JP2010207843A - Continuous casting method of molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting method of molten metal capable of improving lubrication between the inner wall face of a mold and a solidified shell and stably casting a slab having superior surface characteristic. <P>SOLUTION: In the continuous casting method of molten metal, an AC electric current satisfying a frequency of 30-300 Hz is made to flow in a solenoid type electromagnetic coil which is arranged in a manner surrounding a mold 15 or imbedded in the mold 15 having an inner width ≥800 mm in the width direction and ≥150 mm in the thickness direction of a cast slab. Also, to the molten metal 16 in the mold 15, an electromagnetic force is applied, the electromagnetic force satisfying 300-5,000 gausses in the maximum value of a magnetic flux density formed at least in the range up to 400 mm in the casting direction from a meniscus 17 position. In applying the electromagnetic force, a minimum thickness of a molten powder 18 layer covering the meniscus 17 upper face of the molten metal 16 is maintained at 7 mm or more, and the continuous casting is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a continuous casting method for molten metal (particularly molten steel).

As shown in FIG. 3, in the continuous casting of molten metal, molten metal 80 that has been refined passes from a container 81 called a ladle through an intermediate container 82 called a tundish, and is cast by a continuous casting nozzle 83 into a mold 84. It is injected into.
Then, the solidified shell 85 is formed by the primary cooling by the mold 84, and subsequently the solidification is promoted by the secondary cooling by the water spray from the cooling nozzle laid on the support segment 86 disposed below the mold 84, and continuously. The slab 87 is manufactured. In addition, the number 88 in FIG. 3 is the pinch roll which draws out the slab 87 downstream.

In the mold 84, powdery lubricant powder 89 is added to the meniscus surface of the molten metal 80, and the molten metal contact surface side of the lubricant powder 89 is melted. This molten powder 90 (hereinafter referred to as molten powder) is placed in a flow path 91 formed between the inner wall surface of the mold 84 that vibrates under a predetermined condition and the solidified shell 85 drawn at a constant speed. The molten powder 90 flows in and is consumed due to the natural fall due to the static pressure of the molten powder 90 (inflow by the force acting on the meniscus surface by its own weight) and the interaction between the inner wall surface of the mold 84 and the solidified shell 85.
The inflow amount (consumption amount) of the molten powder 90 into the flow channel 91 affects the lubrication between the inner wall surface of the mold 84 and the solidified shell 85, and therefore the surface property of the slab 87 manufactured by continuous casting is determined. It is an important factor to dominate.

For this reason, if the width of the flow path 91 (that is, the thickness of the powder film formed between the inner wall surface of the mold 84 and the solidified shell 85) is reduced, the molten powder 90 flows into the flow path 91. The following problems occur because the amount decreases.
Since the surface temperature of the inner wall surface of the mold 84 is increased and the frictional resistance between the inner wall surface of the mold 84 and the solidified shell 85 is increased, the surface of the slab 87 is cracked. The slab 87 cannot be pulled out by being seized on the inner wall surface. Furthermore, when the slab 87 is forcibly pulled out from the mold 84 under such circumstances, the solidified shell 85 is broken and a small amount of unmelted molten metal leaks (bleed) or a large amount leaks ( Breakout).
Therefore, in order to stably cast slabs with excellent surface properties without affecting production, methods to increase the flow rate (consumption) of molten powder into the flow path and reduce the flow rate so far Various methods for making this difficult have been proposed.

For example, Patent Document 1 discloses that a CaO—BaO—SiO ₂ —F-based composition base material having a required composition that has been preliminarily melted and glassy, contains 2 to 15 wt% of an alkali metal / alkaline earth metal carbonate. In addition, 2-30 wt% of alkali metal / alkaline earth metal fluoride and 0.2-10 wt% of carbon are mixed, and if necessary, at least one of each metal oxide of Fe, Mn, and Ni There is described a mold powder for continuous casting which is composed of a composite compound in which the above is mixed in an amount of 2 to 10% by weight in an inner frame, has a solidification temperature of 900 ° C. or less and a viscosity at 1300 ° C. of 3 poise or less.
Patent Document 2 discloses that the initial viscosity η (poise) of powder at 1300 ° C., initial surface tension τ (dyn / cm ² ), powder entrainment index P, and casting amount W (ton / ton) per unit time of one strand. Describes a method for producing continuous cast pieces having no powder-type internal defects by casting so that a predetermined time satisfies a predetermined condition.

Patent Document 3 describes a powder supply method for supplying powder smoothly by supplying an alternating current in pulses to an electromagnetic coil embedded in a side wall of a mold in continuous casting.
In Patent Document 4, an AC magnetic field having a frequency of 30 to 200 Hz and a magnetic flux density of 1000 gauss or more is formed in a range of at least 10 cm in the casting direction from the meniscus position of the molten steel, and the electromagnetic pressure toward the mold center axis is set in the molten pool. And a method of continuously casting a steel slab using a continuous casting powder adjusted to have a viscosity of 0.5 to 2.0 poise (at 1300 ° C.) and a melting point of 900 to 1200 ° C.
Furthermore, Patent Document 5 discloses that in a continuous casting method in which electromagnetic force is applied to molten steel in a mold and the meniscus shape is changed, the powder viscosity is 16 to 200 poise and the maximum magnetic flux density is 300 to 5000 gauss. Thus, a method of continuously casting a steel slab is described.

JP 60-72653 A JP-A-62-238053 JP-A-64-83348 JP-A-4-3119056 Japanese Patent No. 4091777

However, the conventional technique still has the following problems to be solved.
In Patent Documents 1 and 2, by adjusting the viscosity of the molten powder, the flowability of the molten powder is affected through the interaction between the inner wall surface of the mold and the solidified shell. However, when casting a large-section slab (for example, a slab having a large cross-sectional area cast with a mold having an inner width in the width direction of 800 mm or more and an inner width in the thickness direction of 150 mm or more), the molten powder layer is extremely In a local region where the thickness of the molten powder is reduced, the static pressure of the molten powder becomes small, and even if the viscosity of the molten powder is changed, the inflow site of the molten powder is limited. For this reason, it is not possible to prevent a reduction in the amount of molten powder flowing into the flow path, and the surface properties of the slab may be deteriorated or the operation may be hindered.

Moreover, in patent documents 3-5, since inflow of the molten powder between the inner wall face of a casting_mold | template and a solidification shell is accelerated | stimulated, the surface property of slab can be improved. However, since the inflow amount of the molten powder increases, the thickness of the molten powder layer covering the upper surface of the meniscus becomes thin. In particular, when casting a large-section slab, the static pressure of the molten powder is reduced at a local site where the molten powder layer becomes extremely thin, and the inflow site of the molten powder is limited. As a result, the amount of molten powder flowing into the flow path is reduced, and a slab defect may occur or the operation may be hindered.
From the above, the conventional method did not work effectively in preventing the occurrence of slab defects in casting of a large-section slab.

In addition, when casting a large cross-section slab, applying a technology that expands the flow path of the molten powder formed between the inner wall surface of the mold and the solidified shell by electromagnetic force, the shape of the meniscus (surface shape) is temporal. In addition, the meniscus shape is uneven and uneven, and a part where the molten powder layer becomes extremely thin locally occurs. If this phenomenon continues, in the part where the molten powder layer becomes thinner, the static pressure by the molten powder layer becomes smaller and the inflow part of the molten powder is limited, so the amount of molten powder flowing into the flow path is reduced. Slab defects may occur or the operation may be hindered.

The present invention has been made in view of such circumstances, and when casting a slab having a large cross-sectional area, the lubrication between the inner wall surface of the mold and the solidified shell can be improved, and a slab having excellent surface properties can be stably cast. An object of the present invention is to provide a continuous molten metal casting method.

The molten metal continuous casting method according to the present invention that meets the above-mentioned object is arranged so as to surround a mold having an inner width in the width direction of 800 mm or more and an inner width in the thickness direction of 150 mm or more, or in the mold. A magnetic flux density formed in a range from the meniscus position to at least 400 mm in the casting direction is applied to the molten metal in the mold by passing an alternating current satisfying a frequency of 30 Hz to 300 Hz through the solenoid type electromagnetic coil embedded in In a continuous casting method of molten metal in which casting is performed while applying an electromagnetic force satisfying a maximum value of 300 gauss or more and 5000 gauss or less,
When the electromagnetic force is applied, continuous casting is performed while ensuring a minimum thickness of 7 mm or more for the molten powder layer covering the upper surface of the meniscus of the molten metal.

In the molten metal continuous casting method according to the present invention, the molten metal casting speed may be 1.2 m / min or more.

The molten metal continuous casting method according to the present invention performs continuous casting while ensuring a minimum thickness of the molten powder layer covering the upper surface of the molten metal meniscus at the time of applying electromagnetic force, so that the static pressure of the molten powder layer is reduced. Can be increased. As a result, the amount of molten powder flowing between the inner wall surface of the mold and the solidified shell can be increased even under conditions where the molten powder layer is locally extremely thin, and the surface of the slab can be increased. The properties can be improved and the operation can be stabilized.

In addition, when the molten metal casting speed is set to 1.2 m / min or more, the effect of improving the surface properties of the slab and the effect of stabilizing the operation appear more remarkably.
This is because, when the molten metal casting speed is 1.2 m / min or more, the meniscus shape change is larger than when the molten metal is less than 1.2 m / min, so the surface properties and operability of the slab are deteriorated. Because it is easy to do.

(A) is a side sectional view of a mold for manufacturing a small-section slab when no electromagnetic force is applied, (B) is a side sectional view of a mold for manufacturing a small-section slab when electromagnetic force is applied, and (C) is an electromagnetic FIG. 4D is a side sectional view of a mold for producing a large-section slab when no force is applied, and FIG. 4D is a side sectional view of a mold for producing a large-section slab when an electromagnetic force is applied. It is explanatory drawing which shows the influence which the casting speed of molten steel and the minimum thickness of a molten powder layer have on operability and quality. It is explanatory drawing of the continuous casting method.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, after explaining the background to the idea of the molten metal continuous casting method according to one embodiment of the present invention, the molten metal continuous casting method will be described.
First, a slab having a small cross-sectional area (hereinafter also referred to as a small cross-section slab) is continuously used by using a mold that does not satisfy an inner width in the width direction of the cast slab of 800 mm or more and an inner width in the thickness direction of 150 mm or more The case of casting will be described. In addition, the casting_mold | template which casts a small cross-section slab here refers to the casting_mold | template which has the space part whose inner width of the width direction of a slab to cast is less than 800 mm, or the inner width of a thickness direction is less than 150 mm. This space is formed by the inner wall surface of the mold.

As shown in FIGS. 1A and 1B, a solenoid type electromagnetic coil (not shown) provided in the mold 10 is supplied with an alternating current satisfying a frequency f of 30 Hz to 300 Hz, and the molten steel in the mold 10 is supplied. (Example of molten metal) Casting is performed while applying an electromagnetic force satisfying a maximum value B _{max of} magnetic flux density B _max of 300 gauss to 5000 gauss formed in the range from meniscus position 12 to at least 400 mm in the casting direction. .

At this time, due to electromagnetic force, the flat shape of the meniscus of the molten steel 11 shown in FIG. 1 (A) changes to a shape in which the central portion in the width direction of the mold 10 is convex upward as shown in FIG. 1 (B). Note that a difference in height of about 10 to 20 mm occurs in the meniscus of the molten steel.
Further, the solidified shell formed is moved away from the inner wall surface of the mold 10 by the electromagnetic force in the vicinity of the meniscus of the molten steel 11 due to electromagnetic force, and the flow of the molten powder 13 formed between the inner wall surface of the mold 10 and the solidified shell. The width of the channel, that is, the channel 91 shown in FIG. 3 (corresponding to the thickness of the powder film) is enlarged. For this reason, the molten powder 13 flows into the flow channel 91 due to the natural fall of the molten powder 13 due to the static pressure (inflow by the force acting on the meniscus surface by its own weight) and the interaction between the inner wall surface of the mold 10 and the solidified shell. Is promoted.

As described above, the flow of the molten powder 13 into the flow channel 91 is promoted. As a result, the thickness of the molten powder 13 layer on the meniscus surface is slightly reduced and the static pressure of the molten powder 13 layer is also reduced. Therefore, the inflow of the molten powder 13 is not hindered. Therefore, the surface properties of the slab are improved, and the operation is stabilized (the frequency of bleeding and breakout that hinders the operation is reduced).
Moreover, when the pattern which repeats application and non-application of electromagnetic force with a short period is used, the molten steel flow induced by electromagnetic force can be suppressed and the surface property and operability of a slab improve further.

Here, when the frequency f is less than 30 Hz, the generated electromagnetic force is too small, the shape change of the meniscus of the molten steel is small, and the solidified shell does not move away from the inner wall surface of the mold. Sex is not improved.
On the other hand, when the frequency f exceeds 300 Hz, the electromagnetic force is blocked by the mold and is not applied to the molten steel in a normal integrated mold having a long side and a short side. For this reason, the shape change of the meniscus of molten steel becomes small, the solidified shell does not move away from the inner wall surface of the mold, and the surface properties and operability of the slab are not improved.
For this reason, although the frequency f was 30 Hz or more and 300 Hz or less, it is preferable that the lower limit is 50 Hz and the upper limit is 250 Hz.

Further, when the maximum value B _{max of the} magnetic flux density formed within at least 400 mm from the meniscus of the molten steel is less than 300 gauss, the electromagnetic force is too small, the shape change of the meniscus of the molten steel is small, and the solidified shell is within the mold. Since it is not far from the wall surface, the surface properties and operability of the slab are not improved.
On the other hand, when the maximum value B _max of the magnetic flux density exceeds 5000 gauss, the electromagnetic force is too large, the shape of the central portion in the width direction of the meniscus of the molten steel changes excessively into a convex shape, and the electromagnetic force The molten steel flow velocity induced by is excessive. For this reason, the shape of the meniscus fluctuates with time, and the shape of the meniscus becomes undulating and non-uniform, and the width of the flow path through which the molten powder flows between the solidified shell and the mold wall surface, that is, the powder film The thickness fluctuates with time, and a portion where the thickness is not uniform over the entire circumferential direction of the inner wall surface of the mold is generated. As a result, the inflow of molten powder is locally reduced, and the surface properties and operability of the slab are not improved.
For this reason, the maximum value B _max of the magnetic flux density is set to 300 gauss or more and 5000 gauss or less, but the lower limit is preferably 700 gauss and the upper limit is 3000 gauss.

However, as a result of the casting test, as shown in FIGS. 1C and 1D, the inner width in the width direction of the slab to be cast (an example of a slab) is 800 mm or more even when electromagnetic force is applied (the upper limit is For example, a slab having a large cross-sectional area (hereinafter also referred to as a large cross-section slab) was continuously cast using a mold 15 having an inner width in the thickness direction of 150 mm or more (upper limit is, for example, about 700 mm). In this case, it was found that the surface properties of the slab deteriorated and the operation became unstable. Here, the casting mold for casting a large-section slab refers to a casting mold having a space portion whose inner width in the width direction is 800 mm or more and whose inner width in the thickness direction is 150 mm or more. In addition, operation becomes unstable, so that the cross-sectional area of the above-mentioned space part becomes large exceeding 120,000 mm < ² > (= 800 mm x 150 mm).
This phenomenon occurs similarly when the solenoid type electromagnetic coil is arranged so as to surround the mold and when it is embedded in the mold.

Therefore, the following knowledge was obtained by conducting a study based on the casting test and the actual measurement of the thickness of the molten powder layer on the meniscus surface.
As shown in FIG. 1C, in a continuous casting using a mold 15 for casting a large-section slab, an alternating current satisfying a frequency f of 30 Hz to 300 Hz is applied to a solenoid type electromagnetic coil provided on the mold 15. Electromagnetic force satisfying the maximum value B _{max of} magnetic flux density formed in the range from the position of the meniscus 17 to at least 400 mm in the casting direction on the molten steel (an example of molten metal) 16 in the mold 15 is 300 gauss or more and 5000 gauss or less. Is applied, the area of the meniscus 17 surface also increases, so that the shape of the meniscus fluctuates with time, tends to be spatially non-uniform, and a resonance phenomenon may occur. For this reason, coupled with the action of electromagnetic force, the meniscus 17 shown in FIG. 1 (C) locally has a height difference of about 15 to 25 mm as shown in FIG. 1 (D). Moreover, as a result of the flow channel 91 shown in FIG. 3 expanding and the inflow of the molten powder 90 into the flow channel 91 being promoted, the layer thickness of the molten powder 90 tends to decrease.

Therefore, in the locally raised meniscus portion, the minimum thickness T of the molten powder 18 layer is extremely thin, and the minimum thickness of the molten powder 18 layer is 0 mm (that is, the molten steel 16 is in contact with the powdery powder or the atmosphere) ), Or the minimum thickness of the molten powder 18 layer may be more than 0 mm and less than 7 mm.
Thereby, the natural fall by the static pressure of the molten powder 18 to the flow path between the inner wall surface of the mold 15 and the solidified shell in the part is inhibited, the surface property of the slab deteriorates, and the operation becomes unstable. I found out that

Therefore, as a result of intentionally performing a casting test in which the minimum thickness T of the molten powder 18 layer was changed, the inventors conceived the continuous casting method of molten steel metal according to an embodiment of the present invention.
That is, the continuous casting method of molten steel metal according to an embodiment of the present invention is a method of performing continuous casting while ensuring a minimum thickness T of a molten powder layer covering the upper surface of the meniscus of molten steel at least 7 mm when electromagnetic force is applied. is there.
This prevents a decrease in the amount of molten powder flowing into the flow path by increasing the static pressure of the molten powder layer even when the electromagnetic force is applied in continuous casting using a mold that casts a large-section slab. Thus, it was found that the surface properties of the slab can be improved and the operation becomes stable.

The molten powder layer is not particularly limited because the effect of increasing the static pressure is obtained as the thickness of the molten powder layer is increased. This is because during casting under a condition where no electromagnetic force is applied, the distance from the upper end of the mold to the meniscus position of the molten steel is usually about 80 to 150 mm, the molten powder layer becomes too thick, This is due to deterioration in operability such as outflow from the upper end of the mold.
As described above, as a method of covering the upper surface of the meniscus with the molten powder, any method may be used as long as the minimum thickness T can ensure 7 mm or more, for example, the following method.

(1) Adjust the ratio of the high melting point component and low melting point component in the powdered powder, or the particle size of the low melting point component, and the hatching rate (melting rate) is higher than before without changing the viscosity and solidification temperature. A method of raising about 1 to 3 times.
(2) A method in which the amount of carbon in the powdery powder is increased to increase the heat build-up and the hatching rate is increased.
(3) A method of increasing the hatching speed by installing a heat source such as a heater directly above the powdery powder.
(4) A method of increasing the amount of powdery powder charged onto the upper surface of the meniscus.

The minimum thickness of the molten powder layer is measured, for example, by inserting an iron plate having a width of 200 mm and a thickness of 1 mm into the powder powder, molten powder, and molten steel from above the mold, dipping for about 1 second, and then pulling up and adhering to the iron plate. This is done by evaluating the thickness of the molten slag (see FIG. 3).
In this embodiment, this method is adopted, but other measurement methods may be used.
For example, by inserting multiple steel wires with a diameter of 1 mm into the powder powder, molten powder, and molten steel from the upper part of the mold, immersing them for about 1 second, pulling them up, and evaluating the thickness of the molten slag adhered to the steel wires You can also.
Alternatively, two coating-resistant electrodes may be immersed in powder powder, molten powder, and molten steel from above the mold, and measured from the change in resistance between the electrodes.

Furthermore, when the molten steel casting speed is increased to 1.2 m / min or more compared to the case where the molten steel casting speed is less than 1.2 m / min under the condition that the minimum thickness T of the molten powder layer is less than 7 mm, It has been found that the surface properties and operability of the slab are extremely deteriorated.
That is, the margin for improving the surface properties and operability of the slab by ensuring a minimum thickness T of the molten powder layer of 7 mm or more is 1.2 m / min compared with the case where the casting speed of the molten steel is less than 1.2 m / min. It turned out that it is larger when the time is more than minutes. In addition, since the effect of the thickness of the molten powder layer according to the present invention appears remarkably as the casting speed of molten steel increases, the upper limit value is not specified, but at present, the casting speed of molten steel is 2.4 m. In some cases, it was done at a minute.
As described above, as the casting speed of molten steel increases, the margin for improving the surface properties and operability of the slab increases. The larger the casting speed of molten steel, the greater the fluctuation width of the meniscus height of the molten steel. It is large and the amount of molten powder flowing into the flow path is likely to fluctuate.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, molds of various dimensions (400 mm × 100 mm, 800 mm × 100 mm, 800 mm × 150 mm, 1200 mm × 250 mm, 1000 mm × 400 mm) are used, and low carbon aluminum killed steel (liquidus temperature: 1535 ° C., temperature in the tundish : 1565 ° C.) at a casting speed of 0.6 to 1.7 m / min.
The casting mold used for casting has an electromagnetic coil having a height of 100 mm, with the upper end position of the coil as the meniscus position of the molten steel and surrounding the casting mold for 20 turns.
In addition, the continuous casting nozzle (immersion nozzle) used is provided with one (two in total) molten steel discharge holes on both sides of the lower end thereof, and its axis is 35 degrees downward with respect to the horizontal direction. It is slanted.

When casting the slab using the above-mentioned mold, an alternating current having a frequency f of 60 Hz is applied to the solenoid type electromagnetic coil provided in the mold, and the slab is formed in a range from the meniscus position to at least 400 mm in the casting direction. The maximum magnetic flux density value B _max was 1500 gauss, and the application pattern of electromagnetic force was a repetition of 0.05 second application and 0.05 second non-application. The mold amplitude (oscillation) was ± 2 to 6 mm (amplitude distance: 4 to 12 mm) with respect to the reference position, and the frequency was 90 to 300 cycles / minute.
The powdery powder is prepared by adding 1.5 to 8% by mass of Na ₂ O to the C—Ca—SiO ₂ —Al ₂ O ₃ system and adjusting the viscosity to 4 poise (1300 ° C.). The minimum thickness of the molten powder layer covering the upper surface of the meniscus was changed between 0 mm or more than 0 mm and 22 mm or less, and the operability of the casting operation and the quality of the manufactured slab were evaluated.
The test conditions and test results are shown in Tables 1 and 2.

In addition, the operability evaluation shown in Tables 1 and 2 is “◯” when the number of bleeds detected per 5 m of slab is less than 0.1, and when it is 0.1 or more and less than 0.5. Is “Δ”, and the case of 0.5 or more is “×”.
In addition, the quality is evaluated by hot rolling the manufactured slab and then pickling and cold rolling to produce a steel sheet having a thickness of 0.9 mm. ) Was compared with the reference example. At this time, the number of wrinkles in the reference example is 1, and a case of less than 0.2 is “◯”, a case of 0.2 to 0.5 is “Δ”, and a case of more than 0.5 is “×”. did.
The reference example is a result of casting without applying electromagnetic force, using a mold of dimensions: 1200 mm × 250 mm, casting speed 1.6 m / min, and minimum thickness of the molten powder layer 25 mm. .

Reference Examples 1 to 5 in Table 1 are molds having an inner width dimension of less than 150 mm on one side of the mold, and are not molds for producing a large-section slab, and the above-described problems did not occur. When the cross-sectional area of a mold having dimensions of 800 mm × 150 mm is 1, the cross-sectional area of Reference Examples 1 and 2 is 0.33 (= 40000 / 120,000), and the cross-sectional area of Reference Examples 3 to 5 is 0.67 (= 80,000 / 120,000).
For this reason, for Reference Examples 1 to 5, the operability evaluation was “◯”, and for Reference Examples 3 to 5, the slab quality evaluation was also “◯”. In addition, since the reference examples 1 and 2 are not rolled, quality evaluation is not performed.

On the other hand, the dimension shown in Table 1 is a mold of 800 mm × 150 mm, which is a mold for casting a large-section slab, but as shown in Examples 1 to 9, by ensuring a minimum thickness of the molten powder layer of 7 mm or more, Both evaluations of operability and quality were “◯”.
However, in Comparative Examples 1 to 9, since the minimum thickness of the molten powder layer was less than 7 mm, the operability and quality evaluation were both “Δ” or “×”.
Here, the effect of the casting speed of the molten steel will be described with reference to FIG. 2, comparing the results of Comparative Examples 1, 2, 5, 6, 9 and Examples 1 to 3, 6, and 7.
As is clear from FIG. 2, the minimum thickness of the molten powder layer was set to 7 mm or more (7 mm) (Examples 1 to 3, 6, and 7). It was. However, when the minimum thickness of the molten powder layer is less than 7 mm (6 mm), if the casting speed of the molten steel is less than 1.2 m / min (Comparative Examples 1 and 2), both the operability and quality evaluation are rejected. However, it was “△”.
Therefore, when the minimum thickness of the molten powder layer is 7 mm or more, the operability and quality improvement effects can be further enhanced by setting the casting speed of the molten steel to 1.2 m / min or more.

Moreover, although the dimension shown in Table 2 is a mold of 1200 mm × 250 mm, which is a mold for casting a large-section slab, as shown in Examples 10 to 14, by ensuring a minimum thickness of the molten powder layer of 7 mm or more, Both evaluations of operability and quality were “◯”.
On the other hand, in Comparative Examples 10 to 13, since the minimum thickness of the molten powder layer was less than 7 mm, the operability and the quality evaluation were both “x”.
In addition, if the cross-sectional area of the mold of dimension: 800 mm x 150 mm is 1, each cross-sectional area of Examples 10-14 and Comparative Examples 10-13 is 2.5 (= 300000 / 120,000).

And the dimension shown in Table 2: 1000 mm x 400 mm mold is a mold for casting a large cross-section slab, but as shown in Examples 15 to 17, by ensuring a minimum thickness of the molten powder layer of 7 mm or more, The evaluation of operability was “◯”.
On the other hand, in Comparative Example 14, since the minimum thickness of the molten powder layer was less than 7 mm, the operability evaluation was “x”.
Here, as in Reference Examples 1 and 2, since the rolling is not performed, the quality is not evaluated.
In addition, when the cross-sectional area of the mold having dimensions of 800 mm × 150 mm is 1, the cross-sectional areas of Examples 15 to 17 and Comparative Example 14 are 3.33 (= 400000 / 120,000).

From the above, by using the molten steel continuous casting method of the present invention, when casting a slab having a large cross-sectional area, the lubrication between the inner wall surface of the mold and the solidified shell is improved, and the surface property is excellent. It was confirmed that stable slabs could be cast stably.
As in the prior art described above, the viscosity of the molten powder also affects the flowability of the molten powder through the interaction between the inner wall surface of the mold and the solidified shell. Therefore, in the casting test, we examined the conditions for changing only the viscosity of the molten powder. However, when electromagnetic force was applied using a mold that casts a large-section slab, the surface properties and operability of the slab could not be improved. It was.
This is considered to be because, in a local region where the molten powder layer is extremely thin, even if the viscosity of the molten powder is changed, it is not possible to prevent a reduction in the inflow amount of the molten powder.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the molten metal continuous casting method of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
Moreover, although the case where molten steel was used as a molten metal was demonstrated in the said embodiment, if it is the molten metal which performs continuous casting using the casting_mold | template with which the solenoid type electromagnetic coil was provided, it will not be limited to this.

10: mold, 11: molten steel (molten metal), 12: meniscus position, 13: molten powder, 15: mold, 16: molten steel (molten metal), 17: meniscus, 18: molten powder

Claims (2)

The frequency is 30 Hz or more and 300 Hz or less in a solenoid type electromagnetic coil arranged so as to surround a mold having an inner width in the width direction of the cast slab of 800 mm or more and an inner width in the thickness direction of 150 mm or more, or embedded in the mold. An electromagnetic current satisfying a maximum value of a magnetic flux density formed in a range from the meniscus position to at least 400 mm in the casting direction is applied to the molten metal in the mold satisfying 300 gauss to 5000 gauss. In the continuous casting method of molten metal that is cast while
A continuous casting method of molten metal, wherein continuous casting is performed while ensuring a minimum thickness of a molten powder layer covering the upper surface of the meniscus of the molten metal of 7 mm or more when the electromagnetic force is applied. 2. The molten metal continuous casting method according to claim 1, wherein a molten metal casting speed is set to 1.2 m / min or more.

Images