Effect of Cerium on Inclusion Modification in a Secondary-Hardening Steel

Abstract

Owing to the continuous increasing of steel strength, mechanical properties including toughness and fatigue performance are becoming increasingly sensitive to inclusions in ultra-high strength steel. Rare-earth treatment is considered as an effective method to reduce the harmful effects of inclusions, but is rarely applied in secondary-hardening steel. In the present study, different amounts of cerium were added in a secondary-hardening steel to investigate the modification effect of Ce on non-metallic inclusions in steel. The characteristics of inclusions were observed experimentally using SEM-EDS and the modification mechanism was analyzed based on thermodynamic calculations. The results indicated that the main inclusions in Ce-free steel are Mg-Al-O + MgS. Thermodynamic calculation indicated that MgAl2O4 is firstly formed in liquid steel and then successively transformed into MgO and MgS during cooling process. When the Ce content is 0.0030%, the typical inclusions in steel were individual Ce2O2S and MgO + Ce2O2S complex inclusions. When the Ce content was increased to 0.0071%, the typical inclusions in steel were individual Ce2O2S- and Mg-containing inclusions. Ce treatment modifies the angular magnesium aluminum spinel inclusions into spherical and ellipsoidal Ce-containing inclusions, thus reducing the harmful effect of inclusion on steel properties.

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel

“…Because of its unique electron layer structure, rare earth Ce is widely used for modifying inclusions in steel, improving solidification structure, microalloying and so on [13][14][15][16][17][18][19]. Rare earth elements have a strong affinity with harmful elements such as O and S in steel [20,21].…”

Experiments on Oxidation and Combustion Behaviors of Cerium Metal Slice with Slow Heating under O2/Ar Atmospheric Conditions

“…Cerium has been extensively deployed in many fields, such as catalysts [1,2], energy [3,4], putty fabricated accession [5], metal alloys additives [6][7][8], and anti-corrosion [9]. Regarded as one of the outstanding additions that can improve alloys' anti-oxidation and ignition resistance [10], comprehensive performance assessments of Ce require the evaluation of a wide range of common accident conditions and adverse impacts due to the activated chemical properties [11][12][13], particularly toxic suspended nanoparticles (diameter ≤ 100 nm) released in Ce-related activities.…”