Prequalified Base Metal Eligibility: What Table 5.6 Really Means
AWS D1.1 Table 5.6 prequalified base metals: composition limits, Group I and II classifications, and what CWIs and QC managers do when a structural steel falls outside the list.
When a fab shop says a welding procedure is "prequalified," what that means under AWS D1.1 is that the procedure meets all the conditions in Clause 5—including using only base metals listed in Table 5.6. Table 5.6 is not a registry of every weldable structural steel; it is a curated list of steels whose properties are controlled tightly enough that procedure qualification testing can be skipped. Understanding why some steels are on the list and others are not helps QC managers and CWIs avoid the common error of treating a new material as prequalifiable when it is not.
What Table 5.6 Is—and Is Not
Table 5.6 in AWS D1.1:2025 lists specific ASTM specifications and grade combinations that are approved for prequalified WPS procedures under Clause 5. These steels have been determined to behave predictably under the preheat requirements stated elsewhere in the code and to produce heat-affected zones with acceptable mechanical properties when standard parameters are followed.
The table is not organized by chemistry ranges. It is organized by ASTM specification and grade. This matters because two heats of the same ASTM specification can have different chemistries within the ASTM-allowed composition window—and the variation can affect weldability, particularly hydrogen cracking susceptibility. Table 5.6 acceptance is based on the specification and grade, not the actual heat chemistry, which is why reading the mill test report (MTR) alongside the prequalified WPS is still good practice even for Table 5.6 steels.
Rule library based on AWS D1.1:2025; verify against your governing edition.
Group I and Group II in Table 5.6
Table 5.6 organizes prequalified base metals into groups, most commonly Group I and Group II. The groups matter because they determine when a single PQR can qualify welding to more than one base metal type:
Group I steels are typically lower-strength carbon steels with tightly controlled composition. Common Group I examples include ASTM A36 structural steel, A500 Grades B and C (hollow structural sections), and A53 Grade B pipe.
Group II steels are higher-strength carbon and high-strength low-alloy (HSLA) steels. Common Group II examples include ASTM A572 Grade 50, A992 wide flange steel, and A588 weathering steel. These steels have higher specified minimum yield strengths and often include alloying elements (manganese, vanadium, niobium, silicon) that improve strength and toughness but require more care in heat input and preheat selection.
For prequalified WPS purposes, a procedure written for a Group II base metal does not automatically extend to Group I—and vice versa. The relevant preheat requirements in Table 5.11 are organized by material category and base metal thickness, not simply by group. Check Table 5.11 for the minimum preheat requirements that apply to the specific steel and thickness combination you are welding.
Steels That Are Not on Table 5.6
Some high-strength and alloy steels commonly seen in structural applications are intentionally excluded from Table 5.6 because their composition and heat treatment produce HAZ behavior that needs testing to verify. Two notable examples:
ASTM A514: A quenched and tempered plate steel with a specified minimum yield of 100 ksi (690 MPa). A514's high alloy content—chromium, molybdenum, boron, and vanadium depending on the grade—creates a HAZ that is susceptible to hydrogen-assisted cracking and to softening from excessive heat input. A514 welding is governed by Table 6.10 provisions, requires a tested WPS under Clause 6, and mandates careful control of heat input, preheat, and filler metal hydrogen designation. See AWS D1.1 WPS for A514 and A517 Quenched and Tempered Steel for the full qualification requirements.
ASTM A252: Steel pipe piling. A252 is not listed in Table 5.6 and requires a tested WPS regardless of the welding process used. Shops that encounter A252 in foundation pile splicing work often discover this requirement only when an inspector asks for the PQR.
Foreign and specialty steels: Structural steel produced to CSA, EN, JIS, or other non-ASTM standards is generally not listed in Table 5.6. International fabricators working under AWS D1.1 for US-bound steel need a tested WPS for the foreign base metal unless a formal equivalency determination is made and accepted by the engineer of record. See Foreign Fabricator AWS D1.1 WPS and PQR Documentation Requirements for the qualification path.
The MTR Chemistry Check: Still Relevant for Table 5.6 Steels
Even for steels listed in Table 5.6, reading the mill test report before writing or approving a WPS adds useful information:
Carbon equivalent (CE): The IIW formula—CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15—gives a single number that correlates with cracking susceptibility and preheat demand. Two heats of A572 Grade 50 can produce CE values that differ meaningfully if the producer optimized one heat with more manganese and less carbon than the other. A heat with CE above 0.45 merits closer attention to preheat compliance than a heat at 0.38, even if both are nominally the same ASTM grade.
Sulfur and phosphorus (S and P): Higher sulfur content increases the risk of lamellar tearing under through-thickness loading in heavy restrained joints. The ASTM maximum is permissive; a heat at the high end of the ASTM S limit in a heavy T-connection should prompt a conversation with the EOR about Z-direction testing requirements.
Carbon at the high end of ASTM tolerance: A36 has a maximum carbon content that varies with product form and thickness. A heat of A36 plate at 0.25–0.26% C is technically compliant but represents higher weldability risk than a heat at 0.18% C. The prequalified preheat from Table 5.11 accounts for this range, but verifying that your preheat procedure actually reaches the required temperature (not just nominal temperature) matters more with high-CE heats.
If a project specifies a base metal not listed in Table 5.6, the fabricator must use a tested WPS under Clause 6. The qualification path involves:
Writing a preliminary WPS based on the unlisted material's known characteristics
Running a PQR test with the actual material from the project heat or a representative heat of the same specification
Conducting the mechanical tests required by Clause 6 (tensile, bend, and impact if CVN requirements apply)
Documenting the PQR and referencing it in the production WPS
The owner's engineer may specify additional requirements beyond Clause 6 minimums—supplemental CVN testing, hardness testing, or specific heat input limits—if the unlisted material has known susceptibility issues. See Unlisted Base Metal WPS Qualification Under AWS D1.1 for the complete qualification procedure.
Auditor Questions Around Table 5.6
In an AISC certification audit or third-party WPS review, the reviewer will verify that every base metal listed on a prequalified WPS appears in Table 5.6. Common findings:
A prequalified WPS lists A572 Grade 65 (not on Table 5.6) instead of Grade 50
A WPS lists an A500 grade or wall thickness combination that exceeds the prequalified limits
A project uses dual-certified A36/A572-50 plate and the WPS lists only A36, leaving the higher-yield heat without a supporting prequalified procedure
A straightforward practice: before a new WPS is issued, the QC manager checks the Table 5.6 column for every base metal combination listed. If any material is not in the table, the WPS gets rewritten as a Clause 6 tested procedure or the qualification testing is initiated before fabrication starts.
Digital WPS management systems that maintain a base metal reference database can flag Table 5.6 exceptions before the WPS is issued rather than after an audit finding. Visit our pricing page to see how a structured WPS platform supports prequalification compliance.
Summary
AWS D1.1 Table 5.6 defines which structural steels qualify for prequalified WPS procedures under Clause 5. The list is organized by ASTM specification and grade, with Group I covering lower-strength carbon steels like A36 and Group II covering higher-strength steels like A572 Grade 50, A992, and A588. Steels not on Table 5.6—including A514, A252, and most foreign specifications—require tested WPS procedures under Clause 6. Reading the MTR chemistry for CE and sulfur content adds a quality layer even for Table 5.6 steels, particularly in heavily restrained or high-fatigue connections where composition variation within ASTM limits can still matter.
FAQ
Frequently asked.
Which ASTM steels are prequalified under AWS D1.1 Table 5.6?
Common prequalified structural steels include ASTM A36 (Group I), A572 Grades 42 and 50 (Group II), A992 (Group II), A588 (Group II), A500 Grades B and C (Group I), and A53 Grade B (Group I), among others. A514 and A252 are not listed in Table 5.6 and require a tested WPS under Clause 6.
Why is ASTM A514 not prequalified under AWS D1.1?
A514 is a quenched and tempered high-strength steel with elevated alloy content that makes it susceptible to hydrogen-assisted cracking and heat-affected zone softening under standard preheat procedures. AWS D1.1 requires a tested WPS under Clause 6 and Table 6.10 provisions for A514. The procedure qualification test validates that the specific welding parameters produce acceptable mechanical properties.
What do the Group I and Group II designations in Table 5.6 mean?
The group designations reflect the base metal's strength and composition family. Group I covers lower-strength carbon steels (Fy typically 36–40 ksi) like A36. Group II covers higher-strength carbon and high-strength low-alloy steels (Fy typically 42–65 ksi) like A572 Gr 50, A992, and A588. The groups affect whether a single PQR can qualify welding to multiple base metal types.
Can a WPS for an unlisted base metal be written as prequalified?
No. Prequalified status under AWS D1.1 Clause 5 is available only for base metals listed in Table 5.6. Any steel not in Table 5.6 requires a tested WPS supported by a PQR under Clause 6. The owner's engineer may also require additional testing or approval for unlisted materials.