The theoretical and numerical calculation and experimental study on soft contact electromagnetic casting forming
Based on classical electromagnetic theory, the electromagnetic pressure calculation model and the formula of electromagnetic casting forming have been established. Theoretical and numerical results indicated that the frequency, current density, relative permeability of alloy melt and resistivity can also influence the effect of electromagnetic pressure. Meanwhile, the effect of metal physics properties parameters on the value of electromagnetic pressure is more complicated. The needed magnetic field for casting Al-Si alloys liquid column with length of 0.05m in experiment was very close to the theoretical value. This result indicated that the formula of electromagnetic casting forming can be used to guide experiments and the actual industrial production.
Initial Solidification Control of Continuous Casting Using Electromagnetic Oscillation Method
An initial solidification control technology, called the Electromagnetic Oscillation Method, intermittently applying high frequency magnetic field was developed aiming to reduce the friction between mold and initial solidified shell and to perform high speed casting for producing cast having excellent surface properties. According to the method, a high frequency magnetic field is applied synchronizing with the mold oscillation, applying a horizontal and inward electromagnetic force from outside the mold during the positive strip period, while applying a downward electromagnetic force from above the mold during the negative strip period. The method was investigated in terms of influence on the surface properties of cast and other variables by applying the method to laboratory scale continuous steel casting. The experiment was given by casting round billets having 100 mm in diameter at casting speeds of 0.5 to 1.6mm/min, applying high frequency magnetic fields of 1 to 9.8 kHz. The flux film thickness in the mold increased by applying horizontal electromagnetic force during the positive strip period, and the surface properties of the cast improved. By applying downward electromagnetic force during the negative strip period, the strength of initial solidified shell increased to prevent the occurrence of breakout.
Continuous Casting of Steel Billet with High Frequency Electromagnetic Field
In order to develop the high frequency electromagnetic continuous casting technology for applying to steel, numerical analysis of the magnetic field and casting experiments using various parameters have been conducted. The method of using cold inserts was well established to lead to a reliable numerical model. According to this numerical model, it was predicted that while casting, the magnetic field would be concentrated on the common region occupied by the coil and the melt and further its maximum value would be seen just below the melt level. Casting experiments have been carried out using tin as a simulating material for steel. No oscillation mark was observed on the billets because the solidification started without hook. Under an optimum condition, billet surface roughness was improved to 1/10 of the conventionally cast billets. The surface quality of the billet was heavily dependent on the melt level, the casting speed, and the coil current. In case of the excessive coil current, wave marks other than the oscillation mark appeared on the billet surface. The billet with proper electromagnetic conditions showed a thinner solid shell at the early stage of the solidification and a thicker shell at the mold bottom in comparison with the conventional cast billet. It has been concluded that the Joule heat is a more dominant factor than the magnetic pressure in determining the surface quality of cast products in the high frequency electromagnetic continuous casting process.