JPH0790335B2 - Twin roll type continuous casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is intended to form a pool on the circumferential surface of internally cooled twin rolls which are opposed to each other and are arranged in parallel with a narrow gap therebetween. The side dams are placed on the circumferential surfaces of both sides of the twin rolls, and the molten metal in the pool is cooled and solidified on the roll surface while pressure is applied in the narrowest gap between the rolls to continuously cast thin plates. The present invention relates to improvement of a roll-type continuous casting machine.

[Prior Art and Background of the Invention]

Attempts have been made to apply a twin-roll type continuous casting machine to the production of thin steel plates, and many proposals have been made to improve the continuous casting machine.

The twin roll type continuous casting machine is basically equipped with a pair of internal cooling type rolls arranged in parallel with their axes parallel to each other with a predetermined gap therebetween,
A pool is formed on the circumferential surface of the twin rolls, and while the molten metal in the pool is cooled by the rotating twin roll surface, this cooling causes both solidified shells (solidification shell) to grow on both roll surfaces. ) Are pressure-bonded to each other at the narrowest gap of twin rolls to directly produce a thin plate. Therefore, it is necessary to properly form a pool on the circumferential surface of the rotating twin rolls. For this purpose, the molten metal leaks on the side (the end side of the roll) on the circumferential surface of the twin rolls. It is at least necessary to form a dam so that it does not. This dam is called a side dam, and both sides are usually configured the same.

There are roughly two types of known methods for installing this side dam.

One is in contact (sliding contact) with both side surfaces of the twin rolls (outer surfaces orthogonal to the axes of both ends of the roll).
It is a method of forming a wall. In this method, since the side dam is applied from the outside of the roll, the roll width substantially corresponds to the plate width to be cast.

The second is a method of raising a side dam on the circumferential surface of a twin roll. That is, the bottom of the side dam is raised on the surface of the twin rolls so that the bottoms of the side dams come into sliding contact with the circumferential surfaces on both sides of the twin roll. In this method, the width of both side dams substantially corresponds to the width of the plate to be cast.

The present invention relates to an improvement of a twin roll type continuous casting machine that adopts the second side dam installation method. In the case of this second method, the roll surface is divided into a portion that comes into contact with the high-temperature molten metal and a portion that does not come into contact with it (for example, a portion that comes into sliding contact with the bottom of the side dam).

In JP-A-59-30455, in a twin roll type continuous casting machine adopting the second method, cooling water of a different system is introduced to the back surface of the roll at the contact portion with the molten metal and the non-contact portion. For the non-contact part, we have proposed a method of passing cooling water at a higher temperature than the contact part.

[Object of the Invention]

An object of the present invention is to solve various problems due to roll expansion in a twin roll type continuous casting machine adopting the second side dam installation method. More specifically, in this method, a temperature difference occurs on the roll surface between the roll circumferential surface that comes into contact with the high temperature molten metal and the circumferential surface that does not come into contact with the molten metal (for example, the portion where the side dam exists). A difference in roll expansion appears and the roll is deformed. However, the problem of the roll deformation is described in the above-mentioned JP-A-59-30.
An object of the present invention is to provide a roll structure that more effectively prevents the cooling water temperature from being controlled as in Japanese Patent No. 455.

[Structure of Invention]

The object of the present invention to achieve the above-mentioned object is that the bottom portion of the roll is provided on the circumferential surface of an internally-cooled twin roll which is opposed to each other with a narrow gap and rotates in opposite directions. A pair of side dams are set up so as to be in sliding contact with the circumferential surface, and the molten metal in the pool formed by these side dams and the circumferential surface of the twin rolls is cooled and solidified on the roll surface while the narrowest gap between the rolls is formed. In a twin-roll type continuous casting machine that press-bonds with a double roll to continuously cast a thin plate, the outermost circumferential layer of the twin roll that rotates integrally with the twin roll body is composed of a roll sleeve made of copper alloy, and A cooling water passage is provided on the back surface of the corresponding roll sleeve, and a heat insulating layer, for example, an air layer, is formed on the back surface of the roll sleeve corresponding to the portion not in contact with the molten metal.

The contents of the present invention will be specifically described below with reference to the embodiments of the drawings.

[Detailed Description of the Invention]

FIG. 1 is a schematic diagram showing the main part of a twin roll type continuous casting machine to which the present invention is applied. The internal cooling type twin rolls 1a and 1b are shown in FIG.
Are arranged parallel to each other with their axes horizontal and with a predetermined gap, and they rotate in the opposite directions in the directions of the arrows.
The pool 2 is formed on the circumferential surface R of the twin rolls 1a and 1b, and the molten steel in the pool 2 is the circumferential surface R of the twin rolls 1a and 1b.
While being cooled above, the thin plate 3 is cast through the narrowest gap.

In order to form the pool 2 on the circumferential surface R of the twin rolls 1a, 1b, the side dams 4a, 4b are raised on the circumferential surface R in the plane perpendicular to the axes of the twin rolls 1a, 1b. That is, on the circumferential surface R of the twin rolls 1a and 1b, the bottom portion is the circumferential surface R.
The pair of side dams 4a and 4b are slidably contacted with the twin rolls 1a,
It is launched on both sides of 1b. The side dams 4a, 4b are made of refractory due to their heat resistance and erosion resistance against molten steel.
A cooled plate is attached to the outside of the, and the side dams 4a and 4b are fixed at predetermined positions by this cooling plate.

FIG. 2 schematically shows a roll structure according to the present invention. Although only one roll 1a is shown in the drawing, the other roll 1b has the same structure. As shown in the figure, the roll of the present invention is constructed by coating a roll sleeve 6 made of a copper alloy on the circumferential surface of a steel roll body 5. Here, “adhered” means that the roll body 5 and the roll sleeve 6 are joined to each other as shown in FIGS. Therefore, as the roll body 5 rotates about its axis, the roll sleeve 6 also rotates integrally with it. A high strength alloy such as a precipitation hardening type copper alloy is preferable as the copper alloy constituting the roll sleeve 6, and has a tensile strength of 30 kgf / mm ² or more at a temperature of 0 to 300 ° C. and a thermal conductivity of 0.6 cal / cm.sec.
A temperature above ℃ is suitable.

A cooling water passage 7 is spirally formed along the circumferential direction on the back surface of the roll sleeve 6 corresponding to the portion in contact with the molten steel. In the illustrated example, a spiral groove is preliminarily cut on the outermost circumferential surface of the steel roll body 5, and the surface of the roll body 5 having this groove is covered with a roll sleeve 6 to cool the cooling water. A passage 7 is formed. Cooling water is introduced into the cooling water passage 7 from a cooling water introduction pipe 8 passing through the axis of the roll body 5, and is discharged to the outside of the system via a cooling water drain pipe 9 also passing through the axis of the roll body 5. . On the other hand, a heat insulating layer 10 is formed on the back surface of the roll sleeve 6 corresponding to the portion that does not come into contact with the molten steel (the portion where the side dam exists and, in some cases, further to the side thereof). The heat insulating layer 10 is a layer that blocks the transfer of heat from the roll sleeve 6 to the roll body 5. In the illustrated example, air is interposed as a heat insulating material between the roll sleeve 6 and the roll body 5. ing.

FIG. 3 is a schematic cross-sectional view showing the cross section of the roll in FIG. 2 as a vertical cross section passing through the roll axis, and shows the mounting relationship between the cooling water passage 7 and the heat insulating layer 10. The part where the outermost surface of the copper alloy roll sleeve 6 contacts the molten metal is a side dam.
The width W is between 4a and 4b, and the portions where the side dams 4a and 4b are located and the sides thereof are not in contact with the molten steel.
In the present invention, the cooling water passage 7 is provided on the back surface of the roll sleeve 6 corresponding to this width W to forcibly cool the portion of this width W, but the non-contact portion with the molten steel is not forcibly cooled, and conversely on the back surface thereof. The heat insulating layer 10 is provided to insulate heat received from the contact portion so that the temperature of the roll sleeve 6 in the non-contact portion with the molten steel approaches the temperature of the roll sleeve 6 in the contact portion. This heat insulating layer 10 has a depth on the surface of the roll body 5.
It is desirable to form a groove of 0.5 mm or more and cover the groove with the roll sleeve 6 to form a cavity in which air is interposed. The width of this groove should preferably occupy 50% of the width of the non-contact portion, and in some cases, it can be formed by a plurality of grooves. It is also desirable to attach a heat insulating material to the side surface of the roll sleeve 6 that comes into contact with the atmosphere to prevent heat radiation from the side surface.

[Action]

When a copper alloy is used as the material of the roll sleeve 6, the sleeve temperature is lower than that when steel is used, and as a result, the amount of thermal expansion can be reduced. This means that the coefficient of linear expansion of copper alloy is higher than that of steel (18 × 10 ^{-6 for} copper alloy).
° C. relative to ^-1, 14 × 16 ^-6 ℃ ^-1 in steel), since towards the copper alloy has a larger thermal conductivity than steel (0.84Ca is a copper alloy
l / cm.sec. ° C, while for steel 0.12 cal / cm.sec.
C). The present inventors solved the unsteady heat transfer equation by referring to the measurement data of the surface temperature of the roll sleeve during casting and the solidification rate data. The result is shown in FIG. As can be seen from the results in this figure, the difference between the front and back temperatures of the sleeve is much smaller for copper alloys than for steel. Furthermore, when the amount of thermal expansion of the roll sleeve in the radial direction was calculated using this temperature profile, the result was that the copper alloy was about 75% of the steel. The following equation was derived as the amount of thermal expansion in the radial direction (Δr).

Where a: inner radius, b; outer radius, α: coefficient of linear expansion, T (r):
Sleeve temperature profile, T ₀ : initial sleeve temperature, ν:
Poisson's ratio.

More importantly, because copper alloys have high thermal conductivity,
Heat transfer from the contact area with the molten metal to the non-contact area is large and the temperature difference in the roll width direction is small. The inventors of the present invention measured the surface temperature of the roll sleeve during casting using a surface thermometer.
The results shown in the table were obtained (the casting conditions were the same for both, and the contact portion and the non-contact portion were internally cooled under the same conditions).

In the case of casting with a copper alloy sleeve, the thickness difference between the plate edge and the center of the obtained plate was about 1/4 of the latter when compared with the case of casting with a steel sleeve. .

Therefore, when the copper alloy sleeve is used, the so-called inverted crown shape in which the central portion of the cast plate becomes thinner than the end portions is alleviated. The presence of the inverted crown causes partial extension in the subsequent cold rolling step and a normal plate shape cannot be obtained, but this problem can be partially solved by using a copper alloy sleeve.

However, this alone is not enough to resolve the inverted crown shape. That is, the temperature uniformity in the width direction of the roll sleeve cannot be achieved only by using the copper alloy. In order to achieve this, it is necessary to bring the temperature of the non-contact portion of the sleeve which is in contact with the molten metal close to the temperature of the contact portion. It is characterized in that a heat insulating layer is provided on the back surface of the roll sleeve.

When this heat insulating layer is provided, the molten steel is approximately
The heat generated from the molten steel itself can be accumulated at the sleeve width end due to the extremely high heat flux of 1 Kw / cm ^{2 and} the fact that the copper alloy is a good conductor of heat. Can be warmed. That is, as described with reference to FIG. 3, the back surface of the roll sleeve 6 other than the width W that comes into contact with the molten steel has a supporting structure in which it does not come into contact with the roll body 5 as much as possible (the heat insulating layer 10 using air as a heat insulating material By providing the roll sleeve 6, the back surface of the roll sleeve 6 comes into contact with air, and heat transfer to the roll body 5 is suppressed. Air is an easy and effective thermal insulator in the present invention. For example, the heat transfer coefficient at the sleeve / air interface is about 10 ^-3 cal / cm ² .sec.
In contrast, the heat transfer coefficient at the sleeve / water interface is about 10 ^-1 to 10 ^-2 cal / cm ² .sec. ° C. Also, as shown in FIG. 4, when the width end of the roll sleeve 6 is brought into close contact with the roll body 5 by, for example, shrink fitting, the heat transfer coefficient between the sleeve and the roll body is increased. Is about
It is 10 ^-1 cal / cm ² sec., Which is about 100 times that of the sleeve / air interface. Therefore, it is preferable to form the heat insulating layer 10 composed of voids in the presence of air according to the present invention in terms of the heat insulating effect and the simplicity of the structure.

In the case of FIG. 4, even if the roll sleeve 6 is made of a copper alloy, a temperature difference occurs in the roll sleeve at the contact portion W with the molten steel and the other non-contact portion (the roll main body at the non-contact portion). Since heat flows to No. 5 and heat is not stored), a crown shape as shown by a dotted line is generated.

Hereinafter, an operation example of continuously casting a thin plate of stainless steel using the apparatus of the present invention will be given together with comparative examples.

Example 1 The twin roll type continuous casting machine shown in Figs. 1 to 3 in which the material of the roll body 5 is a steel alloy and the material of the roll sleeve 6 is a precipitation hardening type Cr-Zr copper alloy is used. The roll sleeve 6 made of the copper alloy has an outer diameter of 400 mmφ, an inner diameter of 320 mmφ, a thickness of 40 mm and a width of 300 mm. This roll sleeve 6
Side dams 4a and 4b, which were erected so that their bottoms were in sliding contact with the circumferential surface of, were made of fused silica and had a thickness of 25m.
m. Each of the side dams 4a and 4b was set up so that the outer wall surface thereof was in the same vertical plane as both end faces of the roll sleeve 6. 2mm deep groove on the surface of the roll body 5 from both sides
The heat insulating layer 10 in which air is present was formed by cutting up to 5 mm inside and covering the groove with the roll sleeve 6. A cooling water passage 7 is provided on the back surface of the roll sleeve 6 that comes into contact with the molten steel between the two side dams 4a and 4b, and normal temperature water is flown through the cooling water passage 7 at a flow rate of 1 m / min.

The distance between the narrowest gaps of the twin rolls was set to 2.5 mm, and molten steel of SUS304 was poured into the pool 2 and cast at a speed of 25 m / min.
The plate thickness in the width direction was measured 1 minute after the start of casting. The results are shown in Table 2.

Example 2 (Comparative Example) The material of the roll sleeve 6 is S40C medium carbon steel, and as shown in FIG. 4, the roll sleeve 6 and the roll body 5 are in close contact with each other in the non-contact part with molten steel. Using the same twin-roll type continuous casting machine as in Example 1 except that a heat insulating layer was not provided, casting was performed under the same conditions as in Example 1. The results of measuring the plate thickness at the same time points as in Example 1 are shown in Table 3.

[Brief description of drawings]

FIG. 1 is an overall perspective view showing an example of a twin roll type continuous casting machine,
FIG. 2 is a partially cutaway perspective view for explaining the roll structure of the present invention, FIG. 3 is a schematic cross-sectional view showing the internal structure of the roll of the present invention cut along a vertical plane passing through the roll axis, and FIG. Is a schematic cross-sectional view showing the internal structure of a roll of a comparative example cut by a vertical plane passing through the roll axis, and FIG. 5 is a temperature profile diagram of front and back temperatures of a steel sleeve and a copper alloy sleeve. 1a, 1b ...... twin rolls, 2 ...... pool, 3 ...... thin sheet to be cast, 4a, 4b ...... side dam, 5 …… roll body, 6 …… roll sleeve, 7 …… cooling water passage, 10… … Insulation layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-17169 (JP, A) Actually opened 61-58948 (JP, U) Actually opened 60-113149 (JP, U)

Claims (2)

[Claims] 1. A pair of side dams are provided on the circumferential surfaces of internally-cooled twin rolls, which are opposed to each other with a narrow gap and rotate in opposite directions, so that their bottoms are in sliding contact with the circumferential surfaces of the rolls. A twin roll type in which the molten metal in the pool formed by both side dams and the circumferential surface of the twin rolls is started up and is pressure-bonded in the narrowest gap between the rolls while being solidified by cooling on the roll surface and continuously cast into a thin plate. In the continuous casting machine, the outermost circumferential layer of the twin rolls that rotate integrally with the twin roll body is composed of a roll sleeve made of copper alloy, and cooling water passages are provided on the back surface of the roll sleeve corresponding to the part that contacts the molten metal. A twin-roll type continuous casting machine characterized in that a heat insulating layer is formed on the back surface of the roll sleeve corresponding to the portion that does not come into contact with the molten metal. 2. The heat insulating layer is an air layer.
Twin roll type continuous casting machine according to the item.