JPH067898A - Equipment and method for continuous casting - Google Patents

Abstract

PURPOSE:To provide a continuous casting equipment and its method which is appropriate to manufacture thick cast slab with little non-metallic inclusions or segregations and few surface flaws. CONSTITUTION:A metallic belt 1 traveling in the transverse direction, and a secondary cooling zone having a number of rollers and cooling water injecting nozzles are continuously arranged in the traveling direction of the metallic belt. A pair of side weirs 8a, 8b are provided between the metallic belt and the secondary cooling zone. A rear weir 10 is provided between the side weirs above the metallic belt. The rear weir 10 is constituted so as to heat the wall surface and/or blow the inert gas into the molten steel. Pouring of the molten metal 11 is executed by heating the lower part of the wall surface of the rear weir 10 to the temperature of 1000 deg.C-1500 deg.C, or by blowing two liters of inert gas per ton of the molten metal from the lower part of the wall surface of the rear weir 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plate thickness of 50 mm or more, and particularly a plate thickness of 300 mm suitable for producing a high-quality thick plate.
The present invention relates to a continuous casting machine and a continuous casting method capable of producing the slab-shaped cast piece.

[0002]

2. Description of the Related Art For example, as a method for producing a slab-shaped slab having a thickness of 300 mm or more, an ordinary ingot making method can be considered. However, the steel ingot produced by the ingot-making method has a problem that the homogeneity is insufficient due to segregation of the components, and a slab-rolling step for forming a desired slab is required, resulting in a low yield.

The slab-shaped slab can be manufactured by a vertical continuous casting machine. However, a slab having a thickness of 300 mm or more requires a secondary cooling zone having a strong structure to prevent bulging, and the line length to the cutting machine becomes long, resulting in a large-scale facility. In addition, the slab-shaped slab produced by the vertical continuous casting machine may have insufficient quality due to segregation in the center.

[0004]

In order to produce a high-quality thick plate, it is desirable to use a slab-shaped slab having good surface properties, less segregation and excellent cleanliness. The present invention has a good surface quality, less segregation, and a continuous casting machine having a simple structure suitable for producing a slab-shaped slab excellent in cleanliness and a slab-shaped slab continuous casting method using the same. Offering is an issue.

[0005]

FIG. 1 is an overall explanatory view of a continuous casting machine of the present invention, (A) is a front explanatory view, and (B) is a plan explanatory view. The continuous casting machine of the present invention has a metal belt 1 whose rear surface is cooled and runs sideways. In the present invention, the term “sideways” means approximately horizontal with an inclination angle of 5 ° or less. The metal belt 1 is an endless metal belt that is a pulley 2a.
And 2b, and the pulleys 2a and 2b are rotated in the arrow direction. Reference numeral 5 in the figure is a cooling device for cooling the back surface of the metal belt 1.

A secondary cooling zone 3 is arranged on the exit side of the metal belt 1. The secondary cooling zone has a large number of rollers 4 and injection nozzles 6 arranged between the rollers 4. Each injection nozzle 6 injects a cooling medium, such as water, upward. Also many rollers 4
Is arranged on the extension line of the metal belt so that its upper end is at the same height as the metal belt 1.

The continuous casting machine of the present invention is also provided with a space corresponding to the width W of the cast slab 7 to be manufactured, and the metal belts 1 and 2 are provided.
A pair of side wall weirs 8a extending over the next cooling zone 3
And 8b. The side wall weirs 8a and 8b run in the same arrow 9 direction as the metal belt 1 at the same speed as the metal belt 1.

Two or more side wall blocks, for example, 8-1, 8-2, and 8-3 shown in FIG. 1 (B) are connected to each other in the lengthwise direction so as to be separated from each other to form a side wall and run in the direction of arrow 9. As a result, the side wall block 8-
When 3 is separated from the side surface weir 8a, transferred to the position 8-0, and sequentially connected to the tail end of the side surface weir block 8-1, the three side surface weir blocks 8-1, 8-2, 8-3 can form the side wall 8a.

The continuous casting machine of the present invention also includes a metal belt 1
Between the upper side weirs 8a and 8b, there is a metal belt 1 and a rear side weir 10 arranged in close contact with the side weirs 8a and 8b. The rear weir 10 does not run in the direction of the arrow 9 but is provided at a fixed position. Therefore, the inner wall surfaces of the metal belt 1 and the side weirs 8a and 8b rub against the rear weir 10 to run.

FIG. 2 is an explanatory view of an example of the rear weir 10 of the continuous casting machine of the present invention, (A) is a front view and (B) is a right side view. The rear weir of the present invention has a heating device 13 for heating the lower part of the wall surface that comes into contact with the molten metal 11. This heating device 13 is, for example, a graphite refractory having an electric resistance heating property and a conducting electrode 1
It can be obtained by connecting 6 (+) and 16 (-), and applying a current from the current-carrying electrode to heat the graphite refractory.

For example, a slurry of graphite-based refractory material is applied to the pillars of urethane foam which form pores,
When this is fired, the urethane foam is thermally decomposed and disappears, and a porous graphite refractory having three-dimensional communication holes and electrical resistance heating properties is obtained. This porous graphite-based refractory material is arranged at 13 in FIG. 2, and a wind box 14 filled with a pressurized inert gas is attached to the back of the porous refractory material so that the opening surface of the wind box 14 is in close contact with the porous graphite refractory material. In this case, the inert gas sent from the inert gas introduction pipe 15 to the wind box 14 is blown into the molten metal 11 and the molten metal 1 of the present invention is
It becomes a gas blowing device that blows an inert gas into 1.

For example, the porous graphite refractory and the wind box 14 are arranged as described above, and the current-carrying electrodes 16 (+) and 16 (-) are connected to the porous graphite-based refractory to pass a current through the current-carrying electrodes. At the same time, when the wind box 14 is filled with a pressurized inert gas, a rear weir capable of heating and blowing the inert gas into the molten metal is obtained.

In the present invention, the heating device heats the lower part of the wall surface,
The gas blowing device blows gas from the lower part of the wall surface. As will be described later in detail, a solidified material is likely to be formed on the lower portion of the wall surface of the rear weir that is in contact with the molten metal, but if this solidified material is formed, the surface quality of the slab is impaired. In the present invention, the lower part of the rear weir is heated to prevent the formation of this solidified product, and the molten metal in the lower part of the rear weir is stirred with a blowing gas to prevent the formation of this solidified product. Therefore, in the present invention, the heating device heats at least the lower part of the rear weir, and the gas blowing device injects gas from at least the lower part of the rear weir. Therefore, the present invention does not require heating of the upper portion of the rear weir and blowing of gas from the upper portion.

The continuous casting method of the present invention will be described with reference to FIG. During continuous casting, the molten metal 11 is poured into a molten metal pool formed by the metal belt 1, the side surface dams 8a and 8b, and the rear surface dam 10 that does not run. The poured molten metal 11 is cooled by the metal belt 1 to form a solidified shell 12 on the metal belt 1. The solidified shell runs in the direction of arrow 9 while following the running of the metal belt 1 while growing.

After reaching the end of the metal belt in the traveling direction, the solidified shell is supported by the roller 4. When the end of the metal belt in the running direction is reached, the unsolidified molten metal 11 remains above the solidified shell 12, but the solidified shell has grown and is already thick and has sufficient strength. Even if the support by the belt 1 is changed to the support by the roller 4, no breakage or other trouble occurs. Since the unsolidified molten metal 11 exists above the solidified shell 12, the side walls are continuously supported by the side wall weirs 8a and 8b even in the secondary cooling zone 3 to prevent the molten metal 11 from flowing out from the side surface.

Even in the secondary cooling zone 3, the solidification shell 12
Is continuously cooled at its lower surface by a cooling medium such as water jetted from the jet nozzle 6, and grows while traveling in the direction of arrow 9 to complete solidification and become a slab 7. Slab 7
Is cut into a desired slab size by a conventional means, for example, a cutting machine (not shown) provided on the outlet side of the secondary cooling zone 3.

In the case of an ordinary steel ingot or a slab produced by a vertical continuous casting machine or a curved continuous casting machine, the side surfaces are strongly cooled, so that nonmetallic inclusions are easily trapped at the interface between the solidified shell and the molten metal. . In addition, segregation due to bulging due to static pressure becomes a problem.

In the present invention, the cast slab 12 is cooled exclusively from the bottom surface. The slab 12 runs in the running direction of the metal belt 1. As a result, the tip end surface of the solidified shell, that is, the interface between the solidified shell 12 and the molten metal 11 forms a gently inclined surface as shown in FIG. Therefore, the nonmetallic inclusions float vertically in the molten metal. However, the molten metal 11 is above the slope.
Only. Therefore, the segregated components and non-metallic inclusions are not captured by the solidified shell 12 and float in the molten metal. Further, since it is in the horizontal direction, the static pressure of the molten metal is extremely small, and bulging does not occur in the slab, so that the concentrated molten steel is not sucked as the solidification progresses, and segregation becomes slight. Therefore, the solidified shell 12 of the present invention and the cast piece in which the solidified shell has grown have few nonmetallic inclusions and segregation.

FIG. 3 is a schematic explanatory view of the generation of cold shut flaws on the surface of the cast slab. Since the vicinity of the lowermost end of the rear weir 10 is in contact with the cooled metal belt 1, the temperature is likely to drop, and a solidified substance 17 is easily formed on the lower portion of the wall surface of the rear weir as shown in FIG. 3 (A). This solidified product 17 is the solidified shell 1
Although not normally connected to 2, it will be connected intermittently. Since the solidified shell 12 follows the running of the metal belt 1 in the direction of arrow 9, the solidified material 17 is separated from the wall surface of the rear weir 10 as shown in FIG. 3 (B). When the solidified material 17 is peeled off, the joint with the solidified shell 12 becomes a discontinuous solidified structure. For this reason, cold shut flaws intermittently occur on the back surface of the slab.

In the present invention, the heating device or the gas blowing device provided on the rear weir 10 prevents the formation of the solidified matter 17. Therefore, according to the present invention, a continuously cast slab having less cold shut flaws can be obtained.

According to the knowledge of the present inventors, it is preferable that the heating of the wall surface of the rear weir by the heating device is performed at 1000 ° C to 1500 ° C. If it is less than 1000 ° C, the effect of preventing cold shut flaws is small. Further, if heated to 1500 ° C., no solidified product is formed, so heating at 1500 ° C. or higher is unnecessary. The amount of inert gas blown from the rear weir is 2 Nl /
It is preferable that the amount of molten steel is at least tons. When the blowing amount is less than 2 Nl / ton of molten steel, the force for stirring the molten metal is small, and the effect of preventing cold shut flaws is small.

In a normal vertical continuous casting machine, a secondary cooling zone having high strength is required to support the solidified shell whose center is not solidified from the side, and the static pressure of the unsolidified molten metal is required. Due to this, bulging is likely to occur. In the present invention, since the solidified shell is supported from below, the structure of the secondary cooling zone is simple, and since the static pressure of the unsolidified molten metal is extremely small, bulging does not occur.

[0023]

EFFECTS OF THE INVENTION By carrying out the present invention, a slab-shaped slab is obtained in which the occurrence of cold shut flaws is prevented and the surface properties are good, and segregation and non-metallic inclusions are small.
This slab is preferable for producing a high-quality thick plate. The continuous casting machine of the present invention has a simple structure.

[Brief description of drawings]

1 is an overall explanatory view of the continuous casting machine of the present invention, FIG. 2 is an explanatory view of a rear weir of the continuous casting machine of the present invention, and FIG. 3 is a schematic explanatory view of generation of cold shut flaws.

[Explanation of symbols]

1: metal belt, 2a (2b): pulley, 3: secondary cooling zone, 4: roller, 5: cooling device, 6: injection nozzle, 7: cast slab, 8a (8b): side wall, 9: metal belt , Solidification shell, running direction of side weir, 10: rear weir, 11: molten metal, 12: solidification shell, 13: heating device (refractory having electric resistance heat generation), 14: wind box,
15: Inert gas introduction pipe, 16 (+) (16 (-)): Current-carrying electrode, 17: Coagulated product.

Claims (2)

[Claims] 1. A metal belt having a back surface cooled and running laterally, a large number of rollers having upper ends at the same height as the metal belt, and an injection nozzle for injecting upward a cooling medium arranged between the rollers. The secondary cooling zone extends from the exit side of the metal belt in the running direction of the metal belt, and the secondary cooling zone extends across the metal belt and the secondary cooling zone at an interval corresponding to the width of the cast slab to be manufactured. In a continuous casting machine having a pair of side weirs that are arranged in parallel with each other and run in synchronization with the metal belt, and a rear weir that does not run closely disposed between the metal belt and the side weir between the side weirs on the metal belt, The rear weir includes a heating device for heating the lower part of the wall surface in contact with the molten metal, or a gas blowing device for blowing an inert gas into the molten metal from the lower part of the wall surface in contact with the molten metal, or a heating device and a gas blowing device in combination. Continuous casting machine. 2. The continuous casting machine according to claim 1, wherein the molten metal is poured into a pool formed by a metal belt, a side weir and a rear weir, and the wall surface of the rear weir which is in contact with the molten metal is 1000 to 1000. 1
Heat to 500 ° C, or blow 2Nl / ton of molten metal or more of inert gas from the rear weir, or 1000 ~
A continuous casting method, which comprises producing a continuously cast slab while heating at 1500 ° C. and blowing an inert gas of 2 Nl / ton of molten metal.