JP2003320441A - Coating method for continuous casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method for continuous casting mold, which is free from the generation of thermal deformation, and is excellent in wear resistance and adhesion property. <P>SOLUTION: Self-fluxing alloy or a coating material obtained by mixing the self-fluxing alloy with a carbide is thermally sprayed or powder layered on the inner wall surface of the continuous casting mold. The coating material is irradiated with a laser beam having a wavelength of 630 to 940 nm, energy density of at least 10 kW/cm<SP>2</SP>and is subjected to a remelting treatment to form a coating layer. Preferably, the shape of the surface irradiated with the laser light is rectangular with the short side of 0.1 to 1.0 mm and the long side of 4 to 20 mm or elliptic. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold coating method for improving the life of a mold for continuously casting steel.

[0002]

2. Description of the Related Art The base material of a continuous casting mold for steel is made of copper,
As it is, the abrasion of the slab and powder will be severe. Therefore, Ni-based or Co-based plating is usually applied as a measure against wear, but the hardness is lower and the wear resistance is insufficient as compared with the thermal spray coating, and there has been a demand for life extension. In particular, since the lower part of the mold is heavily worn, application of a Ni-based self-fluxing alloy has been studied as a countermeasure against wear.
As described in Japanese Patent Publication No. 750, since a self-fluxing alloy is generally subjected to remelting treatment (fusing) at a high temperature after thermal spraying, thermal deformation of the base material of the mold is increased, and the treated copper plate is used as a mold. As a result, in the case of a slab continuous casting mold, it cannot be applied to the long side, and only the short side is applied.

The remelting treatment is usually carried out by heating the sprayed coating with the flame of a gas burner, but in this method, oxidative deterioration of the coating is a problem in addition to the above thermal deformation. Also, when covering a large area with a gas burner,
The heating state is likely to be non-uniform, and the occurrence of a portion where the adhesion strength of the coating film is insufficient and the occurrence of pinholes are also problems. Furthermore, since the coating thickness after remelting tends to be uneven, a method of forming a sprayed film thicker than the required film thickness and then grinding is generally performed, resulting in poor yield of sprayed material and increased construction cost. There was also the problem of doing.

As a measure against the above problem, for example, Japanese Patent Laid-Open No. 8-
No. 225917, JP-A-8-187554,
As disclosed in JP-A-9-228071, a self-fluxing alloy is supersonic flame sprayed (remelting treatment omitted), or WC-NiCr, WC-Co, CrC-Ni.
A method of applying Cr by supersonic flame spraying is provided.

Further, as a means for preventing oxidative deterioration of the sprayed coating during the remelting treatment, as disclosed in JP-A-10-121126, a self-fluxing alloy is coated with an antioxidant and fusing. Method, and JP-A 8-32
As disclosed in Japanese Patent No. 3451, there is also provided a method in which a layer of iron or the like is placed on a base of a self-fluxing alloy and fusing is performed by induction heating. Furthermore, JP-A-11-226
As disclosed in Japanese Patent Publication No. 700, a method of applying an electron beam to a self-fluxing alloy to perform fusing has been proposed.

[0006]

As described above, in order to improve the wear resistance of the continuous casting mold, a self-fluxing alloy is sprayed by supersonic flame and the remelting process is omitted, or W
Although methods of applying C-NiCr, WC-Co, and CrC-NiCr by supersonic flame spraying have been proposed, the adhesion strength of the coatings produced by these methods is about 100 MPa at the maximum, and the coating strength of self-fluxing alloy The film adhesion strength after the remelting treatment is considerably lower than about 300 MPa, and there is a problem of peeling in a short time during use of the mold (specifically, physical peeling accompanied by abrasion or peeling accompanied by galvanic corrosion).

For the purpose of preventing oxidative deterioration of the coating film obtained by spraying and remelting the self-fluxing alloy, as described above, a method of applying an antioxidant to the self-fluxing alloy and fusing it, and ironing the base of the self-fluxing alloy. Although a method of fusing by induction heating with a layer such as the above has been proposed, it cannot prevent thermal deformation during remelting treatment. In addition, the method of applying an electron beam to a self-fluxing alloy to perform fusing needs to be performed in a high vacuum, the equipment is large-scale, the cost is high, and it is difficult to confirm the finished state during processing and adjust the heat input amount. There is a problem that is.

The present invention is not limited to the short side of a copper mold,
An object of the present invention is to provide a method for coating a continuous casting mold capable of forming a remelted film of a self-fluxing alloy having good wear resistance and adhesiveness without causing thermal deformation even on the long side.

[0009]

The gist of the present invention is as follows. (1) The inner wall surface of a copper mold is spray-coated with a self-fluxing alloy, and then the coated surface is irradiated with laser light having a wavelength of 630 to 940 nm and an energy density of at least 10 kW / cm ² to remelt the self-fluxing alloy. A coating method for a continuous casting mold, which comprises forming a coating layer after the treatment. (2) Laminating self-fluxing alloy powder on the inner wall surface of a copper mold, and then irradiating the laminating surface with laser light having a wavelength of 630 to 940 nm and an energy density of at least 10 kW / cm ² to remelt the self-fluxing alloy. A coating method for a continuous casting mold, which comprises forming a coating layer after the treatment. (3) In the above (1) or (2), the inner wall surface of the copper mold is coated or laminated with a deoxidizer as a base treatment, and a self-fluxing alloy is spray-coated or laminated thereon. A method for coating a continuous casting mold. (4) The shape on the irradiation surface of the laser beam has a short side of 0.1.
The coating method for a continuous casting mold according to any one of (1) to (3) above, wherein the coating method is a rectangle or an ellipse having a length of ˜1.0 mm and a long side of 4 to 20 mm. (5) The self-fluxing alloy is a Ni-, Co-, or Fe-based self-fluxing alloy, or a chromium carbide, a tungsten carbide, a vanadium carbide, a niobium carbide, or a self-fluxing alloy of these.
The method for coating a continuous casting mold according to any one of (1) to (4) above, wherein one or more zirconium carbides are added. (6) Ni, Co, Fe plating layer or an alloy plating layer having these as a base material, or Ni on the inner wall surface of the copper mold
Alternatively, any one or two of brazing materials of Cu-Ni alloy
The method for coating a continuous casting mold according to any one of (1) to (5) above, wherein a copper mold of the base material is formed with at least one kind of coating layer.

A feature of the present invention is that the self-fluxing alloy film coated on the continuous casting mold has a wavelength with a high energy density and a high energy absorption rate with respect to the film material, that is, a wavelength 63.
By irradiating with a laser beam of 0 to 940 nm, the remelting process is efficiently performed in a shorter time. Since the surface layer of the film is selectively heated by the laser light, heat transfer to the deep portion of the base material is small, and the heat effect and thermal deformation of the base material can be prevented. Also, since the heating time is short, oxidative deterioration of the film can be prevented. If a small semiconductor laser device that emits a laser beam of this wavelength is installed in the feeding device and scanning is performed while keeping the laser output and feeding speed constant, a uniform remelted film can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram of the present invention. A self-fluxing alloy coating 2 is formed on the surface of a continuous casting mold 1 by thermal spraying, and laser light 4 emitted from a laser device 3
Is irradiated on the coated surface for remelting treatment.

The laser device 3 is attached to the feeding device,
It is preferable to scan the coating surface while maintaining a constant distance from the coating material surface at a constant speed. Here, the distance between the laser device and the covering material is set to be equal to or close to the focal length of the laser. In addition, the feed rate and the bead interval for each pass are experimentally determined according to the material of the coating material and the energy density of the laser light so that a remelted film having optimum adhesion strength, porosity, and hardness can be obtained. To be

As a coating method of the self-fluxing alloy, other than thermal spraying,
A method of laminating self-fluxing alloy powder can also be adopted. In this case, when the self-fluxing alloy powder layer is irradiated with laser, multiple reflection of laser light occurs in the powder layer, and heating efficiency at the time of remelting of the coating is further improved. With this method, although the porosity of the coating is slightly higher than that of thermal spraying, the coating can be formed in a short time and at low cost.

When the self-fluxing alloy powder is laminated, if a deoxidizing agent is applied or if the deoxidizing agent is mixed with the self-fluxing alloy powder and laminated, the adhesion strength with the mold base material during remelting treatment is further improved. And the porosity of the coating is also reduced. As the deoxidizing agent, powders of boric acid, silicic acid, magnesium oxide, calcium oxide and the like, and those diluted with a solvent such as anhydrous alcohol are used.

An example of an embodiment according to the present invention is shown in FIG. The self-fluxing alloy coating 2 of the present invention is applied to the lower part of the continuous casting mold 1. On the other hand, the upper part of the mold is a portion located near the molten metal surface during casting, in which thermal cracking is more dominant than wear in terms of life, and a plating layer 5 having higher toughness than self-fluxing alloy coating is applied. To be done. The plating layer material is Ni, C
O-Ni, Ni-W, Ni-Co-W plating or the like is used. These coatings 2 and 5 are connected at a position at a predetermined distance below the molten metal surface.

Another example of the embodiment according to the present invention is shown in FIG. The upper part of the mold is the above-mentioned plated layer 5, but the lower part of the mold is a two-layer coating in which the self-fluxing alloy coating 2 is located on the surface of the plated layer 5. For this reason, the plating layer under the mold is thinned by the thickness of the self-fluxing alloy coating and finished so that the entire surface becomes flat after the remelting treatment. The plating layer has a lower thermal conductivity than copper of the template base material, and selectively heats the interface between the plating layer 5 and the self-fluxing alloy coating 2 at the time of remelting treatment with a laser to improve the adhesion strength and to improve the template base material. It is possible to further reduce the thermal influence on the. Further, by selecting a combination of the plating layer 5 containing components of the same system and the self-fluxing alloy coating 2 such as the Ni plating and the Ni-based self-fluxing alloy, the adhesion strength between the layers is further improved and a preferable coating is formed. You can do it. Further, when the self-fluxing alloy is coated, the surface treatment of the substrate surface of the mold, that is, the steps of shot blasting, alkaline degreasing, electrolytic cleaning, application of a deoxidizing agent, etc. can be omitted.

[0017]

EXAMPLE A continuous casting mold 1 having a width of 2500 mm and a height of 900 mm was coated on the lower surface with four Ni-based self-fluxing alloys and a chromium carbide compounded therein. Ni-based SFA
The four types are films having a Vickers hardness of 600 to 800, which are composed of Ni, Cr, B, Si and the like. Gas flame spraying using ordinary oxygen and fuel gas was used as the spraying method for the self-fluxing alloy. The film thickness before remelting treatment was 1 mm. The upper part of the mold was Ni-plated with a film thickness of 0.7 mm except for some examples. The laser device used for the remelting process was a semiconductor laser having a wavelength of 805 nm and a maximum output of 4 kW. The beam shape of the laser light was rectangular, and two types were used: long side 6 mm x short side 0.25 mm and long side 12 mm x short side 0.5 mm. The distance between the tip of the laser device and the coated surface was set to 40 mm in accordance with the focal length of the device. Also, the bead interval when scanning the laser beam during the remelting process is 12 mm for a beam with a long side of 6 mm and 20 mm for a beam with a long side of 12 mm.
The degree was good. Table 1 shows the examples of the present invention and comparative examples in comparison. In Table 1, “SFA” is an abbreviation for self-fluxing alloy.

Examples 1 and 2 are examples in which re-melting treatment with a laser was performed on a coating film sprayed with a Ni-based self-fluxing alloy under various laser irradiation conditions. Examples 3 and 4
In the present invention, the upper part of the mold has a film thickness of 1.7 mm, and the lower part of the mold has a Ni film thickness of 1 mm and a Ni-based self-fluxing alloy of 1 mm is sprayed on the lower part. This is an example in which the re-melting treatment is performed with the laser light. Further, Example 5 is an example in which chromium carbide is mixed with a Ni-based self-fluxing alloy, and Example 6 is an example in which the Ni-based self-fluxing alloy is formed into a powder layer instead of thermal spraying and remelting treatment is performed by laser light. is there.

In Comparative Example 1, the Ni-based self-fluxing alloy was sprayed, but no remelting treatment was carried out. In Comparative Examples 2 and 3, the Ni-based self-fluxing alloy was prepared by high-speed flame spraying.
And a coating in which chromium carbide was mixed therein was sprayed and the remelting treatment was not carried out. High-speed flame spraying is a method that uses oxygen and petroleum to shoot a sprayed powder from a gun at a supersonic speed of 1 km / sec or more and sprays it onto a substrate. It is said that a denser film can be formed than with ordinary gas flame spraying. .

When these coatings were prepared and used in actual continuous casting molds, the coatings of any of the examples have a lower wear than the conventional Ni plating until the copper mold base material is exposed due to wear of the lower part. The life was more than doubled. Further, in the case of the Ni-based self-fluxing alloy containing the chromium carbide of Example 5, the wear life was 3 times or more that of Ni plating. Most of the coating of Comparative Example 1 was peeled off immediately after the start of use. Further, the coatings of Comparative Examples 2 and 3 were inspected after being used for the same period as the wear life of the Ni plating, and as a result, partial peeling occurred, and continuous use was impossible.

[0021]

[Table 1]

[0022]

According to the present invention, it is possible to manufacture a continuous casting mold having a coating layer formed by remelting a self-fluxing alloy coating excellent in wear resistance without causing thermal deformation. . As a result, the life of the mold is more than doubled as compared with the conventional Ni plating, and the cost required for repair or replacement can be significantly reduced. Therefore, it can be said that the present invention has extremely high industrial value.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a coating method according to the present invention.

FIG. 2 is a mold cross-sectional view showing an example of an embodiment according to the present invention.

FIG. 3 is a mold cross-sectional view showing another example of the embodiment according to the present invention.

[Explanation of symbols]

1 Continuous casting mold 2 Self-fluxing alloy coating 3 Laser device 4 laser light 5 plating layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhiro Minanda             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division Nittetsu Technori Co., Ltd.             Search Laser Technology Center (72) Inventor Kouji Ueda             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation             Kimitsu Works, Nippon Steel Hard Co., Ltd.             Production Division Kimitsu Factory (72) Inventor Takeshi Sanae             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation             Kimitsu Works, Nippon Steel Hard Co., Ltd.             Production Division Kimitsu Factory F-term (reference) 4E004 AB02 AB04 AB08

Claims (6)

[Claims] 1. A copper mold inner wall surface is spray-coated with a self-fluxing alloy, and then the coated surface has a wavelength of 630 to 940 nm.
A coating method for a continuous casting mold, which comprises irradiating a laser beam having an energy density of at least 10 kW / cm ² to remelt the self-fluxing alloy and then forming a coating layer. 2. A self-fluxing alloy powder is laminated on the surface of an inner wall of a copper mold, and a wavelength of 630 to 940 nm is formed on the laminated surface.
A coating method for a continuous casting mold, which comprises irradiating a laser beam having an energy density of at least 10 kW / cm ² to remelt the self-fluxing alloy and then forming a coating layer. 3. The continuous according to claim 1 or 2, wherein a deoxidizer is applied or laminated on the surface of the inner wall of the mold made of copper as a base treatment, and a self-fluxing alloy is spray-coated or laminated thereon. Casting mold coating method. 4. The laser light irradiation surface has a rectangular or elliptical shape having a short side of 0.1 to 1.0 mm and a long side of 4 to 20 mm. Item 7. A method for coating a continuous casting mold according to item. 5. The self-fluxing alloy is Ni, Co or Fe.
A base self-fluxing alloy, or one obtained by adding one or more of chromium carbides, tungsten carbides, vanadium carbides, niobium carbides, and zirconium carbides to these self-fluxing alloys. A method for coating a continuous casting mold according to any one of 1. 6. Ni, Co, Fe on the inner wall surface of a copper mold
It is characterized in that a plated layer or an alloy plated layer using these as a base material, or a brazing material of Ni or a Cu-Ni alloy on which one or more coating layers are formed is used as a copper mold of the base material. The method for coating a continuous casting mold according to any one of claims 1 to 5.