A588 Preheat for SAW — up to 3/4"
Per AWS D1.1:2025 Table 5.11, the minimum preheat for A588 welded with SAW at up to 3/4" is 32°F (0°C), Category B. Preheat below this raises hydrogen-cracking risk in the heat-affected zone; the same temperature is the minimum interpass limit maintained through the weld.
Built on AWS D1.1:2025 Table 5.11 — every value traced to the clause.
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SAW (Submerged Arc Welding)
SAW submerges the arc beneath granular flux for highest deposition rates, flat/horizontal only. Category B in Table 5.11.
SAW with F7A2-EM12K wire/flux delivers the highest deposition rates for flat-position fillet welds on building steel. Typical parameters: 500-700 amps, 28-32 volts, 18-30 IPM travel speed. Flux consumption runs approximately equal to wire consumption by weight. Unfused flux recovery and recycling systems are standard in production shops to control consumable costs.
SAW Tips for Common Structural Steels
For A588 weathering steel (50 ksi yield, CE-IIW 0.45–0.52), SAW with weathering-composition wire (EM12K-W or similar) and neutral flux handles girder web-to-flange fillet welds on unpainted bridge fabrication. The higher alloy content of A588 means the SAW heat input on thick flanges is a more critical parameter than on A36 — target 30–55 kJ/in to avoid excessive grain growth in the wide HAZ.
Typical values for reference — always verify against your approved WPS and electrode manufacturer data.
Filler Metal for SAW
Wire: EM12K or EL12 with matching flux (AWS A5.17). Common combo: F7A2-EM12K. Diameter: 3/32" or 7/64". AWS A5.17 Figure 1U uses A for as-welded and P for PWHT, not flux activity. Annex A6.1 defines active versus neutral flux by weld-metal Mn and Si change with arc voltage (Wall Neutrality Number); primary use of neutral fluxes is multipass welding and of active fluxes is single-pass welds. Voltage: 28-34V. Current: 400-800A depending on joint size. Travel: 12-24 ipm.
Typical values for reference — always verify against your approved WPS and electrode manufacturer data.
A588
ASTM A588 is a weathering steel specification (50 ksi minimum yield, 70 ksi minimum tensile) that forms a protective iron oxide patina when exposed to atmospheric wet-dry cycling. The copper (0.25-0.40%), chromium (0.40-0.65%), and nickel (0.25-0.40%) alloying creates a dense, adherent rust layer that stabilizes after 2-5 years of exposure. Used in unpainted bridges and exposed structural members, it requires low-hydrogen processes (Category B) per Table 5.11 due to its higher alloy content pushing CE-IIW to 0.45-0.52. Weld filler metal must be a matching weathering composition (e.g., E8018-W2) to achieve corrosion-matching at exposed joints. A588 is produced as plate up to 8" thick and is available in structural shapes, though A709 Gr.50W is more commonly specified for bridge applications.
Why This Preheat for A588 with SAW
Weathering steel forming protective patina for unpainted bridge applications. This steel is prequalified only with low-hydrogen processes under Table 5.11. With SAW, the submerged arc process with granular flux produces controlled hydrogen levels, with flux condition being the primary variable. The 32°F minimum preheat balances the steel’s strength level and carbon equivalent against the hydrogen control provided by SAW. Non-low-hydrogen SMAW is not an option for this grade under D1.1 prequalified WPS.
Typical Applications for A588
Used in unpainted highway bridge girders, exposed pedestrian bridges, architectural weathering facades, transmission tower legs, rail bridge stringers, and marine navigation light structures. A588 welds must use compatible weathering-type filler metals (e.g., E8018-W2 or ER80S-G) to achieve matching corrosion resistance in the exposed weld face. Girder flange splices and stiffener fillet welds are primary fabrication joints. The distinctive brown-orange patina develops over 2-5 years of atmospheric exposure to form a stable, adherent oxide layer that does not require repainting. In coastal locations with salt spray or in areas where the surface stays wet for extended periods, the protective oxide layer may not form properly, limiting A588 to inland applications with reliable wet-dry cycling. Bolt holes and copes must be deburred to prevent corrosion concentration. Drainage details in the steel design prevent water traps that would undermine the patina formation process.
Why Preheat Matters at up to 3/4"
Thin material sheds heat quickly, allowing hydrogen to escape the HAZ readily — lowest preheat tier in Table 5.11.
Other Steels with SAW at up to 3/4"
| Steel | Category | Preheat |
|---|---|---|
| A633 Gr.A/C/D | B | 32°F (0°C) |
| A633 Gr.E | C | 50°F (10°C) |
| A709 HPS70W | C | 50°F (10°C) |
| A710 Gr.A | C | 50°F (10°C) |
A588 with SAW
Try Different Combinations
Use the interactive preheat calculator to look up any steel, process, and thickness combination from D1.1:2025 Table 5.11.
A588 Welding Guides
Primary sources
D1.1:2025 reference data. Not affiliated with AWS.
Application context
A588 plate at or below 3/4 inch with SAW is the high-deposition shop combination for bare weathering-steel primary fabrication — bridge plate-girder long-seam fillet runs, transmission-tower main-leg long welds, and exposed-architectural primary members where the controlled-environment SAW process delivers high deposition rate on Group II HSLA plate.
Pre-weld notes
Three constraints sit on top of the 32°F preheat floor at this combination, all consumable-related rather than thermal. First, electrode-flux combination per Table 5.7 — A588 sits in Group II, with SAW columns listing F7XX-EXXX, F7XX-ECXXX, F7XX-E(C)XXX-A1, A2, A4, Ni1, Ni2 combinations under A5.17/A5.17M and A5.23/A5.23M. Second, for exposed unpainted applications the electrode-flux combination must conform to Table 5.9 per Clause 5.6.3 (Ni1, Ni2, Ni3, Ni4, or WX analysis under A5.23/A5.23M). Third, flux conditioning per Clause 7.3.3 — flux must be dry, damaged packages discarded or dried at 500°F minimum for one hour, top-inch discard rule, and reclaimed flux per Clause 7.3.3.3 must use a system maintaining constant composition.
What a CWI verifies
A CWI on bare A588 SAW thin-section shop work verifies (1) electrode-flux combination against Table 5.9 for exposed weathering applications and Table 5.7 Group II for matching strength, (2) flux dryness and the storage log per Clause 7.3.3, (3) current and layer width against Table 5.2 prequalified SAW limits for the specific electrode configuration, and (4) any reclaimed or crushed-slag flux against the Clause 7.3.3.3 and Clause 7.3.3.4 reuse rules. The 32°F preheat floor is rarely binding at this thickness; consumable selection and storage dominate.