Indian standard - IS 1161 YST 210, 240 AND 310

IS 1161 is the definitive Indian Standard for steel tubes used in structural engineering, covering hot-finished seamless and electric resistance welded (ERW) pipes. The classification system centers on the Yield Strength of the Tube (YST), where the numerical values 210, 240, and 310 represent the minimum yield stress in megapascals ($MPa$). YST 210 is the standard utility grade, offering high ductility and ease of fabrication for general frameworks and lightweight structures. YST 240 serves as a versatile middle ground, balancing increased load-bearing capacity with reliable weldability, making it a staple for industrial sheds and scaffolding. For heavy-duty applications requiring maximum structural integrity, YST 310 provides the highest tensile strength, allowing for thinner-walled tubes that maintain high resistance to deformation, which is critical for large-scale space frames and infrastructure projects.