A572 Gr.50 Preheat for FCAW — 1-1/2" to 2-1/2"
Per AWS D1.1:2025 Table 5.11, the minimum preheat for A572 Gr.50 welded with FCAW at 1-1/2" to 2-1/2" is 150°F (65°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 1-1/2" to 2-1/2"
Why FCAW for A572 Gr.50 at 1-1/2" to 2-1/2"? FCAW delivers 8-12 lb/hr deposition — compared to <a href="/welding/preheat-calculator/a572-50/saw/1-1-2-to-2-1-2-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 150°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 1-1/2" to 2-1/2"
Heavy plate with significant restraint and thermal mass — preheat is critical to maintain slow cooling for hydrogen escape.
Other Steels with FCAW at 1-1/2" to 2-1/2"
| Steel | Category | Preheat |
|---|---|---|
| A588 | B | 150°F (65°C) |
| A633 Gr.E | C | 225°F (110°C) |
| A709 HPS70W | C | 225°F (110°C) |
| A710 Gr.A | C | 225°F (110°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 Grade 50 plate in the 1-1/2 to 2-1/2 inch range with FCAW is the heavy-section HSLA production combination — primary fillet runs on transmission-tower main-leg splices, AISC moment-frame heavy connection plates, transfer-girder splice fillets, and outdoor field-erection welds where the higher deposition rate of cored wire moves more steel per shift than SMAW under outdoor conditions and the 150°F floor is binding.
Pre-weld notes
Crossing the 1-1/2 inch threshold changes the preheat-extent rule per Clause 7.6 — for base metal 1-1/2 inch and greater, the heated zone shall extend at least equal to the base-metal thickness, but not less than 3 inches. Real preheat infrastructure is required: induction blankets, electric resistance pads, or oxy-fuel rosebud burners. Through-thickness preheat verification is the binding inspection effort. FCAW classification on the spool against the WPS-cited variant — self-shielded vs gas-shielded is an essential variable per Table 6.6, with FCAW-S preferred for outdoor field work where wind disrupts gas-shielded variants.
What a CWI verifies
A CWI on A572-50 FCAW heavy-section work verifies (1) preheat through-thickness, not just surface — sampling 3-6 inches from the arc on the back side catches the through-thickness lag during heat-up, (2) the heated-zone extent against Clause 7.6, (3) interpass temperature held above 150°F with a contact pyrometer between pass groups, (4) the FCAW classification on the spool against the WPS-cited variant, and (5) inter-pass slag removal across the joint sequence. AISC moment-frame and transmission-tower projects commonly add CVN testing under structural specifications that elevate the WPS to qualified rather than prequalified.