A572 Gr.50 Preheat for SMAW (low-hydrogen) — up to 3/4"
Per AWS D1.1:2025 Table 5.11, the minimum preheat for A572 Gr.50 welded with SMAW (low-hydrogen) 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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SMAW (Low-Hydrogen)
Low-hydrogen SMAW (E7018/E7016) uses basic-coated electrodes requiring rod oven storage, assigned to Category B in Table 5.11.
E7018 is the default electrode for structural fillet and groove welds on common building steels. Rod ovens should hold at a minimum of 250°F per D1.1 Clause 7.3.2.1; exposure time out of the oven is limited to 4 hours maximum per Table 7.1. For overhead position, use 3/32" diameter rods to control puddle size. Vertical-up stringer beads provide the best fusion on thicker members.
SMAW-LH Tips for Common Structural Steels
For A572 Grade 50 structural steel (50 ksi yield, Category B only), E7018 handles column splice groove welds, moment frame beam flange welds in field conditions, and out-of-position connection welds impractical for wire-feed processes. On seismic demand-critical welds per AISC 341, E7018-H4 or E7018-H8 designations provide the hydrogen control for SMAW-LH to qualify for reduced preheat paths where applicable.
Typical values for reference — always verify against your approved WPS and electrode manufacturer data.
Why SMAW (low-hydrogen) for A572 Gr.50 at up to 3/4"
Why SMAW (low-hydrogen) for A572 Gr.50 at up to 3/4"? SMAW (low-hydrogen) delivers 3-5 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 SMAW-LH
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 SMAW-LH, E7018 low-hydrogen electrodes produce typically 4-8 mL/100g diffusible hydrogen under proper rod oven conditions. The 32°F minimum preheat balances the steel’s strength level and carbon equivalent against the hydrogen control provided by SMAW-LH. 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 SMAW (low-hydrogen) 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 SMAW (low-hydrogen)
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 SMAW low-hydrogen typically appears in stiffener plates, splice cover plates, and rolled-section reinforcement where the higher yield over A36 buys section efficiency without changing the preheat floor.
Pre-weld notes
The grade-50 yield doesn't shift the preheat category — A572 Gr.50 is in Category B alongside A36 at this thickness. The dominant pre-weld check is still electrode condition: low-hydrogen consumables out of an oven, atmospheric exposure tracked per D1.1 Clause 7.3, and storage in a holding oven (typically 250°F minimum) when not at the welder. The HSLA composition can be slightly less forgiving on hydrogen-induced cracking than plain carbon, which is why low-hydrogen is the default process here.
What a CWI verifies
A CWI verifies electrode storage and atmospheric exposure first; for HSLA plate the consumable-condition discipline is the practical lever, since the 32°F floor applies in normal conditions. Where a contractor has staged consumables on the bay floor for an extended period, the CWI flags the need to re-bake before use per Clause 7.3 atmospheric exposure provisions.