Abstract
Determination of long-term creep rupture properties for 316H steel is both costly and time-consuming and given the level of scatter in the data would need substantial number of tests to be performed. The primary objective of this study is to estimate the long-term creep properties of cross-weld (XW) and as-received (AR) 316H stainless steel by performing accelerated tests on pre-compressed (PC) material. In this work, uniaxial creep rupture tests have been performed on XW specimens and the results have been used to establish a correlation with accelerated test results on the PC material. Moreover, tensile tests have been performed on XW specimens at room temperature and 550 °C to examine the pre-conditioning effects on the mechanical response of the material. Similar power-law creep properties have been found for the creep strain rate and rupture time behaviour of the XW and PC specimens. It also has been found that the creep ductility data points obtained from XW and PC specimens fall upon the estimated trend for the AR material at 550 °C when the data are correlated with the applied stress normalised by 0.2% proof stress. The results show that the long-term creep properties of the XW and AR material can be estimated in much shorter time scales simply by performing tests on the PC material state.
Highlights
Type 316H austenitic stainless steel (SS) is widely used in the UK’s advanced gas cooled reactor (AGR) power stations
Experiments were performed on XW specimens extracted from an ex-service steam header to characterise the uniaxial creep properties of a 316H stainless steel welded component
The results show that the yield stress of the XW material is higher than the base metal both at room temperature and 550 °C, indicating that the material pre-straining has been introduced into the component during the welding process
Summary
Type 316H austenitic stainless steel (SS) is widely used in the UK’s advanced gas cooled reactor (AGR) power stations. As a consequence of operation at elevated temperatures, cracks have been repeatedly found in the heat affected zone (HAZ) of the thick-walled steam header welded components [2,3,4] This has been attributed to the creep deformation and crack growth driven by highly triaxial residual stresses [5, 6]. In order to account for the aging effects on the creep properties of the material, it is essential to quantitatively evaluate the creep deformation and rupture behaviour of the welded joints after exposure to service conditions at elevated temperatures This approach will result in realistic and accurate life predictions using the creep properties which describe the deformation and failure behaviour of aged steam headers
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