Q690D (GB/T 1591) is an ultra-high-strength low-alloy round steel with a chemistry engineered for extreme loads: 0.12–0.20% C, 1.00–1.60% Mn, 0.50–1.00% Cr, 0.20–0.50% Mo, and 0.02–0.20% Ti (for grain refinement).
This composition delivers 690 MPa minimum yield strength and 770–940 MPa tensile strength, with -20°C impact toughness ≥34 J-critical for heavy machinery operating in cold climates. Q690D is used in crane booms, mining shovel arms, and offshore platform legs, where its high strength reduces weight by 30% compared to Q355. It is China's equivalent to ASTM A514 Grade Q and EN 10025-6 S690QL, with Made-in-China listings highlighting its role in "Mega Machinery Components."