A633 Gr.E 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.

FCAW Tips for Pressure Vessel and Low-Temperature Steels

For A633 Grade E (60 ksi yield, Category C, CVN at -60°F), FCAW requires higher-strength wire — E81T1-Ni1 or E91T1-K2 for tensile matching at 80–90 ksi. Category C minimum preheat starts at 50°F (up to 3/4") and reaches 300°F above 2-1/2" with FCAW (Category C applies regardless of process). H8-certified E81T1-Ni1 provides both the tensile match and low diffusible hydrogen.

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

Why FCAW for A633 Gr.E at up to 3/4"

Why FCAW for A633 Gr.E at up to 3/4"? FCAW delivers 8-12 lb/hr deposition — compared to SAW at 15-40 lb/hr. Position capability: all positions. Suitability: field and shop.

A633 Gr.E

ASTM A633 Grade E is the highest-strength grade in this specification with 60 ksi minimum yield and 80 ksi minimum tensile strength (for plates up to 4”). Produced as normalized and tempered plate, it provides exceptional notch toughness with CVN testing at -60°F (15 ft-lbs transverse). Its higher strength level places it in Category C of Table 5.11, with correspondingly higher preheat requirements than the A/C/D grades. The quenched-and-tempered condition means carbon content is higher (0.22% max) with controlled manganese (1.15-1.50%) and silicon (0.15-0.50%), producing a CE-IIW of approximately 0.44-0.50. Like all Q&T steels, maximum interpass temperature must be respected to avoid degrading the tempered microstructure in the heat-affected zone during multi-pass welding.

Why This Preheat for A633 Gr.E with FCAW

Highest-strength A633 grade at 60 ksi yield requiring Category C preheat. The higher strength level of this steel places it in Category C of Table 5.11, which carries elevated preheat requirements compared to Category B grades. At 50°F minimum with FCAW, flux-cored wire in FCAW provides a combination of deoxidizers and low-moisture flux formulations that control hydrogen, but the preheat must still ensure the cooling rate stays slow enough to prevent hydrogen-induced cracking in this higher-hardenability material.

Typical Applications for A633 Gr.E

Found in heavy-duty crane runway girders for steel mills, offshore jacket legs, polar Class vessels, cold-region bridge main members, large-span roof trusses in Arctic facilities, and load-bearing elements in LNG terminal structures. A633 Gr.E combines 60 ksi yield with excellent low-temperature toughness (CVN testing at -60°F), making it suitable for primary structural members in environments where both high static loads and extreme cold coincide. Procurement lead times for A633 Gr.E plate can be 12-16 weeks due to limited domestic production, and plate availability above 2" thickness may require international sourcing. Repair welding requires the same preheat procedures as original fabrication to maintain the guaranteed toughness properties. Filler metal selection must provide tensile matching (80 ksi minimum) and cold-temperature CVN values that equal or exceed the base metal specification. Weld mockups for offshore and LNG applications typically undergo CTOD or wide-plate testing.

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.

Category C Preheat for A633 Gr.E

Category C in Table 5.11 applies to higher-strength steels where the combination of hardenability and residual stress requires elevated preheat. For A633 Gr.E at up to 3/4", the 50°F minimum preheat slows the weld cooling rate to prevent formation of crack-susceptible martensite in the heat-affected zone. Maintaining interpass temperature at or above this minimum is especially critical for multi-pass welds on restrained joints.

Other Steels with FCAW at up to 3/4"

A633 Gr.E 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.E Welding Guides