KR101712828B1 - Mold for casting - Google Patents

Abstract

A casting mold for casting a casting sheet, the casting mold including a plurality of plates spaced apart from each other so as to face each other and forming a space for passing a casting product therein, A coating layer containing a metal oxide is formed on at least a part of the inner wall of the mold and the quality of the cast steel can be improved by controlling the cooling ability of the mold.

Description

Mold for casting

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a casting mold, and more particularly, to a casting mold capable of controlling the cooling ability of the mold to improve the quality of the casting.

Generally, a cast steel is produced by cooling molten steel contained in a mold through a cooling stand. For example, in the continuous casting process, a molten steel is injected into a mold having a predetermined internal shape, and a reaction product is continuously drawn in the mold to the lower side of the mold to produce semi-finished products of various shapes such as slabs, blooms, billets, beam blanks, Process. In this continuous casting process, the casting is first cooled in the mold, and after passing through the mold, water is injected into the casting and the casting is secondarily cooled.

The surface quality and internal quality of the cast steel produced by the continuous casting process are the main factors determining the quality of the final product. Especially, the surface quality of the cast steel is greatly influenced by the initial solidification pattern in the mold. Therefore, securing the conditions for forming a uniform solidification layer throughout the mold is the most important factor in the continuous casting process.

However, the temperature difference between the mold and molten steel is very large near the bath surface of the molten steel in which the molten steel starts to solidify, and coagulation shrinkage occurs due to the thermal stress resulting in defects such as cracks on the surface of the cast steel. However, the structure of the cooling water flow path inside the mold can be changed in order to suppress such a phenomenon. However, since the structure of the cooling water flow path once constructed is difficult to be modified, there is a great restriction on quality improvement and steel type expansion, .

KR 1992-0000513A KR 2011-0131356A

The present invention provides a casting mold capable of retarding or preventing occurrence of surface defects of a cast steel by delaying the initial cooling rate of molten steel.

A casting mold according to an embodiment of the present invention is a casting mold for casting a cast steel, wherein the mold includes a plurality of plates spaced apart from each other so as to face each other and forming a space for passing the cast steel therein, A coating layer containing a metal oxide is formed on at least a part of the inner wall of the plate of the substrate.

The metal oxide may include a metal having a thermal conductivity lower than that of the material forming the mold.

The coating layer may be formed by stacking and continuously arranging the particles, and roughness may be formed on the surface.

The coating layer may comprise an adhesive.

The metal oxide may have a particle diameter of 0.1 to 10 mu m.

The coating layer may be formed to a thickness of 0.1 to 10 mm.

The coating layer may be formed in a half area with respect to the vertical length of the mold at the top of the mold.

The coating layer may be formed over an area of 50 to 100 mm above the bath surface of the molten steel accommodated in the mold and a range of 50 to 100 mm below the molten steel.

The casting produced using the casting mold according to the embodiment of the present invention can remarkably suppress defects generated on the surface during casting. That is, it is possible to retard or prevent occurrence of non-uniform coagulation shrinkage due to rapid solidification by delaying the solidification rate near the bath surface of molten steel in which molten steel starts to solidify. Therefore, surface defects occurring on the surface of the cast steel can be suppressed or prevented, and the quality of the cast steel can be ensured. Accordingly, it is possible to suppress or prevent the occurrence of defects such as an edge scab which occurs in a subsequent process (rolling) carried out using the manufactured cast steel, thereby reducing the load of the correction work for removing defects.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing a structure of a continuous casting apparatus. Fig.
2 is a perspective view illustrating a casting mold according to an embodiment of the present invention;
3 is a sectional view taken along the line AA in Fig.
4 is a photograph of a coating layer formed on a mold according to an embodiment of the present invention.

Hereinafter, a casting mold according to an embodiment of the present invention and a casting method using the casting mold will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

2 is a perspective view showing a mold according to an embodiment of the present invention, and Fig. 3 is a sectional view taken along the line A-A in Fig. 2. Fig.

With reference to Fig. 1, a continuous casting apparatus will be described.

The continuous casting apparatus includes a ladle 10 containing molten steel refined in a steelmaking process, a tundish 20 for receiving molten steel through an injection nozzle connected to the ladle 10 and temporarily storing the molten steel, And a mold 30 for receiving molten steel stored in the dish 20 and performing initial solidification in a predetermined shape. The plurality of segments 50 are successively arranged so as to perform a series of molding operations while the mold 30 is being poured from the mold 30 at the lower portion of the mold 30 And a cooling water flow path 40.

Here, the mold 30 is made of a copper alloy, and includes a plurality of plates spaced apart from each other so as to form a space for accommodating molten steel therein. 2, the plurality of plates constituting the mold 30 are composed of a pair of long side plates 32 opposed to each other and a pair of short side plates 34 connected to both sides of the long side plate 32 . At this time, a chamfered surface having a chamfered shape may be formed at a corner of the mold 30 to which the long side plate 32 and the short side plate 34 are connected. The chamfered surface of the corner portion of the mold 30 can suppress the surface defects of the cast steel due to the temperature drop at the corner portions of the cast steel. In addition, the short-side plate 34 may be formed to have a trapezoidal shape with its upper side width wider than its lower side width by being inclined downward inward. This is because the amount of shrinkage of the solidified shell is different at the upper side and lower side of the mold 30, that is, along the casting direction of the casting mold 30 when the molten steel is molded 30 to form a solidified shell (cast) To suppress.

A cooling water flow path 36 for forming a solidification shell by solidifying molten steel may be formed in the short side plate 34 and the long side plate 32 constituting the mold 30.

With this configuration, the mold 30 can solidify the molten steel by the cooling ability by the water of the mold 30 to produce the cast strip 1. However, the temperature difference between the mold 30 and the molten steel is very large at the upper region of the mold 30 where the molten steel starts to solidify, that is, near the molten steel bath surface, so that the molten steel rapidly solidifies. That is, the molten steel comes into contact with the surface of the cold mold 30 to start solidification. The heat flux is maximized near the bath surface where the initial solidification takes place, and the heat flux gradually decreases toward the lower portion of the mold 30. As described above, in the vicinity of the hot fluid surface having a large heat flux, the solidification of the molten steel occurs abruptly and the possibility of forming a non-uniform solidification layer is very high. As a result, surface defects such as cracks are generated on the surface of the cast steel, .

Therefore, in the present invention, the generation of the non-uniform solidification layer can be suppressed or prevented by delaying the solidification of the molten steel somewhat in the upper region of the mold 30 where molten steel starts to solidify.

It is possible to delay the solidification of the molten steel by forming the coating layer 38 having lower thermal conductivity than the copper alloy constituting the mold 30 in the upper region of the mold 30 where the molten steel starts to solidify.

The coating layer 38 may include a metal oxide having a thermal conductivity lower than that of the copper alloy. The metal oxide may contain titanium (Ti), zirconium (Zr), or the like. At this time, the metal oxide may be used as a powder and may have a particle diameter of about 0.1 to 10 mu m. When the metal oxide is mixed with the adhesive to form the coating layer 38, if the particle diameter of the metal oxide is smaller than the specified range, it is difficult to uniformly disperse the adhesive in a relatively high viscosity adhesive and it may be difficult to perform a role for lowering the thermal conductivity. In addition, when the particle size of the metal oxide is larger than the prescribed range, another defect may occur on the surface of the solidification layer, thereby deteriorating the quality of the cast steel.

The coating layer 38 may also include an adhesive. As the adhesive, a mixed solution of ethylene glycol and ethanol or a heat resistant adhesive capable of withstanding a temperature of 1000 DEG C or higher may be used. In the case of using a mixture of ethylene glycol and ethanol as the adhesive, the adhesive is removed by the heat of the molten steel during casting, so that only the metal oxide remains on the surface of the mold 30. When the heat resistant adhesive is used, (38) as it is. Such heat-resistant adhesives can be commercially available, such as Ceramabond and Pyro-Putty (trade name, AREMCO). These heat-resistant adhesives can bond ceramics with metals, metals and metals, and can be mixed with water as an aqueous product. Further, it can be coated on the surface of the mold 30, and then cured through drying and thermal drying, so that the state of being adhered to the mold 30 can be maintained. The mixing ratio between the adhesive and the metal oxide may be variously changed depending on the kind of the adhesive.

The coating layer 38 may be formed at least in part in the longitudinal direction of the mold 30, that is, the direction in which the lead pieces are cast. The coating layer 38 may be formed over the entire surface of the mold 30, but in this case, there is a problem in that the solidification is excessively delayed in the lower region of the mold 30 through which the main strips escape. The coating layer 38 can be selectively formed in the upper region of the mold 30 where the molten steel starts to solidify and can be formed within the half region of the mold 30 in the longitudinal direction of the mold 30 have. More specifically, the coating layer 38 may be selectively formed on the upper and lower predetermined regions of the bath surface, and may be formed, for example, from 50 to 100 mm above the bath surface and from 50 to 100 mm below the bath surface.

The coating layer 38 may be formed by spray coating a gel-like mixture obtained by mixing a metal oxide and an adhesive onto the inner surface of the mold 30. The coating layer 38 is coated on the surface of the mold 30 to form droplets which are adhered to each other to form particles. The particles are laminated and continuously formed to form a coating layer. It can be formed rougher than the surface. The shape of the coating layer 38, such as particle size, distribution, shape, etc., can be controlled by the particle diameter of the metal oxide, the viscosity of the mixture, the spraying distance during spray coating, the spraying time and the spraying pressure. The particles forming the coating layer 38 may be formed to have a size of about 0.1 to 10 mu m. If the particle size is smaller than the suggested range, it may be difficult to play a role in lowering the thermal conductivity. In addition, when the particle size is larger than the indicated range, another defect may be generated on the surface of the solidification layer, thereby deteriorating the quality of the cast steel.

The coating layer 38 may be formed to a thickness of 0.1 to 10 mm. When the thickness of the coating layer 38 is smaller than the range shown in the drawing, the effect of lowering the thermal conductivity is insignificant and it is difficult to lower the initial solidification time of the molten steel. When the thickness of the coating layer 38 is larger than the prescribed range, .

With such a configuration, the coating layer 38 can retard or prevent the surface defects of the casting due to the rapid solidification of the molten steel by delaying the initial solidification speed of the molten steel near the bath surface in the mold 30.

Hereinafter, an experimental example of forming a coating layer on the mold of the present invention will be described.

4 is a photograph of the coating layer formed by the experimental example.

[Experimental Example 1]

First, an adhesive for attaching the metal oxide to the mold 30 was provided. Ethylene glycol and ethanol may be used as adhesives. Ethylene glycol and ethanol are mixed at a weight ratio of 1: 1 and then stirred. Thereafter, TiO ₂ was prepared as a metal oxide, and the mixture was added to a mixed solution, that is, an adhesive, followed by stirring. At this time, TiO ₂ can be added at the same molar ratio as ethanol. Thus, the metal oxide is uniformly dispersed in the adhesive, and a gel-like mixture can be obtained. The mixture of adhesive and metal oxide reacts with each other to form a white network. In order to improve the dispersion degree of the metal oxide, the mixture was stirred at a speed of 150 rpm for 30 minutes.

The thus prepared mixture was sprayed on the inner surface of the mold 30 using a spray coating apparatus to form a coating layer 38. [ At this time, the mixture was sprayed using a pressure of 0.4 MPa and sprayed at a distance of 10 cm from the surface of the mold 30.

Thereafter, the coating layer 38 was dried for several hours to remove volatile components in the adhesive.

[Experimental Example 2]

Ethylene glycol and ethanol were used as adhesives. Ethylene glycol and ethanol were mixed at a weight ratio of 7: 3, and TiO ₂ was added in the same molar ratio of ethanol. The rest of the procedure was carried out in the same manner as in Experimental Example 1.

[Experiment result]

FIG. 4 is a photograph of the surface of the coating layer formed by Experimental Examples 1 and 2 by scanning electron microscopy (SEM). 4 (a) is a photograph of the surface of the coating layer formed by Experimental Example 1, and Fig. 4 (b) is a photograph of the coating layer formed by Experimental Example 2.

As a result of the experiment, it was confirmed that the size of the coating layer was 5 to 10 탆. It can be seen that the particles of the coating layer formed in Experimental Example 1 are somewhat larger than those of the coating layer formed in Experimental Example 2, and the particle size of the coating layer can be controlled by the composition of the adhesive.

If a casting layer is formed by forming a coating layer containing a metal oxide on the inner surface of the mold 30 as described above, the temperature difference between the mold 30 and the molten steel can be somewhat reduced, and the solidification rate of the casting can be delayed. Therefore, the degree of coagulation shrinkage due to rapid cooling of the molten steel can be reduced, and surface defects of the cast steel can be suppressed or prevented.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the following claims.

10: Ladle 20: Tundish
22: immersion nozzle 30: mold
36: cooling water passage 38: coating layer

Claims (8)

As a casting mold for casting a cast steel,
Wherein the mold includes a plurality of plates spaced apart from each other so as to face each other to form a space through which the cast steel passes,
A coating layer containing a metal oxide is formed on at least a part of an inner wall of the plurality of plates,
Wherein the coating layer is formed by spray coating a gel mixture obtained by mixing the metal oxide and an adhesive on the inner surface of the mold, and forming a roughness on the surface by forming the particles of the metal oxide by stacking and continuously arranging the particles, . The method according to claim 1,
Wherein the metal oxide comprises a metal having a thermal conductivity lower than that of the material forming the mold. delete delete The method of claim 2,
Wherein the metal oxide has a particle diameter of 0.1 to 10 占 퐉. The method of claim 5,
Wherein the coating layer is formed to a thickness of 0.1 to 10 mm. The method of claim 6,
Wherein the coating layer is formed in a region of the upper portion of the mold in a 1/2 region with respect to the vertical length of the mold. The method of claim 6,
Wherein the coating layer is formed over an upper area of 50 to 100 mm from a bath surface of molten steel accommodated in the mold and a lower area of 50 to 100 mm.

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