JPH10305351A - Mending method of continuous casting mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a mold while securing the quality of casted pieces by removing at least the flaw part or the deformation part of a mold by grinding a continuous casting mold, forming a plating layer over the ground part by electroplating of copper or copper alloy and by applying the plating finish procession. SOLUTION: A mold 2 is dismounted from a supporting frame 3, and then grind and remove the parts by a lathe and the like in a range including the flaw part or the deformation part. When the surface of the mold is plated with nickel and the like, the plating layer of nickel and the like is to be removed form at least in a range where an electroplating of copper or its alloy is to be applied. After the degreasing treatment, such as solvent degreasing and alkali degreasing, the grinded and removed part of the surface is completed, the electroplating of copper or its alloy is to be started acting as cathode. After the electroplating is finished, the plate layered surface is finish processed to a given shape; the surface of the layer doesn't have projections and depressions at the interface to the surface of the basic mold 2, and the plated surface has to be smooth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a continuous casting mold made of copper or copper alloy, and more particularly to a method for repairing copper or copper alloy by electroforming.

[0002]

2. Description of the Related Art A continuous casting mold apparatus has a structure in which a mold is made of copper or a copper alloy having good conductivity, and the back surface of the mold is cooled with cooling water. Then, the surface of the mold that comes into contact with the molten metal or the slab is subjected to nickel plating or chromium plating as necessary, so that abrasion resistance is enhanced.

In general, a mold for casting a rectangular slab is
For example, as shown in FIG. 1, the mold 2 is configured by combining a pair of opposed long pieces 4 and a pair of opposed short pieces 5 provided inside the long piece 4, and the short piece 5 is During casting, the width of the cast piece to be cast is changed by sliding in the long piece portion 4. When the short piece 5 slides, nicks occur on the surface of the long piece 4 or on the side surface of the short piece 5.

During casting, the surface of the mold is in contact with the molten metal or the slab, while the back surface of the mold is cooled by cooling water, so that the mold 2 receives thermal stress. Furthermore, the thermal stress acts repeatedly because the casting process is intermittent. Therefore, the short piece 5 whose both sides are restrained by the long piece 4 is plastically deformed,
In particular, a gap is formed between the long piece portion 4 in a normal temperature state at the time of non-casting at a meniscus portion where the temperature becomes high. FIG. 5 schematically shows how this gap is formed.

[0005] The deformation due to the thermal stress occurs not only in the above-described combined mold but also in an integrally formed mold such as a tubular form. Generates a narrow cross-sectional area.

[0006] The occurrence of cracks and gaps not only hinders the work of changing the width of the slab, but also causes cracks and gaps in the molten metal to cause breakout,
Further, the narrow cross-sectional area in the mold not only makes it impossible to obtain a slab of a predetermined size, but also causes breakout due to suspension of the solidified shell. Therefore, if the nicks and gaps or the narrowing of the cross-sectional area in the mold exceed the allowable value, the mold cannot be used and the mold needs to be repaired.

[0007] As a method of preventing the occurrence of the oyster flaw,
The JP 58-13446 discloses to form a porous metal layer on the short strip portions aspect, a method of reducing the frictional force by impregnating lubricant such as MoS ₂ on porous in the metal has been disclosed.
With this method, oyster flaws can be prevented, but plastic deformation of the short piece cannot be prevented, and repair of the mold is required.

In the conventional method of repairing a mold, for example, when repairing a gap shown in FIG. 5, a short piece portion is taken along an AA plane and a BB plane.
After grinding and removing to the surface, a method of restoring the short piece to the original width (W) by plating the ground surface with nickel has been performed.
That is, in the conventional method of repairing a mold, the mold is ground and removed until no flaws or deformed portions are present, and then nickel plating or chrome plating is performed as necessary.

Therefore, the thickness or width of the mold is reduced by grinding and removing each repair, and when the thickness or width of the mold becomes less than a predetermined value, the mold is discarded, which increases the manufacturing cost. Had become. Although the thickness or width of the mold can be ensured by nickel plating or chromium plating, nickel or chromium has a lower thermal conductivity than copper, so that its cooling ability is inferior. Therefore, from the viewpoint of cooling the slab, the repair thickness of nickel or chromium is generally up to about 4 mm, and no further repair is performed. Extension was limited.

On the other hand, as a method of producing a mold, a method of producing copper by electroforming is disclosed in, for example, Japanese Patent Publication No. 58-5270. The electroforming method is a name of a method of manufacturing a metal product by an electroplating method, and the method disclosed in the same publication first electrocasts nickel on a matrix, then electroformed copper on a nickel surface, and then This is a method for producing a mold by releasing a mother mold. However, a method for repairing a mold by electroforming copper has not yet been disclosed.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to secure a cooling capacity and repair a mold without reducing the thickness or width of the mold. An object of the present invention is to provide a method for repairing a continuous casting mold that can significantly extend the life of the mold.

[0012]

According to a first aspect of the present invention, there is provided a method for repairing a continuous casting mold, comprising the steps of grinding a continuous casting mold made of copper or a copper alloy to remove at least flaws or deformed portions of the mold. And a step of electroplating copper or a copper alloy on the ground and removed portions to form a plating layer, and a step of finishing at least the plating layer.

[0013] A method for repairing a continuous casting mold according to the second invention is the method for repairing a continuous casting mold according to the first invention, wherein the copper or copper alloy plating layer thickness after finishing is 10 mm or less. It is characterized by the following.

In the present invention, as a first repair step, a flaw or a deformed portion of the mold is ground and deleted. This is because if copper or a copper alloy is electroplated as it is on a flaw or a deformed portion, the adhesion of the plating layer deteriorates.

After grinding and removing the flaw or deformed part of the mold,
As a second step, copper or a copper alloy is adhered to the portion of the mold that has been ground and removed by electroplating. Since the thickness or width of the mold can be restored by depositing copper or a copper alloy, the cooling capacity of the mold does not change. Therefore, it is possible to prevent cracks on the slab surface and cracks in the mold caused by a change in the cooling capacity of the mold, and to use the mold semipermanently by repeatedly forming and repairing the plating layer. . Further, since the adhesion layer is formed by the electroplating method, the adhesion between the adhesion layer and the mold is higher than that of the thermal spraying method or the welding method, and the adhesion layer can be prevented from peeling.

Then, as a third step, a plating layer of copper or a copper alloy is finished. The plating layer has irregularities, and if it is used as it is, the plating layer will wear due to friction with the slab,
This is because there is a fear that flaws may be generated on the slab surface.

Further, in the present invention, it is preferable that the thickness of the plating layer after finishing is 10 mm or less. Because the plating layer is not plastically processed, if the plating layer thickness exceeds 10 mm, the number of times the mold is used is reduced due to wear and buckling of the plating layer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view showing an outline of a slab mold apparatus having a rectangular slab cross section. Hereinafter, the present invention will be described with reference to FIG.

In FIG. 1, a mold apparatus 1 comprises a mold 2 made of copper or a copper alloy and a support frame 3 as main components, and the mold 2 is fixed to the support frame 3 via a plurality of support plates 10. Fixed in position. And mold 2
Is composed of a pair of opposing long pieces 4 and a pair of opposing short pieces 5 which are provided inside and fixed to the long pieces 4. A slit 8 through which cooling water passes is provided on the back surface of the long piece 4 and the short piece 5. In FIG. 1, the slit 8 is partially omitted.

A long piece water box 6 fixed to the long piece 4 with bolts (not shown) is disposed on the back of the long piece 4, and flows into the slit 8 of the long piece 4 from the lower part of the long piece water box 6. The cooling water that has risen in the slit 8 returns from the upper portion of the long piece portion 4 to the upper portion of the long piece water box 6 to cool the long piece portion 4. Similarly, on the back surface of the short piece 5, a short piece water box 7 fixed to the short piece 5 and a bolt (not shown) is installed, and the short piece 5 is cooled by cooling water passing through the slit 8 of the short piece 5. I have. A clamping device 9 is provided to penetrate both ends in the width direction of the long piece water box 6, and the short piece 5 is mounted and fixed inside the long piece 4 by the clamping device 9.

When the mold apparatus 1 is used for continuous casting of a slab, if the surface of the long piece 4 or the short piece 5 has a flaw or the plastic deformation of the short piece 5 becomes large, If a gap is formed between the short piece 5 and the mold 2, the mold 2 is removed from the support frame 3, and at least a region including a flaw or a deformed portion is ground and removed with a lathe or the like. When the surface of the mold is plated with nickel or the like, it is necessary to remove at least a plating layer of nickel or the like in a range where copper or a copper alloy is electroplated. This is because when copper or a copper alloy is plated on a plating layer of nickel or the like, the cooling ability of the mold 2 is reduced.

At this time, if the surface roughness of the ground / removed surface is rough, the adhesion to the plating layer is not good, so the surface roughness of the ground / removed surface is adjusted to 6.3S according to JIS-B0601.
It is preferable to set the following.

It is preferable that the long piece water box 6 and the short piece water box 7 are ground and removed without being separated from the long piece 4 and the short piece 5, respectively. When the long piece portion 4 and the short piece portion 5 that have been subjected to thermal strain due to thermal stress are separated from the long piece water box 6 or the short piece water box 7, respectively, they are released from the restrained state and become significantly deformed. Is increased, or, in the worst case, cannot be reused due to deformation.

Then, after the polished and removed surface is degreased by solvent degreasing, alkali degreasing, etc., the long piece 4 or the short piece 5
Is used as a cathode to start copper or copper alloy electroplating.
In the area where the electroplating is not performed, a masking material of a non-conductive material such as vinyl chloride is applied in advance to prevent the plating layer from adhering. The plating bath may be a conventional bath such as a copper sulfate bath, a copper pyrophosphate bath, or a copper bronze bath.

Generally, the mold 2 is made of pure copper or a copper alloy containing chromium or beryllium. Plating layer to mold 2
When the composition is the same as that of the mold 2, the material test values such as thermal conductivity, tensile strength, and elongation are the same as those of the mold 2, and the life of the mold 2 is extended. Pure copper or a copper alloy having a different composition may be used. However, in this case, it is necessary to consider that the life of the mold 2 may be slightly reduced.

Further, in order to enhance the adhesion of the plating layer, it is preferable to wash the ground / removed surface of the mold 2 with hydrochloric acid or the like after the degreasing treatment, and to activate it with a strong acid. The activation treatment of the strong acid may be performed, for example, by immersing the ground / removed surface in an aqueous solution in which sulfuric acid and nitric acid are mixed and the acid content is 50% by volume or more.

After the completion of the electroplating, the plating layer is finished to a predetermined shape. During casting, the mold 2 and the slab come into contact. At that time, in order to prevent the abrasion of the plating layer and the generation of scratches on the surface of the slab due to friction, the surface of the plating layer has no irregularities at the interface with the surface of the original mold 2 and the surface roughness of the plating layer is low. Must be smooth. Normally, since the inner surface of the mold 2 is mirror-finished, the plating layer also has a surface roughness of JIS-B060.
It is preferable to perform mirror finishing of 0.8 S or less according to the definition of 1.

The mold 2 thus repaired is placed on a support frame 3
And put it into practical use.

[0029]

【Example】

Example 1 An oyster flaw generated on the surface of the long piece illustrated in FIG. 1 was repaired by the present invention. The long piece is made of a chromium-containing copper alloy and has a width of 2400 mm, a length of 800 mm, and a thickness of 6 mm.
0 mm, slits of 10 mm width and 25 mm depth are cut on the back surface at a pitch of 20 mm. This continuous casting machine is of a vertical bending type, and the mold has a vertical shape, and nickel plating having a thickness of 4 mm is applied to the lower half of the long piece in a range of 400 mm.

As shown in FIG. 2, this long piece is 4 mm in the casting direction, 20 mm in the width direction, and 3 mm in depth at a position 150 mm from the upper end of the long piece and 500 mm from the side face of the long piece.
Oyster scratches occurred. This long piece is removed from the support frame with the long piece water box attached, and 140 m from the top of the long piece.
m to 160 mm over the entire width at a depth of 4 mm (Fig. 2
(The range of the shaded area shown in the figure)) Grinding and removing, surface roughness is 6.3
It processed to below S.

After processing, degreasing is performed, and the hydrochloric acid concentration is reduced to 10
The solution was pickled with a volume% aqueous solution, then immersed in an acid containing 60% by volume of sulfuric acid and nitric acid for 1 hour to perform an activation treatment, and then electroplated with pure copper. The conditions for electroplating are shown below. A masking material of vinyl chloride was applied to the surfaces other than the ground and removed surfaces.

Copper plating conditions Plating bath Copper sulfate 200 g / l Sulfuric acid 50 g / l 2. Plating conditions Cathode current density 5A / dm ² Bath temperature 20-23 ° C Stirring Cathode rocker air stirring

When the plating layer exceeded 5 mm, the electroplating was finished, and the plating layer was ground until the plating layer had the same thickness as the original mold, and mirror-finished with a surface roughness of 0.8 S or less.
This long piece was attached to a mold apparatus and used for casting. The amount of wear of the electroplated layer was exactly the same as the amount of wear of the unplated mold part, and the obtained slab had a sound quality with no surface flaws.

[Embodiment 2] The present invention is applied to repair of a short piece illustrated in FIG. The short piece is made of copper alloy containing beryllium, width 250mm, length 800mm, thickness 60m
m, slit of width 10mm, depth 25mm is 20mm
Engraved on the pitch. As in the case of the first embodiment, a vertical mold apparatus was used, and a plating layer of nickel or the like was not applied to the short pieces.

During use of the short piece, a gap of 2 mm was generated between the short piece and the long piece of the meniscus portion. The short piece was removed from the mold apparatus with the short piece water box attached, and both side faces were 3 mm wide. Grinded and removed over the entire length.

After the ground / deleted surface was finished to have a surface roughness of 6.3S or less, it was degreased, and then electroplated with pure copper on both sides. The conditions for the electroplating were the same as in Example 1, except that a masking material of vinyl chloride was applied except for the plating surface.

Electroplating is completed when the plating layer exceeds 4 mm on both the left and right sides, and the surface of the mold contacting with the slab is ungrounded until the entire surface of the mold portion is ground and removed by 0.2 mm. And the plating layer were ground and removed, and then a mirror finish with a surface roughness of 0.8 S or less was performed. Next, the plating layer on the side surface was ground and removed to obtain a short piece having a width of 250 mm with a plating layer having a thickness of 3 mm adhered to the left and right side surfaces as shown in FIG.

Then, the short piece was mounted on a mold apparatus and used for casting. The amount of wear of the plated layer during use was exactly the same as the amount of wear of the mold portion where no plating was applied, and the obtained slab was also of a sound quality with no surface flaws.

FIG. 4 is a diagram showing the results of an investigation on the effect of the thickness of the plating layer on the number of times of using the short piece unit in units of one heat in the embodiment in which the thickness of the plating layer on one side was repaired to 14 mm by the above method. is there. No buckling or abrasion occurred up to a plating layer thickness of 10 mm, and the same number of uses as the solid short piece could be achieved.

[0040]

According to the present invention, a mold made of copper or copper alloy is repaired by providing an adhesion layer of copper or copper alloy by an electroplating method, so that the cooling ability of the mold is not changed.
In addition, since the mold can be repaired without reducing the thickness or width of the mold, the life of the mold can be greatly extended while ensuring the quality of the slab.

[Brief description of the drawings]

FIG. 1 is a plan view showing an outline of a slab mold apparatus having a rectangular slab section to which the present invention is applied.

FIG. 2 is a diagram schematically showing a position of an oyster flaw generated in a long piece portion in Example 1 and a portion of plating repair.

FIG. 3 is a view schematically showing a short piece after repair in Example 2.

FIG. 4 is a diagram showing the results of an investigation on the effect of the thickness of a plating layer on the number of use of short pieces in Example 2.

FIG. 5 is a view schematically showing a gap formed between a short piece and a long piece of a meniscus portion in a mold apparatus having a rectangular cast slab cross section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold apparatus 2 Mold 3 Support frame 4 Long piece part 5 Short piece part 6 Long piece water box 7 Short piece water box 8 Slit 9 Clamping device 10 Support plate

Claims (2)

[Claims] 1. A step of grinding a continuous casting mold made of copper or a copper alloy to remove at least flaws or deformed portions of the mold, and electroplating copper or a copper alloy on the ground and removed portions. A method for repairing a continuous casting mold, comprising: a step of forming a layer; and a step of finishing at least the plating layer. 2. The method for repairing a continuous casting mold according to claim 1, wherein the thickness of the plating layer of copper or copper alloy after finishing is 10 mm or less.