WPS for Structural Steel Embed Plates Under AWS D1.1
Embed plates cast into concrete require AWS D1.1-compliant WPS for both shop fabrication and field welding. Here's what QC managers need to document and qualify.
Embed plates — steel plates cast into concrete slabs, walls, and columns to provide a weld-ready connection point for structural steel — show up on almost every commercial and industrial construction project. They're ubiquitous precisely because they're convenient: pour the plate in, let the concrete cure, then make the structural connection with a field weld rather than anchor bolts and baseplates.
But that convenience comes with a documentation obligation that many project teams underestimate. Every structural field weld to an embed plate must be covered by a qualifying WPS under AWS D1.1. If your project has special inspection, the inspector will ask for it.
What an Embed Plate WPS Must Cover
An embed plate connection involves two distinct welding scopes, and a QC manager who thinks only about one of them will miss the other.
Shop scope: anchors to plate. The embed plate typically has mechanical anchors — headed shear studs, hooked rebar, or Nelson-type studs — welded to the back face before the plate goes into the formwork. If those anchors are welded in the fabrication shop, the shop needs a WPS covering that process. Headed stud welding is governed by AWS D1.1 Clause 7 (stud welding), not the main WPS qualification framework. Rebar-to-plate welds fall under AWS D1.4 (structural welding of reinforcing steel) if the rebar is treated as a structural anchor, or AWS D1.1 if the connection is treated as a structural steel weld. Clarify with the EOR which standard governs each anchor type.
Field scope: structural steel to embed plate face. Once the concrete is placed and cured, the structural steel crew welds beams, columns, or plate brackets to the exposed face of the embed. This weld is a structural steel connection governed by AWS D1.1. It typically involves fillet welds or partial-penetration groove welds between the structural member and the embed plate. This is where a standard AWS D1.1 WPS is needed.
Base Metals Typically Involved
Embed plates are almost universally ASTM A36 or A572 Grade 50 carbon steel — prequalified base metals under AWS D1.1 Clause 5. The connecting structural members are also typically A36, A572, or A992 (wide-flange shapes). This combination is ideal for a prequalified WPS: both materials are in the prequalified base metal groups, well-characterized for low-hydrogen filler metal compatibility, and preheat requirements are straightforward based on carbon equivalent.
One exception worth noting: when the project engineer specifies corrosion-resistant embed plates (stainless steel or galvanized carbon steel in an exposed exterior application), the base metal match changes, and prequalified status may not apply. A galvanized embed plate welded with E7018 requires special attention — see weld-through primer and zinc-coated steel WPS requirements for the zinc fume and porosity concerns that apply.
Preheat Requirements for Field Embed Welds
AWS D1.1 preheat requirements for carbon steel depend on the base metal carbon equivalent and the combined thickness of the welded parts. For A36 or A572 Gr. 50 embed plates of typical thickness (3/8" to 3/4"), preheat requirements at ambient temperature are often zero or minimal — assuming low-hydrogen electrodes are used.
However, field embed connections present conditions that can push the effective preheat requirement upward:
Mass of the concrete. Concrete is a thermal sink. A plate cast into a concrete wall or slab conducts heat away from the weld zone rapidly — faster than a free-standing plate of the same dimensions. In cold-weather conditions, this thermal mass effect can increase the effective cooling rate significantly.
Concrete moisture. Freshly placed or rain-saturated concrete introduces moisture near the weld zone. Moisture can diffuse into the HAZ and increase hydrogen-induced cracking risk, particularly on thicker plates with higher restraint.
Restraint. An embed plate cast into concrete is essentially fully restrained — it cannot move to relieve weld shrinkage stress. High restraint increases cracking susceptibility.
Experienced CWIs on embed plate work often specify preheat 50°F [10°C] above the D1.1 minimum for the material and thickness combination, particularly in cold-weather conditions or on thick, high-restraint joints. Your WPS should address these field conditions explicitly, not just recite the table minimum.
Embed plate field welds are often made in difficult access conditions. The structural member being welded — a clip angle, a beam end, a plate bracket — may be tightly fitted to the embed surface with minimal gap. The welder may be working overhead, vertically, or in a corner where electrode angle is constrained.
Your WPS must be qualified for the actual welding position. A WPS qualified for flat (1F) fillet welding does not qualify overhead (4F) fillet welding. If the field condition requires overhead welding to the underside of an overhead embed, the WPS must be qualified in 4F position — and the welder must hold a WPQ that includes 4F.
The WPS should also address the minimum and maximum fillet weld size for the applicable plate thickness. AWS D1.1:2025 Table 7.7 specifies minimum fillet weld sizes based on a governing thickness T: the thinner part joined for low-hydrogen processes, or the thicker part for non-low-hydrogen processes without 6.8.4 preheat (Table 7.7 note a). For a 3/4" embed plate with a 1/2" clip angle welded with a low-hydrogen process, T is the 1/2" angle and the minimum fillet is 3/16"; with a non-low-hydrogen electrode and no 6.8.4 preheat, T is the 3/4" plate and the minimum rises to 1/4" in a single pass. Undersized fillet welds on embed connections are a recurring finding in special inspection reports.
Prequalified vs. Tested WPS
Most embed plate field welds qualify for a prequalified WPS under AWS D1.1 Clause 5:
A36/A572 base metals (prequalified group)
SMAW with E7018 or E7016 electrodes (prequalified process and filler)
Standard fillet or PJP groove geometry (prequalified joint types)
Process parameters within Clause 5 limits
If any of those conditions are not met — unusual base metal, unconventional joint geometry, FCAW-S process, or a connection geometry that doesn't fit a prequalified joint detail — a tested WPS with PQR is required. Don't assume "it's just a simple fillet weld" automatically puts you in prequalified territory. Read Clause 5 carefully for each condition.
A common project-management error is issuing a WPS for embed welding but not verifying that field welders hold WPQ documentation covering the required positions and processes. For embed fillet welds in the vertical position (3F), the welder must hold a WPQ that covers 3F — a WPQ tested only in flat (1F) or horizontal (2F) does not cover vertical.
Welder continuity is a parallel concern: AWS D1.1 Clause 6.4.1 requires that a welder who has not used a process in the preceding six months must re-qualify. If embed welding is intermittent work — a crew that spends most of its time on steel erection and makes embed welds only occasionally — their continuity records need active monitoring.
Embed plate field welds on most commercial and public construction projects fall under IBC Chapter 17 special inspection requirements. The special inspector will verify:
WPS is available at the point of work and covers the joint being welded
Welder WPQ documentation is current
Preheat is verified before arc start
Fillet weld size is verified visually after completion
Any NDE specified on the contract drawings is performed
If the project drawings call for MT or PT on embed weld toes — sometimes required at moment-frame embed connections or embed plates with large imposed loads — the NDE procedure and acceptance criteria must be available and the NDE technician must be qualified per the applicable standard.
Documentation from the special inspector feeds into the project's closeout package and may be required for building permit closeout or certificate of occupancy. A missing WPS or outdated WPQ that holds up a closeout is a common and avoidable problem.
Before the field crew strikes the first arc on an embed plate connection:
WPS covering the process, joint type, position, base metals, filler metal, and preheat
Welder WPQ documentation current and covering the required position
Welder continuity verified (no 6-month lapse per Clause 6.4.1)
Preheat method and measurement documented
Minimum fillet weld size confirmed against AWS D1.1 Table 7.7
Special inspection hold points identified per project ITP
Getting this documentation in order before mobilization — not the morning the crew shows up — is the difference between smooth embed work and a field RFI spiral.
Rule library based on AWS D1.1:2025; verify against your governing edition. The AHJ or contract may specify 2020 or an earlier edition. Stud welding for embed anchors is governed by AWS D1.1 Clause 7; rebar anchor welding is governed by AWS D1.4.
FAQ
Frequently asked.
Do embed plates require an AWS D1.1 WPS?
Yes, when the field weld connecting steel members to the embed is structural. If the embed plate and its anchors are fabricated in a shop (headed studs or rebar welded to the plate), the shop must have a WPS covering those weld types. Field welders connecting steel to the embed face also need a WPS qualified for the joint geometry, process, and base metals involved.
What process is most common for field welding to embed plates?
SMAW (shielded metal arc welding) with low-hydrogen E7018 electrodes is the most common field process for embed connections. FCAW-G is also used on larger projects with fixed field welding stations. The WPS must address the field position (typically 2F, 3F fillet or 1G/2G groove), preheat, and electrode handling requirements.
Who is responsible for the embed plate WPS — the structural fabricator or the concrete subcontractor?
Usually the structural fabricator owns the WPS for field welding to embeds because the connection is structural steel work. The concrete sub handles embed installation in the formwork; once the slab or wall is poured, a structural steel crew performs the field weld. The EOR specifies the weld, and the structural fab shop or steel erector must provide a qualifying WPS and qualified welders.
Can a prequalified WPS cover embed plate field welds?
Often yes, if the joint geometry, base metals, process, filler metal, and parameters all satisfy AWS D1.1 Clause 5 prequalified requirements. Most embed connections are fillet welds or simple PJP grooves on A36 or A572 Gr. 50 plate — prime territory for a prequalified WPS. A tested WPS is needed when the geometry, material, or conditions fall outside Clause 5 scope.