JPH09195098A - Continuous electrolytic polishing method for stainless steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the electrolyzing speed of direct current electrolysis and to uniformly finish the whole face of a stainless steel strip into the objective glossiness by subjecting a stainless steel strip to intermittent electrolysis between electrodes under specified conditions. SOLUTION: A stainless steel strip is introduced into an electrolytic cell, is subjected to direct current electrolysis between electrodes in an electrolytic polishing bath of phosphoric acid series or the like, is continuously subjected to electrolytic polishing and is thereafter pulled out. At this time, it is subjected to intermittent electrolysis in certain current value under time conditions shown by the inequality in the formula L = the length (m) of the steel strip to be immersed, V = sheet passing velocity (m/s), T = required electrolyzing time (s) and (t) = electrolysis one stopping time (S)}.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic polishing method for finishing the entire surface of a stainless steel strip uniformly and with a desired glossiness with good reproducibility. As one method for improving the glossiness and mirror-finishing of a metal strip, so-called electrolytic polishing is known in which the metal strip is used as an anode for electrolysis in a specific electrolytic solution. The smoothing of the metal plate surface by electrolytic polishing is
In addition to improving the surface properties such as appearance, surface roughness, light reflectance and frictional properties, it is a widely applicable technology that can improve mechanical properties, corrosion resistance, and magnetic properties of electromagnetic steel sheets.

As for the electrolytic polishing method for stainless steel sheets, various liquid compositions and electrolysis conditions including a phosphoric acid type and a sulfuric acid type have been proposed. However, when electrolytically polishing a stainless steel plate, it is easy to cause poor gloss and uneven unevenness on the surface,
It was extremely difficult to finish the entire surface uniformly to the desired glossiness.

[0003]

2. Description of the Related Art Electropolishing of stainless steel has been widely used since the 1930s. To improve the surface gloss of electropolishing, chromic acid, dichromate, oxalic acid, agar powder and phosphoric acid or (phosphoric acid + sulfuric acid) solution are used. , Glycerin, citric acid,
It is known to add gelatin, glue, glycolic acid, polyethylene glycol, starch, etc., and these special additives accelerate the oxidative dissolution of the anode, enhance the polishing efficiency, and act as an inhibitor locally. It is described that the surface gloss is improved by suppressing various etchings. Further, as the electrolytic polishing method,
It is a method of electrolyzing continuously for several seconds to several minutes in each predetermined temperature range. (Stainless Steel Handbook, 1995
Published by Nikkan Kogyo Shimbun, January 24, 2012, p. 1143, M
ETAL FINISHING, May 1991 issue,
p. 47, PLATING AND SURFACE
FINISHING, June 1981, p. 44).

A method for preventing the gloss defect of a metal plate by a current load method is disclosed in Japanese Patent No. 1464470 (Japanese Patent Publication No. 63-63).
No. 12159), positive and negative voltages are alternately applied between the metal to be polished immersed in an electrolytic polishing solution and the insoluble counter electrode, and the frequency is changed to efficiently polish the surface of many kinds of metals. A method of doing so is disclosed. Also,
When producing a thin film by electropolishing in JP-A-63-76900, electropolishing is performed using a pulsed current and film thickness measurement is performed with pulsed light, while keeping the polished surface roughness below a specific value. A method is disclosed in which a thin film having an arbitrary thickness can be polished with high precision. Although the generation of gas is suppressed in alternating electrolysis, it takes longer than direct current electrolysis to dissolve a given metal, and there is a limit to high-speed electrolysis.
Further, although the pulse current is easy to control for surface finishing, it takes time to dissolve a predetermined metal.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention diligently studied an industrially possible electrolytic polishing method, maintained the polishing rate of direct current electrolysis, and made the entire surface of a stainless steel strip uniformly glossy for the purpose. The aim was to develop a continuous electropolishing method that finishes every time.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that the electrolytic polishing of stainless steel causes a defective gloss and a variation in finish even though the electrolytic polishing is performed with the same solution, temperature, current density and electrolysis time. On the other hand, it was presumed that one of the causes was that the metal dissolution was non-uniform due to the immobilization of the current path and the immobilization point of the electrolytic gas.
Therefore, the inventors have determined the amount of electrolysis (current density x electrolysis time)
Was kept constant, and during the electrolysis time, an electric current = 0 and a rest time for interrupting gas generation were inserted to change the current path in the solution. The influence of the length of rest time and the number of rest times on the surface gloss was examined. As a result, it was possible to stably reproduce high gloss without defective gloss when a pause time was set as compared with the case of continuous electrolytic polishing. The electrolysis time of continuous electropolishing is the length of the steel strip to be immersed L (m) the stripping speed v (m / s) the required electrolysis time per unit area T (s) the electrolysis rest time t (s) Number of pauses n (times),

[0007]

[Equation 2]

From this formula

[0009]

(Equation 3)

Since n must be at least once,

[0011]

(Equation 4)

## EQU1 ## From the viewpoint of ensuring a sufficient electrolysis time with a rest time interposed, n is preferably twice or more. Regarding the pause time, the minimum time required for pause is considered to be the time from the end of gas generation until the offshore liquid covers the entire surface to be polished. Therefore, since this time varies depending on the viscosity of the polishing liquid, the area of the surface to be polished, the relative speed of the liquid in the tank with the steel strip, and the stirring condition, it is not specified, but the offshore liquid completely covers the entire surface. The time is preferably 1 second or more.

Various types of electrolytic polishing bath compositions have been proposed, such as phosphoric acid type, sulfuric acid type, perchloric acid type, chromic acid type, and the concentration and types of additives are wide-ranging, but are specified in the present invention. This is not the case, and the same applies because there are various necessary electrolysis conditions depending on the liquid composition.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The power supply device is set so that the anode stainless steel strip is introduced into the electrolytic cell and, during the transportation in the polishing solution, the electrolysis and the electrolysis pause are alternately and regularly repeated according to the method of the present invention. .

[0015]

【Example】

<Example 1> In Table 1, in a 55% sulfuric acid solution containing 85 g of wheat flour at 30 g / l, a plate thickness of 0.3 mm and a width of 12
An example of electrolytically polishing a 00 mm SUS430 stainless steel plate (cold rolled annealed plate having a glossiness of 80 or more and 120 or less) at a speed of 50 m / min is shown. The length of the steel strip to be dipped was 18 m, and the fixed point of the steel strip was electropolished for 15 seconds at a current density of 200 A / dm ² . In the case of intermittent electrolysis, the fixed point on the steel strip is immersed 1
The power supply device was set so that the electrolysis was stopped once for 1 second, and the immersion length of the steel strip was adjusted so that the total electrolysis time at the fixed point of the steel strip was 15 seconds. The surface glossiness (incident angle 45 ° specular glossiness specified in JIS Z8741) was measured at 5 points at 1 m intervals, and the average value was defined as a representative glossiness for 5 m. The representative glossiness was measured at 5 points at 5 m intervals. . It is clear that in the case of intermittent electrolysis as compared with continuous electrolysis, it is possible to obtain a stainless steel plate with less variation in gloss and high surface gloss. <Example 2> In Table 1, in a 55% sulfuric acid solution containing 85 g of wheat flour at 30 g / l, a plate thickness of 0.3 mm and a width of 12
An example of electrolytically polishing a 00 mm SUS430 stainless steel plate (cold rolled annealed plate having a glossiness of 80 or more and 120 or less) at a speed of 50 m / min is shown. The condition of intermittent electrolysis is to set the power supply so that the fixed point on the steel strip will be electrolyzed once for 3 seconds during immersion, and soak the steel strip so that the total electrolysis time at the fixed point on the steel strip will be 15 seconds. Adjusted the length. Surface gloss (JIS Z874
The incident angle of 45 ° specular gloss defined in 1) was measured at 5 points at 1 m intervals as an average value, and the representative gloss was measured for 5 m, and the representative gloss was measured at 5 points at 5 m intervals. It is clear that in the case of intermittent electrolysis as compared with continuous electrolysis, it is possible to obtain a stainless steel plate with less variation in gloss and high surface gloss. <Example 3> In Table 1, in a 55% sulfuric acid solution at 85 ° C with 30 g / l of wheat flour added, a plate thickness of 0.3 mm and a width of 12
An example of electrolytically polishing a 00 mm SUS430 stainless steel plate (cold rolled annealed plate having a glossiness of 80 or more and 120 or less) at a speed of 50 m / min is shown. The conditions of the intermittent electrolysis are set so that the fixed point on the steel strip is set to the electrolysis pause of 1 second for each 3 times during the immersion, and the total electrolysis time of the fixed point of the steel strip is set to 15 seconds. The immersion length was adjusted. Surface gloss (JIS
The incident angle 45 ° specular gloss defined by Z8741)
The average value measured at 5 points at 1 m intervals was defined as the representative glossiness for 5 m, and the representative glossiness was measured at 5 points at 5 m intervals. It is clear that in the case of intermittent electrolysis as compared with continuous electrolysis, it is possible to obtain a stainless steel plate with less variation in gloss and high surface gloss.

[0016]

[Table 1]

[0017]

The electropolishing method of the present invention is an epoch-making method as an electropolishing method that maintains the polishing rate of direct current electrolysis and finishes the entire surface of a metal plate uniformly and with a desired glossiness with good reproducibility. . This is an extremely effective method for industrially mass-producing electrolytically polished stainless steel plates.

Claims (1)

[Claims] 1. A stainless steel strip is introduced into an electrolytic cell,
A continuous electropolishing method for a stainless steel strip, which comprises intermittently electrolyzing at a constant current value under the following time conditions when continuously performing electropolishing between electrodes in a pulling process. [Equation 1] The length of the steel strip to be immersed is L (m), the stripping speed is v (m / s), the required electrolysis time is T (s), and the electrolysis rest time is t (s).