Visual Inspection Criteria AWS Welder: Code Foundations
AWS D1.1 Acceptance Standards for Visual Examination
The AWS D1.1 visual inspection guide serves as the regulatory backbone for most structural welding certifications. Under this code, specific acceptance criteria are established based on the service conditions of the weldment—statically loaded versus cyclically loaded structures. For the welder qualification test, the inspector looks for a weld that is free of cracks and exhibits thorough fusion between adjacent layers of weld metal and between weld metal and base metal. All craters must be filled to the full cross-section of the weld, except for those ends of intermittent fillet welds outside their effective length. The code specifically limits the size and frequency of piping porosity and sets rigid boundaries for undercut depth, typically not to exceed 1/32 inch (1 mm) for materials thicker than 1/8 inch. Understanding these thresholds is vital, as a single measurement exceeding these limits results in an immediate failure of the test coupon.
The Role of Visual Inspection in Welder Qualification
In the context of the AWS Certified Welder program, visual inspection acts as a high-fidelity filter. It assesses the welder’s ability to control the arc, manage heat input, and manipulate the puddle effectively. The AWS welder visual test standards are designed to ensure that the surface geometry of the weld does not create stress concentrators that could lead to premature structural failure. While bend tests evaluate internal ductility and fusion, visual inspection evaluates the execution of the welding procedure. An inspector examines the root pass for complete penetration and the cap for uniform width and height. This stage of the exam is non-negotiable; if a candidate cannot produce a weld that meets the surface requirements of the code, it is statistically unlikely that the internal metallurgy will meet the required mechanical properties.
Precision in measurement is impossible without the correct instrumentation. Candidates must be proficient with a V-WAC Gauge or a Bridge Cam Gauge to measure undercut depth and weld reinforcement height. To measure fillet welds, a standard Fillet Weld Gauge is used to determine the leg length and the actual throat thickness. For detecting fine surface cracks or tight overlap, a 10x magnifying glass is often employed. A Hi-Lo gauge is essential for checking the internal alignment of pipe or plate butt joints before and after welding. Using these tools correctly involves ensuring the gauge is perpendicular to the workpiece and that the pointer is zeroed. Misreading a gauge by even 1/64 of an inch can be the difference between a passing grade and a rejection for excessive reinforcement or insufficient throat.
Lighting and Surface Preparation Requirements
Visual inspection cannot be performed accurately in poor conditions. AWS standards often specify a minimum light intensity, typically measured in foot-candles or lux, at the inspection surface to ensure that fine discontinuities like hairline cracks or micro-porosity are visible. Before an inspector approaches the coupon, the welder must ensure the surface is clean. This involves the complete removal of all slag, as slag can mask weld discontinuities acceptance criteria violations like trapped gas or incomplete fusion at the toe. However, candidates must be careful not to over-clean; excessive grinding that reduces the base metal thickness or alters the weld profile can lead to rejection. The goal is a clean, as-welded surface that allows for an unobstructed view of the weld metal and the heat-affected zone (HAZ).
Identifying and Measuring Common Weld Discontinuities
Undercut: Causes, Measurement, and Allowable Limits
Undercut is a groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal. In the undercut porosity inspection exam portion, candidates are tested on their ability to recognize this defect, which is often caused by excessive current, too long an arc length, or an improper electrode angle. Measurement is performed using a depth gauge placed on the base metal with the probe extending into the bottom of the groove. For most AWS qualification tests, the maximum allowable depth for undercut is 1/32 inch. If the undercut is parallel to the primary stress, it is particularly dangerous as it creates a notch effect. Inspectors will look for "sharp" undercut, which is more detrimental than rounded transitions, as it significantly increases the stress concentration factor at the toe.
Porosity and Slag Inclusions: Types and Evaluation
Porosity represents gas pockets trapped in the solidifying weld metal. The AWS criteria distinguish between scattered porosity, cluster porosity, and piping porosity. For a qualification test, the sum of the diameters of visible piping porosity must not exceed 3/8 inch (10 mm) in any linear inch of weld, and the maximum diameter of a single pore is typically limited to 1/16 inch. Slag inclusions, often the result of improper cleaning between passes in SMAW or FCAW, are usually identified as non-metallic solids trapped in the weld. While slag is often internal, surface-breaking slag is a major defect. It indicates a lack of puddle control or failure to maintain a proper travel angle, leading to the "running over" of the slag by the molten metal.
Cracks are the most severe discontinuity and are categorized as "critical" defects. Under AWS D1.1 and D1.5, there is zero tolerance for cracks of any size or type. Whether they are longitudinal, transverse, crater cracks, or underbead cracks, their presence results in immediate rejection. Cracks indicate a fundamental failure in the welding procedure, such as inadequate preheat, high restraint, or improper filler metal selection. During the exam, inspectors pay close attention to the crater at the end of a weld bead, as this is a common location for "star" or "shrinkage" cracks. If a crack is suspected, the inspector may call for a Liquid Penetrant Test (PT) or Magnetic Particle Test (MT) to confirm the finding, though visual confirmation is usually sufficient for rejection.
Overlap, Incomplete Fusion, and Arc Strikes
Overlap occurs when the weld metal overflows the surface of the base metal without fusing to it. This creates a sharp notch and is always a cause for rejection because the effective weld size is reduced. It is often detected by trying to slide a thin feeler gauge or the edge of a scale under the toe of the weld. Incomplete fusion (IF) is the failure of the weld metal to fuse with the base metal or preceding beads, often appearing as a dark line at the boundary. Furthermore, stray arc strikes—marks left on the base metal from accidentally striking the electrode outside the joint—are strictly prohibited. These strikes can cause localized hardening and micro-cracking in the base metal, compromising the structural integrity of the entire component.
Evaluating Weld Size and Profile
Measuring Fillet Weld Leg Length and Theoretical Throat
For fillet welds, the two most important dimensions are the leg length and the theoretical throat. The leg length is the distance from the root of the joint to the toe of the fillet. In a qualification test, the leg size must meet the minimum specified in the Welding Procedure Specification (WPS). The theoretical throat is the shortest distance from the root to the hypotenuse of the largest right triangle that can be inscribed within the fillet weld cross-section. Inspectors use a fillet gauge to ensure the weld is not undersized. An undersized weld fails to carry the designed load, while an oversized weld is an unnecessary waste of filler metal and can lead to excessive distortion of the base material.
Assessing Groove Weld Reinforcement and Penetration
Groove welds are evaluated based on their "reinforcement," which is the weld metal in excess of the metal necessary for the specified weld size. For a standard AWS test plate, reinforcement should typically be between 0 and 1/8 inch (3 mm). Excessive reinforcement is undesirable because it creates a sharp transition at the toe, which acts as a stress riser. On the root side of a single-welded groove joint, complete penetration is required. The inspector will look for "root pull-back" or "incomplete penetration," where the weld metal fails to extend through the full thickness of the joint. The root bead must be fused to both sides of the joint and should generally be flush or slightly convex.
Acceptable Limits for Convexity and Concavity
The profile of a fillet weld can be either convex (bulging outward) or concave (curving inward). While a slightly convex profile is generally preferred for its strength, excessive convexity is a defect. AWS D1.1 provides a formula for maximum convexity based on the actual width of the weld face. For example, if the face width is less than 5/16 inch, the maximum convexity allowed is 1/16 inch. Conversely, excessive concavity is a problem if it reduces the actual throat of the weld below the required theoretical throat. A "dead flat" or slightly convex profile is the target for a passing test coupon, ensuring that the weld provides the necessary throat thickness without creating excessive stress points at the toes.
Dealing with Weld Misalignment and Mismatch
Misalignment, also known as "high-low," occurs when the surfaces of the two pieces being joined are not in the same plane. This is common in pipe welding and plate butt joints. AWS codes specify limits for mismatch because it causes eccentric loading, which can lead to premature failure under tension. During the setup phase of the exam, the welder must ensure that the parts are tacked within the tolerances specified in the WPS. If the misalignment exceeds 10% of the thickness of the thinner part (up to a maximum of 1/8 inch), the joint may be rejected before welding even begins. Proper use of a Hi-Lo gauge during fit-up is the best way to prevent this failure.
Surface Condition and Finishing Requirements
Acceptability of Spatter and Stray Arc Marks
While spatter is often considered a cosmetic issue, excessive spatter in an AWS exam can indicate poor arc stability or incorrect shielding gas flow. The code requires the removal of all spatter that would interfere with subsequent non-destructive testing or that could hide other defects. Stray arc marks are even more critical; as previously mentioned, they are grounds for rejection. If an arc strike occurs, the code often requires it to be ground smooth and inspected for cracks using magnetic particle testing. For the welder qualification test, the best practice is to avoid arc strikes entirely by using a striking pad or carefully striking the arc only within the confines of the weld groove.
Weld Start/Stop Crater Requirements
Every time a welder stops to change an electrode or at the end of a joint, a crater is formed. These "starts and stops" are the most vulnerable points in a weld. AWS criteria require that all craters be filled to the full cross-section of the weld. An unfilled crater creates a thin spot in the weld throat and often contains "crater cracks" due to the rapid cooling of the small molten pool. To pass the visual inspection, the welder must demonstrate the "back-step" technique or dwell at the end of the bead to ensure the crater is fully reinforced. Inspectors will specifically look at these transition points for any evidence of porosity or lack of fusion where the new bead ties into the previous one.
Cleaning and Removal of Slag Between Passes
In multi-pass welding, such as a 3G (vertical) or 4G (overhead) plate test, cleaning is paramount. Each pass must be thoroughly cleaned of all slag and oxides before the next pass is deposited. Failure to do so results in slag inclusions, which are easily identified during visual inspection if they break the surface, or later during a bend test if they are internal. The use of a chipping hammer and wire brush is required. However, the welder should avoid using a power grinder to "reshape" the bead between passes unless the WPS specifically allows it. The goal is to remove the slag while maintaining the integrity of the weld bead profile for the next layer.
Grinding and Weld Toe Blending Rules
While some codes allow for the blending of weld toes to improve fatigue life, the AWS welder qualification test generally evaluates the "as-welded" condition. If grinding is permitted, it must be done carefully to ensure that the base metal is not thinned below its nominal thickness. Any grinding marks should be parallel to the direction of the primary stress to avoid creating new stress risers. "Mechanical cleaning" is acceptable, but "mechanical shaping" to hide poor workmanship is usually discouraged and can be flagged by an experienced inspector. The transition from the weld face to the base metal should be smooth and gradual, ideally with an angle of 135 degrees or greater.
Applying Criteria to Different Welding Processes
SMAW (Stick) Weld Visual Characteristics and Pitfalls
Shielded Metal Arc Welding (SMAW) is prone to specific visual defects, most notably slag inclusions and undercut. Because the slag is thick and fluid, it can easily be trapped if the welder doesn't maintain a tight arc and proper electrode angle. In the vertical up (3G) position, SMAW often exhibits "shelfing" if the travel speed is too slow, leading to an uneven profile. To pass the how to visually inspect a weld for certification phase with SMAW, the inspector looks for a uniform ripple pattern and a clean tie-in at the toes. The presence of "stubbing"—where the electrode sticks to the work—often leaves unsightly marks that must be carefully cleaned and repaired.
GMAW (MIG) and FCAW Weld Appearance Expectations
Gas Metal Arc Welding (GMAW) and Flux Cored Arc Welding (FCAW) are characterized by higher deposition rates and different visual profiles. GMAW, especially in the short-circuit transfer mode, is susceptible to "cold lap" or lack of fusion, which can be difficult to see but often appears as a very rounded weld toe that doesn't seem to "wet" into the base metal. FCAW produces a slag similar to SMAW but usually much thinner and more easily removed. A common pitfall in FCAW is "wormhole" porosity, which appears as long, tunnel-like holes on the surface. This is usually caused by excessive moisture in the flux or a loss of shielding gas and is an automatic rejection.
Process-Specific Discontinuity Patterns
Different processes leave different visual "signatures." For example, GTAW (TIG) welds are expected to have a very fine, consistent ripple pattern and almost zero spatter. Any tungsten inclusions (which appear as small shiny spots) or oxidation (often called "sugar" on the backside of stainless steel) are critical failures. In contrast, GMAW-P (Pulsed MIG) should have a distinct, rhythmic ripple pattern. Understanding these process-specific expectations allows the welder to self-inspect during the test. If a GMAW weld shows a lot of fine spatter, the welder should immediately check the gas flow or voltage settings before continuing, as this indicates an unstable arc that will likely lead to surface defects.
Ensuring Consistent Evaluation Across Processes
Despite the differences in appearance, the AWS welder visual test standards remain the same for the purpose of qualification. A 1/16-inch pore is a 1/16-inch pore, regardless of whether it was produced by SMAW or GMAW. The inspector applies the same D1.1 Table 6.1 (or the equivalent in the specific code being used) to all coupons. This consistency ensures that a certified welder has a universal baseline of competence. The candidate must be able to switch between processes while maintaining the same level of attention to the fundamental acceptance criteria: fusion, profile, and the absence of cracks and excessive porosity.
Practical Test Inspection: A Step-by-Step Guide
Systematic Visual Examination Sequence
A professional inspector follows a logical sequence, and the candidate should do the same during self-inspection. Start with the "macro" view: check the overall alignment and for any obvious misses or arc strikes. Then, move to the weld profile: measure the reinforcement height and fillet leg sizes. Next, conduct a "micro" scan: look closely at the toes for undercut and overlap, and examine the face for porosity. Finally, inspect the root (if accessible) for penetration and fusion. This systematic approach ensures that no single defect is missed. During the exam, performing this check after every pass—not just the cap—allows for the correction of issues before they are buried and become permanent failures.
Documenting Measurements and Findings
In a formal AWS exam setting, the inspector will record findings on a Weld Inspection Report. This document lists the specific criteria from the code and notes whether the coupon "passed" or "failed" each one. As a candidate, you should be prepared to discuss your weld with the inspector using technical terminology. Instead of saying "it looks a bit deep," say "the undercut at the toe of the third pass measures 3/64 inch, which exceeds the D1.1 limit for this thickness." This level of precision demonstrates to the CWI (Certified Welding Inspector) that you are an informed professional who understands the standards of the trade.
Making Accept/Reject Determinations Under Pressure
The pressure of the testing environment can lead to rushed decisions. However, the visual inspection is the one phase where the welder has the most control. If you identify a defect like a crater crack or a small area of porosity while welding, many codes allow for its removal and repair during the test, provided it's done within the rules of the WPS. Once the coupon is handed over for final inspection, however, no further work is allowed. Being able to objectively evaluate your own work—knowing when a weld is "good enough" versus when it requires a repair—is a hallmark of a master welder.
Common Reasons for Failure in the Practical Visual Check
Statistically, the most common reasons for failure are undercut and excessive reinforcement. Many welders, fearing a lack of penetration, over-weld the joint, leading to reinforcement that exceeds the 1/8-inch limit. Others fail due to "cold starts," where the beginning of a weld bead hasn't fully fused to the base metal. Another frequent issue is the failure to fill the crater at the end of the plate. These are all "avoidable" errors that have nothing to do with the welder's ability to run a bead and everything to do with their attention to the visual inspection criteria AWS Welder requirements.
Exam Preparation: Sample Inspection Questions and Scenarios
Interpreting Images of Welds with Discontinuities
The written portion of the AWS exam often includes photographs of welds where you must identify the defect. You might see a photo of a fillet weld where the weld metal "rolls over" the toe; you must identify this as overlap. Or, you might see a series of small holes in a cluster, which you should correctly label as cluster porosity. Practice by looking at the "Welding Inspection Handbook" published by AWS, which contains high-resolution images of both acceptable and unacceptable welds. Being able to name the defect is the first step in understanding how to prevent it in the booth.
Calculating if a Weld Meets Size Requirements
You may be presented with a scenario: "A WPS calls for a 1/4-inch fillet weld. You measure the legs at 5/16 inch and 3/16 inch. Does this weld pass?" In this case, the weld fails because one leg is smaller than the required 1/4 inch, even though the other leg is larger. The size of a fillet weld is determined by the length of the shortest leg. You must also be able to calculate the required throat: for a 1/4-inch fillet, the theoretical throat is 1/4 x 0.707, or approximately 0.177 inches. If your measured throat is less than this, the weld is rejected. These calculations are a staple of the AWS examination process.
Exam questions often test your knowledge of metrology. If the task is to measure the internal misalignment of a pipe, the correct tool is a Hi-Lo Gauge, not a standard ruler. If you need to measure the angle of a bevel, a protractor or a Bridge Cam Gauge is appropriate. Understanding the limitations of each tool—for instance, knowing that a V-WAC gauge is better for undercut but a Fillet Gauge is better for leg size—is essential. You should be familiar with both US Customary and Metric scales, as the AWS exam may use either or both.
Prioritizing Inspection Steps for Efficiency
In a timed exam or a busy shop, you must prioritize. The first step is always to check for cracks, as their presence makes all other measurements moot. Next, check for fusion and penetration. Only after the structural integrity is confirmed should you spend time measuring the finer details of reinforcement height or spatter. This hierarchy of inspection—cracks first, fusion second, dimensions third—reflects the real-world priorities of a CWI and ensures that you are focusing your efforts on the most critical aspects of the AWS welder visual test standards.