A710 Gr.A Preheat for SAW — 3/4" to 1-1/2"

SAW (Submerged Arc Welding)

SAW submerges the arc beneath granular flux for highest deposition rates, flat/horizontal only. Category B in Table 5.11.

SAW on high-strength plate requires careful selection of wire-flux combinations to meet both tensile matching and toughness requirements. F8A4-EA2 or similar high-performance combinations serve Category C steels. Heat input control is particularly important on TMCP grades because SAW naturally deposits high heat input due to the deeply penetrating arc.

A710 Gr.A

ASTM A710 Grade A is a precipitation-hardened low-carbon steel plate achieving high strength through copper precipitation rather than carbon content. Class 2 (65 ksi yield, age-hardened at mill) and Class 3 (75 ksi yield, precipitation-hardened after fabrication) both feature very low carbon (0.07% max) producing a CE-IIW of approximately 0.32-0.38 — among the lowest of any high-strength steel. Table 5.11 assigns Category C for standard low-hydrogen processes and the reduced Category D preheat (32°F all thicknesses) with H8-certified consumables, reflecting the exceptional hydrogen cracking resistance of this ultra-low-carbon metallurgy. The precipitation hardening mechanism means weld thermal cycles can alter the strength in the HAZ depending on peak temperature and cooling rate, requiring attention to heat input control during procedure qualification.

Why This Preheat for A710 Gr.A with SAW

Precipitation-hardened low-carbon plate with multiple category paths. 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 150°F minimum with SAW, the preheat ensures the cooling rate stays slow enough to prevent hydrogen-induced cracking in this higher-hardenability material. Category C steels demand careful attention to interpass temperature control throughout the weld sequence.

Typical Applications for A710 Gr.A

Found in naval hull plates, military vehicle armor brackets, offshore platform node connections, heavy-lift crane boom sections, and mine hoist drum shells. A710 Gr.A precipitation-hardened plate offers a rare combination of high strength and exceptional weldability at low carbon equivalent (CE-IIW approximately 0.32-0.38). The multiple thickness-dependent category paths (B, C, and D with H8) reflect its complex metallurgical response to different section sizes. Class 2 plate is age-hardened at the mill through a controlled thermal cycle, while Class 3 achieves higher strength through precipitation hardening after welding, which makes it particularly suitable for applications where extensive welding occurs before final strengthening. The distinction between Class 2 and Class 3 response to weld thermal cycles requires careful attention during procedure qualification. Plate thicknesses up to 6" are available but procurement requires extended lead times due to limited production volume.

Why Preheat Matters at 3/4" to 1-1/2"

Preheat climbs at this range as thicker material slows heat dissipation, trapping hydrogen at crack-susceptible grain boundaries.

Other Steels with SAW at 3/4" to 1-1/2"

A710 Gr.A with SAW

Try Different Combinations

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

A710 Gr.A Welding Guides