Unit 06: MIG/TIG Welding¶

Microcredential ID¶

MCC-U6-WeldGMAW-GTAW-v1.0

Title¶

Gas Metal Arc Welding (GMAW/MIG) & Gas Tungsten Arc Welding (GTAW/TIG) Operations

Version¶

1.0

Description¶

This unit provides comprehensive instruction on two major arc welding processes: MIG (Metal Inert Gas / Gas Metal Arc Welding) and TIG (Tungsten Inert Gas / Gas Tungsten Arc Welding). Students will understand the physics of welding arcs, shielding gas functions, heat affected zone metallurgy, weld joint design, and filler metal selection. Through hands-on practice, students will develop proficiency in MIG gun technique, wire feeding, transfer modes, and TIG arc control, foot pedal coordination, and tungsten selection. The unit emphasizes weld quality assessment, defect recognition, and safety protocols specific to welding.

This unit integrates OSHA 1910.97 (arc radiation), ANSI Z49.1 (safety in welding), AWS A3.0 (welding terminology and qualification), and OEM equipment documentation.

Alignment to Standards¶

OSHA 1910.97: Nonionizing Radiation Protection
OSHA 1910.1200: Hazard Communication Standard (fume exposure and SDS requirements)
ANSI Z49.1-2012: Safety in Welding, Cutting, and Allied Processes
AWS A3.0M-2020: Standard Welding Terms and Definitions
AWS A2.4M-2012: Standard Symbols for Welding, Brazing, and Nondestructive Examination
AWS C1.1M-2012: Specification for Welding Procedure and Performance Qualifications
ANSI/AWS D1.1-2020: Structural Welding Code—Steel
AWS D17.1M-2015: Specification for Fusion Welding for Aerospace Applications

Learning Outcomes¶

Knowledge¶

Understand arc physics in GMAW and GTAW systems
Explain shielding gas selection and its role in arc stability and weld quality
Describe heat affected zone (HAZ) and its metallurgical effects
Identify common weld joint types and their design criteria
Explain filler metal classification (AWS A5.18 for MIG; AWS A5.10 for TIG)
Recognize weld defects and their causes

Skill¶

Set up and operate MIG welding equipment
Perform wire feed calibration and maintenance
Apply proper MIG gun technique (push/pull angle, standoff distance)
Recognize transfer modes (spray, short-circuit, globular) and adapt parameters
Set up and operate TIG welding equipment
Select and prepare tungsten electrodes
Coordinate foot pedal control with torch hand manipulation
Apply proper TIG filler rod technique
Perform visual inspection and basic weld quality assessment

Competency¶

Independently weld simple joints (butt, lap, fillet) in flat and horizontal positions
Troubleshoot welding defects and adjust parameters accordingly
Select appropriate process (MIG or TIG) for given application
Demonstrate proficiency in both processes with acceptable bead geometry and penetration
Apply arc flash and fume safety protocols throughout operations
Recognize and prevent common weld defects

Unit Structure¶

Module 1: Welding Science Fundamentals¶

Arc physics, shielding gas function, heat affected zone, weld joint types, filler metals.

Module 2: MIG/GMAW Operation¶

Wire feed setup, voltage/amperage selection, gun technique, transfer modes, bead types, common defects.

Module 3: TIG/GTAW Operation¶

Tungsten selection and preparation, foot pedal control, filler rod technique, gas lens, pulse settings.

Module 4: Weld Quality & Safety¶

Visual inspection criteria, weld defects, arc flash PPE, fume extraction, hot work safety, fire watch.

Assessment Strategy¶

Module Assessments: 10-question formative quizzes covering process knowledge
Practical Welding Demonstrations: Supervised practice of fundamental techniques
Bead Evaluation: Instructor assessment of weld bead geometry, uniformity, and freedom from defects
Defect Recognition: Scenario-based identification of common weld defects and root causes
Safety Competency: Demonstrated correct PPE selection and use; emergency scenario response
Unit Practical Test: Weld a simple joint (student choice of process) and submit for evaluation

Instructional Resources¶

Primary References¶

AWS A3.0M: Standard Welding Terms and Definitions
AWS C1.1M: Specification for Welding Procedure and Performance Qualifications
ANSI Z49.1: Safety in Welding, Cutting, and Allied Processes
OEM equipment manuals (Lincoln Electric, Miller, ESAB, Hobart)
Miller Electric Welding Training Series (online videos)
AWS D1.1: Structural Welding Code—Steel

Tools & Equipment¶

GMAW (MIG) welding system with wire feeder and power supply
GTAW (TIG) welding system with torch, foot pedal, and power supply
Shielding gas regulators and cylinders (Argon for TIG and stainless; Ar/CO₂ for MIG steel)
Welding wire (ER70S-2, ER308L, ER5356 for aluminum)
Tungsten electrodes (pure, 2% thoriated, 2% lanthanated for TIG)
Welding consumables (cups, collets, contact tips, gas diffusers)
Test coupons (mild steel, stainless steel, aluminum)
PPE: arc-rated jacket/apron, TIG gloves, welding helmet with auto-darkening lens, hearing protection
Measurement and inspection tools (filler gauge, depth gauge, surface finish gage, visual inspection standard)
Metallurgical samples (cross-section of good and defective welds, if available)

Digital Resources¶

AWS A3.0 online access or PDF
OEM training videos (setup, basic technique, troubleshooting)
Weld defect photo library (porosity, lack of fusion, undercut, spatter examples)
Interactive weld parameter calculator (if available)

Accessibility Considerations¶

Visual Impairment: Audio descriptions of weld bead characteristics; tactile models of joint types; verbal feedback on technique
Hearing Impairment: Visual signals for equipment status; captioned videos; printed instruction guides; vibration feedback from equipment
Motor Coordination: Modified electrode holders (larger diameter for easier grip); extended foot pedal reach; alternative torch positioning techniques
Neurodiversity: Structured checklists for setup and technique; advance notice of loud noise levels; sensory breaks; written reference cards for parameter selection
Language: Bilingual equipment labels; glossary of welding terminology; peer instruction opportunities; visual weld parameter charts

Instructional Approach¶

This unit combines theoretical understanding (arc physics, metallurgy) with intensive hands-on skill development. Each module includes: - Concept slides with deep technical content - Demonstration of proper technique by the instructor - Guided practice with immediate corrective feedback - Peer observation and critique - Scenario-based troubleshooting

The unit assumes some metalworking experience but no prior welding knowledge.

Estimated Duration¶

Contact Hours: 24 hours (4 modules × 6 hours)
Hands-on Practice: 16 hours (supervised welds, technique refinement, defect assessment)
Self-Study: 4 hours (readings, online assessments, procedure creation)
Total: 44 hours

Unit Created: 2025-02-15 Last Updated: 2026-03-18 Curriculum Version: MCC Prototype Design Lab v1.0