JP2009022971A - Continuous casting method and continuous casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a short-side mold so as to be most suitable for changing casting width in the continuous casting for cast slab having the plurality of cast slab widths by using multi-tapered short-side mold plates, and to provide a continuous casting method and a continuous casting mold, wherein the uniformity of solidification is good and the mold binding force is not increased when casting is performed with the narrow width or the wide width. <P>SOLUTION: The continuous casting method is used for casting the plurality of the cast slabs having the cast slab width by using the multi-tapered short-side mold plates having two or more short-side tapered ratios (unit: %/m) different in the casting direction, wherein the short-side tapered ratio at the uppermost position in the casting direction is defined as an upper tapered ratio, the short-side tapered ratio at the lowermost position is defined as a lower tapered ratio, and a value obtained by dividing the upper tapered ratio by the lower tapered ratio, is defined as an upper/lower tapered ratio, and in the case of any cast slab width during the casting, the upper/lower tapered ratio, is set to be lower than a value (R<SB>M</SB>) obtained by calculating with a prescribed formula. And the continuous casting mold is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a continuous casting method and continuous casting mold for continuously casting molten metal.

  In continuous casting of molten metal such as steel, when molten metal is injected into the mold, the molten metal part in contact with the mold is solidified to form a solidified shell, which is pulled out below the mold, and then cooled secondary below the mold. Solidification proceeds in the band, and a continuous cast slab is finally formed. The mold is formed of a water-cooled copper plate on the side in contact with the molten metal. In a continuous casting apparatus for casting a slab, it has two long-side mold plates and two short-side mold plates, and the width of the short-side mold plate is approximately equal to the thickness of a cast piece to be cast. A continuous casting mold is formed by assembling so that two short-side mold plates are sandwiched by two long-side mold plates.

  In the process of moving the solidified shell downward while solidification of the solidified shell proceeds in the mold, the solidified shell solidifies and contracts as solidification proceeds. Therefore, the solidified shell that has started solidification at the meniscus position of the molten metal in the mold contracts when it reaches the lower end of the mold, and the width and thickness of the slab during solidification are smaller than the meniscus position. . In slab continuous casting, since the width is wider than the thickness of the slab, the amount of solidification shrinkage in the slab width direction is large. If there is a gap between the mold and the solidified shell due to the solidification shrinkage of the solidified shell, heat removal from the solidified shell to the mold is hindered, making it impossible to cool the mold sufficiently, and the solidified shell that has lost its support by the mold Will cause bulging to bulge outward.

  Therefore, a taper is provided at least on the short side of the mold. Providing the taper means that the distance between the lower ends of the mold is reduced with respect to the distance between the opposing short sides with respect to the distance at the meniscus position above the mold.

In the present invention, as shown in FIG. 1C, an upper position and a lower position are defined at arbitrary positions in the casting direction, and the distance between both short sides is set to W ₁ (m) at the upper position and W _{2 at} the lower position. (M) When the distance from the upper position to the lower position is ΔL (m), the taper ratio (% / m) is set to taper ratio (% / m) = {(W ₁ −W ₂ ) / W ₀ / ΔL } × 100 (2)
(Here, W ₀ (m) is the meniscus width (W _M ). W ₀ may be any length determined according to a certain width. Mold upper end width, mold lower end width, etc.)
And call it like this.

  If the short side taper ratio is too small, the contact between the solidified shell and the short side mold plate will be non-uniform, cooling imbalance will occur, the solidified shell growth will be non-uniform, Cracking occurs. In particular, when the short side taper ratio is smaller than an appropriate amount, in the thickness distribution of the solidified shell near the lower end of the mold, a portion with a particularly thin solidified thickness is generated near the corner of the long side solidified shell as shown in FIG. The solidified shell easily breaks at this portion, and breakout may occur. In addition, when the short side taper ratio is too large, the contact between the solidified shell and the short side mold plate becomes strong, excessive stress is applied to the solidified shell, and breakage of the solidified shell and breakout due to shell breakage occur. . Alternatively, the mold life may be reduced due to an increase in frictional force between the solidified shell and the mold.

  Regarding an appropriate short side taper, for example, in Patent Document 1, the short side taper rate βn is set to 0.7 to 1.3% / m.

  The surface (hereinafter also referred to as “taper surface 6”) of the conventional short-side mold plate 2 facing the solidified shell is processed in a plane from the upper part to the lower part as shown in FIG. However, the solidification shrinkage rate of the solidification shell is not constant at each position in the casting direction in the mold, and the solidification shrinkage rate is fast near the meniscus, and the solidification shrinkage rate becomes slower as it approaches the lower end of the mold. Therefore, it is considered that the surface of the solidified shell in contact with the short-side mold plate is not a flat surface but a curved surface whose taper rate decreases as it goes below the mold.

  Patent Document 2 discloses a taper control method for controlling the taper of the mold short side as a curved surface. The short side mold is supported at at least three points on the back surface and deformed. A pressure device is attached to at least one of the three points, for example, the central portion, and the surface of the short side copper plate and the free contraction profile are matched in advance and during operation, so that more uniform heat removal is possible. By applying a force of 2 to 5 tons to the central load point, the maximum amount of deflection becomes 0.33 to 0.83 mm, which is considered to be a sufficient amount in view of the solidification shrinkage of the molten steel.

In Patent Document 3, the optimum short side taper is obtained by theoretical analysis. The optimum short side taper depends on the distance Z along the casting direction from the meniscus, and the optimum taper rate (% / m) at each distance Z is It is assumed to be proportional to Z ^-1/2 . According to Example 1 and FIG. 2 of the same document, the short side of the mold having a cross-sectional dimension of 20.8 cm × 105 cm is formed into a shape having a three-step taper, and the taper rate is 2% / m, 0.7% / m, 0.4% / m. Further, according to Example 2 and FIG. 3, the short side of the mold having a cross-sectional dimension of 22 cm × 124 cm is formed into a shape having a three-step taper, and the taper rate is 4% / m, 1.3% / m,. 8% / m. In this way, a mold having a taper of two stages or three or more stages in the casting direction is called a multistage taper mold, and a short side mold plate having such a taper is called a multistage taper short side mold plate.

  In continuous casting of slabs, cast slabs have various widths for each destination, so that the cast slab width is changed while continuous casting is continued. As shown in FIG. 6, the short-side mold plate 2 has a short-side drive device 4 for moving the short-side mold plate 2 in the long-side direction, and the short-side mold plate 2 is sandwiched between the long-side mold plates 3. By changing the position, the slab width can be changed during casting. That is, cast pieces having various widths can be cast using the same continuous casting mold 1 without exchanging both the long side mold plate 3 and the short side mold plate 2.

  Patent Documents 4 and 5 describe methods for estimating the solidification behavior of a slab in a mold by calculation. When the inclination of the casting direction of the mold or the casting speed is set to an arbitrary value, the thickness of the solidified shell at each part around the mold is calculated. Based on this result, the ratio between the maximum value and the minimum value of the solidified shell thickness at the lower end of the mold, the binding force between the solidified shell and the mold, and the gap amount can be obtained.

Japanese Patent Laid-Open No. 2005-21936 JP-A-2-247059 JP-A-56-53849 JP 2006-346735 A JP 2006-346736 A

  When performing slab continuous casting using slabs of various slab widths using a multi-stage tapered short side mold plate, the cohesive force from the mold is reduced while maintaining good solidification uniformity at any casting width. A method for performing continuous casting that can be performed has not been known.

  The present invention provides an optimum method for controlling a short side mold when changing a casting width in continuous casting in which a slab having a plurality of slab widths is cast using a multistage tapered short side mold plate, and a narrow width. It is an object of the present invention to provide a continuous casting method and a continuous casting mold that have good solidification uniformity and no increase in mold restraining force during both casting and wide casting.

  When performing slab continuous casting for casting slabs of various slab widths, it was unclear how the short side taper should be determined when changing the width. When the width was changed while keeping the short side taper rate (% / m) constant, it was found that the solidification uniformity of the solidified shell deteriorates in narrow casting. In order to improve the solidification uniformity, it is considered useful to use a multistage tapered short side mold plate, and when performing slab continuous casting to cast slabs of various slab widths, a multistage tapered short side mold plate is used. We decided to introduce it.

As an example of using a multistage tapered short side mold plate, a two-stage tapered short side mold plate shown in FIG. 1A is assumed. Of the short side taper ratio, the taper ratio at the upper taper surface 6 _U on the meniscus is the upper taper ratio T _U (% / m), and the taper ratio at the lower taper surface 6 _L on the lower end side of the mold is the lower taper ratio T _L (% / M). As the optimal T _U and T _L in conducting casting was determined, in any of the width of casting I think you can use the same T _U and T _L.

When the slab width is W (m) and the taper rate is T (% / m), the angle θ (radian) between the surface facing the solidified shell of the short side mold plate and the vertical surface is (since θ is small)
θ = TW / 100/2 (3)
Can be written. When the angle corresponding to the upper taper rate T _U is θ _U , the angle corresponding to the lower taper rate T _L is θ _L, and the angle formed by the upper taper surface and the lower taper surface is Δθ,
Δθ = θ _U −θ _L = (T _U −T _L ) W / 100/2 (4)
It becomes. If the casting width W is changed while the upper taper rate T _U and the lower taper rate T _L are kept constant, that is, T _U −T _L is kept constant, Δθ will fluctuate.

When a set of two-step taper short side mold plates is manufactured and used by being incorporated in a mold, Δθ is unique to each two-step taper short side mold plate, and Δθ cannot be changed during casting. Accordingly, in a continuous casting mold which corresponds to the variation of the casting width, unless the exchange short side mold plate, it is the principle impossible to hold the both constant T _U and T _L in each casting width.

  That is, when slab continuous casting of slabs with various slab widths is performed using a continuous casting mold to which a multi-stage tapered short side mold plate is applied, the short side mold is changed under any conditions when changing the casting width. It was unclear whether a suitable taper should be controlled.

The present inventors have found that, in the case of using the multi-stage taper short side mold plate, as shown in FIG. 1 (a) (b), the distance between the short sides, W _M (m) at the meniscus position in the casting mold bottom W _B (m), and the distance from the meniscus position to mold the lower end placed between L (m), the total taper ratio (% / m) of total taper ratio (% / m) = {( W M -W B) / W ₀ / L} × 100 (5)
It is defined as W ₀ (m) may be anywhere as long as it has a fixed length according to a certain width. Meniscus width (W _M (m)), mold upper end width, mold lower end width, etc.

  When performing slab continuous casting of slabs having various slab widths using a continuous casting mold to which a multistage tapered short side mold plate is applied, what taper shape should be selected as the multistage tapered short side mold plate, This is a problem.

The inventors of the present invention divide the upper taper rate T _U by the upper taper rate T _U , the lowest short side taper rate in the casting direction, the lower taper rate T _L , and the upper taper rate T _U by the lower taper rate T _L. It was clarified that the optimum shape of the multi-step taper short side mold plate can be expressed as the range of the vertical taper ratio when the above value is defined as the vertical taper ratio.

That is, the gist of the present invention is as follows.
(1) A continuous casting method for casting a slab having a plurality of slab widths using a multistage tapered short side mold plate having two or more short side taper ratios (unit:% / m) different in the casting direction. ,
The upper taper rate is the uppermost short side taper rate in the casting direction, the lower taper rate is the lowermost taper rate, and the short side taper rate obtained by connecting the meniscus part on the short side surface and the lower end of the mold with a straight line is the total taper rate ( T _T ), and the value obtained by dividing the upper taper rate by the lower taper rate is defined as the vertical taper ratio (R). The vertical taper ratio R is expressed by the following formula (1) at any slab width (W) during casting. A continuous casting method characterized in that the value is equal to or less than the value (R _M ) calculated by
R _M = −3.1 × ln (W × T _T ² ) +29 (1)
(R _M (−), T _T (% / m), W (mm))
(2) The continuous casting method according to (1) above, wherein the minimum slab width to be cast is 500 mm or less.
(3) The continuous casting method as described in (1) or (2) above, wherein the maximum slab width to be cast is 2500 mm or more.
(4) The continuous casting method according to any one of (1) to (3) above, wherein a two-step taper mold having a short side taper rate having only two values of an upper taper rate and a lower taper rate is used. .
(5) Change the long side mold plate, the multi-stage taper short side mold plate having two or more short side taper rates (unit:% / m) different in the casting direction, and the width of the cast slab and the inclination of the short side A short side drive device and a control device for the short side drive device, the upper side taper rate is the uppermost taper rate in the casting direction, the lower side taper rate is the lower taper rate, and the shorter side The short side taper ratio connecting the surface meniscus portion and the mold lower end portion with a straight line is defined as the total taper ratio (T _T ), and the value obtained by dividing the upper taper ratio by the lower taper ratio is defined as the vertical taper ratio (R), The control device of the short side drive device sets the vertical taper ratio R to be equal to or less than the value (R _M ) calculated by the following formula (1) at any slab width (W) during casting except during width change. A continuous casting mold characterized by that.
R _M = −3.1 × ln (W × T _T ² ) +29 (1)
(R _M (−), T _T (% / m), W (mm))
(6) The continuous casting mold according to (5), wherein the minimum castable slab width is 500 mm or less and the maximum castable slab width is 2500 mm or more.

  The present invention provides a continuous casting method for casting a slab having a plurality of slab widths using a multistage tapered short side mold plate, and by adjusting the vertical taper ratio within a certain range at any slab width, Even in the casting width, the solidification uniformity of the solidified shell in the mold can be maintained satisfactorily, and good casting can be performed while reducing the restriction of the solidified shell by the mold.

In the present invention, the total taper rate T _T , the upper taper rate T _U , the lower taper rate T _L , and the vertical taper ratio R are defined as follows.

When the distance between the short sides is W _M (m) at the meniscus position, W _B (m) at the lower end of the mold, and L (m) from the meniscus position to the lower end of the mold (FIGS. 1A and 1B) )), And the total taper rate T _T (% / m) T _T (% / m) = {(W _M −W _B ) / W ₀ / L} × 100 (5)
It is defined as W ₀ may be anywhere as long as it has a fixed length according to a certain width. Meniscus width (W _M ), mold upper end width, mold lower end width, etc.

W in the tapered surface 6 _U on the casting direction at the top of the multistage tapered short side mold plate, optionally define the upper and lower positions, the distance between the short sides, in W ₁ (m), the lower position at the upper position ₂ (m), when the distance from the upper position to the lower position is ΔL (m) (FIGS. 1A and 1B), the upper taper ratio T _U (% / m) is set to T _U (% / m) = {(W ₁ −W ₂ ) / W ₀ / ΔL} × 100 (6)
It is defined as

On the lower taper surface 6 _{L at} the bottom in the casting direction of the multi-stage tapered short side mold plate, an upper position and a lower position are arbitrarily determined, and the distance between both short sides is set to W ₃ (m) at the upper position and W at the lower position. ₄ (m), when the distance from the upper position to the lower position is ΔL (m) (FIGS. 1A and 1B), the lower taper rate T _L (% / m) is set to T _L (% / m) = {(W ₃ −W ₄ ) / W ₀ / ΔL} × 100 (7)
It is defined as

The vertical taper ratio R is
Vertical taper ratio R = Upper taper ratio / Lower taper ratio = T _U / T _L (8)
It is defined as

  Patent Documents 4 and 5 describe methods for estimating the solidification behavior of a slab in a mold by calculation. When the inclination of the casting direction of the mold or the casting speed is set to an arbitrary value, the thickness of the solidified shell at each part around the mold is calculated as shown in FIG. Based on this result, the ratio B / A between the maximum value A and the minimum value B of the solidified shell thickness at the lower end of the mold, the binding force between the solidified shell and the mold, and the gap amount can be obtained.

  Using the calculation methods described in Patent Documents 4 and 5 above, the shape of the solidified shell at the lower end of the mold and the binding force between the solidified shell and the mold were determined for continuous casting using a multistage tapered short side mold plate. The shape of the solidified shell at the lower end of the mold is derived as shown in FIG. 7 by calculation. A portion with a thin solidified shell thickness may be formed on the long side of the solidified shell in the vicinity of the slab corner, and the solidified shell thickness at this portion can be set to the minimum value B of the shell thickness. The ratio B / A between the maximum value A and the minimum value B of the solidified shell thickness is referred to herein as “solidification uniformity”. When casting with good solidification uniformity is performed, the shell thickness of the portion where the shell thickness is thin on the long side near the corner approaches the shell thickness of other thick portions.

  Actually casting the molten steel, adding S to the molten steel in the mold during casting, and evaluating the thickness distribution of the solidified shell at the lower end position of the mold by sulfur printing of the slab after solidification. It was found that the uniformity was in good agreement with the maximum and minimum ratios of the mold bottom solidified shell thickness obtained from sulfur printing. Therefore, it is possible to find a suitable continuous casting method using the solidification uniformity obtained by calculation as an index.

  If the value of solidification uniformity (B / A) obtained by calculation is 0.7 or more, good solidification uniformity can be ensured even in actual casting. If the restraint force obtained by calculation is 2.0 or less (value normalized by the reference value at each width), good casting with less restraint can be performed even in actual casting.

  As shown in FIG. 1, the shape of the two-step tapered short side mold plate 2 will be examined. For the taper surface 6 facing the solidified shell of the short side mold plate 2, the distance from the upper end of the mold at the two-stage change point position is Y, the line extending from the lower taper to the upper end of the mold, and the upper taper at the upper end of the mold If the difference is set to X, the surface shape of the two-step tapered short side mold plate can be determined by determining the values of X and Y.

  Assuming a two-step tapered short side mold plate 2, the X value in FIG. 1 is changed several times, the total taper ratio is in the range of 1.0 to 2.0% / m, and the casting width is in the range of 800 to 2200 mm. The width was changed, and the solidification uniformity and the binding force were calculated by the calculation methods described in Patent Documents 4 and 5. The slab thickness was 240 mm. FIG. 2 shows the total taper ratios of 1.0% / m (♦) and 1.6% / 1.6% for the casting width (a) 800 mm, (b) 1100 mm, (c) 1500 mm, and (d) 2200 mm, respectively. The calculation results of the frictional restraining force when the vertical taper ratio is changed with two types of m (●) are shown. The frictional constraint force is a value obtained by normalizing the calculated constraint force with a reference value for each width (restraint force when the taper rate is 1.0% / m with a one-step taper). The limit value of the frictional restraining force that has been found by the inventors' separate investigation is 2.0. From FIG. 2, it is possible to obtain the relationship between the vertical taper ratio and the total taper ratio at which the frictional restraining force reaches a limit of 2.0 at each casting width. Therefore, FIG. 3 shows a line in which the limit value of the frictional restraining force is 2.0 and the vertical taper ratio is constant, plotted on the horizontal axis-width, vertical axis-total taper ratio graph. . For example, in FIG. 3, taking a case where the width is 1000 mm and the total taper ratio is 1.3% / m as an example, if the vertical taper ratio is about 6.0 or less, the binding force is 2.0 or less. When the vertical taper ratio exceeds 6.0, the restraining force exceeds 2.0. If the total taper ratio is 1.52% / m with the same width of 1000 mm, the constraining force exceeds 2.0 when the vertical taper ratio exceeds about 5.0.

From the graph of FIG. 3, the following formula (1) is obtained by formulating the limit vertical taper ratio (R _M ) by the width W and the total taper ratio T _T.
R _M = −3.1 × ln (W × T _T ² ) +29 (1)
(R _M (−), T _T (% / m), W (mm))

  From the above calculation results, the following two points of correlation were newly found.

  First, when the total taper ratio is constant, the critical taper ratio becomes smaller as the width increases. That is, when the taper amount is defined as follows, if the total taper ratio is constant, the taper amount becomes larger when the width is larger than when the width is narrow, and the absolute value of the contact amount with the solidified shell becomes larger. This is thought to be because it becomes easier to restrain due to the strong taper of the upper part (upper and lower taper ratio).

  Second, when the width is constant, the upper and lower taper ratio becomes smaller as the total taper ratio becomes larger. That is, as the total taper ratio increases, the taper amount increases, and the absolute value of the contact amount with the solidified shell increases, so that it is likely to be restrained for the same reason as the first.

By the way, the taper amount is
Taper amount (m) = T _T (% / m) × W ₀ (m) × L (m)
It is defined as

  FIG. 4 shows a vertical taper ratio, frictional restraint force, solidification uniformity when the width is changed by using a two-step taper short side mold plate having a constant taper shape, for example, the total taper rate is fixed at 1.2% / m. Shows the situation. As shown in FIG. 4, when the width is changed while keeping the total taper rate constant, the vertical taper ratio changes with the casting width, and the vertical taper ratio increases as the casting width decreases. And it turned out that a solidification uniformity and a restraint force change with a favorable value in the range of casting width 800-2200mm. That is, when performing continuous casting while changing the casting width using a multi-stage tapered short side mold plate, the above-mentioned upper and lower taper ratio is set to a limit value or less even in the method of changing the width while keeping the total taper rate constant. It was found that both the solidification uniformity and the restraint force can be maintained well.

  Incidentally, it has also been confirmed that even when the total taper rate is 0.5 to 2.0% / m, the same tendency as in FIG. 4 is exhibited.

  Next, using a two-step taper short side mold plate having a width of 1500 mm, a total taper ratio of 2.0% / m, and a vertical taper ratio of 2.0, the casting width is fixed at 1500 mm, and the total taper ratio is changed. Solidification uniformity and restraint force were calculated. The slab thickness was 240 mm. The results are shown in FIG. As is apparent from the figure, solidification uniformity can be maintained well if the total taper ratio is 0.5 or more. Further, if the total taper rate is 2.0% / m or less, the restraining force is small, and it can be held well.

  In addition, since the solidification uniformity can be improved as the lower limit value of the total taper ratio is larger, 1.0% / m or more is preferable, and more than 1.3% / m is more preferable. More preferably, it is 1.35% / m or more.

  It is also effective to change the total taper rate according to the width. With the same total taper ratio, the frictional restraining force is smaller when the width is narrow. In addition, since the solidification uniformity is the same when the total taper ratio is the same, it is also effective to increase the total taper ratio as the width is narrow because the width is narrow.

  In the present invention, the cast slab thickness is preferably 220 mm or more and 350 mm or less. More preferably, it is more than 230 mm and 350 mm or less, and still more preferably 240 mm or more and 350 mm or less. When the slab thickness exceeds 350 mm, an excessive facility is required as a continuous casting mold for changing the width during casting, which is substantially difficult to realize. Also, if the casting thickness is less than 220 mm, the diameter of the immersion nozzle for injecting molten metal from the tundish must be reduced, or if a large nozzle is used, the gap with the mold becomes small and uniform. Injection of molten metal is somewhat difficult. When the casting thickness exceeds 230 mm, uniform injection becomes easy, and when the casting thickness exceeds 240 mm, uniform injection becomes even easier.

  A continuous casting mold for realizing the casting method of the present invention will be described with reference to FIG.

  The continuous casting mold 1 of the present invention includes a long side mold plate 3, a multistage tapered short side mold plate 2 having two or more short side taper ratios (unit:% / m) different in the casting direction, and a cast piece to be cast. It has a short side driving device 4 capable of changing the width and the inclination of the short side, and a control device 5 for the short side driving device. The upper taper rate is the uppermost short side taper rate in the casting direction, the lower taper rate is the lowermost taper rate, and the short side taper rate obtained by connecting the meniscus part of the short side surface and the mold bottom is a total taper rate. The value obtained by dividing the upper taper rate by the lower taper rate is defined as the upper and lower taper ratio, which is the same as in the continuous casting method of the present invention.

  The control device 5 of the short side drive device can drive and control the short side mold plate so that the vertical taper ratio is not more than a predetermined value at any slab width during casting. This makes it possible to carry out the continuous casting method of the present invention in which the vertical taper ratio is not more than a predetermined value at any slab width.

  The long-side mold plate 3 and the short-side mold plate 2 are each composed of a pair, and the side facing the solidified shell is preferably a water-cooled copper plate, and the opposite surface is a steel back frame. The width of the short side mold plate 2 is substantially equal to the thickness of the cast piece to be cast. By sandwiching the short side mold plate 2 between the two long side mold plates 3, a mold having a rectangular casting space is formed.

  The short-side drive device 4 has, for example, two upper and lower drive actuators 9 and holds the short-side mold plate 2 by the actuator 9 from the back frame side. By determining the position of the short-side mold plate by the movement of the upper and lower actuators 9, the total taper ratio of the short-side mold plate 2 can be set to a predetermined value for each casting width. As the actuator 9, an electric cylinder, a hydraulic cylinder, or the like can be used. Or it is good also as an apparatus which has a drive means which performs a reciprocating motion and a swing motion of a short side mold plate as a short side drive device.

  In addition, when changing the casting width during continuous casting, it is required to continuously change the casting width while performing normal casting. During such a width change, it is necessary to change the total taper ratio to change the width smoothly, and the vertical taper ratio cannot be kept below a predetermined value.

  Since the continuous casting mold of the present invention has a minimum castable slab width of 500 mm or less and a maximum castable slab width of 2500 mm or more, a slab having a wide range can be cast. preferable.

It is a figure explaining the taper surface of a short side mold plate, (a) is a 2 step taper short side mold plate, (b) is a 3 step taper short side mold plate, (c) is a 1 step taper short side mold plate. FIG. It is a graph about the frictional restraining force when changing a total taper rate and an up-and-down taper rate, (a) is 800 mm and (b) is 1100 mm. It is a graph about the friction restraint force when changing a total taper rate and an up-and-down taper rate, (c) is 1500 mm, (d) is 2200 mm. It is a figure which shows the relationship between a width | variety, a total taper rate, and a limit vertical taper ratio. It is a figure which shows the change of the up-and-down taper ratio for every width | variety when the total taper rate is made constant, a solidification uniformity, and a restraint force. It is a figure which shows the relationship between a total taper rate, the solidification uniformity, and a restraint force. It is a figure which shows the continuous casting mold of this invention, (a) is a top view, (b) is a cross-sectional front view. It is a figure which shows the solidification shell shape in the casting_mold | template lower end calculated | required.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting mold 2 Short side mold plate 3 Long side mold plate 4 Short side drive device 5 Control device 6 Tapered surface 9 Actuator 10 Solidified shell 11 Meniscus position

Claims (6)

A continuous casting method for casting a slab having a plurality of slab widths using a multi-stage tapered short side mold plate having two or more short side taper ratios different in the casting direction (unit:% / m),
The upper taper rate is the uppermost short side taper rate in the casting direction, the lower taper rate is the lowermost taper rate, and the short side taper rate obtained by connecting the meniscus part on the short side surface and the lower end of the mold with a straight line is the total taper rate ( T _T ), and the value obtained by dividing the upper taper rate by the lower taper rate is defined as the vertical taper ratio (R),
A continuous casting method characterized in that the vertical taper ratio R is equal to or less than the value (R _M ) calculated by the following formula (1) at any slab width (W) during casting.
R _M = −3.1 × ln (W × T _T ² ) +29 (1)
(R _M (−), T _T (% / m), W (mm))   2. The continuous casting method according to claim 1, wherein a minimum slab width to be cast is 500 mm or less.   The continuous casting method according to claim 1 or 2, wherein the maximum slab width to be cast is 2500 mm or more.   The continuous casting method according to any one of claims 1 to 3, wherein a two-step taper mold having a short side taper ratio having only two values of an upper taper ratio and a lower taper ratio is used. A long-side mold plate, a multi-stage tapered short-side mold plate having two or more short-side taper ratios different in the casting direction (unit:% / m), and changing the width of the cast slab and the inclination of the short side A short side drive device that can be used, and a control device for the short side drive device,
The upper taper rate is the uppermost short side taper rate in the casting direction, the lower taper rate is the lowermost taper rate, and the short side taper rate obtained by connecting the meniscus part on the short side surface and the lower end of the mold with a straight line is the total taper rate ( T _T ), and the value obtained by dividing the upper taper rate by the lower taper rate is defined as the vertical taper ratio (R),
The control device of the short side drive device has a vertical taper ratio R equal to or less than a value (R _M ) calculated by the following formula (1) at any slab width (W) during casting except during width change. A continuous casting mold characterized by:
R _M = −3.1 × ln (W × T _T ² ) +29 (1)
(R _M (−), T _T (% / m), W (mm))   6. The continuous casting mold according to claim 5, wherein the minimum castable slab width is 500 mm or less, and the maximum castable slab width is 2500 mm or more.

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