Part A: Fundamentals
Part A is the closed-book fundamentals exam and the largest portion of the CWI. It tests broad knowledge of welding processes, metallurgy, drawing interpretation, weld discontinuities, nondestructive examination, and safety. Mastering the vocabulary and core concepts here builds the foundation for the practical and code-application parts.
Common Arc Welding Processes
A welding inspector must recognize the major arc welding processes and how each is shielded. SMAW (stick) uses a flux-coated consumable electrode whose coating creates both a shielding gas and a protective slag. GMAW (MIG) and FCAW feed a continuous wire, with GMAW shielded by an external gas and self-shielded FCAW protected by flux inside the wire. GTAW (TIG) uses a non-consumable tungsten electrode with inert gas for precise, high-quality welds, while SAW buries the arc under a granular flux for high deposition on thick material. Knowing each process explains the discontinuities and defects an inspector should expect.
Basic Weld Metallurgy
Welding is a localized melting and solidification process, so understanding metallurgy helps predict weld behavior. The heat-affected zone (HAZ) is base metal that did not melt but whose microstructure changed from the heat, often becoming the most vulnerable region. Rapid cooling can harden steel and, combined with hydrogen, lead to cracking, which is why preheat and low-hydrogen practices matter. Inspectors should grasp how carbon content, cooling rate, and heat input influence hardness, toughness, and cracking tendency.
Weld Symbols and Joint Terminology
Drawings communicate weld requirements through standardized AWS welding symbols built around a reference line and an arrow. Symbols below the reference line describe the arrow side of the joint, while symbols above describe the other side, letting one symbol specify welds on both sides. Inspectors must also know joint and weld terminology such as root, face, toe, leg, throat, and reinforcement. Correctly reading these symbols and terms ensures the weld made matches what the engineer specified.
Discontinuities, Defects, and NDT Methods
A discontinuity is any interruption in the typical structure of a weld, and it becomes a defect only when it exceeds acceptance criteria. Common discontinuities include porosity, slag inclusions, incomplete fusion, incomplete penetration, undercut, overlap, and cracks. Inspectors select nondestructive examination methods accordingly: VT for surface conditions, PT for surface-breaking flaws, MT for surface and near-surface flaws in ferromagnetic metals, and RT or UT for internal volumetric flaws. Understanding what each method can and cannot detect prevents over-claiming inspection results, and safety practices such as eye protection from arc radiation and ventilation of fumes underpin all field work.