CA1226418A - Process for preheating a nozzle - Google Patents
Process for preheating a nozzleInfo
- Publication number
- CA1226418A CA1226418A CA000455273A CA455273A CA1226418A CA 1226418 A CA1226418 A CA 1226418A CA 000455273 A CA000455273 A CA 000455273A CA 455273 A CA455273 A CA 455273A CA 1226418 A CA1226418 A CA 1226418A
- Authority
- CA
- Canada
- Prior art keywords
- nozzle
- metal
- process according
- molten metal
- substance
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0637—Accessories therefor
- B22D11/064—Accessories therefor for supplying molten metal
- B22D11/0642—Nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
- B22D41/60—Pouring-nozzles with heating or cooling means
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
- Continuous Casting (AREA)
Abstract
A B S T R A C T
A process for preheating a nozzle, in particular a nozzle for feeding metal between two bands, belt-like tracks or the like of a mound of a casting machine with moving mound wall is such that, before the actual metal to be cast, at least one substance at a different temperature than that of the said metal is passed through the nozzle.
Thus before casting a ferrous metal, for example steel, first a non-ferrous metal for example aluminum and subse-quently a ferrous metal with a lower melting point than that of the metal to be cast is passed through the nozzle.
A process for preheating a nozzle, in particular a nozzle for feeding metal between two bands, belt-like tracks or the like of a mound of a casting machine with moving mound wall is such that, before the actual metal to be cast, at least one substance at a different temperature than that of the said metal is passed through the nozzle.
Thus before casting a ferrous metal, for example steel, first a non-ferrous metal for example aluminum and subse-quently a ferrous metal with a lower melting point than that of the metal to be cast is passed through the nozzle.
Description
~2~:6418 Process for preheating a nozzle The invention relates to a process for preheating a no-ale, in particular a nozzle for feeding metal between two bands, belt-like tracks or the like of a mound for a con-tenuous casting machine with moving mound walls.
Machines for continuous casting in particular ferrous and nonferrous metals have been developed and namely such that the mound features continuously moving walls. These include machines where the metal to be cast is poured 10 between two moving steel bands or belts, in particular the well known Hazelitt strip casters e.g. according to the US
patent 2,640,235.
Also known are other machines in which the cast product obtains its shape by means of mound halves joined together 15 from a pair of endless belts like caterpillar tracks.
At the pouring end the mound halves face each other and move thus over a specific distance in which they form the actual mound. The mound halves then separate and after a short time return to the pouring or casting end.
20 With, in particular, machines featuring caterpillar track type mounds for casting relatively thin strips e.g. strips only 20 mm thick and less, it is the feeder nozzle for the metal which presents the greatest problems. One of the main reasons for this is that there are few materials 25 which are able to withstand the high temperatures of the metal flowing through it. Graphite for example is one of ~Z2641~3 the few materials able to meet the necessary require-mints. On the other hand graphite has the disadvantage of high thermal conductivity, as a result of which the heat is conducted away from the melt so quickly that the metal has a tendency to solidify in the nozzle.
In any case the parts of the feeder nozzle which come into contact with the molten metal must be made of a refractory material which e.g. when casting aluminum comprises a mixture of 30 % diatomaceous earth (almost pure silica in 10 the form of microscopic cells), 30 % long asbestos fires, 20 % sodium silicate (dry weight) and 20 % chalk (to form calcium silicate.
For casting steel one can use in particular ZrO2 for the nozzle material, or ZrSiO4 containing various amounts of 15 ZrO2; for cost saving purposes the nozzle can also be made of two materials. The ZrO2 used is a stabilized, fine con-amid material with very accurately controlled porosity.
Such a structure is able to accommodate the change in volt use occurring in the Zr2 in such a way that problems of 20 cracking are avoided.
Although the above feeder nozzles made of a refractory ma-tonal feature good thermal barrier properties and low heat capacity, their basic disadvantage is that, because of lack of homogeneity in terms of chemical composition 25 and mechanical properties, the material employed exhibits an up-take of moisture, irreversible changes in chemical composition on heating up to the operating temperature and a related further embrittlement or lower mechanical 1;~264~3 strength and - connected with this - normally permits the nozzle to be used only once. In spite of the above men-toned low thermal capacity and poor thermal conductivity of the known ceramic material when the molten metal is poured for the first time unto the nozzle, the nozzle is exposed to extreme thermal shock with the result that the sudden thermal stress created inside the nozzle can cause it to break apart or at least to crack. A further problem is the so called freezing-up of the nozzle as the metal to 10 be cast comes into contact with the cold inner surface of the nozzle.
In order to avoid such thermal shock or freezing up of the nozzle it has been proposed e.g. in the German patent pub-ligation DE-05 28 16 500 that the whole nozzle should come 15 prose a plurality of hollow sections-lying adjacent to each other held together in a metal holder and made of a material which resists melting and is heat resistant -acting as outlet nozzles, and such that channels for heat-in the device are provided parallel to the channels 20 through which the melt passes. With the aid of such a heating facility it is possible to heat the nozzle up to the necessary melt pouring temperature before casting starts. This can be done so slowly that no thermal shock occurs or thermal stresses are created. On the other hand 25 such a nozzle is complicated in its make up and in par-shackler the heating mechanism has a disturbing influence during normal operation i.e. after the start-up phase is past.
The object of the present invention is therefore to dove-12264~8 lop a much simpler possibility for preheating a nozzle to the desired temperature before the actual start of feeding the metal to be cast.
This object is achieved by way of the invention in that, before the actual metal to be cast is passed through the nozzle, at least one substance at a temperature other than of the said metal is passed through the nozzle.
This extremely simple idea is not only very inexpensive and uncomplicated, but enables conventional nozzles to be 10 used and eliminates the need for additional heating fact-titles.
This substance / these substances should, according to the invention, be at a temperature higher than that of the me-tat to be cast. This process has the advantage that only a 15 small amount of preheating substance is required and also the time of contact between substance and nozzle can be kept short. However, this requires considerable experience with regard to heat transfer between substance and nozzle material.
20 Preference should be given therefore to a substance or substances which is / are at a lower temperature than the metal to be cast. This prevents the nozzle being heated to too high a temperature - which would also cause the metal to be overheated and make additional cooling in the mound 25 necessary.
12264~8 The substance to be passed through the nozzle before the metal which is to be cast is preferably another metal. As a rule an inexpensive metal is suitable for this purpose.
Before introduction into the nozzle this metal can be heated in a special container to the desired temperature, be this above or below that of the metal to be cast.
Preferred, however, is a metal of lower density than the metal to be cast. This way the nozzle and in particular its side walls which limit the width of the strip are not 10 suddenly subjected to excessive pressure at the start of casting. If for example a ferrous metal - in particular steel - is to be cast, then aluminum may be employed as it is less dense than steel and its oxide skin prevents the metal penetrating slits or the like. However, this 15 could lead to contamination of the metal to be cast - in this case steel - or at least the first of the metal to be cast. For this reason it is proposed, in accordance with the invention, when casting a ferrous metal to allow an-other ferrous metal e.g. cast iron (grew cast iron) to be 20 passed through the nozzle before the actual casting be-gins.
It is also within the scope of the invention for a pour-amity of the same ox different substances at different temperatures to be passed first through the nozzle. By way 25 of example the following steps in the process should be mentioned: The nozzle is heated to a temperature of about 200 - 250C with hot air. Then molten aluminum at a them-portray of about 760C is introduced. This is followed by grew cast iron at a temperature of about 1200 C. After 30 this the steel which is to be cast can then be introduced 1;2Z6418 without problem into the nozzle.
To this end, and within the scope of the invention, the tundish upstream of the nozzle features a plurality of clambers for the various substances or metals. In order that the metal which is to be cast is not unnecessarily brought into contact with the lower temperature materials a plurality of separate tundishes can be provided upstream of the nozzle.
This process makes it possible, and in a simple manner, 10 also for already fitted nozzles at the casting machine to be heated to the desired temperature prior to casting, and so to employ for the nozzle a material which is relatively sensitive to thermal shock with the processes used up to now.
Machines for continuous casting in particular ferrous and nonferrous metals have been developed and namely such that the mound features continuously moving walls. These include machines where the metal to be cast is poured 10 between two moving steel bands or belts, in particular the well known Hazelitt strip casters e.g. according to the US
patent 2,640,235.
Also known are other machines in which the cast product obtains its shape by means of mound halves joined together 15 from a pair of endless belts like caterpillar tracks.
At the pouring end the mound halves face each other and move thus over a specific distance in which they form the actual mound. The mound halves then separate and after a short time return to the pouring or casting end.
20 With, in particular, machines featuring caterpillar track type mounds for casting relatively thin strips e.g. strips only 20 mm thick and less, it is the feeder nozzle for the metal which presents the greatest problems. One of the main reasons for this is that there are few materials 25 which are able to withstand the high temperatures of the metal flowing through it. Graphite for example is one of ~Z2641~3 the few materials able to meet the necessary require-mints. On the other hand graphite has the disadvantage of high thermal conductivity, as a result of which the heat is conducted away from the melt so quickly that the metal has a tendency to solidify in the nozzle.
In any case the parts of the feeder nozzle which come into contact with the molten metal must be made of a refractory material which e.g. when casting aluminum comprises a mixture of 30 % diatomaceous earth (almost pure silica in 10 the form of microscopic cells), 30 % long asbestos fires, 20 % sodium silicate (dry weight) and 20 % chalk (to form calcium silicate.
For casting steel one can use in particular ZrO2 for the nozzle material, or ZrSiO4 containing various amounts of 15 ZrO2; for cost saving purposes the nozzle can also be made of two materials. The ZrO2 used is a stabilized, fine con-amid material with very accurately controlled porosity.
Such a structure is able to accommodate the change in volt use occurring in the Zr2 in such a way that problems of 20 cracking are avoided.
Although the above feeder nozzles made of a refractory ma-tonal feature good thermal barrier properties and low heat capacity, their basic disadvantage is that, because of lack of homogeneity in terms of chemical composition 25 and mechanical properties, the material employed exhibits an up-take of moisture, irreversible changes in chemical composition on heating up to the operating temperature and a related further embrittlement or lower mechanical 1;~264~3 strength and - connected with this - normally permits the nozzle to be used only once. In spite of the above men-toned low thermal capacity and poor thermal conductivity of the known ceramic material when the molten metal is poured for the first time unto the nozzle, the nozzle is exposed to extreme thermal shock with the result that the sudden thermal stress created inside the nozzle can cause it to break apart or at least to crack. A further problem is the so called freezing-up of the nozzle as the metal to 10 be cast comes into contact with the cold inner surface of the nozzle.
In order to avoid such thermal shock or freezing up of the nozzle it has been proposed e.g. in the German patent pub-ligation DE-05 28 16 500 that the whole nozzle should come 15 prose a plurality of hollow sections-lying adjacent to each other held together in a metal holder and made of a material which resists melting and is heat resistant -acting as outlet nozzles, and such that channels for heat-in the device are provided parallel to the channels 20 through which the melt passes. With the aid of such a heating facility it is possible to heat the nozzle up to the necessary melt pouring temperature before casting starts. This can be done so slowly that no thermal shock occurs or thermal stresses are created. On the other hand 25 such a nozzle is complicated in its make up and in par-shackler the heating mechanism has a disturbing influence during normal operation i.e. after the start-up phase is past.
The object of the present invention is therefore to dove-12264~8 lop a much simpler possibility for preheating a nozzle to the desired temperature before the actual start of feeding the metal to be cast.
This object is achieved by way of the invention in that, before the actual metal to be cast is passed through the nozzle, at least one substance at a temperature other than of the said metal is passed through the nozzle.
This extremely simple idea is not only very inexpensive and uncomplicated, but enables conventional nozzles to be 10 used and eliminates the need for additional heating fact-titles.
This substance / these substances should, according to the invention, be at a temperature higher than that of the me-tat to be cast. This process has the advantage that only a 15 small amount of preheating substance is required and also the time of contact between substance and nozzle can be kept short. However, this requires considerable experience with regard to heat transfer between substance and nozzle material.
20 Preference should be given therefore to a substance or substances which is / are at a lower temperature than the metal to be cast. This prevents the nozzle being heated to too high a temperature - which would also cause the metal to be overheated and make additional cooling in the mound 25 necessary.
12264~8 The substance to be passed through the nozzle before the metal which is to be cast is preferably another metal. As a rule an inexpensive metal is suitable for this purpose.
Before introduction into the nozzle this metal can be heated in a special container to the desired temperature, be this above or below that of the metal to be cast.
Preferred, however, is a metal of lower density than the metal to be cast. This way the nozzle and in particular its side walls which limit the width of the strip are not 10 suddenly subjected to excessive pressure at the start of casting. If for example a ferrous metal - in particular steel - is to be cast, then aluminum may be employed as it is less dense than steel and its oxide skin prevents the metal penetrating slits or the like. However, this 15 could lead to contamination of the metal to be cast - in this case steel - or at least the first of the metal to be cast. For this reason it is proposed, in accordance with the invention, when casting a ferrous metal to allow an-other ferrous metal e.g. cast iron (grew cast iron) to be 20 passed through the nozzle before the actual casting be-gins.
It is also within the scope of the invention for a pour-amity of the same ox different substances at different temperatures to be passed first through the nozzle. By way 25 of example the following steps in the process should be mentioned: The nozzle is heated to a temperature of about 200 - 250C with hot air. Then molten aluminum at a them-portray of about 760C is introduced. This is followed by grew cast iron at a temperature of about 1200 C. After 30 this the steel which is to be cast can then be introduced 1;2Z6418 without problem into the nozzle.
To this end, and within the scope of the invention, the tundish upstream of the nozzle features a plurality of clambers for the various substances or metals. In order that the metal which is to be cast is not unnecessarily brought into contact with the lower temperature materials a plurality of separate tundishes can be provided upstream of the nozzle.
This process makes it possible, and in a simple manner, 10 also for already fitted nozzles at the casting machine to be heated to the desired temperature prior to casting, and so to employ for the nozzle a material which is relatively sensitive to thermal shock with the processes used up to now.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Process for preheating a nozzle for feeding molten metal which comprises: providing a nozzle for feeding molten metal, passing through the nozzle prior to feeding said molten metal there through at least one substance at a different temperature from that of the said molten metal to preheat the nozzle, and passing said molten metal through said preheated nozzle.
2. A process according to claim 1 wherein said nozzle feeds said molten metal to a continuous casting machine with moving mold walls.
3. A process according to claim 1 wherein said substance is at a higher temperature than that of said molten metal.
4. A process according to claim 1 wherein said substance is at a lower temperature than that of said molten metal.
5. A process according to claim 1 wherein at least one metal is employed as said substance.
6. A process according to claim 5 wherein the metal which first has to be passed through the nozzle has a lower density than said molten metal.
7. A process according to claim 1 wherein said substance is a ferrous metal.
8. A process according to claim 7 wherein said ferrous metal is grey cast iron.
9. A process according to claim 1 wherein said substance is a non-ferrous metal.
10. A process according to claim 9 wherein said molten metal is steel and said non-ferrous metal is aluminum.
11. A process according to claim 1 wherein said molten metal is a ferrous metal.
12. A process according to claim 11 wherein before said ferrous metal is passed through said nozzle first a non-ferrous metal is passed through the nozzle and subsequently a ferrous metal with a lower melting point than said molten metal is passed through said nozzle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH2966/83 | 1983-05-31 | ||
| CH296683 | 1983-05-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1226418A true CA1226418A (en) | 1987-09-08 |
Family
ID=4245644
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000455273A Expired CA1226418A (en) | 1983-05-31 | 1984-05-28 | Process for preheating a nozzle |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0127578A3 (en) |
| JP (1) | JPS606255A (en) |
| CA (1) | CA1226418A (en) |
| DE (1) | DE3320131A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5291939A (en) * | 1992-11-23 | 1994-03-08 | Reynolds Metals Company | Start-up method and apparatus for continuous casting of metal into strip product |
| IN181634B (en) * | 1993-05-27 | 1998-08-01 | Bhp Steel Jla Pty Ltd Ishikawa |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2640235A (en) * | 1949-06-02 | 1953-06-02 | Clarence W Hazelett | Metal manufacturing apparatus |
| US3405757A (en) * | 1967-04-12 | 1968-10-15 | Harvey Aluminum Inc | Method and apparatus for continuous casting of metal between oppositely rotatable cooling rolls set generally one above the other |
| US4054171A (en) * | 1977-01-13 | 1977-10-18 | Southwire Company | Method and apparatus for starting the continuous casting of a metal |
| JPS58122157A (en) * | 1982-01-12 | 1983-07-20 | Nippon Steel Corp | Production of thin strip of amorphous metal |
-
1983
- 1983-06-03 DE DE19833320131 patent/DE3320131A1/en active Granted
-
1984
- 1984-05-17 EP EP84810242A patent/EP0127578A3/en not_active Withdrawn
- 1984-05-28 CA CA000455273A patent/CA1226418A/en not_active Expired
- 1984-05-31 JP JP11218084A patent/JPS606255A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE3320131C2 (en) | 1988-04-28 |
| JPS606255A (en) | 1985-01-12 |
| EP0127578A3 (en) | 1987-04-15 |
| DE3320131A1 (en) | 1984-12-06 |
| EP0127578A2 (en) | 1984-12-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |