Abstract: In an electric induction furnace for heating a bar-shaped workpiece, wherein the workpiece has a longitudinal axis and is conveyed through the furnace in a conveying direction orthogonal to the longitudinal axis, an induction coil comprises a continuous conductor including a plurality of substantially horizontal primary conductor members and a plurality of substantially vertical return bends. The primary conductor members and return bends are serially connected and wound about a coil axis into a spiral having a substantially rectangular shape when viewed along the coil axis, which is substantially parallel to the conveying direction. The coil encloses a heating zone and generates a varying magnetic field in the heating zone when a varying electric current is conducted in the conductor. The coil includes first and second ends and has at the second end a workpiece exit portion, which encloses an exit section of the heating zone.

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: A method and apparatus particularly adapted for alloying a coating on a steel strip. The invention uses an induction heating furnace to produce a galvannealed product. In particular, the operating frequency to the heating coils of the furnace is modulated to avoid a resonant vibration in the steel strip through the heating zone of the furnace. Preferably the invention comprises imposing a frequency modulation on the operating frequency of the power signal to the heating coils.

Abstract: An improved electric induction furnace for use in the continuous heat treatment of a running length of coated metal strip moving in a substantially straight path through the furnace includes at least one heating coil extending completely around the path of the strip and extending in closely spaced relation to the opposed surfaces of the strip. The furnace is mounted on a track for movement transversely of the strip path, and each coil is provided with movable connector doors for opening and closing the continuous loops whereby when the coil is not energized, the connector doors may be disengaged to open the coil and permit the furnace to be moved along its track between a retracted non-use position and an online heat treating position. The coils are supported for transverse and angular adjustment to accurately align the coils with the strip whereby the opposed surfaces of the strip are substantially equal distant from the heating coils throughout the path through the furnace.

Abstract: An induction heater is provided for heating electrically conducting workpieces. The heater comprises an induction coil having a number of turns including long straight conductors wherein a major portion of the long straight conductors are secured to a concrete support beam. The conductors and the support beam vibrate together in response to electromagnetic field forces generated during operation of the heater. The coil is caused to vibrate with the coil support beam by a hard adhesive which bonds the support beam and the coil or by tension members which hold the coil tightly to the support beam.

Abstract: Apparatus for overheating the edges of a preheated formed skelp for the purpose of butt welding the skelp into pipe or tube. Induction coil assembly consisting of two (2) series connected loops, with a main conductor of each loop positioned within a magnetic flux guide and positioned adjacent to the open edges of the C-shaped skelp and the return conductors of each loop arranged externally on opposite side of the flux guide, providing localized overheating of the edges of the skelp prior to welding.

Abstract: An improved spray quenching device for quenching a relatively moving elongated workpiece such as steel pipe consisting of an improved quench means for directing a stream of quenchant at an acute angle to an elongated heated workpiece or pipe moving therethrough, means whereby the quenchant contacts the same in a relatively short time after heating and the quenchant is distributed thereby over a greater extent of the workpiece or pipe between the supports thereof.

Abstract: A method and apparatus for induction heating or melting furnaces of varying conductance, comprising controlled adjustment of the power factor angle in response to variations in load conductance to maintain constant power.

Abstract: There is disclosed herein a power control unti for controlling the voltage and power delivered to a single phase load, said control unit being preferably employed with loads whose impedance changes but slightly over the work cycle. The circuit utilizes a diode rectifier and a controlled rectifier connected in parallel therewith connected in series with capacitance and achieves transient-free and harmonic-free power control.

Abstract: There is disclosed herein apparatus and method for heating metallic tubing having a thickened portion, by passing the same through an induction heater energized with power at a relatively high frequency whereby the temperature of the body of the tubing rises at a faster rate than the temperature of the said thickened portion and passing the said tubing through an induction heater energized with power at a relatively low frequency to cause the temperature of said thickened portion of the tubing to rise at a faster rate than the temperature of the body of the tubing, the ratio of the power applied at said low frequency relative to the power applied at said high frequency being such that said body and said thickened portion attain substantially the same predetermined final temperature upon exiting from said apparatus.

Abstract: A static inverter is provided suitable for use as a high frequency power supply utilizing sets of switching thyristors which are switched in pairs in a predetermined sequence, with series-related capacitors, and which includes diodes connected to insure turn-off of the thyristors and to limit the maximum voltage that can occur across the sets of thyristors.

Abstract: There is disclosed herein a circuit for controlling the voltage and power delivered to a single phase induction melting or heating furnace wherein the impedance of the furnace varies. The circuit utilizes diode rectifier means and controlled rectifier means connected in series with capacitance and achieves transient-free and harmonic-free power control.