1. Yield Strength (ReH)
Yield strength is the stress at which a material begins to deform plastically. For ABS steels, minimum yield strength values are grade-dependent:
Grade A: ≥235 MPa (general-purpose plates).
AH36: ≥355 MPa (high-strength for hulls).
EH40: ≥390 MPa (arctic/ice-class vessels).
ABS mandates tensile testing (per ASTM A370) on samples cut transversely from plates. The yield point must be clearly defined, as discontinuous yielding (e.g., in thermo-mechanically rolled steels) requires alternative measurement methods (e.g., 0.2% offset). Higher grades (e.g., FH460) may require through-thickness testing (Z-direction) to prevent lamellar tearing in thick plates. Environmental factors (e.g., saline corrosion) may further influence design yield strengths to account for long-term degradation.
2. Tensile Strength (Rm)
Tensile strength defines the maximum stress a material can withstand before breaking. ABS specifies ranges to balance strength and ductility:
Grade A: 400–520 MPa.
EH36: 490–620 MPa.
Overly high tensile strength can compromise weldability, so ABS limits carbon equivalents (CEV) for grades above AH32 (typically CEV ≤0.43%). Testing involves pulling specimens until fracture and measuring elongation simultaneously. For quenched and tempered (Q&T) steels (e.g., EH47), tensile properties must be uniform across the plate thickness, verified via multiple layer testing.
3. Elongation at Fracture (%)
Elongation measures ductility, critical for absorbing dynamic loads (e.g., waves, collisions). ABS requires:
Grade A: ≥22% (50mm gauge length).
Higher grades (e.g., DH36): ≥21%.
Testing follows ASTM E8, with results sensitive to specimen geometry (e.g., proportional vs. non-proportional). For high-strength steels, elongation may decrease slightly, but ABS compensates by requiring stricter impact toughness. Ductility is also linked to microstructure control-fine-grained steels (achieved via Al-Nb-V microalloying) often exhibit superior elongation.
4. Charpy V-Notch Impact Toughness
ABS mandates minimum energy absorption at operational temperatures:
Grade A: Not required (ambient temperature use).
Grade D: ≥27J at –20°C.
EH36: ≥34J at –40°C (for polar routes).
Testing follows ASTM A370, with three specimens tested per batch. For thick plates (>50mm), ABS may require sub-surface testing to ensure homogeneity. Steels for LNG carriers (e.g., 9% Ni steel) have stricter criteria (e.g., ≥60J at –196°C). Low toughness can lead to brittle fracture, so ABS enforces heat treatment controls (e.g., normalizing for Grade D).
5. Bend Test Performance
Bend tests evaluate formability and surface integrity:
Grade A: 180° bend with mandrel diameter = 2× thickness.
Higher grades (e.g., EH40): May require tighter bends (e.g., mandrel = 3× thickness).
Cracks or delaminations during bending disqualify the plate. ABS permits guided-bend tests for weld qualification, simulating real-world stresses. For thermomechanical rolled (TMCP) steels, bendability depends on controlled cooling rates to avoid excessive hardness. Specialized grades (e.g., corrosion-resistant CR steels) may undergo reverse-bend testing.
