What Is S420N Steel
S420N is a high-strength low-alloy structural steel plate specified in EN 10025-3, the European standard for weldable fine-grain structural steels in the normalized condition. The designation indicates a minimum yield strength of 420 MPa, and the N quality requires impact testing at minus 20 degrees C. Fine-grain processing with controlled microalloying gives the grade an excellent combination of strength and toughness.
Chemical Composition
Heat analysis limits are carbon 0.20 percent, silicon 0.60 percent, manganese 1.00 to 1.70 percent, nickel 0.80 percent, phosphorus 0.030 percent, sulfur 0.025 percent, chromium 0.30 percent, molybdenum 0.10 percent, vanadium 0.20 percent, nitrogen 0.025 percent, niobium 0.05 percent, titanium 0.05 percent, aluminum 0.02 percent minimum, and copper 0.55 percent, with a maximum carbon equivalent of 0.52 percent.
Mechanical Properties
The minimum yield strength is 420 MPa for thicknesses up to 16 mm, 400 MPa for 16 to 40 mm, 390 MPa for 40 to 63 mm, 370 MPa for 63 to 80 mm, 360 MPa for 80 to 100 mm, 340 MPa for 100 to 150 mm, 330 MPa for 150 to 200 mm, and 320 MPa for 200 to 250 mm. The tensile strength is 520 to 680 MPa up to 100 mm thickness and 500 to 650 MPa above, with a minimum elongation of 19 percent for thinner sections and 18 percent for thicker ones.
Impact Toughness
The N quality guarantees 40 J minimum impact energy at minus 20 degrees C in the longitudinal direction and 27 J transverse. Higher energy values are guaranteed at warmer temperatures, for example 47 J at 0 degrees C and 55 J at plus 20 degrees C longitudinal, making the grade suitable for cold-climate structures.
Applications
S420N is used for large ship structural parts such as keels and ribs, highway and railway bridges, load-bearing structures of power stations, medium and high pressure boilers, pressure vessels, crane structures, and heavy machinery frames where high strength reduces section size and dead weight.
Fabrication Notes
The plate has good weldability by arc, gas, and submerged arc processes. Preheat requirements depend on thickness and restraint, and the carbon equivalent should be used to determine the minimum preheat. The material forms well both cold and hot and can be flame cut, laser cut, and plasma cut without special procedures.
Frequently Asked Questions
Q: What standard specifies S420N?
A: EN 10025-3 for normalized weldable fine-grain structural steels.
Q: What is the yield strength of S420N?
A: 420 MPa minimum for thicknesses up to 16 mm.
Q: What does the N mean?
A: Normalized delivery condition with impact testing at minus 20 degrees C.
Q: Is S420N weldable?
A: Yes, with procedures based on thickness and carbon equivalent.
Q: What applications use S420N?
A: Ships, bridges, power station structures, pressure vessels, and crane structures.
Q: What thicknesses are available?
A: From 3 mm up to 250 mm depending on mill capability.
Contact us for S420N plate quotations, including thickness bands, impact requirements, and delivery schedules.