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In order to investigate the effect of Rare Earth La-Ce on the modification of inclusions in GCr15 bearing steel， a high-temperature tube furnace with a nominal capacity of 1 kg was used to smelt 6 heats of GCr15 bearing steel ingots with different La-Ce contents. Characterization methods such as optical microscopy and scanning electron microscopy were used， and the transformation law of inclusions in GCr15 steel at different La-Ce contents was studied using FactSage thermodynamic software. The results show that the typical inclusions in GCr15 bearing steel without adding La-Ce are Al2O3 and MnS， and the addition of La-Ce will modify it to more complex Rare Earth inclusions. With the increase of La-Ce content， the transformation law of inclusions in steel at 1 600 ℃ is Al2O3→REAlO3→ RE2O3→ RE2O2S → RE2O2S + RExSy（RE is La、Ce）. With the increase of La-Ce content， the density of inclusions and the average aspect ratio in the steel both decrease first and then increase. When the La-Ce content is 96 ×10-6， Al2O3 and MnS were both transformed into spherical RE2O2S·RExSycomposite rare earth inclusions. The number of inclusions in the steel was at a low level and the overall morphology of the inclusions was well controlled.

Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) results for cementite in carbon steel suggest that the alloying elements containing Cr and Mn. In order to explore the influence of Cr and Mn on Fe3C (FC), FC and Fe6Cr4Mn2C4 (FCMC) atomic structures and their energies and properties were calculated and compared by first-principles method. The results show that Cr and Mn can easily dissolve in FC and form stable FCMC. The structures of FC and FCMC are electrically neutral, the C atoms in them can get electrons, while the metal atoms (Mn, Fe, Cr) lose electrons, it is worth noting that Cr atoms close to Mn will get a small number of electrons due to Mn atoms have the strongest ability to lose electrons. The magnetic moment results suggest that FC is ferromagnetic and FCMC is sub-ferromagnetic, their magnetic moments of them are 22.18 and 5.09 μB/cell, respectively. The C−M (M = Fe, Cr, and Mn) bonds in FC and FCMC are covalent, the covalent electrons mainly provide by metal atoms, with the increase of C-M bond length, the covalence of bonds decrease gradually. The metal bonds of Fe−Fe, Fe−Cr, Fe−Mn, and Cr−Mn have both ionic and covalent character, while Cr−Cr and Mn−Mn bonds are ionic, and bond spin of Mn−Mn is zero, indicating that the bond is paramagnetic. Compared with FC, the Poisson's ratio and bulk modulus of FCMC structure are significantly reduced, while the Young's modulus and shear modulus are increased, this means that FCMC has lower compressive deformation resistance and higher y-axis shear resistance capacity than FC, i.e., FCMC has a higher brittleness than FC. [ABSTRACT FROM AUTHOR]

Tellurium treatment is used to control the morphology of manganese sulfide (MnS) inclusions, reduce the mechanical anisotropy, and improve the machinability of sulfur‐bearing steels, such as free‐cutting steels, super free‐cutting steels, medium‐carbon microalloyed steels, and die steels. The boiling point of tellurium is low, and it is mainly added to steel in the form of fine particles wrapped in a cored wire. In steels, tellurium mainly exists in the form of Mn(S, Te) inclusions or MnTe–MnS composite inclusions. The strength of MnS inclusions is increased through tellurium doping; thus, the aspect ratio of sulfide after hot working is significantly decreased through tellurium treatment. However, the tellurium content in steel should not be too high; otherwise, brittle compounds will form and cause embrittlement, particularly in high‐alloyed steels. The Te/S mass ratio is considered an important factor in tellurium treatment. When the Te/S mass ratio in steel is 0.2, the aspect ratio of the as‐cast sulfide could be controlled within the optimal range. During steelmaking, the yield of Te can be improved by reducing the basicity of the slag and decreasing the time of Te evaporation. Through data‐driven material design, Te treatment technology undergoes broader development. [ABSTRACT FROM AUTHOR]