Suitability of size adjustment in impact toughness transition region for sub-sized ferritic stainless steel Charpy-V results

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>In this paper, it is examined whether SINTAP/FITNET size adjustment formula can be reliably used for two 11% Cr utility ferritic stainless steels in order to derive safe, yet not overly conservative T_28J transition temperature estimates. Charpy-V notched specimens were machined into five thicknesses and the T35_J/cm² transition temperatures were determined using hyperbolic tangent fitting function. The transition temperatures were then compared against the ideal size adjustment given by the formula. Microstructural characterization and fractographic examinations were carried out using laser confocal and scanning electronmicroscopy.</p><p>It is seen that the size adjustment formula only partially satisfied the examined steels. Specifically, the specimens in 6–10 mm thickness range had little or no change in the transition temperatures and the projected size adjustment did not meet the actual results in these cases. To some extent, extensive splitting/delamination that occurred with steel A in the transition region could have affected the correlation, but it did not affect the results with steel B. Average grain sizes were relatively similar and uniform in the two examined steels through-thickness, but finer 90^th percentile grain size and lower interstitial content in steel B was thought to be responsible for improved toughness over steel A.</p></div>