Abstract: An induction furnace includes a pair of induction coils with a pair of faraday rings disposed between the induction coils to substantially prevent mutual inductance between the first and second induction coils. The induction coils preferably have a different size circumference and may be coplanar. The prevention of mutual inductance provided by the faraday rings is particularly useful for a pusher furnace in which adjacent furnace sections are heated to different and rather specific temperatures.

Abstract: A pusher furnace includes furnace sections having respective susceptors, a slide rail extending through the furnace sections for sliding pusher plates thereon and an alignment assembly for aligning the susceptors and slide rails of adjacent furnace sections. A support structure spaces the susceptors from insulation therebelow to protect the insulation from degradation from contact with the susceptors. The susceptors are slidably mounted on the support structure to accommodate thermal expansion and shrinkage of the susceptor. The upstream end of the slide rails have beveled upper edges to help prevent the pusher plates from catching thereon. The upstream ends are also laterally tapered to reduce the degree of force encountered should a pusher plate catch thereon. Adjacent insulation members have expansion joints filled with a refractory felt. The susceptors slidably and sealingly engage exhaust ports to allow for thermal expansion and shrinkage of the susceptor without damaging the exhaust port.

Abstract: A pusher plate for use in a pusher furnace includes a shaped guidance groove in its lower surface which preferably has a bow-tie shape with a narrower central section and wider ends proximate the leading and trailing faces of the plate. The groove receives therein a guide rail which is disposed intermediate a pair of slide rails upon which the plate slides. The shape of the groove allows the plate a small amount of lateral rotation to minimize jamming during travel. Adjacent plates pivot upon contact with each other to automatically adjust their orientation during travel through the furnace. The leading and trailing faces of the plates thus contact one another over a larger surface area to reduce damage to the plates by reducing the pressure therebetween.

Abstract: A compression system for an inductively heated pusher furnace controls movement of susceptors during thermal contraction thereof. The system includes a plurality of furnace sections each having a susceptor wherein each susceptor abuts an adjacent susceptor and wherein the susceptors include first and last susceptors. A compression plate abuts the first susceptor to apply force thereon toward the last susceptor to keep the susceptors in abutment with each other during contraction of the susceptors during cooling thereof. An actuator for moving the compression plate is preferably automatically controlled by a computerized control system. The susceptors together form a tunnel through which pusher plates travel and have overlapping joints which seal against the escape of gasses and allow for a degree of susceptor contraction without forming a gap therebetween even in the absence of compression of the susceptors.

Abstract: An induction furnace includes an induction coil, an electrically non-conductive crucible having an inner diameter disposed within the induction coil, and an electrically conductive member disposed below the crucible and having an outer diameter which is further from the induction coil than is the inner diameter of the crucible. Due to the non-conductive nature of material disposed within the crucible at lower temperatures, the induction coil initially inductively heats the conductive member, which transfers heat to the material to melt a portion of the material. Once the material is susceptible to inductive heating (usually upon melting) the susceptible material is inductively heated by the induction coil. During the process, inductive heating of the material greatly increases as inductive heating of the conductive member greatly decreases due to low resistivity of the molten material and due to the molten material being closer to the coil than is the conductive member.

Abstract: A method and apparatus for optimizing melting of titanium for processing into ingots or end products. The apparatus provides a main hearth, a plurality of optional refining hearths, and a plurality of casting molds or direct molds whereby direct arc electrodes melt the titanium in the main hearth while plasma torches melt the titanium in the refining chambers and/or adjacent the molds. Each of the direct arc electrodes and plasma torches is extendable and retractable into the melting environment and moveable in a circular pivoting or side to side linear motion.

Abstract: A continuous- or intermittent-melt induction furnace useful for heating and/or melting semi-conductor or other materials includes an induction coil, a susceptor switchable between open and closed electric circuit modes, and a crucible. The susceptor is inductively or resistively heated in the closed circuit mode and transfers heat to material in the melting cavity to make it susceptible to inductive heating. The susceptor is then switched to the open circuit mode and the susceptible material is directly inductively heated to melt remaining solid material. A cone-shaped flow guide in the melting cavity improves molten material flow to improve the ability to draw small-particle material into the melt and increase crucible life due to improved heat uniformity. A trap passage communicating with the melting cavity and an exit opening in the crucible allows the flow of material through the exit opening to be controlled by pressure differentials on either side of the trap passage.

Abstract: A method and apparatus for optimizing melting of titanium for processing into ingots or end products. The apparatus provides a main hearth, a plurality of optional refining hearths, and a plurality of casting molds or direct molds whereby direct arc electrodes melt the titanium in the main hearth while plasma torches melt the titanium in the refining chambers and/or adjacent the molds. Each of the direct arc electrodes and plasma torches is extendable and retractable into the melting environment and moveable in a circular pivoting or side to side linear motion.

Abstract: A continuous- or intermittent-melt induction furnace useful for heating and/or melting semi-conductor or other materials includes an induction coil, a susceptor switchable between open and closed electric circuit modes, and a crucible. The susceptor is inductively or resistively heated in the closed circuit mode and transfers heat to material in the melting cavity to make it susceptible to inductive heating. The susceptor is then switched to the open circuit mode and the susceptible material is directly inductively heated to melt remaining solid material. A cone-shaped flow guide in the melting cavity improves molten material flow to improve the ability to draw small-particle material into the melt and increase crucible life due to improved heat uniformity. A trap passage communicating with the melting cavity and an exit opening in the crucible allows the flow of material through the exit opening to be controlled by pressure differentials on either side of the trap passage.

Abstract: An induction furnace includes an induction coil, an electrically non-conductive crucible having an inner diameter disposed within the induction coil, and an electrically conductive member disposed below the crucible and having an outer diameter which is further from the induction coil than is the inner diameter of the crucible. Due to the non-conductive nature of material disposed within the crucible at lower temperatures, the induction coil initially inductively heats the conductive member, which transfers heat to the material to melt a portion of the material. Once the material is susceptible to inductive heating (usually upon melting) the susceptible material is inductively heated by the induction coil. During the process, inductive heating of the material greatly increases as inductive heating of the conductive member greatly decreases due to low resistivity of the molten material and due to the molten material being closer to the coil than is the conductive member.