CA1062877A - Process for coating moulds, in particular strip moulds for continuous casting machines - Google Patents
Process for coating moulds, in particular strip moulds for continuous casting machinesInfo
- Publication number
- CA1062877A CA1062877A CA222,499A CA222499A CA1062877A CA 1062877 A CA1062877 A CA 1062877A CA 222499 A CA222499 A CA 222499A CA 1062877 A CA1062877 A CA 1062877A
- Authority
- CA
- Canada
- Prior art keywords
- coating
- accordance
- moulds
- deposited
- strip
- 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
- B22D11/0605—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two belts, e.g. Hazelett-process
Abstract
ABSTRACT
A process for coating moulds, in particular endless strip moulds for continuous casting machines for the casting of metals in particular aluminum or zinc or alloys of these, A ceramic material, which is heat resistant at the coating temperature of the metal, is deposited on the mould using a thermal spraying process. The deposited ceramic material can be machined subsequent to being deposited
A process for coating moulds, in particular endless strip moulds for continuous casting machines for the casting of metals in particular aluminum or zinc or alloys of these, A ceramic material, which is heat resistant at the coating temperature of the metal, is deposited on the mould using a thermal spraying process. The deposited ceramic material can be machined subsequent to being deposited
Description
106Z51'77 The invention concerns a coating, in particular a coating for strip moulds for continuous casting machines.
In the accompanying drawings:-Figure 1 is a side view of a continuous casting machine;
Figure 2 is an enlarged section of the coated steel strip ofFigure l;
Figure 3 is a side view of a device for coating the strip.
In continuous casting processes such as, for example, in the well known Hazelett machines as shown in Figures 1 and 2, liquid metals 1 e.g.
aluminum, zinc, copper, steel and alloys of these metals are cast between two endless strips 2. m ese strips 2, which are used as the mould, are usually made of steel.
m e strips 2 are power driven over deflection and support rolls 3 and together form a gap 4. The backs of the strips are cooled with water 5.
m e melt is introduced from a suitable feeder device 6 between the two moving endlass strips 2. The melt solidifies there to form a strip 7 which passes from the machine at the other end. The cooling and solidifica-tion of the melt can be controlled by a layer 8 on the strips which are used as the mould. Through this control of the cooling, the surface finish and the structure of the cast strip can be significantly influenced.
m e layer which must be applied to the endless strips of such a casting machine has a number of requirements to meet in order to be suitable for the production of high grade continuously cast strips as e.g. demanded in the aluminum industry. These requirements are presented here for the case of casting aluminum whereby not only pure aluminum but also its alloys are to be understood here by the term aluminum.
1. m e coating must exhibit very good resistance to high tempera-tures, since it comes in contact with liquid aluminum.
In the accompanying drawings:-Figure 1 is a side view of a continuous casting machine;
Figure 2 is an enlarged section of the coated steel strip ofFigure l;
Figure 3 is a side view of a device for coating the strip.
In continuous casting processes such as, for example, in the well known Hazelett machines as shown in Figures 1 and 2, liquid metals 1 e.g.
aluminum, zinc, copper, steel and alloys of these metals are cast between two endless strips 2. m ese strips 2, which are used as the mould, are usually made of steel.
m e strips 2 are power driven over deflection and support rolls 3 and together form a gap 4. The backs of the strips are cooled with water 5.
m e melt is introduced from a suitable feeder device 6 between the two moving endlass strips 2. The melt solidifies there to form a strip 7 which passes from the machine at the other end. The cooling and solidifica-tion of the melt can be controlled by a layer 8 on the strips which are used as the mould. Through this control of the cooling, the surface finish and the structure of the cast strip can be significantly influenced.
m e layer which must be applied to the endless strips of such a casting machine has a number of requirements to meet in order to be suitable for the production of high grade continuously cast strips as e.g. demanded in the aluminum industry. These requirements are presented here for the case of casting aluminum whereby not only pure aluminum but also its alloys are to be understood here by the term aluminum.
1. m e coating must exhibit very good resistance to high tempera-tures, since it comes in contact with liquid aluminum.
2. The coating must be insulating in order that the melt solidifies 3Q uniformly and in a controlled manner to form a strip without any irregular separation of the solidified crust from the endless strip mould. Furthermore the endless strips must not get too hot due to direct contact with the melt f~
~ q~
106;287~
as this would lead to their warping and the removal of h~at being interrupted.
Any warping of the endless strips leads therefore to the production of unuse-able cast strips. The thermal insulation provided by the coating prevents -la-this overheating of the steel strip. Experience has shown that the heat resistance of the coating must be in the region of 10-4 to 10-3 m.3h. C/kcal in order to achieve good results.
~ q~
106;287~
as this would lead to their warping and the removal of h~at being interrupted.
Any warping of the endless strips leads therefore to the production of unuse-able cast strips. The thermal insulation provided by the coating prevents -la-this overheating of the steel strip. Experience has shown that the heat resistance of the coating must be in the region of 10-4 to 10-3 m.3h. C/kcal in order to achieve good results.
3. There must be no tendency for adhesion between the coating and the melt or the solidified metal i.e. the wettability of the coating by liquid aluminum and the tendency for the solidified metal to stick to the coating must be exceptionally small. If this is not the case then the result is that particles of the coating stick to the cast strip. Under no circumstances could this be tolerated in the production of a high grade quality product.
Furthermore too strong an adhesion between the cast metal and the coating can lead to the coating being torn away from the steel substrate.
Furthermore too strong an adhesion between the cast metal and the coating can lead to the coating being torn away from the steel substrate.
4. The coating must be resistant to temperature changes since on coming into contact with the liquid metal it is raised very quickly to a high tempera-ture and when the solidified strip separates from the coated steel strip the coating is then very rapidly cooled to a iow temperature by cooling water.
5. The coating must also exhibit a certain flexibility which allows the coated steel strip to be led over deflection rolls.
6. The coating must be very adherent to the steel strip onto which it is deposited. Normally to improve this adhesion the surface of the steel strips is roughened.
7. No particles should be transferred from the coating to the cast strip since this would markedly reduce the quality of the cast strip.
8. Th0 roughness on the coating surface must be so slight that the cast strip also obtains a smooth surface which causes no problems on further processing.
9. The coating must be deposited in uniform thickness in order that the heat transfer is the same at all places in the strip. If this is not so then serious flaws appear in the cast strip.
10. The lifetime of the coating must amounc to several hours, prefera-bly longer than a working shift i.e. 8 hours.
There are already a number of known coatings which fulfil several ~06Z877 of these requirements. However, none of the known coatings fulfill all of the necessary requirements at the same time. Thus for example a finely divided graphite, treated with an organic binding agent, i5 worn away relatively quickly by the cast strip. Other coatings consist of resins mixed with various fillers. These resins however are not sufficiently temperature resistant. These layers break up and upset production. In general they must be protected from direct contact with the liquid aluminum by a colloidal separating layer.
The invention provides a process for coating endless strip moulds for continuous casting machines for the casting of metals in particular aluminum or zinc or alloys of these, in which a ceramic material, which is heat resistant at the casting temperature of the metal, is deposited on the mould using a thermal spraying process, preferably by plasma spraying.
The layer can have a preferred thickness of 100 - 600 ~m since the plasma spraying produces a porosity in the layer which gives the layer a sufficiently high degree of flexibility that it can be deflected round rolls and at the same time have good adhesion to the steel substrate.
The ceramic layer, for example consisting of A12O3, CaZrO3, A12O3.MgO, ZrSiO4 or A1203.TiO2 is, in accordance with the invention, deposited in several thin layers (80-100 ~m, preferably 50-70 ~m) on the end-less casting strips until the desired thickness which gives the requisite resistance in the region of lO 4 to 10 3 m2.h.C/kcal, is achieved. The basic advantages of the ceramic layers of the invention are the high temperature resistance and the freedom from wear which make possible the production of high grade casting strips without coating particles and also the markedly improved lifetimes compared to those of the known coatings and thus the more effective protection of the expensive steel strip moulds. With the preferred ceramic coating, deposited by plasma spraying, casting can be carried out for many days without interruption.
3Q The surface of the thermally sprayed coating can, usefully, be machined mechanically e.g. by grinding, in order to achieve uniform strip roughness and wetting behaviour between the layer and the aluminum being 106;2877 cast. As a result of this machining the quality of the aluminum is for special purposes markedly improved since the surface roughness and thus the solidi-fication conditions are altered.
An example of the invention is explained in greater detail with the aid of Figures 1 and 2. Figure 1 shows a side view of a continuous casting machine the endless steel strips 2 of which are provided with the coatings of the invention. Figure 2 shows an enlarged section of this coated steel strip.
Figure 3 shows the side view of a device for coating the strips, and which consists of a drum 9, plasma spraying equipment 10 and an apparatus 11 for roughening the surface of the steel strip e.g. a sand blasting unit. The drum 9 tenses the steel strip and with the strip is made to rotate slowly by an electric motor (e.g. at about 12m/min circumferential speed). On the one side of the ~otating drum there is placed the apparatus 11 which roughens the sur-face of the steel strip and which works in particular with corundum of particle size 200 - 700 ~m, preferably 200 - 400 ~m at a spraying force of 3 - 6, pref-erably 4 - 5 atmospheres. Immediately after the surface is roughened, this part of the steel strip is coated with a ceramic layer ~e.g. CaZrO3) by means of a plas~a gun (e.g. AVKO). The powder used for the ceramic coating should preferably have a particle size of 10 - 100 ~m, preferably 20 - 40 ~m. The plasma spraying equipment coats a strip of about 0.8 cm in width on one rota-tion of the drum. By simultaneous movement of the plasma spraying equipment in a direction perpendicular to the direction of turning of the drum i.e.
parallel to its axis, the whole of the surface of the steel strip is uniformly coated with the ceramic mass, By the applications of several layers the desired coating thickness, and therefore the desired resistance, is reached.
The ceramic layer can then be machined e.g. by grinding, in order to arrive at the desired surface finish. This subsequent machining of the surface influences amongst other things the solidification conditions since the wet-ting of the surface by the liquid metal and the heat transfer change with the roughness of the coating surface.
106;ZS77 The finished, coated steel strip can then be mounted on to the casting machine shown in Figure 1 and used for the continuous production of cast strip.
There are already a number of known coatings which fulfil several ~06Z877 of these requirements. However, none of the known coatings fulfill all of the necessary requirements at the same time. Thus for example a finely divided graphite, treated with an organic binding agent, i5 worn away relatively quickly by the cast strip. Other coatings consist of resins mixed with various fillers. These resins however are not sufficiently temperature resistant. These layers break up and upset production. In general they must be protected from direct contact with the liquid aluminum by a colloidal separating layer.
The invention provides a process for coating endless strip moulds for continuous casting machines for the casting of metals in particular aluminum or zinc or alloys of these, in which a ceramic material, which is heat resistant at the casting temperature of the metal, is deposited on the mould using a thermal spraying process, preferably by plasma spraying.
The layer can have a preferred thickness of 100 - 600 ~m since the plasma spraying produces a porosity in the layer which gives the layer a sufficiently high degree of flexibility that it can be deflected round rolls and at the same time have good adhesion to the steel substrate.
The ceramic layer, for example consisting of A12O3, CaZrO3, A12O3.MgO, ZrSiO4 or A1203.TiO2 is, in accordance with the invention, deposited in several thin layers (80-100 ~m, preferably 50-70 ~m) on the end-less casting strips until the desired thickness which gives the requisite resistance in the region of lO 4 to 10 3 m2.h.C/kcal, is achieved. The basic advantages of the ceramic layers of the invention are the high temperature resistance and the freedom from wear which make possible the production of high grade casting strips without coating particles and also the markedly improved lifetimes compared to those of the known coatings and thus the more effective protection of the expensive steel strip moulds. With the preferred ceramic coating, deposited by plasma spraying, casting can be carried out for many days without interruption.
3Q The surface of the thermally sprayed coating can, usefully, be machined mechanically e.g. by grinding, in order to achieve uniform strip roughness and wetting behaviour between the layer and the aluminum being 106;2877 cast. As a result of this machining the quality of the aluminum is for special purposes markedly improved since the surface roughness and thus the solidi-fication conditions are altered.
An example of the invention is explained in greater detail with the aid of Figures 1 and 2. Figure 1 shows a side view of a continuous casting machine the endless steel strips 2 of which are provided with the coatings of the invention. Figure 2 shows an enlarged section of this coated steel strip.
Figure 3 shows the side view of a device for coating the strips, and which consists of a drum 9, plasma spraying equipment 10 and an apparatus 11 for roughening the surface of the steel strip e.g. a sand blasting unit. The drum 9 tenses the steel strip and with the strip is made to rotate slowly by an electric motor (e.g. at about 12m/min circumferential speed). On the one side of the ~otating drum there is placed the apparatus 11 which roughens the sur-face of the steel strip and which works in particular with corundum of particle size 200 - 700 ~m, preferably 200 - 400 ~m at a spraying force of 3 - 6, pref-erably 4 - 5 atmospheres. Immediately after the surface is roughened, this part of the steel strip is coated with a ceramic layer ~e.g. CaZrO3) by means of a plas~a gun (e.g. AVKO). The powder used for the ceramic coating should preferably have a particle size of 10 - 100 ~m, preferably 20 - 40 ~m. The plasma spraying equipment coats a strip of about 0.8 cm in width on one rota-tion of the drum. By simultaneous movement of the plasma spraying equipment in a direction perpendicular to the direction of turning of the drum i.e.
parallel to its axis, the whole of the surface of the steel strip is uniformly coated with the ceramic mass, By the applications of several layers the desired coating thickness, and therefore the desired resistance, is reached.
The ceramic layer can then be machined e.g. by grinding, in order to arrive at the desired surface finish. This subsequent machining of the surface influences amongst other things the solidification conditions since the wet-ting of the surface by the liquid metal and the heat transfer change with the roughness of the coating surface.
106;ZS77 The finished, coated steel strip can then be mounted on to the casting machine shown in Figure 1 and used for the continuous production of cast strip.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for coating endless strip moulds for continuous casting machines for the casting of metals in particular alum-inum or zinc or alloys of these, in which a ceramic meterial, which is heat resistant at the casting temperature of the metal, is deposited on the mould using a thermal spraying process.
2. A process in accordance with claim 1 in which the deposition is carried out using plasma spray equipment.
3. A process in accordance with claim 1 in which the deposition is carried out using flame spraying equipment.
4. A process in accordance with claim 1 in which the deposition is carried out using an arc-spray gun.
5. A process in accordance with claim 1 in which the ceramic material consists of Al2O3 or CaZrO3, or Al2O3.MgO, or ZrSiO4, or CaZrO3.MgO, or Al2O3.TiO2.
6. A process in accordance with claim 1 in which the application of the coating takes place in several superimposed layers.
7. A process in accordance with claim 5 in which the ceramic material consists of several ceramic materials.
8. A process in accordance with claims 6 or 7 in which the coating is made up of layers of different ceramic materials.
9. A process in accordance with one of the claims 1, 3 or 5 in which the deposited ceramic material is machined subsequent to being deposited.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH388974A CH574285A5 (en) | 1974-03-20 | 1974-03-20 | Refractory coating for continuous casting mould moving bands - comprises layers of refractory covered with resin filled with fine inorg matl |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062877A true CA1062877A (en) | 1979-09-25 |
Family
ID=4265676
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA222,499A Expired CA1062877A (en) | 1974-03-20 | 1975-03-19 | Process for coating moulds, in particular strip moulds for continuous casting machines |
Country Status (3)
| Country | Link |
|---|---|
| BE (1) | BE826897A (en) |
| CA (1) | CA1062877A (en) |
| CH (1) | CH574285A5 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4588021A (en) * | 1983-11-07 | 1986-05-13 | Hazelett Strip-Casting Corporation | Matrix coatings on endless flexible metallic belts for continuous casting machines method of forming such coatings and the coated belts |
| EP0245862B1 (en) * | 1986-05-15 | 1991-09-25 | Union Carbide Corporation | Liquid film coating of iron-based metals |
-
1974
- 1974-03-20 CH CH388974A patent/CH574285A5/en not_active IP Right Cessation
-
1975
- 1975-03-19 CA CA222,499A patent/CA1062877A/en not_active Expired
- 1975-03-20 BE BE154510A patent/BE826897A/en not_active IP Right Cessation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4588021A (en) * | 1983-11-07 | 1986-05-13 | Hazelett Strip-Casting Corporation | Matrix coatings on endless flexible metallic belts for continuous casting machines method of forming such coatings and the coated belts |
| EP0245862B1 (en) * | 1986-05-15 | 1991-09-25 | Union Carbide Corporation | Liquid film coating of iron-based metals |
Also Published As
| Publication number | Publication date |
|---|---|
| CH574285A5 (en) | 1976-04-15 |
| BE826897A (en) | 1975-07-16 |
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