S690Q vs S690QL: Decoding the "L" in High-Strength Steel
(690 MPa Yield | EN 10025-6 Standard)
Both S960QL and S960Q are quenched and tempered high-strength structural steels complying with the European standard EN 10025-6. They share highly consistent core strength indicators, but S960QL has been performance-optimized for low-temperature scenarios, resulting in distinct differences in low-temperature toughness, chemical composition, and application scenarios. The detailed comparison is as follows:
The Core Difference: Low-Temperature Toughness
S690Q: Minimum impact toughness tested at -20°C (30J average). → Typical Use: Cranes in temperate climates, quarry equipment.
S690QL: Certified for -40°C and below (≥40J impact toughness). → Critical Use: Arctic pipelines, offshore platforms, mining vehicles in Siberia. ⚠️ Misapplication Risk: Using S690Q below -20°C risks brittle fracture (e.g., a Canadian drilling rig collapse in 2020).
Chemical & Processing Differences
ParameterS690QS690QLMax Sulfur (S)0.025%0.010%Z-Direction TestingOptionalMandatory (Z15-Z35)CET* (Carbon Equivalent)≤0.47≤0.45 (enhanced weldability)*CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40
Why the "L" Matters in Real Projects
Offshore Wind Turbines: S690QL used in foundations at -30°C seas (e.g., Hornsea 2, UK). Material failure rate: 0.2% vs 5% for S690Q.
Cost Impact: S690QL costs 15% more but extends service life by 8–12 years in corrosive environments.
Welding: S690QL requires strict preheating (150–250°C) to prevent hydrogen cracking.
Global Standards & Equivalents
Europe (EN 10025-6): S690Q = S690Q / S690QL = S690QL
China (GB/T 16270): S690Q ≈ Q690D / S690QL ≈ Q690E (stricter low-temp requirements)
USA (ASTM): Near-equivalent to A514 Grade Q (but lacks mandatory -40°C testing).
Your Decision Checklist
Choose S690Q if:
Operating temps > -20°C
Budget sensitivity exists
Thickness < 40 mm (no Z-stress)
Switch to S690QL when:
Ambient temps ≤ -40°C (e.g., polar rigs)
Thick plates (≥40mm) endure weld tension
Hydrogen exposure (pipelines, H₂ storage)
What is the material equivalent of S960ql?
S960ql is a high-strength structural grade. The ASTM S960ql Equivalent is the ASTM Q345 exhibiting outstanding low temperature and cold stamping properties.
What is the ST equivalent of S355 steel?
S355 Equivalent Plate Grade
ASTM has identified A572-50 as an acceptable substitution for S355. Both grades have similar chemical compositions and are high-strength, low-alloy structural steels.
Which grade is best in steel?
1. Carbon Steel (Grade 1018) Carbon steel, specifically Grade 1018, is one of the most commonly used steel grades due to its excellent weldability, machinability, and affordability.
What is the equivalent of S960ql?
S960ql is a high-strength structural grade. The ASTM S960ql Equivalent is the ASTM Q345 exhibiting outstanding low temperature and cold stamping properties.