ISO 630-4:2021

Overview - ISO 630-4:2021 (Structural steels, high-yield quenched & tempered)

ISO 630-4:2021 specifies technical delivery conditions for high yield strength quenched and tempered structural steel plates and wide flats. It applies to hot-rolled flat products (minimum nominal thickness 3 mm) intended for welded or bolted structures and rolled on a reversing mill. The standard covers 10 steel grades organized in two normative annexes and five impact-related qualities (A, C, D, E, F).

Key topics and technical requirements

• Grades and qualities
  • Annex A: S460Q, S500Q, S550Q, S620Q, S690Q, S890Q, S960Q.
  • Annex B: SG460Q, SG500Q, SG700Q.
  • Qualities: A (no impact test), C (0 °C), D (−20 °C), E (−40 °C), F (−60 °C).
• Thickness ranges
  • Typical max nominal thicknesses differ by grade (e.g., up to 200 mm for many Annex A grades; lower maxima for very-high-strength grades and Annex B grades). (See standard for exact limits by grade.)
• Delivery condition
  • Products are supplied in the quenched and tempered condition; steels are fully killed, fine-grain and contain sufficient nitrogen-binding elements.
• Chemical composition and carbon equivalent
  • Heat and product analysis requirements are specified in the annexes; maximum Carbon Equivalent Value (CEV) limits are required (CEV formula and details referenced in ISO 630-1).
• Mechanical properties
  • Tensile properties at room temperature and Charpy V‑notch impact requirements (orientation predominantly longitudinal; transverse by agreement) are defined per grade/quality.
• Inspection, testing and sampling
  • Verification is by heat. Annex A test unit: by heat (60 tonnes or part thereof). Annex B: test unit per plate/wide flat as heat treated.
• Marking, surface condition, dimensions
  • Referenced to ISO 630-1 for marking, surface condition, internal soundness, tolerances and test methods.

Practical applications and users

ISO 630-4 is used by:

• Steel manufacturers and mills producing quenched and tempered plates and wide flats.
• Procurement teams specifying material for bridges, heavy buildings, cranes, offshore structures and other welded/bolted steelwork where high yield strength is required.
• Structural engineers, fabricators and welders who need certified material properties (tensile, impact) and traceability for design and fabrication.
• Quality and inspection bodies for conformity assessment and batch testing.

Benefits:

• Ensures consistent mechanical performance, weldability and toughness.
• Facilitates international procurement and interchangeability of high-strength structural steels.

Related standards

• ISO 630-1 - General technical delivery conditions for hot‑rolled products (normative reference).
• ISO 4885 and other ISO/TC 17 publications for related terminology, tests and product families.

Keywords: ISO 630-4, structural steels, quenched and tempered, high yield strength, steel plates, wide flats, Charpy V-notch, tensile properties, chemical composition, delivery conditions.