It's 9 pm. You've got a structural steel job starting Monday — column splices, multi-pass groove welds, AWS D1.1 jurisdiction. The GC wants a WPS on file before your crew strikes an arc. You have a MIG machine, an ER70S-6 spool, and a legal pad.
A Welding Procedure Specification isn't paperwork for its own sake. It's the document that tells your welder exactly how to run the bead: process, filler, voltage, amperage, preheat, interpass temperature — every variable that affects whether the joint passes inspection or fails in the field. This guide walks through AWS D1.1 from scratch, with a real worked example you can adapt tonight.
A Welding Procedure Specification (WPS) is a formal written document that defines the parameters a welder must follow to produce a code-compliant joint. Think of it as a recipe: the WPS specifies the ingredient list (filler metal, base metal, shielding gas) and the cooking instructions (amperage, voltage, travel speed, preheat, interpass temperature).
Under AWS D1.1 (the Structural Welding Code — Steel, 2020/2025 edition), you have two paths to a valid WPS:
This guide focuses on prequalified procedures — the path most welding shops use for structural carbon steel work.
The WPS is the instruction document that goes in the welder's hand on the job. The PQR is the test record that proves the WPS produces acceptable welds. Prequalified WPSs are exempt from the PQR requirement because the code itself has already validated those parameters through decades of engineering testing.
An essential variable is any parameter that, if changed beyond the allowed range, requires the WPS to be requalified. For prequalified procedures, Table 5.2 of AWS D1.1 defines the essential variables and their allowable limits.
| # | Essential Variable | What to Specify |
|---|---|---|
| 1 | Welding Process | SMAW, GMAW, FCAW, SAW (GTAW is NOT prequalified under D1.1 for structural steel) |
| 2 | Base Metal | ASTM specification (A36, A572), P-Number group, thickness range (min/max) |
| 3 | Filler Metal | AWS classification (ER70S-6), F-Number, A-Number, diameter |
| 4 | Joint Design | Groove type (V, U, J, bevel), groove angle, root opening, root face, backing (yes/no) |
| 5 | Welding Position | 1G/1F (flat), 2G/2F (horizontal), 3G/3F (vertical), 4G/4F (overhead) |
| 6 | Preheat Temperature | Minimum preheat per Table 5.8; maximum interpass temperature |
| 7 | Post-Weld Heat Treatment | Required or not; if required: temperature range, hold time, heating/cooling rate |
| 8 | Shielding Gas | Gas composition (75% Ar / 25% CO₂), flow rate (CFH) |
| 9 | Electrical Characteristics | Current type (DCEP/DCEN/AC), amperage range, voltage range |
| 10 | Travel Speed | Minimum and maximum ipm (inches per minute) |
| 11 | Electrode Diameter | Wire diameter (0.035", 0.045"); Table 5.1 max diameter limits apply |
| 12 | Transfer Mode (GMAW) | Short circuit, spray, or pulsed — each has different D1.1 allowances |
| 13 | Number of Passes | Single-pass vs. multi-pass; max single-pass fillet size per Table 5.1 |
| 14 | PQR Reference (qualified only) | PQR number and date; not required for prequalified WPS |
Non-essential variables (travel angle, torch orientation, interpass cleaning method) can be modified within a WPS without requalification — but they still need to be documented. Supplementary essential variables apply only when the contract specifically requires notch toughness (CVN impact) testing.
A WPS doesn't have a mandated form layout — AWS D1.1 specifies what information must be present, not how you format it. Here's what goes in each field:
State the process and whether it's manual, semiautomatic, mechanized, or automatic. Example: GMAW — Semiautomatic. If your procedure covers a root pass (GTAW) followed by fill passes (FCAW), you need a separate WPS for each process, or a combined procedure with both fully documented.
Specify the ASTM designation (A36, A572 Gr. 50, A992) and the applicable D1.1 base metal group from Table 5.3. A36 is in Group I. Document the qualified thickness range — for prequalified groove welds, a range up to unlimited thickness is achievable if the joint geometry stays within Clause 5 limits.
List the AWS filler metal specification and classification: e.g., AWS A5.18, ER70S-6, 0.045". The tensile strength of the filler must match or exceed the base metal. For A36 (min 58 ksi tensile), ER70S-6 (70 ksi min) works. Include the F-Number (F6 for ER70S-6) and A-Number (A1) — these define the PQR qualification range if you ever need a qualified procedure from this WPS.
Reference the prequalified joint detail from AWS D1.1 Figure 5.1. Common: TC-U4a (single-V groove with backing, unlimited thickness). Specify groove angle (typically 45° for single-V), root opening (0–1/4"), root face (0–1/8"), and whether a backing bar is used. Draw a simple cross-section if your form has space.
For GMAW on carbon steel, 75% Ar / 25% CO₂ (C25) is standard for short-circuit and spray transfer. Flow rate: 35–45 CFH for most conditions; bump to 45–50 CFH for out-of-position work or drafty environments. FCAW-S (self-shielded) uses no gas — leave the shielding gas field N/A.
AWS D1.1 Table 5.8 gives minimum preheat requirements by base metal group and thickness. For A36 steel:
Maximum interpass temperature for most structural applications: 550°F. Document both the minimum preheat and the maximum interpass temperature on the WPS.
Document current type and polarity first: GMAW typically runs DCEP (electrode positive). Then specify the amperage and voltage range for each pass category (root, fill, cap). Don't use a single value — give a range. Heat input formula: H = (E × I × 60) / (S × 1,000) where H = kJ/in, E = volts, I = amps, S = travel speed in in/min.
Here's a complete prequalified WPS for a common structural application — GMAW on A36 flat-position groove weld with steel backing. Every field filled in as it would appear on a real WPS form.
| WPS Field | Value |
|---|---|
| WPS Number | WPS-001-GMAW-A36 |
| Revision | 0 — dated 2026-05-14 |
| Supporting PQR | Prequalified — no PQR required (AWS D1.1 Clause 5) |
| Welding Process | GMAW — Semiautomatic |
| Base Metal | ASTM A36, Group I per AWS D1.1 Table 5.3 |
| Base Metal Thickness | Min 3/16" (4.8mm) — Max unlimited (groove with backing) |
| Joint Type | Single-V groove butt weld, steel backing (TC-U4a per AWS D1.1 Fig. 5.1) |
| Groove Angle | 45° included (22.5° per side) |
| Root Opening | 0 – 1/4" (0 – 6.4mm) |
| Root Face | 0 – 1/8" (0 – 3.2mm) |
| Backing | Steel bar, min 3/8" × 1-1/2" |
| Welding Position | 1G — flat groove (ANSI/AWS A3.0) |
| Filler Metal | AWS A5.18, ER70S-6 — F-Number: F6 — A-Number: A1 |
| Wire Diameter | 0.045" (1.2mm) |
| Shielding Gas | 75% Ar / 25% CO₂ (C25) — 40–45 CFH |
| CTWD (nozzle-to-work) | 5/8" – 3/4" |
| Current Type / Polarity | DCEP (electrode positive) |
| Root Pass — Amperage | 220 – 260 A |
| Root Pass — Voltage | 22 – 26 V |
| Root Pass — WFS | 280 – 350 ipm |
| Fill/Cap Pass — Amperage | 240 – 290 A |
| Fill/Cap Pass — Voltage | 24 – 28 V |
| Fill/Cap Pass — WFS | 310 – 400 ipm |
| Travel Speed | 12 – 18 ipm |
| Min. Preheat (≤ 3/4" thick) | 32°F (ambient) |
| Min. Preheat (> 3/4" thick) | 150°F (65°C) |
| Min. Preheat (> 1-1/2" thick) | 225°F (107°C) |
| Max. Interpass Temperature | 550°F (288°C) |
| Post-Weld Heat Treatment | None required |
| Heat Input (approx.) | 22 – 44 kJ/in — verify per pass using H=(E×I×60)/(S×1,000) |
| Technique | Stringer beads; slight weave (max 3× electrode diameter) permitted for cap pass |
| Interpass Cleaning | Wire brush or grinder between passes; remove all spatter |
| Governing Code | AWS D1.1/D1.1M:2020 Structural Welding Code — Steel |
At 250A / 25V / 15 ipm: H = (25 × 250 × 60) / (15 × 1,000) = 25 kJ/in. AWS D1.1 doesn't set a mandatory heat input ceiling for prequalified procedures on A36, but document it — heat input records matter for HSLA steels and any CVN-tested application.
A qualified WPS without a valid supporting PQR is unenforceable. The PQR must have been witnessed, the test coupons must have passed required mechanical tests, and the WPS variables must stay within the qualified ranges. If you can't produce the PQR, the WPS has no legs. Inspectors ask for it.
H = (E × I × 60) / (S × 1,000) — E in volts, I in amps, S in inches per minute. A common error: using wire feed speed instead of travel speed for S. Wire feed speed is not the same as torch travel speed. Another: using seconds in the denominator instead of minutes, giving a value 60× too low.
AWS D1.1 Table 5.8 sets minimum preheat by material group AND thickness. A36 under 3/4" requires only ambient temperature; A36 over 1-1/2" requires 225°F. Wrong preheat on thick plate leads to hydrogen cracking in the heat-affected zone — a real failure mode, not just a paperwork problem.
GTAW (TIG) is NOT a prequalified process under AWS D1.1 for structural steel. It requires full procedure qualification with PQR and destructive testing. This surprises welders coming from ASME or pipe work. If you need a GTAW WPS for structural steel, budget for test coupons and a certified testing lab.
A WPS qualified in flat position (1G) does NOT automatically qualify vertical (3G) or overhead (4G) welding. Each position is a separate essential variable. Vertical and overhead positions require different parameter windows — typically lower amperage and voltage to control the puddle against gravity.
IronKit's WPS Generator builds AWS D1.1-formatted welding procedure specifications from a short form. Select your process, base metal, filler, and position — get a print-ready WPS document you can put in your welder's hand tonight.
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