Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Guidelines for the de-hydrogenation of low alloy welds

During fabrication and repair in service, pressure vessels are submitted to various Intermediate Stress Relieving (ISR) and Post Weld Heat Treatments (PWHT) following requirements proposed by construction codes.

In some cases these requirements have appeared too stringent (ISR in place of Dehydrogenation Treatment DHT) or on the contrary too imprecise.

The determination of optimised Heat Treatment conditions depends on the purpose of this treatment and therefore on the dehydrogenation, the tempering and the stress relieving behaviour of the materials to be concerned.

It has been shown that DHT is able to remove hydrogen almost completely for the CrMo steels but not for the CrMoV steels. ISR soacking temperature can be slightly decreased allowing keeping good impact strength even after several ISR.

Besides mechanical characterisation, numerical simulation has been used for the determination of hydrogen behaviour and the evolution of residual stresses.

A guideline for optimising ISR for the heat resisting steels has been issued as a project deliverable to help applying the optimised procedures.

Dissemination of the results:
- Hungarian Seminar - Miskolc (Hungary) -23rd of June 2004.
- ESOPE 2004 (International conference on pressure vessels)- Paris (France) - 28th to 30th of September 2004.
- General assembly of Systus’ users - Paris (France) - 11th of October 2004.
- Soudage et Techniques Connexes - the French Technical review on welded construction - To be published.
- PVP 2005 - Denver (USA) - 17th to 21st of July 2005.

Reported by

Institut de soudure
PARIS NORD II, 90 rue des Vanesses
53420 Villepinte
France
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