A572 Gr.50 Preheat for SAW — up to 3/4"
Per AWS D1.1:2025 Table 5.11, the minimum preheat for A572 Gr.50 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.
Have a preheat question? Ask Flux
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 A572 Grade 50 structural steel (50 ksi yield, Category B only), SAW F7A2-EM12K at 550–700 A is the dominant process for crane runway girder web-to-flange fillet welds, built-up column seams, and plate girder fabrication in building construction. The deep-penetrating SAW arc on A572 Gr.50 plate achieves excellent root fusion on fillet welds without back-gouging.
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.
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 SAW
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 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 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 SAW 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 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.
A572 Gr.50 Welding Guides
Primary sources
D1.1:2025 reference data. Not affiliated with AWS.
Application context
A572 Grade 50 plate at or below 3/4 inch with SAW is the high-deposition shop combination for HSLA structural fabrication — plate girder long-seam fillet runs, beam-flange-to-web automated welds, transmission-tower lattice main-leg long welds, and similar production work where the controlled-environment SAW process delivers high deposition rate and predictable bead geometry on Grade 50 plate.
Pre-weld notes
Three SAW-specific constraints sit on top of the 32°F preheat floor. First, electrode-flux combination per Table 5.7 — A572 Grade 50 sits in Group II, with SAW columns listing F7XX-EXXX, F7XX-ECXXX, and F7XX-E(C)XXX-A1, A2, A4, Ni1, Ni2 combinations under A5.17/A5.17M and A5.23/A5.23M. Second, flux conditioning per Clause 7.3.3 — flux must be dry and free of contamination, damaged packages must be discarded or dried at 500°F minimum for one hour before use. Third, current and layer-width windows per Table 5.2 prequalified SAW limits, which differ across single, parallel, and multiple electrode configurations.
What a CWI verifies
A CWI on A572-50 SAW thin-section shop work verifies (1) electrode-flux combination against Table 5.7 Group II, (2) flux dryness and the storage log, (3) current and layer width against Table 5.2 prequalified SAW limits for the specific electrode configuration, and (4) any flux reclamation system against Clause 7.3.3.3 — the contractor must have a system for collecting unmelted flux, adding new flux, and welding such that flux composition and particle-size distribution stay relatively constant. The 32°F preheat floor is rarely binding at this thickness.