JPH03142045A - Method and apparatus for continuously casting metal strip - Google Patents

Abstract

PURPOSE:To prevent breakout of unsolidified molten metal from plate sides by making the thickness at both edge parts in a case strip less than the thickness at the center part in a twin roll type continuous casting apparatus. CONSTITUTION:A pouring basin part 2 is formed by setting one pair of inside cooling rolls 1a, 1b mutually rotating in reverse directions as facing under paralleling the shafts and setting one pair of side dams 3a, 3b on circular surfaces of the roll pair. In this pouring basin part 2, the molten metal is continuously supplied and cooled on the circular surfaces of rolls and the solidified shells are formed, and clad and rolled at the most approached position 4 to form the strip 5. Then, the rolls 1a, 1b having the diameter at both edge parts 10a, 10b larger than the diameter of center parts 9a, 9b are used so as to make the thickness of the side edge parts 7a, 7b in the strip 5 less than the thickness of the center part 6. By this method, even if the unsolidified structure exists at the center part 6 in the strip, flowing out from the edge part is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in a twin-roll continuous casting method and apparatus for continuous casting of thin plates directly from molten metal.

[Background technology]

A pair of internal cooling rolls that rotate in opposite directions are arranged facing each other with their axes parallel to each other, and a pair of side dams for forming a pool on the circumferential surface of the rolls are installed over part or all of their thickness. is placed on both sides of the roll pair so that the molten metal is located on the circumferential surface of the rolls, and continuously casts the molten metal supplied into the pool into a thin plate through the gap between the roll pairs. It is known that the body shape (circumferential surface shape) of the internal four-roll roll used in such twin-roll continuous thin plate casting equipment has approximately the same diameter over the entire length of the roll in contact with the molten metal. They were either flat (right cylindrical) or had an inverted crown shape to take into account swelling caused by the heat of the rolls.

Generally, when continuously casting a thin plate from 78 mm using such a twin roll method, the solidified shell formed on both circumferential surfaces of the r:1-ru pair is rolled at the narrowest gap between the roll pairs. However, it is known that when the rolling load by the rolls is high, significant uneven cooling occurs in the cast plate. Therefore, in order to suppress the occurrence of uneven cooling, it is necessary to bring the rolling load as close to zero as possible. However, if the rolling load approaches zero, there is a high possibility that the plate will be finned from the rolls with unsolidified molten metal remaining in the center of the plate thickness, and
ij? Ik sticks out. A so-called side break occurs.

The shape of the edge of the plate will also be poor. Further, depending on the type of molten metal to be cast, a molten metal is likely to form between the bottom of the side dam and the roll, and this molten metal can cause problems such as damage to the end of the side dam and breakage of the side of the plate.

Therefore, in casting using the twin roll method, it is extremely important to appropriately control the rolling load.

[Problems to be solved by the invention] As mentioned above, controlling the rolling load is important in twin roll continuous casting machines, but it is actually not easy to do this properly, and the rolling load is high. In addition to the problem of uneven cooling as mentioned above, if the amount of reduction of the solid shell increases, the pressure that the solidified shell tends to protrude toward the inside of the machine increases, causing damage to the side dam, and also increases the rolling load. If there is a small amount, the unsolidified molten metal may break from the temporary side as described above.

The present invention aims to solve the above-mentioned basic problems in twin-roll continuous casting machines.

[Means for Solving the Problems] The gist of the present invention is to achieve the above object by arranging a pair of internal cooling rolls that rotate in opposite directions and facing each other with their axes parallel to each other. The molten metal supplied onto the circumferential surface of the pair of rolls passes through the gap between the pair of rolls,
A thin plate continuous casting method for continuously casting a Ti4 plate is characterized in that the thickness of both ends of the thin plate to be cast is made thinner than the thickness of the central part of the thin plate.

According to the present invention, as a device for implementing this, a pair of internal cooling rolls rotating in opposite directions are arranged facing each other with their axes parallel to each other, and a pool is formed on the circumferential surface of the rolls of this pair of rolls. A pair of side dams are arranged on both sides of the roll pair so that part or all of their thickness is located on the roll circumferential surface, and the molten metal supplied into this pool is placed in the gap between the roll pair. In a thin plate continuous casting device that continuously casts thin sheets through a process of continuous casting, one or both of the circumferential surfaces of the pair of rolls is composed of a central portion having the same diameter and both side portions having a diameter larger than that of the central portion. Provided is a thin plate continuous casting device characterized by: At that time, the central part with the same diameter and the both sides with a larger diameter are connected via an enlarged diameter part (tapered part) that continuously increases in diameter from the central part to both sides. Good. Further, the side dam is installed so that its bottom is in contact with both sides of the large diameter of the roll pair, and more preferably has a thickness sufficient to cover the enlarged diameter part (tapered part) of the roll pair, and has an inner surface. As it approaches the closest position between the rolls, it is tilted in the direction of outward spread.

[Effect]

In the present invention, the width of the thin plate to be cast is such that the center portion, which accounts for most of the width, has the intended normal thickness, and only a small portion at both ends is thin. In other words, when the solidified shell formed on the circumferential surface of the twin rolls is pressure-rolled between the roll gaps, the roll gap is made narrower at both ends of the thin sheet for casting. The solidified shells butt against each other more quickly, and due to the presence of the butted portions at both ends, even if the central part of the plate width is unsolidified, the unsolidified molten metal will not flow out from both ends. The equipment can be operated safely even under casting conditions where molten metal is contained in the center of the thin plate.

In addition, according to the device configuration of the present invention, the circumferential surface of the twin rolls forming the bottom of the pool has a diameter larger at both ends of the roll than at the center. The narrow roll gap that is formed prevents the molten metal from flowing out in the unlikely event that the bottom of the side dam is damaged (generally, side dams are prone to damage at the part corresponding to the closest position between the rolls). It also acts as a dam.

The molten metal flowing into this area rapidly solidifies in the narrow gap.

[Description of preferred embodiments of the invention]

FIG. 1 schematically shows the main parts of a preferred twin-roll continuous casting apparatus according to the present invention.

a pair of internal cooling rolls la rotating in opposite directions;
lb are arranged facing each other with their axes parallel to each other, and a pair of side dams 3a and 3b for forming a pool 2 on the circumferential surface of the rolls of this pair of rolls are located with their entire thickness on the circumferential surface of the rolls. They are arranged on both sides of the roll pair.

Molten metal is continuously supplied into the tundish basin 2 by means not shown.

The molten metal in the pool 2 is cooled by the circumferential surface of the internal cooling rolls la, lb, and forms a solidified shell in contact with the circumferential surface, which is pressed and rolled together at the closest position 4 between the rolls la and lb. A thin plate 5 is manufactured. Furthermore, side dam 3a
, 3b is the entire thickness of the roll la, as shown in the figure.
It does not have to be located on the circumferential surface of the roll lb. For example, the other part of the thickness may protrude outside the circumferential surface of the roll la, lb, and the remaining part may be installed on the circumferential surface. .

In the present invention, in such a twin-roll continuous casting machine, the thin plate 5 to be cast is formed in a temporary center having the originally intended thickness as shown in the cross-sectional view taken in the width direction of the plate in FIG. part 6
In the example shown in the figure, the cross-sectional shape is formed by casting and plate-side end portions 7a and 7b having a thickness thinner than this.
The plate side edges 7a, 7b are both reduced by the same thickness from both sides of the plate central portion 6, and therefore have symmetrical cross-sectional shapes with respect to the plate thickness center plane 8, and the plate side edges The portions 7a and 7b have a symmetrical shape also with respect to the center plane of the plate width. Such a cross-sectional shape can be obtained by using the twin rolls la and lb having substantially the same circumferential surface shape in the apparatus shown in FIG. This example will be explained below with reference to the drawings, but if the plate side edges 7a and 7b can be reduced in thickness better than the plate center part 6, the cross-sectional shape will be the plate thickness center plane or the plate thickness. It does not necessarily have to be symmetrical with respect to the width center plane.

In the present invention, one or both circumferential surfaces of the rolls la and lb (both circumferential surfaces in the case of rolling) are used as an apparatus for casting a temporary film 5 whose plate side ends 7a and 7b have a thin plate thickness.

As shown in FIG.
Both sides 10a and 1 have a diameter larger than that of a and 9b.
0b is used. The central portions 9a and 9b occupy most of the width of the thin plate 5, and have the same diameter within this range. both sides 10a having a large diameter;
10b also has the same diameter within its narrow width and is internally cooled like the central parts 9a, 9b except for its outermost ends. In FIG. 1, the side dams 3a and 3b are raised such that their bottom surfaces are in sliding contact with the large-diameter side portions 10a and 1Ob.

Figure 3 is a plan view of the device in Figure 1.
As seen in this figure, the side dam 3a.

3b has a thickness within the width of both side parts 10a and 10b and stands up thereon, and a solidified shell formed by the circumferential surfaces of rolls la and Ib forms the closest gap 12 between central parts 9a and 9b. is cast into a shape corresponding to the temporary central portion 6 shown in FIG. 2, and both side portions 10a
The closest gaps 13a, 13b between and 10b are similarly cast in a shape corresponding to the plate side ends 7a, 7b.

At that time, the solidified shell formed by the circumferential surfaces of the rolls la and lb is formed at the plate side end 7 which passes through the narrow roll gap.
a, 7b are brought together earlier and more completely than in the machine center section 6. In FIG. 2, these abutting portions are indicated by 14a and 14b. Therefore, even if there is an unsolidified weave (indicated by 15 in FIG. 2) in the central part of the plate when it leaves the roll gap,
This unsolidified molten metal is prevented from flowing out from the plate end side.

FIG. 4 shows enlarged diameter portions 17a and 17b (tapered portions) that continuously increase in diameter from the center toward both sides between the center portions 9a and 9b of rolls la and lb and both side portions 10a and Job. This shows the same device as the previous example, except for the addition of . In other words, in the previous example, there was a step with a surface perpendicular to the roll axis by the difference in diameter between the center and both sides, but in this example, the step is a gradual step that gradually expands in diameter toward both sides. As a result, the thin plate to be cast also has a tapered portion where the thickness gradually decreases from the center of the plate toward the edge of the plate. The presence of these enlarged diameter portions 17a and 17b can prevent temporary cracking caused by steps. In other words, depending on the type of metal or alloy to be cast or the casting conditions, a molten metal may be formed between the side dam and the roll. In particular, the lower end of the side dam near the closest point between the rolls is likely to be damaged.To prevent this, the steps are made higher and the diameters of both sides 10a and lobs are increased, thereby reducing the thickness of the plate end. It is effective to make it even thinner. In this case, the solidified shells abut against each other at the plate ends more quickly, and unsolidified molten metal is more likely to remain in the center.

Therefore, heat recuperation occurs after the sheet leaves the rolls, and the surface temperature of the sheet increases, making the sheet brittle and prone to cracks. In addition, if the zero level difference, which is likely to cause porosity at the center of the plate thickness, is provided through a surface perpendicular to the roll axis as in the previous example, the temperature difference between the edge and center of the plate due to recuperation will become large. Since the difference in the amount of thermal contraction becomes large, thermal stress concentrates at the boundary between the end and the center, which tends to cause plate cracking. However, if a gentle slope is formed by the enlarged diameter parts 17a and 17b as in this example, the stress will be reduced. Since concentration can be avoided, temporary cracking caused by reheating can be prevented.

FIG. 5 shows an example of arranging side dams 3a and 3b for the roll shown in FIG. 4 which has enlarged diameter portions 17a and 17b.
3b, the thickness of both side parts 10a, 10b and the enlarged diameter part 17a, 1
The thickness includes 7b.

FIG. 6 is a schematic view showing the inner surfaces of the side dams 3a and 3b shown in FIG. 5, cut along the plate surface during casting. Side dams 3a, 3 as shown
On the inner surface of b, inclined inner surfaces 18a and 18b are formed in a direction that gradually widens outward as the position closest to the roll is approached. In other words, the thickness of the side dams 3a, 3b which dam up substantially all of the molten metal in one molten metal pool 2 is equal to the thickness of the side dams 10a, 1
0b and the enlarged diameter portions 17a, 17b, but at the closest position, inclined inner surfaces 18a, 18b are formed to reduce the thickness from the inside.

And the lower ends 19a, 19 of the side dams 3a, 3b
b extends to the position closest to both sides 10a, 10b, and is inside the lower ends I9a, 19b @ 20a, 20
b (lower edges of the inclined inner surfaces 18a, 18b) are located near the boundaries between the both side portions 10a, IOb and the enlarged diameter portions 17a, 17b in the illustrated example. As a result, the enlarged diameter portion 17a,
Most of the width of 17b is the side dam 3 at its closest position.
This means that it does not come into contact with the bottom surfaces of a and 3b.

However, the larger diameter portions 17a, 17b come into contact with the bottoms of the side dams 3a, 3b more and more as they move away from the closest position (as they move away from the inside of the pool 2).

Eventually, the entire radius will come into contact with the bottoms of the side dams 3a, 3b. By using such side dams 3a, 3b, the solidified shell formed on the surface of the enlarged diameter portions 17a, 17b becomes thinner outwardly when it passes through the closest position. Therefore, when the solidified shells are butted against each other, the force that presses the side dams 3a, 3b outward is relaxed, and damage to the lower edge portions of the side dams 3a, 3b is suppressed.

In addition, in FIG. 6, the positions of the inner lower ends 20a, 20b of the side dams 3a, 3b are in the enlarged diameter portion 17a in addition to the example in FIG.

It may be slightly inserted into 17b, or it may be slightly inside than in Figure 1.

Examples of operation of the apparatus of the present invention carried out by the present inventors are given below.

(1) The diameter of the center of the roll is 400mm. Using a roll with a diameter of 400.5 mm in the area 30 mm from the end of the roll and a roll width of 300II11, molten metal 1 of 5US304 was prepared.
A 20 kg casting was carried out. The side dam was installed by bringing the bottom of the side dam into contact with the circumferential surface of the roll in an area 20 mm from the end of the roll. The roll gap is 2. On+m, 1 at the end. ．． It was set to 75 mm. During casting, the rolling load was gradually lowered until almost no uneven cooling was observed, but no leakage occurred from the temporary side dam, and we were able to continuously obtain cast plates with good plate edge shapes. .

(2) Using a roll with a diameter of 400 mm at the center of the roll, a diameter of 402 mm in a region 20 mm from the end of the roll, and a roll width of 300 + 1 m with a tapered part in the range of 10 a + m between the center and end of the roll. Then, 120 kg of molten Inconel 600 was cast. The method for installing the side dam is to bring the bottom of the side dam into contact with the closest point of the roll within a range of 20 mm from the end of the roll.

In addition, in the tapered part, the bottom of the side dam is brought into contact with a height of 60 m+m above the point closest to the roll at the point closest to the roll end (point A in Figure 6), and 140 meters above the point closest to the roll at the point closest to the center of the roll. The bottoms of the side dams were brought into contact up to a height of - (point at the mouth in Figure 6), and the length of contact between the molten metal (solid shell a) and the rolls at the tapered part was made shorter as the gap between the rolls became narrower. The roll gap is
2.0mm at the center of the roll, 1.0m at the end of the roll
− is.

During casting, the entire quantity was cast without any problems such as leakage of hot water from the temporary side. The width of the cast plate is the initially set plate width 2.
It had expanded to 2BOn+- for 60mm. This expansion of the plate width is thought to have occurred due to damage to the lower end of the side dam. However, the end shape of the obtained cast plate was good over its entire length.

(3) (Comparison) 5US304 was cast in the same manner as in Example (1) except that a roll having a flat shape with approximately the same diameter over the entire O'-)L/width was used. In order to reduce the uneven cooling that occurs on the surface of the cast plate during casting, the rolling load on the rolls was gradually lowered.

Example (1) Before the level of uneven cooling reached the same level, hot water continued to leak from the side of the board. the result.

A plate with a significantly poor shape at the edge of the plate was obtained. on the other hand.

In the range where the shape of the plate end was good, it was inferior to Example (1) in terms of uneven cooling on the plate surface.

(4) [Comparative Example 3 Using rolls having the same flat shape as in (3), casting experiments of Inconel 600 were conducted with various initial roll gaps. The three side dams were installed in the same manner as in Example (1), in which the bottom of the side dam was brought into contact with the circumferential surface of the roll in an area 201 from the end of the roll. When the initial roll gap was 1.31 or more, molten metal began to leak from the temporary side immediately after casting started, and only a plate with a poor shape at the plate end was obtained. Therefore, the circumferential speed of the rolls during casting was slowed down and the rolling load was increased, but this did not prevent melt leakage from the side of the plate.

The cause of the melt leak was that the lower end of the side dam was damaged, and the molten metal that flowed into this damaged portion did not completely solidify until the plate was separated from the roll. Therefore, in the case of flat rolls, in order to cast an alloy such as Inconel 600, which easily damages the lower end of the side dam, without causing melt leakage from the plate end, the initial roll gap must be set to 1.
Must be 31 or less. On the other hand, if the roll according to the present invention is used as in Example 9 (2), even if the initial roll gap is 1.3 m+m or more, it is possible to continuously obtain plates with good plate end shapes. .

〔effect〕

As described above, according to the present invention, it is possible to prevent unsolidified molten metal from breaking from the side of the plate even if the pressure bonding load is extremely reduced in order to reduce uneven cooling of a plate cast with a twin-roll continuous caster. Furthermore, even if the lower end of the side dam is damaged due to the boiling water, it is possible to prevent the plate side from breaking.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the essential parts of a twin-roll continuous casting apparatus according to the present invention, FIG. A schematic plan view of the device shown in the figure, FIG. 4 is a plan view showing another example of the twin roll of the device of the present invention, and FIG. 5 is a schematic plan view showing an example of the device of the present invention.
FIG. 6 is a schematic cross-sectional view of the device shown in FIG. 5 in a cast state, taken along a plate surface. la, lb...roll, 2...bath 3a,
3b...Side dam, 4...Roll closest position 5...
・Casted plate, 6... Machine center part 7a 7b
...Plate side end, 9a, 9b...Roll center part 1
0a, 10b...Both sides of the roll. 17a, 17b... Roll enlarged diameter portion. 18a, 18b...Slanted inner surface of side dam. Figure 1 0a Figure tJa Figure 6

Claims (5)

[Claims] (1) A pair of internal cooling rolls that rotate in opposite directions are arranged facing each other with their axes parallel to each other, and the molten metal supplied onto the circumferential surface of the rolls is continuously formed into a thin plate through the gap between the pair of rolls. A thin plate continuous casting method for casting a thin plate, characterized in that the thickness of both ends of the thin plate to be cast is made thinner than the thickness of the central part of the thin plate. (2) A pair of internal cooling rolls that rotate in opposite directions are arranged facing each other with their axes parallel to each other, and a pair of side dams with a thickness equal to A continuous thin plate casting device that is disposed on both sides of a pair of rolls so that part or all of the part is located on the circumferential surface of the rolls, and continuously casts molten metal supplied into the pool into a thin plate through the gap between the pair of rolls. Continuous thin sheet casting, characterized in that the circumferential surface of one or both of the pair of rolls is composed of a central portion having the same diameter and both side portions having a diameter larger than the diameter of the central portion. Device. (3) The thin plate continuous casting apparatus according to claim 2, wherein the central portion and both side portions are connected via an enlarged diameter portion (tapered portion) that continuously increases in diameter from the central portion toward both side portions. (4) Claim 2 or 3, wherein the side dam is installed such that its bottom is in contact with both sides of the large diameter of the roll pair.
The thin plate continuous casting apparatus described in . (5) The side dam has a thickness sufficient to cover the enlarged diameter portion of the roll pair, and the inner surface of the side dam is inclined in a direction of expanding outward as it approaches the position closest to the rolls. The thin plate continuous casting apparatus described.