Effect of RE Content on TiN Inclusions Formation in P110-Grade Casing Steel

Hydrogen resistance and sulfide stress corrosionCorrosion resistance of casing steelsCasing steel are severely impaired by large TiNTiN inclusionsInclusions. Rare earth elementsRare earth elements have the potential to modify the properties of non-metallic inclusionsInclusions in steelsSteel. The effect of RE content on the formation of TiNTiN inclusionsInclusions in P110-grade casing steelCasing steel has been investigated based on industrial trial. The results show that the main types of inclusionsInclusions formed in the casing steelCasing steel without RE addition are pure TiNTiN and compositeComposites Ca(-S)-AlAl(-Mg)-O + TiNTiN, while pure TiNTiN and compositeComposites RE-P(-As) + TiNTiN or compositeComposites RE-O(-S-Ca) + TiNTiN after RE addition. The number density of TiNTiN inclusionsInclusions in the rolled products decreases with increasing RE content (0, 0.0160%, 0.0197%), but the average size of TiNTiN inclusionsInclusions becomes smaller and then larger. Thermodynamic calculations show that increasing the RE content in casing steelCasing steel reduces the precipitationPrecipitation temperatureTemperature of TiNTiN inclusionsInclusions, which inhibits the precipitationPrecipitation of TiNTiN inclusionsInclusions.