A992 Preheat for GMAW — over 2-1/2"

GMAW (Gas Metal Arc Welding)

GMAW (MIG) feeds continuous solid wire with shielding gas — an inherently low-hydrogen process assigned to Category B in Table 5.11.

ER70S-6 wire at 0.035" or 0.045" diameter handles most structural work on common grades. Spray transfer at 250-350 amps provides high deposition for shop fillet welds. For thinner material under 1/4", short-circuit transfer at lower parameters reduces heat input. Gas flow rates of 35-45 CFH through a standard nozzle provide adequate shielding in typical shop environments without excessive turbulence.

GMAW Tips for Common Structural Steels

For A992 wide-flange shapes (50 ksi yield, max 0.23% carbon, Category B), GMAW with 0.035" ER70S-6 at 210–260 A handles continuity plate fillet welds, doubler plate attachment welds, and shear tab shop welds on beams and columns. Moment-frame demand-critical welds per AWS D1.8 Clause 6.2.2 require notch-tough filler with CVN at no warmer than LAST+20°F for 70/80 ksi (at LAST for 90 ksi); a lower test temperature also complies. Preheat 32°F minimum up to 3/4".

Typical values for reference — always verify against your approved WPS and electrode manufacturer data.

Why GMAW for A992 at over 2-1/2"

Why GMAW for A992 at over 2-1/2"? GMAW delivers 8-12 lb/hr deposition — compared to <a href="/welding/preheat-calculator/a992/saw/over-2-1-2-inch/">SAW</a> at 15-40 lb/hr. Position capability: all positions (not GMAW-S). Suitability: primarily shop.

A992

ASTM A992 (50 ksi minimum yield, 65 ksi maximum yield, 65 ksi minimum tensile) is the standard specification for W-shapes in building construction — virtually all wide-flange beams and columns in US structural steel buildings are A992. The specification was created in 1998 to address weldability concerns with earlier A36/A572 shapes by imposing tighter chemistry controls: 0.23% max carbon, 0.15% max combined V+Cb+N, and a 0.85 maximum yield-to-tensile ratio to ensure ductile behavior in seismic connections. These controls produce a typical CE-IIW of 0.38-0.44. It falls under Category B in Table 5.11, requiring low-hydrogen welding processes. Most domestic W-shapes are dual-certified A992/A572 Gr.50, with actual mill test yields typically 50-58 ksi. The controlled chemistry makes A992 the most weldable 50 ksi structural shape available.

Why This Preheat for A992 with GMAW

Standard W-shape specification for virtually all US building wide-flanges. This steel is prequalified only with low-hydrogen processes under Table 5.11. With GMAW, the continuous solid wire and gas shielding in GMAW produce inherently low hydrogen levels, typically 2-4 mL/100g. The 225°F minimum preheat balances the steel’s strength level and carbon equivalent against the hydrogen control provided by GMAW. Non-low-hydrogen SMAW is not an option for this grade under D1.1 prequalified WPS.

Typical Applications for A992

The universal W-shape steel for building frames: beam-to-column moment connections, simple shear tabs, column web doubler plates, continuity plates, collector beams in lateral systems, drag struts, transfer beams, and composite deck stud rails. A992 chemistry control (max 0.23% carbon, max 0.15% V-Cb-N) was specifically designed to improve weldability over earlier A36/A572 shapes after the 1994 Northridge earthquake revealed brittle fracture problems in welded steel moment frames. Flange CJP welds in seismic moment frames are the highest-criticality joints in US building construction. The controlled yield-to-tensile ratio (max 0.85) ensures ductile behavior in seismic connections by guaranteeing sufficient strain hardening capacity. Mill test reports for A992 shapes routinely show actual yield strengths of 50-55 ksi, well above the 50 ksi minimum. The weld access hole geometry per AISC 358 is dimensioned specifically for A992 flanges to reduce stress concentrations at the CJP weld termination.

Why Preheat Matters at over 2-1/2"

The heaviest sections demand the highest preheat in Table 5.11. Multi-pass sequences require maintaining interpass temperature throughout.

Other Steels with GMAW at over 2-1/2"

A992 with GMAW

Try Different Combinations

Use the interactive preheat calculator to look up any steel, process, and thickness combination from D1.1:2025 Table 5.11.

A992 Welding Guides