1a) Groove Weld — Table QW-451.1 (Transverse-Bend Tests)

Table QW-451.1 is the baseline thickness qualification table for groove weld procedure qualification using tension and transverse guided-bend tests. It defines both the qualified range of base metal thickness T and the maximum qualified deposited weld metal thickness t, with the coupon thickness as the reference point. The table has six coupon thickness bands:

Table Notes (ASME Section IX 2025):

• Note (1): QW-403.9 further restricts the limits shown when referenced in QW-250 for the process under consideration. QW-202.2, QW-202.3, and QW-202.4 provide exemptions that supersede the limits. Supplementary essential variable requirements may also further limit thickness ranges.
• Note (2): For combination of welding procedures, see QW-200.4.
• Note (3): Applies to SMAW, SAW, GMAW, PAW, LLBW, and GTAW only. For all other processes: 2T and 2t apply as applicable.
• Note (4): See QW-151.1, QW-151.2, and QW-151.3 for multiple specimens when coupon thickness exceeds 1 in (25 mm).
• Note (5): Four side-bend tests may be substituted for face and root bends when T is 3/8 in (10 mm) and over.
• Note (6): For coupons over 6 in (150 mm) thick, the full thickness of the test coupon shall be welded.

Fig. 1 — ASME Section IX Table QW-451.1: Groove-Weld Tension Tests and Transverse-Bend Tests. The minimum qualified base metal T is a fixed absolute value — not a fraction of T — for all coupon thicknesses of 1/16 in (1.5 mm) and above.

1b) Groove Weld — Table QW-451.2 (Longitudinal-Bend Tests)

Table QW-451.2 is an alternative for groove weld procedure qualification using longitudinal guided-bend tests instead of transverse bends. It is used when the base or weld metal properties would prevent a valid transverse bend — for example with dissimilar-strength combinations. The thickness structure is simpler than QW-451.1:

Unlike QW-451.1, Table QW-451.2 has no 8 in (200 mm) or 1.33T provision for thick coupons — the maximum is always 2T regardless of coupon thickness or welding process. The same Notes (1) and (2) from QW-451.1 apply, meaning QW-403.9 and the QW-202 exemptions operate identically.

1c) Fillet Weld — Tables QW-451.3 and QW-451.4

Fillet weld procedure qualification operates under a fundamentally different rule: there are no base metal thickness limits in either direction, and no weld metal deposit thickness restriction.

A fillet-only PQR (QW-451.3) does not qualify groove welds. A groove-weld PQR automatically qualifies fillet welds of all sizes and thicknesses per QW-451.4, with no additional testing required.

Fig. 2 — Tables QW-451.3 and QW-451.4: Fillet weld procedure qualification. All fillet sizes, all base metal thicknesses, and all diameters are qualified — no upper or lower base metal thickness restriction applies.

1d) Impact Test Requirement — QW-403.6 (Supplementary Essential Variable)

QW-403.6 is a supplementary essential variable. It activates only when toughness testing (impact testing) of the heat-affected zone is required by the referencing code section. When it applies, it modifies only the minimum qualified base metal thickness from Table QW-451.1 — it does not change the maximum. The exact text from ASME Section IX 2025:

In practice this gives three conditions based on coupon thickness:

QW-403.6 does not apply under any of the following conditions:

• (a) The WPS is qualified with a heat treatment above the upper transformation temperature.
• (b) The WPS is for welding austenitic or P-10H material qualified with a solution heat treatment.
• (c) Base metals are assigned to P-No. 8, P-Nos. 21 through 26, or P-Nos. 41 through 49.

Fig. 3 — QW-403.6: Supplementary essential variable for minimum qualified base metal thickness when impact testing is required. Modifies only the minimum from QW-451.1 — not the maximum.

1e) Pass Thickness Restriction — QW-403.9 (Essential Variable)

The exact text from ASME Section IX 2025, QW-403.9:

When any individual weld pass in the PQR test coupon exceeds 13 mm in thickness, the maximum qualified production base metal thickness is 1.1 × T of the test coupon — overriding the higher maximum that Table QW-451.1 would otherwise allow. QW-403.9 is an essential variable referenced in Table QW-451.1 Note (1). It restricts base metal thickness, not weld metal deposit thickness.

The restriction reflects the metallurgical reality that thick individual passes deliver significantly higher heat input per unit volume and create a different HAZ thermal cycle than stringer beads — particularly relevant for Cr-Mo steels such as P91 and for toughness-critical applications. To qualify for a larger production base metal thickness, either the coupon must be thicker, or the WPS must be re-qualified using passes not exceeding 13 mm.

Fig. 4 — QW-403.9: When any weld pass in the PQR exceeds 1/2 in (13 mm), the maximum qualified production base metal thickness is restricted to 1.1 × T of the test coupon.

Fig. 5 — Individual pass thickness in a multi-pass groove weld. Any single pass exceeding 13 mm (1/2 in) triggers the QW-403.9 restriction on maximum qualified base metal.

1f) Short-Circuit GMAW — QW-404.32 (Essential Variable)

The exact text from ASME Section IX 2025, QW-404.32:

Three important points follow directly from the code text:

• The 1.1× restriction applies only when the PQR deposited weld metal is less than 1/2 in (13 mm). At 13 mm or more, the normal QW-451 tables govern with no additional restriction from this clause.
• The restriction is on deposited weld metal thickness — not base metal thickness.
• This clause sits in the filler metal variables section (QW-404), not the base metal section (QW-403). The parallel restriction for welder qualification is found in QW-355.

Short-circuit transfer is a low-heat-input mode used for thin material, root passes, and out-of-position welding. Its fusion characteristics on heavier material differ significantly from those demonstrated on a thin coupon, which is why this additional restriction exists. For full process details see the GMAW welding guide.

Fig. 6 — QW-404.32: Short-circuit (low-voltage) GMAW restriction on deposited weld metal thickness. The 1.1×t limit applies only when the PQR deposit is less than 1/2 in (13 mm). At 13 mm or greater, QW-451.1 or QW-451.2 govern normally.

1g) Dissimilar Base Metal Thicknesses — QW-202.4

When a production groove weld joins two members of different thicknesses, QW-202.4 of ASME Section IX 2025 governs whether the WPS applies. The clause provides both a general rule and specific exemptions based on P-Number:

• (a) The thickness of the thinner member shall be within the range permitted by QW-451.
• (b)(1) — P-No. 8, P-No. 41, P-No. 42, P-No. 43, P-No. 44, P-No. 45, P-No. 46, P-No. 51, P-No. 52, P-No. 53, P-No. 54, P-No. 61, P-No. 62, and P-No. 81: No limitation on the maximum thickness of the thicker production member, provided the PQR coupon was at least 1/4 in (6 mm) thick.
• (b)(2) — All other P-Numbers: The thicker member shall be within the range permitted by QW-451, except there is no upper limit on the thicker member when the PQR coupon was at least 1-1/2 in (38 mm) thick.

More than one PQR may be required for some dissimilar-thickness combinations. This provision is commonly encountered in nozzle-to-shell welds on pressure vessels, where the nozzle neck and shell plate can differ substantially in wall thickness.

Fig. 7 — QW-202.4: Qualification rules for production welds between base metals of dissimilar thickness.

Fig. 8 — Dissimilar-thickness joint. Each member is evaluated independently against the qualified range.

1h) Overlay Qualification — Table QW-453

Table QW-453 governs procedure and performance qualification for both corrosion-resistant overlays and hard-facing (wear-resistant) overlays. The threshold coupon thickness in both cases is 1 in (25 mm). In all overlay cases there is no restriction on the deposited overlay thickness — qualification is based on the substrate (base metal) thickness only.

The key distinction between overlay types: for hard-facing procedure qualification on coupons less than 1 in (25 mm), the qualified base metal thickness has both a lower bound (T) and an upper bound (1 in / 25 mm). For corrosion-resistant procedure qualification with thin coupons, there is no upper bound — any base metal thickness at or above T is qualified.

Fig. 9 — Table QW-453: Qualification thickness limits for corrosion-resistant and hard-facing overlay procedures and welder qualification. Deposited overlay thickness is unrestricted in all cases.

1i) ASME B31.3 Construction Code — Impact Test Override

When the governing construction code is ASME B31.3 (Process Piping) and impact testing is required, the qualified base metal thickness range is governed by ASME B31.3 Table 323.3.1, not by QW-403.6 of Section IX. This is established by QG-100(b) of ASME Section IX, which states that when the referencing code imposes additional restrictions, those restrictions govern. This position was confirmed by ASME Code Interpretation Record No. 15-586. Fabricators working under B31.3 must check Table 323.3.1 explicitly whenever impact testing is required — not only QW-403.6.

Fig. 10 — ASME B31.3 Table 323.3.1: Qualified base metal thickness range when impact testing is required under the B31.3 process piping code. Governs over QW-403.6 of Section IX per QG-100(b) and Code Interpretation 15-586.

2a) Groove Weld WPQ — Table QW-452.1(b)

The complete table from ASME Section IX 2025:

Table Notes from ASME Section IX 2025:

• Note (1): When more than one welder, process, or set of essential variables is used, the thickness t deposited by each welder, for each process, and with each set of essential variables is determined and used individually to determine the qualified weld metal thickness.
• Note (2): Two or more pipe test coupons with different weld metal thicknesses may be used to determine the qualified weld metal thickness, applicable to production welds at the smallest qualified diameter per Table QW-452.3.
• Note (3): A test coupon of 3/4 in (19 mm) or over shall be used for qualifying a combination of three or more welders each using the same or a different welding process.

Fig. 12 — Table QW-452.1(b): Qualified weld metal deposit thickness for Welder Performance Qualification (WPQ). Base metal thickness limits are not applicable to welder qualification.

2b) Short-Circuit GMAW Welder Qualification — QW-355

When short-circuit GMAW was used during welder qualification and the deposited weld metal in the test coupon was less than 1/2 in (13 mm), the maximum qualified production weld metal deposit is limited to 1.1 times the test deposit — exactly mirroring QW-404.32 for procedure qualification. For weld metal deposits of 1/2 in (13 mm) or greater, Tables QW-452.1(a) and QW-452.1(b) apply normally with no additional restriction from this clause.

Fig. 13 — QW-355: Short-circuit GMAW welder qualification deposit restriction. Max deposit = 1.1×t of the qualification test when t < 1/2 in (13 mm). At 13 mm or more, QW-452.1(b) applies normally.

2c) Overlay WPQ — Table QW-453 (Performance Qualification)

For welder qualification on overlay work, the performance qualification rows of Table QW-453 apply. Welding operators qualify for all base metal thicknesses in every case. Welders are subject to the base metal thickness restriction tied to coupon thickness:

• Corrosion-resistant overlay: Coupon < 1 in (25 mm) — welders qualify base metal ≥ T. Coupon ≥ 1 in (25 mm) — welders qualify base metal ≥ 1 in (25 mm). Operators: all thicknesses.
• Hard-facing overlay: Same structure as corrosion-resistant for performance qualification — welders qualify base metal ≥ T for thin coupons and ≥ 1 in (25 mm) for thick coupons; operators qualify all.
• Deposited overlay thickness: no restriction in any case.

Fig. 14 — Table QW-453 performance qualification (WPQ). Welding operators qualify for all base metal thicknesses regardless of coupon size. No restriction on deposited overlay thickness.