A913 Gr.80 Preheat for GMAW (H4) — 3/4" to 1-1/2"

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.

On high-strength plate, GMAW wire selection must meet the specified minimum tensile to satisfy weld metal matching. ER80S-D2 or ER100S-G wires serve higher-strength steels. The inherently low hydrogen input of solid wire makes GMAW particularly well-suited for crack-sensitive TMCP grades where minimizing diffusible hydrogen is the primary fabrication objective.

A913 Gr.80

ASTM A913 Grade 80 (80 ksi yield, 95 ksi minimum tensile) is the highest-strength TMCP shape specification in D1.1, produced exclusively by the QST process. It requires H4-certified consumables (the strictest hydrogen control at ≤4 mL/100g deposited weld metal per AWS A4.3) and falls exclusively under Category G, which has four thickness-dependent preheat tiers (32°F up to 3/4”, 50°F up to 1-1/2”, 150°F up to 2-1/2”, 225°F above). No other hydrogen designation, standard low-hydrogen, or non-low-hydrogen SMAW is prequalified for this grade under Table 5.11. The H4 requirement limits the available consumable pool significantly — only select electrode classifications carry the H4 designator. A913 Gr.80 availability is limited to heavy W14 column sections from a small number of domestic and international mills, with procurement lead times typically 16-24 weeks.

Why This Preheat for A913 Gr.80 with GMAW

Highest-strength 80 ksi TMCP shape requiring H4 consumables exclusively. This steel requires H4-certified consumables — the strictest hydrogen control in Table 5.11 at no more than 4 mL diffusible hydrogen per 100g. At 50°F with GMAW, the four thickness-dependent preheat tiers in Category G reflect the balance between the steel's 80 ksi yield strength and the exceptional hydrogen control provided by H4 certification. No other hydrogen designation is prequalified for this grade.

Typical Applications for A913 Gr.80

Reserved for the most demanding column applications in super-tall structures, typically interior gravity columns carrying 50+ stories of tributary load. A913 Gr.80 allows W14 sections to replace built-up box columns, simplifying connections and reducing fabrication cost while maintaining equivalent axial capacity. Every weld on this grade demands verified H4 consumables and documented preheat compliance — no exceptions or substitutions are permitted under Table 5.11. Column splice CJP welds require UT inspection per D1.1 Table 8.2. Only a limited number of domestic mills produce A913 Gr.80 shapes, with lead times of 16-24 weeks for non-stock sizes. The H4 consumable requirement eliminates most standard electrode inventory and requires dedicated electrode orders for each project. Fabricators must establish verified H4 supply chains before bidding Gr.80 column work, as H4-designated electrodes are not stocked by most welding distributors. Rejected consumable certifications can delay erection schedules by weeks.

Why Preheat Matters at 3/4" to 1-1/2"

Preheat climbs at this range as thicker material slows heat dissipation, trapping hydrogen at crack-susceptible grain boundaries.

A913 Gr.80 with GMAW (H4)

Try Different Combinations

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

A913 Gr.80 Welding Guides