What Is Grade S355 Steel
S355 is a high-strength low-alloy structural steel known for its high minimum yield strength of 355 MPa, good weldability, and durability. It is a versatile steel conforming to European standards, used widely in construction, heavy machinery, bridges, and offshore structures. The S designation means structural steel and 355 indicates the minimum yield strength in MPa.
Common Quality Grades
S355JR meets a minimum impact energy of 27 J at plus 20 degrees C; S355J0 meets 27 J at 0 degrees C; S355J2 meets 27 J at minus 20 degrees C; and S355K2 meets 40 J at minus 20 degrees C. The suffix indicates the impact toughness requirement and test temperature, allowing selection for the service climate.
Key Characteristics
High strength: the 355 MPa minimum yield allows lighter sections for the same load. Excellent weldability: S355 welds easily with conventional methods. High toughness: it maintains good impact resistance, especially at lower temperatures depending on the grade. Versatility: it serves a wide variety of structural applications.
Equivalents
ASTM A572 Grade 50 is often considered the American equivalent, as both are high-strength low-alloy steels with similar properties; Q355B is the Chinese equivalent; and DIN ST52-3 the former German designation. S355J2 is equivalent to Q345D in China per engineering practice, and ABS DH36 or EH36 can replace S355J2+N in marine applications.
S275 vs S355
S275 provides lower strength with an average minimum yield of 275 MPa but has good machinability and weldability. S355 offers 355 MPa minimum yield, about 30 percent more strength, allowing significant weight reduction in structures. The choice depends on the load requirements and cost targets.
A36 vs S355
A36 has a lower yield strength of about 250 MPa, while S355 starts at 355 MPa. S355 is stronger and follows European standards; A36 is a more general, lower-cost structural steel for less demanding scenarios. S355J2H additionally guarantees impact toughness at minus 20 degrees C, critical for cold-weather applications.
Frequently Asked Questions
Q: What is the yield strength of S355 steel?
A: 355 MPa minimum, with tensile strength of 470 to 630 MPa depending on thickness.
Q: What is the difference between S355JR and S355J2?
A: The impact test temperature: JR at plus 20 degrees C and J2 at minus 20 degrees C, both with 27 J minimum.
Q: What is S355 equivalent to?
A: ASTM A572 Grade 50, Q355B in China, and DIN ST52-3.
Q: Which is better, S275 or S355?
A: S355 for higher load capacity and weight reduction; S275 for lower cost where strength is sufficient.
Q: What does the H mean in S355J2H?
A: Hollow section profile per EN 10210 or EN 10219.
Q: Is S355 weldable?
A: Yes, excellent weldability with conventional welding methods.
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