1. Testing Requirements (QW-451)

Clause QW-451 of ASME BPVC Section IX defines the specific type and quantity of test specimens required to qualify a groove weld Procedure Qualification Record (PQR). Table QW-451.1 cross-references test coupon thickness to mandatory specimen types, establishing that both tensile and transverse guided bend specimens must be tested for every groove weld PQR qualification.

2. Purpose of Mechanical Tests

Clause QW-141 defines the intended objective of each mechanical test performed during PQR qualification. Understanding what each test measures is just as important as understanding how to perform it. The two primary tests — tension and guided bend — serve distinct and complementary purposes.

2.1 Tension Test

The tension test is performed to determine the ultimate tensile strength of a groove weld joint. It verifies that the completed weld is capable of withstanding the mechanical loads it will encounter in service. Learn more about how mechanical properties influence weld performance.

2.2 Guided Bend Test

The guided bend test evaluates the soundness and ductility of a groove weld joint. By bending a specimen over a mandrel to a prescribed angle, the test reveals any subsurface discontinuities such as lack of fusion, slag inclusions, or porosity that might not be visible on the surface.

3. Number of Specimens Required

Table QW-451.1 specifies not only the type but also the minimum quantity of each specimen. The required count varies based on the test coupon thickness used during PQR qualification.

3.1 Tensile Specimens

Regardless of the test coupon thickness, a minimum of two (2) tensile specimens must always be tested. Specimens are prepared in accordance with QW-151 as reduced-section tensile specimens applicable to both plate and pipe test coupons.

The following rules govern specimen size relative to coupon thickness:

• When T ≤ 25 mm, full-thickness specimens are required.
• When T > 25 mm, full-thickness specimens are preferred. However, if the available tensile testing machine cannot accommodate full-thickness specimens, the coupon may be mechanically cut into the minimum number of equal strips (sub-size specimens) that can be tested on the available equipment.
• When multiple sub-size specimens are used, they must collectively represent the full thickness of the weld at that location and are treated as a single set.
• Every specimen in the set must individually meet the minimum strength requirements of the applicable construction code.

3.2 Bend Specimen Locations and Quantity

The number and type of guided bend specimens depend on the test coupon thickness, as defined in Table QW-451.1:

• T < 10 mm: Two face bend specimens and two root bend specimens are mandatory.
• 10 mm ≤ T < 19 mm: Either two face bend + two root bend specimens, or four side bend specimens are required.
• T ≥ 19 mm: Four side bend specimens are mandatory.
• Low-ductility materials (elongation < 3%): Macro-examination specimens are required in lieu of guided bend tests.

The three transverse guided bend orientations are defined as follows:

• Transverse Side Bend: One side of the weld surface becomes the convex (outer) surface of the bent specimen.
• Transverse Face Bend: The weld face surface becomes the convex surface of the bent specimen.
• Transverse Root Bend: The weld root surface becomes the convex surface of the bent specimen.

4. Location of Specimen Extraction

The locations from which tensile and guided bend specimens must be cut are governed by ASME BPVC Section IX Figures QW-463.1(a) through QW-463.1(e) for both plate and pipe test coupons. These figures define the exact orientation and position of each specimen within the welded coupon to ensure consistent, representative sampling across the full weld cross-section.

For pipe test coupons, the same figures define extraction positions relative to the pipe circumference and wall thickness. All specimens must be taken in strict accordance with these figures to ensure PQR validity.

5. Acceptance Criteria

5.1 Tension Test Acceptance (QW-153)

The tensile strength acceptance criteria are defined in clause QW-153, with minimum required values specified in Table QW/QB-422. A tensile specimen is considered acceptable if any of the following conditions are satisfied:

• The specimen tensile strength is not less than the minimum specified tensile strength of the base metal.
• When two dissimilar base metals are joined, the specimen tensile strength is not less than the minimum specified tensile strength of the weaker of the two base metals.
• When the applicable construction code permits a weld deposit with lower tensile strength than the base metal at room temperature, the specimen tensile strength may be not less than the minimum specified tensile strength of the weld filler metal.
• If the specimen fractures in the base metal outside the weld or weld interface, the result is acceptable provided the measured strength is within 5% of the minimum specified tensile strength of the base metal.

The following table illustrates worked examples applying each acceptance condition:

5.2 Guided Bend Test Acceptance (QW-163)

Acceptance of guided bend specimens is assessed by examining the convex surface of the bent specimen for open discontinuities after bending.

Groove Welds: After bending, no open discontinuity in the weld or heat-affected zone (HAZ) may exceed 3 mm (1/8 in.) measured in any direction on the convex surface. Corner discontinuities are not penalized unless there is clear evidence they originate from lack of fusion, slag inclusions, or other internal weld defects.

Corrosion-Resistant Weld Overlay Cladding: A tighter standard applies — no open discontinuity exceeding 1.5 mm (1/16 in.) is permitted within the cladding layer, and no discontinuity exceeding 3 mm (1/8 in.) may appear along the weld interface.