A913 Gr.70 Preheat for GMAW (H8) — over 2-1/2"
Minimum preheat and interpass temperature for A913 Gr.70 welded with GMAW (H8) at over 2-1/2" thickness, per AWS D1.1:2025 Table 5.11.
H8-certified consumables — reduced preheat for A913 Gr.70
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.70
ASTM A913 Grade 70 (70 ksi yield, 90 ksi minimum tensile) is a TMCP structural shape used in heavily loaded columns and seismic applications requiring higher strength than Gr.50/60/65. It falls under Category C for standard low-hydrogen processes, with preheat requirements reflecting its higher strength level and CE-IIW of approximately 0.42-0.48. With H8-certified consumables, it qualifies for Category F — 32°F up to 2-1/2”, 150°F above. The TMCP QST microstructure provides inherent resistance to hydrogen cracking through its fine-grained bainitic structure, which is why H8 consumables unlock a reduced-preheat path not available for conventional Q&T steels at similar strength. A913 Gr.70 is primarily available in W14 sections ranging from W14x233 through W14x730, with limited W12 and W36 availability.
Why This Preheat for A913 Gr.70 with GMAW
TMCP 70 ksi shape with Category F reduced preheat using H8 consumables. H8-certified consumables with GMAW place this in Category F of Table 5.11. At 150°F, the preheat requirement reflects the TMCP microstructure's inherent resistance to hydrogen cracking combined with the controlled hydrogen input from H8 consumables. Category F uses a 2-1/2-inch thickness breakpoint, allowing 32°F preheat for most practical section sizes.
Typical Applications for A913 Gr.70
Used in heavily loaded interior columns of super-tall buildings, transfer truss compression chords, mega-brace members in outrigger systems, stadium roof cantilever supports, and seismic collectors in high-rise cores. A913 Gr.70 TMCP shapes enable smaller column sections, freeing usable floor space on every floor of the building. Column splice butt welds at upper stories and moment connection flange welds carry the highest inspection priority. The 70 ksi yield enables using W14x398 where conventional Gr.50 would require W14x550, saving 38% in material weight and 3-4 inches of floor space per column. Erection splices at every 2-3 stories use CJP groove welds with backing bars removed and back-gouged per seismic detailing requirements. The Category F path with H8 consumables (32°F up to 2-1/2", 150°F above) provides a practical alternative to full Category C preheat on these thick-flange column splices.
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.
H8-Certified Consumables for A913 Gr.70
The H8 supplementary designator on a consumable classification (e.g., E7018-H8) certifies that the electrode deposits no more than 8 mL of diffusible hydrogen per 100g of deposited weld metal, tested per AWS A4.3. For A913 Gr.70, using H8 consumables qualifies for Category F with reduced preheat of 150°F at over 2-1/2" thickness. Verify the H8 designator on electrode packaging or manufacturer certification before claiming the reduced preheat category.
A913 Gr.70 with GMAW (H8)
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.70 Welding Guides
D1.1:2025 reference data. Not affiliated with AWS.