Pressure Vessel Weldments Research Articles

Materials data for high-temperature design of ferritic steel pressure vessel weldments

To aid material selectors and engineering designers in the design of ferritic pressure vessel weldments, a data bank has been created of the creep deformation and rupture properties of weld materials and heat affected zone (HAZ) materials. The generated data are based on the properties of well-characterised typical materials and on information supplied by plant engineers. The presentation style allows the data to be used in materials selection at the earlier stages of design, or in Continuum Damage Mechanics based finite element analysis at the detailed design stage.

A determination of the benefits of annealing irradiated pressure vessel weldments

The long-term benefit of annealing an irradiated reactor pressure vessel steel may be described in terms of a benefit factor, B. The benefit factor compares the mechanical properties of an annealed and reirradiated specimen with an equivalent specimen having no intermediate anneal. The benefit factor was determined using a series of microhardness specimens prepared from nuclear pressure vessel surveillance program materials. These specimens were annealed and then reirradiated in a test reactor. There was an obvious long-term benefit in the specimens annealed at 450°C. The long-term benefit was less obvious at 400°C and no significant benefit was noted at 350°C. The benefit factor may also be used as the basis of a surveillance program for an annealed pressure vessel. A strategy for such a surveillance program is described.

Investigation methods for the detection and study of stress-relief cracking

The occurrence of grain boundary damage and stress-relief cracking within heat-affected zones of pressure vessel weldments and claddings has led to numerous investigations. The metallographic and fractographic as well as microanalytical methods used are reported in respect of the results obtained and the given limits. Within the range of microanalysis the application of the electron beam microprobe is described for the detection of micro segregations as well as companion elements and trace elements, Auger spectroscopy for the investigation of thin grain boundary films, transmission electron microscopy especially for the identification of precipitations, and the photoemission electron microscope for the analysis of transformation and precipitation behaviour, as well as the so-called phase analysis for better knowledge in the field of kinetics of phases. Using the results of these methods, which were applied on real welded joints as well as on weld simulation tests, it was possible to prove the validity of the chosen parameters for the welding simulation. Further efforts will be made to find more clear correlations between the contents of alloying elements in the base material and the precipitation or crack behaviour in the coarse grain zone of the HAZ.

Assessing heat-affected zone properties of pressure vessel weldments using simulation techniques

This paper describes simulation methods for mechanisms occurring in the coarse grain heat affected zone (HAZ) of thick-walled weldments. The simulation process is divided into overheating simulation and simulation of stress-relief heat treatment. Overheating simulation is mainly practised by inductive or conductive heating and produces an HAZ-representative microstructure. For the stress-relief heat treatment simulation, annealing tests and constant load creep tests at stress-relief temperatures are carried out. Classifications in order of crack sensitivity and service-suitability are proposed. The order of crack sensitivity is derived from the magnitude of deformability and creep resistance in constant load creep tests. The order of service-suitability is based on the results of notch-impact tests (ISO-V) and tensile tests subsequent to both simulation treatments. The techniques are demonstrated on an example of an ASTM A 508 CI 2 (22 NiMoCr 37) plate material.

Ultrasonic/radiographic examination of heavy-wall pressure vessel weldments: Center, D.E., Roehrs, R.J., materials evaluation, vol 27, no 5 (May 1969) pp 107–117

Ultrasonic/radiographic examination of heavy-wall pressure vessel weldments: Center, D.E., Roehrs, R.J., materials evaluation, vol 27, no 5 (May 1969) pp 107–117