JP5787614B2 - Method and apparatus for removing oxide scale by electropolishing - Google Patents

Description

  The present invention relates to a method and apparatus for removing oxide scale generated in a welded portion of stainless steel by electropolishing.

  When stainless steel is welded, an oxide scale called “weld burn” is generated at the welded portion. Since this oxide scale causes various troubles, it must be removed, and “electropolishing” for removing it electrochemically is widely used.

  FIG. 4 shows an example of a method for removing oxide scale by electropolishing. A cloth body 91 such as a non-woven fabric is wrapped around and fixed to a stainless steel rod-like electrode 90 protruding from the tip of the holder 9. Is impregnated and pressed against the welded portion 93 of the stainless steel 92 and energized, thereby removing the oxide scale generated in the welded portion 93 (see, for example, Patent Document 1). The electrolyte includes various acids such as sulfuric acid, phosphoric acid, hydrofluoric acid, nitric acid, citric acid, tartaric acid, malic acid, acetic acid, succinic acid, and neutral salt aqueous solutions such as ammonium salts, potassium salts, and sodium salts. Used.

JP 2005-213550 A

  However, in the above-described oxide scale removal method, the cloth body 91 needs to be wound and fixed around the rod-shaped electrode 90, which takes time for preparation and may cause the cloth body 91 to come off during the operation. Further, it is not easy to uniformly contact the cloth body 91 with the uneven surface of the welded portion 93, and it is difficult to completely remove the oxide scale from the welded portion 93.

  In order to solve the above problem, the inventor has made extensive studies, and instead of using the rod-shaped electrode 90, an electrode formed by bundling flexible carbon fibers in a brush shape is used. Devised to include directly. According to this method, it is not necessary to wind the cloth body, and the bundle of carbon fibers constituting the electrode can be brought into contact with the uneven surface of the welded portion 93 without unevenness. However, when such an electrode is used, the electrical conductivity of the carbon fiber is extremely good, and the contact portion between the stainless steel and the electrode generates heat and becomes hot due to energization, and depending on the electrolyte, it can be a toxic gas. This is an obstacle to the use of carbon fiber electrodes.

  The present invention has been made by paying attention to the above problem, and employs an electrode portion in which carbon fibers are bundled in a brush shape, and by electropolishing that does not generate toxic gas even if such an electrode portion is used. An object of the present invention is to provide an oxide scale removing method and an apparatus therefor.

The method for removing oxide scale by electropolishing according to the present invention uses a neutral salt aqueous solution combining one or more of sodium salt, potassium salt and ammonium salt of citric acid, tartaric acid, malic acid, lactic acid as an electrolytic solution. In the electrode portion formed by bundling carbon fibers in a brush shape, the electrolyte solution is included in the bundle of carbon fibers and pressed against the welded portion of stainless steel to energize the welded portion, thereby forming an oxide scale on the welded portion. It is characterized by removing.

According to the present invention, the bundle of carbon fibers constituting the electrode part can be uniformly brought into contact with the uneven surface of the welded portion, so that the oxide scale can be reliably removed. In addition, since the carbon fiber constituting the electrode part has extremely good electrical conductivity, the contact part between the stainless steel and the electrode part generates heat and becomes high temperature due to the current. However, citric acid, tartaric acid, malic acid are used as the electrolyte. Since a neutral salt aqueous solution combining one or more of lactic acid sodium salt, potassium salt and ammonium salt is used, no toxic gas is generated from the electrolyte.

In a preferred embodiment of the present invention, a neutral salt aqueous solution in which one or more of sodium salt, potassium salt and ammonium salt of tartaric acid are combined is used as the electrolytic solution.

When stainless steel is treated with an aqueous solution of neutral salt in which one or more of sodium salt, potassium salt, and ammonium salt of tartaric acid is combined as an electrolytic solution, the contact portion between the stainless steel and the electrode portion It was confirmed that even if a spark occurred, the treated portion did not deteriorate in corrosion resistance and was higher in corrosion resistance than the untreated portion. On the other hand, when other electrolyte solutions were used, it was confirmed that when sparks occur at the contact portion between the stainless steel and the electrode portion, the corrosion resistance is significantly reduced even at the treated portion. In addition, the corrosion resistance test was judged by comparing the weight loss ratio after the test piece was immersed in a ferric chloride aqueous solution.

An apparatus for removing oxide scale by electropolishing according to the present invention comprises an apparatus main body and an electrolytic solution. As the electrolytic solution, one of citric acid, tartaric acid, malic acid, sodium salt of lactic acid, potassium salt, and ammonium salt is used. A neutral salt aqueous solution in which two or more species are combined is used. The apparatus main body has a power supply part and an electrode part provided at each end of two cord wires drawn from the output terminal of the power supply part, and one electrode part can be connected to stainless steel, The other electrode part is formed by bundling carbon fibers in a brush shape, and the electrolytic solution is held in a gap between the carbon fibers .

In order to remove the oxide scale generated in the welded portion using the oxide scale removing device having the above-described configuration, one electrode portion is connected to stainless steel, and the electrolyte is applied to the bundle of carbon fibers constituting the other electrode portion. It is included and pressed against the welded portion of stainless steel, and a voltage supplied from the power supply unit is applied between the electrode units to conduct electricity. Since the bundle of carbon fibers constituting the electrode portion is flexible and can be brought into uniform contact with the uneven surface of the welded portion, the oxide scale in the welded portion is reliably removed. In addition, since the carbon fiber constituting the electrode part has extremely good electrical conductivity, the contact part between the stainless steel and the electrode part generates heat and becomes high temperature due to current application. However, as the electrolyte, citric acid, tartaric acid, apple Since a neutral salt aqueous solution in which one or more of acid, lactic acid sodium salt, potassium salt and ammonium salt is combined is used, no toxic gas is generated from the electrolyte.

According to this invention, since the electrolyte solution is directly included in the bundle of carbon fibers of the electrode portion formed by bundling carbon fibers in a brush shape and pressed against the welded portion to energize, the cloth body is wrapped around the electrode portion, etc. This work is unnecessary, and the bundle of carbon fibers constituting the electrode portion can be brought into contact with the uneven surface of the welded portion evenly, and the oxide scale can be reliably removed. In addition, no toxic gas is generated from the electrolytic solution even when the contact portion between the stainless steel and the electrode portion generates heat and becomes high temperature due to energization.

It is a perspective view which shows the apparatus structure for enforcing the oxide scale removal method of this invention. It is a front view which shows an electrode. It is sectional drawing which follows the AA line of FIG. It is a perspective view which shows the conventional oxide scale removal method.

FIG. 1 shows a configuration of an oxide scale removing apparatus according to an embodiment of the present invention and a method for removing oxide scale (indicated by hatching in the figure) generated in a welded portion 50 of stainless steel 5 using the apparatus. Show.
The oxide scale removing apparatus in the illustrated example removes the oxide scale by electrolytic polishing, and includes an apparatus main body 1 and an electrolytic solution 10. The apparatus main body 1 includes a box-shaped power supply unit 2, two cord wires 23 and 24 drawn from output terminals 21 and 22 on the front surface of the power supply unit 2, and tips of the respective code wires 23 and 24. Are provided with electrode portions 3 and 4, respectively. The output terminals 21 and 22 of the power supply unit 2 can output AC, DC, and AC / DC superimposed voltages by switching the switches. The operator selects the output voltage format, and adjusts the output voltage by turning the volume 25 while viewing the state of the stainless steel 5 to be processed. The output voltage is adjusted in the range of 15 to 40 volts, for example, and a current of 5 to 50 amperes is passed.

  One electrode portion 3 is configured to be electrically and mechanically connectable to the stainless steel 5 to be processed. In this embodiment, the electrode portion 3 can cope with various thicknesses of the stainless steel 5 and can be attached to and detached from the stainless steel 5. It is configured using a clip 30 for ease.

  The other electrode portion 4 is formed by closely bundling ultrafine carbon fibers having a flexible linear shape in a brush shape, and an electrolytic solution is held in a gap between the carbon fibers. As shown in FIG. 2, the base end portion of the carbon fiber bundle 42 is inserted into and fixed to the opening 41 at the tip of the stainless steel pipe 40. Carbon fibers having a low coefficient of linear expansion, being hardly affected by acids, bases, and various solvents, excellent in chemical stability, and excellent in tensile strength and wear characteristics are used.

  A screw shaft 43 protrudes from the rear end surface of the pipe 40, and is screwed into a screw hole of an electrode connection portion (not shown) provided at the tip of a holder 44 that can be held by hand. The electrode unit 4 is fixed to the holder 44 and is electrically connected to the cord wire 24. As shown in FIGS. 2 and 3, a cylindrical cover 45 made of synthetic rubber or the like is attached to the outer peripheral surface of the pipe 40 by heat shrinking. The distal end edge of the cylindrical cover 45 protrudes from the distal end of the pipe 40 and surrounds the proximal end portion of the carbon fiber bundle 42, so that even if the proximal end portion of the carbon fiber bundle 42 is bent, the opening of the distal end of the pipe 40 is opened. Touching the edges will not hurt you.

  Since the above-described brush-shaped electrode unit 4 is attached to the holder 44 by screwing the screw shaft 43, the electrode unit 4 can be replaced with another electrode unit 4. For example, a plurality of types of electrode portions 4 having different wire diameters, lengths, densities, and the like of carbon fibers are prepared in advance, and either one is selected according to an electrolytic solution to be used or a processing target. You may make it use.

Various electrolytes can be used as the electrolyte solution 10, but a neutral salt obtained by combining one or more of citric acid, tartaric acid, malic acid, sodium salt, potassium salt, and ammonium salt of lactic acid. Use one of the aqueous solutions. Since the carbon fiber constituting the electrode part 4 has very good electrical conductivity, the contact part between the stainless steel 5 and the electrode part 4 generates heat and becomes high temperature by energization. For example, no toxic gas is generated due to heat generation. Here, “toxic gas” refers to hydrogen phosphide, sulfuric acid gas, chlorine gas, hydrogen fluoride gas, etc., and sulfuric acid, phosphoric acid, or neutral salt aqueous solution such as sodium, ammonium, potassium or hydrofluoric acid. It is necessary to avoid the use of electrolytes that may generate toxic gases, such as those obtained by adding neutral salts such as fluoride to acidic solutions.

Further, according to experiments, when the stainless steel 5 is treated with an aqueous solution of neutral salt obtained by combining one or more of sodium salt, potassium salt, and ammonium salt of tartaric acid as the electrolytic solution 10, It has been confirmed that even if a spark occurs at the contact portion between the steel and the electrode portion, the corrosion resistance of the treated portion does not decrease and the corrosion resistance is higher than that of the untreated portion. Incidentally, it has been confirmed that when other electrolytes are used, if a spark is generated at the contact portion between the stainless steel 5 and the electrode portion 4, the corrosion resistance is significantly reduced even at the treated portion.

  In order to remove the oxide scale generated in the welded portion 50 of the stainless steel 5 using the oxide scale removing device having the above-described configuration, one electrode portion 3 is connected to the stainless steel 5 and the other electrode portion 4 is configured. An electrolytic solution is included in the carbon fiber bundle 42 and pressed against the welded portion 50 of the stainless steel 5, and a voltage supplied from the power supply unit 2 is applied between the electrode units 3 and 4 to conduct electricity. The carbon fiber bundle 42 of the electrode part 4 is flexible and can be brought into contact with the uneven surface of the welded part 50 evenly, and the oxide scale of the welded part 50 is reliably removed.

In addition, since the carbon fiber constituting the electrode part 4 has extremely good electrical conductivity, the contact part between the stainless steel 5 and the electrode part 4 is heated by heating and becomes high temperature. However, citric acid, tartaric acid, By using a neutral salt aqueous solution in which one or more of malic acid, lactic acid sodium salt, potassium salt, and ammonium salt are combined, a toxic gas is not generated from the electrolyte solution 10.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Power supply part 3,4 Electrode part 5 Stainless steel 21,22 Output terminal 23,24 Cord wire 42 Carbon fiber bundle 50 Welded part

Claims (2)

A method for removing oxide scale generated in a welded portion of stainless steel by electropolishing, and combining one or more of citric acid, tartaric acid, malic acid, sodium salt, potassium salt, and ammonium salt of lactic acid By using a neutral salt aqueous solution as an electrolyte, and energizing the carbon fiber bundle of the electrode part formed by bundling carbon fibers in a brush shape by pressing the electrolyte solution against the welded portion of stainless steel. A method for removing oxide scale by electropolishing, comprising removing oxide scale from the welded portion. An apparatus for removing oxidized scale generated in a welded portion of stainless steel by electrolytic polishing, comprising an apparatus main body and an electrolytic solution, and as the electrolytic solution, citric acid, tartaric acid, malic acid, sodium salt of lactic acid, A neutral salt aqueous solution in which one or more of potassium salt and ammonium salt are combined is used, and the apparatus body has a power supply unit and two cords drawn from an output terminal of the power supply unit Each electrode portion is provided at the tip of each of the electrodes, one electrode portion is connectable to stainless steel, and the other electrode portion is formed by bundling carbon fibers in a brush shape, and the electrolyte solution Is an oxide scale removal device by electropolishing that is held in the gaps between carbon fibers .

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