--- title: "Grade and classification of structural steel" subject: "Design of Steel and Timber Structure" chapter: 1 key: "semester_6/design_of_steel_and_timber_structure:grade-classification-structural-steel" source: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/grade-classification-structural-steel site: BCT Engineering --- # Grade and classification of structural steel Design of Steel and Timber Structure · Chapter 1: Steel Structures and their Analysis and Design - Asked in: 2072 Asoj, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/grade-classification-structural-steel - Whole chapter: https://www.bctengineer.com/md/semester_6/design_of_steel_and_timber_structure/chapter-1 ## Question Explain about grade and classification of structural steel as per Indian Standard. ## Short answer Grades per IS 2062 are designated E followed by minimum yield stress (e.g. E250, E350). Quality classes A, BR, B0, C denote impact toughness levels. Classification also includes deoxidation type (killed, semi-killed) and product shape (I-sections, channels, angles). ## Answer #### Structural steel as per IS 2062 / IS 800:2007 Structural steel is carbon or low-alloy steel (mainly iron with 0.15-0.25% carbon and manganese) rolled into plates, angles, channels and I-sections for use in construction. IS 800:2007 refers to IS 2062:2011 for hot-rolled steel. #### Grade Grade is expressed by the yield stress. In IS 2062:2011 steel is designated E (Engineering) followed by the minimum yield stress in N/mm², e.g. E250, E275, E300, E350, E410, E450, E550, E600. Earlier it was designated by ultimate stress, e.g. Fe410. | Grade | $f_y$ (N/mm², $t\le20$ mm) | $f_u$ (N/mm²) | |---|---|---| | E250 (Fe410) | 250 | 410 | | E275 | 275 | 430 | | E300 | 300 | 440 | | E350 (Fe490) | 350 | 490 | | E410 (Fe540) | 410 | 540 | | E450 (Fe570) | 450 | 570 | Yield strength reduces for thicker plates (20-40 mm, >40 mm). #### Quality classification Each grade is supplied in qualities A, BR, B0 and C, depending on deoxidation and notch toughness: A (semi-killed or killed, no impact test), BR (impact test at room temperature), B0 (impact test at 0 °C) and C (killed, impact test at −20 °C). Examples: E250 A, E250 BR, E250 C. #### Other IS classifications - By deoxidation: killed, semi-killed, rimmed. - By strength: mild steel (E250), high-tensile (E350-E450), and low-alloy steels. - By product: plates, bars, flats, angles (IS 808), channels, I-sections (ISMB, ISLB, ISWB, ISHB). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the designation E250 in IS 2062 indicate? A. Ultimate stress of 250 N/mm2 B. Minimum yield stress of 250 N/mm2 C. Modulus of elasticity 250 D. Thickness limit of 250 mm Answer: B. E stands for Engineering steel and the number is the minimum yield stress in N/mm2. (Key point: Meaning of E250) 2. E350 corresponds to which old designation, and what does the old number denote? A. Fe490, denoting ultimate stress B. Fe350, denoting yield stress C. Fe410, denoting ultimate stress D. Fe540, denoting yield stress Answer: A. E350 was Fe490 and the old Fe designation was based on ultimate stress. (Key point: Old vs new designation) 3. Which quality grade of a steel has no impact test? A. Quality C B. Quality BO C. Quality A D. Quality BR Answer: C. Quality A is supplied without an impact test; BR is tested at room temperature, BO at 0 deg C, and C at a specified low temperature. (Key point: Quality classification) 4. How does the yield strength of a plate change with thickness? A. Increases for thicker plates B. Reduces for thicker plates (20-40 mm, >40 mm) C. Does not change D. Depends only on the quality A/B/C Answer: B. The tabulated fy is for t <= 20 mm; thicker plates have lower yield strength. 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