A913 Gr.50/60/65 Preheat for GMAW — up to 3/4"

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 follows the steel's Table 5.6 base-metal group: Table 5.7 marks AWS A5.18 carbon-steel wire N/A for Groups III, IV and V and lists AWS A5.28 low-alloy classifications such as ER80S-Ni1 (Group III), ER90S-D2 (Group IV) and ER100S-1 (Group V). 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.

GMAW Tips for High-Strength and TMCP Steels

For A913 Grades 50/60/65 TMCP shapes (CE-IIW 0.35–0.42), GMAW spray transfer at 210–280 A with ER70S-6 is particularly effective — the inherently low hydrogen of solid wire pairs well with the QST microstructure. Standard Category B applies; H8-certified wire (most ER70S-6 wire already meets H8 limits) qualifies for Category D (32°F all thicknesses). Verify the H8 designation on the wire.

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

Why GMAW for A913 Gr.50/60/65 at up to 3/4"

Why GMAW for A913 Gr.50/60/65 at up to 3/4"? GMAW delivers 8-12 lb/hr deposition — compared to <a href="/welding/preheat-calculator/a913-506065/saw/up-to-3-4-inch/">SAW</a> at 15-40 lb/hr. Position capability: all positions (not GMAW-S). Suitability: primarily shop.

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. With GMAW, the continuous solid wire and gas shielding in GMAW produce inherently low hydrogen levels, typically 2-4 mL/100g. The 32°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 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 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 GMAW at up to 3/4"

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