A709 Gr.36 Preheat for SMAW (non-low-hydrogen) — up to 3/4"

SMAW (Non-Low-Hydrogen)

Non-low-hydrogen SMAW (E6010/E6011) uses cellulosic electrodes with higher hydrogen potential, assigned to Category A in Table 5.11.

For common structural shapes and plate, non-low-hydrogen SMAW with E6010 or E6011 excels at root passes on open-root groove welds where burn-through control matters. Vertical-up technique with a slight weave keeps the puddle manageable. Rod consumption runs about 10-12 electrodes per pound of weld metal deposited. Electrode stubs should be no shorter than 2 inches to maintain adequate arc length control.

SMAW Tips for Common Structural Steels

For A709 Grade 36 bridge steel (36 ksi yield, Category A and B), E6010 at 80–120 A handles root passes and field tack welds on secondary bridge members (stiffeners, lateral bracing) under D1.1. Bridge fabrication governed by D1.5 imposes additional restrictions — check whether D1.5 limits cellulosic electrode use on fracture-critical members. Under D1.1 Category A, E6010 on A709 Gr.36.

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

Why SMAW (non-low-hydrogen) for A709 Gr.36 at up to 3/4"

Why SMAW (non-low-hydrogen) for A709 Gr.36 at up to 3/4"? SMAW (non-low-hydrogen) delivers 3-5 lb/hr deposition — compared to SAW at 15-40 lb/hr. Position capability: all positions. Suitability: field and shop.

A709 Gr.36

ASTM A709 Grade 36 is the bridge-specific equivalent of A36, used exclusively for highway bridge construction under AASHTO LRFD Bridge Design Specifications. With 36 ksi minimum yield, 58-80 ksi tensile, and mandatory Charpy V-notch testing requirements based on AASHTO temperature zone (Zone 1: 70°F, Zone 2: 40°F, Zone 3: 10°F test temperatures), it qualifies for both Category A and Category B preheat in Table 5.11. Chemistry matches A36 (0.26% max carbon) but the CVN requirements add a fracture resistance guarantee absent from plain A36. A709 Gr.36 is primarily used for secondary bridge members — lateral bracing, floor beam stiffeners, diaphragm plates, and bearing components — where Gr.50 strength is not needed but bridge-code CVN compliance is required.

Why This Preheat for A709 Gr.36 with SMAW

Bridge-specific 36 ksi grade with CVN testing for highway construction. At this thickness, SMAW with non-low-hydrogen electrodes places the joint in Category A of Table 5.11. The minimum preheat of 32°F compensates for the higher diffusible hydrogen from cellulosic electrode coatings. The thicker the material, the longer hydrogen takes to escape the heat-affected zone, which is why preheat rises with thickness even for this common grade.

Typical Applications for A709 Gr.36

Specified exclusively for highway bridge deck plate, floor beams, lateral bracing, secondary framing, bridge railing posts, abutment bearing stiffeners, and diaphragm plates. A709 Gr.36 requires CVN testing per AASHTO zone classification, distinguishing it from plain A36 by guaranteeing fracture resistance at the bridge’s design service temperature. Transverse stiffener fillet welds and floor beam web-to-flange joints are high-frequency fabrication details in bridge shops. The fracture-critical designation on certain bridge members imposes additional NDT requirements (UT in lieu of RT for CJP welds) and welder qualification testing beyond standard D1.5 provisions. Temperature zones (1 through 3) determine the CVN test temperature for the Charpy specimens: Zone 1 at 70°F for moderate climates, Zone 2 at 40°F for cold climates, and Zone 3 at 10°F for severe cold. Mill certifications must show CVN results meeting the specified zone before plate release to the bridge fabricator.

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.

Why 32°F for A709 Gr.36?

A minimum preheat of 32°F (0°C) means no active preheating is needed above freezing conditions. Table 5.11 Category A at this thickness assigns the ambient minimum because A709 Gr.36 with non-low-hydrogen SMAW has sufficient ductility and low enough carbon equivalent that hydrogen cracking risk is minimal at this section thickness. Per footnote (a), if working below 32°F, preheat the joint to at least 70°F (20°C) and maintain during welding.

Other Steels with SMAW (non-low-hydrogen) at up to 3/4"

A709 Gr.36 with SMAW (non-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.

A709 Gr.36 Welding Guides