Can I use my AWS D1.1 WPS on structural stainless steel?

No. Structural stainless welding is governed by AWS D1.6, not D1.1. The preheat, interpass, essential variable, and filler metal rules are different. A WPS qualified under D1.1 is not valid for stainless structural members.

When does AWS D1.5 apply instead of D1.1 for bridge work?

AWS D1.5 (the AASHTO/AWS Bridge Welding Code) governs welding on highway bridges built with federal-aid funds. It is more stringent than D1.1 in several areas including CVN requirements and NDE. Projects that are not federally funded highway bridges typically use D1.1 unless the contract specifies otherwise.

Does ASME Section IX replace AWS D1.1 for structural steel?

No. ASME Section IX applies to pressure boundary welds — pressure vessels, boilers, process piping (ASME B31.3). Structural steel members, even in industrial plants, use AWS D1.1. A structural support frame holding a pressure vessel uses D1.1 for the frame, ASME IX for the vessel itself.

Which code applies to welding A706 rebar to structural steel plates?

This is a mixed-code situation. The rebar qualification falls under AWS D1.4; any structural steel member involved falls under D1.1. The connection details and the WPS must satisfy both applicable standards. Many structural engineers specify a dual-code qualification in this scenario.

Jun 21, 20266 min read

Which AWS D1 welding code applies to your project?

AWS D1.1 is not the only structural welding standard. This guide walks through D1.1 through D1.9 and related codes so fab shops pick the right standard before writing a WPS.

AWS D1.1 WPS Code Selection ASME IX AWS D1.6

New to procedures? Start with WPS welding: what a welding procedure specification is, with a filled-in example.

A new project arrives and the drawings say "welding per AWS standards." That phrase covers a lot of ground. The AWS D1 family has nine published standards, and using the wrong one invalidates your WPS library, your welder qualifications, and potentially the whole NDE program.

Choosing the right code is not a paperwork formality — it determines everything from your PQR test requirements and essential variables to your NDE sampling rates and filler metal restrictions. Here is how to match base metal and application to the correct AWS D1 standard before you write a single line on a WPS form.

AWS D1.1 — Structural Carbon and Low-Alloy Steel

AWS D1.1 is the default structural welding code for carbon and low-alloy steel in buildings, industrial structures, bridges under certain contracts, and general fabrication. It covers base metals including ASTM A36, A572 (grades 42–65), A992, A913, A514, A709, A588, and many others that appear on prequalified base metal tables.

D1.1 applies when the structural engineer of record specifies it, when the contract requires it, or when no other more specific code applies to the material and application.

D1.1 does not apply to:

Pressure boundary components (vessels, piping)
Aluminum
Sheet steel thinner than 1/8" in most applications
Reinforcing bar
Structural stainless steel

If your project uses structural carbon steel and there is no more specific code requirement, D1.1 is your standard.

AWS D1.2 — Aluminum Structures

AWS D1.2 covers structural welded aluminum. The filler metal system (AWS A5.10), preheat requirements (typically none — but interpass control matters), and joint design tables are completely different from D1.1. A shop qualified under D1.1 for structural steel must run separate PQRs under D1.2 to work on structural aluminum.

Common applications: lightweight structures, transportation equipment, marine structural components, sign bridges, bleachers, and architectural elements in aluminum.

AWS D1.3 — Sheet Steel

AWS D1.3 covers arc welding of sheet steel with thicknesses typically under 3/16" (4.8 mm) — the cold-formed, light-gauge material used in metal building systems, decking, HVAC ductwork, and light-framing connections.

The prequalified joints in D1.3 are optimized for thin material where burn-through is the main failure mode. AWS D1.1 is not appropriate for sheet steel; the heat input, joint geometries, and acceptance criteria are calibrated for plate, not sheet.

AWS D1.4 — Reinforcing Steel

AWS D1.4 governs welded splices of reinforcing steel (rebar). Weldable rebar is ASTM A706; welding of A615 is permitted but requires special PQR controls because of its higher carbon equivalent. The code covers butt splices, lap splices, and welded connections of rebar to structural steel.

When a project requires welding rebar to structural plate — a common embed detail in concrete construction — you are in a dual-code situation: D1.4 for the rebar connection, D1.1 for the structural plate side. Structural drawings should specify which code applies to each element; if they don't, ask the engineer of record in writing before qualifying procedures.

AWS D1.5 — Bridge Welding

AWS D1.5 is the AASHTO/AWS Bridge Welding Code, developed jointly by the American Welding Society and the American Association of State Highway and Transportation Officials. It applies to steel highway bridges constructed with federal-aid funds.

D1.5 is more stringent than D1.1 in several key areas:

CVN impact testing is required for many weld categories (not optional as it often is under D1.1)
NDE sampling rates are higher
Some process restrictions are tighter
Radiographic testing for CJP groove welds is more broadly required

For state-funded bridges that don't invoke federal requirements, confirm with the contracting authority whether D1.5 or D1.1 applies. Some state DOTs have their own supplementary specifications that modify D1.5 further.

AWS D1.6 — Structural Stainless Steel

AWS D1.6 governs structural welding of stainless steel: austenitic (304, 316), duplex, ferritic, and martensitic grades. Stainless welding under D1.6 has fundamentally different essential variables from D1.1 — filler metal selection, preheat (often prohibited or very low), interpass temperature ceiling, and heat input control all differ because stainless has far lower thermal conductivity and a greater sensitization risk from carbide precipitation.

A D1.1-qualified WPS for carbon steel is not valid for stainless. See welding stainless structural members under AWS D1.6 for the practical differences.

Common D1.6 applications: chemical plant structural supports, food-processing facility framing, ornamental and architectural structural elements, pulp and paper equipment supports.

AWS D1.7 — Strengthening and Repairing Existing Structures

D1.7 is a supplemental document — it is used alongside D1.1, not instead of it. It addresses the unique concerns of welding on existing structures: unknown or variable base metal chemistry, existing stress states, limited access, and the need to qualify procedures on material that cannot be destructively sampled.

If your project involves weld repair or structural strengthening of an existing steel building or bridge component, D1.7 provides the supplemental guidance for that work. D1.1 remains the baseline code for the weld procedure and qualification requirements.

See AWS D1.1 requirements for welding on existing structures for the Clause 8 provisions that apply to existing-structure work under D1.1.

AWS D1.8 — Seismic Supplement

AWS D1.8 is another supplement to D1.1. It applies to structural steel welding in seismic-force-resisting systems — special moment frames, eccentrically braced frames, special concentrically braced frames — wherever AISC 341 (Seismic Provisions) is invoked.

D1.8 adds CVN requirements for demand-critical welds, additional WPS restrictions, supplemental weld tabs removal requirements, and inspection requirements beyond D1.1 baseline. Any project in a seismic zone where AISC 341 applies should be reviewed for D1.8 requirements before the WPS program is built.

AWS D1.9 — Titanium

D1.9 covers structural welding of titanium. A niche standard used primarily in aerospace, chemical processing, and offshore. Most structural fab shops will not encounter it.

API 1104 — Pipeline Welding

API 1104 is not an AWS D1 standard, but it is often compared to D1.1 in the field. It governs welding of oil and gas transmission pipelines — specifically girth welds on steel pipe. The essential variable structure, qualification test requirements, and acceptance criteria are completely different from D1.1. A welder qualified under D1.1 is not automatically qualified under API 1104, and vice versa. See API 1104 vs AWS D1.1 WPS differences for a detailed comparison.

ASME Section IX — Pressure Vessels and Piping

ASME Section IX covers welding of pressure-boundary components: ASME pressure vessels (Division 1 and 2), ASME B31.3 process piping, B31.1 power piping, and boilers. When a structural support frame sits under a pressure vessel in an industrial plant, the frame is D1.1 and the vessel is ASME IX.

The most common field confusion: a maintenance weld on process piping is ASME IX territory regardless of where it is located. A weld on the structural steel rack holding that pipe is D1.1. This is explained in more detail in AWS D1.1 vs ASME Section IX — when each code applies.

Code selection decision framework

Run through this list before writing the first WPS:

Aluminum? → AWS D1.2
Sheet steel under 3/16"? → AWS D1.3
Reinforcing bar? → AWS D1.4 (plus D1.1 if structural steel is also involved)
Highway bridge with federal funding? → AWS D1.5 (AASHTO/AWS)
Structural stainless? → AWS D1.6
Repair or strengthening of existing steel structure? → D1.1 + D1.7
Seismic-force-resisting system per AISC 341? → D1.1 + D1.8
Pressure vessel or process piping? → ASME Section IX (not D1.1)
Pipeline girth weld? → API 1104
Carbon or low-alloy structural steel, none of the above? → AWS D1.1

When in doubt, read the contract documents. The structural specifications section will name the governing welding standard. If the specs are silent, the material drives the decision and D1.1 is the default for structural carbon steel.

Misapplied code is one of the top findings in third-party fabrication audits — particularly when a shop carries over WPS documents from a D1.1 project and applies them to stainless, sheet metal, or rebar work without re-qualifying. WPS management software that tags each procedure with its governing code standard and alerts when a welder picks a mismatched WPS for a material is one way to prevent that category of error. See how WPS software addresses this and other audit findings.

Rule library based on AWS D1.1:2025; verify against your governing edition.

FAQ

Frequently asked.

Can I use my AWS D1.1 WPS on structural stainless steel?: No. Structural stainless welding is governed by AWS D1.6, not D1.1. The preheat, interpass, essential variable, and filler metal rules are different. A WPS qualified under D1.1 is not valid for stainless structural members.
When does AWS D1.5 apply instead of D1.1 for bridge work?: AWS D1.5 (the AASHTO/AWS Bridge Welding Code) governs welding on highway bridges built with federal-aid funds. It is more stringent than D1.1 in several areas including CVN requirements and NDE. Projects that are not federally funded highway bridges typically use D1.1 unless the contract specifies otherwise.
Does ASME Section IX replace AWS D1.1 for structural steel?: No. ASME Section IX applies to pressure boundary welds — pressure vessels, boilers, process piping (ASME B31.3). Structural steel members, even in industrial plants, use AWS D1.1. A structural support frame holding a pressure vessel uses D1.1 for the frame, ASME IX for the vessel itself.
Which code applies to welding A706 rebar to structural steel plates?: This is a mixed-code situation. The rebar qualification falls under AWS D1.4; any structural steel member involved falls under D1.1. The connection details and the WPS must satisfy both applicable standards. Many structural engineers specify a dual-code qualification in this scenario.