S355K2G1W Tensile Strength Explained

The basic number. S355K2G1W has a minimum tensile strength (Rm) of 470 MPa for thicknesses up to 100mm. The typical range falls between 470 and 630 MPa, depending on plate thickness and mill processing.

How tensile strength changes with thickness:

Up to 16mm: 470–630 MPa

16–40mm: 470–630 MPa (similar range)

40–100mm: 470–630 MPa, though actual values tend toward the lower half

Unlike yield strength, which drops noticeably as plates get thicker, tensile strength holds fairly steady. That's one reason thicker plates still offer good safety margins—they may yield a bit earlier, but they stretch and resist rupture almost as well as thin material.

Tensile vs. yield: the ratio matters. For S355K2G1W, the yield-to-tensile ratio typically runs around 0.75 to 0.85. A ratio that's too high (say, 0.95) means the steel gives little warning before breaking. A lower ratio means it stretches and deforms visibly first—giving you a clear visual alert before failure. S355K2G1W strikes a healthy balance.

Why this matters for weathering steel applications.

Bridges and cranes: Under rare overloads, the steel yields first (visible bending or sagging) rather than snapping without warning.

Earthquake zones: Higher tensile strength with good ductility allows structures to absorb energy.

Cold regions: Tensile properties remain reliable down to -20°C, matched with the K2 impact rating.

What the mill certificate shows. Look for "Rm" (tensile strength) on the test report. Actual values are typically 500–580 MPa for common thicknesses. If you see numbers below 470 MPa, reject the material. If you see values above 630 MPa, check whether the elongation still meets minimums—very high strength sometimes comes at the cost of ductility.

A practical takeaway. For most structural designs, meeting the minimum tensile strength is easy. But always verify the actual test values, especially for welded joints where the heat-affected zone might have slightly different properties than the base metal.