1. Shielded Metal Arc Welding
TSM 233: Unit 5
Shielded Metal Arc Welding

2. What is SMAW?
The SMAW process is accomplished by producing an electric arc between the base metal and a consumable flux-covered electrode.

3. What are the basic components of the SMAW process?
Welder
Leads
Electrode holder
Ground clamp
Electrode

4. What are some specific safety precautions for SMAW?
Produces intense ultra-violet rays.
Need to use number 10 or 12 shade lens.
U-V rays burn the outer layers of the skin/eyes.
Electrical shock.
Toxic fumes/smoke.
Heat exposure.

5. How does the SMAW process produce heat?
Volt –electrical pressure
Amperage – amount of electricity
Resistance – produces heat.
Welder works at a lower voltage, pushes large amounts of electricity, across a gap.
Voltage drops, amperage increases as the arc length decreases.

6. What are the key variables when SMAW?
Type of metal, thickness, weld-ability.
Type of weld, characteristics, position.
Types of electrodes.
Types of electrical current, amperage range.
Welder (person) characteristics, speed, skill, electrode angles.

7. What are the different types of SMAW welders?
Two basic types:
Constant current – preset the amperage, used mostly for SMAW and GTAW (TIG)
Constant potential (voltage), preset the voltage, GMAW (MIG) and FCAW (Flux Core)

8. AC –alternating current DC – direct current
What are the characteristics of the different types of electrical current used for SMAW?
AC –alternating current
DC – direct current
DCEN – electrode negative, straight polarity, greater deposit of metal and thinner metal. (electricity flows from the (-) negative pole to the positive (+) pole
DCEP – reverse polarity, electrode positive, heat is greater at the metal, deeper penetration.

9. How are different types of electricity produced by the welders?
AC is easier to get from electrical service,
DC is easier to produce from a generator.
Generators – produces the electricity, need an alternator to produce AC. To get DC from an alternator, convert the AC to DC.
Static Converted power
Transformer – very common, most lighter duty welders, changes the voltage/amperage.
Rectifier – converts AC to DC.
Inverter – converts the 60 mHz to High Frequency, 1000 – 50,000mHz., actually….
AC to DC to HFAC to Transformer to DC

10. Factors to consider when selecting SMAW welders.
Input Voltage.
Whether need AC and/or DC.
Duty Cycle: the ratio of welding time to total time.
Whether planning to also use the welder for GTAW.

11. How are welders classified?
Welders are classified by their duty cycles for the rated output.
Class I: 60%, 80% and 100% duty cycles.
Class II: 30%, 40%, and 50% duty cycles.
Class III: 20% duty cycle

12. What types of metals can we SMAW?
Most all common metals, except Magnesium.
Aluminum and Copper alloys are very difficult
SMAW is still the most common, widely used type of welding process.

13. What to consider when selecting electrodes?
type of base metal
weld groove design
required tensile strength
position of the weld joint
the rate of desired weld deposit
the type of electrical current available

14. How do we identify the different types of electrodes?
E – Electrode
60 – tensile strength in 1,000#
1 – position (1=all, 2=flat/horizontal only)
1 – special characteristics, flux, current.

15. What are some of the different types of electrodes?
Low-Alloy Steel Covered Electrodes
Low Hydrogen Electrodes
Stainless Steel Electrodes
Cast Iron Electrodes
High Tensile Strength Electrodes
Aluminum Electrodes
Copper and Copper Alloy Electrodes
Hard-facing/surfacing Electrodes

16. Low-Alloy Steel Covered Electrodes
E6010 High cellulose, sodium DCEP
E6011 High cellulose, potassium AC/DCEP
E6012 High titania, sodium AC/DCEN
E6013 High titania, potassium AC/DC
E7014 Iron powder, titania AC/DC
E7024 Iron powder, titania AC/DC
Suffixes: A,B…G.

17. Low Hydrogen Electrodes
E7015 Low hydrogen, sodium DCEP
E7016 Low hydrogen, potassium AC/DCEP
E7018 Low hydrogen, potassium, iron powder AC/DCEP
E7028 Low hydrogen, potassium, iron powder AC/DCEP

18. Why use “stringer” type beads and “weave” type bead?
Stringer Beads, welded with little side to side motion
Weave beads use a deliberate side to side motion.
Stringer beads:
easier to perform
generally a smoother finish.
Less metal mass, therefore less potential distortion
generally less penetration, less overall strength
Weave beads:
generally greater strength.
More metal deposited
Potentially deeper penetration.
A “back and forth” forward motion is also often used to increase penetration and to help “freeze” the weld puddle
An “in and out” motion is used to help freeze puddle, used for out-of-position welds, called a “whip” motion.

19. When should we groove the metal for welding?
Grooving is used to help insure deeper weld penetration.
Recommended when the base metals are equal to, or greater than twice the thickness of the electrode core wire diameter.
Generally a 60 degree angle, not less than 45 degrees.
Do not groove to a sharp point, leave a “root face” equal to the diameter of the electrode core wire.
Use multiple passes:
first pass is the “root pass”
the last pass is a “wash pass” which uses a wide weave pattern to cover the pervious passes.

20. How do we store electrodes?
Moisture and extreme temperature changes can harm/destroy electrodes.
Store in a dry, air-tight environment.
Commercial electrode storage cabinets are available, provide a warm, low humidity environment.
Low hydrogen electrodes are very sensitive to moisture, and must be stored in a continuous dry environment.
Heating electrodes in an oven above 212 degrees can help “dry” and restore electrodes.

21. What is “arc blow” and what can we do to reduce it?
Arc Blow is caused by a distorted magnetic attraction of the electric arc to the base metal.
The arc “curves” to one side.
Or “jumps” from side to side in an inconsistent pattern.
Generally a problem when using DC welding current
Causes metal to be deposited to one side of the weld.
How to control?
Switch to AC.
Move the ground clamp
Use intermittent welds
Use a weave pattern.

22. What is a weld “undercut” and what can we do to reduce it?
Undercut is when the weld has a depressed area between the bead and base metal.
Can be caused by:
electrode side angle
too high amperage
poor weave pattern
wrong type of electrode, too “hot”
base metals are too dissimilar

23. Weld Heat Affected Zone

24. Types of Groove Welds

25. Welding Positions