5.2 Performance Test Evaluation (Visual, Guided Bend, Macroetch) & Retest Rules

Visual Examination of Performance Coupons (Clause 6.23)

Visual examination is the mandatory first line of evaluation for all welder performance test coupons. Per AWS D1.1 Clause 6.23, the test coupon must be visually examined over its entire surface prior to cutting guided bend specimens or performing non-destructive testing. If the coupon fails visual inspection, no mechanical testing or NDT shall be performed, and the welder fails the test.

+-----------------------------------------------------------------------------------------+
|             WELDER PERFORMANCE COUPON VISUAL ACCEPTANCE CRITERIA (Clause 6.23)        |
+-----------------------------------------------------------------------------------------+
|                                                                                         |
|  DISCONTINUITY TYPE         ACCEPTANCE CRITERIA / LIMITS                                |
|  =====================================================================================  |
|  Cracks                     NONE permitted (Zero tolerance)                             |
|  Lack of Fusion             NONE permitted between weld/base metal or weld passes       |
|  Incomplete Penetration     NONE permitted for CJP groove welds                         |
|  Crater Cross Section       All craters shall be filled to the full cross section       |
|  Weld Reinforcement         Groove face reinforcement <= 1/8 in. [3 mm]                 |
|  Weld Profile / Flushness   Substantially flush, uniform, merging smoothly into base    |
|  Undercut                   Depth <= 1/32 in. [1 mm]                                    |
|  Root Surface (Open Root)   No melt-through > 1/8 in. [3 mm]; concavity <= 1/16 in.     |
|  Porosity                   Sum of visible piping porosity <= specified limits          |
|                                                                                         |
+-----------------------------------------------------------------------------------------+

[!IMPORTANT] The visual inspection standard for welder qualification coupons in Clause 6.23 is more stringent than production visual inspection in Table 8.1. For instance, while Table 8.1 permits undercut up to $1/16\text{ in.} \ [2\text{ mm}]$ under certain conditions in production, performance qualification coupons restrict undercut to a strict maximum of $1/32\text{ in.} \ [1\text{ mm}]$.

Guided Bend Testing Mechanics & Acceptance Criteria (Clause 6.23)

Guided bend testing subjects the outer fibers of the weld metal and heat-affected zone (HAZ) to severe plastic strain (approximately 20% elongation in standard jigs), mechanically forcing any lack of fusion, slag inclusions, or internal cracks to open to the surface.

                        Guided Bend Specimen Orientations

    Transverse Root Bend                  Transverse Face Bend              Side Bend (t >= 3/8 in.)
   (Root in outer tension)               (Face in outer tension)             (Cross-section in tension)

        Weld Face (Down)                      Weld Root (Down)                     Side View (t = 1 in.)
      +------------------+                  +------------------+                   +------------------+
      |                  |                  |                  |                   | |   Weld Cross   | |
      |  //// Weld ////  |                  |  //// Weld ////  |                   | |    Section     | |
      +------------------+                  +------------------+                   +------------------+
        Weld Root (Up)                        Weld Face (Up)                         Weld Surface
         (Tension Side)                        (Tension Side)                        (Tension Side)

Specimen Selection by Coupon Thickness

• Thickness $T < 3/8\text{ in.} \ [10\text{ mm}]$: Requires one transverse root bend and one transverse face bend.
• Thickness $T = 3/8\text{ in.} \ [10\text{ mm}]$: Permitted to use two side bends OR one root bend and one face bend.
• Thickness $T > 3/8\text{ in.} \ [10\text{ mm}]$ (e.g., $1\text{ in.}$ plate): Requires two side bend specimens.

Guided Bend Acceptance Criteria (Clause 6.23)

After bending in a standardized plunger-and-die jig to a full $180^\circ$ U-bend, the convex surface of the specimen is examined for discontinuities:

1. Maximum Single Discontinuity: The convex surface shall contain no open discontinuity exceeding $1/8\text{ in.} \ [3\text{ mm}]$ measured in any direction.
2. Corner Cracks Exception: Cracks occurring on the corners of the specimen during bending shall not be considered unless there is definite visual evidence that they result from internal slag inclusions, lack of fusion, or other internal defects (in which case the $1/8\text{ in.}$ limit applies).
3. Sum of Discontinuities: The sum of the greatest dimensions of all open discontinuities exceeding $1/32\text{ in.} \ [1\text{ mm}]$ but less than or equal to $1/8\text{ in.} \ [3\text{ mm}]$ shall not exceed $3/8\text{ in.} \ [10\text{ mm}]$ across the convex surface.

NDT Substitution Rules & The GMAW-S Exception (Clause 6.23)

Under AWS D1.1 Clause 6.23, a contractor may elect to substitute non-destructive examination for destructive guided bend testing on welder performance test coupons, subject to strict code limitations:

+-----------------------------------------------------------------------------------------+
|                        NDT SUBSTITUTION FOR PERFORMANCE QUALIFICATION                   |
+-----------------------------------------------------------------------------------------+
|                                                                                         |
|   PERMITTED NDT SUBSTITUTIONS:                                                          |
|   * Radiographic Testing (RT): Permitted for groove weld coupons on plate or pipe       |
|   * Ultrasonic Testing (UT): Permitted for groove weld coupons on plate or pipe         |
|     where thickness t >= 5/16 in. [8 mm]                                                |
|                                                                                         |
|   CRITICAL CODE PROHIBITION (Clause 6.23):                                          |
|   * GMAW-S (Short-Circuiting Transfer) CANNOT be qualified by RT or UT.                 |
|   * Welders qualifying on GMAW-S MUST undergo destructive guided bend testing.          |
|                                                                                         |
+-----------------------------------------------------------------------------------------+

Why RT/UT is Prohibited for GMAW-S Performance Qualification

In GMAW-S, the low heat input and cyclic short-circuiting mode frequently result in microscopic sidewall lack of fusion (cold lap). These planar discontinuities are extremely tight, closed, and oriented parallel to the radiographic beam, making them virtually invisible on radiographic film or digital radiography. Furthermore, their acoustic reflectivity can be obscured by base metal geometry. Because guided bend testing applies direct tensile strain across the fusion boundary—mechanically tearing open any unbonded interfaces—bend testing is mandatory for GMAW-S.

Tack Welder Qualification (Clause 6.24 & Figures 6.20/6.27)

A tack welder is qualified by welding a standardized fillet-weld-break test assembly (Figure 6.27, ruptured per Figure 6.20):

• Test Assembly: Consists of two plates joined with a single $1/4\text{ in.} \ [6\text{ mm}]$ maximum fillet tack weld, minimum $2\text{ in.} \ [50\text{ mm}]$ in length.
• Mechanical Testing: The specimen is loaded mechanically to force the root of the weld into tension until the joint fractures or bends flat upon itself.
• Acceptance Criteria: The fractured surfaces must show complete penetration into the root, complete fusion to the base metal, and no inclusion or porosity exceeding $3/32\text{ in.} \ [2.5\text{ mm}]$ in greatest dimension.
• Macroetch Test: If the specimen does not fracture under load, it is cut transversely and macroetched to verify penetration, fusion, and sound weld cross section.

Retest Regulations (Clause 6.25)

When a welder, welding operator, or tack welder fails a performance qualification test, Clause 6.25 governs the retest requirements based on whether additional training is provided.

+-----------------------------------------------------------------------------------------+
|                             AWS D1.1 RETEST PATHWAYS (Clause 6.25)                      |
+-----------------------------------------------------------------------------------------+
|                                                                                         |
|   PATHWAY 1: IMMEDIATE RETEST (NO TRAINING)                                             |
|   * Trigger: Retest requested immediately without further practice or training.         |
|   * Requirement: Welder must weld TWO (2) consecutive test coupons of each type         |
|     and position failed.                                                                |
|   * Acceptance: BOTH coupons must satisfy all visual and mechanical/NDT requirements.   |
|     If either coupon fails a single specimen, the welder fails the retest.              |
|                                                                                         |
|   PATHWAY 2: RETEST AFTER FURTHER TRAINING                                              |
|   * Trigger: Welder receives verified additional training or practice.                  |
|   * Requirement: Welder must weld ONE (1) test coupon of each type and position failed. |
|   * Acceptance: The single coupon must satisfy all standard qualification criteria.      |
|                                                                                         |
+-----------------------------------------------------------------------------------------+

Summary Table of Retest Rules