JIS SS490 vs SS400 Steel Plate: Which Grade Should You Choose?

SS490 and SS400 are structural steel grades specified in JIS G 3101. Both are used in general steel structures and engineering applications, but they differ in their specified strength requirements. Understanding these differences helps buyers select the appropriate material for their projects.

The main distinction is the strength level. SS400 has a specified tensile strength range generally associated with conventional structural steel, while SS490 has a higher specified tensile strength requirement. The applicable yield strength requirements also depend on the standard and plate thickness. Buyers should therefore check the relevant JIS requirements rather than assuming that every mechanical property increases by the same proportion.

SS400 is often suitable for general structural applications where its specified properties meet the design requirements. Typical uses include building components, brackets, frames, and general fabrication. It may be an economical choice when the project does not require the higher strength level associated with SS490.

SS490 may be preferred when the design calls for higher tensile strength. It can be considered for selected load-bearing structures, industrial equipment components, and engineering projects, provided that the material meets the applicable design and fabrication requirements.

However, choosing SS490 does not automatically make a structure safer or more economical. The final selection should consider design loads, plate thickness, weldability, fabrication procedures, material availability, and total project cost. Higher-strength material may not provide a practical benefit if the engineering design does not require it.

International buyers should also be careful when comparing SS490 and SS400 with grades under ASTM, EN, or other standards. Similar strength values alone do not establish full equivalence in chemistry, testing, delivery condition, or certification.

The best choice is the grade that satisfies the project's technical specification at the lowest overall cost. Before purchasing, confirm the required JIS grade, dimensions, quantity, inspection requirements, and mill test certificate with the supplier.