JP2002332599A - Descaling method for metallic strip material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a descaling method for a metallic strip material which uses an electrolyte not containing a nitric acid and is capable of performing sufficient descaling treatment. SOLUTION: The metallic strip material W containing any among Fe, Ni, Ti and Cu as an essential component is immersed into the aqueous electrolyte L containing a hydrofluoric acid and sulfuric acid. Electric current is passed through the aqueous electrolyte L between an electrode 43 immersed into the aqueous electrolyte L and the metallic band material W while the polarity of the electrode 43 is inverted at prescribed periods. Gaseous hydrogen and/or gaseous oxygen is generated by this energization and the surface of the metallic band material W is subjected to electrolytic descaling treatment by the bombardment by the gas. Further, the current density of the current to be passage to the electrode 43 is regulated to >=30 A/dm<2> is addition thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for descaling a metal strip.

[0002]

2. Description of the Related Art Conventionally, in a method of manufacturing a metal member such as a metal wire or a metal strip, a descaling process is performed to remove scale and dirt generated on the surface of the metal member by hot rolling, heat treatment or the like. ing. If such a scale layer is formed on the surface of these metal members, the subsequent steps will be adversely affected. Therefore, it is preferable to remove the scale layer as much as possible. As a descaling process for such a metal member, a descaling process using an aqueous solution containing hydrofluoric nitric acid has been conventionally performed.

However, when the above-mentioned aqueous solution containing hydrofluoric acid is used, since the nitric acid contains a nitrogen component, the pickling waste liquid after descaling treatment contains the nitrogen component.
When the pickling waste liquid containing nitrogen is discharged, there is a problem in that the ocean, rivers, lakes and marshes are eutrophic by nitrogen. Therefore, in recent years, the regulation of the content of nitrogen contained in the waste liquid has been strengthened, and even in the surface cleaning line of metal wires and metal strips, to reduce the nitrogen contained in the pickling waste liquid, There is an increasing demand for surface cleaning technology that uses as little nitric acid as possible.

[0004]

As a surface cleaning technique that uses as little nitric acid as possible, for example, Japanese Patent Laid-Open No.
A method for descaling an iron-based wire disclosed in Japanese Patent No. 38700/38 can be exemplified. In this method, an aqueous solution containing hydrofluoric acid and sulfuric acid is used as an electrolytic solution to remove the scale layer formed on the surface of the iron-based wire. That is, the wire is immersed in the electrolytic solution to perform electrolytic descaling. According to the above method, since an aqueous solution containing no nitric acid is used as the electrolytic solution, the influence on the environment is not so much a concern. However, in an Fe-Ni alloy strip used for applications such as a lead frame, a shadow mask, or a permalloy, a Ni-enriched layer is generated in the scale, it is difficult to descaling, and an aqueous solution containing hydrofluoric nitric acid is used. Pre-treatment such as shot blasting was also required in descaling using. However, when the shot blasting treatment is performed, irregularities are generated on the back surface of the metal strip, which adversely affects the quality of the back surface at the time of cold rolling as a subsequent process.

An object of the present invention is to provide a method for descaling a metal strip using an electrolytic solution containing no nitric acid and capable of performing a sufficient descaling treatment. Further, F
An object of the present invention is to provide a descaling method capable of descaling an e-Ni alloy without performing a pretreatment such as a shot blast treatment.

[0006]

In order to solve the above-mentioned problems, a method for descaling a metal strip according to the present invention comprises adding a Fe, N, or A solution to an aqueous electrolyte containing hydrofluoric acid and sulfuric acid.
A metal strip containing any one of i, Ti and Cu as a main component is immersed, and a current is applied between the electrode immersed in the aqueous electrolyte and the metal strip via an aqueous electrolyte. By generating hydrogen gas and / or oxygen gas,
A method for electrolytic descaling a surface of a metal strip by the impact of the gas, wherein a current density of a current passed between the electrode and the metal strip is 30 A / dm ² or more. .

The aforementioned JP-A-12-38700 discloses a descaling method for an iron-based wire (hereinafter, also simply referred to as a wire). This method is intended to perform descaling treatment on a wire without using nitric acid which is not desirable from the viewpoint of environmental protection. In addition, in this publication, the hydrogen gas and / or oxygen gas generated by energizing the aqueous electrolyte is repeatedly generated or released in the vicinity of the scale layer, so that the scale layer is removed by the impact. There is a description. Accordingly, a method of removing a scale layer formed on the surface of a metal member by gas impact has been known. Further, according to the publication, in an iron-based wire, a current density of 10 A is used to remove a scale layer formed on the surface of the wire.
It is sufficient if a current of about / dm ² is passed through the aqueous electrolyte.
It is described that not only a remarkable effect is not obtained even when the current density is 30 A / dm ² or more, but also that the production cost is increased. As described above, this publication discloses only the range of the current density suitable for the case of using only the iron-based wire rod.

[0008] Here, the present inventors have described the descaling method of iron-based wires described in the above-mentioned publications as Fe, Ni, Ti.
When applied to a metal band containing either one of Cu and Cu as a main component (hereinafter also simply referred to as a metal band), the scale layer could not be sufficiently removed. As a result of investigations by the present inventors, it is considered that the reason why the descaling treatment is not sufficiently performed is that the surface area of the metal strip is considerably larger than that of the wire. If the surface area is large, the formation amount of the scale layer formed on the surface also increases,
It is considered that the descaling method similar to the case of the wire does not sufficiently remove the scale layer.

[0009] The present inventors, when employing the electrolytic descaling treatment in the method of descaling an iron-based wire disclosed in the above-mentioned publication for a metal strip, can remove the scale layer by increasing the amount of generated gas. The knowledge that it is performed more effectively was obtained. Then, in the case of a metal strip, it has been found that descaling treatment on the surface of the metal strip is preferably performed by generating an appropriate amount of gas.

When a current is passed through the aqueous electrolyte, an oxidation / reduction reaction occurs in the vicinity of the scale layer based on the components constituting the scale layer. Then, a hydrogen gas and / or an oxygen gas are generated by a hydrolysis reaction (or an electrolysis reaction of water) accompanying the oxidation / reduction reaction. And
The present inventors take advantage of the fact that if the current density of the current passed through the aqueous electrolyte solution is increased, the amount of generation of the hydrogen gas and / or the oxygen gas is increased. A range of current density suitable for generating an amount of gas capable of performing a proper descaling process was found. Specifically, 30 A / d is required to generate an amount of gas necessary to sufficiently remove the scale layer formed on the surface of the metal strip.
It is effective to employ a current density of m ² or more. When the current density is less than 30 A / dm ² , the amount of hydrogen gas and / or oxygen gas generated from the aqueous electrolyte does not reach the level at which the scale layer formed on the surface of the strip is removed. Desirably, when the current density is 50 A / dm ² or more, a better descaling process is realized.
On the other hand, an excessive increase in the current density is not preferable because the metal strip generates heat. In order to suppress the heat generation of the metal strip, it is preferable to keep the current density at 200 A / dm ² or less.

Further, by setting the current density to 30 A / dm ² or more, it is possible to remove most of the scale layer of the metal strip only by the electrolytic descaling treatment. Therefore, when the metal strip is to be transported along the transport path, after performing at least one of the hot rolling treatment and the heat treatment on the transport path, without performing preliminary cleaning,
It is also possible to carry in the metal strip continuously into the aqueous electrolyte to perform electrolytic descaling. It is to be noted that, when the metal strip is conveyed in a form subjected to at least one of a hot rolling treatment and a heat treatment, a strong and thick scale layer is usually formed on the metal strip. In the present invention, it is possible to remove the scale layer even from a metal strip on which such a strong and thick scale layer is formed, and it is also possible to omit the preliminary cleaning.

Conventionally, for example, in a descaling method for an iron-based wire as described in the above-mentioned publication, a preliminary cleaning is performed on the wire before performing an electrolytic descaling treatment. The pre-cleaning dissolves the scale layer in advance and makes the subsequent electrolytic descaling process much easier. However, this process has disadvantages such as an increase in the overall processing time and the necessity of separately providing a processing tank for performing pre-cleaning. In the present invention, such disadvantages hardly occur, and there is an effect that the process can be simplified and the manufacturing cost can be reduced.

Further, by inverting the direction of current flow in the electrode at a predetermined cycle, the effect of removing the scale layer by the generated gas can be further enhanced.
In order to obtain such an effect more remarkably, the frequency (cycle pitch) of reversal of the direction of conduction (reversal of the polarity of each electrode) is preferably set to 5 to 70 times / second, and more preferably. It is good to set to 10 to 30 times / second. By adopting such a cycle pitch, gas generation and
The impact on the scale layer due to the release becomes remarkable, and the descaling treatment can be suitably performed.

The aqueous electrolyte used for the electrolytic descaling treatment contains 0.5 to 10% by mass of hydrofluoric acid and 1 to 40% by mass of sulfuric acid. When the content of these components is less than the above lower limit, descaling on the surface of the metal strip becomes insufficient. Further, if any of the above components is excessively contained, the descaling treatment may not be sufficiently performed similarly, or when the content of these acid components becomes extremely large, In some cases, the surface condition of the metal strip deteriorates due to acid corrosion. The aqueous electrolyte is more preferably
It is preferable to use one containing 3 to 6% by mass of hydrofluoric acid and 10 to 25% by mass of sulfuric acid. Furthermore, since such an aqueous electrolyte does not use nitric acid, there is no need to worry about eutrophication of the environment such as oceans, rivers and lakes.

The present invention also relates to Fe, Ni, Ti and C
It can be suitably applied to a metal strip containing any of u as a main component. Among these, Fe
-Ni-based alloy, stainless steel, titanium alloy, pure Ni, C
In a metal strip composed of a u-Ni alloy or the like,
The present invention can be suitably applied. In particular, conventionally, it is relatively difficult to remove the descaling layer, and a material containing a larger amount of a Ni component, for example, a metal strip composed of an Fe-Ni alloy, austenitic stainless steel, or the like. In the above, the amount of the scale layer removed by applying the present invention is greatly improved.

Further, the present invention provides a method for manufacturing a semiconductor device having a width of 100 to 1500 m.
The effect is further exhibited by applying the present invention to a metal strip having a thickness of 1 to 10 mm. In the metal strip having the above dimensions, the formation amount of the scale layer formed on the surface thereof is larger than that of a member such as a general wire, for example. For this reason, the current density employed in the conventional descaling method for iron-based wires cannot generate gas sufficient to remove the scale layer. According to the present invention, the amount of generated gas can be set in a suitable range for the metal strip having the above dimensions, and the scale layer can be effectively removed.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the descaling method of the metal strip of the present invention includes a shot blasting step for generating cracks on the surface of the metal strip, and an electrolytic descaling treatment. Then, after performing the electrolytic descaling treatment, the surface of the metal strip is cleaned with a brush, and then the surface of the metal strip is dried. These steps may be performed by continuously transporting the metal strip on the transport path, or may be performed separately instead of being continuously transported.

For example, a metal strip is conveyed to a shot blasting device arranged on a conveying path, and a necessary one is subjected to a shot blasting process. Next, the metal strip is conveyed to the electrolytic descaling device similarly arranged on the conveying path, and the electrolytic descaling treatment is performed. In the electrolytic descaling device, the scale layer of the metal strip is removed, and the scale component adhering to the surface of the metal strip after removal is removed by brushing the surface of the metal strip with a brush. As a brush, for example,
Nylon can be suitably used. After cleaning the surface of the metal strip with a brush, the metal strip is transported to a drying device and dried. Through the above steps, the step of removing the scale layer formed on the surface of the metal strip is completed.

As shown in FIG. 3A, the scale layer 31 before the shot blasting process has a smooth surface, but the scale layer 31 after the shot blasting process.
In this case, a part of the scale layer 31 is shaved by abrasive particles, and cracks 32 and the like are formed on the surface thereof. The aqueous electrolytic solution in the subsequent electrolytic descaling process penetrates into the crack 32, and the descaling effect is enhanced.
In addition, if sufficient electrolytic descaling can be performed without performing the shot blasting, the processing can be omitted.

Further, in the present invention, since the scale layer of the metal strip S is sufficiently removed in the electrolytic descaling process, the preliminary cleaning before the electrolytic descaling process can be omitted. After the shot blasting process, it may be transported to the electrolytic descaling device 4 along the transport route. However, the present invention is not limited to this, and it goes without saying that preliminary cleaning may be performed.

FIG. 1 shows an example of an apparatus for performing an electrolytic descaling process according to the present invention. In the electrolytic descaling apparatus 4, an electrolytic solution tank 41 in which an aqueous electrolytic solution L is stored, a guide roll 43 for holding a metal strip S, and a metal strip S for dipping in the electrolytic solution tank 41. Of the guide roll 42. In the aqueous electrolyte solution L, a plurality of electrodes 43a to 43g are arranged. Hereinafter, these electrodes 43a to 43g are collectively referred to as electrodes 43. These electrodes 43 are arranged along the transport path in such a manner that adjacent electrodes have polarities opposite to each other. That is, the electrodes 43a, 43c, 43
When e and 43g are anodes, the electrodes 43b, 43d,
The wiring of these electrodes 43 is adjusted so that 43f serves as a cathode. Thus, when a current is applied to the electrode 43, the anode (here, the electrodes 43a, 43c, 43
e, 43g), the cathode reduction reaction proceeds on the surface of the metal strip S, and the cathodes (here, the electrodes 43b, 43g)
In the portions d and 43f), the anodic oxidation reaction proceeds on the surface of the metal strip S. The metal strip S is continuously transported between these electrodes 43, and the above-described reaction proceeds alternately in each part of the metal strip S. The electrode 43
Are arranged so as to face the transport surface of the metal strip S (and a surface parallel to the transport surface). The various electrodes 43 are mainly composed of carbon, for example, a material obtained by molding graphite powder into a plate shape and firing it is used, but other materials, for example, noble metals such as platinum and palladium, or It is also possible to use a plate-like base material coated with such a noble metal.

As the aqueous electrolyte L used in the electrolytic descaling treatment, an aqueous solution containing hydrofluoric acid and sulfuric acid, for example, 0.5 to 10% by mass of hydrofluoric acid (preferably 3 to 6%)
Mass%), sulfuric acid is 1 to 40 mass% (preferably 10 to 10 mass%).
25% by mass). The bath temperature of the aqueous electrolyte L is preferably set in the range of 40 to 80C. By setting it in this range, descaling of the metal strip S is easily promoted.

Hereinafter, the outline of the electrolytic descaling process will be described. First, the metal strip S immersed in the aqueous electrolyte L
Current density 3 between the electrode 43 and the aqueous electrolyte L
0 A / dm ² or more (preferably, 50 A / dm ² or more)
Of current. At this time, the metal strip S serves as a cathode at a position facing the anode electrode 43 and serves as an anode at a position facing the cathode electrode 43.

The scale layer 31 is composed of components A and B, such as oxides. Electrode 4
When an electric current is caused to flow through the aqueous electrolyte solution L by the electrode 3, the anode electrode 4
In No. 3, since the metal strip S has a negative polarity as shown in FIG. 1 (b), a hydrolysis reaction by a cathode reduction reaction proceeds on the surface of the metal strip S. As the hydrolysis reaction proceeds, a component A such as an oxide, which forms a scale layer, is reduced and converted into a component A ′ which is solid-soluble in hydrofluoric acid or sulfuric acid constituting the aqueous electrolyte L, and the scale is formed. It is considered that the dissolution of the layer proceeds. By this hydrolysis reaction, the reduction and conversion of the component A proceed, and at the same time,
Hydrogen gas is generated from the surface of the metal strip S.

On the other hand, in the negative electrode 43, the anodic oxidation reaction proceeds because the surface of the metal strip S has a positive polarity as shown in FIG. 1B. As a result, the hydrolysis reaction proceeds similarly, and the component B such as an oxide constituting the scale layer 31 is further oxidized and solid-dissolved in hydrofluoric acid or sulfuric acid constituting the aqueous electrolyte L. Oxidized and converted to B '. At the same time as the conversion of the component B, oxygen gas is generated from the vicinity of the surface of the metal strip S due to the hydrolysis reaction. As described above, the conversion of the components A and B, such as oxides, constituting the scale layer proceeds, and the scale layer is dissolved.

However, in the present invention, the scale layer 3
It is not sufficient to simply convert 1 into a component that is solid-soluble in an acid.
That is, the scale layer 31 formed on the metal strip S
Is formed in a large amount, so that the scale layer 31 is not sufficiently removed only by converting it into a component which is dissolved in an acid.
Therefore, by controlling the polarity of the electrodes 43 alternately at a predetermined cycle pitch, or by transporting the metal band S, the polarity of the surface of the metal band S is reversed. The gas generated by the hydrolysis reaction is repeatedly generated and released, and the components A ′ and B ′ constituting the converted scale layer 31 can be effectively removed from the surface of the metal strip S.

FIG. 2 shows how the hydrogen gas and the oxygen gas remove the converted components A ′ and B ′ constituting the scale layer 31. As shown in FIG. 2A, hydrogen gas and oxygen gas (hereinafter simply referred to as gas G) generated by the above hydrolysis reaction (at this time, the conversion of the scale layer 31 also occurs at the same time) are converted to the scale layer 31. Is in contact with At this time, the polarity of the metal strip S is reversed by reversing the direction of the current supplied to the electrode 43 or by transporting. As a result, FIG.
As shown in (b), the gas G in contact with the scale layer 31 is rapidly released from the scale layer 31. At this time, the components A ′ constituting the squeeze layer 31 converted by the oxidation or reduction reaction due to the impact due to the release of the gas,
B ′ can be removed from the scale layer 31. The components A ′ and B ′ constituting the scale layer 31
Removal occurs in both the inversion of the electrode 43 from the anode to the cathode and the inversion of the electrode 43 from the cathode to the anode.
That is, when the electrode 43 is inverted from the anode to the cathode, the metal strip S is inverted from the cathode to the anode, so that the component B ′ converted by the anodic oxidation reaction is removed by the oxygen gas. On the other hand, when the electrode 43 is inverted from the cathode to the anode, the component A ′ converted by the cathode reduction reaction on the surface of the metal strip S is removed by the hydrogen gas.

When the metal strip S is transported in the aqueous electrolyte L, the transport speed of the metal strip S is set to 10 to 30 m in the transport direction of the electrolytic descaling device for storing the aqueous electrolyte. It is good to be 2-30 m / min. Thus, the descaling process for the metal strip S is sufficiently performed.

[0029]

EXAMPLES The following experiments were conducted to examine the effects of the present invention. First, the width is 200 to 50 by a predetermined rolling device.
A metal strip which was hot-rolled to 0 mm was prepared, subjected to a solution treatment while being conveyed on the conveyance path, and subjected to electrolytic descaling based on the method of the present invention. In some cases, a shot blast treatment (SB) was performed as a pretreatment before the electrolytic descaling treatment. Several kinds of metal strips shown in Table 1 were prepared and used for the experiment. Furthermore, electrolytic descaling treatment was performed under several conditions. Table 2 shows the conditions of the shot blast treatment and the electrolytic descaling treatment. The concentration of hydrofluoric acid and sulfuric acid contained in the aqueous electrolyte was 5% by mass of hydrofluoric acid,
Sulfuric acid: 15% by mass, and the temperature was 50 ° C. Further, the distance between the surface of the metal strip S and the electrode immersed in the electrolytic solution was set to 50 mm. Further, the length of the electrolytic descaling apparatus was set to 20 m, and eight electrodes each having a length of 20 cm were formed at intervals of 150 cm so that the anode and the cathode were inverted from each other.

The descaling layer is removed by generating hydrogen gas and oxygen gas as described above.
Thereafter, by brushing with a nylon brush, the scale component removed by the descaling treatment and attached to the surface of the metal strip is removed, and the metal strip is further washed and dried to remove the surface. The scale condition was visually evaluated. The evaluation method is as follows. A: No scale remaining B: Whitish scale alteration remaining C: Some scale remaining D: Many scale remaining Many evaluation results are shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

According to the above embodiment, in the aqueous electrolyte,
The current density flowing through between the metal strip and the electrode is 30
By setting A / dm ² or more, the scale layer formed on the metal strip S can be effectively removed.
In particular, as the metal strip, Fe, Ni, Ti and Cu
The present invention can be suitably applied to those containing as a main component. Looking at the material types constituting the metal strips, in the case of the Fe-Ni-based alloy, Example N
o. Even without shot blasting as in 2-6, 3
By passing a current having a current density of 0 A / dm ² or more, the scale layer is sufficiently removed. In No. 1, since the current density is less than 30 A / dm ² , the scale layer on the surface of the metal strip is not sufficiently removed. Further, by increasing the current density, the descaling state on the surface after the descaling step is also improved. On the other hand, in the case of pure Ni, Example No.
By setting the current density to about 70 A / dm ² as shown in FIGS. 7 and 8, the scale layer can be sufficiently removed without the shot blast treatment. In the case where a high alloy is used as the metal strip, Example No. 17, 18
And Comparative Example No. Compared with 16 the current density was 30 A
It can be seen that the descaling state is significantly improved by setting the ratio to / dm ² or more. Furthermore, in the case of a Ti alloy, shot blasting is not performed as a pretreatment, and current is not supplied (current density = 0 A / d).
m ² ), a certain degree of descaling state can be obtained, but by passing a current having a current density of 30 A / dm ² or more, the surface state after the descaling treatment can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an electrolytic descaling apparatus in which an electrolytic descaling process is performed in the present invention.

FIG. 2 is a schematic view showing the operation of a descaling process in the present invention.

FIG. 3 is a schematic view showing an effect of a shot blast process on a scale layer.

[Explanation of symbols]

 41 Electrolyte bath 42,44 Guide roll 43 Electrode S Metal strip 32 Crack

Claims (4)

[Claims] 1. An aqueous electrolytic solution containing hydrofluoric acid and sulfuric acid,
A metal strip containing any one of Fe, Ni, Ti and Cu as a main component is immersed, and a current is passed between the electrode immersed in the aqueous electrolyte and the metal strip via the aqueous electrolyte. A hydrogen gas and / or an oxygen gas, and subjecting the surface of the metal strip to electrolytic descaling by the impact of the gas, wherein a current is applied between the electrode and the metal strip. A method for descaling a metal strip, wherein the current density of the current to be applied is 30 A / dm ² or more. 2. The aqueous electrolyte according to claim 1, wherein the hydrofluoric acid is 0.5 to 10%.
The method for descaling a metal strip according to claim 1, wherein the metal strip contains 1 to 40% by mass of sulfuric acid. 3. The metal strip is transported along a transport path, and at least one of a hot rolling process and a heat treatment is performed on the transport path. The descaling method of a metal strip according to claim 1 or 2, wherein the strip is continuously carried into the aqueous electrolytic solution to perform the electrolytic descaling treatment. 4. The method for descaling a metal strip according to claim 3, wherein a plurality of electrodes are provided in the aqueous electrolyte in such a manner that the polarity is alternately reversed along the transport path.