Temperature review · Table 5.11
How do you find the minimum preheat for a two-member joint?
Identify each member’s Table 5.11 preheat category from its listed material and process condition, use the thickest part at the point of welding for the thickness band, then apply the higher side-specific minimum. Table 5.6 strength groups answer a separate filler-matching question.
A practical workflow for the actual joint
- Confirm identity on both sides. From material certificates or controlled project records, record each ASTM/API specification, grade or class, product form and applicable thickness condition. Do not treat a steel family name or yield strength as a substitute for the listed grade.
- Keep the strength-group check separate. If the WPS is intended to be prequalified, map each member to Table 5.6 and retain any grade, product-form or thickness restriction. Use those Groups I–V for the applicable filler-metal matching check; do not use them to select preheat.
- Determine each Table 5.11 category. Match each member to its listed category and the welding process/electrode condition. For example, GMAW uses the ordinary listed process condition in Categories B or C, depending on the steel entry. A different process or SMAW electrode condition may use another category.
- Measure thickness where the weld is made. Enter the thickest joined member at that point—not the weld size or a thicker remote section. Select the applicable SI or US customary table column and its printed band boundaries.
- Read both minima and govern by the higher one. AWS 5.7.2 applies the highest minimum where the two base metals have different Table 5.11 requirements. Do not average categories or temperatures.
- Apply additional conditions. Check the table notes, initial temperature, any qualifying hydrogen-based category, project minimum, separate maximum interpass limit, material-specific cap and the contract edition before writing the WPS.
The AWS D1.1 preheat calculator compares supported material/process choices on both sides and reports the governing value. It applies SI and US table columns independently. The result does not establish Table 5.6 eligibility or complete WPS qualification; confirm those separately.
Worked example: A572 Grade 50 joined to Grade 60
Consider a GMAW joint between ASTM A572 Grade 50, 12 mm thick, and ASTM A572 Grade 60, 25 mm thick. Assume the stated grades are verified, the contract uses the 2025 base edition, there is no documented reduced-hydrogen route, the starting temperature is at least 0°C, and no project minimum raises the result.
| Member | Table 5.6 strength group | Table 5.11 GMAW category | Minimum at 25 mm |
|---|---|---|---|
| A572 Grade 50, 12 mm | Group II | Category B | 10°C |
| A572 Grade 60, 25 mm | Group III | Category C | 65°C |
The 25 mm Grade 60 member is the thickest part at the point of welding, so use the >20 through 38 mm band for the joint’s Table 5.11 checks. Category B calls for 10°C and Category C calls for 65°C in that band; the higher minimum governs. The Table 5.6 groups (II and III) are recorded separately for the filler matching review. They are not the reason the 65°C preheat applies.
Enter both A572 grades, GMAW, 25 mm and the actual starting temperature in the calculator to reproduce the supported temperature check. The example is bounded to these stated assumptions; it is not a complete WPS or confirmation that all Clause 5 conditions are met.
Details that can change the result
- Material identity: Table 5.11 includes grade-specific entries. For instance, A572 Grade 50 is listed in Category B, while Grades 60 and 65 are in Category C for the stated ordinary process condition. Do not assign a category to an unlisted grade by similarity.
- Process and consumable condition: SMAW with non-low-hydrogen electrodes can follow a different row from low-hydrogen SMAW, SAW, GMAW or FCAW. GMAW-S is not a Clause 5 prequalified process; a preheat calculation alone does not qualify it.
- Hydrogen-based lower categories: Categories D–G require their listed material and process conditions and documented qualifying diffusible-hydrogen evidence at the specified limit. An electrode name or normal handling practice is not that test evidence.
- Initial temperature and project limits: A marked freezing-point cell can invoke a 20°C/70°F minimum when the base metal starts below 0°C/32°F. A project minimum may increase the temperature. A maximum interpass limit is separate and can conflict with the minimum.
- Alternative methods: Annex B and the special Engineer-approved multi-electrode SAW path have their own inputs and conditions. Do not replace Table 5.11 with a carbon-equivalent estimate or assumed reduction.
Basis and scope
This page uses AWS D1.1/D1.1M:2025 base edition plus the registered July 28, 2026 base-edition errata; AMD1 is excluded. Contract-specified editions govern. Relevant provisions are Table 5.6, Table 5.11 and Clauses 5.7 and 7.6, including applicable notes. For an existing-PQR WPS, use its applicable qualification rules and the actual record instead of assuming a new Clause 5 path.
Scope limit: The worked calculation establishes only the stated Table 5.11 minimum under its assumptions. It does not establish weld design, complete prequalification, PQR coverage, production settings or project approval.