US3092681A - Electric resistance furnaces and the like - Google Patents
Electric resistance furnaces and the like Download PDFInfo
- Publication number
- US3092681A US3092681A US840932A US84093259A US3092681A US 3092681 A US3092681 A US 3092681A US 840932 A US840932 A US 840932A US 84093259 A US84093259 A US 84093259A US 3092681 A US3092681 A US 3092681A
- Authority
- US
- United States
- Prior art keywords
- elements
- furnace
- furnace chamber
- furnaces
- electric resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000010438 heat treatment Methods 0.000 claims description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 12
- 238000002791 soaking Methods 0.000 claims description 12
- YXTPWUNVHCYOSP-UHFFFAOYSA-N bis($l^{2}-silanylidene)molybdenum Chemical compound [Si]=[Mo]=[Si] YXTPWUNVHCYOSP-UHFFFAOYSA-N 0.000 claims description 6
- 229910021343 molybdenum disilicide Inorganic materials 0.000 claims description 6
- 239000000377 silicon dioxide Substances 0.000 claims description 6
- 235000012239 silicon dioxide Nutrition 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 4
- 238000007669 thermal treatment Methods 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 239000000571 coke Substances 0.000 description 16
- 239000010410 layer Substances 0.000 description 8
- 239000002893 slag Substances 0.000 description 8
- 239000011449 brick Substances 0.000 description 7
- 229910016006 MoSi Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000013021 overheating Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000011241 protective layer Substances 0.000 description 2
- 229910021332 silicide Inorganic materials 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 239000000440 bentonite Substances 0.000 description 1
- 229910000278 bentonite Inorganic materials 0.000 description 1
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910000953 kanthal Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/62—Heating elements specially adapted for furnaces
Definitions
- the present invention relates to an electric resistance furnace and particularly the invention relates to a soaking pit furnace for the thermal treatment in the air of steel. It is not new to heat soaking pit furnaces electrically.
- an electrically heated soaking pit furnace in which channels are provided in the furnace chamber to receive strings of petrol coke. Heavy carbon electrodes connect the ends of these strings to a source of current having a low voltage in comparison with the effect and the strings become glowing when a high current is applied.
- currents having a magnitude of 3000 A. or 4000 A. and even up to 7000 A. are required.
- the second problem which is closely related to the one just mentioned, consists in that, at the regularly required cleanings and services, i.e. particularly the removal of slags in the form of scalings from ingots, for instance, and the checking of the whole petrol coke strings, it is necessary to work with a rather high effect in the whole furnace until the last ingot has been withdrawn, before the furnace may be switched off for cooling. This means that the furnace is badly utilized in the last period before the maintenance works. In this context it should be mentioned that, if a fault occurs in the petrol coke strings, it is generally necessary to switch off the whole furnace for cooling, which means a long period of waiting, before any adjustment is possible.
- resistor elements manufactured by a powder metallurgical method and composed mainly of heat resistant silicides.
- molybdenum disilicide, MoSi with possible remainders of oxides, carbides or borides is used, in which case, besides molybdenum, one or more of the elements Ti, Zr, m, V, Nb, Ta, Cr and W may be used for the metal atom.
- particles detrimental to such silicide containing elements may be formed.
- the main object of the present invention is to solve the above recited problems.
- FIGURE 1 shows a vertical longitudinal section through a portion of a soaking pit furnace
- FIGURE 2 is a horizontal section FIG. 1;
- FIGURE 3 shows a cross section through the furnace in FIG. 1;
- FIGURE 4 shows a vertical section through a portion of a soaking pit furnace in which the elements are inserted through the furnace wall;
- FIGURE 5 shows a section along the line VV in FIG. 4;
- FIGURE 6 shows an element in diagrammatic perspective
- FIGURE 7 shows a modification furnace according to FIG. 4.
- the soaking pit furnace shown in FIGS. 1-3 comprises two juxtaposed rows of heating pits 20, each row containing e.g. ten pits so that the charging capacity amounts to twenty ingots.
- the furnace is especially intended for heating ingots to rolling temperature, the operating temperature preferably amounting to about 1300 C.
- the ingots are introduced from above int-o the heating pits which, for this purpose, are open at the top and each closed by a heavy cover 21. These covers 21 may be lifted and moved aside by means of a traverse 22, FIGS. 1 and 3.
- the invention uses a great number of resistor elements 26 which are introduced into the furnace chamber independently of each other and in such a way that they may be replaced separately from the outside while the furnace is in operation.
- the resistor elements 26 consist of two parallel and slightly spaced lead in electrodes 26A extending through a common hole in the wall of the furnace and a substantially hairpin-shaped glow zone portion 26B wholly or for the greater part consisting of molybdenum disilicide, Mosi which depends along the inner side of the furnace wall.
- vertical webs 27, ZS may be placed'between the glow zone portions of the elements to prevent mechanical damage to the glow zones.
- the resistor elements of the furnace according to the invention may be connected in the manner most suitable in view of the construction of the furnace. For instance, it is. possible to connect the elements 26 in groups each comprising four juxtaposed heating pits 20, and each such group of elements being controlled separately.
- the elements of each group may be interconnected as desired according to the voltage of the source of current and the dimensions of the elements. As the resistance value of the elements is constant during the operation-contrary to that obtained when using petrol coke strings-no regulating transformer is required. An ordinary transformer is sufficient and the furnace temperature can be controlled by simply switching on and off the elements of the group in question by means of contactors or the like.
- the heating of a soaking pit furnace by means of the elements as disclosed above constitutes a considerable improvement over the prior art and involves per se a great progress when it is desired to obtain a more or less continuous operation of furnaces of the kind mentioned.
- a considerable amount of slag containing i.e. scalings and surface particles exfoliated from the ingots during the heating collects on the bottom of the furnace.
- This slag may cause disturbances in the operation after some time, by short-circuiting the elements or the like, for instance. This means-even if the elements are intact-that it might become necessary to switch off the furnace and let it cool off to make it possible to remove the slag.
- the heating of the ingots in the furnace according to the invention occurs by radiation, although the elements of several heating pits are disposed along one wall only. Owing to the extremely high temperature level in the furnace, however, a temperature equalization takes place in such a way that also e.g. the supporting intermediate wall 34 between the two rows of heating pits serves as a radiating surface.
- electrical elements 35 having the shape of a hairpin or substantially the shape of a hairpin are inserted through the wall 36 of the furnace, the glow zone portion 35A of the elements. depending substantially vertically along the inner side of the furnace wall 36 and the two lead in electrodes 35B projecting through the wall of the furnace.
- the elements consist substantially of molybdenum disilicide, MoSi which renders possible an operating temperature of as much as l600-l700 C.
- the elements are bent at the portion where the glow zone portion 35A merges with the lead in electrodes 358 so as to include an angle of about 120.
- the elements maybe bent more or less, e.g. perpendicularly, or they may be arched.
- the elements may also be arranged depending vertically from the vault of the furnace.
- the wall of the furnace is provided with inlet openings 37 larger than strictly necessaryy for the insertion of the elements.
- the inlet openings 37 are partly filled with a casting mass 38' in which one or more juxtaposed inlet holes 39 for the elements are provided.
- the lead in electrodes 35B of the elements rest in notches 40 in the casting mass 38 and in the refractory bricks 41.
- Other refractory bricks 42 and 43 are placed on the lead in electrodes and the refractory bricks 41 and the mass 38, respectively.
- Shoulders 38A of the mass 38 prevent the innermost bricks 42 of each element from sliding off into the furnace. The elements may easily be withdrawn after release of the contact pieces 44 and the element holders 45 and removal of the refractory bricks 41, 42 and 43.
- the sealing and securing ofthe elements is effected by fitting the parts mentioned in the reversed order.
- the refractory bricks 41, 42 and 43 as well as the design of the mass 38 mustbe adapted to the shape of theelements in each separate case.
- the resistor elements may contain other metals or oxides which, on oxidation of the elements, are partly converted into an oxidiferous material that forms a flowable superficial layer on the elements together with SiO
- the elements may be composed of MoSi and a ceramic binding agent which is formed entirely or partly of an easily fusible clay, such as bentonite, for instance, at the sintering of the elements. It is particularly advantageous to use an easily fusible clay as binding agent for MoSi as thereby the protective layer is given such a composition that it may flow off without impeding the protective action against oxidation.
- a heating source consisting of elongated, hairpin-shaped resistor elements containing molybdenum disilicide, MoSi having the property of producing on their surface a layer containing silicon dioxide when heated to high temperatures, because of the action of the oxygen of the air, said elements each having a glow portion depending vertically into the furnace chamber, and each element having two lead-in electrodes extending to the exterior of the furnace chamber at a short distance from one another through a common opening so that the elements are replaceable individually while the furnace is functioning, the composition and arrangement of the resistor elements being such, that in operation the superficial layer containing silicon dioxide together with oxide particles deposited on the glow zone of the elements after separation from the steel, becomes flowing and under the action of gravity flows slowly downwards along the length of the resistance elements, while a new superficial layer is being continuously formed, the excess simultaneously leaving the elements in the form of drops so that impurities adhered to the surface of the elements are removed.
Landscapes
- Resistance Heating (AREA)
- Furnace Details (AREA)
- Tunnel Furnaces (AREA)
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE887458 | 1958-09-22 | ||
| SE1120058 | 1958-12-03 | ||
| SE115159 | 1959-02-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3092681A true US3092681A (en) | 1963-06-04 |
Family
ID=27354264
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US840932A Expired - Lifetime US3092681A (en) | 1958-09-22 | 1959-09-18 | Electric resistance furnaces and the like |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3092681A (de) |
| DE (1) | DE1127009B (de) |
| GB (2) | GB925899A (de) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3373239A (en) * | 1964-06-18 | 1968-03-12 | Siemens Planiawerke Ag | High-temperature electric furnace with molybdenum silicide heater elements |
| US4462963A (en) * | 1982-03-05 | 1984-07-31 | Leco Corporation | Analytical furnace |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3620203A1 (de) * | 1986-06-16 | 1987-12-17 | Riedhammer Ludwig Gmbh | Heizelement |
| CN102954691A (zh) * | 2012-10-29 | 2013-03-06 | 苏州新长光热能科技有限公司 | 一种坑式铝锭加热炉 |
| CN106288690A (zh) * | 2016-09-23 | 2017-01-04 | 丹阳市恒泰电炉有限公司 | 燃气烘干炉 |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1498990A (en) * | 1921-07-05 | 1924-06-24 | Beyer Robert | Electric furnace |
| US1532017A (en) * | 1923-04-18 | 1925-03-31 | Gen Electric | Enameling apparatus |
| US1547623A (en) * | 1922-08-11 | 1925-07-28 | Electric Heating Apparatus Com | Electric furnace |
| US1659946A (en) * | 1926-03-12 | 1928-02-21 | Western Electric Co | Apparatus for heat treating articles |
| US1776823A (en) * | 1923-05-31 | 1930-09-30 | David L Summey | Heating apparatus |
| US1853382A (en) * | 1930-02-18 | 1932-04-12 | Hevi Duty Electric Co | Supporting means for electrical heating elements |
| US1901499A (en) * | 1924-05-19 | 1933-03-14 | Frank A Fahrenwald | Electric furnace |
| US2618671A (en) * | 1948-12-28 | 1952-11-18 | Norton Co | Tunnel kiln |
| US2622304A (en) * | 1950-10-02 | 1952-12-23 | Climax Molybdenum Co | Refractory |
| US2650254A (en) * | 1953-08-25 | Side heater | ||
| US2745928A (en) * | 1952-10-06 | 1956-05-15 | American Electro Metal Corp | Heater bodies and their production |
| US2745932A (en) * | 1953-06-03 | 1956-05-15 | American Electro Metal Corp | Electric resistor |
| DE1060066B (de) * | 1958-02-18 | 1959-06-25 | Siemens Planiawerke Ag | Heizelement fuer elektrische Widerstandsoefen fuer Temperaturen oberhalb 1600íÒ C |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1010668B (de) * | 1955-08-31 | 1957-06-19 | Siemens Planiawerke A G Fuer K | Heizelement fuer elektrische Widerstandsoefen mit Betriebstemperaturen ueber 1500íÒC |
| DE1027820B (de) * | 1957-01-25 | 1958-04-10 | Siemens Planiawerke Ag | Heizelement mit schleifenfoermigem Gluehteil fuer elektrische Widerstandsoefen |
-
1959
- 1959-09-14 DE DEA32857A patent/DE1127009B/de active Pending
- 1959-09-18 US US840932A patent/US3092681A/en not_active Expired - Lifetime
- 1959-09-18 GB GB31918/59A patent/GB925899A/en not_active Expired
- 1959-10-29 GB GB36783/59A patent/GB868442A/en not_active Expired
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2650254A (en) * | 1953-08-25 | Side heater | ||
| US1498990A (en) * | 1921-07-05 | 1924-06-24 | Beyer Robert | Electric furnace |
| US1547623A (en) * | 1922-08-11 | 1925-07-28 | Electric Heating Apparatus Com | Electric furnace |
| US1532017A (en) * | 1923-04-18 | 1925-03-31 | Gen Electric | Enameling apparatus |
| US1776823A (en) * | 1923-05-31 | 1930-09-30 | David L Summey | Heating apparatus |
| US1901499A (en) * | 1924-05-19 | 1933-03-14 | Frank A Fahrenwald | Electric furnace |
| US1659946A (en) * | 1926-03-12 | 1928-02-21 | Western Electric Co | Apparatus for heat treating articles |
| US1853382A (en) * | 1930-02-18 | 1932-04-12 | Hevi Duty Electric Co | Supporting means for electrical heating elements |
| US2618671A (en) * | 1948-12-28 | 1952-11-18 | Norton Co | Tunnel kiln |
| US2622304A (en) * | 1950-10-02 | 1952-12-23 | Climax Molybdenum Co | Refractory |
| US2745928A (en) * | 1952-10-06 | 1956-05-15 | American Electro Metal Corp | Heater bodies and their production |
| US2745932A (en) * | 1953-06-03 | 1956-05-15 | American Electro Metal Corp | Electric resistor |
| DE1060066B (de) * | 1958-02-18 | 1959-06-25 | Siemens Planiawerke Ag | Heizelement fuer elektrische Widerstandsoefen fuer Temperaturen oberhalb 1600íÒ C |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3373239A (en) * | 1964-06-18 | 1968-03-12 | Siemens Planiawerke Ag | High-temperature electric furnace with molybdenum silicide heater elements |
| US4462963A (en) * | 1982-03-05 | 1984-07-31 | Leco Corporation | Analytical furnace |
Also Published As
| Publication number | Publication date |
|---|---|
| GB868442A (en) | 1961-05-17 |
| GB925899A (en) | 1963-05-15 |
| DE1127009B (de) | 1962-04-05 |
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