JPS6339340B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to
This invention relates to a method for manufacturing thin metal sheets with a thickness of ~20 mm by continuous casting.

(Prior art) Conventionally, in order to manufacture thin metal plates, such as thin steel plates, a steel ingot is bloomed to obtain a slab with a thickness of 200 to 250 mm, and this slab is hot-rolled in a hot strip mill. Alternatively, a slab is obtained by continuously casting molten steel, and the slab is hot rolled.

However, when using these conventional techniques,
It is desired to develop a technique for directly obtaining thin plates by continuous casting of molten steel in large-scale hot strip mills and places that require energy to heat slabs.

Conventionally, when continuously casting molten steel, a method has generally been used in which the molten steel is injected into a mold, solidified around the cross section, and then pulled out downward. However, with this method, it is difficult to obtain slabs with a thickness of several tens of millimeters or less due to the relationship between the diameter of the nozzle through which molten steel is injected into the mold and the cross-sectional dimensions of the mold. Friction between the slab and the inner wall of the mold Therefore, it is difficult to increase the slab drawing speed to 2 m/min or more, and there is a risk that if it is increased to 2 m/min or more, there is a risk that the solidified shell will break and a flow of molten steel will blow out (breakout). Ta.

In order to solve these problems in the conventional continuous casting process and provide an efficient manufacturing method and apparatus for continuous casting of thin plates, the present inventors previously filed Japanese Patent Application No. 56-188862 (Japanese Unexamined Patent Application Publication No. 58-188). In JP-A-90357), we proposed a method and apparatus for manufacturing thin metal sheets by single-sided casting.

In other words, it is a method of casting thin steel plates by pouring molten steel onto a flat plate forming an inclined endless track, with the casting direction and the direction of the flow of poured molten steel being reversed, that is, the flat plate forming an endless track moves upward on the slope. molten steel is poured onto a flat plate under conditions of a belt mechanism having an inclined plane and a means for supplying molten metal downward onto the inclined belt plane; a device for extracting slabs on the upper side of the inclined plane; This is a continuous casting device for molten metal, which consists of a device driven by

This device is shown in FIG.

In FIG. 3, reference numeral 11 is a casting belt or endless track, which is driven in the direction of arrow A. 12
13 is a belt drive wheel, 13 is a tundish, 14 is molten steel, and 15 is a solidified thin plate, that is, a slab.

When molten steel is continuously cast into a thin plate using this device, the molten steel 14 is supplied flowing down from the tundish 13 onto the surface of the belt 11, and is kept constant on the surface of the belt 11 which is inclined by gravity. Flowing down the distance. Since the belt 11 is moving upward on the slope (in the direction of arrow A), in a steady state, the front end 17 and rear end 18 of the molten steel flow are connected to the tundish 1.
The molten steel flows from point 19 from point 19 to a substantially constant relative position.

A solidified shell develops on the belt 11 as it advances from the molten steel flow tip 17 in the direction of arrow A, and eventually passes through the molten steel to become a completely solidified thin plate, which is wound up by a winding device.

With this technique, steel plates with a thickness of 2 to 20 mm can be manufactured by continuous casting. According to this technology, molten steel (molten metal) solidifies on a track plane that is inclined and moves upward, and the extraction speed of the solidified shell (slab) and the moving speed of the track plane (belt) are synchronized. If this is done, breakout due to friction between the belt surface and the slab will not occur, so the casting speed can be dramatically increased.

In addition, since it is one-sided solidification, the bottom surface of the slab is in contact with the belt surface during casting, but the top surface is in contact with the molten steel or the atmosphere, and since there is no space constraint such as a mold, the molten steel is transferred from the tundish to the tundish. There are no problems with the nozzle arrangement for supplying the water.

However, even in the above-mentioned process for manufacturing thin metal sheets by casting, there are still technical problems that need to be solved.

That is, the position of the molten steel flow tip 17 on the belt plane shown in FIG. 3 must be stable, and the molten steel flow flat end plane shape must be uniform in the belt width direction. Otherwise, a pattern due to hot water wrinkles will be formed on the lower surface of the thin sheet obtained by casting, which will significantly impair the surface quality of the thin sheet.

4 and 5 show the planar shape of the molten steel flow tip 17 on the belt plane.

It is necessary for the quality of manufactured products that the molten steel flow tip 17 on the belt plane has a tip shape as shown in FIG. 4 and that its position in the belt movement direction is stable.

From this point of view, Japanese Patent Application No. 188862 (1983)
Even in the technique previously proposed by the present inventors in Japanese Patent Publication No. 58-90357, there still remained technical problems to be solved. The present inventors further discovered that the planar shape of the molten steel flow tip 17 on the belt plane is uniform in the belt width direction as shown in FIG. 4, and that the position of the molten steel flow tip 17 is stabilized in the belt movement direction. A method for this purpose was proposed in Japanese Patent Application No. 58-30362 (Japanese Unexamined Patent Publication No. 59-156554).

That is, the molten steel flow tip 17 on the belt plane
By providing a weir on the belt plane, continuous casting is performed while stably maintaining the desired position and desired planar shape on the belt plane.

The weir is formed by an insulating solid, or a heated or sublimating solid, or a gas jet. FIG. 2 shows one aspect of this.

In the embodiment shown in FIG. 2, a solid weir 2
1 is arranged to hold the molten steel pool 7 above the solidification shell 6. It goes without saying that the solid weir 21 has a required width in the width direction of the belt 11.

The solid weir 21 has its support rod 22
It is fitted into a tube 23 having an inner diameter larger than the outer diameter of the belt 11, and is therefore movable in the vertical direction, so that it can follow the vertical movement of the belt 11.

Since the solid weir 21 shown in FIG. 2 is constructed as described above, the bottom surface of the solid weir 21 is
It contacts the surface of the belt 11 with a force equal to its weight and that of its support rod 22.

For this reason, the solid weir 21 cannot follow sudden fluctuations in the vertical direction of the belt 11, and the belt 11
A gap was generated between the surface of the solid weir 21 and the bottom of the solid weir 21.

Further, as the belt 11 moves, the solid weir 21 is pulled in the moving direction of the belt 11 by friction between the surface of the belt 11 and the bottom of the solid weir 21, and is fitted with the solid weir support rod 22. Since there is a gap between the solid weir 21 and the pipe 23, the solid weir 21 vibrates, and this also causes a gap between the surface of the belt 11 and the bottom of the solid weir 21.

In this way, molten steel is inserted into the gap created between the surface of the belt 11 and the bottom of the solid weir 21, and due to the insertion of the molten steel, a wrinkly pattern is formed on the side of the cast thin plate that is in contact with the belt 11. This caused a problem in that the surface quality of the cast product (thin plate) was significantly impaired.

(Problems to be Solved by the Invention) This invention solves the above-mentioned belt problem in a process in which molten steel is poured onto the flat plate (belt) forming an inclined endless track and slabs are extracted upward from the inclined flat plate. In order to prevent the deterioration of the surface quality of the cast product (thin plate) caused by the gap between the belt and the bottom of the weir installed at the tip of the molten steel flowing down the surface, we created a gap between the bottom of the weir and the belt surface. The purpose is to provide a method to prevent this from occurring.

(Means for Solving the Problems) The gist of this invention is to pour molten metal onto a metal plate that moves upwards on a slope, and cast the metal onto the slope upward of the moving metal plate that forms the slope. In a continuous thin plate casting method that extracts thin plates,
A weir is provided at the tip of the flowing molten metal poured onto the slope of the moving metal plate so that at least a part of the lower surface thereof is in contact with the surface of the moving metal, and the weir is elastically supported with respect to the moving metal plate. A hot water boil prevention method characterized by casting the weir with elastic support for the moving metal plate. The above-mentioned method for preventing boiling water by pressing the weir against the movable metal plate and the elastic support for the moving metal plate of the weir are such that the fulcrum of the weir support is placed at a position other than the surface of the weir, and the weir is supported by a spring so as to rotate around the fulcrum. Accordingly, in any of the above-mentioned methods of preventing hot water from forming, the weir is supported by a moving metal plate under pressure.

This invention will be explained in detail below.

In the weir structure at the front end of the molten steel flow on the belt surface, which was previously proposed by the present inventors in Japanese Patent Application No. 58-30362, when the belt 11 is suddenly displaced in a direction perpendicular to the surface, the weir A gap is created between the belt surface and the bottom surface of the weir due to the fact that the belt cannot be displaced at a speed that does not create a gap between the belt surface and the belt surface in a direction perpendicular to that surface. Ta.

Therefore, in the present invention, the weir is configured to elastically support and press the belt against the surface.
An example of an apparatus for implementing the present invention is shown in FIG. In FIG. 1, 11 is a belt, 1 and 2 are weir members, and 3 is a frame. 4 is a spring,
The corner portion formed by the weir members 1 and 2 is pressed against the surface of the belt 11 and supported.

5 is a fulcrum, and the weir constituted by the weir members 1 and 2 and the frame 3 is displaced so as to rotate around this fulcrum 5.

6 is a solidification shell, and 7 is a molten steel pool.

When the weir is supported elastically against the surface of the belt 11, when the weir is displaced in a direction perpendicular to the surface of the belt 11, the weir can be displaced to follow the belt 11 at a speed higher than the displacement speed. It has to be something.

By the way, if we consider the relationship between the belt 11, weir, and spring as a model as shown in Fig. 6, the equation of motion is mx ₁ + c (x ₁ − x ₂ ) + k (x ₁ − x ₂ ) = 0……(
1) is given by. Here, m is the mass of the weir, x ₁
is the displacement of the weir, _x2 is the displacement of the belt, c is the damping coefficient, and k is the spring constant.

Asinω ₀ t (A: _amplitude , ω ₀ :
Substituting the angular velocity, t: time) and solving equation (1), we get (Here, q=ωn√1− ² , ζ=c/c _C , c _C =2
√, ωn=√, m=W/g, φtan ^-1
[(ζω ₀ /ωn)/(1−ω ₀ ² /ωn ² )]).

The first term on the right side of equation (2) is 0, so in a steady state, In order to prevent hot water from pouring in, it is necessary to select a spring with a spring constant k that will keep the gap (x ₁ −x ₂ ) between the belt and the weir at 0.1 mm or less.

In one embodiment of the present invention, x ₁ −x ₂ =0.1×
10 ^-3 m, A=2×10 ^-3 m, ζ=0.01, m=1.02Kg
Casting was carried out at s ² /m, ω ₀ =20.9 rad/s.

When these values are substituted into equation (3), the spring constant k becomes k=9.4Kg/mm. Therefore, in order to perform continuous casting with a gap of 0.1 mm or less between the weir and the belt,
A spring 4 with a spring constant of 9.4Kg/mm or more is required.

On the other hand, the upper limit of the spring constant is limited by the belt driving force and the frictional force between the belt and the weir bottom surface. From this point of view, in this example, the spring constant k is k=15
A tabular spring with kg/mm was used.

By the way, the present inventors previously filed a patent application No. 58-30362.
In the weir structure at the tip of the molten steel flow on the belt surface proposed in this issue, the solid weir 21 is connected to the belt 1.
1 is pulled in the moving direction of the belt 11 by friction between the surface of the belt 11 and the bottom surface of the solid weir 21, and a gap is created between the solid weir support rod 22 and the pipe 23 in which it is fitted. Since there is a solid weir 21
vibrated, and this also caused a gap between the surface of the belt 11 and the bottom of the solid weir 21.

Therefore, in the present invention, the weir constituted by the weir members 1 and 2 and the frame 3 is configured to rotate around the fulcrum 5 as described above. By configuring in this way, the backlash in the mechanical system is eliminated in this system, and the occurrence of a gap between the bottom surface of the weir and the surface of the belt 11 due to backlash in the mechanical system is better suppressed. .

Furthermore, in the present invention, at least the corner portions of the weir members 1 and 2 that are in contact with the surface of the belt 11 are
It is composed of an elastic member such as ceramic fiber, alumina fiber, glass fiber, asbestos, etc.

Since the present invention is constructed as described above, the weir is always in close contact with the belt surface even when the belt 11 undergoes sudden vertical vibrations, and no gaps are formed.

Although the above explanation has been made regarding continuous casting of thin steel sheets from molten steel, it is understood that this invention is not limited to continuous casting of molten steel, but can also be applied to continuous casting of metals other than steel. Of course.

(Example) Molten steel was cast into a 10 mm thick steel strip using the apparatus shown in FIG. 1 having the spring 4 with a spring constant k=15 Kg/mm described above.

A partial sketch of the belt contacting surface side of the slab (steel strip) at this time is shown in FIG. A steel strip with good surface quality and no wrinkles on the surface of the slab was obtained.

For comparison, FIG. 8 shows a partial sketch of the belt contacting surface of the steel strip when molten steel is cast into the steel strip using the conventional apparatus shown in FIG. 2. There are wrinkles in a wide range of slabs (steel strips) caused by pouring molten steel into the weir bottom and belt surfaces.

(Effects of the Invention) Since the present invention is configured and operated as described above, when continuously casting a thin plate from molten metal, the casting process caused by the insertion of molten metal between the solid weir and the belt can be avoided. To prevent deterioration of the surface quality of a thin plate and to enable production of a thin metal plate with excellent surface quality.

[Brief explanation of drawings]

Fig. 1 is an elevational view illustrating an example of an apparatus for carrying out the method of the present invention, Fig. 2 is an elevational view illustrating an example of holding the tip of molten steel using a conventional apparatus, and Fig. 3 is a continuous casting process. 4 and 5 are plan views showing the planar shape of the lower end of the injection flow in the process shown in Fig. 3. Fig. 6 is a spring system model showing the relationship between the belt, weir, and spring. Fig. 7 is a partial sketch showing the surface properties when molten steel is cast into a steel plate by the method according to the present invention, and Fig. 8 is a partial sketch showing the surface properties when molten steel is cast into a steel plate by the conventional technique. It is a partial sketch diagram showing properties. 1, 2... Weir member, 3... Frame, 4... Spring, 5... Fulcrum, 6... Solidification shell, 7... Molten steel pool, 11... Casting belt or endless track,
12...Mold drive wheel, 13...Tandateshitsu,
14...Unsolidified molten steel, 15... Solidified thin plate, 17,
17'... Molten steel tip, 18... Molten steel rear end, 19...
... Molten steel falling point, 21... Solid weir, 22... Solid weir support rod, 23... Pipe.

Claims (1)

[Claims] 1. A method for continuous casting of a thin plate, in which molten metal is poured onto a metal plate moving upward on a slope, and a cast thin plate is extracted upward from the slope of the moving metal plate forming the slope. , a weir is provided at the tip of the flowing molten metal poured onto the slope of the moving metal plate so that at least a part of the lower surface thereof is in contact with the surface of the moving metal, and the weir is elastically applied to the moving metal plate. A hot water boil prevention method characterized by supporting and casting. 2. The elastic support of the weir for the moving metal plate is achieved by constructing the lower part of the weir with a highly elastic material and pressing the lower surface of the weir against the surface of the moving metal plate using a spring. How to prevent boiling water. 3. Elastic support for the moving metal plate of the weir is achieved by placing the fulcrum of the weir support at a position other than the surface of the weir, and pressing and supporting the weir against the moving metal plate using a spring so as to rotate around the fulcrum. A method for preventing boiling water according to claim 1 or 2.