JPS6333600A - Method for electrolytically pickling steel strip - Google Patents

Abstract

PURPOSE:To carry out perfect pickling and to obtain a steel strip having a fine surface when oxide on the surface of a steel strip is removed by electrolytic pickling in a pickling soln., by arranging anode plates and cathode plates having different lengths in the pickling soln. so that they confront each other on both sides of the steel strip which is passed through the pickling soln. CONSTITUTION:When an oxide film sticking to the surface of a steel strip 3 of ordinary steel, stainless steel or other steel is removed by passing the steel strip 3 through a pickling bath 2 such as a soln. of sulfuric acid, hydrochloric acid or phosphoric acid, pairs of anode plates 6 and cathode plates 7 are alternately arranged in the pickling bath 2 so that they confront each other on both sides of the steel strip 2 which is passed through the bath. In case of anodic pickling, the cathode plates 7 are made longer than the anode plates 6. In case of cathodic pickling, the anode plates 6 are made longer than the cathode plates 7. Unpickled parts are not present on the surface of the steel strip and a smooth fine pickled surface is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a process for electrolytic pickling of steel strips, such as ordinary low carbon steel sheets and stainless steel sheets.

[Prior art] Pickling is performed to remove scale (oxide film) formed on the surface due to high-temperature processing or heat treatment, but it is also used as a material with a glossy surface, such as stainless steel sheets and base plates for painting or plating. In order to complete pickling in a short time and prevent surface deterioration and pickling embrittlement, steel strips are generally subjected to electrolytic pickling methods such as anodic pickling or cathodic pickling. The electrolytic pickling method is described in Japanese Utility Model Publication No. 58-3565, for example.
As introduced in Figure 1 of Publication No. 9, a large number of electrode plates are arranged above and below a steel strip running in a pickling solution so as to be perpendicular to the running direction of the strip, and are energized. It is a scale.

There is also an electrolytic pickling method in which a pair (set) of anode plates or cathode plates are arranged at opposite positions of the steel strip and alternately arranged in the running direction of the steel strip. Furthermore, such an electrolytic pickling method includes the provision of an impeller near the electrode plate as in Japanese Patent Publication No. 57-45319 in order to forcefully flow the pickling liquid onto the plate surface of the #4 strip, and the method described above. Attempts have also been made to change the partial shape of the electrode plate, as disclosed in the publication.

[Problems to be Solved by the Invention] As described above, the electrolytic pickling method has been improved. However, on the surface of the steel strip after pickling.

Impurities dissolved in the pickling solution (Ni, Cu, Cr,
There was a problem in that metal oxides such as Fe, hydroxides, etc.) were deposited, significantly reducing the pickling efficiency. The present invention relates to an electrolytic pickling method with high pickling efficiency, and the present inventors have
As a result of various studies on electrolytic pickling methods to solve this problem, we found that the problem could be solved by changing the size of the electrodes, which are manufactured to the same size, using the electrolytic method due to the advantage of using both electrodes together. . The present invention was constructed based on this knowledge.

[Means for solving the bending point problem] The present invention uses a set of two plates, an anode plate and a cathode plate having different lengths, which are arranged at opposing positions across a steel strip running in a pickling solution. , the length of the anode plate in the case of anodic pickling and the length of the cathode plate in the case of cathodic pickling is shorter than the plate length of the other polarity, and the anode plate and the plate are arranged in the running direction of the steel strip. This is an electrolytic pickling method for steel strip characterized by alternately arranging cathode plates.

The present invention will be described in detail below with reference to the drawings.

The figure shows an embodiment of the invention in an anodic electrolytic pickling apparatus. 1
is a processing tank filled with pickling liquid 2.

As the pickling solution 2, a sulfuric acid-based, hydrochloric acid-based, phosphoric acid-based, or other commonly used electrolytic pickling solution is used. 3 is a steel strip made of low carbon steel, stainless steel, etc. 4 is a deflector roll, and 5 is a seal roll. That is, the steel strip 3 is passed through the electrolytic treatment tank 1 by the deflector roll 4.
It is configured so that it passes while being guided by the seal roll 5. 6 is an anode plate and 7 is a cathode plate. Anode plate 6
The and cathode plates 7 are a pair (set) of two plates arranged opposite to each other with the steel strip 3 in between, and the anode plate 6 and the cathode plate 7 have different lengths, and the steel strip 3 are arranged alternately in the running direction. In this case, in the anodic pickling method, the length of the anode plate 6 is shorter than the cathode plate 7, and in the cathodic pickling method, the length of the cathode plate is shorter than the anode plate. The figure shows an example in which the length of the anode plate is shorter than the length of the cathode plate using the anodic pickling method.

[Function] The inventors have determined that the length Q+ of each anode plate and the length Q of each cathode plate
- The descaling pickling efficiency of steel plates was investigated by changing various values.

That is, L+ (total length of each anode plate) = ΣΩ + L- (total length of each cathode plate) = Σ2-, and L++ L- = 100
0 m (constant).

A. Total energization time...50 seconds, pickling solution - H2SO4: 200g/Q, NaN0. :
200g/Q, temperature 280℃ C, current density of cathode plate...40 A/d+m"2, steel strip...5 US409 hot coil thickness:
1.51m! 1. Width: 12°O+n+a, length: Coil Descaling pickling results are shown in Table 1.

(The percentage in the frame is the percentage of descaled area.) From Table 1, in the conventional pickling example where L- = 500m and L+ = 500m, 60% of the surface area of the strip steel plate is descaled, but it is insufficient. During pickling, descaling progresses as L- becomes larger, L-=800my L+=200
It is completely descaled at m. That is, in the anodic pickling method, by making the length Q- of the cathode plate longer than the length Q+ of the anode plate, it is possible to completely descale what was conventionally insufficiently descaled.

The effect of the present invention has been explained using the example of the anodic pickling method, but it is clear that in the case of the cathodic pickling method, pickling can be carried out with high efficiency by increasing the length of the anode plate Q+. .

[Effects of the Invention] Accordingly, the present invention enables anodic pickling and cathodic pickling (or vice versa) of the steel strip 3 passing through the narrow gap between the anode plate and the cathode plate while energizing the anode plate and the cathode plate. ) is repeated to produce a steel strip with a beautiful surface and no unpickled parts during pickling.

Especially when pickling stainless steel strips, it makes the surface beautiful and improves corrosion resistance. In addition, in the method of the present invention as described above, in the anodic pickling method, a counter cathode plate is used as the final electrode,
In addition, in the cathodic pickling method, the pickling efficiency is further improved by providing a counter anode plate to the final electrode.

[Brief explanation of the drawing]

The figure shows an example of an anodic pickling method according to an embodiment of the present invention. 1: Treatment tank, 2: Pickling liquid, 3: Steel strip, 4: Deflector roll, 5: Seal roll, 6: Anode plate, 7:
cathode plate,

Claims (1)

[Claims] A pair of anode and cathode plates with different lengths are placed opposite each other across a steel strip running in the pickling solution.In the case of anodic pickling, the length of the anode plate is In the case of cathodic pickling, the length of the cathode plates is shorter than the length of the plates of other polarities, and the anode plates and cathode plates are arranged alternately in the running direction of the steel strip. electrolytic pickling method.