KR20160048688A

KR20160048688A - Method for coating mold of continuous casting apparatus and mold with coating layer

Info

Publication number: KR20160048688A
Application number: KR1020150148148A
Authority: KR
Inventors: 박순홍; 장진영
Original assignee: 재단법인 포항산업과학연구원
Priority date: 2014-10-23
Filing date: 2015-10-23
Publication date: 2016-05-04
Also published as: KR101766856B1

Abstract

A method to coat a mold of a continuous casting apparatus comprises a step of forming a spray coated layer by fusing and cooling powder for coating using a laser to form a uniform coated layer regardless of a shape of a mold. The mold has a surface to be in contact with a cast piece, which includes a plane and inclined surfaces protruding from the plane. The step of forming the spray coated layer comprises: a step of forming the spray coated layer on the plane of the mold; a step of forming the spray coated layer on the inclined surfaces of the mold; a step of forming the spray coated layer along a connection part of the plane and the inclined part of the mold. According to the present invention, a uniform coated layer is able to be formed on a mold having a bent or a curved shape.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of coating molds and performance facilities of a performance facility,

The present invention relates to a mold coating method for improving wear resistance of a mold of a performance facility and a mold of a performance facility manufactured therefrom.

In recent years, the rate of continuous casting has been increasing, and a lot of research is being conducted to improve the casting ability. In particular, in order to improve the casting ability, it is essential to extend the life of the mold. If the lifetime of the mold for continuous casting is increased, the service life of the continuous casting mold can be extended to improve the overall casting ability of the casting machine.

The mold for continuous casting consists of two long side molds and short side molds, respectively. The life of the short side mold is shortened to about 1/2 of that of the long side mold so that the mold is replaced according to the life of the short side mold. If the lifetime of the mold is increased, the maintenance repair period can be extended to improve the overall casting ability of the caster.

In order to increase the lifetime of the mold, a coating layer for improving abrasion resistance was formed on the short side mold. Conventionally, a more uniform coating layer having improved abrasion resistance was formed on the surface of the mold using a laser spray coating technique.

However, the conventional technique using laser spray coating is a technique for improving the wear resistance through hardness increase, and a short side mold having a coating layer is rubbed against a long side mold, resulting in a problem that a long side mold is worn. That is, the short side mold is brought into contact with the long side mold while being assembled, and is moved along the long side for varying the mold width, so that the long side mold is worn.

In addition, in the case of a recently developed chanfered mold, there is a problem in that it is difficult to properly form a spray coating layer through the conventional laser spray coating technique. The chamfer mold has a shape in which both ends of the short side mold are projected obliquely for the purpose of controlling defects occurring in the cast steel and increasing the quality of the cast steel, so that friction with the cast is frequently generated and abrasion is particularly serious.

In the case of such a chaser mold, plating or spray coating should be uniformly formed along the projected inclined surface of the chamfer mold. However, in the case of the spray coating layer, there is a problem that the spray coating of the inclined surface and the curved shape is difficult due to the straightness of the sprayed powder.

The plating layer is formed uniformly in the mold of the general flat plate type, but the bubble formation and defects of the plating layer occur along the projected slope in the bent chamfer mold.

There is provided a mold coating method of a mold and a performance facility of a performance facility capable of forming a uniform coating layer on a mold having a curved or curved shape including a chamfer mold.

Also provided is a mold coating method for a mold and a performance facility of a performance facility capable of minimizing wear of a long side mold by a short side mold.

A mold coating method for a performance facility comprising melting and cooling a coating powder using a laser of this embodiment to form a spray coating layer, wherein the surface of the mold is in contact with the casting to form a projected sloped surface with respect to the plane and the plane The spray coating layer forming step may include a step of forming a spray coating layer on the plane of the mold, a step of forming a spray coating layer on the inclined surface of the mold, and a step of forming a spray coating layer along the connection between the plane and the inclined surface of the mold .

When forming the spray coating layer at the connection portion between the plane of the mold and the inclined surface in the spray coating layer formation step, the spray coating layer may be formed by irradiating only the laser without supplying the coating powder.

And adjusting the irradiation angle of the laser according to the plane or inclined surface position of the mold in the spray coating layer formation step.

In the coating method, the mold may further include a long side mold and a short side mold provided so that both sides thereof are in contact with the inner surface of the long side mold, and forming a plating layer on both sides of the short side mold after formation of the spray coating layer have.

The coating method may further include cutting both sides of the short side mold by a thickness of the plating layer before forming the plating layer on both sides of the short side mold.

The plating layer formed on both side surfaces of the end mold may be a copper plating layer.

The coating method may further include forming a Ni plating layer on the surface of the mold before forming the spray coating layer.

In the step of forming the spray coating layer, the powder for coating may be a mixture of NiCr powder and at least one selected from B and Si.

The B may be mixed in an amount of 1 to 3% by weight based on the coating powder.

The Si may be mixed at 2 to 5 wt% with respect to the coating powder.

The size of the coating powder may be 40-150 mu m.

On the other hand, the performance equipment mold of this embodiment has a Ni plating layer formed on a flat surface and a sloped surface, the surface of which contacts with the cast steel forms a projected inclined surface with respect to the plane and the plane, and a Ni plating layer formed on the Ni plating layer through a laser spray coating process Coating layer.

Wherein the mold includes a long side mold and a short side mold provided so that both side surfaces thereof are in contact with the inner surface of the long side mold, and the short side mold further includes a plating layer formed on both side surfaces thereof, .

The plating layer formed on both side surfaces of the short side mold may be a copper plating layer.

The spray coating layer may be a structure formed by spray coating a mixed powder of NiCr powder mixed with at least one selected from B and Si.

According to the present embodiment as described above, the occurrence of bubbles and defects can be minimized even for a mold having a curved surface, and a uniform laser spray coating layer can be formed.

In addition, a copper plating layer is formed on both side surfaces of the short-side mold contacting with the long-side mold so that the spray coating layer formed on the surface of the short-side mold does not contact the long-side mold so that abrasion of the long side mold due to friction with the short- do.

Thus, the abrasion resistance of the performance mold is increased, and the life of the mold can be maximized.

1 is a schematic perspective view showing a mold according to the present embodiment.
2 is a schematic view showing a state in which a coating layer is formed on a mold according to the present embodiment.
3 is a schematic view showing a cross section of a mold manufactured according to this embodiment.
FIGS. 4 and 5 are diagrams comparing the abraded state of the mold manufactured according to the comparative example and the example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. 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 invention. Accordingly, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Hereinafter, the mold of the performance equipment according to the present embodiment will be described by taking a chamfer mold as an example. The present embodiment is not limited to a chamfer mold, and is applicable to a performance equipment mold having various types of surfaces.

FIG. 1 shows a mold according to the present embodiment, and FIG. 2 shows a state in which a coating layer is formed on a mold according to the present embodiment.

The chanfered mold 10 of this embodiment has a long side mold 12 having a relatively long length and a short side mold 14 having a relatively short length according to the length in the width direction perpendicular to the direction in which the molten metal travels ). Two long-edge molds 12 and two end-section molds are arranged in a rectangular shape to form the chamfered mold 10. The short side mold 14 is disposed between the two long side molds 12 so that both side surfaces thereof are in contact with the inner surface of the scene mold. The chamfered mold has a structure in which both end sides of the short side mold 14 are projected obliquely.

2, a flat portion of the surface of the short-side mold 14 in contact with the molten metal is referred to as a flat surface 16, and a portion projecting obliquely is referred to as an inclined surface 18, 12 are referred to as side surfaces 20, respectively. Further, a portion between the plane surface 16 and the inclined surface 18 is referred to as a connection portion 22. The connecting portion can be understood as a certain region including a boundary line between a plane and an inclined plane.

Here, the coating method of the present embodiment includes a step of melt-cooling the coating powder using a laser to form a spray coating layer 30 on the surface of the short side mold 14 of the chamfered mold 10.

In addition, the coating method may further include forming an Ni plating layer (see 32 in FIG. 3) on the surface of the mold before forming the spray coating layer 30. By forming the Ni plating layer, the effect of preserving the bonding force between the short-side mold 14 as the base material and the spray coating layer can be enhanced.

The step of forming the Ni plating layer on the surface of the short-side mold 14 prior to the formation of the spray coating layer uses an electroplating process, and a detailed description thereof will be omitted since a number of techniques have already been disclosed.

The Ni plating layer 32 may have a thickness of 1 to 2 mm. If the thickness of the Ni plating layer exceeds 2 mm, the possibility of peeling is high. If the thickness is less than 1 mm, the Ni plating layer may be removed by working.

2, the laser irradiation process includes a laser generator 100 for generating a laser, a laser coating head 200 for forming a spray coating layer 30 on the mold by supplying a powder for coating and focusing the laser, ). &Lt; / RTI > The laser coating head 200 includes a nozzle for supplying powder for coating, and a laser penetration portion to which a laser is irradiated. The coating powder is melted by the laser passing through the laser penetration portion to form a spray coating layer.

The laser generating apparatus 100 may include a diode laser, a fiber laser, a CO2 laser, a YAG laser, or the like. In this embodiment, the laser generating apparatus can irradiate a laser with an output of 1 to 8 kW. When the output of the laser is low, the input heat source is low, so that melting of the base material and melting of the incoming powder are difficult. When the output is high, the heat is large in the copper plate and reflected energy is high. Problems can arise. In this embodiment, the wavelength of the laser may be 950 to 1000 nm. Since the wavelength region of the laser includes an absorption region of the metal, the material usable as the base material can be diversified in the case of the laser spray coating.

In this embodiment, the shape of the laser beam may be a rectangular shape so as to uniformly heat the surface and provide a uniform energy source at the position where the powder is introduced to uniformly coat the powder. The laser beam can be used in various sizes ranging from 1 to 6 mm in length and 3 to 24 mm in width. For example, the laser beam may have a rectangular shape with a length of 4 mm and a length of 4 mm. Conventionally, a round laser beam is used. However, in such a structure, melting of the powder formed on the side of the circular beam is not uniform and there is a problem that the uniformity is low with respect to the movement of the laser beam in the horizontal direction.

In the present embodiment, the coating powder may be a NiCr powder mixed with at least one selected from B and Si.

In the present embodiment, the NiCr powder is a powder in which 7.5% of Cr is added to Ni.

The B may be mixed in an amount of 1 to 3% by weight based on the coating powder. The B bonds with Cr, Fe, Ni, etc. in the matrix of the powder to form borides. The boride thus formed serves to increase the hardness. However, when the amount of B is out of the above range, cracks and other coating layer defects are generated through borides having different thermal expansion coefficients and lattice constants.

The Si may be mixed at 2 to 5 wt% with respect to the coating powder. If the mixing amount of Si exceeds the above range, the melting point of the metal is lowered.

As described above, by mixing B and / or Si with the coating powder and spray coating, the hardness of the boride system can be increased without hardening the cemented carbide to improve the hardness, and the hardness can be increased.

The size of the powder may be 45-150 탆. When the diameter of the powder is smaller than 45 탆, the size of the particles is small, causing a problem in supplying and transporting the powder, and clogging of the head or nozzles of the laser equipment occurs. When the diameter of the powder is larger than 150 mu m, it is difficult for the powder to uniformly melt by the laser heat source.

The coating powder prepared as described above is supplied to a laser spray coating apparatus. The laser spray coating apparatus melts powder for coating with a laser. The metal powder is melted by the laser generated in the laser generator to form a spray coating layer on the Ni plating layer of the mold. The Ni plating layer has properties that the Ni plating layer is well adhered to the surface and is not peeled off regardless of the thermal conductivity of the mold of the copper material. The interface between the Ni-plated layer and the NiCr-based coating layer also melts a part of the Ni layer where the laser source is first plated and melts the powder to form an intermetallic compound layer, thereby preventing peeling of the spray coating layer by the laser.

In this embodiment, the NiCr alloy contains intergranular diffusion particles such as B and Si, and is melted by a high-temperature heat source to form CrC. That is, the laser heat source melts the base material and melts and coagulates the NiCr, and the coagulated structure forms CrC particles in the Ni material. In the conventional Ni plating, there is only an increase in hardness due to Ni in terms of the enamel hardness, but in the case of this embodiment, Cr forms CrC, which causes Cr carbide formation and hardness increase in the Ni base alloy. Conventionally, NiCr spray coating can be applied, but since the sprayed coating particles are weak in shear stress, the coating layer is peeled off. Therefore, complicated processes such as fusing treatment after spray coating are required. However, in the case of this embodiment, it is possible to improve the bonding force with the base material through the laser spray coating and to remove defects such as pores existing in the coating layer through the melting and re-solidifying process.

Also, since the surface temperature of the mold during the performance is 350 ° C or higher on average, it is important that the hardness of the mold surface is maintained at 350 ° C or higher. In addition, since the role of the copper plate is to conduct heat from the surface of the mold so that the solidification of the cast steel becomes uniform, it is important to keep the thickness thin and constant so that the coating layer on the mold surface does not become a barrier of thermal gradient . With respect to these required characteristics, conventionally Ni plating or NiB plating has a high room temperature hardness but a low temperature hardness of 350 deg. C or more. That is, in Ni plating or NiB plating, the hardness of the surface due to the thermal curing sharply decreases as the temperature rises, and abrasion resistance sharply decreases at high temperature.

On the other hand, according to the present embodiment, the spray coating layer formed by laser spray coating of a coating powder containing intergranular diffusion particles such as B, Si and the like to a NiCr alloy has a low hardness lowering rate with increasing temperature, Can be greatly improved. In addition, as mentioned above, wear resistance can be improved by strengthening particles such as CrC by adding elements such as Cr and B.

In the coating process of the present embodiment using the laser, the step of forming a spray coating layer on the surface of the end surface mold includes the steps of forming a spray coating layer on the plane of the short side mold, forming a spray coating layer on the side surface of the short side mold, And forming a spray coating layer along the connection between the flat surface and the inclined surface.

In addition, when forming the spray coating layer at the connection portion between the plane of the short side mold and the inclined plane, the spray coating layer may be formed by irradiating only the laser without supplying the coating powder.

When the spray coating layer is formed on the surface of the end surface mold, the coating powder supplied to the inclined surface and the solution melted by the laser flow down along the inclined surface during the process of coating the inclined surface after the flat coating. Since the connection portion with the plane is located below the inclined surface, the coating powder and the solution are collected at the connection portion. Therefore, when another coating powder is supplied in the process of forming the spray coating layer on the connection part, the coating powder is excessively supplied to the connection part.

Thus, when the spray coating layer is formed on the curved-shape short-side mold having a flat surface and an inclined surface, the connection between the flat surface and the inclined surface is sprayed without supplying the coating powder finally after forming the spray coating layer on the flat surface and the inclined surface, It is possible to prevent the formation of pores in the spray coating layer and to form a more uniform spray coating layer.

In addition, the coating method of the present embodiment further includes adjusting the irradiation angle of the laser according to the plane or inclined surface position of the mold in the spray coating layer formation step.

The laser facility is such that the supply of the laser heat source and the supply of the powder are directed in the vertical direction, i.e. in the gravitational direction, towards the coated surface. This is related to the supply of powder by gravity and the transport of the laser beam, and spray coating is applied in a direction perpendicular to the coated surface. However, in this embodiment, since the short-side mold used as the base material is made of the same material, the reflected wave is severe due to the nature of the material, so that the laser beam irradiation and the supply angle of the powder are inclined by 2 to 15 degrees. Thus, in this embodiment, when spraying the flat surface and the inclined surface of the short side mold, the spraying layer can be more uniformly formed by controlling the laser beam irradiation and the powder supply angle of the laser equipment according to the angle of each coated surface.

Therefore, even in the case of a short-side mold having an inclined surface other than the above-mentioned plane, a uniform coating layer can be formed as a whole.

In addition, the coating method of the present embodiment may further include the step of forming a plating layer on both sides of the short side mold after forming the spray coating layer.

The plating layer may be a copper plating layer.

The short side mold is disposed between the long side molds of the mold so that both side surfaces of the short side mold are in contact with the inner surface of the long side mold.

As described above, if a thermal spray coating layer is formed on the surface of the short side mold to increase abrasion resistance and the hardness is increased, the inner surface of the long side mold is damaged due to the increase of the hardness of both side portions of the short side mold. That is, the short-side mold moves between the long-side molds when the width of the mold is variable. In this process, both sides of the short-side mold come into contact with the inner surface of the long-side mold and friction occurs. do.

In this embodiment, by plating the both side surfaces of the short side mold contacting with the long side mold as described above to form the plating layer, the inner surface wear of the long side mold can be minimized.

More specifically, the plating layer forming step is performed by first cutting both sides of the short side mold by the thickness of the plating layer. Thus, even if a plating layer is formed later, the entire width of the short side mold can be formed with an accurate dimension.

After cutting both side surfaces of the short side mold, both sides of the short side mold are copper-plated to form a copper plating layer. It is possible to precisely process the plating layer after forming a plating layer on both sides of the short side mold, if necessary.

Fig. 3 shows a cross section of a short side mold having a plating layer formed thereon.

3, the plating layer 40 is formed on both side surfaces 20 of the short side mold 14 so as to protrude outward from the sprayed coating layer 30 through the forming process. Therefore, when the short side mold and the long side mold are joined, the spray coating layer formed on the surface of the short side mold is not in contact with the inner side surface of the long side mold. Only the plating layer formed on both side surfaces of the short side mold is brought into contact with the inner surface of the long side mold.

Accordingly, friction between the plating layer and the long side mold can be reduced when the short side mold is moved, thereby minimizing the wear of the long side mold.

Experimental Example

Continuous casting was carried out using the chamfer mold produced according to this embodiment and the chamfer mold manufactured according to the prior art.

As mentioned in the case of the embodiment, continuous casting was performed using the chamfered mold manufactured according to the manufacturing method of the present invention. In the comparative example, continuous casting was performed using the chamfered mold that was plated according to the conventional method. The continuous casting was performed the same number of times under the same conditions in both the comparative example and the example.

After the continuous casting process, the abrasion of the molds of Comparative Examples and Examples was observed.

Fig. 4 shows a chamfer mold of a comparative example. As shown in FIG. 4, in the comparative example, the coating layer was not properly adhered to the inclined chamfer mold surface, and peeling phenomenon and abrasion were severely generated at the lower end of the mold. Also, it can be seen that the side plating layer of the mold is not properly formed, and bubble formation and defects are generated.

Fig. 5 shows a chamfer mold according to the present embodiment.

As shown in FIG. 5, in the present embodiment, the coating layer is firmly formed on the surface of the inclined chamfer mold, and it is confirmed that there is no wear amount such that the groove shape caused by the laser process is maintained. In addition, it can be seen that no crack is generated at the upper end portion of the inclined surface.

As a result of thorough examination of the abrasion amount of the molds of this embodiment and the comparative example, abrasion of 3 to 5 mm was generated in the comparative example, whereas abrasion amount in the embodiment was in the level of 0.01 to 0.02 mm.

As described above, according to this embodiment, a more uniform and robust coating layer can be formed on the mold having the inclined surface like the chamfer mold, and the wear of the mold can be minimized through the formation of the hard coating layer.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

10: mold 12: long side mold
14: short side mold 16: plane
18: slope 20: both sides
22: connection 30: spray coating layer
32: Ni plated layer 40: Plated layer

Claims

1. A mold coating method for a performance facility, comprising the steps of: melting a coating powder using a laser to form a spray coating layer,
Wherein the mold has a surface in contact with the cast steel forming a plane and a projected sloped surface with respect to the plane,
The spray coating layer forming step includes the steps of forming a spray coating layer on a plane of the mold, forming a spray coating layer on an inclined surface of the mold, and forming a spray coating layer along a connecting portion between a plane and an inclined surface of the mold Mold coating method.

The method according to claim 1,
Wherein the spray coating layer is formed by irradiating only the laser without supplying the coating powder when the spray coating layer is formed at the connection portion between the plane and the inclined surface of the mold in the step of forming the spray coating layer.

3. The method of claim 2,
And forming an Ni plating layer on the surface of the mold before forming the spray coating layer.

The method of claim 3,
And adjusting the irradiation angle of the laser according to the plane or inclined surface position of the mold in the spray coating layer forming step.

5. The method according to any one of claims 1 to 4,
Wherein the mold includes a long side mold and a short side mold provided so that both side surfaces thereof contact the inner surface of the long side mold,
And forming a plating layer on both sides of the short side mold after formation of the spray coating layer.

6. The method of claim 5,
Further comprising cutting both sides of the short side mold by a thickness of the plating layer before forming the plating layer on both side surfaces of the short side mold.

The method according to claim 6,
Wherein the plating layer formed on both sides of the end face mold is a copper plating layer.

The method according to claim 6,
Wherein the coating powder is a NiCr powder mixed with at least one selected from B and Si in the step of forming the spray coating layer.

9. The method of claim 8,
And B is 1 to 3% by weight based on the coating powder.

9. The method of claim 8,
Wherein the Si is mixed at 2 to 5 wt% with respect to the coating powder.

9. The method of claim 8,
Wherein the coating powder has a size of 40 to 150 mu m.

A surface contacting the cast steel forms a plane and a projected inclined surface with respect to the plane,
A Ni plating layer formed on the plane and the inclined surface; and a spray coating layer formed on the Ni plating layer through a laser spray coating process.

13. The method of claim 12,
Wherein the spray coating layer is formed by spray coating a mixture of NiCr powder and at least one selected from B and Si.

The method according to claim 12 or 13,
Wherein the mold includes a long side mold and a short side mold provided so that both side surfaces thereof are in contact with the inner surface of the long side mold, and the short side mold further includes a plating layer formed on both sides of the long side mold, Mold of performance facility.

15. The method of claim 14,
Wherein the plating layer formed on both sides of the short side mold is a copper plating layer.