Common mistakes on AWS Welder practical exam
Ignoring Joint Preparation and Fit-Up Tolerances
A primary cause of AWS welder practical test failures is the failure to respect the geometric requirements of the joint before welding begins. In an AWS D1.1 qualification test, the Root Opening and Groove Angle are not merely suggestions; they are critical variables defined by the WPS. If a candidate fits a V-groove with a root opening that is 1/16th of an inch too wide, the risk of "blow-through" or excessive melt-through increases exponentially. Conversely, a root opening that is too tight prevents proper Root Penetration, leading to a lack of fusion at the base of the joint. Surface preparation is equally vital. Many candidates fail to remove mill scale or oxidation at least one inch back from the weld area. This oversight often results in Inclusions or a brittle heat-affected zone (HAZ). The inspector examines the fit-up before welding starts; a failure to meet the specified tolerances at this stage can result in immediate rejection of the test coupon before a single drop of filler metal is deposited.
Incorrect Machine Setup and Parameter Selection
Operating outside the allowable ranges for voltage, amperage, or wire feed speed is a common procedural error. Every WPS provides a range of electrical characteristics tailored to the material thickness and welding position. For example, in Shielded Metal Arc Welding (SMAW), setting the amperage too low for an E7018 electrode can lead to "cold starts" and a lack of fusion, while setting it too high causes excessive spatter and potential undercut. Candidates often forget to verify the Polarity (DCEP vs. DCEN), which fundamentally changes the heat distribution between the electrode and the base plate. In gas-shielded processes, failing to calibrate the flow meter can lead to atmospheric contamination. A flow rate that is too low provides insufficient shielding, while a rate that is too high can create turbulence, pulling oxygen into the weld pool and causing Subsurface Porosity that will only be revealed during a bend test or radiographic examination.
Critical Visual Inspection Errors That Lead to Failure
Misidentifying Acceptable vs. Defective Weld Profiles
Visual inspection is the first gate a candidate must pass, and visual inspection mistakes regarding weld profile are frequent. AWS D1.1 Clause 6 specifies strict limits for Reinforcement (the height of the weld above the base metal surface). For most structural tests, reinforcement must not exceed 1/8 inch. Excessive reinforcement creates a sharp "toe" angle, which acts as a stress riser and can lead to fatigue failure in real-world applications. Another common profile defect is Overlap, where the weld metal rolls over the base metal surface without fusing. This is often caused by low travel speeds or incorrect electrode angles. Candidates must also ensure the weld face is relatively smooth and transitions gradually into the base metal. A "ropey" bead with deep valleys between passes is often a precursor to slag entrapment, which will cause a failure during the destructive Bend Test phase of the examination.
Overlooking Surface Porosity and Cracks
Under AWS standards, any visible crack is an automatic disqualification. Cracks often occur in the Crate (the end of a weld bead) if the welder pulls the electrode away too quickly, leaving a localized shrinkage cavity. This is known as a crater crack. Furthermore, surface porosity—small gas pockets that breach the surface—is strictly regulated. Typically, the sum of the diameters of piping porosity must not exceed 3/8 inch in any linear inch of weld and shall not exceed 3/4 inch in any 12-inch length of weld. Candidates often ignore small pinholes, assuming they are insignificant, but these are often indicators of deeper internal issues. Welding disqualification errors frequently arise from a candidate's failure to use a magnifying glass or proper lighting to self-inspect their work before submission. If an inspector identifies a crack or porosity exceeding these limits, the test is terminated immediately, and the candidate is not permitted to proceed to the destructive testing phase.
Procedural Violations and WPS Non-Compliance
Deviating from Specified Welding Techniques
A common misconception among experienced welders is that "as long as the weld looks good, the technique doesn't matter." However, the AWS practical exam is a test of your ability to follow a specific Procedure Qualification Record (PQR). If the WPS specifies a "stringer bead" technique and the candidate uses a wide "weave" pattern, they are in violation of the procedure. Excessive weaving increases the Heat Input (calculated as (Amps x Volts x 60) / Travel Speed), which can degrade the mechanical properties of the steel, specifically its impact toughness. Furthermore, the WPS will dictate the allowable positions (e.g., 3G or 4G). Attempting to reposition the test coupon to make it easier to weld is a major violation. The test assembly must remain in the position in which it was leveled and marked by the inspector. Changing the orientation of the coupon after the start of the test is grounds for immediate disqualification.
Skipping Mandatory Preheating or Interpass Temperature Checks
Temperature control is critical for preventing Hydrogen-Induced Cracking (HIC). Many candidates, in an effort to finish quickly, ignore the Interpass Temperature requirements specified in the WPS. For high-strength steels, allowing the plate to get too hot can soften the material, while welding on a plate that is too cold can lead to rapid cooling rates and the formation of brittle martensite in the heat-affected zone. Use of Tempilstiks or digital pyrometers is essential to verify that the base metal is within the required temperature range before depositing the next pass. Neglecting to preheat the plates to the minimum specified temperature—often 50°F or higher depending on thickness and material grade—is a technical violation that can lead to structural failure of the weldment under stress. Inspectors often monitor these temperatures throughout the exam to ensure the candidate is following the thermal requirements of the code.
Technique Flaws That Cause Discontinuities
Travel Speed Issues Leading to Undercut or Overlap
Travel speed is the most difficult variable for many candidates to master under the pressure of an exam. Moving too fast results in a thin, weak bead and often causes Undercut, which is a groove melted into the base metal adjacent to the toe of the weld that is left unfilled by weld metal. AWS D1.1 allows for undercut no greater than 1/32 inch in most structural applications. Conversely, moving too slowly causes the weld pool to get ahead of the arc, leading to Overlap (cold lap) where the molten metal sits on top of the plate without fusing. This creates a sharp notch that is a primary failure point during the root and face bend tests. Maintaining a consistent travel speed is essential for achieving a uniform Weld Leg length and throat thickness, ensuring the weld can handle the design loads intended by the engineering specifications.
Poor Electrode Manipulation and Arc Control
In processes like SMAW or GTAW (Gas Tungsten Arc Welding), the angle of the electrode significantly influences the direction of the arc force and the resulting penetration. A common mistake is using an incorrect Work Angle or Travel Angle. For a horizontal fillet weld (2F), a 45-degree work angle is standard; deviating from this can cause the weld to favor one plate over the other, resulting in unequal leg lengths. Arc length is another critical factor. Holding an arc that is too long (long-arcing) increases the voltage and can lead to excessive spatter, loss of shielding gas effectiveness, and erratic metal transfer. This often results in "stray arcs" outside the weld zone. Under AWS rules, stray arcs are considered a defect because they create localized brittle spots on the base metal which can initiate cracks. Proper arc control requires a steady hand and a constant adjustment as the electrode is consumed.
Pre-Test and Post-Weld Handling Mistakes
Inadequate Material Cleaning and Contamination Control
Practical welding test preparation must involve meticulous cleaning of the test coupons. Beyond just removing mill scale, candidates must ensure there is no oil, grease, or moisture on the plates. Even a fingerprint can introduce enough hydrocarbons to cause porosity in certain processes like GTAW. Between passes, the removal of slag is mandatory. Failing to thoroughly clean the "toes" of a previous bead with a wire brush or chipping hammer often leads to Slag Inclusions. These are non-metallic solids trapped in the weld metal. During a bend test, these inclusions act as voids, causing the specimen to "open up" or fracture. If a slag inclusion exceeds 1/8 inch in any direction on the bent specimen, the candidate fails. Interpass cleaning is not just a housekeeping task; it is a fundamental requirement for ensuring the integrity of multi-pass welds.
Improper Test Coupon Identification and Submission
Even a perfect weld can result in failure if the administrative requirements are not met. Each test coupon must be marked with the candidate's identification and the orientation of the weld (e.g., "Top" or "Vertical Up"). A common error is the failure to preserve these markings throughout the welding and cutting process. Furthermore, when the test is complete, the candidate must not perform any unauthorized post-weld treatments. This includes grinding the face of the weld unless specifically allowed by the WPS. AWS D1.1 is very specific: "The face or root of the welds shall not be finished by any means... unless otherwise approved." Grinding away a defect like undercut rather than repairing it according to code procedures is a violation of the test integrity. Once the coupon is submitted for Destructive Testing, it must represent the welder's raw ability to meet the code requirements through welding technique alone.
Developing a Mistake-Proof Practice Routine
Simulating Full Exam Conditions
Many candidates practice in a comfortable environment that does not reflect the reality of the testing center. To avoid AWS welder practical test failures, practice sessions should strictly adhere to the time limits and physical constraints of the actual exam. This includes welding in a restricted booth, using the same protective equipment required during the test, and following a specific WPS from start to finish. Candidates should practice "stops and starts" in the middle of a joint, as the inspector will often require a stop-start in the root pass to evaluate the candidate's ability to tie in the weld. Simulating these conditions helps build the "muscle memory" needed to maintain composure when the pressure of the actual certification begins. It also allows the candidate to identify which positions or segments of the test cause the most fatigue, enabling them to adjust their technique accordingly.
Conducting Peer and Self-Inspections
Before sitting for the actual exam, a candidate should be proficient in the use of welding gauges, such as the V-WAC Gauge or the Fillet Weld Gauge. Self-inspection is the most effective way to identify and correct Common mistakes on AWS Welder practical exam before they become habitual. Candidates should evaluate their own practice coupons against the AWS D1.1 visual acceptance criteria. This includes measuring undercut depth, reinforcement height, and checking for any signs of overlap. Engaging in peer reviews—where another experienced welder critiques the work—can provide a fresh perspective on technique flaws that the candidate might be overlooking. Understanding the perspective of the Certified Welding Inspector (CWI) is crucial; by learning to see the weld through the eyes of the inspector, the candidate can proactively address discontinuities and ensure that their final submission exceeds the minimum standards for certification.