JPH0987900A - Electrolytic pickling method for steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrolytic pickling method capable of suppressing an electric power consumption low and forming uniformly bright surfaces on steel strip surfaces by making the current density distribution in the longitudinal direction of the steel strip surfaces uniform. SOLUTION: An electrolytic cell 3 is provided with a pair of anode electrode plates 5a, 5b arranged above and below the stainless steel strip 1 on a deflector roll 2 side in this cell in three rows along the progression direction of the steel strip 1 and is provided with a pair of cathode electrode plates 6a, 6b arranged above and below the steel strip 1 on a deflector roll 4 side in this cell in three rows along the progression direction of the steel strip 1. The control of the electrolytic current density J(A/dm<2> ) for each of the respective electrode plates 5a, 5b, 6a, 6b is discretely executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic pickling method for removing scale on the surface of steel strip.

[0002]

2. Description of the Related Art As a conventional electrolytic pickling method of this type,
For example, the one shown in FIG. 5 is known. According to this method, a positive electrode plate c and a cathode arranged along a longitudinal direction (traveling direction) of the steel strip b are provided on a stainless cold-rolled steel strip b passing through a tank a filled with a neutral salt electrolyte. The scale on the surface of the steel strip b is removed by applying an electrolytic current through the electrode plate d.

More specifically, the positive electrode plate c is arranged along the longitudinal direction on the upper and lower surfaces of the steel strip b on the upstream side of the steel strip b, while the negative electrode plate d is on the downstream side of the steel strip b. The steel strips b are arranged on the upper and lower surfaces along the longitudinal direction, and a power supply voltage e is applied between the positive electrode plates c, c and between the negative electrode plates d, d. Therefore, the upper and lower surfaces of the steel strip b passing between the positive electrode plates c and c are negatively charged, while the upper and lower surfaces of the steel strip b passing between the negative electrode plates d and d are positively charged. As a result, the current of the power source e becomes an electrolytic current from the positive electrode plate c and flows to the negatively charged portion on the surface of the steel strip b, and then flows to the negative electrode plate d side of the steel strip b to reach the positively charged portion, An electrolytic current flows from the positive charging portion to the negative electrode plate d and returns to the power source e. At this time, the positively charged portion of the steel strip b becomes the anode surface, and the scale on the surface of the steel strip b is chemically removed by the progress of the dissolution of the metal or metal oxide and the generation of oxygen gas due to the chemical reaction on the anode surface. It is supposed to be done.

[0004]

By the way, when electrolytic pickling is applied to a stainless steel strip, the electrolytic current density applied to the steel strip b is increased within a range satisfying conditions such as use of pickling equipment to improve the pickling ability. I am going to the maximum. However, in the above conventional electrolytic pickling method, the upper and lower fixed electrode plates c, c
Since the steel strip b moves between (d, d) and pickling is performed,
When the electrode length is long, as shown in FIG. 6, a so-called gradient current density distribution is generated in which the electrolytic current density has a gradient in the longitudinal direction of the electrode plates c and d (the positive / negative of the current density in FIG. It represents the direction of flow.) In the case of such a gradient current density, on the high density current side, a large amount of current is consumed for the generation of oxygen gas, which results in a waste of current, which deteriorates the power consumption rate.

Further, there is a problem that unevenness in current density distribution due to the gradient current density causes uneven gloss called an electrolytic pattern on the surface of the steel strip b. The present invention has been made in order to eliminate such inconvenience, and it is possible to suppress the electric power consumption to a low level by making the current density distribution in the longitudinal direction of the steel strip surface uniform, and to form a uniform glossy surface on the steel strip surface. An object of the present invention is to provide a method for electrolytic pickling of a steel strip that can be formed.

[0006]

In order to achieve the above object, the method of electrolytic pickling of a steel strip according to the present invention includes a traveling direction of the steel strip when performing electrolytic pickling of the steel strip using an electrolytic solution. A method for electrolytic pickling of a steel strip, wherein an electrolytic current is passed through the steel strip through electrodes arranged along the strip to remove scale on the surface of the steel strip, the electrode being It is characterized in that a plurality of electrodes are arranged in parallel along the traveling direction so that the current density of the electrolytic current applied to the surface of the steel strip can be adjusted individually for each electrode.

[0007]

In the present invention, the current density of the electrolytic current applied to the surface of the steel strip from a plurality of electrodes arranged in parallel along the traveling direction of the steel strip is adjusted individually for each electrode, thereby The current density distribution in the longitudinal direction of the strip surface is made uniform.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION One example of an embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. FIG. 1 is a schematic diagram of an electrolytic pickling apparatus used in an electrolytic pickling method for a stainless steel strip, which is an example of an embodiment of the present invention. A steel strip such as a stainless steel strip 1 annealed after cold rolling is, as shown in FIG.
It is introduced into the electrolytic cell 3 filled with the neutral salt electrolytic solution through the deflector roll 2 and passes through the electrolytic solution, and then is led out of the electrolytic cell 3 through the deflector roll 4 to be the electrolytic cell of the next step. And sent to the washing and drying processing equipment.

On the deflector roll 2 side in the electrolytic cell 3,
A pair of positive electrode plates 5 arranged above and below the stainless steel strip 1.
a and 5b are provided in three rows along the traveling direction of the stainless steel strip 1, and a pair of negative electrode plates 6 arranged above and below the stainless steel strip 1 are provided on the deflector roll 4 side in the electrolytic cell 3.
Three rows of a and 6b are provided in the traveling direction of the stainless steel strip 1. The arrangement of the electrode plates is not necessarily limited to this. For example, the positive electrode plate (or the negative electrode plate) is on the upper side of the stainless steel strip 1, and the negative electrode plate (or the positive electrode plate) is on the lower side. A plurality of stainless steel strips 1 may be arranged in the traveling direction of the stainless steel strip 1 and may be appropriately changed depending on the purpose.

Each positive electrode plate 5a, 5b and each negative electrode plate 6
A DC power source (not shown) is supplied between a and 6b, so that the upper and lower surfaces of the stainless steel strip 1 passing between the positive electrode plates 5a and 5b are negatively charged, while
The upper and lower surfaces of the stainless steel strip 1 passing between the negative electrode plates 6a and 6b are positively charged. As a result, the current of the power source becomes an electrolytic current from each of the positive electrode plates 5a and 5b and flows to the negatively charged portion on the surface of the stainless steel strip 1, and then the stainless steel strip 1 flows to the negative electrode plates 6a and 6b side. After reaching the positive charging portion, an electrolytic current is generated from the positive charging portion and flows into the negative electrode plates 6a and 6b to return to the power source. At this time, the positively charged portion of the stainless steel strip 1 becomes the anode surface, and the scale of the surface of the stainless steel strip 1 becomes chemically due to the progress of dissolution of metal and metal oxide and generation of oxygen gas due to the chemical reaction on the anode surface. It is supposed to be removed.

Here, in this embodiment, in order to always obtain a substantially uniform electrolytic current density (see FIG. 2) along the longitudinal direction of the stainless steel strip 1 passing through the electrolytic solution, the following (1) ) And (2) based on each electrode plate 5a, 5b,
The electrolytic current density J (A / dm ² ) is controlled individually for each of 6a and 6b. α = (2ρ _s / ρtl) ^1/2 (1) J = (I _i / WL) · (αL · cosh (αX _i ) / sinh (αL)) (2) where I _i is an electrode Current (A), W is the width of the steel strip (m), ρ is the liquid resistance (Ωm), and ρ _s is the steel strip resistance (Ω).
m) and t are steel strip thicknesses (m), l is an electrode-steel strip distance (m), L is an electrode length (m), and X _i is a position (m) in the electrode length direction.

In the above equations (1) and (2),
The current applied to each electrode plate 5a, 5b, 6a, 6b by giving the electrolytic current density J (A / dm ² ) and the electrode position X _i (m) that effectively work for descaling of the stainless steel strip 1. Is controlled to be I _i . As a result, the electrolytic current density applied to the longitudinal direction of the stainless steel strip 1 can always be J (A / dm ² ), and it is possible to favorably prevent the conventional gradient current density from occurring.

In such a steel strip electrolytic pickling method as described above, since the current density distribution in the longitudinal direction of the stainless steel strip 1 can be made uniform, the oxygen gas on the high density current side as in the prior art can be obtained. The amount of current used for generation is greatly reduced, so that there is no waste, and the power consumption rate can be kept low. Further, since the current density distribution can be made uniform, it is possible to prevent the occurrence of uneven gloss called an electrolytic pattern on the surface of the steel strip 1. Further, since the electrolytic current density that works effectively for descaling can be obtained for each electrode, the descaling of the stainless steel strip 1 can be efficiently performed, and the scale residue can be reduced as compared with the conventional case.

In the above embodiment, electrolytic pickling is performed in the electrolytic bath 3 filled with a neutral salt solution, but an acidic solution such as nitric acid or sulfuric acid may be used instead of the neutral salt. Good. In the above embodiment, the case where the stainless steel strip 1 is passed through the electrolytic solution is taken as an example, but the present invention is not limited to this.
It is also applicable to a type in which an electrolytic solution is sprayed between the stainless steel strip 1 and each of the electrodes 5a, 5b, 6a, 6b.

[0015]

EXAMPLE A stainless steel strip 1 of SUS304, which was cold-rolled by using the neutral salt electrolytic cell 3 shown in FIG. 1 and then finish-annealed by atmospheric annealing at 1050 ° C., was descaled. A 20% sodium sulfate solution was used as the pickling solution, and nitric hydrofluoric acid pickling and nitric acid electrolytic pickling were performed as post-treatments after the neutral salt electrolytic pickling.

FIG. 2 shows a case where the electrodes arranged in parallel in the longitudinal direction of the stainless steel strip 1 are controlled so that J = 500 A / dm ² by using the above equations (1) and (2). 2 shows a current density distribution in the longitudinal direction of the stainless steel strip 1 of FIG. As is clear from FIG. 2, a substantially uniform current density distribution was obtained in the longitudinal direction of the stainless steel strip 1, and the conventional gradient current density distribution (see FIG. 6) was not generated.

Further, when the electric power consumption rate is compared with that of the conventional example, as shown in FIG.
It turned out to be% lower. Further, comparing the defective occurrence rate due to the electrolytic pattern with the conventional example, as shown in FIG.
The present invention was 0.2% and the conventional example was 2.0%, and it was found that the electrolytic pattern generation rate was significantly reduced because the electrolytic current density was uniform in the longitudinal direction of the stainless steel strip 1. It was

[0018]

As is apparent from the above description, according to the present invention, the current density distribution applied in the longitudinal direction of the steel strip can be made uniform, so that the oxygen gas generation on the high density current side as in the conventional case. The electric current used for is drastically reduced, so that there is no waste and the power consumption rate can be kept low.

Further, since the current density distribution can be made uniform, it is possible to prevent the occurrence of uneven luster called an electrolytic pattern on the surface of the steel strip, and to perform uniform pickling along the longitudinal direction of the steel strip. The effect that it can be obtained is obtained. Furthermore, since it is possible to obtain an electrolytic current density that effectively works for descaling for each electrode, it is possible to efficiently perform descaling of the steel strip, and it is possible to reduce the scale residue compared to the conventional case. can get.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used in an electrolytic pickling method for a stainless steel strip, which is an example of an embodiment of the present invention.

FIG. 2 is a distribution diagram showing current density in the electrode length direction.

FIG. 3 is a graph diagram comparing electric power consumption with a conventional example.

FIG. 4 is a graph diagram comparing a defect occurrence rate due to an electrolytic pattern with a conventional example.

FIG. 5 is an explanatory diagram for explaining a conventional example.

FIG. 6 is a distribution diagram showing the current density in the electrode length direction of the conventional example.

[Explanation of symbols]

 1 ... Stainless steel strip 3 ... Electrolyzer 5a, 5b ... Positive electrode plate 6a, 6b ... Negative electrode plate

Claims (1)

[Claims] 1. When electrolytically pickling a steel strip using an electrolytic solution, an electrolytic current is passed through the steel strip through electrodes arranged along the traveling direction of the steel strip, thereby A method for electrolytic pickling of a steel strip adapted to remove scale, wherein a plurality of the electrodes are arranged in parallel along the traveling direction of the steel strip and the current densities of the electrolytic currents applied to the surface of the steel strip are varied. An electrolytic pickling method for steel strips characterized in that each electrode can be individually adjusted.