|Publication number||US2955145 A|
|Publication date||Oct 4, 1960|
|Filing date||Jul 14, 1959|
|Priority date||Jul 16, 1958|
|Publication number||US 2955145 A, US 2955145A, US-A-2955145, US2955145 A, US2955145A|
|Inventors||Gustav Schrewelius Nils|
|Original Assignee||Kanthal Ab|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (1), Referenced by (28), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
2,955,145 Patented Oct. 4, 1960 THERMO-ELE CTRIC ALLOYS Nils Gustav Schrewelius, Hallstahammar, Sweden, assignor to AB Kanthal, Hallstahammar, Sweden, a corporation of Sweden N Drawing. Filed .luly1'4, 1959, Ser. No. 826,916 Claims priority, application Sweden July 16, 1958 4 Claims. (Cl. "136-5) 7 This invention relates to thermo-electric alloys which are particularly suitable for use at very elevated temperatures, and which consist essentially of an intermetallic composition containing molybdenum, silicon and aluminium.
It is known (J. Appl. Phys. 24, p. 498, 1953), that MoSi within the range from -60 C. to +600 C. exhibits, with respect to platinum, a thermal which corresponds approximately to that of copper. Thus, highly temperature-resistant molybdenum disilicide can be used in a thermo-couple. It is also known (Austrian patent specification 193,632) that molybdenum disilicide with 3040% Si and various additions of other scaleresistant silicides or oxides or silicon carbide may be used in thermo-couples at elevated temperatures. Additions suggested in this patent are titanium silicide, tungsten silicide, chromiumsilicide, aluminium oxide, thorium oxide, titanium oxide, and zirconium oxide. Up to 25% of the silicon atoms of the molybdenum silicide may be replaced by carbon, boron or nitrogen.
"the thermo-electric alloys according to the present invention are distinguished from such previously known alloys in that they comprise molybdenum disilicide wherein 20-60 atomic percents of silicon have been replaced by aluminium. As a result, the crystal structure of the molybdenum disilicide, which is normally of the tetragonal C 11 lattice type, is converted entirely to the hexagonal C 40 lattice type. These lattice types are well known to those skilled in the art. (Compare Schwarzkopf et al., Refractory Hard Metals, 1953.) This conversion of the crystal structure results, surprisingly, in a considerably increased thermal for the alloys according to the present invention with respect to pure M0Si for example. Other advantages of these alloys are high mechanical strength, high oxidation resistance, and resistance to thermal shocks. By variations of the content of aluminium variations in the thermal E.M.F. can be readily obtained, and these variations are not accompanied by any significant deterioration of the mechanical or chemical properties of the alloys. In this respect, the alloys according to the present invention are distinguished from the previously known thermo-electric alloys based on molybdenum silicide.
The thermo-electric alloys according to the invention may also, if desired, comprise admixtures of other metals. Thus, up to 50 atomic percents as a maximum of molybdenum can be replaced by one or more of the metals titanium, zirconium, hafnium, tantalum, niobium, vanadium, tungsten, and chromium. The composition of the thermo-electric alloys according to the present invention may thus be expressed as wherein 0.2 x 0.6 and 0 y 0.5, and M represents one or more of the metals Ti, Zr, Hf, Ta, Nb, V, W or C1.
When the alloy contains no metal M, i.e. when y is 0,
then the alloy has the composition Mo(Si Al When a metal M is present, y preferably has a value of at least 0.05.
Thermo-couples comprising the alloys according to the invention are preferably made by a powder metallurgical process by sintering after admixture with 0.5 to 20 Wt. percent of a ceramic binding substance. Preferably, the ceramic binding substance is composed essentially of very finely powdered silica. However, it may also contain other oxides or silicon carbide. Conveniently, the final sintering is carried out in air, in which case a certain internal oxidation takes place. The ceramic component should preferably not exceed 30 percent'by weight of the material.
Thermocouples having one leg comprised of an alloy according to the invention, and another leg composed of MoSi for example, may also advantageously be used as heating resistors for producing high temperatures. In this case, the device defined by the two legs is suitably connected to serve as a thermocouple only for the short periods when the thermo-voltage is measured and to serve as an electrical heating resistor for the remaining periods. The resulting thermo-voltage may be used in practice for controlling the current supply to the resistor over a relay. Preferably the welded joint between the two legs should be disposed internally of the furnace, at or adjacent a lead-in electrode, so that it is not subjected to higher temperatures than those of the furnace room.
The following example illustrates the use of alloys according to the invention in a thermo-couple for 1600 to 1700 0:
The thermal increased regularly with the temperature and attained, inter alia, the following values:
Millivolts 800 C. 10 1000" C. 14 1200 C. l9 1400 C 24 1600 C 31 Both legs were 6 mm. cylindrical rods, made by extrusion and sintering, and joined by resistance butt welding. The most oxidation resistant negative leg may also, as an alternative, be formed as a tube which is closed at one end and surrounds the rod-shaped positive leg.
The above described leg combination may also be used as an electrical heating resistor and should then have the following dimensions: the positive leg is formed as a hair pin having one portion of 6 mm. diameter which acts as a glowing zone. One end of the loop is enlarged to 14 mm. and is long enough to extend out from the furnace as a cold lead-in electrode. The other end is Welded to a 9 mm. negative leg, which is similarly elongated to act as a cold lead-in electrode. As the alloy forming the negative leg has about half as high a specific resistance at 1600 C. as the alloy forming the positive leg, this lead-in electrode will also remain cool enough without special cooling devices. For the same reason, the welded joint will attain the same temperature as the furnace room, provided that it is disposed appropriately in the furnace, notwithstanding the fact that it is disposed adjacent the hot glowing Zone.
The alloy in accordance with the present invention described in the above example and used as the positive leg, was formed as follows; all parts being by weight; 98 parts of a metal powder made as set forth below were admixed with two parts of bentonite as a ceramic binding substance. Then this mixture was formed, dried and placedin a metal tube and sintered at 1400" C. for 30 minutes in an atmosphere of technical hydrogenl Final sintering was carriedout at 1550 C. in air for 2 minutes. The above mentionedmetal powder was of the composition (MoojjTid g)(Si0 8A1U 2 )2 and was formed in such a manner that Mo, Ti, Si and Al in theoretic quantities were heated in hydrogen gas to 1100 C. to start an exothermic reaction. The resulting sponge was then milled in a ball mill to a grain size of l-10 microns. The negative leg was formed in the same manner, using 95% MoSi and .5 bentonite.
- It'will be understood that thermocouples formed by the use of the alloys of the present invention may have' 4- in thermo-couples for elevated temperatures in oxidizing atmospheres, said alloy being of the hexagonal C 40 lattice type and having the composition (Mo M (Si 5;Al,;) Where M is at least one of the metals Ti, Zr, Hf, Nb, Ta, V, W, Cr, x has a value of 0.2 to 0.6 and y has a value of 0 to 0.5.
2. A thermo-electric alloy containing molybdenum, silicon and at least one other metal and adapted to be used in thermo-couples for elevated temperatures in oxidizing atmospheres, said alloy being ofthe hexagonal C 40 lattice type and having the composition (Mo Ti o.a o.2)z-
3. A thermo-couple having a positive leg comprising an alloy having the composition (Mo M (Si Al where M is at least one of the metals Ti, Zr, H f, Nb, Ta, V, W, Cr, x has a value of 0.2 to 0.6 and y has a value of 0 to 025, and a negative leg comprising Mosi r 4. A thermo-couple as defined in claim 3, wherein the alloy has the composition (Mo Ti )(Si Al References Cited in the file of'this'patent UNITED STATES PATENTS 2,745,928 Glasser May 5, 1955
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2745928 *||Jun 3, 1953||May 15, 1956||American Electro Metal Corp||Heater bodies and their production|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US2998394 *||May 25, 1960||Aug 29, 1961||Union Carbide Corp||Electrical resistor composition|
|US3051924 *||Jul 6, 1959||Aug 28, 1962||Kanthal Ab||Sintered electric resistance heating elements and methods of producing such elements|
|US3072733 *||Jul 17, 1961||Jan 8, 1963||Daizaburo Shinoda||Thermoelectric generator|
|US3248346 *||Oct 16, 1962||Apr 26, 1966||Kanthal Ab||Heat-resistant and oxidation-proof materials containing molybdenum disilicide|
|US3256696 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256697 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256698 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256699 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256700 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256701 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3256702 *||Jan 29, 1962||Jun 21, 1966||Monsanto Co||Thermoelectric unit and process of using to interconvert heat and electrical energy|
|US3275572 *||Oct 11, 1961||Sep 27, 1966||Ruben Samuel||Refractory composition and electrical resistance made therefrom|
|US3285017 *||May 27, 1963||Nov 15, 1966||Monsanto Co||Two-phase thermoelectric body comprising a silicon-germanium matrix|
|US3285018 *||May 27, 1963||Nov 15, 1966||Monsanto Co||Two-phase thermoelectric body comprising a silicon-carbon matrix|
|US3285019 *||May 27, 1963||Nov 15, 1966||Monsanto Co||Two-phase thermoelectric body comprising a lead-tellurium matrix|
|US3298777 *||Dec 12, 1961||Jan 17, 1967||Du Pont||Thermoelectric compositions of nbxta1-xsiyge2-y|
|US3330703 *||May 18, 1962||Jul 11, 1967||Leon Podolsky||Thermoelectric elements of oriented graphite containing spaced bands of metal atoms|
|US3343373 *||May 27, 1963||Sep 26, 1967||Monsanto Co||Two-phase thermo-electric body comprising a boron-carbon matrix|
|US3523832 *||Jun 9, 1969||Aug 11, 1970||Siemens Ag||Thermogenerator with germanium-silicon semiconductors|
|US4486651 *||Jan 24, 1983||Dec 4, 1984||Nippon Soken, Inc.||Ceramic heater|
|US4644133 *||Feb 25, 1986||Feb 17, 1987||Nippondenso Co., Ltd.||Ceramic heater|
|US5156688 *||Jun 5, 1991||Oct 20, 1992||Xerox Corporation||Thermoelectric device|
|US5474619 *||May 4, 1994||Dec 12, 1995||The United States Of America As Represented By The Secretary Of Commerce||Thin film high temperature silicide thermocouples|
|US6563095 *||May 19, 2000||May 13, 2003||Sandvik Ab||Resistance-heating element|
|US7164103 *||Mar 7, 2003||Jan 16, 2007||Sandvik Intellectual Property Aktiebolag||Electrical heating resistance element|
|US8053710 *||Mar 6, 2003||Nov 8, 2011||Sandvik Intellectual Property Aktiebolag||Method of making a heating element of the molybdenum silicide type and a heating element|
|US20050236399 *||Mar 6, 2003||Oct 27, 2005||Sandvik Ab||Method of marking a heating element of the molybdenum silicide type and a heating element|
|US20050252909 *||Mar 7, 2003||Nov 17, 2005||Jan Andersson||Electrical heating resistance element|
|U.S. Classification||136/239, 252/519.12, 419/19, 419/20, 136/240, 419/10, 136/236.1, 338/48|
|International Classification||H01L35/12, H01L35/20|