Electric heater assembly
OwnerC. Edward Eckertinventor
Life of this patent
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Abstract
An improved electric heater assembly suitable for heating molten metal, the electric heater assembly having a tube comprised of a closed end suitable for immersing in the molten metal. The tube is fabricated from a composite material comprised of a metal having a coefficient of thermal expansion of less than 10.times.10.sup.-6 in/in/.degree. F. and having an outside surface to be exposed to the molten metal coated with a refractory resistant to attack by the molten metal; and an electric heater located in the tube in heat transfer relationship therewith.
Claims27
An electric heater assembly suitable for heating molten metal, the electric heater assembly comprised of:
- (a) a tube having a closed end suitable for immersing in said molten metal, the tube fabricated from a composite material comprised of a metal case having a thermal coefficient of expansion of less than 10.times.10.sup.-6 in/in/.degree. F.,
- (i) the metal case fabricated from a metal selected from the group consisting of titanium or titanium alloy stainless steel nickel based alloys and iron based alloys;
- and
- (ii) the tube having an outside surface to be exposed to said molten metal coated with a refractory coating having a coefficient of expansion less than 10.times.10.sup.-6 in/in/.degree. F. and being resistant to attack by said molten metal;
- (b) an electric heating element located in said tube in heat transfer relationship therewith for adding heat to said molten metal;
- and
- (c) a powdered contact medium provided in said tube between said heating element and said tube, the contact medium having the ability to conduct heat from said heating element to said tube to improve heat transfer.
An electric heater assembly suitable for heating molten metal, the electric heater assembly comprised of a tube having a closed end suitable for immersing in said molten metal, the tube fabricated from a composite material comprised of:
- (a) a base metal layer of a titanium alloy having a coefficient of expansion less than 10.times.10.sup.-6 in/in/.degree. F.;
- (b) a bond coat bonded to an outside surface of said base layer to coat said surface to be exposed to said molten metal;
- (c) a refractory layer bonded to said bond coat, the refractory layer resistant to attack by said molten metal, the refractory layer having a coefficient of expansion less than 10.times.10.sup.-6 in/in/.degree. F.;
- (d) an electric heating element positioned in said tube in heat transfer relationship;
- and
- (e) a contact medium provided in said tube between said heating element and said tube to fill air gaps between said element and said tube, the contact medium having the ability to conduct heat from said element to said tube and improve heat transfer.
A method of forming an electric heater assembly for heating molten metal, the electric heater assembly comprised of a tube having a closed end suitable for immersing in said molten metal, the tube fabricated from a composite material comprising the steps of:
- (a) providing a tube of metal selected from the group consisting of a titanium based alloy, nickel based alloy, iron based alloy and stainless steels, said metal having a coefficient of thermal expansion of less than 8.times.10.sup.-6 in/in/.degree. F.;
- (b) providing a contact medium in said tube;
- (c) locating an electric heater in said tube;
- (d) forming said tube about said heating element thereby compressing said contact medium;
- (e) applying a bond coat bonded to an outside surface of said metal to coat said surface to be exposed to said molten metal;
- and
- (f) applying a refractory layer to said bond coat, the refractory layer resistant to attack by said molten metal, the refractory layer having a coefficient of expansion less than 10.times.10.sup.-6 in/in/.degree. F.
An electric heater assembly suitable for heating molten metal, the electric heater assembly comprised of:
- (a) a tube having a closed end suitable for immersing in said molten metal, the tube fabricated from a composite material comprised of metal case having a thermal coefficient of expansion of 10.times.10.sup.-6 in/in/.degree. F. and having an outside surface to be exposed to said molten metal coated with a refractory resistant to attack by said molten metal;
- (b) an electric heating element located in said tube in heat transfer relationship therewith for adding heat to said molten metal;
- and
- (c) a thermocouple positioned in said tube for purposes of monitoring the heat output of said heating element and preventing said heating element from overheating.
A composite material for use with molten metal, the composite material having a tensile strength of greater than 30 ksi and being resistant to attack by the molten metal, the composite material comprising:
- (a) a base layer of metal having an expansion coefficient of less than 10.times.10.sup.-6 in/in/.degree. F.;
- (b) a bond coating applied to a surface of said base layer, the bond coating having a thickness in the range of 0.1 to 8 mils and a thermal coefficient of expansion of less than 10.times.10.sup.-6 in/in/.degree. F.;
- (c) a protective refractory coating applied to said bond coating, the refractory coating having a coefficient of expansion of less than 10.times.10.sup.-6 in/in/.degree. F., said refractory coating bonded to said bond coating;
- and
- (d) a molten metal substantially non-wetting coating applied to said refractory coating, said non-wetting coating selected from one of the group consisting of silicon carbide, boron nitride, silicon aluminum oxynitride and silicon nitride.
A composite material for use with molten aluminum, the composite material having a tensile strength of greater than 30 ksi and being resistant to attack by said molten aluminum, the composite material comprising:
- (a) a base layer of titanium base alloy having an expansion coefficient of less than 5.times.10.sup.-6 in/in/.degree. F.;
- (b) a bond coating applied to a surface of said base layer, the bond coating having a thickness in the range of 0.1 to 5 mils and a thermal coefficient of expansion of less than 10.times.10.sup.-6 in/in/.degree. F.;
- (c) a protective refractory coating having a coefficient of expansion of less than 10.times.10.sup.-6 in/in/.degree. F. and resistant to attack by said molten aluminum, said refractory coating bonded to said bond coating and having a thickness in the range of 4 to 22 mils, the refractory coating having a porosity of 3 to 22%;
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- (d) a boron nitride coating applied to said refractory coating, the boron nitride being substantially non-wettable by said molten aluminum.
Dependencies are inferred from the claim text.