To investigate the influence of heavy rare earth element yttrium on the type, morphology, and quantity distribution of inclusions in grain-oriented silicon steel, thermodynamic calculation was carried out on the typical rare earth inclusions in grain-oriented silicon steel containing yttrium. The main inclusions in the experimental steels with and without yttrium were observed and analyzed using field emission scanning electron microscope (FESEM, Zeiss Gemini SEM 300) and energy dispersive spectrometer (EDS, OXFORD Ultim Extreme). The electron backscatter diffraction (EBSD, OXFORD Symmetry) was used to analyze the local average misorientation of the hot-rolled plate. The results show that the inclusions in the Y-free steel are mainly long MnS, irregular Al₂O₃ and MnS-Al₂O₃. The inclusions in the Y-bearing steel are spherical rare earth compounds. The number of inclusions in Y-bearing steel decreases and the size increases compared with Y-free steel. The mean value of local average misorientation and the dislocation density of Y-bearing steel are smaller compared with Y-free steel, which could avoid the cracking problem caused by dislocation accumulation during hot rolling. After heating the rough-rolling sample to 1350 °C, there is no obvious difference in the inclusions type between the Y-free steel and Y-bearing steel. However, the area fraction of inclusions in Y bearing steel increases slightly. According to the thermodynamic calculation results, there are mainly three kinds of rare earth inclusions, YS, Y₂S₃ and Y₂O₂S, in Y-bearing steel, among which YS has the strongest stability and the stability of Y₂O₂S is the weakest. The rare earth element yttrium can effectively modify the inclusions, transforming the irregular Al₂O₃ inclusions, formed during the deoxidation of silicon steel into spherical rare earth inclusions, which suppress the precipitation of long MnS inclusions. Thus, the formability of the steel could be improved.

Reasonable regulation of nonmetallic inclusions in steel can significantly improve its strength, toughness, and corrosion resistance. In this paper, EH420 marine steel was treated with Mg, Ce, and Mg-Ce to modify the inclusions. The effects of different treatments on the morphology, composition, size distribution, induced intragranular ferrite (IGF) nucleation, and pitting resistance of inclusions were systematically analyzed using various methods. The results show that the Mg-Ce composite treatment can modify irregular MgAl₂O₄ inclusions into spherical Mg-Ce-O composite inclusions and MgO-dominated inclusions. The density of inclusions is increased from 74.8/mm² to 186.0/mm², and the average size of inclusions is decreased from 2.60 μm to 1.07 μm. The Mg-Ce-O composite inclusions are effective inclusions for inducing IGF. Furthermore, the pitting potential is increased from −503 mV to −487 mV, and the corrosion rate is decreased. The order of average electronic work function is ΦMgO < ΦCe₂O₃ < Φα-Fe < ΦAl₂O₃. Ce₂O₃ is hard to induce pitting corrosion due to its similar electronic work function to the steel matrix. Thus, the Mg-Ce composite treatment is better than that for Mg and Ce treatment alone, and has better application prospects.

The effect of rare earth Y on precipitates and textures of the grain-oriented silicon steels, the composition, morphology, size, quantity of inclusions and texture evolution of hot-rolled and cold-rolled oriented silicon steel containing rare earth Y were studied using transmission electron microscopy, field emission scanning electron microscope, and electron backscatter diffraction. The results show that there are mainly spherical or ellipsoidal Y ₂ O ₂ S precipitates in the Y bearing silicon steel. Rare earth treatment effectively improves the precipitates’ morphology and restrains the precipitation of the long-strip MnS in the hot-rolled plate. Meanwhile, the microstructure is more uniform, and the recrystallized grains on the surface and the fiber structure in the central layer are larger after hot rolling compared with Y-free steel. Furthermore, with the addition of rare earth Y, the unfavorable brass texture and rotational cube texture in the hot-rolled plate are reduced. Meanwhile, the number of shear bands is increased and the strength of the favorable {111} 〈112〉 texture is improved in the cold-rolled plate, which helps develop the Goss texture during the annealing process.

The unlubricated sliding wear test of high chromium white cast irons (HCCIs) was conducted using a pin-on-disc configuration under different heat treatments and different hardnesses of the counterface. With the increase of counterface hardness (20 HRC–47 HRC–54 HRC), the mass loss of the sample first increases then decreases. When the counterface hardness is 20 HRC, adhesion wear mainly takes place between the high chromium cast iron and the surface of 1045 steel. When the hardness is 47 or 54 HRC, first HCCI’ matrix wear takes place, then carbide bump flakes under alternating stress. The mass loss of the counterface decreases with the increase of hardness for the same sample. The mass loss of quenching, once tempering and twice tempering sample decreases gradually for the same counterface hardness, but fluctuation of the samples’ surface increased. The disc material is always softer than the pin material and results in a severe wear regime operation.