ISO 9329-2:1997

Overview

ISO 9329-2:1997 - "Seamless steel tubes for pressure purposes - Technical delivery conditions - Part 2: Unalloyed and alloyed steels with specified elevated temperature properties" - specifies technical delivery requirements for seamless circular steel tubes intended for elevated-temperature pressure piping (e.g., steam generators and interconnecting pipework). It replaces ISO 2604‑2:1975 and forms part of the ISO 9329 series covering tubes for pressure purposes.

Key topics and requirements

• Scope and applicability: Covers seamless tubes of circular cross-section; can be used as a basis for non‑circular sections by agreement. Intended where material is exposed to elevated temperatures.
• Steel grades and chemical composition: Defines unalloyed and alloyed steel grades (examples in the standard include PH 23, PH 26, PH 29, PH 35, CrMo grades, 11CrMo, 13CrMo, 16Mo3, etc.) and requires heat (heat analysis) and product (check) analyses with permissible deviations.
• Delivery condition and heat treatment: Specifies required heat treatments over full tube length - e.g., normalizing, normalizing & tempering, isothermal annealing or full annealing - and notes exceptions where manufacturing gives an equivalent condition.
• Mechanical properties at room and elevated temperature: Requires tensile, proof stress and other mechanical property tests; long‑term stress‑rupture values at elevated temperature are provided (Annex A for information).
• Dimensions, tolerances and marking: References dimensional standards and tolerance systems; includes marking, protection and documentation requirements.
• Inspection and testing: Defines inspection categories and testing (hydraulic, ultrasonic, flattening, tensile, impact where applicable), and links to inspection certificates (e.g., inspection certificate 3.1.B per ISO 10474).
• Weldability and fabrication notes: States steels covered are regarded as weldable and cautions on air hardening of some ferritic steels (requiring post‑weld heat treatment as appropriate).

Practical applications

• Specification and procurement of seamless steel tubes for elevated‑temperature pressure piping in power plants, boilers, superheaters, heat exchangers and industrial steam systems.
• Design and manufacturing guidance for pressure piping engineers, boiler makers, fabricators and tube manufacturers to ensure tubes meet specified metallurgical and mechanical performance at elevated temperatures.
• Quality control and inspection planning for material inspectors and purchasing departments when requiring traceable heat/product analysis and test certificates.

Who uses this standard

• Steel tube manufacturers and mill test laboratories
• Pipe and pressure equipment designers and fabricators
• Plant engineers (power, petrochemical, process industries)
• Procurement, quality assurance and inspection bodies

Related standards

• ISO 404 - General technical delivery requirements for steel
• ISO 10474 - Inspection documents and certificates (e.g., 3.1.B)
• ISO 4200 - Dimensions and masses for plain end steel tubes
• ISO 9302 / ISO 9303 / ISO 9305 - Ultrasonic and electromagnetic testing for pressure tubes
• ISO/R 831 / ISO 5730 - Rules for construction of boilers and stationary shell boilers

Keywords: ISO 9329-2:1997, seamless steel tubes, elevated temperature properties, pressure piping, technical delivery conditions, steel grades, heat treatment, inspection and testing, weldability, material specification.