Safe use of duplex stainless steel weldments at elevated temperatures

Purpose and goal:

Extension of the guidelines for safe use of duplex stainless steel in the range 275-350 °C to also include welded structures.

Assess the physical origin of the increased rate of embrittlement of welds compared to base material and investigate possible ways to mitigate this problem.

Development of testing procedure for fracture mechanical testing that will allow lifetime predictions of duplex stainless steels at elevated temperatures, including welds.

Provide data as input to revision of standards pertaining to maximum service temperatures of duplex stainless steel grades. Expected results and effects:

This project will provide experimental results on how the structural integrity of duplex stainless steel welds is affected with time and temperature. The data can be used in fitness for risk assessment for new equipment or for service evaluation of existing equipment, ensuring sustainable use of material to prevent scrapping a fully functional material. Data will also be provided for revision of standards pertaining to maximum service temperatures of duplex stainless steel grades.

Approach and implementation:

The project will be run by a committee with representatives from the project participants and with reporting to a steering committee from Jernkontoret. The work is divided in two phases, phase 1 comprising gathering of long-term heat-treated materials and specimens from previous projects and from the industry. Phase 2 comprises structural integrity testing, a study of the embrittlement mechanisms, gathering of industrial experience and a work package with dissemination & management.