Abstract: A process for directional solidification of a cast part comprises energizing a primary inductive coil coupled to a chamber having a mold containing a material; generating an electromagnetic field with the primary inductive coil within the chamber, wherein said electromagnetic field is partially attenuated by a susceptor coupled to said chamber between said primary inductive coil and said mold; determining a magnetic flux profile of the electromagnetic field after it passes through the susceptor; sensing a component of the magnetic flux in the interior of the susceptor proximate the mold; positioning a mobile secondary compensation coil within the chamber; generating a control field from a secondary compensation coil, wherein said control field controls said magnetic flux; and casting the material within the mold.

Abstract: An electromagnetic induction melting furnace to control an average nominal diameter of the TiB2 cluster of the Al—Ti—B alloy includes a main body containing the melted alloy; and a multi-layer coil disposed on the main body, wherein a frequency of the alternative current of each coil of the multi-layer coil is different, and the alloy is heated by inducing a magnetic field generated by the alternative currents. The selection of the frequency and the changeable magnetic field may reduce the cohesion force between the TiB2 grains of the Al—Ti—B alloy to control the average nominal diameter of the TiB2 cluster.

Abstract: An electromagnetic induction melting furnace to control an average nominal diameter of the TiC cluster of the Al—Ti—C alloy includes a main body containing the melted alloy; and a multi-layer coil disposed on the main body, wherein a frequency of the alternative current of each coil of the multi-layer coil is different, and the alloy is heated by inducing a magnetic field generated by the alternative currents. The selection of the frequency and the changeable magnetic field may reduce the cohesion force between the TiC grains of the Al—Ti—C alloy to control the average nominal diameter of the TiC cluster.

Abstract: A power supply (300) includes a rectification means (303) for providing a voltage from an AC mains input (301). An inverter (307) is used for supplying a switched AC voltage at high frequency from the rectified voltage to a transformer (311) for modifying the amplitude and/or providing galvanic isolation of the switched AC voltage. Output rectification (313) is used to convert the switched AC voltage at the secondary of the transformer back to a rectified voltage. An inductor (309) is used in series with the primary of the transformer (311) for reducing the peak and ripple current in both the primary and secondary of the transformer while minimizing or eliminating the need for an inductive component in the output filter of the supply.

Abstract: An electromagnetic induction melting furnace to control an average nominal diameter of the TiC cluster of the Al—Ti—C alloy includes a main body containing the melted alloy; and a multi-layer coil disposed on the main body, wherein a frequency of the alternative current of each coil of the multi-layer coil is different, and the alloy is heated by inducing a magnetic field generated by the alternative currents. The selection of the frequency and the changeable magnetic field may reduce the cohesion force between the TiC grains of the Al—Ti—C alloy to control the average nominal diameter of the TiC cluster.

Abstract: An electromagnetic induction melting furnace to control an average nominal diameter of the TiB2 cluster of the Al—Ti—B alloy includes a main body containing the melted alloy; and a multi-layer coil disposed on the main body, wherein a frequency of the alternative current of each coil of the multi-layer coil is different, and the alloy is heated by inducing a magnetic field generated by the alternative currents. The selection of the frequency and the changeable magnetic field may reduce the cohesion force between the TiB2 grains of the Al—Ti—B alloy to control the average nominal diameter of the TiB2 cluster.

Abstract: The present invention is apparatus for, and method of, heating, melting and purifying a material by electric induction heating in a susceptor furnace. Non-electrically conductive solid charge may initially be placed in the furnace. Output frequency from a power source supplying current to one or more induction coils surrounding the furnace is selected to maximize magnetic coupling with the susceptor material in the susceptor furnace to induce eddy current heating in the material. Heat transfers by conduction from the susceptor material to the non-electrically conductive charge placed in the susceptor furnace to melt the charge. Output frequency is reduced as the charge melts and becomes electrically conductive to enhance magnetic coupling with the melt in the furnace. Degassing of impurities from the melt can be achieved by bubbling a gas through the melt while the surface level of the melt is maintained at vacuum.

Abstract: An apparatus and process are provided for controlling the heating or melting of an electrically conductive material. Power is selectively directed between coil sections surrounding different zones of the material by changing the output frequency of the power supply to the coil sections. Coil sections include at least one active coil section, which is connected to the output of the power supply, and at least one passive coil section, which is not connected to the power supply, but is connected in parallel with a tuning capacitor so that the at least one passive coil section operates at a resonant frequency and the output frequency of the power supply is changed so that the induced power in the at least one passive coil section changes as the frequency is changed.

Abstract: An induction furnace includes a cylinder, a top and bottom cover that seal the top and bottom ends of the cylinder, and coolant passages within the cylinder and the covers. The induction furnace further includes a power supply and a coil. The coil surrounds the chamber and is hollow to allow flow of coolant therethrough. A susceptor susceptible to induction heating is located in the chamber and includes top and bottom pieces. A thermal insulator is disposed between the susceptor and the inner walls of the chamber and can be formed of a fused quartz cylinder within which the susceptor and the workpiece are contained. The thermal insulator can also include infrared reflectors and insulating members on the ends of the susceptor to reduce heat leakage to parts of the furnace outside of the susceptor.

Abstract: An induction furnace system has an active induction coil surrounding a crucible. A passive induction coil also surrounds the crucible. The passive induction coil is connected in parallel with a capacitor to form an L-C tank circuit. A source of ac current is provided to the active induction coil to produce a magnetic field that inductively heats and melts an electrically conductive material in the crucible. The magnetic field also magnetically couples with the passive induction coil to induce a current in the passive induction coil. This induced current generates a magnetic field that inductively heats and melts the material. The resistance of the L-C tank circuit is reflected back into the circuit of the active induction coil to improve the overall efficiency of the induction furnace system. The crucible may be open-ended to allow the passage of the electrically conductive material through the crucible during the heating process.

Abstract: An induction furnace system has an active induction coil surrounding a crucible. A passive induction coil also surrounds the crucible. The passive induction coil is connected in parallel with a capacitor to form an L-C tank circuit. A source of ac current is provided to the active induction coil to produce a magnetic field that inductively heats and melts an electrically conductive material in the crucible. The magnetic field also magnetically couples with the passive induction coil to induce a current in the passive induction coil. This induced current generates a magnetic field that inductively heats and melts the material. The resistance of the L-C tank circuit is reflected back into the circuit of the active induction coil to improve the overall efficiency of the induction furnace system. The crucible may be open-ended to allow the passage of the electrically conductive material through the crucible during the heating process.

Abstract: An induction furnace having a voltage source series inverter, a load circuit having a combination of an induction coil and a resonating capacitor bank, and control circuitry to phase lock the inverter frequency to the natural resonant frequency of the load. The capacitor bank can be divided into two groups, one across the output of the inverter and the other in series with the load. This arrangement allows for the division of the inverter voltage across the furnace coil according to the ratio of the two capacitances. The inverter uses pulse width modulation and is buffered from the load circuit by means of a small series connected inductor. Additionally, the system can have a common power supply system that supplies power in any desired proportion to a plurality of induction furnaces.

Abstract: The present invention relates to a melting method by which the melting raw materials having a variety of configurations are collectively melted to enable the composition to be adjusted in the melt, and a melting apparatus and tapping method by which tapping is readily controlled, wherein the raw materials are melted by flowing an electric current satisfying the frequency range defined by the equation below using a crucible with an inner diameter of 400 mm or more in melting using a cold crucible induction melting apparatus, the melt being tapped through a tapping nozzle provided at the bottom of the crucible and equipped with a tapping coil wound around the circumference of the nozzle:7.8.times.2.times.log(D).ltoreq.log(F).ltoreq.8.7-2.times.log(D)(wherein F denotes the frequency of a power supply and D denotes the inner diameter (mm) of the crucible).

Abstract: A coreless induction furnace includes a vertical melting crucible defining a melting chamber having upper and lower chamber portions and at least two coils. A first one of the coils is disposed so as to surround the upper chamber portion and a second one of said coils is disposed so as to surround the lower chamber portion. The furnace also includes a single-phase load-commutated oscillation circuit converter, a plurality of capacitors and an electrical circuit system electrically connecting the coils, the capacitors and the converter. The electrical interconnection is such that the first one of the coils is electrically connected in series with a first one of the capacitors having a first capacitvie impedance to thereby present a first oscillation circuit, and the second one of the coils is electrically connected in series with a second one of the capacitors having a second capacitive impedance to thereby present a second oscillation circuit.

Abstract: Temperature sensors are embedded in a refractory material that make up the walls of a body of an induction furnace and detect an increase in the temperature of a molten metal in the body of the furnace due to the bridging of a metal material that is to be melted in the furnace body. The temperature sensors are connected to an antenna for detecting runout. Since various electrical data (voltage, current, power, frequency, etc.) that affect an alternating current to be supplied to a coil of the induction furnace change depending on the temperature of the molten metal, bridging of the metal material is detected by determining the rates of temporal change in these electrical data. Furthermore, the changes in the electrical data with respect to the progress of the operation of the induction furnace are previously stored in data storage, and the electrical data stored are compared with electrical data detected in the induction furnace in operation.

Abstract: Temperature sensors are embedded in a refractory material that make up the walls of a body of an induction furnace and detect an increase in the temperature of a molten metal in the body of the furnace due to the bridging of a metal material that is to be melted in the furnace body. The temperature sensors are connected to an antenna for detecting runout. Since various electrical data ( voltage, current, power, frequency, etc.) that affect an alternating current to be supplied to a coil of the induction furnace change depending on the temperature of the molten metal, bridging of the metal material is detected by determining the rates of temporal change in these electrical data. Furthermore, the changes in the electrical data with respect to the progress of the operation of the induction furnace are previously stored in data storage, and the electrical data stored are compared with electrical data detected in the induction furnace in operation.

Abstract: A system for simultaneously melting metal and holding molten metal for treatment and the like comprises a plurality of separate induction furnaces, each having an induction coil. The induction coil of each furnace is arranged to inductively heat metal in its associated furnace. A plural-output power supply is operatively connected to the induction coils for supplying ac power to the coils. The power supply comprises at least one rectifier section having an output and a plurality of high-frequency inverter sections equal to the number of separate induction furnaces Each inverter section has an input operatively associated with the rectifier section output for receiving power from said at least one rectifier section and an output operatively connected to a respective one of the induction coils for supplying ac power to the induction coil. Switches are provided for selectably interrupting power from selected ones of said plurality of inverter sections to their associated induction coils.

Abstract: In one embodiment, an induction furnace is disclosed having a crucible, first and second set of induction coils surrounding the crucible and master and slave inverters, whereas in another embodiment, related to a channel-type induction furnace, the lower portion of the crucible houses at least first and second induction coils. The master and slave inverters each have a switching device with known turn-off-time characteristics for generating an alternating polarity output voltage across a load. The master inverter monitors the current, detects the zero-crossing of the current in the first induction coils, and generates a control signal in response to such detection of zero-crossing. The control signal is generated at an interval following the detection of the zero-crossing which is greater than the turn-off-time characteristic of the switching device.

Abstract: An apparatus for directing electromagnetic flux near an induction coil comprises a loop-shaped member adapted to conduct electromagnetic flux, defining an axis parallel to the central axis of the induction coil and extending substantially the length of the coil. The loop-shaped member acts as a return circuit for minimizing a stray magnetic field external to the coil.

Abstract: A control circuit particularly useful for controlling the application of power to a single phase induction furnace from a normal line frequency power supply is provided. The load has a large inductance and a resistance. A switch, preferably formed from thyristors, is provided in series connection with the furnace load. A first capacitor is provided in parallel connection with the series connected switch and load. A second capacitor is provided in series connection with the series connected switch and load and the first capacitor whereby selective operation of conduction of the switch results in the smooth and continuous control of furnace power. In an alternative embodiment small inductors are placed in series with the capacitors to provide a filter preferably tuned to the fourth harmonic of the power supply.

Abstract: The invention relates to a method for temperature control in a channel of an inductor unit of a channel-type induction furnace for iron or steel. The method is characterized in that the current intensity or the power is measured, and the measuring signal (I, P) is compared with a desired value (I.sub.b, P.sub.b) in a control means for controlling the power of the inductor, the power to the inductor being switched off or reduced at a value I>I.sub.b or P>P.sub.b, where I.sub.b or P.sub.b corresponds to a temperature at or near the Curie point of the iron/steel.In those cases where the inductor is supplied from a thyristor unit, the control can also be carried out so that a constant impedance, corresponding to the conditions at the Curie point, is maintained in the inductor circuit.