High efficiency induction heating and melting systems

An induction furnace for heating a workpiece, comprising:

• a substantially enclosed crucible having a selectably closeable opening whereby the workpiece can be inserted or removed from the crucible, the crucible formed substantially from the group of materials consisting of silicon carbides, high resistivity steels and high permeability steels;
• an at least one induction coil comprising a cable wound of a plurality of conductors isolated from each other, the at least one induction coil surrounding the crucible;
• and
• an electrically and thermally insulating isolation sleeve of low magnetic permeance separating the crucible from the at least one induction coil.

A process for heating a metal workpiece comprising the steps of:

• feeding the metal workpiece through a tunnel formed from a crucible, the crucible substantially comprising a material of high electrical resistivity or high magnetic permeability;
• inductively heating the container by supplying a current to an at least one induction coil consisting of a cable wound of multiple conductors isolated from each other, the at least one induction coil surrounding the container and being electrically and thermally isolated from the container by an isolation sleeve;
• and
• adjusting the frequency of the current so that the depth of penetration into the crucible of the magnetic field generated by the current in the at least one induction coil is in the range of from half the thickness to the thickness of the container, whereby the metal is heated by the conduction of heat from the container to the metal.

A process for heating a metal comprising the steps of:

• placing the metal in a container formed substantially from a material of high electrical resistivity or high magnetic permeability;
• inductively heating the container by supplying a current to an at least one induction coil consisting of a cable wound of multiple conductors isolated from each other, the at least one induction coil surrounding the container and being electrically and thermally isolated from the container by an isolation sleeve;
• and
• adjusting the frequency of the current so that the depth of penetration into the crucible of the magnetic field generated by the current in the at least one induction coil is in the range of from half the thickness to the thickness of the container, whereby the metal is heated by the conduction of heat from the container to the metal.