AWS D1.1:2025 Table 5.11 sets minimum preheat for prequalified WPS by base metal group and thickness. CWIs and QC managers: here's how to read and apply it correctly.
Preheat is one of the first places a prequalified WPS gets rejected in a third-party audit. The fabricator followed every Clause 5 joint geometry requirement, used a listed electrode, and documented everything—but the preheat value on the WPS doesn't match what Table 5.11 requires for that combination of base metal and thickness. The whole document is compromised until the preheat is corrected and any affected production welds are dispositioned.
This article walks through how to read and correctly apply Table 5.11 for prequalified welding procedures.
Rule library based on AWS D1.1:2025; verify against your governing edition. Some projects specify D1.1:2020 or earlier—edition differences matter for table numbers and preheat values.
Why Prequalified WPS Preheat Is Different
A tested WPS (Clause 6) establishes its own preheat by doing it—whatever minimum preheat was used during PQR testing becomes the qualified minimum. The code doesn't dictate the number up front; it dictates that changes from the qualified minimum require requalification.
A prequalified WPS skips the PQR entirely. That shortcut comes with tradeoffs: you must comply with every mandatory Clause 5 parameter, including the preheat floors in Table 5.11. There is no negotiation and no "close enough." If Table 5.11 says 150°F for your base metal and thickness, your WPS must state at least 150°F and the field must achieve it before arc initiation.
How Table 5.11 Is Organized
Table 5.11 in AWS D1.1:2025 organizes requirements along two axes:
Base metal category. Base metals eligible for prequalified WPS are listed in Table 5.6, grouped into categories. Table 5.11 rows correspond to those categories. Common structural steels—A36, A53, A500 Grade B/C, A501, A572 Grades 42 and 50, A992, A588, A913—map to specific rows. Quenched-and-tempered steels such as A514 and A517 sit in their own row with higher minimums.
Base metal thickness at the joint. Columns step through thickness ranges. Thinner material at the joint generally requires lower preheat; thicker material requires more. The cutoff points between thickness bands are not arbitrary—they reflect the increased risk of hydrogen cracking as heat sinks grow with thickness.
The intersection of your base metal category and the thickness of the thicker part at the joint gives you the required minimum preheat and interpass temperature.
The Thicker-Member Rule
This is where most errors occur in production, especially on beam-column connections.
The governing thickness for determining preheat is the thicker of the two pieces being joined. For a W18×97 beam connecting to a W14×233 column with a CJP beam flange weld:
Beam flange thickness: approximately 0.870 inches
Column flange thickness: approximately 1.720 inches
Preheat requirement is based on the 1.720-inch column flange, not the beam flange. Welders who apply the preheat chart to the thinner piece—the piece they're actually welding onto—will often fall short of the requirement at the column flange.
The practical solution: on your preheat procedure card or WPS cover sheet, list the governing thickness explicitly by connection type. A fabricator with a consistent connection portfolio can pre-calculate the governing thickness for each joint type and post it in the fab bay.
Quenched-and-Tempered Steels: A Two-Sided Requirement
For A514, A517, and similar Q&T steels, Table 5.11 sets both a minimum preheat and a maximum interpass temperature. The minimum protects against hydrogen cracking; the maximum protects the base metal's mechanical properties by preventing the heat-affected zone from overtemping and losing the strength imparted during quenching and tempering.
CWIs inspecting Q&T steel welds must verify both sides of the interpass temperature window on every pass. A thermocouple or contact thermometer between passes is the only reliable method—hand checks are not adequate when precision matters. See Interpass Temperature Control for Structural Welding for measurement methods and documentation requirements.
The Role of Low-Hydrogen Electrodes
AWS D1.1 allows reduced preheat when low-hydrogen electrodes with appropriate H-designator classifications are used. The H-suffix designator on an electrode—H4, H8, or H16—indicates the diffusible hydrogen content in milliliters per 100 grams of deposited weld metal. Lower hydrogen content enables lower preheat at a given thickness.
For prequalified WPS to take advantage of these reductions, the WPS must specify the electrode's H-suffix classification, and the actual electrodes used in production must be stored, handled, and conditioned per the manufacturer's requirements. Electrode that absorbs moisture in a humid shop environment loses its low-hydrogen designation. If the electrode's actual diffusible hydrogen content is questionable, the preheat reduction evaporates—the WPS should be revised to the baseline Table 5.11 preheat for that condition.
AWS D1.1:2025 Annex B provides a carbon equivalent method for calculating alternative preheat temperatures. This method is explicitly labeled as an alternative—it can be used instead of Table 5.11 for prequalified WPS when specific conditions are met. The Annex B result may be higher or lower than Table 5.11 depending on the steel chemistry.
Fabricators working with material where the heat certificate shows elevated carbon equivalent values sometimes find Annex B produces a more conservative result than Table 5.11. Others find relief. Either way, if you invoke Annex B, the WPS must document the basis for the alternative preheat including the calculated carbon equivalent and source data.
The same Table 5.11 requirements apply to prequalified fillet welds, not just groove welds. A common misconception is that small fillet welds on thin material don't need preheat. If Table 5.11 requires preheat for that base metal category at the thickness present, it applies regardless of weld type or size.
One clarification: Table 5.11 minimum preheat is based on the base metal at the joint, not the weld size. A 1/4-inch fillet weld on a 1-1/2-inch plate still requires preheat per Table 5.11 based on the plate thickness. Note that Table 7.7, which governs minimum fillet weld size, uses the thinner part joined (T) as its controlling dimension for low-hydrogen processes—a different parameter entirely from the preheat thickness lookup in Table 5.11.
Field Verification and Documentation
The CWI's job at the joint isn't just to confirm the WPS says the right temperature—it's to confirm the base metal actually reached that temperature before arc initiation. Temperature measurement methods accepted by AWS D1.1 include:
Calibrated temperature-indicating crayons (Tempilstik or equivalent) — economical, reasonably accurate; verify the crayon rating matches the required temperature
Digital contact thermometers with calibrated probes — more precise, appropriate for Q&T steels and applications where the interpass ceiling matters
Infrared (IR) pyrometers — useful for remote measurement but susceptible to emissivity error on shiny steel surfaces; calibrate against a contact thermometer reading
Measurement location: for groove and fillet welds, temperature should be checked at or near the joint, on the base metal, typically 3 inches from the fusion zone. For Q&T steels the interpass temperature should be checked immediately before each new pass, at the joint location.
Document the measured preheat temperature on the welder's production log or the CWI daily inspection record. If preheat was not achieved before the welder struck an arc, that is a WPS departure—log it, notify the QC lead, and determine the disposition.
Tying It to the WPS Format
The WPS must explicitly state both the minimum preheat and the minimum interpass temperature required by Table 5.11. For Q&T steels, the WPS must also state the maximum interpass temperature. Many WPS forms have dedicated blocks for these values; Annex J Form J-1 in AWS D1.1:2025 provides the reference layout.
When multiple base metals or multiple joint types appear under a single WPS, list the governing preheat for each combination. A shop WPS that covers both A36 material and A572 Grade 50 at various thicknesses should either scope down to a single temperature that covers all combinations, or explicitly table the preheat by material/thickness scenario with notes directing the welder and inspector to the correct value.
When the WPS Preheat Is Wrong
If an audit or third-party review finds that the WPS states a preheat below the Table 5.11 requirement for the material and thickness, the fix is straightforward:
Revise the WPS to state the correct minimum preheat
Issue the revised WPS under change control (new revision level, dated)
Conduct a review of production welds made under the non-compliant WPS
Work with the EOR to disposition any welds where preheat was likely deficient—this typically involves documented evidence of actual preheat achieved (welder logs, CWI records) or NDE
The WPS revision itself does not require a new PQR—prequalified status is retained as long as you remain within all Clause 5 parameters. The documentation gap is a paperwork fix; the production weld disposition may be more involved.
Table 5.11 is non-negotiable for prequalified WPS. The key application points:
Use the thicker base metal at the joint to find the governing thickness
Apply the preheat category that matches your base metal's classification in Table 5.6
For Q&T steels, enforce both the minimum preheat and the maximum interpass temperature
Document actual preheat measurements in production—not just the WPS requirement
Low-hydrogen electrode H-designators can reduce required preheat, but storage and conditioning must be maintained
A WPS that states the correct Table 5.11 preheat, paired with a CWI who verifies and documents it in the field, is the combination that keeps prequalified procedures audit-ready and structurally sound.
Table 5.11 lists the minimum preheat and interpass temperatures required for prequalified welding procedures, organized by base metal category and base metal thickness at the joint. It is a mandatory requirement under Clause 5 for any WPS claiming prequalified status.
Does Table 5.11 apply to tested (Clause 6) WPS?
No. Table 5.11 is specific to prequalified WPS governed by Clause 5. For tested WPS qualified under Clause 6, preheat is established during PQR testing—the minimum is what was used during qualification, and any decrease below that value is an essential variable requiring requalification.
Which base metal thickness governs when two different materials meet at a joint?
For a prequalified groove weld, the thicker of the two base metals at the joint governs the preheat requirement. This is a common CWI gotcha: a 3/8-inch beam web welded to a 1-1/4-inch column flange requires preheat based on the column flange thickness, not the web.
Can you exceed the Table 5.11 minimum preheat?
Yes, always. Table 5.11 is a floor, not a ceiling—except for quenched-and-tempered steels, where an excessive interpass temperature ceiling also applies to protect the base metal's mechanical properties. The WPS must state both the minimum preheat and, for Q&T steels, the maximum interpass temperature.