JP3006703B2 - Continuous descaling method for stainless steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously removing scale formed on the surface of a stainless steel strip after annealing, and more particularly to a neutral salt bath electrolytic descaling method.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional method for removing scale after annealing a stainless steel strip. The stainless steel strip 1 that has produced scale on its surface when subjected to annealing enters the neutral salt electrolysis tank 2. The tank 2 is filled with an aqueous solution 3 of a neutral salt such as Na ₂ SO ₄ as an electrolytic solution, and an electrode group 4 for performing electrolysis is provided opposite to both ends of the steel strip 1. . In this state, electricity is supplied under the condition that the steel strip 1 becomes an anode, and the scale formed on the steel strip 1 is oxidized anodically. Most of the scale formed on the steel strip by this electrolysis is removed. However, in order to remove the remaining scale and passivate the steel strip surface after descaling, the steel strip 1 has a ringer roll group 7. To the pickling tank 8 via The pickling tank 8 is filled with an acid solution 9 of a mixed acid composed of, for example, nitric acid and hydrofluoric acid, and performs passivation after finishing pickling and descaling of the stainless steel strip.

[0003]

FIG. 3 shows the polarization characteristics of the anode and the cathode in such a conventional method. That is, in the conventional method, as the current density between the steel strip 1 as the anode and the electrode 4 as the cathode increases, the degree of polarization at the anode and the cathode increases (the thick line in FIG. 3), and high productivity is obtained. If electrolytic descaling is performed at a high current density, the bath voltage becomes relatively large, and the power consumption increases. Therefore, in order to suppress power consumption, the operation at a low current density (6 to 8 A / cm ² ) has been unavoidably performed. Further, in the conventional method, H ₂ gas generated on the cathode surface tends to adhere and stagnate on the cathode surface, and this phenomenon further increases the bath resistance and has a disadvantage of increasing power consumption. Therefore, the present invention aims to provide a continuous descaling method of stainless steel strip which enables high-efficiency electrolytic descaling without increasing the power consumption by solving the problems in the conventional descaling method. It is.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for continuously descaling a stainless steel strip after cold rolling annealing by neutral salt electrolysis, wherein the stainless steel strip as the material to be treated and the electrode are not separated. Contact, and the electrolytic solution present between the steel strip and the electrode is subjected to electrolysis in a state where vibration is imparted by a vibrating flow nozzle , and the vibration of the electrolytic solution is set to several Hz to 40 Hz, Further, as a method for imparting vibration to the electrolytic solution, a vibrating flow nozzle is provided on the electrode portion, and this is used as means for solving the problem.

[0005]

According to the present invention, by vibrating the electrolytic solution during the descaling of the electrode, a vibrating flow is generated between the stainless steel strip and the electrode. Since the boundary layer can be made thin, ion supply to the electrode surface (stainless steel strip surface and cathode surface) and dissipation of electrolytic products become active, the degree of concentration polarization decreases and the electrolytic voltage is kept low. it can. Further, the adhesion of the H ₂ gas generated on the cathode surface by the vibrating flow to the cathode surface or the stainless steel strip surface is suppressed, and the H ₂ gas on the electrode surface is suppressed.
₍₂₎ Increase in bath resistance due to gas adhesion can also be suppressed. Therefore, the electrolysis voltage can be suppressed to a low level, and operation with low power is possible even in high current density operation.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. . In FIG. 1, a stainless steel strip 1 having a scale formed on its surface when subjected to annealing enters a neutral salt electrolysis tank 2. This tank 2
The inside is filled with an aqueous solution 3 of a neutral salt made of Na ₂ SO ₄ or the like as an electrolytic solution. An electrode group 4 for performing electrolysis is provided opposite to both surfaces of the steel strip 1. A feature of the present invention is that a header 5 and an oscillating flow nozzle 6 are provided in addition to the conventional technology, and electrolysis is performed in a state where an oscillating flow is applied between the stainless steel strip 1 and the electrode 4. . If the frequency of the oscillating flow is set too low,
The concentration boundary layer generated on the surface of the stainless steel strip 1 becomes thicker, and the ion replenishment to the electrode surface (stainless steel strip as an anode and the electrode surface as a cathode) and the escape of electrolytic products are not sufficient and the effect is small. the lower limit of the frequencies from was 3H _Z. Further, by the response of the water flow is too high frequency is deteriorated, and the upper limit about 40H _Z.

Namely, it energized under the condition that the steel strip 1 while applying a vibration flow oscillation condition between 3H _Z of 40H _Z is an anode, oxidizing the scale is generated on the steel strip 1 anodically In this way, the scale is removed. The electrolysis conditions are such that the current density is 6 to 8 A /
According to the method of the present invention, the electrolysis voltage can be suppressed to a low state even when the current density is 8 A / cm ² or more, whereas the upper limit is about ² cm ^2, so that operation at a low voltage is possible. Become. Thereafter, in order to passivate the surface of the steel strip 1 after descaling, the steel strip 1 is sent to a pickling tank 8 via a ringer roll group 7. The tank 8 is filled with an acid solution 9 of a mixed acid composed of nitric acid and hydrofluoric acid, and performs a passivation treatment. As an example of a method for imparting vibration to the electrolytic solution, an embodiment in which a vibration flow is jetted to the stainless steel strip 1 by a vibration flow nozzle 6 provided in the header 5 and the electrode 4 has been described. It goes without saying that various methods for imparting vibration to the electrolytic solution are possible within the scope of the gist.

[0008]

As it has been described [of the effect the invention described above in detail the present invention is, stearyl
In order to continuously process stainless steel strip,
To the electrolyte solution during electrolytic descaling using an oscillating flow nozzle.
In the state where vibration is applied, a vibration flow is generated between the stainless steel strip and the electrode, and this vibration flow can reduce the concentration boundary layer generated at the time of high current density operation. Since the dissipation of the electrolysis product becomes active, the degree of concentration polarization decreases and the electrolysis voltage can be kept low. Furthermore, the adhesion of H ₂ gas generated on the cathode surface by the vibrating flow to the cathode surface or the stainless steel strip surface can be suppressed, and the increase in bath resistance accompanying the H ₂ gas adhesion to the electrode surface can also be suppressed. Therefore, the electrolysis voltage can be suppressed to a low level, and operation can be performed with low power even in high current density operation, so that descaling can be performed efficiently and continuously.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a process in a continuous descaling method of a stainless steel strip according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a process in a conventional method for descaling a stainless steel strip.

FIG. 3 is an explanatory diagram of a conventional polarization characteristic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stainless steel strip 2 Neutral salt electrolysis tank 3 Neutral salt aqueous solution 4 Electrode 5 Header 6 Oscillating flow nozzle 7 Ringerol 8 Pickling tank 9 Acid liquid

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuhiro Shibatomi 4-6-22 Kannonshinmachi, Nishi-ku, Hiroshima Sanritsu Heavy Industries, Ltd. Hiroshima Works (72) Inventor Nobuyuki Taniguchi 4-6-kannonshinmachi, Nishi-ku, Hiroshima-shi 22 Hiroshima Works, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-59-162496 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25F 1/06

Claims (3)

(57) [Claims] 1. A method for continuously descaling a stainless steel strip after cold rolling annealing by neutral salt electrolysis, wherein the stainless steel strip as a material to be treated and the electrode are brought into non-contact with each other.
A continuous descaling method for a stainless steel strip, characterized in that electrolysis is performed in a state where vibration is applied to an electrolyte present between the electrode and an electrode by a vibrating nozzle . Wherein said continuous descaling method of stainless steel strip according to claim 1, characterized in that the vibration of the electrolyte as a few H _Z ~40H _Z. 3. The method for continuously descaling a stainless steel strip according to claim 1, wherein a vibrating flow nozzle is provided on the electrode portion as a method for imparting vibration to the electrolytic solution.