A913 Gr.50/60/65 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.

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.50/60/65

ASTM A913 Grades 50 (50 ksi yield), 60 (60 ksi yield), and 65 (65 ksi yield) are quenched-and-self-tempered (QST) structural shapes produced by thermo-mechanical controlled processing (TMCP) — an in-line water quench immediately after the final rolling pass, followed by self-tempering from the core heat. This produces a fine-grained bainitic/ferritic microstructure throughout the full cross-section with carbon content typically 0.10-0.16% and CE-IIW of 0.35-0.42. Standard low-hydrogen processes use Category B; H8-certified consumables qualify for the reduced Category D (32°F all thicknesses), reflecting the inherent hydrogen cracking resistance of the TMCP microstructure. Available exclusively as W-shapes (primarily W14 heavy column sections), A913 is not produced as plate or other forms. The QST process eliminates the need for separate mill heat treatment, providing consistent through-thickness properties.

Why This Preheat for A913 Gr.50/60/65 with GMAW

TMCP structural shapes for seismic frames with H8-eligible reduced preheat. This steel is prequalified only with low-hydrogen processes under Table 5.11, which is why it appears in Category B but not Category A. The 225°F minimum preheat with GMAW balances the steel's strength level and carbon equivalent against the controlled hydrogen input from the consumable. Non-low-hydrogen SMAW is not an option for this grade under D1.1 prequalified WPS.

Typical Applications for A913 Gr.50/60/65

Specified for seismic moment frame columns, high-rise building corner columns, transfer girder bearing seats, heavy truss chords, stadium cantilever support columns, and parking garage moment frame members. A913 TMCP shapes eliminate the need for post-rolling heat treatment, providing consistent through-thickness properties from flange tip to web center. Column splice CJP welds and beam-to-column continuity plate fillet welds are the critical weld joints. Available in W14 sections from W14x132 through W14x730, these shapes are the backbone of seismic column design in high-rise construction. The TMCP process creates a fine-grained microstructure throughout the full cross-section, unlike conventional heat-treated shapes that may have property gradients. The H8 path to Category D (32°F all thicknesses) offers significant fabrication cost savings on heavy column splices that would otherwise require 150-225°F preheat under Category B. Column flange thicknesses on W14x455 and heavier sections exceed 3".

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"

A913 Gr.50/60/65 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.

A913 Gr.50/60/65 Welding Guides