Answer
High Tensile Steel (HTS)—often referred to as high tensile carbon-manganese steel—is used in ship construction primarily to optimize the strength-to-weight ratio of the hull structure. While mild steel remains the primary material for vessel construction, HTS is strategically incorporated in areas subjected to high structural stress.
Key Technical Drivers for Using High Tensile Steel
Weight Reduction & Increased Payload Capacity: Because HTS has a higher yield strength (≈315 to 390 N/mm2) compared to standard mild steel (≈235 N/mm2), classification rules (such as IACS, ABS, DNV, and Lloyd's Register) permit a reduction in plate thickness (t). Reduced steel weight directly lowers lightweight displacement, increasing deadweight carrying capacity and lowering fuel consumption.
Handling High Longitudinal Bending Moments: When a vessel experiences longitudinal bending (hogging and sagging in high seas), maximum tensile and compressive stresses occur at the structural members furthest from the neutral axis. HTS is extensively fitted in:
Strength Deck Plating & Deck Strakes (sheer strake, deck stringer plate).
Bottom Shell Plating & Keel Members (flat plate keel, bottom plating, bilge strake).
Hatch Coamings & Topside Tanks on bulk carriers and container ships.
Managing High Localized Stress Concentrations: HTS is specified in areas subjected to cyclic loads, localized fatigue, or high impact, including container hatch corners, heavy cargo hold boundaries, bulkheads, and engine room bedplate foundations.