Advanced Shielded Metal Arc Welding (SMAW)

Course Overview and Fundamental Principles

Definition of Welding: Welding is the joining together of two pieces of metal by heating to a temperature high enough to cause softening or melting, with or without the application of pressure, and with or without the use of filler metal. Any filler metal used has either a melting point approximately the same as the metals being joined or a melting point that is below these metals but above $800\,^{\circ}\text{F}$ .
Shielded Metal Arc Welding (SMAW): The most widely used welding process in fabrication due to its low cost, flexibility, portability, and versatility. It is a manual arc welding process where heat is generated by an electric arc established between a flux-covered consumable metal rod (electrode) and the workpiece. Also known as stick electrode welding.
Gaseous Shielding Mechanism: Combustion and decomposition of the electrode flux coating creates a gaseous shield that protects the electrode tip, weld puddle, arc, and highly heated workpiece from atmospheric contamination.
Key Requirements for Welder Success: Demands proper manipulation of the weld puddle through hand-eye coordination, adherence to correct procedures, precise control of welding variables, knowledge of base materials, electrode selection, equipment setup, joint design, and welding position.
Core Course Outcomes:
- Summarize advanced principles of shielded metal arc welding.
- Develop skills and knowledge in setting up various SMAW equipment.
- Develop skills and knowledge in operating various advanced SMAW processes.
- Explain and internalize essential welding principles and processes.
- Adopt proper attitudes in caring for and maintaining welding tools and equipment.
- Apply safety essentials across various welding operations.

History and Industrial Evolution of Welding Technology

19th Century: Edmund Davy discovered acetylene ( $\text{C}_2\text{H}_2$ ), a gas later utilized extensively in oxyacetylene welding, heating, and cutting.
1801: Sir Humphry Davy first discovered the electric arc while conducting experiments in electricity.
1809: Sir Humphry Davy demonstrated that a high-voltage arc could be maintained for varying periods of time.
Middle of 19th Century: Workable electrical generating devices were invented and developed on a practical basis.
1881: Auguste de Meritens accomplished the first documented instance in fusion welding by joining lead battery plates together using a carbon electrode. A British patent was issued four years later (1885).
1888: Bare metal electrode welding was introduced by N.G. Slavianoff, a Russian engineer. Recognized in Western Europe in 1892, bare electrode welding became the prevailing electric arc welding method in the United States until approximately 1920.
1907: Kjellberg, a Swedish engineer, received a patent covering the electrode-coating process.
1912: Kjellberg received another patent for an electrode featuring a heavier coating made of asbestos with a binder of sodium silicate.
World War I Era: Prior to World War I, welding technology and industrial application progressed slowly, serving chiefly as a maintenance and repair tool. By the end of World War I, welding achieved broad acceptance.
1920s: Focused research improved coated electrodes and core wire composition.
1930s: Considerable research was carried out with alternating current (AC) for welding.
1930: Hobart and Devers received a patent for utilizing an electric arc within an inert gas atmosphere.
1936: High-frequency stabilized AC industrial welding machines were introduced by the Miller Electric Manufacturing Company.
World War II Era: WWII spurred the development of inert gas welding, making high-purity welds for critical applications possible.
1942: Linde Company obtained a license to develop Gas Tungsten Arc Welding (GTAW), initially performed with rotating DC welding machines.
1948: The U.S. Patent Office issued a patent for the Gas Metal Arc Welding (GMAW) process. The term GMAW superseded earlier terms like Metal Inert Gas (MIG) and Metal Active Gas (MAG).
1950: AC GTAW machines with built-in high frequency were developed.
1970: All-position flux-cored wires became commercially available.
1980s to Present: Rapid evolutionary changes continue as engineers design advanced filler metal formulas to enhance arc performance and weld quality on exotic materials. Today, over 90 distinct welding processes are in active use.

Welding Governing Bodies and Standards Associations

American National Standards Institute (ANSI): Provides broad oversight for national standardization systems.
American Petroleum Institute (API): Sets standards for oil, gas, and petrochemical industry fabrication and piping.
American Society of Mechanical Engineers (ASME): Establishes codes for pressure vessels, boilers, and industrial machinery.
American Welding Society (AWS): Sets standard procedures, symbols, electrode specifications, and welder qualifications.
American Bureau of Shipping (ABS): Establishes guidelines and standards for marine vessels and offshore structures.

Overview of Major Welding Processes

Oxyfuel Gas Welding (OFW):
- Produces coalescence by heating materials with an oxyfuel gas flame or flames, with or without pressure, and with or without filler material.
- One of the oldest processes; historically termed gas welding. Acetylene ( $\text{C}_2\text{H}_2$ ) remains the most popular fuel gas.
Shielded Metal Arc Welding (SMAW):
- Produces coalescence by heating workpieces with an arc between a flux-covered consumable metal electrode and the workpiece.
- Shielding gas is derived entirely from flux decomposition; no pressure is used; filler metal comes from the melting electrode core.
Gas Tungsten Arc Welding (GTAW):
- Produces coalescence by heating materials with an arc between a nonconsumable tungsten electrode and the workpiece.
- Shielded by an externally supplied gas (inert gas). Also referred to as TIG (Tungsten Inert Gas) or Heliarc.
- Tungsten electrode does not melt under proper conditions; base metal melts to form a molten weld pool. Filler metal is optional.
Gas Metal Arc Welding (GMAW):
- Produces coalescence with an arc between a continuous, automatically fed solid filler metal electrode wire and the workpiece.
- Shielding is obtained entirely from an externally supplied gas.
Flux Cored Arc Welding (FCAW):
- Produces coalescence with an arc between a continuous tubular filler metal electrode and the workpiece.
- Shielding is provided by flux contained within the tubular wire; auxiliary external shielding gas may or may not be used.
Submerged Arc Welding (SAW):
- Produces coalescence by heating with an arc (or arcs) between a bare metal electrode (or electrodes) and the workpiece.
- The arc and molten metal are completely shielded beneath a blanket of granular, fusible material (flux) on the workpiece. Pressure is not used.
Plasma Arc Welding (PAW):
- Produces coalescence by heating with a constricted arc between a nonconsumable electrode and the workpiece (transferred arc), or between the electrode and the constricting nozzle (nontransferred arc).
- Shielding is obtained from hot, ionized gas (plasma) issuing from the torch, optionally supplemented by an auxiliary shielding gas mixture.

Industrial Applications and Career Opportunities

Essential Skills for Welders: Complete mastery requires proficiency in manual welding techniques, blueprint/drawing reading, applied mathematics, and computer operations.
Certification: Qualified welders obtain certification through testing bodies such as AWS, ASME, and API, which require rigorous training and practice.
Sectors Utilizing Welding Infrastructure:
- Aircraft
- Automotive
- Bridge building
- Construction equipment
- Farm equipment and appliances
- Furnaces and heating equipment
- Guided missiles and spacecraft
- Jigs and fixtures
- Machine tools
- Military equipment
- Mining equipment
- Oil drilling and refining equipment
- Ornamental iron work
- Piping
- Quality food service equipment
- Railroad equipment
- Residential, commercial, and industrial construction
- Sheet metal
- Steel mill equipment
- Tanks and boilers
- Tools and dies
- Watercraft

Shielded Metal Arc Welding Safety Standards

Core Safety Principle: Accident prevention relies on caution, common sense, and personal responsibility. Safety cannot be assumed; it requires deliberate work.
Primary Welding Hazards and Mitigations:
- Fumes and Gases:
  - Hazard: Toxic fumes cause serious respiratory damage.
  - Precaution: Keep head out of fume plume. Utilize local exhaust ventilation at the arc or sufficient general room ventilation to keep breathing zone clean. Consult Material Safety Data Sheets (MSDS) and product labels.
- Electric Shock:
  - Hazard: Primary input voltage ( $230\,\text{V}$ or $460\,\text{V}$ ) and secondary welding output voltage ( $6\,\text{V}$ to $100\,\text{V}$ ) can cause fatal electrocution.
  - Precaution: Never touch live electrical parts. Dry insulation must be maintained between the welder's body, the workpiece, and the ground (using rubber mats or dry wood). Wear dry, hole-free leather gloves. Change damp gloves immediately. If working in damp environments where body insulation is impossible, use semiautomatic constant-voltage equipment or a stick welder fitted with a voltage-reducing device. Maintain electrode holder and cable insulation in flawless condition.
- Arc Rays:
  - Hazard: The arc produces intense ultraviolet (UV) and infrared radiation brighter than the sun, causing severe eye burn (arc eye) and skin burns.
  - Precaution: Wear protective welding helmets fitted with appropriate filter lenses. Wear nonflammable protective clothing fully covering exposed skin. Erect nonflammable shielding screens to protect bystander workers.
- Fire and Explosion Hazards:
  - Hazard: Sparks and molten spatter can spray up to $35\,\text{ft}$ ( $10.7\,\text{m}$ ) from the welding arc.
  - Precaution: Remove all combustible materials from a $35\,\text{ft}$ radius or cover them with fireproof blankets. Maintain a active fire watch during welding and for at least $30\,\text{minutes}$ after welding ceases. Keep operational fire extinguishers in the immediate work area. Never weld on tanks or containers that previously held combustible substances unless strict procedures defined in AWS F4.1 are executed.
- Noise:
  - Hazard: High decibel levels cause permanent hearing loss.
  - Precaution: Wear approved ear plugs or ear muffs.
- Protective Clothing Checklist:
  - Fire-proof clothing without rolled sleeves, cuffs, or open frays.
  - Heavy-duty leather work boots.
  - Flame-retardant welding gloves, jackets, bibs, leather sleeves, and fire-proof pants.
  - Welding cap, helmet, and safety glasses with side shields.
  - Earplugs during overhead welding operations to prevent falling spatter from entering ear canals.

Welding Power Sources and Machine Types

Step-Down Transformers:
- Converts high-voltage, low-amperage utility primary power into low-voltage, high-amperage welding power.
- Standard choice in industry because they are quiet, highly energy-efficient, low-maintenance, and cost-effective.
- Primary Components:
  - Primary Coil: Winding connected directly to incoming utility electrical power.
  - Secondary Coil: Winding where welding current is induced; connected to welding leads (electrode and work cables).
  - Core: Constructed of laminated steel sheets; concentrates the magnetic field generated by the primary winding into the secondary winding.
Multiple-Coil (Tap-Type) Welders:
- Adjusts current settings by physical taps connected into the secondary coil at varying turn values.
- Greater number of active secondary turns yields higher output amperage.
- May feature fixed amperage tap steps or fine-tuning adjustment knobs marked in fractional/decimal units.
Movable-Coil or Movable-Core Welders:
- Adjusted by turning a hand wheel or operating a lever to physically shift internal components.
- Closer proximity between primary and secondary coils increases induced current; moving them farther apart decreases current.
- Moving the laminated iron core inward concentrates more magnetic force lines on the secondary coil, increasing current output.
Inverter-Type Welders:
- Utilizes solid-state electronic components to transform standard incoming power ( $60\,\text{Hz}$ / $60\,\text{cycles/s}$ ) into high frequencies ranging in several thousand cycles per second.
- High frequency enables a transformer weighing as little as $7\,\text{lb}$ ( $3.2\,\text{kg}$ ) to perform electrical work equivalent to a conventional power transformer weighing $100\,\text{lb}$ ( $45.4\,\text{kg}$ ).
- Offers unmatched portability, ultra-compact physical footprints, and superior energy efficiency.
Engine-Driven Generators and Alternators:
- Produce welding current driven by mechanical internal combustion engines for field operations.
- Alternators:
  - Magnetic lines of force rotate (rotor) inside a stationary coil of wire (stator).
  - Produces Alternating Current (AC) natively.
  - Welding current is generated directly on the stator; only tiny field excitation currents pass through brushes. Brushes are smaller and last much longer.
  - Lighter, smaller, and highly efficient.
- Generators:
  - Coil of wire (armature) rotates inside a magnetic force field.
  - Capable of producing AC or Direct Current (DC).
  - Welding current is generated on the spinning armature and collected via heavy-duty carbon brushes riding on a commutator.

Rectification and Current Conversion

Rectifiers: Solid-state electrical components that permit current to flow in only one direction, converting AC to DC.
Bridge Rectifiers: An arrangement of multiple rectifiers designed to smooth out pulsating single-rectified power into stable Direct Current suitable for welding.
Heat Loss and Power Efficiency:
- Rectification produces substantial heat; components must be mounted on heat sinks and continuously fan-cooled.
- Heat generated inside rectifiers represents wasted power. Consequently, at identical machine dial settings, DC output yields lower net amperage than AC output.
- Operating directly on AC is more energy-efficient and less expensive than operating on DC.

Welding Current Principles and Electrical Measurements

Electron Motion: Electric current is defined as the flow of electrons from negative ( $-$ ) to positive ( $+$ ). Electrical resistance encountered during electron flow generates heat. Higher resistance produces higher thermal energy in the arc.
Voltage ( $\text{V}$ ):
- Measurement of electrical pressure (analogous to $\text{psi}$ in fluid systems).
- Controls maximum gap distance electrons can jump to establish and maintain the arc.
- Directly associated with welding arc temperature.
Amperage ( $\text{A}$ ):
- Measurement of the total number of electrons flowing per second (analogous to flow rate in gallons).
- Controls the physical size of the arc pool and rate of electrode deposition.
- Directly associated with welding arc heat.
Wattage ( $\text{W}$ ):
- Measurement of absolute electrical power generated in the arc.
- Calculated using the formula: $\text{Wattage} = \text{Voltage} \times \text{Amperage} \quad (W = V \times A)$
- Directly associated with total welding power (combined heat and temperature capacity).

Types of Welding Current Polarity

Direct Current Electrode Negative (DCEN):
- Setup: Electrode is connected to negative ( $-$ ); workpiece is connected to positive ( $+$ ). Historically termed Direct Current Straight Polarity (DCSP).
- Heat Distribution: Electrons travel from the electrode tip to the workpiece, placing approximately one-third ( $1/3$ ) of total arc heat on the electrode and two-thirds ( $2/3$ ) on the workpiece.
- Performance: Yields rapid electrode melting rates and high deposition.
Direct Current Electrode Positive (DCEP):
- Setup: Electrode is connected to positive ( $+$ ); workpiece is connected to negative ( $-$ ). Historically termed Direct Current Reverse Polarity (DCRP).
- Heat Distribution: Electrons travel from the workpiece to the electrode tip, placing approximately two-thirds ( $2/3$ ) of total arc heat on the electrode and one-third ( $1/3$ ) on the workpiece.
- Performance: Provides superior arc stability, deep joint penetration, and optimal overall arc characteristics.
Alternating Current (AC):
- Setup: Current reverses direction $120$ times per second ( $60\,\text{Hz}$ frequency), altering electrode and work between anode and cathode every $1/120\,\text{s}$ .
- Heat Distribution: Arc heat is split evenly: half ( $1/2$ ) on the workpiece and half ( $1/2$ ) on the electrode.
- Performance: Balances penetration depth and weld bead buildup. Helps prevent magnetic arc blow.

Welding Accessories and Cable Setups

Welding Cables (Leads):
- Must feature high flexibility and durable insulation.
- Copper Cables: Standard material composed of fine-stranded copper wire.
- Aluminum Cables: Lighter and cheaper than copper. Because aluminum has lower electrical conductivity than copper, aluminum cables must be selected one trade size larger than required copper cables.
Electrode Holders (Stinger):
- Must be rated for the maximum amperage used. Exceeding rated amperage causes rapid overheating and insulation destruction.
- Over-sized holders cause excessive hand fatigue and hinder precise hand-eye manipulation.
Work Clamps:
- Must clamp tightly onto clean base material to avoid high electrical resistance.
- Loose or undersized work clamps cause substantial voltage drops, severe heat buildup in the clamp, and accidental electrical arcing that damages parts.
- Swivel-type clamps or temporary welded tabs are utilized on heavy structural shapes.

Operational Welding Variables

Machine Settings:
- Current/Polarity Selection: AC, DCEP ( $\text{DC}^+$ ), or DCEN ( $\text{DC}^-$ ).
- Amperage Output setting.
Operator-Controlled Variables:
- Work Angle: The angle maintained between the centerline of the electrode and the surface of the base metal plane.
- Travel Angle (Lead Angle): The angle maintained between the centerline of the electrode and a line perpendicular to the weld axis along the direction of travel.
- Arc Length: The distance from the tip of the electrode core wire to the surface of the molten weld pool.
  - Standard maintained distance is $1/8\,\text{in}$ ( $3.2\,\text{mm}$ ).
  - Too short: Electrode freezes/sticks to workpiece or shorts out.
  - Too long: Produces violent spatter, loss of directional control, heavy undercut, and atmospheric porosity.
- Travel Speed: The linear rate at which the electrode is advanced along the joint.
  - Too fast: Produces a narrow, high-crowned, convex, "ropey" weld bead with poor fusion.
  - Too slow: Produces an excessively wide, flat weld bead with potential slag inclusions and heavy weld deposit.

SMAW Electrode Classification and Numbering System

Electrode Structure: Consists of a central solid metallic Core Rod (which carries electrical current and becomes filler metal) wrapped in an extruded Flux Coating (which forms protective shielding gas, adds deoxidizers, stabilizes the arc, forms protective slag, and can contribute alloying elements/metal powder).
AWS Identification System (Mild and Low-Alloy Steel):
- Prefix E: Designates an arc welding electrode.
- First Two Digits of a 4-Digit Number (or First Three Digits of a 5-Digit Number): Represents minimum tensile strength in thousands of pounds per square inch ( $\text{psi}$ ).
  - Example: \textbf{E6010} = $60,000\,\text{psi}$ minimum tensile strength.
  - Example: \textbf{E10018} = $100,000\,\text{psi}$ minimum tensile strength.
- Next-to-Last Digit: Designates allowable welding positions:
  - $\textbf{1}$ : All positions (Flat, Horizontal, Vertical, Overhead).
  - $\textbf{2}$ : Flat and Horizontal fillet positions only.
  - $\textbf{4}$ : Flat, Horizontal, Overhead, and Vertical-Down positions.
- Last Two Digits Combined: Designates type of flux coating, arc characteristics, penetration capabilities, and required current/polarity:
  - $\textbf{0}$ : High cellulose sodium coating; requires DCEP ( $\text{DC}^+$ ).
  - $\textbf{1}$ : High cellulose potassium coating; operates on AC, DCEP ( $\text{DC}^+$ ), or DCEN ( $\text{DC}^-$ ).
  - $\textbf{2}$ : High titania sodium coating; operates on AC or DCEN ( $\text{DC}^-$ ).
  - $\textbf{3}$ : High titania potassium coating; operates on AC or DCEP ( $\text{DC}^+$ ).
  - $\textbf{4}$ : Iron powder titania coating; operates on AC, DCEP ( $\text{DC}^+$ ), or DCEN ( $\text{DC}^-$ ).
  - $\textbf{5}$ : Low hydrogen sodium coating; requires DCEP ( $\text{DC}^+$ ).
  - $\textbf{6}$ : Low hydrogen potassium coating; operates on AC or DCEP ( $\text{DC}^+$ ).
  - $\textbf{7}$ : High iron oxide, iron powder coating; operates on AC, DCEP ( $\text{DC}^+$ ), or DCEN ( $\text{DC}^-$ ).
  - $\textbf{8}$ : Low hydrogen potassium, iron powder coating; operates on AC, DCEP ( $\text{DC}^+$ ), or DCEN ( $\text{DC}^-$ ).

Common SMAW Electrodes and Operating Characteristics

E6010:
- DCEP ( $\text{DC}^+$ ) only. Deepest arc penetration available.
- Digs effectively through heavy rust, mill scale, oil, paint, and dirt.
- Primary choice for open-root pipe welding (vertical-down cross-country pipelines).
E6011:
- AC or DCEP ( $\text{DC}^+$ ). Deep penetrating arc.
- All-position equivalent to E6010 for utility transformer machines where DC current is unavailable; ideal for repair/maintenance on unclean metal.
E6013:
- AC, DCEN ( $\text{DC}^-$ ), or DCEP ( $\text{DC}^+$ ).
- Soft arc, low spatter, shallow penetration, and easily cleanable slag; designed for clean sheet metal fabrication.
E7014:
- AC, DCEN ( $\text{DC}^-$ ), or DCEP ( $\text{DC}^+$ ).
- Iron powder titania coating (Fast Fill). Smooth bead surface, fine ripples, easily removed slag. Ideal for high-speed production on mild steel.
E7015:
- DCEP ( $\text{DC}^+$ ) low hydrogen electrode.
- Moderate penetration, heavy friable slag. Designed for high-carbon, high-sulfur, alloy steels, and enameling stock.
E7016:
- AC or DCEP ( $\text{DC}^+$ ) low hydrogen electrode.
- Similar operating characteristics to E7015 with added AC operational capability.
E7018:
- AC or DCEP ( $\text{DC}^+$ ) low hydrogen electrode with iron powder.
- All-position, top choice for structural code work, high-yield steels, and restraint joints.
- Produces exceptional impact strength properties at sub-zero temperatures.
E7024:
- AC, DCEN ( $\text{DC}^-$ ), or DCEP ( $\text{DC}^+$ ).
- Heavy iron powder content; limited to flat downhand and horizontal fillet welds on plate thickness $\ge 1/4\,\text{in}$ ( $6.4\,\text{mm}$ ), optimized for plate $\ge 1/2\,\text{in}$ ( $12.7\,\text{mm}$ ).
E7028:
- AC or DCEP ( $\text{DC}^+$ ).
- Horizontal fillet and flat position low hydrogen electrode containing heavy iron powder; produces flat-to-concave profiles.
E7048:
- AC or DCEP ( $\text{DC}^+$ ).
- Low hydrogen electrode formulated specifically for high-speed vertical-down progress in structural joints.
Suffix Designators (e.g., E8018-B2H4R):
- B2: Chemical deposit composition designation (alloy classification).
- H4: Diffusible hydrogen level designator (specifies maximum $4\,\text{mL}$ diffusible hydrogen per $100\,\text{g}$ of deposited weld metal).
- R: Moisture resistance designator indicating electrode meets strict low moisture absorption limits under humidified testing conditions.

Alloy and Stainless Steel Electrodes

Alloy Steel Electrodes: Tensile strengths span 80XX, 90XX, 100XX, 110XX, and 120XX ratings. Operating characteristics mirror E7015, E7016, and E7018 low-hydrogen types.
Stainless Steel Classifications and Recommended Electrodes:
- Austenitic (AISI 300 Series):
  - 302, 303, 304, 308 ( $18/8$ or $19/9$ chemistry) $\rightarrow$ E308-15, E308-16
  - 309 ( $25/12$ chemistry) $\rightarrow$ E309-15, E309-16, E309Cb-15, E310-15, E310-16
  - 310 ( $25/20$ chemistry) $\rightarrow$ E310Cb-15, E310Cb-16, E310Mo-15, E310Mo-16
  - 312 ( $29/9$ chemistry) $\rightarrow$ E312-15, E312-16, E316-15, E316-16
  - 316 ( $18/12\text{Mo}$ chemistry) $\rightarrow$ E316Cb-15, E316Cb-16
  - 317 ( $18/12\text{Mo}$ chemistry) $\rightarrow$ E317-15, E317-16
  - 330 ( $15/35$ chemistry) $\rightarrow$ E330-15, E330-16
  - 347 ( $18/8\text{Cb}$ chemistry) $\rightarrow$ E347-15, E347-16
- Straight-Chromium (AISI 400 Series):
  - 410 ( $12\%$ Chromium) $\rightarrow$ E410-15
  - 430 ( $16\%$ Chromium) $\rightarrow$ E430-15
  - 442 ( $18\%$ Chromium) $\rightarrow$ E442-15
  - 446 ( $28\%$ Chromium) $\rightarrow$ E446-15
- Straight-Chromium (AISI 500 Series):
  - 502 ( $5\%$ Chromium) $\rightarrow$ E502-15, E502-18, E505-18
  - 550 ( $9\%$ Chromium) $\rightarrow$ E502-16, E505-18
Pipe Welding Selection Guidelines:
- EXX10: Standard for vertical-down cross-country lines due to steady concentrated arc, thin slag, wetting ability, and minimal pinholes on stringer root passes.
- EXX10 & EXX18 Combined: Used in industrial vertical-up piping (EXX10 for root stringer bead, EXX18 for fill and cap passes).
- Low Hydrogen (E7018, E7048): Required on high-yield strength pipe materials and high-pressure lines requiring X-ray inspection quality.

Welding Symbols and Blueprint Interpretation

Standard Governing Symbol Application: ANSI/AWS A2.4 (Standard Symbols for Welding, Brazing, and Nondestructive Examination).
Structure of the Standard Welding Symbol:
- Reference Line: Always drawn horizontally. Base on which all weld symbols and dimensions are placed.
- Arrow: Connects the reference line to the joint to be welded.
- Arrow Side (Near Side): Weld elements placed below the horizontal reference line apply to the side of the joint touched by the arrow tip.
- Other Side (Far Side): Weld elements placed above the horizontal reference line apply to the opposite side of the joint.
- Both Sides: Identical symbols placed above and below the reference line.
- Tail: Added to the opposite end of the reference line only when process specifications, electrode types, root gouging, or supplementary procedures are referenced. Omitted if unnecessary.
Basic Symbols for Specific Welds:
- Fillet Weld: Right triangle symbol.
- Plug or Slot Weld: Rectangular symbol.
- Groove Welds: Square, V, Bevel, U, J, Flare-V, Flare-Bevel contours.
- Flange Welds: Edge flange or corner flange symbols.
Dimension Placement Rules:
- Fillet Welds: Size (leg length) is placed to the left of the symbol. Length of the weld is placed to the right of the symbol. Unequal legs are shown in parentheses: e.g., $(1/4 \times 3/8)$ .
- Intermittent Fillet Welds: Designated to the right of the weld symbol as length-pitch: e.g., $2-5$ (designates a $2\,\text{in}$ long weld segment spaced every $5\,\text{in}$ center-to-center). Serves to limit heat input and act as crack-stoppers.
- Plug Welds: Size/diameter placed to the left; angle of countersink placed above/below; depth of fill inside symbol; center-to-center pitch to the right.
- Spot Welds: Size (diameter) or minimum shear strength (in pounds/Newtons) placed to the left; pitch to the right; total quantity of spot welds placed in parentheses above or below the symbol.
- Seam Welds: Size (width) or minimum shear strength per linear inch placed to the left; length placed to the right.
- Groove Welds: Depth of preparation placed to the left; effective throat shown in parentheses to the left: e.g., $3/8\,(1/2)$ . Root opening placed inside the symbol contour. Groove angle placed above/below.
- Backing: Backing strip symbol on opposite side. Inclusion of the letter R inside backing symbol indicates backing strip must be removed after welding.

Joint Design, Edge Preparation, and Welding Positions

Five Basic Joint Designs:
1. Butt Joint: Edges of two plates meet in approximately the same plane.
2. Lap Joint: Members overlap each other; joined by fillet, plug, or seam welds.
3. Tee Joint: Edge of one member meets the surface of another at approximately $90^{\circ}$ .
4. Outside Corner Joint: Edges meet at an approximate $90^{\circ}$ corner angle.
5. Edge Joint: Surfaces of two parallel plates are placed together with edges aligned.
Faying Surface Preparation: Reasons for edge preparation (beveling/grooving) include meeting codes, deep penetration, smooth grind appearance, and achieving $100\%$ joint strength.
Groove Geometry Variations: Square, Single-Bevel, Double-Bevel, Single-V, Double-V, Single-J, Double-J, Single-U, Double-U. Standard groove angles range between $60^{\circ}$ and $90^{\circ}$ (or $30^{\circ}$ in special narrow-groove joint designs).
Plate Welding Positions:
- 1G / 1F (Flat): Weld made from top side of horizontal surface.
- 2G / 2F (Horizontal): Axis of weld is horizontal. For 2F, weld is on top of an approximately vertical surface. For 2G, weld face lies in a vertical plane.
- 3G / 3F (Vertical): Axis of weld is vertical.
- 4G / 4F (Overhead): Weld made from the underside of a joint.
Pipe Welding Positions:
- 1G (Horizontal Rolled): Pipe is rotated continuously or intermittently while welding from the top within $0^{\circ}$ to $15^{\circ}$ of vertical.
- 2G (Vertical Fixed): Pipe axis is vertical; weld axis runs horizontally around the pipe.
- 5G (Horizontal Fixed): Pipe axis is horizontal; weld runs vertically around the stationary pipe.
- 6G (Inclined Fixed): Pipe is fixed at a $45^{\circ}$ angle; weld runs around the pipe.
- 6GR (Inclined Fixed with Restriction Ring): Pipe fixed at $45^{\circ}$ angle with an added restriction ring obstacle located directly below the weld groove.

Review Questions and Self-Assessment Exercises

True/False Assessment

Statement: Plasma welding was referred to as gas welding, although the process today is referred to as oxyacetylene or oxyfuel welding.
Answer: False (Oxyfuel Gas Welding was historically referred to as gas welding).
Statement: SMAW is manual arc welding in which the heat for welding is generated by an electric arc established between a flux-covered consumable metal rod called the electrode and the work.
Answer: True
Statement: GTAW process is sometimes referred to as TIG, or heliarc.
Answer: True
Statement: GMA welding uses a solid welding wire that is fed automatically at a constant speed as an electrode.
Answer: True
Statement: GTAW shielding is provided by a flux contained within the tubular electrode.
Answer: False (FCAW shielding is provided by flux inside a tubular electrode; GTAW uses external shielding gas).
Statement: The arc and molten metal in submerged arc welding are shielded by a blanket of granular.
Answer: True
Statement: Sir Humphry Davy was first discovered the electric arc while conducting experiments in electricity.
Answer: True
Statement: End of World War II when welding was widely accepted.
Answer: False (Welding was widely accepted by the end of World War I).
Statement: 1920’s- research on coated electrodes improved and core wire.
Answer: True
Statement: Today there are 10 welding processes in use.
Answer: False (Today there are over 90 welding processes in use).

Multiple Choice Assessment

An alternating welding current can be converted to direct current by using a series of:
   a. Rectifier
   b. capacitor
   c. transformer
   d. resistor
Answer: a. Rectifier
Much smaller than other types of machines of the same amperage range:
   a. Transformer type
   b. inverter
   c. DC machines
   d. AC machines
Answer: b. inverter
These machines may have a high and low range, but they do not have a fine adjusting knob:
   a. Transformer type
   b. inverter
   c. Movable coil
   d. AC machines
Answer: c. Movable coil
Connected to a high voltage alternating current (AC) that is supplied to the welding shop by the utility company:
   a. inverter
   b. AC machines
   c. DC machines
   d. transformer type
Answer: d. transformer type
The term used to describe the electricity that jumps across the arc gap between the end of the electrode and the metal being welded:
   a. welding current
   b. voltage
   c. resistance
   d. wattage
Answer: a. welding current
Is associated with the welding temperature:
   a. voltage
   b. amperage
   c. wattage
   d. resistance
Answer: a. voltage
Is associated with the welding heat:
   a. voltage
   b. amperage
   c. wattage
   d. resistance
Answer: b. amperage
Associated with welding power or how much heat and temperature an arc produces:
   a. voltage
   b. wattage
   c. amperage
   d. resistance
Answer: b. wattage
The term for DCEN which meant direct-current ________ polarity:
   a. inverter
   b. reverse polarity
   c. straight polarity
   d. transformer
Answer: c. straight polarity
The term for DCEP which meant direct-current ________ polarity:
    a. inverter
    b. straight polarity
    c. reverse polarity
    d. rectifier
Answer: c. reverse polarity
Is a consumable and gets melted during the welding process:
    a. Weld puddle
    b. electrode
    c. arc
    d. shielding gas
Answer: b. electrode
This protects the weld puddle from the atmosphere preventing contamination during the molten state:
    a. Slag
    b. arc
    c. shielding gas
    d. weld puddle
Answer: c. shielding gas
This all-position, AC electrode is used for welding clean, new sheet metal. Its soft arc has minimal spatter, moderate penetration and an easy-to-clean slag:
    a. E6013
    b. E6011
    c. E6010
    d. E7018
Answer: a. E6013
The last two numbers in electrode classification indicate:
    a. Type of coating and current
    b. Position
    c. Tensile strength
    d. Properties of Metal
Answer: a. Type of coating and current
Which of the following electrode is not recommended for welding in all position?
    a. E7018
    b. E7016
    c. E7024
    d. All of the above
Answer: c. E7024 (E7024 is limited to flat and horizontal fillet positions).
In electrode E6013, the 60 indicates:
    a. Tensile strength
    b. welding position
    c. electrode
    d. type of current and coating
Answer: a. Tensile strength
In welding position classification, 1 indicates:
    a. All position
    b. flat
    c. vertical
    d. horizontal
Answer: a. All position
Electrode for welding on rusty, dirty, less-than-new metal and has a deep penetrating arc:
    a. E6013
    b. E6011
    c. E7018
    d. E7024
Answer: b. E6011
Is the popular term for the chromium and chromium-nickel steels:
    a. alloy
    b. stainless steel
    c. aluminum
    d. alloy steel
Answer: b. stainless steel
A low-hydrogen, usually DC, all-position electrode used when quality is an issue or for hard-to-weld metals:
    a. E7018
    b. E7024
    c. E6013
    d. E6011
Answer: a. E7018
Angle between the electrode and the plane perpendicular to the weld axis:
    a. travel speed
    b. work angle
    c. arc length
    d. travel angle
Answer: d. travel angle
The speed at which the electrode moves along the base material while welding:
    a. travel angle
    b. work angle
    c. arc length
    d. travel speed
Answer: d. travel speed
Enables a designer to indicate clearly to the welder, important detailed information regarding the weld:
    a. welding operator
    b. welding parameters
    c. welding symbols
    d. welding codes
Answer: c. welding symbols
Is a piece of metal that is placed on the back side of a weld joint to prevent the molten metal from dripping through the open root:
    a. bevel
    b. groove
    c. backing
    d. flare
Answer: c. backing
Is made by welding through a round hole in the top plate to fuse the bottom plate:
    a. fillet weld
    b. plug weld
    c. seam weld
    d. spot weld
Answer: b. plug weld

Analytical Essay Prompts and Key Technical Perspectives

Industry Selection Rationale: Joining structural construction, piping, or marine sectors provides steady career advancement and high wages due to continuous global demand for certified AWS/ASME infrastructure welders.
SMAW Advantages Over Other Processes: SMAW requires no bulky external gas shielding cylinders, is highly portable for outdoor field construction, operates reliably in windy conditions, is low-cost, and handles dirty or rusty metals effectively via cellulose-coated electrodes.
Accident Management: Immediate mitigation requires isolating power sources during electrical shock events, notifying emergency services, securing active fire watch/extinguishers, and enforcing proper personal protective equipment (PPE).
Equipment Malfunction Response: Switch off incoming machine power immediately, tag out the unit, and report to qualified technical maintenance personnel rather than attempting uncertified internal repairs.
Electrode Selection Importance: Selecting the proper electrode based on base metal chemistry, tensile requirements, joint fit-up, and position prevents joint cracking, lack of fusion, severe spatter, and catastrophic structural failure.
Optimal Welding Position: The flat ( $1\text{G}$ / $1\text{F}$ ) position is most ideal because gravity keeps the molten weld pool contained, permitting larger electrode diameters, higher current settings, faster travel speeds, and maximum metal deposition rates.