A633 Gr.A/C/D Preheat for FCAW — up to 3/4"

FCAW (Flux Cored Arc Welding)

FCAW uses tubular flux-cored wire, available gas-shielded (E71T-1) or self-shielded (E71T-8) for field work. Category B in Table 5.11.

For vessel fabrication, FCAW offers a productivity advantage over SMAW on long circumferential and longitudinal seams. Gas-shielded E71T-1 provides consistent bead profile for radiographic quality. Self-shielded wire is generally not approved for ASME pressure service due to higher inclusion content in the weld deposit.

A633 Gr.A/C/D

ASTM A633 Grades A, C, and D are normalized high-strength low-alloy structural plates with enhanced notch toughness for structural applications at temperatures down to -75°F. Grade A (42 ksi yield) provides basic low-temperature service; Grade C (50 ksi yield) is the most widely specified for cold-region bridges; Grade D (50 ksi yield) offers the lowest test temperature at -75°F for Arctic service. All are normalized to produce a fine-grained microstructure that resists brittle fracture. They fall under Category B in Table 5.11, with chemistry limits (0.20% max carbon for Gr.C/D, Nb and V microalloying) producing a CE-IIW of 0.38-0.44. Charpy V-notch specimens are tested in the transverse direction at -50°F (Gr.C) or -75°F (Gr.D) with 20 ft-lbs minimum absorbed energy per ASTM requirements.

Why This Preheat for A633 Gr.A/C/D with FCAW

Normalized HSLA plate with enhanced toughness for cold environments to -75°F. 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 32°F minimum preheat with FCAW 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 A633 Gr.A/C/D

Specified for bridge pier caps in cold regions, offshore platform deck plates, Arctic pipeline support structures, cold-climate building trusses, icebreaker hull stiffeners, and polar research station framing. A633 Grades C and D provide guaranteed Charpy toughness at -40°F and -75°F respectively, making them essential for structures operating in extreme cold where brittle fracture is the primary failure mode. Impact specimen orientation (longitudinal vs transverse) affects the guaranteed toughness values and must be specified at procurement. Field welding on A633 in sub-zero ambient conditions requires heated enclosures or windbreaks to maintain interpass temperature above the Table 5.11 minimum. Filler metals for cold-region service must also meet CVN requirements at the design service temperature, typically requiring -20°F or colder impact testing. Weld procedure qualification includes impact testing of the weld metal and HAZ at the minimum design temperature.

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 FCAW at up to 3/4"

A633 Gr.A/C/D with FCAW

Try Different Combinations

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

A633 Gr.A/C/D Welding Guides