration
Poor quality weld
Electrode sticks
Narrow weld
What are the characteristics of a weld completed with insufficient arc length?

23. Five (5) Factors 5. Speed of Travel
The speed of travel is measured in inches per minute.
What factors determine the best speed of travel?
The size of the joint,
The type of electrode
The size of the electrode
The current setting on the machine
Deposition rate of the electrode (cubic inches per minute)

24. Five (5) Factors 5. Speed-cont.
The ideal speed can be calculated using the volume of the joint and the deposition rate of the electrode.
Step one: determine the area of the weld. (Assuming 1/16 inch penetration.)
Step Two: knowing the deposition rate of the electrode, determine the welding speed. (Deposition rate = 2.5 in3/min.)

25. Five (5) Factors 5. Speed-cont.
The correct welding speed is indicated by the shape of the ripples.
Too slow = excessive width, excessive penetration
Too fast = narrower width, elongated ripple pattern, shallow penetration.
Recommended = width 2-3 times diameter of electrode, uniform ripple pattern, full penetration.

26. SMAW Joints

27. Square Groove
A butt joint can be completed with a groove welded on metal up to 1/8 inch thick with a single pass on one side, with no root opening.
Electrode manipulation should only be used to prevent burning through.

28. Square Groove Thicker Metal
A groove weld on metal up to 1/4 inch thick can be welded with a single pass on one side but, if possible, it should be completed with a single pass on both sides.
Metal this thick requires a root opening to achieve adequate penetration.
Electrode manipulation will reduce penetration.

29. Single V Groove Weld
Butt joints on metal greater than 1/4 inch thick require joint preparation.
Note that the groove does not extend all the way. A short distance, called the root face, is left undisturbed.
Several different combinations of passes can be used to complete this joint.
What determines that amount of joint preparation that must be done before welding?
The purpose of the joint preparation is to compensate for not having sufficient amperage and electrode diameter.
Note: this is the principle use of pattern beads.

30. T-Joints

31. Information
In a T-joint the two welding surfaces are at an angle close to 90 degrees from each other.
The welding side and number of passes uses depends on the thickness of the metal, the welding access and capacity of the power supply.
Common joints include.
Plane T
T with joint gap
Single preparation
Double preparation

32. Plane T-Joint The plane T joint is very useful for thin metal.
Can be completed at angles other than 90 degrees.
Can be completed with metal of different thickness.
The work angle must be changed to direct more heat to the thicker piece.

33. T-joint--Thicker Metal
When the metal thickness exceeds 1/8 inch the recommendation is to gap the joint.
Improves penetration
May not be necessary if larger diameter electrode is used and sufficient amperage is available.
The need for a joint gap varies with the type of electrode, but should not exceed 1/8 inch.

34. T-joint Single Single Bevel
As with other joints, thicker metal must have joint preparation to achieve full penetration with smaller diameter electrodes.
Several different preparations can be used. A popular one is the bevel.
A bevel can be completed by grinding or cutting.
The bevel joint can be completed with electrode manipulation or no electrode manipulation.
When when electrode manipulation is used to fill the joint, the first pass should be a straight bead with no manipulation.

35. T-joint Double Bevel
The double bevel T-joint is recommended for metal 1/2 inch thick and thicker.
The root passes should be with not manipulation, but the filler passes can be completed with either straight beads or patterns beads.
Alternating sides reduces distortion.

36. Weld Defects

37. Common SMAW Defects Hot cracks Undercutting Slag inclusions Porosity
Caused by excessive contraction of the metal as it cools.
Excessive bead size
May also be found at the root of the weld.
Slag inclusions
Long arc
Incomplete removal of slag on multipass welds.
Undercutting
improper welding parameters; particularly the travel speed and arc voltage.
Porosity
Atmospheric contamination or excess gas in the weld pool.

38. SMAW Weld Defects-cont.
Incomplete fusion
Toe cracks
Microcracks
Underbead cracks
Toe Cracks
Excessive heat and rapid cooling.
Underbead cracks
Excessive hydrogen in weld pool
Microcracks
Caused by stresses as weld cools.
Incomplete fusion
Incorrect welding parameters or welding techniques.

39. Questions