Selecting Materials and Filler Metals for Commercial Shipbuilding

The core objective of commercial shipyards is to enable high volume production across a wide range of vessels, including barges, tugs, tankers, dredges, oil supply ships, support ships, and more. While the designs of these vessels are simpler than those of military ships, care must be taken throughout the welding operation to ensure the integrity and safety of the structures. Specifically, commercial shipbuilders in the United States must comply with requirements set by the American Bureau of Shipbuilding (ABS) or other governing bodies for welding operator certification, materials, and welding procedure specifications covering joint design, welding processes, techniques, and filler metals. All filler metals used in shipbuilding applications must be certified through rigorous testing and selected for the specific material. For many common materials, multiple options may be available.

Common Steels Used in Commercial Shipbuilding

ABS Grades AH36, DH36, and EH36 high-strength shipbuilding steels are among the most common materials used by commercial shipbuilders, with aluminum, stainless steel, and copper-nickel utilized for a variety of internal components.

AH36, DH36, and EH36 steels are known for their excellent weldability and toughness. All three feature an ultimate tensile strength of 71 to 90 ksi (490 to 620 MPa), a yield strength of 51 ksi (352 MPa), and an elongation of 21%. The key difference between the steels is the temperature at which they pass a Charpy V-notch impact test. AH36 is tested at 32°F (0°C); DH36 is tested at –4°F (–20°C); and EH36 is tested at –40°F (–40°C).

Welding Processes and Filler Metal Selection

Commercial shipbuilders use both AH36 and DH36 steel for building ship hulls, but they can also be used for upper decks and bulkheads on cargo and container ships, as well as tankers. When manually welded, both materials require a 70-ksi flux cored arc welding (FCAW) wire. Welding wires for shipbuilding applications carry designations that differ from those used in other applications, and several can be used to weld AH36 and DH36 steel. A filler metal with an ABS 3YSA H10 classification would be an option for welding these steels and is similar to AWS E71T-1C H8 or E71T-1M H8 wire. The ABS 3YSA H10 wires can be certified for use with either 100% CO₂ shielding gas or a 75% argon/25% CO₂ mix, operating on direct current electrode positive (DCEP). By ABS certifications, this filler metal can be used in all positions. For 0.045- and 0.052-in.-diameter wires, parameters range from approximately 170 to 250 A and 23 to 26 V. A 1/16-in.-diameter wire would also operate in a window of approximately 23 to 26 V but at higher amperage ranges of around 180 to 275 A.

For large panels, both AH36 and DH36 steel can also be welded using the submerged arc welding (SAW) process on a panel line coupled with a gantry system or subarc tractor. Commercial shipyards typically use a solid SAW wire, and one with an ABS 3YM classification is an option. The wire would be coupled with the filler-metal manufacturer’s recommended flux for that wire. The ABS 3YM-classified wire is similar to an AWS EM12K classification and operates between 200 and 900 A and 29 and 42 V, depending on the wire diameter, which ranges from 5/64 to 5/32 in.

Because of its low-temperature toughness, ABS EH36 steel is used for the construction of hulls for commercial vessels that will encounter severe, even Arctic, water temperatures. An ABS 4YSA H5 FCAW wire (similar to an AWS E71T-1CJ H8) is an option for welding with 100% CO₂ shielding gas in all positions and operates on DCEP. Welding with a 0.045- or 0.052-in.-diameter wire requires around 100 to 250 A, while a 1/16-in.-diameter wire operates between approximately 150 and 275 A. The voltages for all three diameters range from 23 to 27 V. Another wire option is an ABS 5Y400 H5 classification, which uses a 75% argon and 25% CO₂ shielding gas mixture and also operates on DCEP for all-position welding. It is like an AWS E71T-1MJ H4 FCAW wire and operates in an approximate range of 200 to 240 A and 25 to 26 V for 0.045- or 0.052- and 1/16-in.-diameter wires.

ABS EH36 steel can also be welded using the SAW process, especially for large plates, again with a panel line and gantry system or subarc tractor. An ABS 4YM classification solid wire would be suitable, as would an ABS 3YM solid wire. Cored or composite electrodes, such as ABS 4M H10 (similar to an AWS EC1 filler metal), are also an option for SAW of ABS EH36 steel. Among these options, the approved flux/wire combination determines low-temperature toughness, depending on whether it’s a neutral or active flux. Neutral fluxes will provide better overall mechanical properties.

Takeaways

The specific FCAW or SAW wires used to weld ABS AH36, DH36, and EH36 steel can vary by shipyard specifications for a given commercial vessel. Some may prefer to standardize their filler metal selection to simplify inventory, while others may look to achieve different mechanical properties for various ship components. Some commercial shipyards may also consider selecting a filler metal that provides good weldability and a wide operating window to help new operators achieve high-quality welds and reduce costly rework. Whichever the case, the aim is to construct commercial vessels that can withstand low temperatures while being safely operated.

This article was written by Matt Underwood (senior applications welding engineer at Hobart Brothers LLC, Troy, Ohio) and Ryan O’dell (corporate account manager at Miller Electric Mfg. LLC, Appleton, Wis.) for the American Welding Society.