Difference between S420G1+QT and S420G2+QT steel plate

S420G1+QT is a high-strength offshore structural steel plate certified under EN 10225 for fixed offshore structures, oil/gas platforms, and wind turbine foundations . The "+QT" suffix indicates the quenched and tempered delivery condition, which provides an excellent combination of high strength and toughness through heat treatment . It has a minimum yield strength of 420 MPa (for thickness ≤16mm) and tensile strength ranging from 500 to 660 MPa, with a minimum elongation of 19% . The chemical composition is strictly controlled with carbon ≤0.14%, manganese ≤1.65%, and sulfur ≤0.010% . Maximum plate thickness is 100 mm . Impact toughness is tested at -40°C with a minimum energy requirement of 60 Joules .

S420G2+QT is also a quenched and tempered offshore structural steel certified under EN 10225, sharing the same minimum yield strength of 420 MPa and tensile strength range of 500-660 MPa as G1 . However, S420G2+QT offers stricter chemical composition controls, featuring a lower sulfur limit of ≤0.007% (compared to ≤0.010% for G1) . The higher "G" number (G2 vs. G1) signifies more stringent requirements for purity and toughness. Like G1, it is impact tested at -40°C with a minimum energy requirement of 60 Joules . Maximum plate thickness is also 100 mm .

Both S420G1+QT and S420G2+QT are EN 10225-certified quenched and tempered offshore structural steels with identical mechanical properties (minimum yield 420 MPa, tensile 500-660 MPa) and impact requirements (-40°C, 60J) . Their primary difference lies in chemical purity: S420G1+QT is suitable for general offshore applications, while S420G2+QT features stricter limits on sulfur (≤0.007%), offering enhanced low-temperature toughness and weldability for more demanding offshore structures . Both grades maintain excellent weldability and corrosion resistance, making them ideal for offshore platforms, shipbuilding, and subsea pipelines . The selection between them depends on whether the project requires standard offshore performance (G1) or enhanced purity and toughness for critical applications (G2).

Mechnical property for S420G1+QT steel plate:
 

Mechnical property for S420G2+QT steel plate:
 

Chemical composition for S420G1+QT steel plate 
 

Chemical composition for S420G2+QT steel plate