The thermal and numerical simulation of the mould electromagnetic stirring (M-EMS) during continuous casting (CC) of the GCr15 bearing steel was performed. The thermal simulation apparatus with the M-EMS was used to examine the effect of stirring parameters on solidification structures. It was found that M-EMS enlarged the equiaxed grain regions, refined the grain size and resulted in more homogeneous distribution of the solute elements. The flow field in the mould was simulated to show the M-EMS intensity, which is in accordance with experimental observations. The mechanical properties of the blooms obtained at the current of 300A and frequency of 5 Hz are optimal.

No abstract

This work focus on the effect of different contents of Cu on microstructure and properties of Al-Zn composite coatings. The SEM and EDS were used to analyse the microstructure and composition of the coatings, and the deposition efficiency and porosity of the coating were calculated. The results show that the coatings have low porosity and uniform structure. The hardness, electrical conductivity and corrosion resistance of the coating were measured, and the results showed that the addition of Cu can improve the hardness, electrical conductivity and corrosion resistance of the coating but reduce the deposition efficiency of the powder.

This work focus on the influence of Ni-Coated Graphite contents on microstructure and properties of Al-Zn composite coatings. The morphology and composition of the coatings were analysed by SEM and EDS. The result showed that the coating is dense, the composition is uniform, and there is no phase change. The bonding mechanism between coating particles and between coating and substrate was also analysed. The hardness and wear resistance of the four coatings were tested. It was found that the addition of Ni-Coated Graphite improves the hardness and wear resistance of the coating. In general, the addition of 20% Ni-Coated Graphite powder is the best for Al-Zn composite coatings with low porosity.

The heat absorption method (HAM) was proposed to improve the quality of a large steel ingot. The CaO-CaF 2 inorganic material rods was used to reduce 5 K superheat of the 6-ton GCr15 molten steel. The quality of the steel ingots with and without the HAM was compared. In comparison with conventional casting, the HAM not only significantly alleviated the A-and V-segregation and the segregation levels of carbon and sulfur, but also reduced the number of inclusions and the shrinkage porosity zone in the 6-ton steel ingot. The simulation results demonstrated that the molten steel could quickly be cooled from within by the inorganic material rods, which is the main reason for the reduction of macrosegregation. Additionally, the majority of inclusions could be absorbed and removed when the liquid inorganic material floated up in the molten steel.