JPH04339548A - Strip caster - Google Patents

Abstract

PURPOSE:To allow the operation to produce sheets free from surface flaws and cracks stably over a long period of time by installing ceramic pieces on the surfaces of a dynamic water cooling bodies in strip casting of a molten metal. CONSTITUTION:The ceramic pieces to be installed on the surfaces of the dynamic water cooling bodies are ceramics having 4X10-61/ deg.C coefft. of thermal expansion. The h-BN component content in the case of the ceramic pieces contg. h-BN is 50 to 97wt.% and a compd. consisting of elements Si, Al, O, N, B, C, Ca, and Zr as the components exclusive of the h-BN is used to constitute the direct rolling which is excellent in the peelability from solidified shells and the slow cooling of the solidified shells and prevents the thermal deformation of the cooling bodies by heating. The excellent sheets free from the surface flaws and defects are easily and continuously produced at a high yield simply by providing the ceramics in the existing strip caster.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip caster for directly manufacturing a thin plate from molten metal that is free from surface scratches such as wrinkles and oscillation marks.

0002

2. Description of the Related Art Continuous casting machines are broadly classified into vertical and horizontal types depending on the direction in which the slab is drawn. The shape of the slab is determined by the shape of the mold into which the molten metal is poured. In the case of a vertical continuous casting machine, the mold vibrates up and down, and in the case of a horizontal type, the mold does not vibrate. Generally, a mold is used to create a shape, and in the case of continuous casting, it is made of water-cooled copper. The drawn slab is hot or cold rolled in a post-process, and processed into a thin plate shape, for example.

[0003] Strip casting (direct rolling) is a process in which a thin plate is manufactured directly from a heated melt without using a fixed mold or a hot or cold rolling mill as described above. The heated molten material is injected into a dynamic water-cooled body, and depending on the shape, type, number, etc. of this dynamic water-cooled body, direct rolling can be performed using the single-roll method, twin-roll method, internal ring method, roll-belt method, or twin-belt method. , vibration molding method. In either method, the heated molten material is poured into a dynamic water-cooled body such as a water-cooled metal rotating roll or belt, and solidification begins on the surface of the water-cooled body. The dynamic water cooling body is always rotating continuously, so that the solidified shell is withdrawn synchronously according to this rotational speed. The amount of melt that has been drawn out is automatically poured in to form a solidified shell again. This repetition is performed continuously, resulting in the formation of a continuous solidified shell. The width of the dynamic water cooling body gives the width of the product board, and the distance between the dynamic water cooling bodies gives its thickness.

[0004] Since the dynamic water cooling body and the solidified shell are synchronously displaced, that is, the relative speed between them is zero, there is no friction due to sliding, and therefore the solidified shell is less likely to be torn off. It can also be manufactured in the form of a thin plate. However, since dynamic water cooling bodies use metals such as copper and stainless steel, they may seize with the solidified shell immediately after injection or undergo rapid cooling, causing the solidified shell to solidify and shrink, and the shells to fuse together. As a result, water wrinkles and scratches appear on the surface of the product thin plate. Furthermore, during operation, the temperature of the metal dynamic cooling body increases, and the resulting surface deformation causes the plate thickness to become non-uniform. On the other hand, since fixed metal plates and refractories are used for the members on the short side (thickness side) of the thin plate, the short side of the shell slides and oscillation marks are formed. As a means to avoid this, the short side member is made into a block shape,
A method is used to run this synchronously with the shell, but
The whole thing becomes very complicated. Molten metal may enter and solidify between the drum or belt and the short side member, making it impossible to pull out the shell, and as a result, burrs form at the corners of the thin plate. Such defects on the thin plate surface, short side surfaces, and corners often become cracks during the cooling process, and tend to result in product defects. This technology has been known for a long time and has not yet been put into practical use.

[0005]

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and its purpose is to:

(1) Direct rolling of molten metal is possible, and

(2) To provide a strip caster that can stably produce thin plates without surface scratches.

[0008]

[Means for Solving the Problems] As a result of extensive research into the above-mentioned problems, the present invention has resulted in the following new findings. That is,

(1) When ceramics are installed on the surface of the dynamic cooling body of a strip caster, the heat removal rate of the solidified shell is reduced and the shell is slowly cooled, and the state of fusion between the shells is extremely good, and the surface It is possible to produce a thin plate with good quality, free from hot water wrinkles and accompanying scratches such as cracks. Also,

001
[0] (2) The dynamic cooling body is protected by the installed ceramics, and there is no thermal deformation, and a uniform thin plate without distortion can be manufactured.

(3) When ceramics having a coefficient of thermal expansion of 4×10 −61 /° C. or less is installed, stable direct rolling is possible without cracking or chipping due to thermal shock or thermal stress.

(4) If ceramics containing h-BN are selected as the ceramics to be installed, h-B will be added to the ceramics.
N has inherent heat resistance, corrosion resistance, wettability, thermal shock resistance,
It exhibits self-lubricating properties and enables direct rolling.

(5) By heating the dynamic water cooling body with ceramics installed on the surface, the temperature of the surface is raised, the heat extraction property is reduced, and the fusion property and slow cooling of the solidified shell are improved,
Direct rolling of thin plates with good surface quality is possible.

[0014]

[Operation] Ceramic pieces are integrated by adhering or bonding to the surface of the dynamic cooling body. In the case of adhering, adhesives containing organic or inorganic adhesives as the basic ingredients are used as the adhesive between metal and ceramics. You can choose as appropriate. When using an organic adhesive as a basic component, its heat resistance is low at 400°C or less, so it is necessary to consider the heat insulation properties of the ceramic and either increase the thickness or select a ceramic with low thermal conductivity. be. When an inorganic material is used, there is no problem with heat resistance, but it is necessary to select an adhesive that alleviates the difference in thermal expansion between the ceramic and the metal.

[0015] The metal to which the ceramic is bonded is preferably copper, which has a high cooling ability, when the adhesive is organic, and when it is an inorganic adhesive, it is preferable to use heat conductive materials such as stainless steel, which has a low cooling ability due to slow cooling of the solidified shell. Metals with low properties are preferred. When joining, a general joining method such as brazing is used.

Since thermal shock and thermal stress occur in ceramics, it is preferable to reduce their thermal expansion. If the coefficient of thermal expansion is 4×10 −61 /° C. or less, separating the ceramic pieces into small pieces and adhering or joining them to metal can prevent the ceramic pieces from peeling off due to thermal shock or thermal stress. When the coefficient of thermal expansion of ceramics is larger than 4.0 × 10-61/℃, the size of ceramics when used,
Even if the thickness and shape are changed, the above problems cannot be avoided.

The reason why a ceramic containing h-BN is used as the ceramic is to exhibit the original characteristics of h-BN, such as thermal shock resistance, corrosion resistance, difficult wettability, and lubricity. Moreover, its preferable amount is 50 to 95% by weight. When the amount of h-BN is less than 50% by weight, the original properties of h-BN, especially thermal shock resistance and wetting properties, are no longer exhibited. Moreover, when the amount of h-BN exceeds 95% by weight, wear due to the solidified shell becomes severe. The reason why compounds consisting of Si, Al, O, N, C, B, Ca, and Zr are selected as components other than h-BN is that properties such as corrosion resistance are further improved. Si, Al, O, N, C, B, C in the sintered body
As a starting material for a compound consisting of a, Zr, SiO2
, Si3 N4 , SiC, Al2 O3 , AlN,
B4C, ZrO2, ZrB2, CaO-B2O
3 Compound, CaO-SiO2 Compound, CaO-B2
O3-Al2O3 compounds, CaB6 can be used. In addition, the starting material for the h-BN component in the sintered body may be used as is, or the h-BN component may be used in the sintering process.
Anything that changes can be used. Sintering at temperature 15
A temperature of 00° C. or higher is sufficient, and all conventional sintering methods can be used. In particular, when sintering is carried out under normal pressure in a reducing nitriding atmosphere, for example, B (boron) may be used and reacted with nitrogen during sintering to form h-BN, or B2 O3
(boric acid) may be reduced and nitrided during the sintering process to form h-BN. Furthermore, amorphous BN is also preferred as a starting material. The amorphous BN mentioned here is Cu
X-ray diffraction of hexagonal h-BN using Kα rays (
It is preferable that the half width of the peak corresponding to 002) exceeds 0.3°. Of course, any combination of these may also be used. Si3 N4 as a component other than h-BN in the sintered body
, SiO2, SiC, AlN, Al2O3, A
l6 Si2 O13, Si2 Al3 O7 N, S
i3 Al2.67O4 N4, Si3 Al3 O
3 N5 , Al3 O3 N, Si6 Al0 O2
1N4, B4C, ZrB2, ZrO2, CaO
The reason why the -B2 O3 type compound and the CaO--SiO2 compound are included is that a sintered body can be obtained without impairing the inherent properties of h-BN, especially thermal shock resistance, corrosion resistance, and wettability. For example, 3Al2 O3 2SiO2 (Al
6 Si2 O13) is included in the sintered body, thermal shock resistance is exhibited, and AlN, Si3 Al3 O3
If N is included, the thermal shock resistance will be poor and the heat resistance will be good. Further, if ZrO2 is included, the thermal conductivity will be poor, and if AlN is included, the thermal conductivity will be good. By changing components other than h-BN in this way, it is possible to change the characteristics of ceramics containing h-BN. Direct rolling is possible with the ceramics attached or bonded to the metal surface placed in the right place.

[0018] When heating the surface of the dynamic cooling body in order to raise the surface temperature and further increase the temperature or slowly cool the solidified shell, any existing equipment can be used as a heating source. When ceramics are placed on the surface of the dynamic cooling body, oxidation due to heating is extremely reduced, and due to its heat resistance, there is little deformation. In the case of only a conventional metallic dynamic cooling body, the metal surface becomes rough or deformed due to heating and oxidation, which is undesirable.

[0019]

[Example] As an example, the results of an actual machine operation of direct rolling of a thin plate using a single roll method will be explained.

As shown in FIG. 1, two types of ceramics 1 and 2 divided into small pieces are adhered to the surface of a water-cooled copper drum. The thickness of the ceramic 1 is 5 mm, and the adhesive is an inorganic adhesive. The thickness of ceramics 2 is 10m
m, exhibits slow cooling and heat insulation effects, increasing the temperature of the shell and lowering the temperature of the adhesive layer. Therefore, the adhesive is an organic adhesive. A ceramic 3 is attached to a portion facing the rotating drum (2) and in contact with the solidified shell, and a ceramic 4 is adhered to a portion in contact with the solidified shell and the molten body using an inorganic adhesive. Here, the ceramic 3 has the same hardness as the ceramic 1 and is made of the same material so as to prevent sliding wear. Further, the ceramic 4 which is in contact with at least the solidified shell is made of the same material as the ceramic 2 and has particularly good peelability from the solidified shell. The molten metal poured into the tundish 5 is cooled, and a solidified shell is formed so as to contact the surface of the ceramic 2 and the ceramic 4 in the thickness direction. The solidified shell produced is drawn out in the direction of rotation 7 of the water-cooled copper drum. After the drawn shell, the molten metal solidifies again, resulting in the production of a continuous sheet. Table 1 shows the ceramic materials, and Table 2 shows the operating conditions and results. Further, Table 3 shows the results when the surface was heated with a heating device under the same conditions.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Effects of the Invention] The following effects can be achieved by the present invention.

[0025] By installing ceramics on the surface of the dynamic water cooling body,

(1) Direct rolling can be performed stably for a long time.

(2) Directly rolled thin plates have no surface flaws and have a uniform thickness.

(3) Since the ceramic is divided, ceramic pieces with different material properties and thickness can be placed at appropriate locations.

[0029]

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic diagram of direct rolling according to an embodiment of the present invention.

[Explanation of symbols]

1 to 4...Each of the installed ceramics 5...
... Water reservoir 6 ... Water-cooled copper roll 7 ... Rotation direction

Claims (7)

[Claims] [Claim 1] Strip caster (direct rolling mill)
A strip caster in which divided ceramic pieces are integrated on the surface of a dynamic cooling body by pasting or bonding. Claim 2: The ceramic has a coefficient of thermal expansion of 4×
The strip caster according to claim 1, which is made of ceramic having a temperature of 10-61/C or less. 3. The strip caster according to claim 1, wherein the ceramic is a ceramic containing hexagonal boron nitride (h-BN). 4. h of the ceramics containing the h-BN.
- The strip caster according to any one of claims 1 to 3, characterized in that the amount of the BN component is 50 to 97% by weight. 5. h of the ceramics containing the h-BN.
- Component elements other than BN are Si, Al, O, N, C, B,
The strip caster according to claim 1, characterized in that it is made of Ca and Zr. 6. h of the ceramics containing the h-BN.
- Components other than BN are at least Si3 N4, SiO
2, SiC, AlN, Al2O3, Al6Si
2 O13, Si2 Al3 O7 N, Si3 Al
2.67O4N4, Si3Al3O3N5,
Al3 O3 N, Si6 Al10O21N4, B
4C, ZrO2, ZrB2, CaO-B2O3
Compound, CaO-SiO2 Compound, CaO-SiO
The strip caster according to any one of claims 1 to 5, characterized in that it contains a 2-Al2O3 compound. 7. The strip caster according to claim 1, wherein the surface of the dynamic cooling body of the strip caster is heated.