Introduction
This article explains the heat resistance of S350GD galvanized steel and its temperature limits. The S220GD to S550GD grades are continuously hot-dip galvanized structural steels defined in EN 10346, where the number states the minimum yield strength in megapascals. They are specified for load-bearing profiles, purlins, structural sections and steel frames that must carry mechanical loads in addition to resisting corrosion.
Grade System
The designation combines the S for structural steel with the minimum yield strength and the GD for the continuously galvanized product, for example S250GD with 250 MPa minimum yield strength. The series extends from S220GD for lightly loaded sections to S550GD for high-strength members, and the mechanical properties are guaranteed for the stated coating and thickness range.
Mechanical Properties
Yield strength, tensile strength and elongation vary with the grade and the thickness. The higher grades achieve their strength through chemistry and processing, which allows thinner, lighter sections to carry the same load, reducing material cost and structure weight.
| Grade | Yield MPa Min | Tensile MPa | Typical Use |
|---|---|---|---|
| S250GD | 250 | 330 - 430 | Purlins, light framing |
| S280GD | 280 | 360 - 440 | Structural sections |
| S320GD | 320 | 390 - 470 | Frames, racks |
| S350GD | 350 | 420 - 520 | Heavy framing |
| S550GD | 550 | 560 - 700 | High-strength members |
Coating and Durability
Structural grades are supplied with zinc coatings from about Z200 to Z600 depending on the exposure, and the coating protects the steel from corrosion during the service life of the structure. Heavy coatings are used for outdoor and industrial environments, and the spangle and surface treatment are specified for the intended finish.
Applications
Typical uses are purlins and girts, structural framing, roof and wall cladding systems, storage racks, solar mounting structures, agricultural buildings and industrial plant. The grade and coating are selected by the load, the environment and the required design life.
Verification
Check the grade, yield and tensile values, coating mass and dimensions on the mill certificate, and verify the bend test requirement for the forming process before acceptance.
