JP2001079650A - Mold for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the rhombic deformation of a cast slab and to cast the cast slab having high quality without developing the defect in the internal part and on the outer surface by forming the cross sectional shape of a mold as a round corner square shape obtained by connecting the straight line sides and one-forth circular arcs, and making the radius of one-forth circular arcs and the inner circular length of the round corner square shape to be the largest at the upper end side and to be the smallest at the lower end side. SOLUTION: The mold 1 is divided with the equal intervals and the cross sectional shapes are made to the round corner square shapes L0, L1, L2, L3, Ln in order from the lower part. The one-forth circular arcs in the round corner square shapes L0, L1, L2, L3, Ln are made to (R0), (R1), (R2), (R3), (Rn). This round corner square shape has the shape satisfying the relation of R0<R1<R2< R3<Rn and the inner circular lengths of the round corner square shapes L0, L1, L2, L3, Ln are made to be the largest at the upper end side and to be the smallest at the lower end side. The changing ratio of the inner circular length of the round corner square shapes L0, L1, L2, L3, Ln, is desirable to be set with both of the tapered rate of the straight line sides and the changing ratio of the radiuses of the one-forth circular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuous casting mold.

[0002]

2. Description of the Related Art FIG. 6 is a schematic longitudinal sectional view of a conventional continuous casting mold, wherein (101) is a single taper mold, (102) is a two-stage taper mold, and (103) is a parabolic taper. Shows the template. As shown in the figure, conventionally, a continuous casting mold for continuously casting steel is roughly divided into a single-tapered mold 101, and a multi-stage in which the amount of taper is changed at each stage by dividing the mold into a plurality of stages in the casting direction. Tapered molds (a two-stage taper mold 102, a parabolic taper mold 103, etc.) are known.

FIG. 7 is a plan view of a conventional continuous casting mold. As shown in FIGS. 6 and 7, the cross-sectional shape of the conventional continuous casting mold is a rounded rectangle in which four straight sides are connected by four quarter arcs. In addition, the conventional continuous casting mold, regardless of whether it is a single-tapered mold 101 or a multi-tapered mold 102, 103, is formed of a quarter arc that forms a rounded square having a cross-sectional shape. The radius is always constant, no matter what height the mold cuts. And since the volume of the cast slab decreases when cooled, the length of the straight side of the rounded rectangle which is the cross-sectional shape of the mold is large at the upper end of the mold and smaller at the lower end, and the taper of the straight side is The amount is negative. The taper amount of the straight side is a change amount in which the length of the straight side changes with respect to a fixed height change amount.

[0004]

However, as described above, the radius of a quarter arc forming a rounded square which is a cross-sectional shape of a conventional continuous casting mold is determined at any height of the mold. Even so, it is always constant. For this reason, the amount of change in the inner circumference of the cross section of the mold with respect to the amount of change in the constant height (hereinafter referred to as the amount of change in the inner circumference) is only the amount of taper of the straight sides forming the rounded rectangle. It is subordinate to.
Therefore, the conventional continuous casting molds having a single taper or a multi-stage taper have the following problems (1) and (2), respectively.

(1) Problems in the case of a single taper in which the radius of a quarter arc is always constant In the process of solidifying a slab in a mold, the difference between the taper inside the mold and the shrinkage of the slab, or the mold Slab outer wall due to thermal expansion,
An air gap is created between the inner surfaces of the mold. The air gap causes uneven cooling, resulting in rhombic deformation of the slab and internal / external defects (cracks, etc.). These defects can be a factor in lowering the productivity of the lower process. There is a problem that the casting speed cannot be improved with the defects.

(2) Problems in the case of a multi-stage taper in which the radius of a quarter arc is always constant. As described in the above (1), in order to reduce defects in a slab,
It is necessary to suppress the generation of an air gap between the inner surface of the mold and the slab. Therefore, in order to match the shrinkage of the slab, a multi-stage taper having a structure in which the amount of taper on the upper straight side is increased and the amount of taper on the lower straight side is reduced has been devised and used. In the case of a multi-stage taper mold, if the amount of taper on the straight side is increased, the air gap surely decreases and defects in the slab can be reduced. However, if the taper amount of the straight side is increased, it becomes difficult to pull out the slab, and a hiccup phenomenon occurs. In an extreme case, the slab is torn. Normally, in the case of a rounded square mold with 130 to 150 [mm] square, the taper amount of the straight side is 0.9 to 1.
If it exceeds 2 [% / m], there is a problem that the slab is crushed or the slab is torn. Further, when it is 0.9 [% / m] or less, there is a problem that the air gap does not decrease and a slab defect occurs as described above.

In view of such circumstances, the present invention prevents high-speed casting of high-quality slabs having no defects on the inner and outer surfaces by preventing rhombic deformation and the like, and is applicable to a single-taper or multi-step taper mold. It is an object of the present invention to provide a continuous casting mold that can be used.

[0008]

A mold for continuous casting according to claim 1 is a mold for continuously casting steel, wherein the cross-sectional shape of the mold is such that four straight sides are four quarters. It is a rounded rectangle connected by an arc, the radius of the quarter arc is large at the upper end of the mold and smaller at the lower end, and the inner peripheral length of the rounded rectangle is large at the upper end of the mold. It is characterized in that it is smaller on the lower end side. The mold for continuous casting according to claim 2 is a mold for continuously casting steel, wherein the cross-sectional shape of the mold is a rounded rectangle in which four straight sides are connected by four quarter arcs. The radius of the quarter arc is large at the upper end of the mold and smaller at the lower end, and the inner peripheral length of the rounded rectangle is larger at the upper end of the mold and smaller at the lower end. The rate of change of the inner peripheral length of the rounded rectangle is set based on both the taper amount of the straight side and the rate of change of the radius of the quarter arc.

According to the first aspect of the present invention, the air gap can be reduced by setting the taper amount of the straight side, and the occurrence of the hiccup phenomenon can be prevented by setting the radius of the quarter arc. Therefore, rhombus deformation and the like can be prevented, high-quality cast pieces having no defects on the inner and outer surfaces can be cast at high speed, and the present invention can be applied to a single-taper or multi-taper mold. According to the second aspect of the present invention, the amount of taper on the straight side and the amount of change in the radius of the quarter arc can be set separately, so that the amount of taper on the straight side and the amount of change in the inner peripheral length of the rounded rectangle are reduced. Can be set separately. Therefore, the taper amount of the straight side can be larger than the change amount of the rounded rectangle,
It can deal with changes in operating conditions such as casting temperature and steel type.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of the continuous casting mold of the present embodiment. FIG. 2 is a plan view of the continuous casting mold of the present embodiment. As shown in FIGS. 1 and 2, the continuous casting mold 1 of the present embodiment (hereinafter, simply referred to as a mold 1).
Is a mold for continuously casting steel.

In FIG. 1, the height direction is indicated by the Y axis. The height of the lower end of the mold 1 is indicated by y0, and the height of the upper end of the mold 1 is indicated by yn. Points obtained by dividing y0-yn at equal intervals are denoted by y1, y2, and y3. Y = y0, y shown in FIG.
The cross-sectional shapes of the mold 1 at the respective heights of 1, y2, y3, and yn are indicated by reference numerals L0, L1, L2, L3, and Ln in FIG. For example, reference symbol L0 indicates a cross-sectional shape at the lower end of the mold 1, and reference symbol Ln indicates a cross-sectional shape at the upper end of the mold 1.

As shown in FIG. 2, the cross-sectional shapes L0, L1, L2, L3, and Ln of the mold 1 of the present embodiment have four straight sides B regardless of the height of the mold. And a rounded square shape connected by four quarter arcs R. FIG.
In 4 and 5, the rounded rectangles L0, L1, L2, L3
Let a quarter arc in Ln be R0, R1, R2, L
3, Rn, and the straight sides are E0, E1, E2, E3, E
Indicated by n.

The present invention is characterized by the setting of a quarter-arc R forming a rounded square having a cross-sectional shape of the mold 1. The radius of the quarter arc R is set to be large at the upper end of the mold 1 and smaller at the lower end. That is, R0 <R1 <R2
<R3 <Rn is satisfied.

The inner peripheral length S of the rounded rectangle L is large at the upper end of the mold body 1 and smaller at the lower end.
That is, the relationship of L0 <L1 <L2 <L3 <Ln is satisfied.

Moreover, in the continuous casting mold 1 of the present embodiment, the rate of change of the inner peripheral length S of the rounded rectangle L is represented by the straight side B
And the rate of change of the radius of the quarter arc R can be set. When the taper amount of the straight side B is changed, it may be changed stepwise or continuously. For example, when the taper amount of the straight side B is constant, the mold 1 has a single taper. When the taper amount of the straight side B is changed stepwise, the mold 1 has a multi-stage taper. Furthermore, when the taper amount of the straight side B is continuously changed, the mold 1 has a parabolic taper. As described above, the continuous casting mold of the present invention can be applied to a single taper or a multi-stage taper mold.

The rate of decrease of the inner peripheral length S of the rounded rectangle L must decrease from the upper end to the lower end of the mold 1. That is, the degree of change of the inner circumference S is large at the upper end of the mold 1, and the degree of change of the inner circumference S is small at the lower end of the mold 1.

Next, based on FIGS.
Will be described in more detail. FIG. 3 shows the mold 1
3 is a cross-sectional view of the upper end of FIG. FIG. 4 is a cross-sectional view of the center of the mold 1. FIG. 5 is a cross-sectional view of the lower end of the mold 1. As shown in FIG. 1 again, the origin 0 is set on the inner surface excluding the corners at the lower end of the mold, and the Y axis is taken upward in parallel with the casting direction of the mold, and the X axis is taken in a direction perpendicular thereto. Any cross section A-
Assuming that the opposite side dimension in section A (Y = y) is B (y) and the radius of a quarter arc of the corner is R (y), the inner circumference S (y) is expressed by the following equation. S (y) = 4 ｛B (y) −2 · R (y)｝ + 2π · R (y) where B (y) = Bo + 2xx Since x is expressed as a function of y as described above, x = f
(Y), and the relationship between x and the taper is dS (y) since mold taper = 2 / Bo · dx / dy × 100.
/ Dy = 8 · dx / dy− (8−2π) · dR (y) / d
y.

Now, assuming that the mold taper is Tm, d
S (y) /dy=Bo/25.Tm- (8-2.pi.). DR
(y) / dy, and as is apparent from the above equation, the circumference S
Is the rate of change in the y direction of the taper Tm and the radius R of the corner arc
Is a function of the rate of change dR (y) / dy. Therefore, by changing the radius of the taper and the radius of the corner arc, the inner peripheral length change rate S (y) of the cross section of the mold body 1 can be arbitrarily set.

In the present invention, the term "square" includes a rectangle.

Next, a continuous casting method using the mold 1 of the present embodiment will be described. When using the mold 1 in which the inner peripheral length S of the rounded rectangle L can be changed by the taper Tm and the radius R of the corner arc, not only the decreasing rate of the inner peripheral length S but also the curvature by the quarter arc R After initially forming a solidified shell having a large radius, the radius of curvature is reduced toward the lower end of the mold so as to ensure contact between the solidified shell and the copper plate in the quarter arc R.

When the operating conditions such as the casting temperature and the type of steel change, the physical quantities representing the contact state between the solidified shell and the mold copper plate change. By measuring or calculating these physical quantities, the values can be adjusted within the appropriate range. It is good to intentionally move the molten steel level in the mold so that Examples of the physical quantity include (1) pull-out resistance in the mold, (2) copper plate temperature, (3) temperature difference between the water supply side and the drain side of the mold cooling water, and the like. Index.

For example, if excessive contact occurs during the operation, physical quantities such as the temperature difference between the inlet and the outlet of the mold cooling water, the temperature of the copper plate, and the value of the pull-out resistance in the mold increase. If this tendency further progresses, the tensile stress of the solidified shell below the slab constrained by the mold breaks beyond the allowable limit, leading to breakout. Therefore, by operating while monitoring the physical quantity, an optimal contact state can be maintained.

The physical quantity representing the contact state between the mold copper plate and the cast slab is not measured each time casting is performed, but an appropriate calculation of the molten steel level in the mold with respect to the operating conditions is performed based on data accumulated in advance. It is also possible to establish a method.

[0024]

According to the first aspect of the present invention, it is possible to prevent rhombic deformation and the like, to perform high-speed casting of a high-quality cast piece having no defect on the inner and outer surfaces, and to achieve a single-taper or multi-taper mold. Also applicable to According to the second aspect of the present invention, the amount of taper on the straight side and the amount of change in the radius of the quarter arc can be set separately, so that the amount of taper on the straight side and the amount of change in the inner peripheral length of the rounded rectangle are reduced. Can be set separately. Therefore, the taper amount of the straight side can be made larger than the change amount of the rounded rectangle, and it is possible to cope with a change in operating conditions such as a casting temperature and a steel type.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a continuous casting mold of the present embodiment.

FIG. 2 is a plan view of the continuous casting mold of the present embodiment.

FIG. 3 is a cross-sectional view of the upper end of the mold 1.

FIG. 4 is a cross-sectional view of a central portion of the mold 1.

FIG. 5 is a cross-sectional view of the lower end of the mold 1.

FIG. 6 is a schematic longitudinal sectional view of a conventional continuous casting mold, wherein (A) is a single taper mold, (B2) is a two-stage taper mold, and (Bn) is a parabolic taper mold.

FIG. 7 is a plan view of a conventional continuous casting mold.

[Explanation of symbols]

 1 Mold E Straight side S Inner circumference R Quarter arc R L Rounded square

Claims (2)

[Claims] 1. A mold for continuously casting steel, wherein the cross-sectional shape of the mold is a rounded rectangle in which four straight sides are connected by four quarter arcs. The radius of one arc is
A continuous casting mold, wherein the inner circumference of the rounded rectangle is greatly increased at the upper end of the mold and reduced at the lower end thereof. 2. A mold for continuously casting steel, wherein the cross-sectional shape of the mold is a rounded rectangle in which four straight sides are connected by four quarter arcs. The radius of one arc is
It is greatly reduced at the lower end side at the upper end side of the mold, and the inner peripheral length of the rounded rectangle is greatly reduced at the lower end side at the upper end side of the mold, and the rate of change of the inner peripheral length of the rounded square is reduced. And a rate of change in the radius of the quarter arc, which is set by both the amount of taper of the straight side and the rate of change of the radius of the quarter arc.