Modification of titanium inclusions in 321 stainless steel by yttrium and cerium
The study investigated the thermodynamic characteristics of titanium inclusions in 321 stainless steel and the impact of rare earth elements,specifically Y and Ce,on the composition and morphology of these inclusions during the steel's melting process.The results showed that in the absence of rare earth elements,the inclusions commonly found in 321 steels were TiN and Al2O3-TiN composite inclusions,where Al2O3 served as the core.When adding rare earth elements to the steel,at a Y addition of 5.0×10-6(mass fraction),the steel contained typical inclusions of Al2O3-Y2O3 and some unmodified Al-O composite inclusions.As the Y element content increased,the Al2O3 inclusions were gradually modified to yttrium-containing oxides.When the Y addition was 4.7×10-5,the typical inclusions in the steel were Y2O3-TiN composite inclusion.With the addition of 5.0×10-6 Ce,the inclusions consisted mainly of Ce-O and Ce-Al-O,and Al2O3 inclusions no longer existed separately.The number and size of TiN inclusions in the liquid steel varied depending on the addition of rare earth elements.The addition of rare earth elements resulted in a decrease in the number and size of TiN.Specifically,when the amount of Ce added was 1.0×10-5,the number and size of TiN were similar to those when the amount of Y added was 4.7×10-5.Ce appears to have a more effective modification effect on inclusions compared to Y at similar addition amounts.
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