JPH02263551A - Method and apparatus for continuously casting cast strip - Google Patents

Abstract

PURPOSE:To stably and continuously cast a cast strip having excellent surface characteristic and the quality by pressing the cast strip remaining unsolidified part drawn out from a mold to width direction from both sides with plural liquid lubricating press plates and forming this to the prescribed thickness in order. CONSTITUTION:The size of both short side walls sandwiched with long side walls is substantially equalized to the aimed cast strip thickness and the cast strip is drawn out from both end opened mold 4 having cross sectional shape, where facing inner faces at center part of the long side walls are retreated and separated by distance to be possible to use a submerged nozzle 3. At the position remaining the unsolidified part in the cast strip, plural liquid lubricating press plates 6 constituting pressing curve face 5 are set so as to gradually squeeze the distance between both bulging faces of the cast strip formed at the center part of the long side walls in the mold from inlet side toward outlet side direction. Then, the cast strip drawn out from the mold is passed from both sides toward thickness direction with plural liquid lubricating press plates 6 to gradually form the prescribed thickness. By this method, the cast strip having good quality can be continuously cast at good workability.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a continuous casting method for thin metal slabs of good quality;
This invention also relates to continuous casting equipment used therein.

<Conventional technology and its issues> In recent years, significant advances in refining technology and casting technology have made it easier to manufacture slabs with good quality properties, and against the backdrop of the growing awareness of labor and energy conservation, hot rolling has become increasingly popular. Attempts have been made to directly and continuously produce thin sheets from molten metal without any melting, and efforts have been made not only for non-ferrous metals with relatively low melting points, but also for ferrous metals.

The following methods have been proposed as means for continuously casting thin metal slabs.

a) Continuous casting method using a belt-type wall moving mold (vertical or horizontal).

b) Continuous casting method using a modified cross-section mold called '5M5 (Schlemann-Simark) method (Japanese Patent Laid-Open No. 1983
-158955, JP-A-62-203651.

JP-A-62-203652, JP-A-62-220
(See Publication No. 249). This 3M3 type continuous casting method is as shown in Fig. 10 (Fig. 10 (a) is a plan view, Fig. 10 (b) and Fig. As another example, FIG. 10(C) shows a sectional view taken along the line C-C), the inner surface of the mold long side wall 21 expands at the center to form the pouring part 22, and the long side wall An inverted triangle that narrows as the pouring part goes down toward the mold exit side [Figure 10 (
b)] or rectangular (Fig. 10, 6)] in a continuous casting mold with both ends open.

However, among these methods, "method using a belt-type wall-moving mold route" has the problem of high maintenance costs and running costs due to the difficulty of belt cooling, and in addition, this type of mold requires a large amount of installation work. There was a problem in that unless pouring was carried out using a ``immersion nozzle,'' which was often difficult, the situation would fluctuate widely and it would be difficult to maintain quality. In addition, in the above-mentioned "3M3 type continuous casting method," the cross-sectional area of the slab is gradually but greatly reduced within the mold, so a large frictional force is generated between the inner surface of the mold and the surface of the slab, and this frictional resistance causes the inner surface of the mold to It has been pointed out that there is a problem that the mold life is shortened due to severe wear, and because the mold structure has a gradually shrinking cross-section, the scene fluctuations are amplified by mold oscillation, which has a negative impact on the quality of the slab. Its existence was also recognized.

As described above, the conventional continuous thin slab casting methods have many unresolved problems from the perspective of stably producing thin slabs of sufficiently satisfactory quality with good workability. At present, the results have not reached the level where it can replace the conventional method involving hot rolling, especially in the industrial production of iron-based metal sheet materials.

Therefore, in view of the above circumstances, the present inventors first aimed to continuously cast ferrous metal thin sheet materials such as steel at a stable and low cost without deteriorating quality or workability. However, [other than securing a cross-sectional bulge in the center area in the width direction that is large enough for the immersion nozzle to penetrate, the thickness of the thin slab is the same as the target, and the cross-section is substantially the same from the malt inlet side to the malt outlet side. Continuous casting is performed using a shaped mold with both ends open, and the bulge in the thickness direction of the slab pulled out of the mold is placed in a vibrating press while the unsolidified portion remains within the slab. proposed a method for continuous casting of thin slabs by compressing them in the thickness direction from both sides to a predetermined thickness.
-165395).

However, when this method is examined in detail, it is found that the method of forming the slab before it is completely solidified using a vibrating press has the following drawbacks:
There are concerns about ``increase in drawing resistance'' and ``deterioration of surface quality'' due to difficulty in sufficiently avoiding friction and wear between the slab and the press surface. I had to admit that there were still some issues that warranted some leeway.

<Means for Solving the Problem> Based on the above, the present inventors have developed a more practical method that does not require a particularly large burden in terms of equipment costs, etc., and can ensure smoother operating conditions. In order to establish a method for continuous casting of thin cast slabs, we continued experiments and studies from a broader perspective, and found that ``the immersion nozzle penetrates into the center of the width, similar to what the inventors proposed earlier.'' Continuous casting was carried out using a mold with both ends open, which was the same as the target thin slab except for securing as much cross-sectional bulge as possible, and had a substantially similar cross-sectional shape from the mold entry side to the mold exit side. At that time, the bulge in the thickness direction of the slab that is pulled out of the mold is not a "vibration press" but a "multiple pressing curved surface that is gradually narrowed as it goes in the direction of pulling out the slab". If you use a "liquid lubricated press plate (a press plate with a pressure liquid film formed on the surface)" and perform compression molding sequentially while the unsolidified part still remains in the slab, it will be possible to use a vibrating press. We have come to the conclusion that the above-mentioned problems that have been pointed out have been sufficiently eliminated."

The present invention has been made based on the above-mentioned findings, etc.
) is the A-A cross-sectional view of the same) and as shown schematically in FIG. A slab drawn from a mold 4 with both ends open, having a cross-sectional shape that is substantially the same and whose opposing inner surfaces at the center of the long side walls are set back and spaced apart (separated by a distance e) to enable the use of the immersion nozzle 3. A pressing curved surface 5 is formed at a position within a range where an unsolidified portion remains within the mold so that the distance between the re-expanded surfaces of the slab formed at the center of the long side wall of the mold is gradually narrowed from the inlet side to the outlet side. A plurality of liquid lubricant press plates 6 are arranged, and the remaining unsolidified slab pulled from the mold is compressed from both sides in the thickness direction by the plurality of liquid lubricant press plates 6 to sequentially make it to a predetermined thickness. It is characterized by the fact that it is possible to continuously cast high-quality thin slabs with good workability.'' The dimensions of the short side walls 2, 2 are substantially the same as the target thickness of the thin slab, and the opposing inner surfaces at the center of the long side walls are set back and separated by an amount (distance e) that enables the use of the immersion nozzle 3. A mold 4 whose cross section is open at both ends and whose cross section is spaced apart by a distance of and a plurality of liquid lubricant press plates 6 forming a pressing curved surface that gradually reduces the distance between the re-expanded surfaces of the slab formed in the inlet side toward the outlet side.'' As illustrated in FIG. 3, the liquid lubricated press device used for continuous casting of the thin slabs includes a plurality of press plates 6 facing the surface of the slab pulled out from the mold, and a press device ( (not shown in FIG. 3), the press plate 6 has a concave pressure liquid port 12 and a drain groove 13 formed on the surface facing the slab, and the pressure liquid port 12 is A pressure liquid supply device (not shown) is connected through a pressure liquid supply path 14 passing through the press plate 6, and a drain path 15 passing through the press plate 6 is connected to the drain groove 13. ”
It also has the following characteristics.

In the drawings, numeral 7 is a press device, 8 is a molten metal,
9 is a solidified shell, 10 is a support roll.

Reference numeral 16 indicates each liquid supply pipe.

By the way, in the mold according to the present invention, the lengths of the left and right short sides in the cross section are the same as the thickness of the target thin slab, and the lengths of the short sides are the same as the thickness of the target thin slab, and the lengths of the short sides are the same in the vicinity of the center of the inner surface of the long side walls in order to facilitate pouring with an immersion nozzle. It has a so-called "deformed cross section" in which the cross section is receded so that the distance is wider than the side length, but as shown schematically in Fig. 1, the cross section from the mold entry side to the mold exit side is The shape is substantially the same in all parts.

Of course, "substantially the same" here means that the cross-sectional shape does not change noticeably from the mold entrance side to the mold exit side, as in the case of the 3M3 type mold shown in FIG. 9, for example. Needless to say, those in which the cross section is slightly narrowed from the mold entry side to the mold exit side are included in the category of ``substantially the same''. Furthermore, since a mold with a slightly narrowed cross section from the inlet side to the outlet side as described above can effectively accommodate the shrinkage allowance of the slab,
Rather, it should be actively adopted.

The "liquid lubricated press plate" used here means that a pressure liquid film is formed on the surface of the press plate that press-forms the slab, and the pressure liquid film is formed without substantially direct contact between the press plate surface and the slab. 4(a) and 4('b) as shown in FIG. 3, or as another example, as shown in FIG. A large number of concave pressure liquid ports 12 and drain grooves 13 are formed between the pressure liquid ports on the surface of the press plate 6 facing the slab, and each pressure liquid port 12 is provided with a press plate. The pressure liquid supply device is connected to the pressure liquid supply path 14 passing through the plate 6, and the drain path 15 passing through the press plate 6 is connected to the drain groove 13. It is practical to use a type that forms a pressure liquid film between the press plate 6 and the slab by supplying pressure liquid into the pressure liquid port 12 through the pressure liquid port 14.

Note that, as shown in the above drawings, it goes without saying that the pressure liquid port 12 and the pressure liquid supply path 14 may be of the same size or different sizes. Moreover, it goes without saying that this liquid lubricated press plate is used while being supported by a press device.

Here, in order to strengthen the liquid lubrication and furthermore effectively press and support the slab through the liquid, the viscosity of the pressure liquid used is μ = 1,002 cP (to the viscosity of water at 20°C). (equivalent) or higher is recommended. In addition, "liquid" here
The term "solid-liquid mixed fluid" is also included, and for example, it may be [graphite particles + rapeseed oil].

In addition, since the amount of solidification shrinkage of slabs differs depending on the steel type, casting speed, etc., in order to properly approach the liquid lubricated press plate to the slab surface for effective press forming and support, it is necessary to adjust the pressing curved surface as described above. From this point of view, the pressing curved surface needs to be constructed by gathering a plurality of liquid-lubricated press plates so that the pressing curved surface can be changed freely.

As the shape of each press plate, a hexagonal shape (tortoiseshell shape), a square shape (lattice shape), a short circular shape, etc. may be adopted as appropriate.

Furthermore, the position of the liquid lubricated press plate is such that the forming effect of press compression cannot be obtained at a position beyond the unsolidified end of the slab, but at other positions from directly below the malt to the unsolidified end of the slab. It may be in any position if there is one.

Therefore, it may be installed directly below as shown in Figure 2, or
As shown in FIG. 5, it may be placed at the unsolidified end of the slab at some distance from the mold without any problem.

The continuous casting apparatus according to the present invention is particularly beneficial when applied to the production of thin cast slabs of steel, but it goes without saying that it can also be applied to the production of thin cast slabs of non-ferrous metal materials other than steel.

Next, an example of a continuous casting process for thin slabs using the continuous casting apparatus according to the present invention will be described with reference to FIG. 2.

<Function> First, as mentioned above, the double-end open mold 4 according to the present invention allows the general immersion nozzle 3 for continuous casting of thick slabs to be inserted as is, so there is no need to take any special measures. The molten metal is poured into the mold 4 by the immersion nozzle 3 as usual.

Therefore, there are extremely few changes in the scene during pouring, and deterioration of the surface properties of the slab due to this is easily and effectively prevented.

Furthermore, Fig. 6 shows the solidification status of the molten metal and the shape of the slab corresponding to each position indicated by A, A, T, T, O in Fig. 2, and Fig. 6 (A) shows the pouring state. This is the shape of the mold surface (mold cross section).

Since the inner surface of the mold 4 does not have any extreme shape changes in the direction of drawing the slab, similar to those for general continuous casting of thick slabs, the friction between the slab surface and the mold inner surface does not exist. This method does not cause any deterioration in the quality of the mold, and the wear on the mold inner surface does not become severe compared to those for general continuous casting of thick slabs.

The slab immediately after being pulled out of the mold 4 is shown in Figure 6 (a).
As shown in the figure, the slab contains an unsolidified portion inside, but in this state, the slab is compressed in the thickness direction by a liquid lubricated press plate roller. The slab to be compressed contains an unsolidified part inside, and the compressed part is limited to the bulging part at the center in the width direction of the slab, so it can be easily formed using the liquid lubricated press plate 6. In addition, since the plurality of liquid lubricated press plates constitute a pressing curved surface 5 whose facing surface distance is gradually narrowed from the inlet side to the outlet side, the compressive deformation of the bulging portion occurs as the slab moves (pulls out). It is done very smoothly, and the shape of the slab can be adjusted to the specified thickness without any difficulty. Moreover, since a pressure liquid film is formed between the press plate and the slab for forced lubrication, friction between the two is sufficiently prevented, and inconveniences due to friction and wear can be avoided.

By the way, when compressing the completely solidified slab with a liquid lubricated press plate, it is preferable to adjust the shell solidification interface strain in the width direction of the slab and in the casting direction to within 0.3%. This is because by suppressing the shell solidification interface strain to 0.3% or less, internal cracking of the slab can be suppressed as much as possible.

The slab [Fig. 6 (1)] whose shape and thickness have been adjusted by the plurality of liquid-lubricated press plates 6 is then cooled and solidified as it is, and is made into the desired thin slab [Fig. 6 (Fig. 6)]. .

Above, the liquid lubricant press plate 6 is placed directly under the mold 4.
The explanation is based on FIG. 2, in which a thin slab is continuously cast by arranging a The solidification state of the molten metal and the shape of the slab at each position at that time will not change, and the solidification status of the molten metal and the shape of the slab at each position will be as shown in Figure 6 with the same symbols corresponding to the positions A, A, T, and O in Figure 5. It is.

As is clear from the above description, the following effects can be enjoyed by applying the present invention.

(a) Aerated pouring using a normal immersion nozzle can be easily adopted without special modification.

(b) There is virtually no change in the cross section of the slab within the mold, so even if oscillation is applied, there will be little variation in the scene.
Further, no particularly large frictional force is generated between the inner surface of the mold and the surface of the slab.

(c) Compression molding of slabs is carried out with forced lubrication using a liquid-lubricated press plate, so there is no undesirable frictional force that occurs when compression is performed using a vibrating press, reducing drawing resistance and facilitating casting operations. Adequate stabilization is ensured.

(d) Therefore, according to this continuous casting method for thin slabs, it is possible to maintain a stable casting operation similar to the continuous casting of ordinary thick slabs, and the continuously produced slabs have a surface It has a desirable quality with good properties and internal quality.

By the way, when carrying out the present invention, liquid lubrication is required because the thickness of the slab is sequentially formed using a plurality of liquid lubrication press plates that constitute pressing curved surfaces whose opposing surfaces are gradually narrowed from the mold entry side to the mold exit side. The problem is how to evaluate the appropriate shape of the pressing curved surface of the press plate.

Here, the evaluation method for the appropriate shape of the pressed curved surface is summarized as follows.

That is, judging from various experimental data, it is appropriate to calculate the appropriate amount of press with the liquid-lubricated press plate as shown in FIG. 7, taking into account various factors. Here, regarding "solidification shrinkage", the shape of the pressing surface is adjusted to correspond to the amount of solidification shrinkage from point P (see Figure 2) to point Q (see Figure 2), and the solidified shell It is important to maintain conditions that do not generate excessive stress.

Next, the present invention will be explained by examples.

(Example) First, continuous casting equipment is provided with a plurality of liquid lubricant press plates 6 downstream of a mold 4 with open ends as shown in FIG. (shown in the figure), pour the low carbon aluminum killed steel molten metal by pouring with a conventional immersion nozzle, and
The slab immediately after being pulled out of the mold 4 was sequentially compressed using a liquid lubricated press to form a thin slab (thickness: 50 m).

The conditions for continuous casting of thin slabs at this time were as follows.

Mold oscillation: 240cycle/win.

Casting speed [Vc]: 5 m/ll1in.

Liquid lubrication press press surface curvature radius [R] :1660m1゜ Pressing surface width [al: 900 dragons.

Pressure surface length [L]: 800 dragons.

Pressure amount [b]: 25m (per side).

In addition, the solidified shell thickness d at the entry point P in the pressing curved surface casting direction is approximately 4.98 ni, and the solidified shell thickness d at the exit point Q
was 9.42n, and the shell surface temperature difference between point P and point Q was 100°C. Further, the values shown in FIG. 7, which serve as the basis for calculating the appropriate pressing amount, were as follows.

Free solidification shrinkage amount bo: 21.1 mm.

Pressure amount Δb: d −4, where the strain in the width direction is 0.3% or less,
When it was 9811, it was 101.7.

53.7 m when d = 9.42 mn.

Limit pressure amount Δb' that does not cause buckling in the width direction: d = 4
．． 6.2m at 98m.

4, 2 vna when d = 9.42 m.

Pressure amount Δb′ at which distortion in the casting direction is 0.3% or less: d −
When there are 4,98 cranes, there are 205.5 cranes.

When d = 9.42 tribute 1, 103.6 cranes.

Therefore, based on these, the appropriate pressing amount was calculated to be 25.3 mm.

During the period of this test, it was confirmed that the casting operation was carried out extremely smoothly and that a thin slab with very good surface condition and internal quality was obtained.

Separately, a continuous casting test was also carried out under similar conditions using equipment in which a liquid lubricated press was installed at some distance from the mold, and almost the same good results as above were obtained.

Summary of Effects> As explained above, according to the present invention, it is possible to improve the surface texture and improve the surface quality by simply introducing a liquid lubrication press, which does not involve wear of the malt or difficulty in cooling the mold, and which requires a small capacity as an accessory equipment. It is possible to stably and continuously cast thin slabs with excellent internal quality, and it is possible to supply thin slabs with good quality at a low cost, which brings about extremely useful effects industrially.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of a mold with both ends open according to the present invention. FIG. 1(a) is a plan view, and FIG. FIG. 2 is an explanatory diagram of an example of a thin slab continuous casting apparatus according to the present invention. FIG. 3 is an explanatory diagram of a liquid lubrication press apparatus according to the present invention. a) and FIG. 4(b) are schematic diagrams each illustrating another example of the main part of the liquid lubrication press apparatus according to the present invention. FIG. An example is shown. Fig. 6 is a conceptual diagram showing the molten metal solidification situation and slab shape at each part in the apparatus of the present invention, and Fig. 6 (A) to Fig. 6 (Ex) are Each shows the state corresponding to the corresponding part in Fig. 2 or Fig. 5. Fig. 7 is a drawing explaining the appropriate amount of pressing with a liquid lubricant press. FIG. 9 is a schematic diagram showing the dimensions of each part of the continuous thin slab casting apparatus. FIG. 9 is a schematic diagram illustrating the shape and dimensions of a mold with both ends open in the continuous thin slab casting apparatus used in the example. Figure 10 is an explanatory diagram of a mold applied to the conventional SMS type thin slab continuous casting method. (Respectively different examples of the BB sectional view in al, and the 10th
Figure (C) shows a CC sectional view in Figure 10 (a). In the drawings: 1.21... Long side wall, 2... Short side wall. 3... Immersion nozzle, 4... Both ends open mold. 5... Pressure curved surface. 6... Liquid lubricant press plate 7... Press device, 8... Molten metal. 9... Solidified shell, 10... Support roll 12... Pressure liquid port 13... Drainage groove. 14...Pressure liquid supply path, 15...Drainage path. 16...Liquid supply piping. 22...Pouring part. 23... Transition surface.

Claims (3)

[Claims] (1) The dimensions of both short walls sandwiched between the long walls are substantially the same as the desired thin slab thickness, and the opposing inner surfaces at the center of the long walls enable the use of an immersion nozzle. Between the two bulging surfaces of the slab formed at the center of the long side wall of the mold, the slab is pulled out from the mold with both ends open and the cross section receded by the amount of A plurality of liquid lubricant press plates forming a pressing curved surface whose distance is gradually narrowed from the inlet side to the outlet side are arranged, and the remaining unsolidified slab pulled out from the mold is transferred to the plurality of liquid lubricant press plates. A continuous casting method for thin slabs, which is characterized by compressing them in the thickness direction from both sides to a predetermined thickness. (2) The dimensions of both short walls sandwiched between the long walls are substantially the same as the desired thin slab thickness, and the opposing inner surfaces at the center of the long walls enable the use of an immersion nozzle. a mold with both ends open in a cross-sectional shape that is recessed by the same amount, and a central portion of the long side wall of the mold located within a range where an unsolidified portion remains in the slab pulled out from the mold with both ends open. A thin cast slab formed by a plurality of liquid lubricated press plates forming a pressing curved surface that gradually narrows the distance between both bulging surfaces of the cast slab from the inlet side to the outlet side. Continuous casting equipment. (3) Consisting of a plurality of press plates facing the surface of the slab pulled out from the mold and a press device that supports them, the press plate has a pressure liquid port and a drainage liquid concave in the surface facing the slab. A pressure liquid supply device is communicated with the pressure liquid port via a pressure liquid supply passage passing through the press plate, and a liquid drainage passage passing through the press plate is communicated with the liquid drainage groove. A liquid lubrication press device for continuous casting slab forming, characterized by: