JPH024753Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The technology described in this specification is a thin-walled slab continuous casting machine (hereinafter referred to as "thin-walled slab continuous casting machine") that directly produces thin-walled slabs with a thickness of 50 mm or less from molten metal, such as molten steel. Regarding belt casters (referred to as "belt casters"), this is a proposal for a belt guiding/sealing member that is particularly useful for controlling a running water film in the belt width direction when attached to a belt cooling device (cooling pad) using a running water film.

(Prior Art) A continuous thin-walled cast slab casting machine for continuously producing steel plates such as sheet bars directly from molten steel: A belt caster has already been disclosed in, for example, Japanese Patent Application Laid-Open No. 100851/1983. There are various types of these known belt casters, but a typical belt caster is a belt caster that uses a plurality of guide rolls to maintain a gap for holding molten steel over a predetermined distance. A pair of metal belts (the back side is cooled by a cooling water film and supports the long sides of the cast slab) are placed opposite each other and move in a circular motion. It usually has a structure in which a casting space is defined on four sides by a pair of side plates for the short sides that are in contact with each other. A cooling pad is provided on the back surface of the metal belt to form a cooling water film of a predetermined thickness for supporting and cooling the static pressure of the molten steel inside the metal belt.

Now, the function of the cooling pad described above is that the static pressure caused by the molten steel or semi-solidified slab changes as it moves from the hot water level in the slab drawing direction. ) The size and arrangement of the water supply hole facing the metal belt of the cooling pad and the flow rate supplied thereto are adjusted so that the static pressure of the molten steel (tension applied to the belt) and the pressure of the cooling water film are balanced. There is.

(Problems to be Solved by the Invention) The above-mentioned conventional water film cooling using a cooling pad has the following problems 1 and 2.

(1) The thickness of the running water film is not uniform, which tends to cause uneven cooling, which leads to belt deformation and slab deformation. This means that the thickness of the water film can be controlled to some extent by applying tension in the pouring direction, but in the width direction of the slab, there is no restraining force at all, so the thickness of the water film tends to change. by.

Regarding this point, since the rigidity of the belt usually has a greater influence on the change in the thickness of the water film than the belt tension, it is possible to counteract the change in the thickness of the water film by increasing the thickness of the metal belt. There is. However, unnecessarily increasing the thickness of the metal belt is not advantageous because it reduces the cooling effect or further increases the temperature of the metal belt. Further, in the width direction of the belt, water flows out at the ends, making it difficult to form a water film pressure, resulting in wasted water. Moreover, a different pressure distribution is formed in the width direction of the belt, causing non-uniformity in the thickness of the water film. In other words, in the belt width direction,
Since the ends of the belt are open, it is unavoidable that the cooling water supplied into the water film will flow out from the ends of the belt.If water is supplied evenly across the width of the belt, the amount of water flowing out at the ends of the belt will decrease. will increase.

Therefore, the floating shape of the belt due to the water film is such that the central portion in the width direction of the belt is relatively protruded and convex compared to the end portions, resulting in a defective slab having a concave shape.

Furthermore, the speed of cooling water passing through the belt end is determined by the difference between the internal pressure of the water film and the outside air pressure, and therefore cannot be changed in response to the thermal load on the molten steel or slab.

Since the cooling capacity is determined approximately by the flow velocity, for example, if the flow velocity at the end of the belt is lower than the required flow velocity, the temperature at the end of the belt will become high, and in the worst case, the belt will be deformed.

The above factors cause non-uniform cooling in the belt width direction, causing belt deformation and eventually deformation of the slab.

(2) The running water film near the side plate for sealing between the short side support side plate and the metal belt becomes uneven, which causes belt deformation. That is, in general, in order to prevent molten steel from being inserted between the side plate and the metal belt, the clearance for forming a water film between the side plate and the metal belt is set to be small. For this reason, as shown in FIG. 5, the metal belt becomes inwardly convex, and the water film thickness distribution changes greatly in the belt width direction, resulting in a cooling water flow rate distribution (difference) in the belt width direction. (more in the center and less on both sides).

That is, since the belt end is open, the cooling water flows out from there, and the cooling water pressure at the position corresponding to the side plate contact portion decreases. In order to obtain a predetermined pressure, a larger amount of cooling water must be supplied to the portion corresponding to the side plate contact position than to the center of the width. This increase in the amount of water naturally causes an increase in the amount of water flowing into the center of the width, so that the amount of protrusion at the center of the width further increases and the amount of belt deformation also increases.

If the amount of cooling water at the center of the belt width direction is not increased, from the side plate to the outside (belt side edge)
Since the water film pressure decreases toward the side, the pressing force of the metal belt against the side plate part is weakened, and the insertion of molten steel is facilitated. Further, even if the clearance between the side plate and the metal belt portion is made small, the pressure of the running water film will not increase and there will be no effect.

The object of the present invention is to eliminate the adverse effects caused by uneven cooling of a metal belt, particularly at the both side edges of the belt, and to prevent deformation of the belt and slab.

(Means for solving the problem) The above problem (1) is that it is difficult to control the thickness of the running water film in the belt width direction as a whole, and the thickness of the running water film near both side edges of the belt (near the side plates) can be controlled. In order to solve the above problem (2), the present invention consists of a pair of metal belts on the long sides that move circularly while maintaining a gap to hold the molten metal and slabs with the help of cooling pads. In a continuous casting machine for thin-walled cast slabs, which is composed of a pair of side plates for short sides that are located between the metal belts and are in close contact with them, the back side of the metal belts controls the introduction and discharge of cooling water flow. A continuous thin-walled cast piece characterized in that a belt end seal member for suppressing the pressure of the cooling water film from the opposing direction is provided at both ends of the cooling pad, protruding so as to close both side edges of the belt. A casting machine is the solution.

In particular, it is preferable that the belt end sealing member is formed of a rigid member or a rigid member with an elastic member interposed in a portion thereof.

By providing belt end sealing members on both side edges of the cooling pad as in the present invention, it is possible to prevent cooling water from flowing out in the belt width direction at both side edges of the belt, thereby saving wasted cooling water for forming a flow film. At the same time, the pressure of the running water film can be easily applied to both side edges of the metal belt, and the thickness of the running water film in the belt width direction can be easily controlled.
In other words, in order to avoid cooling water flowing out from the end of the belt, it is possible to control supply and drainage in a closed system with a running water film spanning the belt width direction, and the thickness of the running water film can be controlled to be constant across the belt width direction. Problem (1) is resolved. In addition, there is no need to press down the belt with the side plate at the part where it contacts the side plate, and the pressure is suppressed by the sealing member; preferably, the pressure is elastically suppressed, so it is easy to build up pressure near the side plate, and the flow rate can be secured. The flow rate distribution in the belt width direction can also be made uniform. That is, since the belt end sealing member allows the running water film to form a closed system across the belt width, the film thickness can be maintained constant by controlling supply and drainage within this system. Therefore, belt deformation is avoided, and the water film pressure near the side plate can be increased, and the above problem (2) is solved.

Next, the operation of the present invention will be described in detail.

When cooling a metal belt with cooling water, unless the cooling water boils, the cooling capacity is determined by the flow rate; if the flow rate is slow, the cooling capacity is small, and conversely, if the flow rate is fast, the cooling capacity is large. It is important to ensure the minimum cooling capacity to cool and solidify the slab.

If the minimum cooling capacity is not reached, the temperature of the belt will rise, causing the cooling water near the belt to boil, and although the rise in belt temperature will stop at a certain temperature, this will lead to uneven belt temperature. This results in a uniform bottom thermal stress distribution in the belt, and also in the distribution of compressive and tensile stresses within the belt. Then, due to the increase in compressive stress, the belt is plastically deformed and eventually remains as a permanent deformation.

On the other hand, when the belt end is closed with a belt end sealing member to create a system in which the running water film is closed in the belt width direction, a flow rate that satisfies the required cooling capacity can be ensured under a constant film thickness. In other words, a constant film thickness can be achieved by appropriately selecting the means of supply and drainage.

However, in the past, cooling water flowed out from the belt ends, so the thickness of the water film at the belt ends was smaller than that at the center of the belt width, and the cooling capacity at the ends was determined by the flow rate of the water flowing out at the ends. Therefore, the required minimum cooling capacity cannot always be secured, and the temperature at the belt ends increases, causing belt deformation.On the other hand, if the flow rate is increased blindly to protect the belt ends, the supply/drainage balance at the center of the belt width will be balanced. collapses, and the thickness of the running water film in the center increases. The increase in film thickness is not necessarily proportional to the increase in flow rate, so even though the flow rate is increased,
The flow rate may decrease. As a result, the temperature at the center of the belt increases. Therefore, it can be seen that the uneven cooling of the belt occurs because the flow rate of the cooling water flowing out from the belt end cannot be controlled.

As mentioned above, by providing a belt end sealing member, the flow rate of cooling water can be controlled over the entire width of the belt, which prevents the central part of the belt from becoming convex. A running water film of uniform thickness is obtained.

(Example) Fig. 4 shows a perspective view of a general continuous caster for thin-walled slabs to which the present invention is applied. Metal belts 7 and 8 are cooling pads.

A preferred embodiment of the present invention includes the cooling pad 7,
8, belt end seal members 10, 10a having a structure as shown in FIGS. 1 to 8 are provided.

That is, in the example shown in FIG.
This is an example in which cooling pads 7 and 8 are protruded from both ends.
The belt end sealing members 10, 10a are structured to block the outflow of the cooling water for forming a running water film discharged from the water supply port 12 of the cooling pad, and are arranged in the direction in which the metal belt swells due to the pressure of the running water film. The shape is such that both side edges of the metal belts 4 and 5 are pressed from opposite directions.

Note that since there is less need for cooling at both ends of the belt, the condition is satisfied even if there are no or small discharge holes, and the water film pressure is more likely to increase.
However, in the parts that have a curved structure,
When tension is applied, a force is generated in the direction of crushing the running water film, so the gaps shown in FIGS. 2 and 3 need to be relatively small. In addition, the static pressure of molten steel is applied to other parts, so the water film pressure decreases, so it is necessary to set the value of the gap δ to an appropriate number, but in general,
Approximately 0.2 to 1 mm is appropriate.

On the other hand, in order to provide flexibility in the value of δ, a structure in which the force that suppresses the metal belt is constant is also effective.

This example is shown in FIGS. 2 and 3. In this structure, the metal belts 4 and 5 are held down with a constant force by attaching an elastic member 11, such as a telescopic bellows that does not impair sealing performance. However, a lower limit is set for the thickness suppressed by this elastic member 11 (for example, 0.3 mm), so that the metal belts 4, 5 and the pads 7, 8 do not come into contact and create resistance to the sliding of the metal belts 4, 5. I'll take it into consideration. In this way, when the water film pressure increases, the water film thickness increases and the water film pressure decreases, a phenomenon that is repeated, and the film pressure becomes stable at a certain constant level.

Note that the value of d in FIG. 2 is preferably set to 10 mm or more, taking into consideration the meandering of the metal belts 4 and 5.

Example of operation using the device of the present invention The belt end sealing member of the present invention was adopted in the belt caster shown in Figure 4.

Conventionally, the distance between the side plate and the metal belt was set to 0.3
mm, there was no lateral seal at all where there was no side plate. As a result, it was not possible to maintain a running water film of uniform thickness on the back surface of the metal belt, and the belt thermal deformation was particularly large at the end of the slab (near the side plate), and the slab itself was also concave (1.5 to 2 mm).

Therefore, we adopted the present invention, and in the narrowing section, δ = 0.3
mm, and δ = 0.5 mm was adopted for parts without side plates.
Also, the setting between the side plate and the metal belt was changed to 1.0mm. As a result of conducting operations based on these design changes, a running water film of a constant thickness was maintained even when the metal belt cooling water, which conventionally required 6 t/min, was reduced to 4 t/min. There was no deformation at the center of the belt, and no thermal deformation of the belt was observed at the position corresponding to the end of the slab. This is thought to be because there was no wasted water in the width direction, and a sufficient amount of water was secured even near the side plates, eliminating uneven cooling of the metal belt. Also, although the slab is slightly concave, the difference is less than 0.2 mm, which is a great improvement compared to the conventional method.

(Effects of the invention) As explained above, according to the invention, both side edges of the metal belt, which were conventionally supported by the balance between the water film pressure and the side plates, can be supported by the belt end sealing member, so that the belt width direction can be increased. The flow rate distribution of the cooling water becomes uniform, and sufficient water film pressure can be formed near the side plate portions, thereby preventing thermal deformation of the belt and deformation of the slab.

[Brief explanation of drawings]

FIGS. 1a and 1b are cross-sectional views showing the belt end sealing member of the present invention together with a cooling pad, FIGS. 2 and 3 are cross-sectional views showing another embodiment of the present invention, and FIG. FIG. 5 is a perspective view of a continuous thin slab casting machine, and a cross-sectional view showing a conventional belt support system using a running water film. 1... Molten steel, 2, 3... Guide roll, 4, 5
... Metal belt, 6 ... Side plate, 7, 8 ... Cooling pad, 10, 10a ... Belt end seal member,
11...Elastic member, 12...Water supply port.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A pair of metal belts on the long sides that rotate while maintaining a gap for holding molten metal and slabs with the assistance of a cooling pad, and a gap between the metal belts. In a thin slab continuous casting machine, which is composed of a pair of short-side side plates that are in close contact with the thin-walled slab side plates, there are two side plates on both sides of the cooling pads that control the introduction and discharge of cooling water flow on the back side of the metal belt. 1. A continuous caster for thin-walled cast slabs, characterized in that belt end sealing members for suppressing the belt from a direction opposed to the pressure of the cooling water film are protruded so as to close both side edges of the belt. 2. The continuous thin slab casting machine according to claim 1, wherein the belt end sealing member is formed of a rigid member or a rigid member partially interposed with an elastic member.