ISO 9328-5:2018

Overview - ISO 9328-5:2018 (steel flat products for pressure purposes)

ISO 9328-5:2018 specifies technical delivery conditions for thermomechanically rolled, weldable fine grain steels used as flat products for pressure equipment (plates, strips). It is part of the ISO 9328 series and complements the general requirements of ISO 9328-1. The standard covers chemical composition, mechanical properties, delivery condition, inspection and testing requirements for grades listed in Annex A (European design codes) and Annex B (ASME-type design codes).
Key limitations: these steels are not suitable for hot forming, and elevated-temperature properties are not standardized - use at high temperature must be agreed between purchaser and manufacturer. Fine grain steels are defined as ferritic grain size 6 or finer (ISO 643).

Key topics and technical requirements

• Material scope and designation: Grades organized into series (basic, and low-temperature series down to −40 °C / −50 °C / −60 °C depending on annex). Designation follows ISO 9328-1.
• Delivery condition: Products supplied in the thermomechanically rolled condition.
• Chemical composition: Cast (heat) analysis and allowable deviations for product analysis are specified (see Tables A.1 and B.1). Option to agree carbon-equivalent values.
• Mechanical properties: Yield/tensile and impact requirements referenced in Annex Tables (A.3–A.4, B.3–B.4). Optionally a 40 J impact energy can be specified at certain temperatures.
• Weldability: Steels must be suitable for current welding processes; manufacturer can supply welding procedure data. Guidance on avoiding cold cracking and cautions about excessive post‑weld heat treatment (PWHT) affecting properties are included.
• Inspection & testing: Specifies types of inspection, sampling, tests (including impact testing direction for Annex B), and inspection certificates (example: certificate 3.1 per ISO 10474).
• Dimensions, surface condition, internal soundness: Requirements and tolerances aligned with ISO 9328-1.

Practical applications and users

Who uses ISO 9328-5:2018

• Steel producers and plate manufacturers (production, heat analysis, delivery).
• Purchasers and specifiers of pressure equipment materials (pressure vessels, boilers, piping, storage tanks).
• Welding engineers, fabricators and welding procedure qualification teams.
• Design engineers using European or ASME-type codes who need compatible material specifications.
• Inspection bodies and certification authorities verifying conformity and issuing inspection certificates.

Practical value

• Ensures consistent material quality for pressure purposes.
• Facilitates specification of weldable fine grain steels for low-temperature service.
• Supports procurement, testing, and welding procedure development with clear acceptance criteria.

Related standards

• ISO 9328-1 (general requirements)
• ISO 643 (ferritic grain size)
• ISO 10474 (inspection certificates)
• EN 1011-1 / EN 1011-2, IIS/IIW 382-71 (welding guidance)

Keywords: ISO 9328-5:2018, steel flat products, pressure purposes, thermomechanically rolled, weldable fine grain steels, delivery conditions, chemical composition, mechanical properties, weldability, ASME, European design codes.