JPH09195097A - Electrolytic polishing method for stainless steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the polishing speed in a stainless steel as high as possible and to uniformly finish the whole face of the sheet into objective glossiness with high reproducibility by using the stainless steel sheet to be polished as the positive electrode and executing intermittent electrolysis before the amt. to be electrolyzed reaches the prescribed one. SOLUTION: In an electrolytic bath of phosphoric acid series, the stainless steel sheet to be polished is arranged as the positive electrode and a metallic sheet as the counter electrode, and direct current is applied to subject the stainless steel sheet to electrolytic polishing. At this time, intermittent electrolysis in which the electric current is regulated to zero for >=1sec is executed for at least one time before the amt. to be electrolyzed reaches the prescribed one. Thus, the fixation of the pass of the electric current at the generating point of electrolyzing gas is prevented, by which the stainless steel sheet is subjected to high speed electrolytic polishing without generating deterioration in luster and nonuniformity.

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 plate uniformly and with a desired glossiness with good reproducibility. As one method for improving the glossiness and mirror-finishing of a stainless steel plate, so-called electrolytic polishing is known in which a metal plate is used as an anode and electrolysis is performed in a specific electrolytic solution. Smoothing the metal plate surface by electrolytic polishing not only improves the surface properties such as appearance, surface roughness, light reflectance and friction, but also improves mechanical properties, corrosion resistance, and magnetic properties of electromagnetic steel sheets. It is a technology that can be widely applied.

As for the electrolytic polishing method for metal plates, various liquid compositions and electrolysis conditions have been proposed including phosphoric acid type and sulfuric acid type. However, when electrolytically polishing a stainless steel sheet, poor gloss and uneven unevenness occur on the surface, and it has been extremely difficult to finish the entire surface uniformly and with a desired gloss level with good reproducibility.

[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 of preventing a gloss defect of a metal plate by a current load method is disclosed in Japanese Patent No. 1464470 (Japanese Examined Patent Publication No. 63).
No. 12159), positive and negative voltages are alternately applied between the metal to be polished immersed in the electrolytic polishing liquid and the insoluble counter electrode, and the frequency is changed to efficiently polish the surface of many kinds of metals. A method of performing is disclosed. Further, Japanese Patent No. 1464470 (Japanese Patent Laid-Open No. 63-76900)
When producing a thin film by electropolishing, the electropolishing is performed using a pulsed current and the film thickness is measured by pulsed light, so that the polishing surface roughness can be kept below a specific value while maintaining an arbitrary thickness. A method for making it possible to polish a thin film with a highly accurate film thickness is disclosed. 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 easily suppressed for the surface finish, it takes time to dissolve a predetermined metal.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have diligently studied an electrolytic polishing method that is industrially possible, and have maintained the polishing rate of direct current electrolysis as much as possible to obtain a uniform and desired gloss over the entire surface of a metal plate. We aimed to develop an electropolishing method that achieves a highly reproducible finish.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that the electrolytic polishing of stainless steel has a poor gloss and a variation in finish even though the electrolytic polishing is performed with the same solution, temperature, current density and electrolysis time. It was speculated that one reason was that the metal dissolution was non-uniform due to the immobilization of the current path and the immobilization point of the electrolytic gas. That is, when the reaction system is not significantly disturbed, it is considered that the place where the metal is dissolved by the anode current and the gas generation point may not change. Therefore, the inventors changed the electric current path in the solution by keeping the electrolysis amount (current density × electrolysis time) constant, inserting a current zero and a pause time for stopping gas generation during the electrolysis time. The length of the rest time and the number of rests,
The effect on surface gloss was investigated. As a result, it was possible to stably reproduce high gloss without defective gloss when the pause time was put in comparison with the test piece subjected to continuous electropolishing. When the rest time was less than 1 second, the gloss reproduction varied.
Above a second, the gloss remained almost unchanged. The minimum time required for this 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, depending on the viscosity of the polishing liquid and the area of the surface to be polished,
Sometimes more than a second is needed. As for the number of pauses, theoretically, if the number of times is increased, the current path can be changed a lot, so it is thought that the polishing efficiency will be improved. When the number of pauses was one or more, there was almost no difference in glossiness. However, in order to speed up the electrolysis, it is preferable that the rest time and the number of rests are small. Therefore, the pause time is set to 1 second or more, and the number of pauses is set to 1 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 their concentrations 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.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In an electrolytic polishing liquid tank, a stainless steel plate to be polished is used as an anode and a counter electrode is an insoluble metal plate. After electrolysis for a certain period of time, the current is made zero. After holding in that state for 1 second or more, electrolysis is performed again. This operation is repeated using a power switch with a timer or the like.

[0009]

【Example】

<Example 1> In Table 1, in a 55% sulfuric acid solution containing 85 g of wheat flour at 30 g / 1, SUS having a plate thickness of 0.3 mm was prepared.
A 430 stainless steel plate (cold rolled annealed plate with an area of 80 mm ² and a glossiness of 80 or more and 120 or less) is a plate to be polished with a current density of 200 A
/ Dm ² surface gloss after electropolishing for 15 seconds (JI
Incident angle 45 ° specular gloss defined by S Z8741)
Is shown by comparing the case of continuous electrolysis and the case of intermittent electrolysis. The electrolysis pattern of intermittent electrolysis is 7.5 seconds electrolysis → 1 second pause → 7.5.
Second electrolysis. It is clear that intermittent electrolysis shows a higher surface gloss with good reproducibility. Example 2 In Table 1, in a 55% sulfuric acid solution containing 85 g of wheat flour at 30 g / 1, SUS having a plate thickness of 0.3 mm was prepared.
A 430 stainless steel plate (cold rolled annealed plate with an area of 80 mm ² and a glossiness of 80 or more and 120 or less) is a plate to be polished with a current density of 200 A
The surface glossiness (incident angle 45 ° specular glossiness specified by JIS Z8741) when intermittent electrolytic polishing is performed at / dm ² for 15 seconds is shown. The electrolysis pattern of the intermittent electrolysis is 7.5 seconds electrolysis → 10 seconds rest → 7.5 seconds electrolysis. It is clear that it exhibits high surface gloss with good reproducibility. Example 3 In Table 1, in a 55% sulfuric acid solution containing 85 g of wheat flour at 30 g / 1, SUS having a plate thickness of 0.3 mm was prepared.
A 430 stainless steel plate (cold rolled annealed plate with an area of 80 mm ² and a glossiness of 80 or more and 120 or less) is a plate to be polished with a current density of 200 A
The surface glossiness (incident angle 45 ° specular glossiness defined by JIS Z8741) in the case of intermittent electropolishing at / dm ² for 15 seconds is shown in comparison between the case of continuous electrolysis and the case of intermittent electrolysis.
The electrolysis pattern of intermittent electrolysis is 5 seconds electrolysis → 5 seconds rest → 5 seconds electrolysis → 5 seconds rest → 5 seconds electrolysis. It is clear that it exhibits high surface gloss with good reproducibility. <Example 4> In Table 1, in a 55% sulfuric acid solution containing 30 g / 1 of flour at 85 ° C, SUS4 having a plate thickness of 0.3 mm was used.
30 stainless steel plate (cold rolled annealed plate having an area of 80 mm ² and a glossiness of 80 or more and 120 or less) is to be polished plate Current density 200 A /
Surface gloss after intermittent electropolishing with dm ² for 15 seconds (J
The incident angle of 45 ° specular gloss defined by IS Z8741) is shown in comparison between continuous electrolysis and intermittent electrolysis. The electrolysis pattern of intermittent electrolysis is 2.5 seconds electrolysis → 5 seconds rest →
2.5 seconds electrolysis → 5 seconds pause → 2.5 seconds electrolysis → 5 seconds pause →
2.5 seconds electrolysis → 5 seconds pause → 2.5 seconds electrolysis → 5 seconds pause →
2.5 seconds electrolysis. It is clear that it exhibits high surface gloss with good reproducibility.

[0010]

[Table 1]

[0011]

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 producing a stainless steel plate electrolytically polished product.

Claims (1)

[Claims] 1. A stainless steel plate characterized in that a stainless steel plate to be polished is used as an anode and a counter electrode is a metal plate, and intermittent electrolysis is carried out at least once for 1 second or more until a predetermined electrolysis amount is reached. Electrolytic polishing method.