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newSchoolWorks.com › VoTechWorks › Building & Construction › Welding › Gas Tungsten Arc Welding (GTAW) › Lesson 9
BLD-WELD01-06 · Lesson 9 · 10 clock hours · practice

Certification Coupon Welding: Plate and Pipe Entry-Level Practice

Objective. Students will complete a full AWS Certified Welder-format GTAW test coupon in the 2G or 3G position, applying all learned technique, fit-up, and documentation practices under simulated test conditions.

What This Lesson Is About

This lesson places you in a simulated AWS Certified Welder test environment. You will fit up a pre-beveled carbon steel groove coupon, tack weld it to a written Welding Procedure Specification (WPS), weld the complete joint in the 2G (horizontal) or 3G (vertical) position using GTAW, fill out a weld test record, and have the finished coupon evaluated against AWS D1.1 visual acceptance criteria. Every step mirrors what happens on an actual certification test day.

Why Simulation Matters

The AWS Certified Welder credential is performance-based. A qualified examiner watches you work, reviews your documentation, and sends your coupon through visual and destructive examination. Practicing under test-like conditions — timed, quiet, no coaching — trains you to perform reliably when it counts. It also reveals technique habits you may not notice when an instructor is guiding you in real time.

Fit-Up and Tack Welding

A good coupon starts with correct fit-up. Your pre-beveled coupons have been prepared to the joint geometry specified in the WPS. Your job before welding begins:

1. Check bevel angle and root face. Use a weld gauge to confirm the bevel angle and root face width match the WPS. A root face that is too wide traps the root pass and causes incomplete fusion; too narrow and you burn through.

2. Set root opening. Measure the root opening at both ends and the center using your weld gauge. Set it to the dimension stated in the WPS — typically in the range of 1/8 in. (3.2 mm) for many D1.1 groove joints, but always follow the specific WPS value.

3. Tack weld. Place tacks at each end and, for longer coupons, in the center. Tacks must be strong enough to hold alignment but small enough that the root pass can fully fuse through or consume them. AWS D1.1 requires that tacks become part of the finished weld or be completely removed — partial fusion on a tack left in place is a defect.

4. Instructor sign-off. Have your fit-up inspected and approved before you strike an arc. On a real test, the examiner checks fit-up. Skipping this step in practice builds a bad habit.

Welding the Coupon

Once fit-up is approved, set your machine parameters to the WPS range — verify polarity (DCEN for most GTAW), amperage, and shielding gas flow rate (argon, typically in the range of 15–25 CFH; your WPS specifies the value). Record the actual amperage and gas flow on your weld test record before you start.

Root pass: Use a filler diameter suited to the tight root opening. Move steadily and watch the keyhole — a consistent keyhole indicates full penetration. Avoid stopping in the middle of the joint; if you must stop, feather the restart area with a grinder and overlap the restart by at least 1/2 in.

Fill and cap passes: Clean each pass with a stainless steel wire brush (never carbon steel — it contaminates the weld). Maintain interpass temperature within WPS limits. Blend toes smoothly to avoid undercut. The cap must be flush to 1/8 in. (3.2 mm) above the base metal surface — excessive reinforcement is a D1.1 visual rejection criterion.

2G vs. 3G considerations: In 2G, gravity pulls the puddle downward; angle the torch and filler slightly upward to compensate. In 3G vertical-up, use a controlled weave or stringer progression and allow each pass to cool enough to support the next without sagging.

Post-Weld Visual Inspection

After the coupon cools, inspect it against AWS D1.1 visual acceptance criteria before submitting:

Use a weld gauge for undercut depth and reinforcement height. Your eyes alone are not precise enough.

Weld Test Record

Documentation is part of the credential, not an afterthought. The weld test record must capture every critical variable: WPS number, base metal specification and thickness, filler metal classification and heat/lot number, position, amperage and voltage used, shielding gas and flow rate, and your name and date. Missing entries invalidate the record on a real test. Complete it accurately — your instructor will review it entry by entry.

Safety for This Lesson

PPE: Auto-darkening helmet set to the appropriate shade for GTAW amperage, leather gloves, flame-resistant jacket, leather boots, and hearing protection if grinding is performed.

Shielding gas: Argon displaces oxygen in confined or low spaces. Ensure ventilation is adequate. Inspect hose connections for leaks before opening the cylinder valve. Always stand to the side when cracking a cylinder valve.

Grinding: Angle grinders require a face shield over safety glasses, not a face shield alone. Secure the coupon in a vise or clamp — never hand-hold it while grinding.

Lockout/Tagout: If a machine malfunction requires opening the GTAW inverter case, lock out the power source before any inspection. Do not attempt electrical repairs; report faults to your instructor.

Hot metal: Coupons retain heat long after welding stops. Use pliers or tongs; mark hot metal with soapstone or chalk and allow cooling before handling bare-handed.

Key terms10

Root openingThe gap between the two base metal pieces at the root of the joint before welding; set to the dimension specified in the WPS to allow full penetration on the root pass.
Welding Procedure Specification (WPS)A written document that prescribes all essential variables for a weld — base metal, filler, position, amperage, voltage, preheat, and more — that welders must follow during qualification testing and production welding.
Critical variableAny parameter on a weld test record whose change would require re-qualification; examples include welding process, position, and base metal group.
UndercutA groove melted into the base metal at the toe of the weld that is not filled by weld metal; AWS D1.1 limits undercut depth to protect the structural integrity of the joint.
Weld reinforcementWeld metal deposited above the plane of the base metal surface on a groove weld; AWS D1.1 sets a maximum height to prevent stress concentration.
KeyholeA small, elongated opening at the leading edge of the GTAW root pass puddle that indicates the arc is fully penetrating through the root of the joint.
2G positionA groove weld made on a plate or pipe held so the weld axis is horizontal and the weld face is vertical; the welder works in the horizontal position.
3G positionA groove weld on a plate held vertical; the welder progresses upward (vertical-up) or downward (vertical-down) along the joint axis.
Interpass temperatureThe temperature of the weld joint measured between passes; the WPS specifies a maximum to prevent excessive heat input that can degrade mechanical properties.
Destructive testingExamination methods — such as bend testing or nick-break testing — that physically break the coupon to evaluate internal soundness and fusion; required for AWS Certified Welder qualification.

Worked examples4

1. Your WPS specifies a root opening of 1/8 in. You measure the gap at the left end as 0.130 in. and at the right end as 0.118 in. Are both ends within tolerance if the WPS allows ± 1/16 in. (0.0625 in.)?
  1. Convert 1/8 in. to decimal: 1 ÷ 8 = 0.125 in. (target value).
  2. Calculate the allowable range: 0.125 − 0.0625 = 0.0625 in. (minimum); 0.125 + 0.0625 = 0.1875 in. (maximum).
  3. Check the left end: 0.130 in. Is 0.0625 ≤ 0.130 ≤ 0.1875? Yes — within tolerance.
  4. Check the right end: 0.118 in. Is 0.0625 ≤ 0.118 ≤ 0.1875? Yes — within tolerance.
  5. Both ends are acceptable; proceed to instructor fit-up approval.
Answer: Both measurements (0.130 in. and 0.118 in.) fall within the allowable range of 0.0625 in. to 0.1875 in., so fit-up is acceptable.
2. After welding, you measure the cap reinforcement at three spots: 3/32 in., 1/8 in., and 5/32 in. AWS D1.1 allows a maximum reinforcement of 1/8 in. (0.125 in.). Which readings pass and which require correction?
  1. Convert all fractions to decimal inches: 3/32 = 0.09375 in.; 1/8 = 0.125 in.; 5/32 = 0.15625 in.
  2. Compare each to the maximum of 0.125 in.
  3. 3/32 in. (0.09375 in.): 0.09375 ≤ 0.125 — PASS.
  4. 1/8 in. (0.125 in.): 0.125 ≤ 0.125 — PASS (exactly at the limit).
  5. 5/32 in. (0.15625 in.): 0.15625 > 0.125 — FAIL; this area exceeds the maximum and must be ground flush and re-evaluated.
Answer: The 3/32 in. and 1/8 in. readings pass. The 5/32 in. reading fails; that area of the cap must be ground down to no more than 1/8 in. and re-inspected.
3. You are filling out your weld test record. Your filler is ER70S-2 and you ran the root pass at 90 A and fill/cap passes at 105 A. The WPS amperage range is 80–120 A. Were your amperages within the WPS range?
  1. Identify the WPS range: 80 A minimum, 120 A maximum.
  2. Check root pass: 90 A. Is 80 ≤ 90 ≤ 120? Yes — within range.
  3. Check fill/cap passes: 105 A. Is 80 ≤ 105 ≤ 120? Yes — within range.
  4. Record both values accurately on the weld test record; do not average them — list the actual values used per pass.
Answer: Both 90 A and 105 A fall within the WPS range of 80–120 A. Record each actual value on the test record by pass type.
4. You find a surface pit (visible porosity) on the cap that measures approximately 1/16 in. (0.0625 in.) in diameter. AWS D1.1 visual criteria for a Certified Welder test do not permit visible porosity. What action do you take before submitting the coupon?
  1. Confirm the indication is porosity (round, open pit) rather than a surface marking from a wire brush.
  2. Since AWS D1.1 prohibits visible porosity on a Certified Welder coupon regardless of size, the coupon fails visual inspection as-is.
  3. Determine whether repair is permitted under your test conditions: in a formal AWS Certified Welder test, the examiner decides; in this simulated lesson, consult your instructor.
  4. If repair is authorized: grind out the pore completely, verify no remaining porosity with a magnifier, re-weld, and re-inspect the repaired area against all visual criteria before resubmitting.
Answer: Visible porosity of any size is cause for visual rejection under AWS D1.1 Certified Welder criteria. The coupon must be repaired or rejected; no size threshold makes it acceptable on the surface.

The math in this lesson1

Learners check decimal root-gap and reinforcement readings against ±1/16 in and 1/8 in limits and amperage against WPS range.
N-Q.3
Brush up in the math halls at newSchoolWorks.com:
In class: Full fit-up and tack sequence: students receive pre-beveled coupons, measure and set root opening to WPS specification, tack weld in accordance with D1.1 requirements, and have fit-up approved by instructor before welding. · Timed test simulation: students weld a complete groove coupon under quiet, test-like conditions with no coaching; instructor observes and notes technique observations for the debrief without intervening. · Post-weld documentation and debrief: students complete a weld test record (WPS number, amperage used, filler heat number, position) and participate in an individual feedback session reviewing the coupon against AWS D1.1 visual criteria and discussing correction plans.
Materials: Pre-beveled carbon steel coupons per AWS D1.1 test coupon dimensions, GTAW inverter, argon gas, ER70S-2 filler, clamps and fixturing, weld test record forms (AWS format), weld gauge, angle grinder, PPE full set
Check: Test coupon meets all AWS D1.1 visual acceptance criteria (no cracks, porosity, undercut, or incomplete fusion visible); weld test record completed with no missing critical variable entries — both criteria required to pass lesson; coupon submitted for destructive testing in formal skills assessment.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

AWS D1.1 Certified Welder qualification practice
1. Before welding begins on a certification coupon, an instructor must review and approve the fit-up. What is the primary purpose of this step?
GTAW technique and AWS SENSE L1-2
2. During GTAW root pass welding, a welder observes a consistent keyhole at the leading edge of the puddle. What does this indicate?
AWS D1.1 visual acceptance criteria
3. AWS D1.1 visual acceptance criteria for a Certified Welder test coupon permit undercut no deeper than:
GTAW technique and NCCER Welding L1-4
4. A welder stops mid-joint during a fill pass on a GTAW groove coupon. What is the correct action before restarting the arc?
AWS Certified Welder documentation requirements
5. When completing the weld test record, which of the following is considered a critical variable that must be accurately recorded?
GTAW technique and AWS SENSE L1-2
6. In the 3G (vertical) position, which travel progression is most commonly used for GTAW structural groove welds on carbon steel to ensure adequate fusion and control of the puddle?
Welding safety and PPE — NCCER/AWS SENSE
7. Argon shielding gas presents which specific safety hazard in the welding area that welders must guard against?
AWS D1.1 visual acceptance criteria
8. A coupon cap shows weld reinforcement measuring 5/32 in. (0.156 in.) above the base metal surface. Based on the AWS D1.1 maximum of 1/8 in. (0.125 in.), what must the welder do?
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