Overview
CEN ISO/TR 14745:2015 - Welding: Post-weld heat treatment parameters for steels provides practical recommendations for post-weld heat treatment (PWHT) of steels. The technical report defines holding temperatures, holding times and key process parameters (including the Hollomon–Jaffe parameter) for stress relieving and tempering of specific steel groups. Its guidance is independent of product type or location but does not prescribe when PWHT is required - those requirements remain in product standards, material specifications or supplier data sheets.
Key topics and requirements
- Scope and limit: Recommendations are limited to stress relieving for non‑alloy steels (groups 1, 2, 3, 4 and 11) and tempering for Cr‑Mo‑(Ni) steels (groups 5, 6) and martensitic stainless steels (group 7.2).
- Table of PWHT parameters: Table 1 gives holding temperature ranges and holding times for different material groups and thicknesses. It also introduces a critical Hollomon–Jaffe parameter (Pcrit) to account for cumulative tempering effects.
- Heating and cooling control: PWHT may be performed in a furnace or by local heating (induction/resistance). Temperature uniformity limits are specified: for temperatures up to 500 °C the variation must not exceed 150 °C within 4 500 mm; above 500 °C the variation must not exceed 100 °C.
- Procedure, equipment and records: PWHT must follow a written procedure. Equipment should meet ISO 17663 requirements for temperature control and uniformity. Manufacturers should record holding temperature, holding time, and heating/cooling rates.
- Thickness rules for welded joints: Rules are provided to determine which thickness governs holding-time calculations (e.g., thickest part for butt welds, throat thickness for fillet welds, nozzle/plate thickness for nozzle welds).
- Limitations and cautions: Upper-range PWHT conditions may degrade yield strength, tensile strength or toughness. Material supplier guidance (e.g., thermo‑mechanically treated fine‑grain steels) takes precedence.
Practical applications
- Use this report to select PWHT holding temperatures and times when preparing welding procedures, qualification tests, or production heat‑treatment plans.
- Applicable in industries where weld integrity and residual stress control matter: pressure vessels, piping, petrochemical, power generation, heavy fabrication and pipeline construction.
- Supports welding engineers, procedure writers, fabricators, QA/QC inspectors and materials engineers in defining safe and repeatable PWHT cycles.
Related standards
- EN 10052 - Vocabulary of heat treatment terms for ferrous products
- ISO 17663 - Methods and equipment for PWHT (temperature control and uniformity)
- ISO/TR 15608 and ISO 4885 - referenced for material grouping and heat‑treatment definitions
Keywords: post‑weld heat treatment, PWHT parameters, holding temperature, holding time, stress relieving, tempering, Hollomon–Jaffe, ISO/TR 14745:2015, welding procedure.