What Is a Welding Procedure Specification (WPS)?
A welding procedure specification (WPS) is a written document that defines the welding variables required to produce a sound weld for a given application. Under AWS D1.1:2025 Clause 5.2.1, all prequalified WPSs shall be prepared by the Contractor as written prequalified WPSs. The WPS is the instruction set the welder follows — it specifies what to weld, how to weld it, and under what conditions.
The one-sentence version: The WPS is the recipe. The PQR is the proof the recipe works. A prequalified WPS under D1.1 Clause 5 needs no PQR — the code has already validated it through decades of industry use.
WPS Definition and Purpose
A Welding Procedure Specification is a formal written document that prescribes the variables for a specific welding application to assure repeatability. Every time a qualified welder picks up that WPS, they weld to the same parameters — same process, same base metal group, same filler metal, same preheat, same technique limits. That consistency is what produces predictable mechanical properties and code compliance.
Under AWS D1.1:2025 Clause 5.2.1, the written prequalified WPS may follow any convenient format. AWS Annex J provides sample forms, but fabricators can use their own format provided all required variables per Table 5.5 are addressed. The WPS is a living document: changes to essential variables beyond permitted tolerances require a new or revised WPS.
The WPS is the starting point for all welded construction under D1.1. Before the first arc is struck, the Contractor must have a written WPS that covers the specific combination of base metal, process, filler metal, position, and joint geometry being used. No WPS, no compliant weld.
What a WPS Must Contain
D1.1:2025 Table 5.5 has two sections. The upper section lists 21 variables that must be included in a written prequalified WPS. The lower section adds 10 variable tolerance entries (items 22–31) defining allowable ranges for parameters like amperage, voltage, and travel speed. Of the 21 required variables, only the Welding Process (item 1) carries a footnote requiring a separate WPS when changed — changes to other variables require a revised WPS or requalification per Clause 5.2.1.
The preheat calculator looks up variable (4) directly from D1.1:2025 Table 5.11. The carbon equivalent calculator supports the alternative preheat method from Annex B, which can reduce required preheat for certain steels. Both values belong on the written WPS.
Prequalified WPS vs. Qualification by Testing
D1.1 provides two distinct paths to a compliant WPS. Understanding the difference determines whether you need to run procedure qualification tests before starting production welding.
Prequalified WPS
Exempt from qualification testing per Clause 6. The code has validated these combinations through industry experience. No test welds, no PQR required.
Requirements: Approved process (SMAW, SAW, GMAW except GMAW-S, FCAW) + base metal from Table 5.6 + filler metal per Table 5.7 + joint from the applicable prequalified figure (Figure 5.1 for CJP, Figure 5.2 for PJP, Figure 5.3 for fillet welds) + preheat per Table 5.11.
Who uses it: Most structural fabrication shops. A36 or A572 Gr.50 steel, standard groove or fillet welds, E7018 or E71T-1 wire — fully prequalifiable.
Qualified WPS + PQR
Required when any element falls outside Clause 5 limits. A test weld is produced, specimens extracted and tested, results documented on a PQR.
Common triggers: GMAW short-circuit transfer (GMAW-S), joint geometry not in Figure 5.1, base metal not in Table 5.6, GTAW or ESW processes.
Who uses it: Specialty fabricators, pressure-boundary adjacent work, non-standard joint geometries, higher-strength steels not in Table 5.6.
Which Base Metals Can Be Used in a Prequalified WPS?
D1.1:2025 Clause 5.3 and Table 5.6 define the approved base metals for prequalified WPSs, organized into five groups by strength level. Only steels listed in Table 5.6 may be used without qualification testing. Common structural steels across the groups include:
Group I: ASTM A36, A53 Gr.B, A106 Gr.B, A131, A139 Gr.B, A381 Gr.Y35, A500 Gr.B/C, A501 Gr.A, A516 Gr.55/60, A524 Gr.I/II, A573 Gr.58/65, A709 Gr.36, A1008 SS, A1011 SS, A1018 SS, API 5L Gr.B and X42, ABS Gr.A/B/D/E.
Group II: ASTM A36 (all thicknesses), A131, A216, A501 Gr.B, A516 Gr.65/70, A529 Gr.50/55, A537 Class 1, A572 Gr.42/50/55, A588, A595, A606, A618, A633 Gr.A/C/D, A709 Gr.36/50/50W/HPS 50W, A710 Gr.A Class 2, A847, A913 Gr.50, A992, A1066 Gr.50, A1085, API 2H/2MT1/2W/2Y, API 5L X52, ABS.
Group III: ASTM A537 Class 2, A572 Gr.60/65, A633 Gr.E, A710 Gr.A Class 2 and Class 3, A913 Gr.60/65, A1018 HSLAS Gr.60/70, A1066 Gr.60/65.
Group IV: ASTM A709 HPS 70W, A913 Gr.70, A1066 Gr.70.
Group V: ASTM A913 Grade 80 — the highest-strength prequalified base metal in Table 5.6. Note: per Table 5.6 footnote, the heat input limitations of Clause 7.7 do not apply to A913 Grades 60, 65, 70, or 80.
For steels not in Table 5.6, Clause 6.2.1 governs qualification by testing. The mill test report (MTR) is the document that confirms your base metal meets the Table 5.6 specification and grade requirements before welding begins.
Prequalified Welding Processes
Per Clause 5.5.1, four processes are eligible for prequalification under D1.1:
SMAW (Shielded Metal Arc Welding) — stick electrodes classified per AWS A5.1 or A5.5. Low-hydrogen electrodes (E7018, E8018, etc.) required for Group III and IV steels and when preheat would otherwise be elevated. Table 5.1 governs SMAW prequalified WPS requirements including maximum electrode diameter by position.
SAW (Submerged Arc Welding) — single and multiple electrode configurations. Table 5.2 governs SAW prequalified WPS requirements. Preheat and interpass temperatures for parallel or multiple electrode SAW may be established by the alternate method of Clause 5.7.3 when HAZ hardness testing is performed.
GMAW (Gas Metal Arc Welding) — spray, pulse, and globular transfer only. GMAW-S (short-circuit transfer) is not prequalified and requires Clause 6 qualification. GMAW and FCAW used in prequalified WPSs shall use constant voltage (CV) power supplies per Clause 5.5.4. Table 5.3 governs GMAW solid wire requirements.
FCAW (Flux-Cored Arc Welding) — both gas-shielded (FCAW-G) and self-shielded (FCAW-S) variants. Table 5.4 governs FCAW and GMAW cored wire requirements. Shielding gas composition for GMAW and FCAW-G shall conform to AWS A5.32M/A5.32 per Clause 5.6.4.
WPS vs. PQR — The Difference
These two documents are related but serve completely different functions. Confusing them is one of the most common errors in welding documentation.
The WPS is the recipe — it tells the welder what to do. Process, base metal, filler metal, joint geometry, preheat, electrical parameters, technique. It lives on the shop floor and the welder references it during production.
The PQR is the proof the recipe works — it documents that a test weld produced to the WPS parameters passed mechanical testing. Tensile, bend, and impact tests (when required) confirm the procedure produces welds with adequate strength, ductility, and toughness. The PQR supports the WPS; the WPS references the PQR.
A prequalified WPS under D1.1 Clause 5 requires no PQR. The code itself serves as the technical justification. This is a major advantage of D1.1 over ASME Section IX, which requires procedure qualification for every WPS with no prequalified exemption.
Postweld Heat Treatment (PWHT)
PWHT may be included in a prequalified WPS provided it is approved by the Engineer and the following five conditions of Clause 5.9 are met: (1) the base metal minimum yield strength shall not exceed 50 ksi [345 MPa]; (2) the steel shall not be quenched and tempered (Q&T), quenched and self-tempered (Q&ST), thermo-mechanical controlled process (TMCP), or cold-worked to achieve higher mechanical properties (e.g., certain grades of ASTM A500 tubing); (3) there shall be no notch toughness requirements for the base metal, HAZ, or weld metal; (4) adequate strength and ductility data for the weld metal in the PWHT condition shall be available; and (5) PWHT shall be conducted in conformance with Clause 7.8.
For higher-strength steels (Group III and IV) and Q&T steels, PWHT considerations are critical. The heat input calculator helps control the thermal cycle that affects HAZ properties in these materials.
Calculators That Feed Your WPS
The variables that go into a written WPS are not guesses — they come from D1.1 table lookups and calculations. These tools produce the values directly.