JPH1029043A - Continuous casting method for steel, and mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent longitudinal cracks in the surface of a cast slab and a recess in the cast slab caused by non-uniform solidification of a solidified shell in the vicinity of the meniscus in a continuous casting mold. SOLUTION: A continuous casting method of steel is provided by using a mold made of copper plate in which lattice-shaped plates 2 made of dissimilar metal or alloy of lower thermal conductivity than that of copper is provided on a surface of at least a longer side copper plate 1 with the lattice interval (a) of 10∼40mm, the plating width (b) (mm) satisfies the inequality of 0.2a<=b<=0.5a, the thickness is >=0.5mm, and the arrangement of the lattice is inclined in relation to the drawing direction of the cast slab, and by using the mold powder to satisfy the inequality of η<=0.3Vc+1.5, where η is the viscosity (poise) at 1300 deg.C and Vc(m/min.) is the drawing speed of cast slab, with the melting point is <=1100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast slab having excellent surface properties, which prevents vertical cracks and skewing of the cast slab surface caused by uneven solidification of a solidified shell near a meniscus in a mold. And a continuous casting mold for producing the same.

[0002]

2. Description of the Related Art In continuous casting of steel, vertical cracks and slab dents generated on the slab surface (hereinafter, slab dents are referred to as "depression") become product defects after rolling.
The mechanism of occurrence and preventive measures have been studied. From these examination results, it was found that the vertical cracking and the depression caused the shrinkage due to the δ → γ transformation immediately after the solidification.
~ 0.22wt.% Medium carbon steel and austenitic stainless steel, easy to occur, vertical cracks and depression are generated in the mold due to non-uniformity of solidified Schull thickness in initial solidification in the mold. It is known that the non-uniformity of the solidified shell thickness depends on the heat removal in the mold.

[0003] Since the composition of steel is determined by the application, it is not possible to avoid a range of components in which vertical cracking and depletion are likely to occur. Therefore, in order to prevent vertical cracking and depletion, the amount of heat removed from the mold is controlled. Techniques have been implemented to improve heterogeneous solidification and the results have been reported.

[0004] Yamachi et al., "Materials and Processes, vol. 6, No. 1
(1993) -287 "(hereinafter referred to as" prior art 1 "), by increasing the solidification temperature of the mold powder added to the mold and increasing the thickness of the mold powder fixing layer formed between the mold and the solidified shell. He reported that the heat conduction resistance was increased and the mold was cooled slowly, resulting in improved uneven solidification and prevention of depletion.

[0005] Nakai et al., "Iron and steel, vol. 73, No. 3 (1987),
498 "(hereinafter referred to as" prior art 2 ") on the surface of the mold copper plate with a width of 0.8 mm, a depth of 0.3 to 0.4 mm, and a pitch of 0.1 mm.
A 9 mm groove is provided in the vertical direction to forcibly create an air gap between the mold copper plate and the solidified shell. As a result, it is possible to reduce the heat removal in the vicinity of the meniscus by 30 to 40%. Reported that it was prevented.

[0006] Japanese Patent Laid-Open No. 1-289542 (hereinafter, referred to as
In "Prior art 3"), a lattice-like groove is formed on the surface of a mold copper plate near the meniscus by a depth of 0.5 to 1.0 mm and a width of 0.1 mm.
The grooves were filled with dissimilar metals (Ni, Cr) or ceramics at a distance of 5 to 1.0 mm, and the grooves were filled with different kinds of metals (Ni, Cr) or ceramics, thereby giving partial strength to the cooling ability of the mold, thereby preventing the slab surface cracks. (Hereinafter, the mold disclosed in Prior Art 3 is referred to as a “lattice groove mold”). The technique of Prior Art 3 is as follows.
The formation of the initially solidified shell is slightly delayed in the groove portion, which is a weakly cooled portion, and thin portions of the shell are left at regular intervals, and the strain during solidification contraction is absorbed in this portion. Then, the mold copper plate and the solidified shell are brought into close contact with each other to prevent generation of an air gap, secure uniform heat removal in the mold, and grow the solidified shell uniformly.

[0007]

In the prior art 1, uneven solidification is improved by using a mold powder having a high melting point. However, when a mold powder having a high melting point is used, a thick layer of the mold powder is formed between the mold and the solidified shell, and the consumption of the mold powder which is effective for slow cooling but is also a lubricant between the mold and the solidified shell. During high-speed casting, there is a risk of restraint breakout due to seizure between the mold and the solidified shell,
Difficult to implement.

The prior art 2 has a problem that at the start of casting, when molten steel is poured into a mold, the molten steel enters the groove, and the solidified shell and the mold are seized to cause a breakout.

In prior art 3, the width of the groove is 1 mm or less, which is problematic in that it is too small. As can be seen from the results of the actual machine test described below, the temperature difference of the mold copper plate between the groove portion filled with metal and the portion without the groove is small due to the small groove width, and therefore, the partial removal of the groove portion. It has been found that the effect on the difference in calorific value is small. There is also a problem such as the separation of different metals or ceramics in the grooves.

As described above, the prior arts have respective problems and cannot be said to be a complete measure. The present invention has been made in view of the above circumstances, and an object thereof is to prevent a vertical crack and depletion of a slab and to provide a continuous casting method and a continuous casting mold capable of producing a slab having excellent surface properties. To provide.

[0011]

The continuous casting method of steel according to the present invention is characterized in that at least the surface of a long-side copper plate is coated with a grid-like plating of a dissimilar metal or alloy having a lower thermal conductivity than copper and a grid spacing a of 10 to 40 mm. , Plating width b is set to 0.2a ≦ b ≦ 0.5a (m
m), using a copper plate mold having a thickness of 0.5 mm or more and a lattice array inclined with respect to the direction of drawing the slab, the melting point is 1100 ° C. or less, and the viscosity η (pois
e) is characterized by using a mold powder satisfying the expression (1) in relation to the slab drawing speed Vc (m / min.). η ≦ 0.3Vc + 1.5 (1)

The continuous casting mold for steel according to the present invention comprises:
The copper plate surface is plated with a lattice of a dissimilar metal or alloy having a lower thermal conductivity than copper, the lattice spacing a is 10 to 40 mm, the plating width b is 0.2a ≦ b ≦ 0.5a (mm), and the thickness is 0.5 mm. As described above, the arrangement of the lattices is characterized by having the long-side copper plate provided inclining with respect to the slab-drawing direction.

[0013] In order to improve the durability of the mold, it is desirable that the contact surface between the lattice plating made of dissimilar metal and the long side copper plate be formed as a curved surface.

FIG. 1 shows an outline of a long side copper plate which is a component of the casting mold for continuous casting according to the present invention. In the drawing, reference numeral 1 denotes a long-side copper plate of a mold, and reference numeral 2 denotes a plating portion made of a dissimilar metal having a lower thermal conductivity than copper applied to the inner surface of the long-side copper plate 1 in a lattice shape. Plating part 2
Is arranged such that the arrangement of the plating grid is inclined by an angle θ (hereinafter, the angle is referred to as “inclination angle”) with respect to the direction of drawing the slab of the mold. Nickel, chromium, and alloys of these metals are optimal as dissimilar metals having lower thermal conductivity than copper.

At least the inside of the long-side copper plate is plated with a lattice-like dissimilar metal, the lattice spacing a is 10 to 40 mm, the plating width b is 0.2 a ≦ b ≦ 0.5 a (mm), and the thickness is 0.5 mm or more. A continuous casting mold in which the lattice arrangement is inclined with respect to the slab drawing direction (hereinafter, referred to as "lattice-plated mold")
The use of a solidified shell having a uniform thickness can be obtained as compared with a conventional flat copper plate or a continuous casting mold (hereinafter, referred to as a “plate-shaped mold”) in which the entire surface is plated. The reason is as follows.

FIG. 2A shows how a non-uniform solidified shell is formed when a flat mold is used. In the figure, 3
Is a solidified shell, and 4 is a long side copper plate of a flat mold. The molten steel is cooled by the long side copper plate 4 and solidified. Δ occurs immediately after solidification
→ The solidified shell 3 is deformed by the large solidification shrinkage accompanying the γ transformation, but is warped at a constant interval L because it is pushed back by the molten steel static pressure. At this time, a part of the solidified shell 3 is peeled off from the long side copper plate 4 to form an air gap 5, the amount of heat removed at that portion decreases, and the subsequent solidification is delayed. As a result, large irregularities are formed in the solidified shell.

On the other hand, in the case of the lattice plating mold of the present invention in which the lattice spacing a is 10 to 40 mm, the plating width b is 0.2a ≦ b ≦ 0.5a (mm), and the thickness is 0.5 mm or more, FIG.
As shown in (b), lattice spacing a (where a <L)
Since the plating portion 2 is formed in a lattice shape in the manner described above, a portion with a small amount of heat removal is compulsorily and regularly formed, so that a solidification delay occurs in the plating portion 2 and solidification caused by solidification shrinkage accompanying the γ → δ transformation. The deformation of the shell 3 occurs at every lattice interval a. Therefore, the warpage of the solidified shell 3 is reduced, and the contraction strain is concentrated on the solidification delay portion. Although the shrinkage strain is concentrated on the solidification delay portion, the crack is not generated so much that the adhesion between the mold and the solidification shell is improved. As a result, large deformation of the entire solidified shell 3 does not occur,
No air gap 5 is generated, and solidification of a uniform thickness is promoted.

If the lattice spacing a is less than 10 mm or more than 40 mm, the rate of occurrence of vertical cracks in the slab increases, as will be described later.

In the present invention, since the dissimilar metal is plated, the possibility of peeling from the joint with the mold copper plate is extremely small. Further, in the present invention, the arrangement of the grid plating is inclined with respect to the direction of drawing the slab of the mold, and more desirably, the contact surface between the grid plating and the mold copper plate is made a curved surface, thereby repeating the process. In this case, there is no plating peeling on the surface of the mold copper plate to which the thermal stress load is applied and there is no plating peeling at the joint portion, and it is possible to extend the life of plating on the copper plate.

During casting, the mold powder fills the space between the copper mold plate and the solidified shell, and the mechanism for improving the non-uniform solidification by the mold is actually also performed indirectly through the mold powder. When the mold powder has a high melting point, a thick powder fixing layer is formed between the molten powder layer and the mold copper plate, and an air gap is generated between the fixing layer and the mold copper plate. The heat transfer in the air gap is a convective heat transfer or a radiative heat transfer, and the heat transfer is significantly reduced as compared with the heat transfer in the solid. Therefore, when an air gap is generated, the air gap governs the heat transfer in the mold, so that the slow cooling effect of the plating portion is reduced, and the solidification delay is reduced, and the effect of the solidification delay portion is reduced.

Therefore, in order to sufficiently exhibit the characteristics of the grid-plated mold, the space between the mold copper plate and the solidified shell is filled with a uniform molten powder layer, and the fixing layer on the mold copper plate side is reduced in thickness.
It is important to use mold powder that does not easily cause an air gap.

In the present invention, the use of a low-viscosity mold powder having a viscosity at 1300 ° C. within the range of the formula (1) with respect to the drawing speed Vc (m / min.) Makes it possible to reduce the distance between the mold copper plate and the solidified shell. The uniform inflow of powder into the mold is ensured, and the use of a mold powder having a low crystallization temperature of 1100 ° C. or less suppresses the formation of a fixed layer on the mold side. Can be sufficiently derived. Also, the higher the slab drawing speed, the higher the temperature on the solidified shell side between the mold and the solidified shell, so that the practical viscosity of the mold powder increases in proportion to the drawing speed.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of a long side copper plate which is a component of a continuous casting mold according to the present invention. 1A is a side view, and FIG. 1B is a cross-sectional view. In the drawing, reference numeral 1 denotes a long-side copper plate of a mold, and 2 denotes a plating portion of a dissimilar metal having a lower thermal conductivity than copper which is formed on the inner surface of the long-side copper plate 1 in a grid shape (a lattice interval a mm, a plating width b mm, a thickness c mm). It is. The procedure for applying the continuous casting mold according to the present invention will be described below.

As a dissimilar metal having a lower thermal conductivity than copper,
Nickel, chromium, and alloys of these metals are selected and used as plating materials.

The plating part 2 is arranged in the direction of drawing the slab of the mold.
The inclination angle is given by θ. Since the inclination angle is desirably 15 ° or more, it is arbitrarily determined in the range of 15 ° to 45 °. Note that the range where the tilt angle is 45 ° or more is rotationally symmetric with the case where the tilt angle is 45 ° or less (for example, a tilt angle of 60 ° is rotationally symmetric with a tilt angle of 30 °). Value.

The grid spacing a of the grid plating is determined at an arbitrary value of 10 to 40 mm, and the plating width b is set to 0.2 based on the grid spacing a.
It is determined by an arbitrary value in the range of a ≦ b ≦ 0.5a (mm).
The plating thickness is set to an arbitrary value of 0.5 mm or more, and a groove is formed on the long-side copper plate 1 so as to have the determined grid spacing amm, plating width bmm, and thickness cmm. At this time, it is desirable to form a groove so that the contact surface between the plating portion 2 and the long side copper plate 1 is a curved surface.
The plating thickness is related to the thickness of the mold copper plate. However, if the thickness is large, the cost of processing the copper plate and the cost of plating will be high.

In this way, plating is applied to the long-sided copper plate 1 having the groove. Unnecessary plating is masked so as not to be plated. After plating, long side copper plate 1 having plating part 2
The entire inner surface is smoothed to complete the long-sided copper plate 1 of the grid-plated mold.

Although the short side copper plate is not plated here, the same plating portion 2 as the long side copper plate 1 may be provided for the short side copper plate. .

The maximum value of the casting speed is determined from the specifications of the continuous casting machine to be used, and the upper limit of the viscosity at 1300 ° C. of the mold powder to be used is obtained by the equation (1). Using a mold powder having a melting point of 1100 ° C. or less, casting is performed with a grid-plated mold manufactured by the above method.

[0030]

【Example】

(Embodiment 1) Lattice spacing, plating width In order to determine appropriate lattice spacing a and plating width b, nickel was used as a plating material, and a grid-shaped plating mold with an inclination angle of 45 ° was used. Casting test at a drawing speed of 2.0 m / min. Using a mold powder with a concentration of 0.10 to 0.12 wt% medium carbon steel having a viscosity of 2.0 poise at 1300 ° C and a crystallization temperature of 950 ° C. went.

First, assuming that the plating thickness is constant at 0.5 mm,
Casting was performed using a mold in which the lattice spacing a was changed in the range of 1 mm to 60 mm, and the occurrence of longitudinal cracks in the slab was investigated. However, the plating width b was all b = a / 2. The result is shown in FIG.
From the results shown in FIG. 3, it was found that the lattice spacing a is preferably 10 to 40 mm.

Next, assuming that the plating thickness is constant at 1.0 mm,
Lattice spacing a was set to two levels of 10 mm and 20 mm, and casting was performed using a mold with a varied plating width b, and the occurrence of vertical cracks in the slab was investigated. The result is shown in FIG. From the results shown in FIG. 4, when the lattice spacing a is 10 mm, the plating width b is 2 to 5 m.
m, grid width a = 20 mm, plating width b is 4-10 m
m turned out to be good.

From the above, it can be said that it is optimal that the relationship between the lattice spacing a and the plating width b satisfies 0.2a ≦ b ≦ 0.5a.

Example 2 Lattice Plating Thickness In order to determine an appropriate plating thickness, the grid spacing was 10 mm, the plating width was 5 mm, the inclination was 45 °, and the plating thickness was 0.2 to 2.0 mm.
Using a template changed in the range, the carbon concentration is 0.10
0.12 wt% medium carbon steel with viscosity at 1300 ° C
A casting test was carried out with a mold powder having a crystallization temperature of 0 poise and a crystallization temperature of 950 ° C. at a drawing speed of 2.0 m / min. FIG. 5 shows the result. From the results shown in FIG. 5, it was found that the optimal plating thickness was 0.5 mm or more. That is, if the thickness is less than 0.5 mm, the thickness is not sufficient, so that the slow cooling effect of the grid plating does not appear.

Example 3 Grid Plating Arrangement Nickel is used as a plating material, grid spacing is 10 mm, plating width is 5 mm,
A test was performed in which the arrangement of the plating grid was changed in the slab drawing direction using a mold having a grid-like plating with a plating thickness of 2 mm. For the first strand of the continuous casting machine, a mold whose lattice arrangement coincides with the slab drawing direction (tilt angle 0 °) is used, and for the second strand, a mold whose tilt angle is changed to 15 °, 30 °, 45 ° is used. , 250 tons / heat of molten steel
00 heat casting.

FIG. 6 shows the cracking index on the plated surface of the long side copper plate after 700 heat casting. The crack generation index was determined by performing a color check on the plating surface and as a ratio to the amount of crack generation (total length) on the plating surface in a grid-like plating mold having a tilt angle of 0 °. As shown in FIG. 6, it was found that the crack generation index decreased as the inclination increased, and that the occurrence of cracks on the plated surface was the least when the inclination was 45 °, which was optimal for extending the life of the mold.

The molten steel in the mold controls the temperature distribution on the surface of the copper plate, and the thermal stress caused by the temperature distribution on the surface of the copper plate promotes cracking of the plated surface. The thermal stress can be reduced by inclining the lattice arrangement with respect to the drawing direction.

Example 4 Influence of mold powder viscosity and crystallization temperature Lattice interval 10 mm, plating width 5 mm, nickel plating thickness 0.5
Using a grid-plated mold according to the present invention having a thickness of 45 mm and a tilt angle θ of 45 °, medium carbon steel having a carbon concentration of 0.10 to 0.20 wt% was cast by changing the viscosity of the mold powder and the speed of drawing the slab. The incidence of longitudinal cracks in the pieces was investigated. The drawing speed is 0.6 ~ 3.0m / min., 1300 ℃ of mold powder
Has a viscosity of 0.5 to 3.0 poise and a crystallization temperature of 950 ° C.
And

FIG. 7 shows the relationship between the viscosity η and the rate of occurrence of vertical cracks at a drawing speed of 2.2 m / min. In the figure, indicates a slab that is acceptable (the rate of occurrence of vertical cracks is 0), and • indicates a slab that is rejected (with vertical cracks). If the viscosity η at 1300 ° C exceeds 2.0 poise, the test is rejected. Therefore, when the drawing speed was 2.2 m / min., It was found that a mold powder having a viscosity η at 1300 ° C. of 2.0 poise or less should be used.

Similarly, the relationship between the viscosity and the vertical crack was determined at other drawing speeds, and the results are shown in FIG. Again, the crystallization temperature of the mold powder is 95
The one at 0 ° C. was used. In the figure, the result is acceptable (the rate of occurrence of vertical cracks is 0), and the symbol ● is reject (there is vertical cracks). The most viscous slab of the passing slabs at each drawing speed is almost on a straight line with respect to the drawing speed (m / min.), And when the straight line is obtained by a linear regression equation, the equation (2) is obtained. Was. η (poise) = 0.3Vc + 1.5 (2)

Therefore, the range in which no vertical cracks occur in the slab is given by equation (1). η (poise) ≦ 0.3Vc + 1.5 (1)

Next, using the same grid-plated mold according to the present invention as described above, using a medium carbon steel having a carbon concentration of 0.10 to 0.20 wt%, a viscosity η at 1300 ° C. of 2.2 poise and a crystal The drawing speed was 2.6 m / min. And 3.
A casting test at 0 m / min. Was performed to investigate the occurrence of vertical cracks in the slab.

FIG. 9 shows the results of the investigation. In the figure, Δ indicates a pass (the rate of occurrence of vertical cracks is less than 0.1%), and ● and ▲ indicate a failure (a rate of occurrence of vertical cracks of 0.1% or more). Crystallization temperature is 1100
It is good when the temperature is lower than 1 ° C, but rejected when the temperature is higher than 1100 ° C.

(Embodiment 5) Influence of bonding surface between plating and copper plate Nickel was used as plating material, grid spacing was 10 mm, plating width was 5 mm,
Using a mold having a plating thickness of 1 mm and a grid plating with a tilt angle of 15 °, a test was conducted in which the joining surface between the plating and the copper plate was changed. As shown in FIG. 10, the joint between the plating and the copper plate has a wedge-shaped edge on the first strand of the continuous casting machine, and the joint between the plating and the copper plate has a 1/1 / plating width b on the second strand. A mold joined by a curved surface of No. 5 was used. In this test, the radius of curvature of the curved surface is equivalent to 1 mm.

FIG. 11 shows the crack generation index on the plated surface of the long side copper plate after 700 heat casting. The crack initiation index is
A color check was performed on the plated surface, and the result was shown as a ratio to the amount of cracks generated (total length) on the plated surface having a wedge-shaped joint. From FIG. 11, it was found that making the joining surface between the plating and the copper plate a curved surface was effective for extending the life of the mold.

(Example 6) Comparison with a conventional lattice groove mold A grid-like nickel plating having a lattice spacing of 10 mm, a plating width of 5 mm, a plating thickness of 0.5 mm, and a tilt angle of 45 ° was applied to the first strand of the continuous casting machine. The grid-like plating mold according to the present invention, which has been subjected to the present invention, is mounted thereon, and as a comparison, the grid groove mold disclosed in Prior Art 3 (grid width 0.5 mm, grid spacing 10 mm, depth 0.5 mm, filler nickel) ) And carbon concentration of 0.
10 ~ 0.12wt% of medium carbon steel slab drawing speed Vc =
A casting test was performed at 2.0 m / min. Mold powder has a viscosity of 2.0 pois at 1300 ° C for both strands.
e. A crystallization temperature of 950 ° C. was used.

In this test, a thermocouple was attached to the plated portion 2 or the nickel-filled portion 6 and the portion 7 where they were not present as shown in FIG. The temperature of the copper plate at that time was measured. There were a total of four measurement positions, which were embedded from the rear surface near the meniscus in the center of the long side copper plate of the mold and at a position 1 mm from the surface. This is indicated by a white circle in FIG. From the measured values at each position, the average ΔT of the temperature difference between the two points (ΔT = T ₂ −
T ₁ ) and ΔT ′ (ΔT = T ₄ −T ₃ ).

FIG. 13 shows the result. In the lattice-shaped plating mold A according to the present invention, there is a temperature difference in which the average value of ΔT exceeds 5 ° C., whereas in the lattice groove mold B of the prior art, the temperature difference is small, and the influence on the difference in the amount of heat removal due to the groove is small. Therefore, the effect of improving the uneven solidification cannot be expected.

(Example 7) Casting of medium carbon steel The first strand of the continuous casting machine was subjected to a grid-like nickel plating having a grid spacing of 10 mm, a plating width of 5 mm, a plating thickness of 0.5 mm, and a tilt angle of 45 °. A grid-type plating mold according to the present invention is mounted, and as a comparison, a flat-plate mold with nickel plating on the entire surface is mounted on the second strand, and a carbon concentration of 0.08 to 0.18 wt.
% Of medium carbon steel was subjected to a casting test at a drawing speed Vc of 0.6 to 3 m / min., And the longitudinal cracking rate of the slab was investigated. The mold powder used for both strands,
The viscosity at 1300 ° C is 1.6 poise and the crystallization temperature is 95
The one at 0 ° C. was used. FIG. 14 shows the result. The lattice plating mold has been confirmed to have an effect of suppressing vertical cracking with respect to the flat mold, and the effect is remarkable in a high-speed casting region with a slab drawing speed of 1.4 m / min or more.

(Example 8) Casting of austenitic stainless steel Austenitic stainless steel with δ → γ transformation (SU
(S304 steel) was applied with the lattice plating mold of the present invention. Nickel is used as a plating material on the first strand of the continuous casting machine, lattice spacing 10 mm, plating width 5 mm, plating thickness 0.5 mm,
Using a mold plated with a grid-like plating at an inclination of 45 °, using a conventional flat mold plated with nickel over the entire surface as compared with the second strand, the viscosity at 1300 ° C. is 2.0.
SUS304 steel was cast at a draw speed of 2.2 m / min. with a mold powder having a crystallization temperature of 950 ° C. and the number of depletions was investigated.

FIG. 15 shows the result. FIG. 15 shows that the grid-plated mold of the present invention obtained good results even with SUS304 steel. In addition, the effect of the grid-plated mold of the present invention was confirmed by a similar test for SUS316 steel.

[0052]

As described above, according to the present invention, an appropriate mold powder is used in combination with a mold copper plate in which lattice-like nickel plating is applied to the inner surface of a long-side copper plate at an angle in the direction of drawing a slab. , And vertical cracks and depletion caused by uneven solidification of the solidified shell near the meniscus were prevented, and a slab having excellent surface properties even at the time of high-speed casting could be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing an outline of a long side copper plate of a continuous casting mold according to the present invention, wherein (a) is a side view and (b) is a sectional view.

FIG. 2 is a diagram showing a comparison of the growth of a solidified shell between a lattice plating mold according to the present invention and a conventional flat mold.

FIG. 3 is a view showing the effect of the lattice spacing of lattice plating on the incidence of vertical slab cracks.

[FIG. 4] Lattice interval a of lattice plating is 10 mm and 20 m.
FIG. 4 is a diagram showing the effect of plating width on the rate of occurrence of vertical slab cracks in the case of m.

FIG. 5 is a diagram showing the influence of the plating thickness of lattice plating on the occurrence rate of vertical slab cracks.

FIG. 6 is a diagram showing the effect of the inclination angle (inclination angle) of the lattice arrangement with the slab drawing direction on the crack generation index on the plating surface of the mold.

FIG. 7 is a view showing the relationship between mold powder viscosity at 1300 ° C. and the rate of occurrence of vertical cracks when casting is performed at a slab drawing speed of 2.2 m / min. Using the lattice-shaped mold of the present invention.

FIG. 8: Using the lattice mold of the present invention, 0.6 to 3.0 m /
FIG. 3 is a diagram showing the relationship between mold powder viscosity at 1300 ° C. and the rate of occurrence of vertical cracks at a slab drawing speed of min.

FIG. 9 shows the relationship between the crystallization temperature of mold powder and the rate of occurrence of vertical cracks in the slab when the slab drawing speed is 2.6 m / min. And 3.0 m / min. Using the lattice-shaped mold of the present invention. FIG.

FIGS. 10A and 10B are views showing a joint between the grid plating and the copper mold plate in the lattice mold of the present invention, wherein FIG. 10A shows a mold having a joint having a wedge shape, and FIG. Of (1 /
5) A mold joined with a curved surface of R.

FIG. 11 is a view showing the influence of the shape of the joint between the plating surface and the mold copper plate on the crack generation index on the plating surface in the grid plating of the present invention.

FIG. 12 is a view showing a position where a thermocouple is installed for measuring a temperature of a mold copper plate in the lattice mold of the present invention and a conventional lattice groove mold.

FIG. 13 is a diagram showing a comparison between temperature measurement results during casting in the lattice-shaped mold of the present invention and a conventional lattice groove mold.

FIG. 14 is a diagram showing a comparison between the relationship between the rate of occurrence of vertical cracks in slabs and the drawing speed between the example of the present invention and the conventional example in medium carbon steel having a carbon concentration of 0.08 to 0.18 wt%. It is.

FIG. 15 is a diagram showing the number of depletions of a slab of SUS304 steel in an example of the present invention and a conventional example.

[Explanation of symbols]

 1: long side copper plate 2: plating part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryuzo Nishimachi, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Inventor Hiroshi Murakami 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Honko Co., Ltd.

Claims (4)

[Claims] 1. At least on the surface of a long side copper plate, grid-like plating of a dissimilar metal or alloy having lower thermal conductivity than copper, lattice spacing a is 10 to 40 mm, plating width b is 0.2a ≦ b ≦ 0.5a.
(Mm), using a copper plate mold having a thickness of 0.5 mm or more and a lattice array inclined with respect to the direction of drawing the slab, the melting point is 1100 ° C. or less, and the viscosity η at 1300 ° C. ( po
ise), using a mold powder that satisfies the formula (1) in relation to the slab drawing speed Vc (m / min.). η ≦ 0.3Vc + 1.5 (1) 2. The continuous casting method of steel according to claim 1, wherein a contact surface between the grid-plated metal of a dissimilar metal and the long side copper plate is a curved surface. 3. A copper plate surface is plated with a lattice of a dissimilar metal or alloy having a lower thermal conductivity than copper, and the lattice spacing a is 10 to 40 m.
m, having a plating width b of 0.2a ≦ b ≦ 0.5a (mm), a thickness of 0.5 mm or more, and having a long-side copper plate with a lattice arrangement inclined with respect to the slab drawing direction. Features A continuous casting mold for steel. 4. The continuous casting mold for steel according to claim 3, wherein a contact surface between the grid-plated metal of a different kind of metal and the long side copper plate is a curved surface.