Two-member decision · AWS D1.1 Clause 5
How do you check a WPS for dissimilar structural steels?
Treat each member as a separate material input. Confirm its exact specification, grade and condition; map both Table 5.6 strength groups; apply the mixed-group filler rule; then determine each Table 5.11 temperature category and use the higher applicable minimum at the point of welding.
Keep both sides visible in the review
| Decision | Member 1 | Member 2 | Joint result |
|---|---|---|---|
| Identity | Actual specification, grade, product condition and thickness | Actual specification, grade, product condition and thickness | Verify both against the project record; do not infer identity from a trade name. |
| Table 5.6 group | Exact row and any thickness/product restriction | Exact row and any thickness/product restriction | Use the group pair for Table 5.7 filler matching; preserve any qualifying footnote. |
| Table 5.11 category | Material plus process/electrode condition | Material plus process/electrode condition | Use the thickest part at the weld for both lookups, then the higher applicable minimum. |
| Remaining procedure | Process, filler product, joint detail, position, thickness and project restrictions | Only a complete applicable Clause 5 check can establish a prequalified route. | |
The base-metal lookup helps identify curated Table 5.6 rows, and the preheat calculator compares supported Table 5.11 inputs. Neither result alone qualifies the joint.
The mixed-group filler decision
Under the base-edition Table 5.6 notes and Clause 5.6.1, the stated mixed-group option is a filler matching the higher-strength group, or a lower-group matching filler with low-hydrogen deposited weld metal. That is a classification route, not a product approval. The actual process, complete classification, consumable product, gas or flux, position, manufacturer operating conditions and project requirements still must fit.
Design matching or undermatching requirements are a separate check under the applicable design provision (including Table 4.3 or 10.2 where relevant). Do not choose the lower-strength option merely because it appears in a filler table. Use the filler-metal selector only after both material groups are confirmed.
Bounded example: A36 joined to A572 Grade 60
Consider a hypothetical GMAW joint between a verified 25 mm ASTM A36 member and a verified 12 mm ASTM A572 Grade 60 member. Use the code's SI column and assume the ordinary listed process route, starting temperature at least 0°C, no documented reduced-hydrogen alternative and no higher project minimum.
| Member | Table 5.6 strength group | Table 5.11 GMAW category at 25 mm |
|---|---|---|
| A36, 25 mm | Group II: the Group I A36 listing ends at 20 mm | Category B: 10°C |
| A572 Grade 60, 12 mm | Group III | Category C: 65°C |
For the filler review, the group pair is II–III; check the Table 5.7 route and the mixed-group rule, then verify design matching and the actual product. For temperature, use the 25 mm thickest part at the weld for both category lookups; the higher stated minimum is 65°C. These results answer only the material/filler-group and bounded preheat questions. Joint geometry, process settings and complete prequalification still need review.
If the route is based on an existing PQR
Do not use the Clause 5 mixed-group shortcut as a replacement for Clause 6 qualification coverage. Record the PQR's actual coupon material combination and compare it with the target pair under the applicable qualification table and notes. A PQR for A36 with A36, plus another for A572 with A572, does not by itself prove a procedure for A36 joined to A572.
Use the PQR coverage matrix to keep the test combination, governing rule, supported target and unresolved conditions separate. The existing-PQR WPS route requires the genuine record and supporting test reports.
Basis and scope
This guide uses AWS D1.1/D1.1M:2025 base edition plus the registered July 28, 2026 base-edition errata; AMD1 is excluded. The relevant sources are Clause 5.3, 5.6.1 and 5.7.2, Tables 5.6, 5.7 and 5.11 with their notes, and the applicable Clause 6 material-combination rules for a PQR route. The project contract's edition governs. The example is a method illustration, not a finished WPS or a declaration that an actual joint qualifies.
Submit both material records, the actual joint and the governing contract conditions.