A106 Gr.B Preheat for SAW — over 2-1/2"

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 pipe joints is limited to rotated butt welds in the flat position. For large-diameter pipe (24" and above), tandem SAW with two wires provides fill rates exceeding 25 lb/hr. The submerged arc conceals the weld pool entirely, so joint tracking relies on seam-finding sensors or pre-marked centerlines.

SAW Tips for Pipe and Tube Steels

For A106 Grade B seamless pipe (35 ksi yield, high-temperature service), SAW handles roll-welded shop fabrication of heavy-wall process piping manifolds and header assemblies in the flat position. Use 3/32" EM12K wire at 450–550 A with neutral flux for multi-pass joints on Schedule 80 and heavier walls. The all-seamless construction of A106 eliminates HAZ interaction with a longitudinal ERW seam.

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

Why SAW for A106 Gr.B at over 2-1/2"

Why SAW for A106 Gr.B at over 2-1/2"? SAW delivers 15-40 lb/hr deposition — the highest deposition rate among available processes. Position capability: flat and horizontal only. Suitability: shop only.

A106 Gr.B

ASTM A106 Grade B covers seamless carbon steel pipe for high-temperature service up to about 750°F, with 35 ksi minimum yield and 60 ksi minimum tensile strength. Produced in sizes from 1/4" through 30" NPS, it is the standard pipe material for power plants, refineries, and process piping where elevated temperature and pressure coexist. Chemistry limits (0.30% max carbon, 0.29-1.06% manganese) give it a weldability profile that matches common structural grades with Category A and B preheat requirements. A106 is exclusively seamless, which eliminates the ERW seam concern present in A53. Grade C (40 ksi yield) exists but Grade B handles the vast majority of process piping service.

Why This Preheat for A106 Gr.B with SAW

Seamless pipe rated for high-temperature service up to 750°F. With low-hydrogen SAW, this combination falls under Category B rather than Category A — the submerged arc process with granular flux produces controlled hydrogen levels, with flux condition being the primary variable. The 225°F minimum preheat is lower than what non-low-hydrogen SMAW would require at the same thickness because SAW significantly reduces the driving force for hydrogen-induced cracking in the heat-affected zone.

Typical Applications for A106 Gr.B

Used in boiler steam headers, refinery piping racks, process plant branch connections, heat exchanger nozzle welds, power plant main steam lines, petrochemical reactor feed piping, and high-temperature manifolds. A106 Gr.B butt welds in process piping require joint preparation to B31.1 (power piping) or B31.3 (process piping) depending on service classification. Socket welds on small-bore A106 drain lines and instrument take-offs are common in utility stations, typically 1/2" to 2" NPS. Typical wall thicknesses range from Schedule 40 (0.237" wall on 2" NPS) to Schedule 160 (0.500" wall on 4" NPS) in critical high-energy service. Weld procedure qualification often includes side bend tests and tensile tests specific to the pipe diameter and wall thickness being joined. Field welds at pipe-to-flange connections and valve set-on joints require portable preheating equipment when wall thickness exceeds 1/2".

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.

Other Steels with SAW at over 2-1/2"

A106 Gr.B 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.

A106 Gr.B Welding Guides