Effects of Centerline Segregation of Cr Carbides and Non-Metallic Inclusions on the Pitting Corrosion of Fe-13Cr-0.3C Stainless Steel Produced by Continuous Casting and Strip Casting

The effects of the centerline segregation of Cr carbides and nonmetallic inclusions (NMIs) on the pitting corrosion of an Fe-13Cr-0.3C stainless steel (SS) plate produced by a continuous casting (CC) process were examined and compared with the effects on a plate produced by a strip casting (SC) process. For the CC plate annealed at 820°C, Cr carbides and NMIs were segregated in the centerline region, whereas they were uniformly and finely distributed throughout the SC plate. The resistance to pitting corrosion of the CC plate was much lower than that of the SC plate due primarily to the centerline segregation of Cr carbides and/or NMIs irrespective of whether annealing took place at 820°C or 1050°C. A micro-droplet cell test on CC samples revealed that the most dangerous site for pitting corrosion is the manganese sulfide (MnS) inclusion, followed by the centerline segregation of the Cr carbide. The oxide-type NMIs were not significant as sites at which pitting corrosion was initiated.