JPH082482B2 - Thin plate continuous casting machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin plate continuous casting machine for continuously casting thin plates directly from a molten metal, and more specifically, to a side dam of a twin roll type thin plate continuous casting machine. It is about improvement.

[Conventional technology]

Conventionally, a pair of internal cooling rolls that rotate in opposite directions are arranged in parallel with an appropriate gap, and a pool is formed in the upper part between the rolls. The rolls are rotated and the thin plates are continuously cooled while cooling on the roll surface. A twin roll type continuous casting machine for casting is known. In this case, in order to form the 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. Side dams are generally constructed using refractory materials.

Japanese Unexamined Patent Publication No. 63-252646 discloses a thin plate continuous casting machine which can be said to be a semi-moving type or a grinding moving type of side dam, in which the side dam is worn away on the circumferential surface of the roll and is fed at a predetermined speed in the casting direction. The invention is disclosed. According to this method, stable casting can be performed. In this case, both sides of the roll circumferential surface that contact the side dam are machined into a rough surface with grinding ability, and the side dam is overhung so that a part of the thickness of the side dam is in contact with this rough surface. A method of feeding in the casting direction is particularly preferable. In this grinding movement method, the side dam refractory material is preferably made of a material having good grindability and excellent heat insulation. This is because high-strength refractories have poor machinability and generally have poor heat resistance. If the heat insulation is poor, the side dam will cool at the part in contact with the chill roll, and the side shell will be likely to develop abnormally at this part, causing problems when the side shell peels off. For example, when the roll is dropped, the gap between the rolls expands, the gap between the side dam refractory and the roll comes out, and the molten metal enters and solidifies into this, and the side dam tip may be damaged due to this. It will also impair the quality of the thin plate.

[Problems to be solved by the invention]

Therefore, in the side dam grinding movement method described in JP-A-63-252646, a side dam having good machinability and good heat insulation is used, but in this case, the following problems occur. Accompany.

(1) In the twin roll type thin plate continuous casting machine, the tip of the side dam shape becomes thinner as it approaches the narrowest gap of the roll. Therefore, when setting the side dam in preparation for casting, the tip is easily damaged by the influence of vibration such as roll rotation.

(2) When the molten metal level fluctuates, the position at which both solidification shells formed on each circumferential surface of the roll pair merge (solidification completion position) also fluctuates, which causes the rolling of the plate rolled in the narrowest gap. The widening position also changes. Due to this variation in the pushing amount of the plate end, the tip of the side dam is easily damaged.
If this damage becomes severe, the molten metal will leak.

(3) It is desirable to control the flow of molten metal in the pool to collect the molten metal flow near the side dam in order to prevent the inner surface of the side dam from cooling and side shells to develop in this area. When a large molten metal flow is formed, the inner surface of the side dam is eroded, causing the side dam to be destroyed.

(4) During casting, the shape of the refractory tip of the side dam changes due to a slight change in the roll gap due to fluctuations in the melt level, defective shell insertion, etc., and the melt is inserted until this shape change returns to the normal position, and this tip Cause damage to the.

The present invention is intended to solve the above-mentioned problems in the side dam grinding and moving system disclosed in JP-A-63-252646.

[Means for solving problems]

A pair of inner cooling rolls rotating in opposite directions are arranged opposite to each other with their axes parallel to each other, and a pair of side dams for forming a basin on the circumferential surface of the roll pair has at least a part of its thickness. Is located on both sides of the roll pair so as to be located on the circumferential surface of the roll pair, and is provided with a feeding mechanism for feeding the side dam in the casting direction. According to the present invention, in a thin plate continuous casting machine in which a surface portion is formed into a rough surface having a grinding ability and a side dam sent by a sending mechanism is worn while being worn away by the rough surface, according to the present invention, grinding is performed by the circumferential surface of a roll pair. The side dam portion to be formed is made of a heat-resistant refractory having good machinability, and the side dam portion to be in contact with the end of the thin plate to be cast is covered. Using the side dam constructed high-strength refractory material inferior sex, by allowing feed the whole of the side dams in the casting direction by the feed-out mechanism, in which attempted to solve the above problems.

In a twin-roll continuous casting machine of the side dam grinding and moving type, the side dam portion that comes into contact with the end of the thin plate to be cast generally appears in the central part of the side dam as a linear shape along the feeding direction. Therefore, in the side dam according to the present invention, the linear high-strength refractory layer is located in the center along the feeding direction of the feeding mechanism, and the high-strength refractory layer at the center is sandwiched between the heat-insulating refractory layers with good machinability. It consists of plate-shaped objects located on both sides. At that time, a high-strength refractory layer in the center and machinable refractory layers on both sides are integrally molded.

 Examples of the drawings will be described below.

〔Example〕

In FIG. 1, reference numerals 1a and 1b are a pair of internal cooling rolls which are arranged so as to face each other so that they rotate in directions opposite to each other (the directions of rotation of both are indicated by arrows), and 2 are the rolls 1a and 1b. Molten metal in the pool formed on the circumferential surface R of
3a and 3b are side dams, and 4 is a thin plate to be cast.

Roll pair 1a, 1b is an internal cooling roll. In each of the illustrated examples, a water-cooled roll is used. More specifically, in each of the roll pairs 1a and 1b, a groove-shaped cooling water passage is formed inside the roll sleeve forming the circumferential surface R (not shown in the figure). ), The circumferential surface R is cooled to a predetermined temperature by passing water through the cooling water passage. The supply of cooling water to the cooling water passage on the inner side of the circumferential surface R and the 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 gripped by metal side dam cases 5a, 5b attached to their outer side surfaces, and the side dam cases 5a, 5b are moved in the casting direction, so that the side dams 3a, 3b are also moved in the casting direction. Sent out. In the illustrated example, metal side dam cases 5a and 5b are attached to the outer surfaces of the refractory side dams 3a and 3b so as to completely cover the outer surfaces and hold the side dams 3a and 3b. At that time, as shown in FIG. 2, of the thickness of the side dam, the bottom surface 6 or 6'which is curved so as to correspond to the circumferential surface R of the rolls 1a and 1b with respect to the inner thickness W ₁ is the roll. The side dams 3a, 3b are arranged so that they are located on the circumferential surface R of the rolls 1a, 1b, and the inner surfaces 7, 7'of the thickness W ₂ are in sliding contact with the side surfaces S of the rolls 1a, 1b. The side dam cases 5a and 5b are set, and the side dam cases 5a and 5b are supported by supporting the threaded support pillar 8 through the nut 9 fixed to the case side and rotating the support pillar 8 around the axis. Is moved in the casting direction. As a result, during operation of the apparatus, the side dams 3a, 3b are lowered while being worn down and worn by the bottom surface 6, 6'of the roll circumferential surface R that rotates. In order to perform this grinding satisfactorily, the circumferential surface portions of the rolls 1a and 1b that come into contact with the bottom surface portions 6 and 6'of the side dams 3a and 3b are formed as rough surfaces 10. When the roughness and hardness of the rough surface 10 are made appropriate according to the material of the side dam and the casting conditions, the bottom surfaces 6, 6'of the side dam are favorably ground during casting. This rough surface 1
In order to form 0, it is preferable that the surface of the base material on the circumferential surface of the roll is plated with a hard metal, or it is composed of a sprayed layer of hard metal, ceramics or cermet. Reference numeral 11 denotes a brush for cleaning the rough surface 10. If the brush 11 is set so as to abut the rough surface 10, the grinding powder adhered to the portion 10 is rotated by the rotation of the rolls 1a and 1b. It can be removed, and it is possible to prevent a decrease in grinding ability due to clogging of the rough surface. The side dam cases 5a and 5b and the side dams 3a and 3b may be mechanically engaged with each other and may be adhered to each other by using a bonding agent at the joint interface between them, and the side dam cases 5a and 5b are moved downward. The mechanism is preferably a system in which it is continuously lowered during operation of the device, but in some cases it may be a intermittent movement system in which it is repeatedly lowered and stopped, or it may be a system in which it is lowered while slightly vibrating. In any case, it is preferable to control the descending speed by using the descending amount of the side dam or the plate width to be cast as a detection signal.

In the twin roll type continuous casting machine based on the grinding and moving method of the side dams 3a and 3b, in the present invention, when the side dams 3a and 3b are configured, a refractory material to be ground on the roll circumferential surface R, On the circumferential surface R of the roll, the material is divided into a refractory material which is substantially not ground or has a small grinding allowance even if it is ground.

That is, as shown in FIG. 2, the side dam portion, which is to be ground and consumed by the circumferential surface of the roll pair, has good machinability as a heat insulating refractory material A ₁ , A ₂ (A ₁ , A ₂ is (Same material)
Then, the side dam portion, which comes into contact with the end of the thin plate 4 to be cast, is made of a high-strength refractory material B having poor machinability. In the continuous casting machine shown in Fig. 1, twin rolls of the same diameter are used, rolls 1a and 1b are arranged so that the narrowest gap is located in the center, and side dams 3a and 3b are cast in the thin plate 4 casting direction. Since the rolls 1a and 1b are used for grinding, the thin plate 4 is the part that is consumed by grinding by the rolls 1a and 1b.
It will appear in contrast, centering on the part that touches the edge of. That is, a linear high-strength refractory layer B is located at the center along the delivery direction of the delivery mechanism, and the high-strength refractory layer B at the center is sandwiched between the heat-resistant refractory materials A ₁ , A ₂ will be symmetrically located on both sides. Although FIG. 2 shows one side dam, the other side dam has the same configuration.

As shown in FIG. 4, the width C of the narrowest gap of the rolls 1a and 1b
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 sheet to be cast contacts at the side dam portion corresponding to the narrowest gap. Since the thickness of the thin plate is approximately equivalent to the width C of the narrowest gap, the width b _{1 of the} linear high-strength refractory layer B (3rd
It is sufficient that the figure) corresponds approximately to the width C of the narrowest gap.

In reality, the linear high-strength refractory layer B occupies only a part of the plate-shaped side dam, and the width b of the side dam that is in contact with the molten metal is approximately equal to the width C of the narrowest gap. It is only necessary to have ₁ , but this high-strength refractory layer B
In order to integrally and firmly bond the heat-resistant refractories A ₁ and A ₂ with good machinability, as shown in FIG. 3, the linear high-strength refractory layer B has a convex cross section. It is good to choose one. That is, the inner side surface of the side dam, which comes into contact with the molten metal in the pool, has a small width of b ₁ and the outer surface has a large width of b ₂ , and the small width b ₁ has a thickness corresponding to the thickness W _{1 of the} side dam. Or, the thickness should be greater than this, and the thickness b ₂ should be within the thickness W ₂ of the side dam. By using such a convex cross-section, it is possible to obtain a joining structure in which resistance to vibration and stress is provided while increasing the joining area between the refractory materials A and B.

Boron nitride (BN) or graphite is suitable as the high-strength refractory layer B, and Al ₂ O ₃ fiber board is suitable as the machinable refractory material A. Alternatively, the high-strength refractory layer B may be a high-density Al ₂ O ₃ fiber board and the machinable refractory layer A may be a low-density Al ₂ O ₃ fiber board. In any case, the high-strength refractory layer B has a high machinability in comparison with A but is inferior in heat insulation property as compared with A, but it is sufficient to suppress overhang of the cast plate edge. Since it is a different resistor and its width b ₁ is narrow, even if the heat insulation performance is slightly inferior, the molten metal in the pool is prevented from cooling and solidifying at this part. This was verified by the following operation example performed by the present inventors.

The inner cooling rolls 1a and 1b with a diameter of 850 mm and a width of 600 mm were set with a clearance of 2.00 to 3.00 mm in the narrowest gap, and the side dams 3a and 3b were fed at a feeding speed of 2 to 10 mm / min, while Sheet thickness from molten steel 2.00 to 3.0 at casting speed of ~ 30mm / min
A thin plate with a width of 0 mm and a width of 530 mm was manufactured. Side dams 3a and 3b are W
₁ = 35 mm, W ₂ = 25 mm, width of high strength refractory layer B ₁ = 2.00 to 3.0
0 mm and b ₂ = 60 mm. At that time, as the refractory of A and B constituting the side dam, (1) B is boron nitride (BN: density 1.0 to 1.7 g / cm ³ , bending strength 3.2 kgf / mm ² ), and A is A
l ₂ O ₃ fiber board (density 0.3g / cm ³ , bending strength 0.05kgf
/ mm ² ) integrally molded product, and (2) B is Al ₂ O ₃ fiberboard baked product (density 0.5 to 0.6 g / cm ³ ), A is Al ₂ O ₃ fiberboard (density 0.3 g / cm ³ ), An integrally molded product was used.

As a result, when using either side dam of (1) or (2), the problem due to defective shell did not occur. Although a slight solidification was also observed in the portion B, the width was within the range of the gap width of the narrowest gap of the roll, and it did not spread beyond that, which was not a problem. Further, spalling due to the difference in thermal expansion coefficient between A and B, which was a concern, showed the effect that the low-density products located on both sides absorb the thermal expansion of the high-density product, and there was no problem. Furthermore, 1TD complete casting (about 1 ton) was possible without any dripping on both ends of the cast plate, and a thin plate of about 2 mm x 530 mm could be manufactured over 100 m.

As described above, according to the present invention, the weakest part, which is the tip of the side dam, can be covered with a high-strength product, and the tip is not damaged even under the influence of vibration such as roll rotation, and stable casting can be performed. However, even if the molten steel level fluctuates slightly, the solidification completion position fluctuates, and the width-spreading position of the cast plate fluctuates, the rate at which the sand dam refractories are scraped off decreases. In addition, to prevent sand shell development on the inner surface of the side dam, even if molten steel flow is collected in the vicinity of the side dam, the side dam is less eroded and a good side dam shape can be maintained, and some roll gap fluctuations occur during casting. However, since the tip of the side dam can maintain a stable shape without abnormality, the object of the present invention described at the beginning can be effectively achieved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an essential part of an embodiment of the apparatus according to the present invention, FIG. 2 is a perspective view showing an example of the shape of a refractory of a side dam in the apparatus of FIG. 1, and FIG. 3 of FIG. Of the side dam
FIG. 4 is a schematic side view for explaining the positional relationship between the roll pair and the side dam, taken along the line III-III 'of FIG. 1a, 1b …… pair of internal cooling rolls, 2 …… bath, 3a, 3b ……
Side dam, 4 …… Casted cast plate, 6,6 ′ …… Side dam bottom surface curved to correspond to the circumferential shape of the roll, 7,7 ′ …… Side dam in sliding contact with the roll side surface , 10 …… Rough part of the circumferential surface of the roll that is in sliding contact with the bottom surface of the side dam, A ₁ , A ₂ …… Adiabatic refractory with good machinability, B …… High-strength refractory, C… … Width of narrowest gap, b ₁ …… Width of inner surface of side dam of high-strength refractory, W ₁ …… Thickness of side dam in contact with roll circumferential surface, W ₂ …… Side dam located outside roll circumferential surface Thickness.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Hanashi 4976 Tomita, Shinnanyo-shi, Yamaguchi Prefecture Shunan Steel Works, Nisshin Steel Co., Ltd. (72) Inventor Tomoaki Kimura 3-1-1, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Works, Ltd. (72) Inventor Tadashi Nishino 3-1-1 Sachimachi Hitachi City, Ibaraki Prefecture Hitachi Ltd., Hitachi Works (56) References JP-A-63-26241 (JP, 63-26241) A)

Claims (6)

[Claims] 1. A pair of inner cooling rolls, which rotate in mutually opposite directions, are arranged so as to face each other with their axes parallel to each other, and a pair of side dams for forming a basin on the circumferential surface of the roll pair are provided. It is arranged at the side part of the roll pair so that at least a part thereof is located on the circumferential surface of the roll, and a feeding mechanism for feeding this side dam in the casting direction is provided. The contacting roll circumferential surface is formed into a rough surface with grinding ability,
In a thin plate continuous casting machine that casts while damaging the side dam sent out by the sending mechanism by the rough surface, the side dam portion that is worn away by the circumferential surface of the roll pair has good machinability And the side dam portion that comes into contact with the edge of the thin plate to be cast is composed of a high-strength refractory material with poor machinability. A thin plate continuous casting machine characterized by being sent to 2. The side dam has a linear high-strength refractory layer located in the center along the feeding direction of the feeding mechanism, and a heat-insulating property having good machinability with the central high-strength refractory layer sandwiched therebetween. 2. The thin plate continuous casting machine according to claim 1, wherein the refractory material is a plate-shaped body located on both sides, and the central high-strength refractory material layer and the machinable refractory material layers on both sides are integrally formed. 3. A central high-strength refractory layer is boron nitride (BN),
The thin plate continuous casting machine according to claim 2, wherein the machinable refractory layers on both sides thereof are made of Al ₂ O ₃ fiber board. 4. A high-strength refractory layer in the center has a high density of Al ₂ O ₃ fiberboard, and machinable refractory layers on both sides thereof have a low density.
The thin plate continuous casting machine according to claim 2, comprising an Al ₂ O ₃ fiber board. 5. The thin plate continuous casting machine according to claim 2, wherein the high-strength refractory layer in the center is made of graphite, and the machinable refractory layers on both sides thereof are made of Al ₂ O ₃ fiber board. 6. The thin plate continuous casting machine according to claim 1 or 2, wherein the high-strength refractory material has a width substantially corresponding to the gap width of the narrowest gap portion of the roll pair.