JPH0732096A - Slab continuous casting method and apparatus - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides continuous casting means for completing solidification by supporting only unsolidified molten steel in the solidified shell from immediately below the mold of the slab continuous casting machine to the completion point of solidification. provide. In a slab continuous casting apparatus for solidifying and drawing a cast piece from molten steel, the casting apparatus comprises a mold 3 for forming a solidified shell of molten steel, a mold vibrating device 4, and a cast piece 7 while growing the solidified shell. It is composed of a secondary cooling device 5 for solidifying and a slab lowering device 9 for holding and moving the bottom of the slab directly below the mold. [Effect] Multi-size, small lot materials can be efficiently cast, diversification of user needs can be met, construction cost can be reduced by utilizing existing equipment, and the cost of small lot production can be reduced. The rise can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab continuous casting method and apparatus for casting and solidifying molten steel from immediately below a mold without restraining the solidified shell on the surface of the slab.

[0002]

2. Description of the Related Art At present, the production ratio by continuous casting in steel production has already reached a level of over 90%, but continuous casting is being advanced from the viewpoint of quality stability and cost saving.

At present, the continuous casting machine tends to be a high-production continuous casting machine by direct connection, synchronization with a rolling machine, high-speed casting, etc. aiming at energy saving and process saving of the continuous casting process.

Under these circumstances, steel types that are not currently continuously cast are difficult to continuously cast due to their components, the order lot is small, the casting size is large, and the casting speed cannot be increased. For these reasons, it cannot be efficiently incorporated into an existing high-productivity continuous casting machine, so that it is produced by the ordinary ingot casting method, which is inferior to the continuous casting method in terms of cost and productivity.

[0005]

On the other hand, even for steel grades already produced by continuous casting machines, there is a tendency for the quality to become higher, the variety of products to be produced, and the lots to be made smaller due to the diversification of user needs. Therefore, as a result, there are some steel grades that have to be manufactured by conventional conventional ingot making.

These steel types can be incorporated in continuous casting production by performing continuous casting of different steel types, but workability and productivity such as separation for suppressing mixing of components and insertion of iron plate are impaired. ， When it is not possible to sufficiently suppress the component mixing of joints of different steel types, scrap the component mixing part, or install a small lot material below the manufacturing lot of the refining furnace that supplies molten steel to continuous casting, store it There is a problem such as increase of surplus materials accompanied by fees.

[0007] In the case of a thick plate, generally, the allocation rate allocated to the original standard within three months after the surplus material is generated decreases as the order lot becomes smaller, and becomes 150 ton.
The allocation rate is less than 50% for lots of less than one year.

Considering the total quantity of orders received, 150t
The generation amount of casting lots of on / year or less varies depending on the month, but is 5,000 to 20,000 tons per month, which is extremely small. Therefore, when considering an apparatus dedicated to small lot materials for the purpose of eliminating the disadvantage of producing small lot materials with a high production continuous casting machine, it is necessary to make a continuous casting machine that can be realized with extremely inexpensive equipment investment.

From the above, it is to realize a continuous casting machine for producing small lot materials, which can efficiently continuously cast small lot materials including sizes outside the manufacturing range of the existing continuous casting machines which satisfy the following requirements. is necessary. The concept of the continuous casting machine for small lot production is shown below.

(1) A small lot can be efficiently produced. That is, it can flexibly cope with casting of small lots. (2) Applicable to multi-size casting including large-section slabs.
That is, the casting size range can cover the range from general-purpose continuous casting thickness to slab size. (3) The yield and production efficiency are superior to those of the ordinary ingot making method. In other words, it is possible to reduce the hot top and shorten the track time including solidification time. (4) Low equipment investment for low-volume production and therefore low merit, that is, compact equipment that can utilize existing cranes and buildings, equipment that has only the functions required for operation, and simple equipment for operation and maintenance. To be.

The present invention realizes the concept for the continuous casting machine described above, and efficiently performs casting of multi-size and small lot materials which will be increased in the future due to the delay of continuous casting or diversification of user needs. A slab continuous casting method and apparatus are provided.

[0012]

According to the method of the present invention, solidification is completed by supporting unsolidified molten steel in the solidified shell from immediately below the mold of the continuous casting machine for slabs up to the solidification completion point only by the solidified shell. It is a slab continuous casting method characterized by the above.

Further, the apparatus of the present invention is a continuous casting apparatus for solidifying and drawing a slab from molten steel, the casting apparatus comprising a mold for forming a solidified shell of molten steel and a mold vibrating device.
A slab continuous casting apparatus comprising a secondary cooling device for solidifying a slab while growing a solidified shell and a slab descending device for holding and moving the bottom of the slab directly below the mold. is there.

[0014]

The present invention will be described in detail below together with its operation.

One of the features of the present invention is that the slab guide equipment of the conventional continuous casting machine for slabs is eliminated and the apparatus is simplified.

A conventional continuous casting machine cools molten steel in a mold to form a solidified shell. Then, it is drawn out from the mold by a cast piece drawing device and cooled in the secondary cooling zone while being restrained by the guide rolls.

One of the functions of the guide roll and the secondary cooling in the continuous casting machine is to prevent the solidified shell from being deformed (bulging) by the static pressure of molten steel. Since bulging occurs due to the static pressure of molten steel, the greater the static pressure of molten steel,
Further, the thinner the solidified shell is, the larger it becomes, but the width and thickness of the slab are also large, and so-called bloom or slab with a narrow slab width (thickness) is less likely to cause bulging than the long side.

In the secondary cooling zone, the slab is cooled by spray cooling or steam cooling, but the corners of the slab are cooled from both the short side and the long side of the slab, or the secondary cooling is performed. Since the water for use is discharged through the corners of the slab after colliding with the slab, it is cooled more strongly than the central part of the long and short sides, the solidified shell grows and the temperature of the solidified shell decreases at the same time. The strength of the corner solidified shell is higher than that of the central solidified shell.

FIG. 1 shows the effect of slab width on bulging. From FIG. 1, the shape factor (α) shows a substantially constant value in the case of a slab width of 1 m or more, but decreases in the range of 0.6 to 0.8 m or less and tends to be difficult to bulge. This behavior is considered to indicate that the solidified shell at the corner has a restraining force against the bulging at the center of the width of the slab and suppresses the bulging.

Even in actual casting, the so-called blame with a narrow width (thickness) of the slab or the short side of the slab is not installed with a slab guide roll until the solidification is completed, but the shape of the slab is controlled. That is consistent with

On the other hand, a continuous casting machine for casting a slab in which the effect of suppressing the slab corners against bulging does not work is conventionally manufactured with a specification of casting at a high casting speed, placing importance on productivity, and slabs immediately below the mold. Sufficient solidified shell strength cannot be obtained over the range until the solidification is completed, and on the long side, a slab guide device is installed immediately below the mold, thereby maintaining the slab shape to the specified shape and the secondary cooling device. Generally, the method of cooling by cooling to complete the solidification is essential, and the guide device on the long side of the slab is indispensable.

Therefore, the equipment cost is higher than that of a continuous casting machine for bloom in which the guide rolls need to be installed only in a limited area immediately below the mold.

However, even in the case of a slab width of 1 m or more, if the casting method in which the strength of the solidified shell is strengthened by controlling the casting speed and the slab cooling temperature in the secondary cooling zone, it is installed in the conventional slab continuous casting machine. Without the guide roll
Casting is possible while supporting the unsolidified molten steel in the slab with only the solidified shell, and the shape of the slab can also be controlled.

FIG. 2 shows the relationship between the casting speed, the secondary cooling temperature and the slab bulging amount. The casting conditions in this case are: slab size: slab width 1,800 mm, casting thickness 350
mm Casting speed: 0.1 to 0.5 m / min Cooling temperature of slab: 2 levels of 600 ° C. and 800 ° C. Mold length: 1000 mm (effective length: 900 mm).

As can be seen from FIG. 2, the bulging amount can be controlled by the casting speed and temperature. Note that bulging of the slab requires a facility and operational response in terms of transportation of the slab and securing of the rolling shape, so the allowable amount of slab deformation is determined by considering these factors. One side is preferably 50 mm or less.

Further, as described above, the required monthly production amount by the small lot continuous casting machine is 10,000 to 20,0 a month.
Since it is very small like 00 tons, even a low-speed casting type low-production continuous casting machine can realize a continuous casting machine that sufficiently achieves its purpose.

The present invention provides a slab continuous casting method and apparatus based on a new idea that a slab guide device, which has been indispensable in a conventional continuous casting machine, is not installed by controlling the casting speed and the slab cooling temperature in the secondary cooling zone. Is provided.

That is, the present invention is (1) a slab continuous casting method in which the unsolidified molten steel in the solidified shell is supported only by the solidified shell from immediately below the mold of the continuous slab casting machine to the solidification completion point, and solidification is completed, (2) As a continuous casting device for solidifying and drawing a slab from molten steel, a mold and a mold vibrating device that form a solidified shell of molten steel, a secondary cooling device that solidifies the slab while growing the solidified shell, and directly below the mold It is a slab continuous casting device configured only by a slab lowering device that holds the bottom of a slab and moves it.

[0029]

EXAMPLE FIG. 3 shows an example of the continuous casting machine of the present invention.

The continuous casting machine shown here has a width changeable mold 3, a mold vibrating device 4, a slab cooling device 5, a slab lowering device 9 for holding and moving the slab bottom, and a slab moving device stopper 11. The slab lowering device 9 can stop and hold the cast slab at an arbitrary position between immediately below the mold 3 and the slab moving device stopper 11.

Further, since this continuous casting machine eliminates the slab guide which has been indispensable for the conventional slab continuous casting machine, it is extremely easy to change the casting size and is restricted by the conventional slab guide equipment specifications. It is possible to design a continuous casting machine capable of casting an extremely wide size in which restrictions on the thickness of the castable slab are alleviated.

The operation method will be described below.

(1) Preparation for pouring is completed by raising the dummy block 8 just below the mold by the cast piece lowering device 9 and sealing the space between the mold 3 and the dummy block 8.

(2) Casting is moved to the upper part of the mold, and is poured into the mold 3 from the ladle 1 stopped and held, and the molten steel such as the tundish 2 is held, and is poured into the mold 3 through a pouring device (not shown) such as a stopper installed in the feeding device. The molten steel poured into is cooled by a mold to form a solidified shell.

(3) After the solidified shell is formed in the mold, the cast slab 7 is continuously withdrawn from the mold as the slab lowering device 9 descends. However, the cast slab is different from a normal slab continuous casting machine. While passing the molten steel inside the slab by only its own solidified shell, it passes through the inside of the secondary cooling device 5 and is cooled and solidification proceeds.

The secondary cooling device 5 can be moved by the drive device 6 and has a structure capable of changing the casting size.

(4) At the stage where casting has been performed for the specified length within the stroke range of the slab lowering device 9, the injection from the supply device is stopped and the slab 7 is completely solidified. The specified length is set in consideration of the required slab length and the cut-off amount of the top and bottom parts of the slab, and keeping the crude slab yield high.

(5) After the injection is completed, the ladle 1 and the tundish 2 are retracted from the continuous casting machine until the cast piece reaches the completely solidified state, and the cast piece 7 after the injection is stopped or lowered, It is kept in a continuous casting machine until it is completely solidified.

(6) The mold 3 is opened at the long and short sides or retracted from the casting position in order to take out the slab.

(7) FIG. 4 is a view showing a state in which the mold 3 is opened and the cast slab 7 is taken out by the tongs 12. When the slab 7 is completely solidified, the slab is first lowered. Raised by device 9.

(8) When the top of the cast piece comes out of the upper surface of the operation floor, the rise of the cast piece 7 is stopped, and the tongue 12 is used to carry the cast piece out of the continuous casting machine by the upper crane.

(9) After the cast slab is carried out of the continuous casting machine, the casting size is changed and the mold is maintained, and the next operation is started.

Although FIG. 3 shows the method of raising and lowering the slab lowering device 9 by means of the hydraulic cylinder 10, a method of raising and lowering by means of a winch or the like is also possible. Further, the secondary cooling device 5 can be moved at a suitable time when the casting size is changed or the slab is carried out by a driving device.

Further, using the drive device of the secondary cooling device 5,
If the secondary cooling device on one side is greatly retracted, as shown in FIG.
A method of overturning the slab 7 inside the continuous casting machine and carrying it out of the continuous casting machine is also applicable.

3 and 4 show only one continuous casting machine, two or more continuous casting machines are arranged in parallel, and each tundish is cast from a large-capacity ladle to separate water. Alternatively, it is also possible to use one tundish common to many continuous casting machines and cast simultaneously.

The function of the tundish in this case is to receive the molten metal from the ladle and distribute it to the strands of the continuous casting machine, and Japanese Patent Publication No. 2-38302.
As shown in Japanese Patent No. 299753, a heating device and a stirring device attached to a tundish having a refining function of holding and homogenizing an injection temperature and adding an alloy are also applicable. As an alloy to be added, for example, Si-M
n, Fe-Si, Fe-Mn, Fe-Nb, Fe-Ti
Can be considered.

[0047]

As described above, according to the present invention, immediately below the mold of the continuous casting machine, the unsolidified molten steel in the solidified shell up to the solidification completion point is supported only by the solidified shell to complete solidification,
By repeatedly casting these, it is possible to efficiently perform casting of multi-size, small lot materials, respond to diversifying user needs, and use existing cranes and buildings, as well as construction costs. The cost is low and the increase in cost due to small lot production can be suppressed.

[Brief description of drawings]

FIG. 1 is a drawing showing the influence of slab width on bulging of a slab.

FIG. 2 is a drawing showing the effects of casting speed and secondary cooling temperature on bulging of cast slabs.

FIG. 3 is a side sectional view showing an example of the continuous casting machine of the present invention.

FIG. 4 is a drawing showing a situation in which a cast piece cast by the continuous casting machine shown in FIG. 3 is taken out.

[Explanation of symbols]

 1 Ladle 2 Tundish 3 Mold 4 Mold Vibrating Device 5 Secondary Cooling Device 6 Secondary Cooling Moving Device 7 Casting Slab 8 Dummy Block 9 Slab Dropping Device 10 Hydraulic Cylinder 11 Stopper

Claims (2)

[Claims] 1. A continuous casting method for slabs, characterized in that unsolidified molten steel in the solidified shell up to the point where solidification is completed is supported by only the solidified shell to complete solidification immediately below the mold of the continuous casting machine for slabs. 2. A continuous casting apparatus for solidifying and drawing a cast piece from molten steel, the casting apparatus comprising a mold for forming a solidified shell of molten steel and a mold vibrating device, and solidifying the cast piece while growing the solidified shell. A slab continuous casting apparatus comprising a secondary cooling device and a slab lowering device that holds and moves the bottom of the slab directly below the mold.