FREE CWI Study Guide 2026

This free CWI study guide teaches the fundamentals the AWS Certified Welding Inspector exam tests, organized to the official AWS Body of Knowledge.^[1]

It’s interactive, not a wall of text: every module has built-in checkpoint quizzes, flashcards, and practice questions, so you learn by doing — not just reading.

The CWI credential is three separate exam parts — Part A (Fundamentals), Part B (Practical), and Part C (Code Book) — and you must pass all three at 72%. This guide focuses on Part A, the 150-question closed-book exam, then orients you to Parts B and C. Read a module, test yourself at each checkpoint, then drill gaps with our free practice test and flashcards.

CWI Exam Snapshot

The CWI is not one test — it is three parts, each scored separately and each requiring 72% to pass.^[1] Part A is the closed-book fundamentals this guide teaches:

This guide teaches Part A, organized into six topic modules that map the official Body of Knowledge — with a seventh module orienting you to the Part B and Part C exams. Study by the topics that carry the most Part A questions:^[2]

Module 1 · Welding Processes & Cutting

About 17% of Part A. An inspector must recognize the major welding and cutting processes, how each is shielded, and the discontinuities each tends to produce. The fastest way to tell the arc-welding processes apart is by how the weld pool is protected from the air.

1.1 The Five Arc-Welding Processes

The big five arc processes are SMAW (stick), GMAW (MIG), FCAW (flux-cored), GTAW (TIG), and SAW (submerged arc). SMAW and FCAW shield with flux that forms Slag; GMAW and GTAW shield with an external Shielding gas; SAW hides the arc under a granular flux blanket.^[3]

GTAW gives the cleanest, most precise welds (thin material, root passes, stainless and aluminum); SAW gives the highest deposition on thick sections. With GMAW and FCAW the electrode is consumed and becomes the Filler metal; with GTAW the tungsten is not consumed and filler is added separately.

1.2 Other Processes & Consumables

Beyond the big five, know resistance spot welding (heat from electrical resistance, no filler), oxyacetylene welding (a fuel-gas flame), and stud welding. Electrode and filler classification matters: an SMAW electrode like E7018 encodes tensile strength (70 ksi), position, and coating, while the “LH” (low-hydrogen) class must be kept dry to prevent Cold cracking.

1.3 Thermal Cutting

Oxy-fuel cutting (OFC) preheats steel then burns it in a stream of oxygen — it works only on carbon and low-alloy steel because it relies on oxidation. Plasma arc cutting (PAC) uses an ionized gas jet and cuts any electrically conductive metal, including stainless steel and aluminum. Carbon-arc gouging removes metal with an arc and compressed air.

Module 2 · Metallurgy & Heat Control

About 15% of Part A. Welding is localized melting, so the inspector must understand what heat does to steel — the Heat-affected zone, cracking, and how preheat controls both — plus the everyday calculations of fabrication math.

2.1 Steel, the HAZ & Cracking

Welding heat creates a Heat-affected zone (HAZ): base metal that was not melted but whose grain structure and hardness changed. Because the HAZ can become hard and brittle, it is a common site for cracking. Hot cracking happens during solidification (often along the centerline); Cold cracking is hydrogen-induced and appears after cooling.

Cold cracking needs three things together: hydrogen, a hard microstructure, and stress. Remove any one and the risk drops — which is exactly what preheat and low-hydrogen electrodes do. The Carbon equivalent (CE) estimates how hardenable (and crack-prone) a steel is.

2.2 Preheat, Interpass & PWHT

Preheat slows the cooling rate so the weld and HAZ stay softer and hydrogen can escape — the primary defense against cold cracking. Interpass temperature control keeps those benefits between passes. PWHT (post-weld heat treatment) is controlled heating after welding to relieve residual stress or improve toughness.

2.3 Welding-Related Calculations

Part A includes fabrication math: areas and volumes, weld metal weight, deposition and travel-speed relationships, and unit conversions. A core relationship is heat input, which rises with voltage and amperage and falls with travel speed (heat input is proportional to voltage times amperage divided by travel speed). Higher heat input means a slower cooling rate.

Module 3 · Weld Symbols (AWS A2.4)

About 12% of Part A. Weld symbols are the language of fabrication drawings, governed by AWS A2.4. The inspector reads them to know exactly what weld is required, where, and how big.^[4]

3.1 Anatomy of a Welding Symbol

Every Welding symbol is built on a Reference line with an arrow pointing to the joint and a tail for extra references. The single most-tested rule: a weld symbol placed below the reference line means the Arrow side; a symbol above the line means the Other side.

3.2 Joints, Welds & Supplementary Symbols

Don’t confuse the joint (the geometry of how parts meet) with the weld (how they’re joined). The five basic joints are butt, lap, tee, corner, and edge. A Fillet weld joins surfaces at a right angle; a Groove weld fills a prepared groove (square, V, bevel, U, or J).

Supplementary symbols add instructions: a flag on the bend = a field weld; a circle at the bend = weld all around; contour and finish symbols specify the weld face shape.

Module 4 · Discontinuities & NDE

About 26% of Part A — the largest topic area. This is the heart of inspection: recognizing weld discontinuities, deciding when one becomes a Defect, and choosing the right examination method to find it.

4.1 Discontinuity vs. Defect

A Discontinuity is any interruption in the typical structure of a weld. A Defect is a discontinuity that exceeds the applicable acceptance criteria of the governing code. Every defect is a discontinuity, but not every discontinuity is a defect — the Acceptance criteria decide which is which.^[3]

4.2 Common Weld Discontinuities

Know each discontinuity, its cause, and how it’s found. Porosity is trapped gas; Slag inclusions are trapped flux; Undercut and Overlap are toe-region flaws; Incomplete fusion and Incomplete joint penetration are bonding/root flaws; and cracks are the most serious, sharp-tipped flaws.

4.3 Nondestructive Examination (NDE)

Nondestructive examination evaluates a weld without damaging it. The five methods split into surface (Visual inspection, Liquid penetrant testing, Magnetic particle testing) and volumetric (Radiographic testing, Ultrasonic testing). VT is always first and finds the most defects per dollar.

4.4 Destructive Testing

Destructive testing sacrifices the specimen to measure properties — used to qualify procedures and welders, not to inspect production parts. The key tests: tensile (strength), bend (soundness and ductility), Charpy V-notch impact (toughness), hardness, and macroetch (cross-section soundness).

Module 5 · Inspection, QA & Documentation

About 15% of Part A. The inspector enforces the code through documents — the WPS, the PQR, qualification records — and through a disciplined before/during/after workflow, while staying within the duties and ethics of the role.

5.1 WPS, PQR & Qualification

A Welding Procedure Specification (WPS) tells the welder how to make a code-compliant weld. It is supported by a Procedure Qualification Record (PQR), which records the test weld and its results. A Welder Performance Qualification (WPQ) shows the welder can deposit sound welds. Changing an Essential variable beyond limits requires requalification.

5.2 Duties of the Inspector

The CWI verifies that materials, procedures, welders, and finished welds conform to the code and contract documents, and maintains accurate, impartial records. Ethics matter: the inspector must be honest, objective, and free of conflicts of interest, reporting findings factually regardless of pressure. AWS B5.1 defines the inspector’s qualification.^[6]

Module 6 · Terminology & Definitions

About 15% of Part A. Part A is precise about vocabulary, governed by AWS A3.0. Many questions hinge on the exact meaning of a single term, so the definitions are worth memorizing cold.^[3]

6.1 Core Welding Terms (AWS A3.0)

Build a reflex for the foundational pairs: Base metal vs. Filler metal vs. Weld metal; Discontinuity vs. Defect; Fillet weld vs. Groove weld. Anatomy of a weld — face, root, toe, leg, throat, and Weld reinforcement — shows up throughout symbols and inspection.

6.2 Positions, Safety & Symbols Vocabulary

Welding positions are coded: 1 = flat, 2 = horizontal, 3 = vertical, 4 = overhead, with G for groove and F for fillet (so 3G = vertical groove). Safety vocabulary — arc-flash and UV eye protection (proper shade lens), fume ventilation, and fire/hot-work precautions — is tested as recognition, not deep detail.

Module 7 · Part B (Practical) & Part C (Code Book)

Part A is only one of three exams. This module orients you to the other two — both required at 72% to earn the CWI.^[1]

7.1 Part B — Practical Inspection

Part B is a 46-question, hands-on exam. You inspect molded plastic weld replicas with real measuring tools (fillet gauges, calipers, the high-low gauge) and judge acceptability against the AWS Book of Specifications (BOS) — a fictitious spec AWS provides so the test is about inspection skill, not memorizing a code.^[5]

7.2 Part C — Code Book Application

Part C is a 50–65-question, open-book exam that tests whether you can quickly find and apply requirements in a code you choose at registration — most often AWS D1.1 (structural steel) or API 1104 (pipeline).^[7] Speed of navigation matters more than memorization; tabbing and knowing your code’s layout is the winning strategy.

How to Use This CWI Study Guide

This guide is built to be worked, not just read. The most efficient path to a pass:

• Master Part A first. It is the broad, closed-book fundamentals exam — and the foundation for Parts B and C. Lead with Discontinuities & NDE (the largest topic), then processes, metallurgy, inspection, terminology, and symbols.
• Check off as you go. Use the Study Guide Contents to mark each section done; it raises your exam-readiness score.
• Take every checkpoint. The end-of-module quizzes show you exactly which topics need another pass.
• Drill the weak topic. Send your weak area into the flashcards and a practice test until the score climbs.
• Train Parts B and C separately. Part B needs hands-on practice with gauges and replicas; Part C needs speed navigating your chosen code book.

CWI Glossary

The high-yield welding-inspection terms in one place — hover any dotted term in the guide, or flip the whole deck here as a self-grading flashcard set.

Acceptance criteria

The limits in a code or specification that determine whether a discontinuity is acceptable or is a rejectable defect.

Arrow side

The side of the joint the symbol's arrow points to; weld symbols for it sit below the reference line.

Base metal

The metal being welded or cut (the parent material), as opposed to the filler metal added by the weld.

Book of Specifications

BOS — the fictitious specification AWS supplies for CWI Part B, providing the acceptance criteria applied during the hands-on exam.

Carbon equivalent

A calculated value (from carbon and alloying elements) used to estimate a steel's weldability and cracking risk.

Certified Welding Inspector

AWS CWI — an individual certified by the American Welding Society as qualified to inspect welds, having passed Part A (Fundamentals), Part B (Practical), and Part C (Code Book).

Cold cracking

Hydrogen-induced cracking that occurs after the weld cools, favored by hydrogen, hard microstructure, and stress.

Crack

A fracture-type discontinuity with a sharp tip; classified as hot or cold, and longitudinal or transverse.

Defect

A discontinuity that exceeds the applicable acceptance criteria of the governing code, making it rejectable.

Destructive testing

Tests that destroy the specimen to measure properties — tensile, bend, impact (Charpy), hardness, and macroetch tests.

Discontinuity

An interruption in the typical structure of a weld — a lack of homogeneity in the material. A discontinuity is not automatically a defect.

Essential variable

A welding variable whose change beyond set limits requires requalification of the procedure or welder.

FCAW

Flux-Cored Arc Welding — a continuous tubular wire with flux inside, used self-shielded or with additional gas.

Filler metal

The metal added during welding, supplied by an electrode or filler rod, that becomes part of the weld.

Fillet weld

A weld of roughly triangular cross-section that joins two surfaces at approximately a right angle (tee, lap, or corner joints).

GMAW

Gas Metal Arc Welding (MIG) — a continuous consumable wire electrode shielded by an externally supplied gas.

Groove weld

A weld made in a groove between two members; groove types include square, V, bevel, U, and J.

GTAW

Gas Tungsten Arc Welding (TIG) — a non-consumable tungsten electrode with inert gas shielding and a separately added filler.

Heat-affected zone

HAZ — the region of base metal next to the weld whose microstructure and properties were changed by welding heat without melting.

Hot cracking

Cracking that occurs at high temperature during solidification, often along the weld centerline.

Incomplete fusion

A weld discontinuity in which weld metal did not fuse with the base metal or with a preceding bead.

Incomplete joint penetration

Joint root that is not completely filled — the weld metal does not extend through the full required depth.

Interpass temperature

The temperature of the metal between weld passes, controlled to keep the benefits of preheat.

Lack of fusion

A common term for incomplete fusion between weld passes or with the base metal.

Liquid penetrant testing

PT — an NDE method that uses a dye drawn into surface-breaking flaws and a developer to reveal them.

Magnetic particle testing

MT — an NDE method for ferromagnetic materials that reveals surface and near-surface flaws using a magnetic field and iron particles.

Nondestructive examination

NDE (or NDT) — methods that evaluate a weld without damaging it: VT, PT, MT, RT, and UT.

Other side

The side of the joint away from the arrow; weld symbols for it sit above the reference line.

Overlap

Weld metal that has flowed over the base metal surface without fusing to it, at the toe or root of a weld.

Oxy-fuel cutting

OFC — a thermal cutting process that burns metal in a stream of oxygen; works on carbon and low-alloy steel.

Plasma arc cutting

PAC — thermal cutting using a high-temperature ionized gas jet; cuts any electrically conductive metal.

Porosity

Cavity-type discontinuities formed by gas trapped in the solidifying weld metal.

Preheat

Heat applied to the base metal before welding to slow cooling and reduce cracking risk.

Procedure Qualification Record

PQR — the document recording a test weld and its results that qualifies (supports) a WPS.

PWHT

Post-Weld Heat Treatment — controlled heating after welding to relieve residual stress or improve properties.

Radiographic testing

RT — an NDE method using X-rays or gamma rays to image internal (volumetric) flaws such as porosity and slag.

Reference line

The horizontal backbone of a welding symbol; symbols below it mean the arrow side, above it mean the other side.

SAW

Submerged Arc Welding — a continuous wire under a granular flux blanket; the arc is not visible.

Shielding gas

A gas (such as argon or carbon dioxide) supplied to protect the molten weld pool from atmospheric contamination.

Slag

The nonmetallic solid that forms over a weld from flux; it must be removed and, if trapped, becomes a slag inclusion.

SMAW

Shielded Metal Arc Welding (stick) — a consumable flux-coated electrode whose coating forms a shielding gas and slag.

Ultrasonic testing

UT — an NDE method using high-frequency sound to detect internal flaws, especially planar cracks and lack of fusion.

Undercut

A groove melted into the base metal next to the weld toe or root and left unfilled by weld metal.

Visual inspection

VT — examination of a weld with the eye (aided by gauges and lighting) to find surface discontinuities, profile, and size.

Weld joint

The junction of members to be joined; the five basic types are butt, lap, tee, corner, and edge.

Weld metal

The portion of a weld that has been melted during welding (a mix of melted base metal and filler metal).

Weld reinforcement

Weld metal in excess of the quantity required to fill the joint, on the face or root side.

Welder Performance Qualification

WPQ — a record showing a welder has demonstrated the skill to deposit sound welds within a range of conditions.

Welding Procedure Specification

WPS — a written document giving the welder the direction to make a code-compliant weld via its essential variables.

Welding symbol

The AWS A2.4 graphical instruction — reference line, arrow, and tail — specifying the weld required on a drawing.

CWI Study Guide FAQ

References

1. 1.American Welding Society. “Certified Welding Inspector (CWI) — Certification Program.” aws.org. ↑
2. 2.American Welding Society. “Examination User Guide for Certified Welding Inspector.” aws.org. ↑
3. 3.American Welding Society. “AWS A3.0 — Standard Welding Terms and Definitions.” pubs.aws.org. ↑
4. 4.American Welding Society. “AWS A2.4 — Standard Symbols for Welding, Brazing, and Nondestructive Examination.” pubs.aws.org. ↑
5. 5.American Welding Society. “CWI Part B (Practical) — In-Person Training.” aws.org. ↑
6. 6.American Welding Society. “AWS B5.1 — Specification for the Qualification of Welding Inspectors.” pubs.aws.org. ↑
7. 7.American Welding Society. “AWS D1.1 — Structural Welding Code, Steel.” pubs.aws.org. ↑

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