A number of researchers have reported that a static magnetic field (SMF) will affect the process of selective laser melting (SLM), which is achieved mainly through affecting molten pool evolution and microstructure growth. However, its underlying mechanism has not been fully understood. In this work, we conducted a comprehensive investigation of the influence of SMF on the SLM Inconel 625 superalloy through experiments and multi-scale numerical simulation. The multi-scale numerical models of the SLM process include the molten pool and the dendrite in the mushy zone. For the molten pool simulation, the simulation results are in good agreement with the experimental results regarding the pool size. Under the influence of the Lorentz force, the dimension of the molten pool, the flow field, and the temperature field do not have an obvious change. For the dendrite simulation, the dendrite size obtained in the experiment is employed for setting up the dendrite geometry in the dendrite numerical simulation, and our findings show that the applied magnetic field mainly influences the dendrite growth owing to thermoelectric magnetic force (TEMF) on the solid–liquid interface rather than the Lorentz force inside the molten pool. Since the TEMF on the solid–liquid interface is affected by the interaction between the SMF and thermal gradient at different locations, we changed the SLM parameters and SMF to investigate the effect on the TEMF. The simulation shows that the thermoelectric current is highest at the solid–liquid interface, resulting in a maximum TEMF at the solid–liquid interface and, as a result, affecting the dendrite morphology and promoting the columnar to equiaxed transition (CET), which is also shown in the experiment results under 0.1 T. Furthermore, it is known that the thermoelectric magnetic convection (TEMC) around the dendrite can homogenize the laves phase distribution. This agrees well with the experimental results, which show reduced Nb precipitation from 8.65% to 4.34% under the SMF of 0.1 T. The present work can provide potential guidance for microstructure control in the SLM process using an external SMF.

Submerged entry nozzle (SEN) clogging is a troublesome phenomenon in the continuous casting process that can induce the asymmetric mold flow, and thus, lowering the steel product quality. In this paper, a mathematical model coupling the electromagnetic and flow fields, was developed to investigate the influence of the SEN clogging rate on the flow field and the influence of electromagnetic stirring (EMS) on the asymmetric mold flow. Slag entrapment index R_c was introduced to quantify the possibility of slag entrapment, and symmetric index S was introduced to quantify the symmetry of the flow field. The results show that as the SEN clogging rate increased, the slag entrapment index R_c increased, while the symmetric index S decreased. EMS can greatly improve the symmetry of the flow field with SEN clogging, but it cannot remove the asymmetric phenomenon completely because the stirring intensity should be controlled below the safe level to avoid slag entrapment.

Silica ceramic cores prepared by heat-press molding were strengthened by impregnating silicone resin. The effect of heating treatment conditions on the properties of silica ceramic cores was analyzed. Results showed that the ambient bending strength increased from 9.3 ± 2.0 MPa to 24.8 ± 1.5 MPa by curing process at low temperature of 250 °C. However, further heating treatment at high temperature ranging from 1150 to 1300 °C made the strength of the samples lower than that of the cured samples owing to the decomposition of silicone resin. But the strength of the samples was still higher than that of raw samples. The increasing heating treatment temperature promoted an increase in the strength by a densification process.