Welding Introduction Notes

Introduction

Methods of joining materials have evolved, enhancing living conditions and advancing materials and machinery.

• Early methods: sticks to stones.
• Egyptians: stone tools & gypsum mortar.
• Bronze & Iron Ages: forming, casting, alloying metals.
• Early welding: casting shapes or pouring molten metal to fuse pieces.
• Bronze goat statue: braze welded 1000 years ago.

Industrial Revolution

The Industrial Revolution (1750-1850) brought forge welding.

• Metal heated, hammered until fused.
• Elihu Thomson's resistance welding (1886) was faster.

Fusion Welding

Fusion welding replaced riveting.

• Welding crucial in WWI, kept secret.
• Post-WWI: many welding methods developed.
• Welding is now dependable and economical.

Welding Terminology

Regional terms vary. Oxyacetylene welding is part of oxyfuel gas welding (OFW).

• Oxyacetylene welding (OAW): gas/torch welding.
• Shielded metal arc welding (SMAW): stick/rod welding.
• Use formal terms; learn regional variations.

Welding Defined

AWS defines a weld as localized coalescence by heating/pressure, with or without filler materials.
Welding: joining materials by heating, with/without pressure or filler metal.
A weld combines materials into one piece by:

• Applying heat to soften/melt.
• Using pressure to coalesce.
• Combining heat and pressure.
  Material includes plastics, glass, and ceramics.

Uses of Welding

Modern techniques build ships, buildings, bridges, and machines.

• Enables strong, lightweight aircraft.
• Essential for space exploration.
• Improvements benefit daily life.
• Used in cars, appliances, computers, mining, and construction.
• Applied from dental braces to satellites; virtually everywhere.

Welding and Cutting Processes

Processes vary in heat/pressure application and equipment. Table 1-1 lists processes.

• Popular processes: OAW, SMAW, GTAW, GMAW, FCAW, TB.
• Popular cutting: OAC, PAC.

Welding Processes

Oxyacetylene Welding, Brazing, and Cutting

OAW and TB use the same equipment; OFC uses similar.

• High-temperature flame from oxygen and fuel gas.
• OF welding melts base metal; filler optional, no flux for steel.
• TB heats metal below melting; brazing alloy melts and bonds; flux may be used.
• Used on smaller, thinner metals.

Shielded Metal Arc Welding (SMAW)

SMAW uses a consumable stick electrode.

• Arc melts electrode, becoming part of weld.
• Electrodes: 12 in., 14 in., 18 in. ($300 \, mm$, $350 \, mm$, $450 \, mm$).
• Vaporized flux protects weld metal.
• Fluxes have beneficial functions.
• Equipment: transformer, cables, clamp, holder.
• Offers widest filler metal selection.
• Joins various metal types/thicknesses.

Gas Tungsten Arc Welding (GTAW)

GTAW uses a nonconsumable tungsten electrode.

• Arc melts base metal and filler, manually dipped.
• Shielding gas protects weld metal.
• Remote control starts/adjusts power.
• Cleanest manual process; requires thorough cleaning.
• High-quality welds in critical applications; some alloys require GTAW.

Gas Metal Arc Welding (GMAW)

GMAW uses continuous solid electrode wire.

• Shielding gas flows through the welding gun.
• Arc melts wire and base metal.
• The gas shield protects weld.
• Fast and economical; minimal cleanup.
• Welds thin to heavy metal with adjustments.

Flux Cored Arc Welding (FCAW)

FCAW uses continuous flux core wire.

• Some wires need shielding gas; others self-shield.
• Current melts wire and base metal.
• Vaporizing flux forms a protective cloud; slag covers the weld.
• Offers high quality, versatility, and speed, but slag must be cleaned.
• GMAW and FCAW use similar equipment.
• Semiautomatic: automatic feed, manual gun movement.
• GMAW/FCAW are cost-effective and versatile.

Thermal Cutting Processes

Common processes: oxyfuel cutting (OFC) and plasma arc cutting (PAC).

• Air carbon arc (AAC) is also used.
• Many use laser beam cutting (LBC).

Oxyfuel Gas Cutting

OFC heats steel surface with a high-temperature flame.

• Oxygen stream burns away steel.
• Dependent on oxidation, limited to metals and alloys.
• Cuts steel from fractions of an inch to feet thick.

Plasma Arc Cutting

PAC uses ionized gas to vaporize metal.

• High-pressure air through electrode and tip.
• Ionized air heats and exits at supersonic speeds.
• Cuts almost any metal/alloy.
• Equipment: transformer, torch, cable, clamp, air supply.
• High speeds and low heat reduce distortion.

Selection of the Joining Process

Depends on equipment, operation, quality, location, materials, appearance, size, time, skill, cost, and codes.

• Manual: Welder controls all.
• Semiautomatic: Auto filler, manual manipulation.
• Machine: Mechanically done with observation.
• Automatic: Programmed machine without intervention.
• Automated: Robot-controlled processes.

Occupational Opportunities in Welding

Welding skills are in demand.
Job Classifications:

• Welders: Pass tests to codes.
• Tack Welders: Hold parts in place.
• Welding Operators: Operate welding machines.
• Welders' Helpers: Clean slag, grind welds.
• Welder Assemblers (Fitters): Position parts, interpret blueprints.
• Welding Inspectors: Certified, test on processes, blueprints, symbols, metallurgy.
• Welding Shop Supervisors: Manage jobs and workers.
• Welding Salespersons: Understand processes, marketing skills.
• Welding Shop Owners: Manage businesses, specialize, or subcontract.
• Welding Engineers: Design weldments, advanced degree.

Related Welding Jobs

Engineers and technicians need knowledge of chemistry, physics, metallurgy, electricity, and mathematics.

Training for Welding Occupations

Months of training are needed.

• Entry-level welders: reading, writing, math, communication.
• Some jobs require knowledge of welding, blueprints, symbols, metal properties, and electricity.

Job-Related Skills

Entry-level skills: teamwork, leadership, integrity, time management, diversity.

• Robotics and CAM require computer literacy.
• Need eyesight, dexterity, coordination, technology knowledge.
• Employers prefer vocational training.

Beginning a Welding Career

Beginners start in manual jobs or as helpers.

• Apprenticeships in large companies and military.
• High skill needs: atomic energy, aerospace, pressure vessel construction.

Job Prospects

Skilled welders may qualify as technicians.

• Increased employment due to maintenance and repair.
• Needed in manufacturing, construction, and energy.
• Certification may be required.

Think Green

Minimize environmental impact.

Welding Certification

Certification for welders who pass tests.

Job-Related Personal Skills

Important for teamwork, communication, problem-solving, and technical reading.

Teamwork

Collaboration is necessary.

Communication

Formal or informal, written or verbal.

Leadership Roles

Positive, clear communication.

Problem Solving

Adaptive thinking is valuable.

Critical Thinking

Objectively analyzes problems.

Process Problem-solving

Brainstorming solutions.

Planning

Develop procedures to complete tasks efficiently.

Research

Seeking information from references.

Red Car Trap

Avoid limiting solutions by subconscious suggestions.

Reading and Understanding Text

Understand safety precautions, codes, and standards.

Punctuality

Necessary to demonstrate job interest and willingness to work.

Missing Work

It is important to show up at work every day.

Continued Education

Stay up to date with the latest technologies.

AWS SENSE Welder Certification

AWS has two certification levels.

• Entry-Level and Level II.
  Students must pass a closed book test regarding Module 2 (Safety and Health of Welders) with a minimum grade of 90%.
• A closed book test regarding material covered in Modules 1 and 3 must be passed with a minimum grade of 70%.
  Each of the four major welding processes are covered in Modules 4 through 7:
• Module 4, Shielded Metal Arc Welding (SMAW)
• Module 5, Gas Metal Arc Welding (GMAW, GMAW-S)
• Module 6, Flux Cored Arc Welding (FCAW, FCAW-G/GM)
• Module 7, Gas Tungsten Arc Welding (GTAW)
  $1/4 \text{ inch} = 6 \text{ mm}$
  $1/2 \text{ inch} = 13 \text{ mm}$
  $3/4 \text{ inch} = 18 \text{ mm}$
  $1 \text{ inch} = 25 \text{ mm}$
  $2 \text{ inches} = 50 \text{ mm}$
  $1/2 \text{ gal} = 2 \text{ L}$
  $1 \text{ gal} = 4 \text{ L}$
  $1 \text{ lb} = 1/2 \text{ K}$
  $2 \text{ lb} = 1 \text{ K}$
  $1 \text{ psig} = 7 \text{ kPa}$
  $1 \text{°F} = 1/2 \text{°C}$

Conversions

Conversions

Weight (Mass) Measurement

Conversions

Linear Measurement

Conversions

Pressure and Force Measurements

Conversions

Area measurement

Conversions

Volume measurement

| Unit | Measurement |
| :--------------------- |
| 1 cu in. |
| 1 cu ft. |
| 1 cu ft |
| 1 cu ft |
| 01