JPH02251343A - Continuous casting machine for strip - Google Patents

Abstract

PURPOSE:To keep a side dam to good shape by constituting side dam parts ground with toll pair of heat insulating refractory having good machinability and a part in contact with cast strip of high strength refractory having poor machinability. CONSTITUTION:In order to form pouring basin 2 on circular surfaces in one pair of inner cooling rolls 1a, 1b, one pair of the side dams 3a, 3b are arranged. At least the circumferential surface parts in contact with a pair of the side dams 3a, 3b in the circular surfaces of the rolls are formed with rough surface 10 having good grindability. Then, the parts in the side dams 3a, 3b where the dams are grindingly weared with the circular rough surfaces 10 of the roll pair are constituted of the heat insulating refractory having good machinability. Further, the parts in the side dams 3a, 3b in contact with edge of the cast strip 4 are constituted of the high strength refractory having poor machinability. By this method, leakage of the molten metal caused by breakage of the side dam can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a continuous thin plate casting machine for continuously casting thin plates directly from molten metal, and more specifically, to a continuous thin plate casting machine for continuously casting thin plates directly from molten metal. It's about improvement.

[Conventional technology]

Conventionally, a pair of internal cooling rolls that rotate in opposite directions are arranged in parallel with a suitable gap between them, a pool is formed at the upper part between the rolls, and the thin plate is continuously cooled by rotating the rolls and cooling them on the roll surface. A twin-roll continuous casting machine is known. In this case, in order to form a pool on the circumferential surface of the roll, side dams are required to prevent the molten metal from flowing to both sides of the roll. Generally, side dams are constructed using refractory materials.

Japanese Patent Laid-Open No. 63-252646 discloses a thin plate continuous casting machine, which can be called a semi-mobile type or a grinding-mobile type, of a side dam, which performs casting while feeding the side dam at a predetermined speed in the casting direction while grinding the side dam on the circumferential surface of the roll. Disclose the invention. This method allows stable casting. in this case,
The ribs on both sides of the roll circumferential surface that are in contact with the side dam are machined into a rough surface with grinding ability, and a part of the thickness of the side dam is made to overhang this rough surface so that it is in contact with it, and with this overhang, the side dam is moved in the casting direction. A sending method is particularly preferred. In this grinding movement method, the side dam refractory should be made of a material that has good grindability (and excellent heat insulation properties).This is because high-strength refractories have poor machinability and generally have poor heat insulation resistance. If the insulation is poor, the side dam will cool down at the part where it contacts the cooling roll, and the side shell will develop abnormally in this part, causing trouble when the side shell peels off and falls.For example, the gap between the rolls will widen when it falls. , a gap may appear between the side dam refractory and the roll, and molten metal may enter and solidify in this gap, which may cause damage to the tip of the side dam, and peeling and falling of the side shell may impair the quality of the thin plate being cast. It also becomes.

[Problem that the invention seeks to solve]

Therefore, in the side dam grinding and moving method described in JP-A-63-252646, a side dam with good machinability and good heat insulation is used.

In this case, the following problems arise.

(1) In a twin-roll continuous sheet casting machine, the side dam shape becomes tapered at the tip as it approaches the narrowest gap between the rolls. Therefore, when centering the side dam in preparation for casting, the tip is susceptible to damage due to vibrations such as roll rotation.

(2) When the molten metal level changes, the position where both solidified shells formed on each circumferential surface of the roll pair come together (solidification completion position) changes, and this causes the plate to be rolled at the narrowest gap. The width spread position also changes.

20. The tip of the side dam is likely to be damaged due to fluctuations in the amount of extrusion at the end of the plate. If this damage becomes severe, the molten metal will leak.

(3) In order to prevent the inner surface of the side dam from cooling and developing a side shell in this area, it is desirable to control the flow of molten metal in the pool and collect the molten metal flow near the side dam, but it is not possible to If a large molten metal flow is formed, the inner surface of the side dam will be eroded and the side dam will be destroyed.

(4) During casting, the shape of the refractory tip of the side dam changes due to slight fluctuations in the roll gap due to fluctuations in the molten metal level, defective shell insertion, etc., and it takes t8 before this shape change returns to the normal position. Ik is the difference.

This causes damage to the tip.

The present invention aims to solve the above-mentioned problems in the side dam grinding and movement method disclosed in Japanese Patent Application Laid-open No. 63-252646.

[Means for solving the problem] A pair of internal cooling rolls that rotate in opposite directions are mounted on the shaft.
A pair of side dams are arranged on both sides of the roll pair to form a pool on the circumferential surface of the roll pair, and a delivery mechanism is provided to send out the side dams in the casting direction. Provision 5. In a thin plate continuous casting machine, in which at least a part of the roll circumferential surface that contacts the side dam among the roll circumferential surfaces is formed into a rough surface having a grinding ability, and the side dam sent out by the delivery mechanism is cast while being ground and consumed by the rough surface. 1. According to the present invention, the side dam portion which will be worn out by grinding by the circumferential surface of the pair of rolls is made of a heat-insulating refractory material with good machinability, and
The above-mentioned problem is solved by using a side dam made of a high-strength refractory with poor machinability for the side dam portion that comes into contact with the end of the thin plate to be cast.

In a twin-roll continuous casting machine with a side dam grinding movement method, the side dam part that comes into contact with the edge of the thin plate to be cast is
Generally, it appears in the center of the side dam as a straight line along the delivery direction. Therefore, in the side dam according to the present invention, a linear high-strength refractory layer is located in the center along the feeding direction of the feeding mechanism, and a heat-insulating refractory with good machinability is sandwiched between the high-strength refractory layer in the center. It consists of a plate-like body with objects located on both sides. In this case, a high-strength refractory layer in the center and machinable refractory layers on both sides are integrally formed.

Examples of the drawings will be described below.

〔Example〕

In FIG. 1, reference numerals 1a and lb refer to a pair of internal cooling rolls that are arranged facing each other with their axes horizontal so as to rotate in opposite directions (the direction of rotation of both is indicated by arrows);
2 indicates the molten metal in a pool formed on the circumferential surface 1 of the rolls la and lb; 3a and 3b indicate side dams; and 4 indicates a thin plate to be cast.

Roll pair 1a, lb is an internal cooling roll. In the illustrated examples, water-cooled rolls are used. More specifically, each pair of rolls 1a, lb has a groove-shaped cooling water passage formed inside the roll sleeve forming the circumferential surface R thereof (as shown in the figure). The circumferential surface R is cooled to a predetermined temperature by passing water through this cooling water passage. Supply of cooling water to the cooling water passage inside this circumferential surface R and drainage thereof are performed from a roll shaft having a double pipe structure. P indicates a pump for this water supply.

The side dams 3a, 3b are held by metal side dam cases 5a, 5b attached to their outer surfaces, and by moving the side dam cases 5a, 5b in the casting direction, the side dams 3a, 3b are also moved in the casting direction. In the illustrated example, the refractory side dams 3a, 3
Metal side dam cases 5a and 5b are placed on the outer surface of b.
Install the side dam 3 so as to completely cover the outer surface of the side dam 3.
a, 3b are being held. At that time.

As shown in Figure 2, the thickness of the side dam.

For one part of the inner thickness, the bottom surface 6.6", which is curved to correspond to the circumferential surface R of the rolls la and lb, is positioned above the circumferential surface R of the rolls la and lb, and the thickness is -2 inner surface 7,7'' is roll la, lb
Each side dam 3a, 3
b is set, the side dam cases 5a and 5b are supported on the threaded support 8 via a nut 9 fixed to the case side, and the side dam case 5a is rotated around the axis. , 5b in the casting direction. This allows the side dam 3 to be
The bottom surfaces 6.6" of the side dams 3a and 3b are ground by the rotating roll circumferential surface R and descend while being worn out. In order to perform this grinding well, the bottom surfaces 6, 6 of the side dams 3a and 3b are
The circumferential surfaces of the rolls la and lb that come into contact with the rollers 1 and 1 are formed to have a rough surface 10.

If the roughness and hardness of this rough surface 10 are appropriate depending on the material and casting conditions of the side dam, the bottom surface 6 of the side dam,
6゛ is well ground during casting. The rough surface 10 is preferably formed by plating the base material surface of the roll circumferential surface with a hard metal, or by a thermally sprayed layer of hard metal, ceramics, or cermet. Note 11
1 shows a brush for cleaning the rough surface 10, and if this brush 11 is set so as to come into contact with the rough surface 10, the grinding powder adhering to the part 10 will be removed by the rotation of the rolls la and lb. This makes it possible to prevent a decrease in grinding performance due to clogging of the rough surface. In addition to mechanically interlocking the side dam cases 5a, 5b and the side dams 3a, 3b, the side dam cases 5a, 5b may be bonded using a bonding agent at the bonding interface between the two, and the side dam cases 5a, 5b may be moved downward. As for the mechanism, it is preferable to use a method in which the device is lowered continuously while the device is in operation, but depending on the situation, an intermittent movement method in which the device repeatedly lowers and stops, or a method in which the device is lowered while slightly vibrating may also be used.

In any case, it is preferable to control the lowering speed using the lowering amount of the side dam or the width of the plate to be cast as a detection signal.

In the twin roll continuous casting machine using such a grinding movement method of the side dams 3a, 3b, in the present invention, when configuring the side dams 3a, 3b, the refractory of the part to be ground by the roll circumferential surface R, and the roll On the circumferential surface R, the material is separated from the refractory material in a portion that is not substantially ground or has a small amount of grinding allowance even if it is ground.

That is, as shown in FIG. 2, the side dam portion, which will be worn out by grinding by the circumferential surface of the pair of rolls, is made of heat-insulating refractories A, , A with good machinability.

(A I and A t are the same material), and the side dam portion that comes into contact with the end of the thin plate 4 to be cast is made of a high-strength refractory B with poor machinability. In the continuous casting machine shown in Fig. 1, twin rolls of the same diameter are used, rolls la and Ib are arranged so that the narrowest gap is located in the center, and side dams 3a and 3b are cast in the casting direction of the thin plate 4. Roll 1a, lb
The parts that will be worn out by grinding will appear symmetrically around the part that will come into contact with the edge of the thin plate 4. That is, a linear high-strength refractory layer B is located at the center along the feeding direction by the feeding mechanism, and the heat-insulating refractory A + with good machinability is sandwiched between this central high-strength refractory layer B. AZ will be located symmetrically on both sides. Although FIG. 2 shows one side dam, the other side dam also has the same configuration.

As shown in FIG. 4, the width C of the narrowest gap between the rolls la and lh corresponds to the thickness of the thin plate to be cast. When the side dam is pushed out in the casting direction by the feeding mechanism, the end of the thin plate to be cast comes into contact with the side dam portion corresponding to the narrowest gap.

Since the thickness of the thin plate approximately corresponds to the width C of the narrowest gap, the width b+ (Fig. 3) of the linear high-strength refractory layer B is 8 approximately equivalent to the width C of the narrowest gap. Bye.

In reality, the linear high-strength refractory layer B occupies only a small part of the plate-shaped side dam, and the width b1 approximately corresponds to the width C of the narrowest gap on the side of the side dam that contacts the molten metal. However, this high-strength refractory layer B
In order to integrally and firmly join the heat-insulating refractories A + and A z with good machinability, the linear high-strength refractory layer B has a convex cross section as shown in Fig. 3. It is better to take it as a thing. In other words, the inner surface of the side dam that will be in contact with the molten metal in the pool should have a narrow width of bl, and the outer surface should have a wide width of b2, and the narrow width b+ should have a thickness equivalent to the thickness of the side dam, or The width b2 shall be within the thickness w2 of the side dam. By having such a convex cross-sectional shape, the refractory A
It is possible to create a bonded structure that provides resistance to vibration and stress while increasing the bonding area between B and B.

As the high-strength refractory layer B, boron nitride (BN) and graphite are suitable, and as the machinable refractory material A, Ai,
z O3 fiberboard is preferred. In addition, the high-strength refractory layer B is made of high-density A Rz O3 fiberboard,
The machinable refractory layer A can also be a low density Al z O3 fiberboard. In any case, although the high-strength refractory layer B has inferior machinability compared to layer A, it has high strength and also has inferior heat insulation properties, but it is sufficient to suppress the overhang of the edge of the plate being cast. The molten metal in the pool is prevented from cooling and solidifying in this area even if the heat insulation performance is slightly inferior due to its narrow width. This was demonstrated by the following operational example conducted by the present inventors.

Internal cooling roll la with a diameter of 850mm and a width of 600mm
, lb with a gap of 2.00 to 3.00 mm at its narrowest part
Set it with

While the feeding mechanism makes the side dams 3a and 3b feed at a speed of 2 to 10 mm/win, the feeding speed is 20 to 30 mm/win.
Plate J ¥2.00 from i8111jl at win casting speed
A thin plate with a thickness of ~3.00 mm and a plate width of 530 mm was manufactured. Side dams 3a and 3b are + L = 35mm 11g = 25m
m+ Width of high-strength refractory layer B = 2.00 to 3.0
0am, same tlz=60m-. At that time, as the above-mentioned refractories A and B constituting the side dam, (1
) B is boron nitride (BN: density 1.0 to 1.7 g/c
m'', bending strength 3.2 kgf/gu-f), A is Al
x Ox fiberboard (density 0.35/cm”,
Bending strength: 0.05 kgf/ms'') (7)% molded product, and (2) B is a fired AlzOs fiberboard product (density 0.5 to 0.6 g/cm3), A is Affi, 0. Fiberboard (density 0.3g/c
An integrally molded product of w') was used.

As a result, no problem caused by the defective shell occurred when using either side dam (1) or (2). Although a slight amount of solidification was observed in portion B, the width was within the range of the gap width of the narrowest part of the roll, and it did not spread beyond that and did not pose a problem. In addition, spalling due to the difference in thermal expansion coefficients between A and B, which was a concern, did not become a problem as the low-density products located on both sides were effective in absorbing the thermal expansion of the high-density products. Furthermore, both ends of the cast plate are completely ITD cast (approximately 1 ton).
It is possible to cut a thin plate of approximately 21111 x 530mm for 100m.
I was able to manufacture more than that.

As described above, 1. According to the present invention, the weakest part, which is the tip of the side dam, can be covered with a high-strength product. 1. Even when affected by vibrations such as roll rotation, the tip does not break and stable casting is possible. Even if the molten steel level fluctuates somewhat, the solidification completion position fluctuates, and the width widening position of the cast plate fluctuates, the proportion of sand dam refractories being scraped away is reduced. In addition, in order to prevent the development of sand shells that occur on the inner surface of the side dam, even if the molten steel flow is collected near the side dam, erosion of the side dam will be reduced and a good side dam shape can be maintained, and the roll gap will change slightly during casting. Even if the tip of the side dam has an abnormal shape (it can maintain a stable shape), the object of the present invention stated at the beginning can be effectively achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing essential parts of an embodiment of the apparatus according to the present invention, FIG. 2 is a perspective view showing an example of the shape of the refractory of the side dam in the apparatus shown in FIG. 1, and FIG. FIG. 4 is a cross-sectional view taken along line mm' of the side dam, and a schematic side view for explaining the positional relationship between the roll pair and the side dam. la, lb... pair of internal cooling rolls, 2... hot water pool. 3a, 3b...side dam, 4...cast plate. 6.6゛... The bottom surface of the side dam, which is curved to correspond to the circumference of the roll. 7.7°... The part of the side dam that comes into sliding contact with the side surface of the roll. 10... Rough surface portion of the roll circumferential surface that comes into sliding contact with the bottom surface of the side dam. A1. A2: Heat-insulating refractory with good machinability B: High-strength refractory C: Width of the narrowest gap 5 bl: Width of the inner surface of the side dam of the high-strength refractory -1: Roll circumferential surface Thickness of the side dam in contact with 6: Thickness of the side dam located outside the roll circumferential surface. Figure 1

Claims (6)

[Claims] (1) A pair of internal cooling rolls that rotate in opposite directions are arranged facing each other with their axes parallel to each other, and a pair of side dams are installed on the sides of the roll pair to form a pool on the circumferential surface of the roll pair. The side dam is arranged and provided with a delivery mechanism for sending out the side dam in the casting direction, and at least a part of the roll circumferential surface that contacts the side dam among the roll circumferential surfaces is formed into a rough surface having grinding ability, and the side dam is sent out by the delivery mechanism. In a thin plate continuous casting machine that casts thin plate while grinding and wasting it by the rough surface, the side dam part which is being ground and wasted by the circumferential surface of the pair of rolls is made of an insulating refractory with good machinability, and is cast. A thin plate continuous casting machine characterized in that the side dam portion of the side dam that comes into contact with the end of the thin plate is made of a high-strength refractory material with poor machinability. (2) The side dam has a linear high-strength refractory layer located in the center along the feeding direction by the feeding mechanism,
This central high-strength refractory layer is sandwiched between plate-shaped bodies with heat-insulating refractories with good machinability located on both sides. The thin plate continuous casting machine according to claim 1, which is integrally formed. (3) The thin plate continuous caster according to claim 2, wherein the central high-strength refractory layer is made of boron nitride (BN), and the machinable refractory layers on both sides thereof are made of Al_2O_3 fiberboard. (4) Central high-strength refractory layer is high-density Al_2O_3
The thin plate continuous casting machine according to claim 2, wherein the fiberboard and the machinable refractory layers on both sides thereof are made of low-density Al_2O_3 fiberboard. (5) The thin plate continuous casting machine according to claim 2, wherein the central high-strength refractory layer is made of graphite, and the machinable refractory layers on both sides thereof are made of Al_2O_3 fiberboard. (6) The thin plate continuous caster according to claim 1 or 2, wherein the high-strength refractory has a width approximately equivalent to the gap width of the narrowest gap between the roll pairs.