Can one WPS cover welding A36 to A572 Grade 50?

Yes, if the WPS was qualified using PQR test welds that cover both base metals. AWS D1.1 groups base metals by similar metallurgical and mechanical characteristics; a PQR on one material covers similar materials within the same group. A36 and A572 Gr. 50 often fall within the same or adjacent groups for prequalified joint purposes.

What filler metal do I use when joining two different steel grades?

AWS D1.1:2025 requires filler metal that meets the mechanical properties of the higher-strength base metal in the joint, or that is compatible with both. For most structural combinations, a matching filler to the stronger member (e.g., E7018 for A572 Gr. 50 side) is the starting point; the CWI or EOR should confirm the selection.

Does joining dissimilar steels require a separate PQR?

Not always. AWS D1.1 base metal groupings allow a PQR on one steel to cover a range of similar steels. If both steels in the joint fall within the covered range, an existing PQR may suffice. If one steel is outside the qualification range—for example, a high-strength alloy steel joined to A36—a new PQR is required.

Do I need a separate WPS for each dissimilar metal combination on a project?

In practice, most structural projects can be served by two or three WPS documents that address the most common combinations through broad PQR coverage, rather than one WPS per joint type. Proper procedure scoping at the start of a project avoids qualification gaps discovered during inspection.

WPS for Dissimilar Base Metal Joints Under AWS D1.1

How AWS D1.1:2025 governs WPS qualification when joining different ASTM steel grades: base metal grouping, filler metal selection, PQR coverage rules, and common field scenarios.

Structural steel projects rarely use one grade of steel throughout. A typical building frame might combine A992 wide-flange columns and beams with A500 HSS bracing, A36 base plates and shear tabs, and A572 Grade 50 gusset plates. Each of those joints—column to base plate, beam to gusset, brace to connection plate—potentially joins two different ASTM steel specifications. AWS D1.1:2025 addresses dissimilar base metal welding, but the rules require careful reading to apply them correctly in procedure qualification.

Rule library based on AWS D1.1:2025; verify against your governing edition (the AHJ or contract may specify 2020 or earlier).

How AWS D1.1 Groups Base Metals

AWS D1.1 does not require a separate PQR for every possible pair of ASTM specifications. Instead, the code groups steels by similar metallurgical and mechanical characteristics. A PQR test weld on one steel within a group qualifies procedures for other steels in the same group, and in many cases for adjacent groups with lower strength.

The groupings are based primarily on:

Minimum specified tensile strength
Carbon equivalent and hardenability
Process compatibility (which welding processes can achieve proper fusion without cracking)

For the most common structural steels—A36, A53, A500 grades, A572 grades, A992, A588, A709 Grade 50—the groupings are deliberately broad to allow procedure reuse across projects. A fabricator that has qualified procedures for A572 Grade 50 typically has those procedures covering A992, A36, and similar steels without additional test welds.

High-strength and specialty steels break out of those broad groupings: A514, A517, A709 Grade HPS70W, and other quenched-or-tempered grades each have tighter groupings or are excluded from cross-qualification.

Filler Metal Selection for Mixed-Grade Joints

When two steels of different specified minimum tensile strength (SMTS) are joined, the general rule in AWS D1.1:2025 is to select a filler metal whose deposited weld metal mechanical properties meet or exceed the requirements of the lower-strength base metal—but that is also compatible with the higher-strength base metal to avoid hot cracking or incomplete fusion.

In most structural combinations, this is straightforward:

A36 to A572 Grade 50: An E70XX electrode is correct. The weld metal at 70 ksi tensile strength overmatches A36 (58–80 ksi SMTS) and is appropriate for A572 Gr. 50 (65–100 ksi SMTS). Using an E60XX on this joint would understrength the A572 side.
A572 Grade 50 to A992: Both have similar SMTS and comparable weldability. E70XX filler works for both; no special considerations unless CVN toughness is specified.
A36 to A514: This is where it gets careful. A514 has a SMTS of 110–130 ksi depending on thickness. Matching filler for A514 (E110XX or similar) is typically not appropriate for the A36 side because the weld would be significantly harder and more brittle than the A36 base metal. The standard approach is to use an intermediate filler—often E90XX or E100XX—and confirm with the engineer of record. The WPS must be qualified by test, not prequalified.

The selection principle is to avoid a mismatch in either direction: a filler much weaker than the stronger base metal creates an understrength interface; a filler much stronger than the weaker base metal creates a hard, brittle weld metal that can crack or cause the base metal to fail adjacent to the weld rather than in the intended failure mode.

For filler metal classification details, the essential variables article on filler metal covers how filler specification changes trigger requalification under Table 6.6.

Which PQR Covers Which Combination

AWS D1.1:2025 qualification coverage for base metals follows a hierarchy:

Same base metal, same group: A PQR test on A572 Gr. 50 covers production WPS use on A572 Gr. 50 (and other steels in the same group).
Higher-strength test covers lower-strength production: A PQR test weld on A572 Gr. 50 (65 ksi SMTS minimum) typically covers production use on A36 (58 ksi SMTS minimum) within the same or lower group because the higher-strength material presents the more demanding qualification condition.
Lower-strength test does not cover higher-strength production: A PQR on A36 does not automatically extend to A572 Gr. 65 or higher grades where base metal composition and microstructural response to welding differ.

For dissimilar combinations where the two base metals are in adjacent or related groups, a PQR test weld using one of the two materials may cover the combination—provided the filler metal is appropriate for both. Documenting this coverage mapping is part of the CWI's responsibility when reviewing a WPS package for a multi-material project.

When the combination is genuinely novel—a high-alloy steel to a common carbon steel, or two steels from distant groups—a dedicated PQR test weld on the actual combination of materials is the clean approach. It eliminates ambiguity about coverage and gives the inspector a defensible record.

Prequalified Joints and Dissimilar Base Metal

For prequalified WPS, AWS D1.1 restricts base metal to the approved prequalified list. Both base metals in a prequalified joint must be on that list. A joint between A572 Grade 50 (on the prequalified list) and a proprietary HSLA grade not listed in AWS D1.1 Clause 4.2 cannot be prequalified—even if the HSLA grade has similar chemistry—because it has not been validated for the prequalified provisions.

This is a common source of procedure gaps on projects involving imported or specialty steels that are not ASTM-standard grades. If the structural drawings call for a steel not listed in AWS D1.1 Clause 4.2, a PQR-backed WPS is required for every joint involving that steel.

Common Dissimilar Metal Scenarios in Structural Practice

Column (A992) to base plate (A36): A992 and A36 are both on the prequalified list and in compatible groups. A standard E70XX prequalified procedure covers this combination. The filler selection (E70XX) overmatches A36 and is consistent with A992 requirements. No PQR needed for a prequalified joint geometry.

HSS brace (A500 Grade C) to gusset (A36 or A572 Gr. 50): A500 Grade C is not on the AWS D1.1 prequalified base metal list by default in many editions—check your governing edition's Clause 4.2 list. If A500 Grade C is on the list, a prequalified procedure on a standard groove or fillet joint geometry works. If not listed, a PQR is required. AWS D1.1:2025 expanded the prequalified base metal list relative to prior editions; confirm A500 Grade C's current status against the 2025 edition.

Stainless steel overlay or dissimilar weld (stainless to carbon steel): AWS D1.1 does not govern stainless-to-carbon steel dissimilar welds. AWS D1.6 covers stainless structural welding. A dissimilar joint between carbon steel and austenitic stainless steel requires procedures qualified under the applicable stainless code, typically using Alloy 309 or 309L filler metal, which bridges the carbon-to-stainless interface without excessive dilution.

A588 weathering steel to A572 Grade 50: A588 (Cor-Ten) is on the prequalified list and in a compatible group with A572 Gr. 50. The primary consideration is filler metal: to maintain the weathering characteristics of the joint, a matching weathering-grade filler (such as E8018-W2 for SMAW) is typically specified. A standard E70XX filler produces a non-matching weld that will not patina to match the base metal. The WPS must specify the filler accordingly.

Documenting the WPS for Dissimilar Joints

A WPS covering dissimilar base metals should explicitly list both base metal specifications in the procedure document, not just one. The qualification range must reference a PQR that covers both materials, or document the code rationale for cross-group coverage. A WPS that says "A36" in the base metal field but is being used on a joint between A36 and A572 Gr. 50 may technically be adequate if the PQR coverage supports it—but an inspector seeing only "A36" on the WPS has no way to confirm that without digging through the PQR package.

The better practice is to write the WPS base metal field to reflect the full covered range. For example: "Base Metal: ASTM A36, A572 Gr. 50, A992, and other similar structural steels per AWS D1.1:2025 Table 4.9 group coverage."

For the inspection side—how the CWI reviews a WPS package for a multi-grade project before the first arc is struck—see the WPS submittal package checklist for EOR review, which walks through the sign-off process from the owner's engineer's perspective.

Base Metal Records in the Audit File

When a fabricator's AISC certification audit covers welded connections between multiple steel grades, auditors look for a clean chain from base metal to WPS to PQR: the mill certificate confirms the base metal specification; the WPS specifies that material; the PQR covers that material. A gap anywhere in that chain—a PQR that doesn't clearly extend to one of the base metals in use—is a finding.

For projects with significant dissimilar metal work, mapping the base metals in use to the existing WPS/PQR library at the start of bidding prevents qualification gaps from appearing as inspection holds during fabrication. See the AISC fabrication certification audit readiness guide for the full pre-audit procedure review checklist.

Shops that want to manage procedure coverage across multiple steel grade combinations can explore how wpswelding.com/pricing supports WPS libraries with explicit base metal coverage mapping linked to PQR records.