Difference in Mechanical Properties and Microstructure of SA 508 CL.3 Reactor Pressure Vessel Steels Manufactured by Different Steel Refining Process

摘要

Three kinds of SA 508 Cl.3 reactor pressure vessel steels were examined to evaluate the effect of differences in steel refining practice on the microstructure and mechanical properties. The three refining processes were vacuum carbon deoxidation (VCD), vaccum carbon deoxidation plus aluminumkilled (VCDA), and silicon killing and aluminum treated (SA). Results of microstructural examinations and mechanical tests show that the advanced steel making practice of silicon killing and aluminum treated steels (SA) revealed better carbide and bainite lath microstructures. In the case of steels manufactured by VCD, thick interlath carbide layers and incomplete, unclear bainite lath boundaries (BLB) were apparent compared to SA and VCDA steels, suggesting that the material may have experienced nucontrolled heat treatment during the manufacturing process of the thick shell forging material. Despite the microstructural differences the mechanical proerties were only slightly different.