A710 Gr.A Preheat for SMAW (low-hydrogen) — over 2-1/2"

SMAW (Low-Hydrogen)

Low-hydrogen SMAW (E7018/E7016) uses basic-coated electrodes requiring rod oven storage, assigned to Category B in Table 5.11.

For high-strength shapes and plate, the Table 5.11 preheat category does not select the filler metal. Matching strength follows the steel's base-metal group in D1.1 Table 5.6: Table 5.7 lists AWS A5.1 carbon-steel electrodes such as E7018 for Group I and Group II base metals and marks A5.1 N/A for Groups III, IV and V, which take AWS A5.5 low-alloy electrodes such as E8018-C3 (Group III), E9018M (Group IV) or E10018M (Group V). Bead sequencing on thick TMCP flanges should follow qualified WPS parameters precisely to avoid overheating the refined microstructure.

SMAW-LH Tips for High-Strength and TMCP Steels

For A710 Grade A precipitation-hardened low-carbon plate (0.07% max carbon), E7018-H8 certified electrodes (not just standard E7018) qualify for the Category D reduced-preheat path (32°F all thicknesses) when combined with the inherent crack resistance of this ultra-low-carbon steel. With standard E7018 this calculator shows the Category C value, which applies only to Class 2 up to 2 in [50 mm] or Class 3 over 2 in [50 mm]; Table 5.11 lists Class 2 over 2 in [50 mm] under Category B. Verify H8 marking on individual rod packages and box labels before claiming the reduced preheat path.

Typical values for reference — always verify against your approved WPS and electrode manufacturer data. This 300°F (150°C) value applies only to A710 Grade A Class 3 (over 2 in [50 mm]); Class 2 at this thickness is Category B, and Class 1 is listed only under Category D with H8.

Why SMAW (low-hydrogen) for A710 Gr.A at over 2-1/2"

Why SMAW (low-hydrogen) for A710 Gr.A at over 2-1/2"? SMAW (low-hydrogen) delivers 3-5 lb/hr deposition — compared to <a href="/welding/preheat-calculator/a710-a/saw/over-2-1-2-inch/">SAW</a> at 15-40 lb/hr. Position capability: all positions. Suitability: field and shop.

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 lists it by class and thickness: with standard low-hydrogen processes, Category C covers Class 2 up to 2 in [50 mm] and Class 3 over 2 in [50 mm] and Category B covers Class 2 over 2 in [50 mm], while every class takes 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. This 300°F (150°C) value applies only to A710 Grade A Class 3 (over 2 in [50 mm]); Class 2 at this thickness is Category B, and Class 1 is listed only under Category D with H8.

A710 Grade A Table 5.11 split

A710 Grade A is listed by class and thickness in AWS D1.1:2025 Table 5.11. The Category C value on this page applies only to Class 2 up to 2 in [50 mm] and Class 3 over 2 in [50 mm]. Class 2 over 2 in [50 mm] is Category B. Class 1, and Class 3 up to 2 in [50 mm], have no Table 5.11 row without H8 consumables and are listed only under Category D with H8, so this value does not apply to them. Confirm the class before using it.

Why This Preheat for A710 Gr.A with SMAW-LH

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 300°F minimum with SMAW-LH, E7018 low-hydrogen electrodes produce typically 4-8 mL/100g diffusible hydrogen under proper rod oven conditions, but the preheat must still ensure the cooling rate stays slow enough to prevent hydrogen-induced cracking in this higher-hardenability material. This 300°F (150°C) value applies only to A710 Grade A Class 3 (over 2 in [50 mm]); Class 2 at this thickness is Category B, and Class 1 is listed only under Category D with H8.

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 over 2-1/2"

The heaviest sections demand the highest preheat in Table 5.11. Multi-pass sequences require maintaining interpass temperature throughout.

Category C Preheat for A710 Gr.A

Category C in Table 5.11 applies to higher-strength steels where the combination of hardenability and residual stress requires elevated preheat. For A710 Gr.A at over 2-1/2", the 300°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. This 300°F (150°C) value applies only to A710 Grade A Class 3 (over 2 in [50 mm]); Class 2 at this thickness is Category B, and Class 1 is listed only under Category D with H8.

Other Steels with SMAW (low-hydrogen) at over 2-1/2"

A710 Gr.A with SMAW (low-hydrogen)

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