A572 Gr.50 Preheat for FCAW — up to 3/4"
Per AWS D1.1:2025 Table 5.11, the minimum preheat for A572 Gr.50 welded with FCAW 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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FCAW (Flux Cored Arc Welding)
FCAW uses tubular flux-cored wire, available gas-shielded (E71T-1) or self-shielded (E71T-8) for field work. Category B in Table 5.11.
E71T-1 gas-shielded wire is the workhorse for structural steel erection fillet welds. Self-shielded E71T-8 is preferred for field welding where wind makes gas shielding unreliable. Deposition rates run 8-12 lb/hr depending on wire diameter and position. The flux core provides a protective slag that supports the puddle in vertical-up and overhead positions.
FCAW Tips for Common Structural Steels
For A572 Grade 50 structural steel (50 ksi yield, Category B only — non-LH SMAW not prequalified), FCAW with E71T-1M at 220–260 A is the standard process for column stiffener welds, continuity plates, and field moment frame connection welds. The all-position capability of FCAW handles overhead-position fillet welds on column doubler plate attachments that would be impractical with SAW.
Typical values for reference — always verify against your approved WPS and electrode manufacturer data.
Why FCAW for A572 Gr.50 at up to 3/4"
Why FCAW for A572 Gr.50 at up to 3/4"? FCAW delivers 8-12 lb/hr deposition — compared to <a href="/welding/preheat-calculator/a572-50/saw/up-to-3-4-inch/">SAW</a> at 15-40 lb/hr. Position capability: all positions. Suitability: field and shop.
A572 Gr.50
ASTM A572 Grade 50 (50 ksi minimum yield, 65 ksi minimum tensile) is the dominant high-strength low-alloy structural steel in building construction. Most W-shapes rolled today are dual-certified A572/A992, with actual yield typically 50-58 ksi. It falls under Category B only in Table 5.11 — non-low-hydrogen SMAW is not prequalified for this grade. Chemistry limits include 0.23% max carbon (shapes) and columbium (niobium) or vanadium microalloying for grain refinement, producing a typical CE-IIW of 0.40-0.45. A572 Gr.50 plate is available in thicknesses up to 6" and is the default grade for connection plates, gussets, and base plates in building construction when loads exceed A36 capacity. The Gr.42, 55, 60, and 65 grades exist but Gr.50 accounts for over 90% of A572 production.
Why This Preheat for A572 Gr.50 with FCAW
Dominant 50 ksi HSLA structural steel often dual-certified with A992. This steel is prequalified only with low-hydrogen processes under Table 5.11. With FCAW, flux-cored wire in FCAW provides a combination of deoxidizers and low-moisture flux formulations that control hydrogen. The 32°F minimum preheat balances the steel’s strength level and carbon equivalent against the hydrogen control provided by FCAW. Non-low-hydrogen SMAW is not an option for this grade under D1.1 prequalified WPS.
Typical Applications for A572 Gr.50
Dominates building construction for W-shape column splices, beam-to-column moment connections, braced frame gusset plates, base plates over 36 ksi demand, crane runway girder webs, and mezzanine floor beams. A572 Gr.50 plate is the standard for connection elements in seismic designs per AISC 341. Complete joint penetration groove welds at beam flanges are the most critical weld detail in moment frames. The most common connection plate thicknesses are 3/4" and 1" for moment end plates and 1/2" to 5/8" for shear tabs. Demand-critical welds in seismic applications require notch-tough filler metals meeting AISC 341 Section A3.4b and AWS D1.8 Clause 6.2.2: CVN tested at no warmer than LAST+20°F for 70/80 ksi fillers (at LAST for 90 ksi); a lower test temperature also complies. Column splice CJP welds at every 2-3 story intervals are typically 2G or 3G field welds requiring portable preheat equipment. Base plate welds to foundation embed plates carry the full column load and require strict preheat compliance on thicker plates.
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 FCAW at up to 3/4"
| Steel | Category | Preheat |
|---|---|---|
| A588 | 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) |
A572 Gr.50 with FCAW
Try Different Combinations
Use the interactive preheat calculator to look up any steel, process, and thickness combination from D1.1:2025 Table 5.11.
A572 Gr.50 Welding Guides
Primary sources
D1.1:2025 reference data. Not affiliated with AWS.
Application context
A572 Gr.50 plate at or below 3/4 inch with FCAW appears in shop-welded HSLA work where the higher deposition rate of flux-cored matches the production cadence — long fillet runs on stiffeners, repeating connection details on bridge or transmission components.
Pre-weld notes
Same 32°F floor as A36 at this thickness — Category B in Table 5.11 covers both grades for FCAW. The HSLA chemistry shifts the consumable selection: flux-cored electrodes for HSLA welding typically carry an E71T-X or E81T-X classification with low-hydrogen designators. Check the specific classification against Table 5.4 prequalified requirements and Table 5.7 matching-strength requirements. Slag removal between passes is the recurring FCAW issue regardless of base metal.
What a CWI verifies
A CWI on this combination verifies the FCAW electrode classification against Table 5.4 prequalified requirements first, then checks slag removal and deposit contour through the joint. Filler-metal matching-strength per Table 5.7 is the second check; on HSLA the matching-strength selection is more sensitive than on plain carbon.