JP4252010B2 - Steel pickling electrode - Google Patents

Description

  The present invention relates to an electrode used for electrolytic pickling treatment of steel materials.

  In the process of continuously plating the surface of a steel material such as a steel wire or a steel strip, the steel material is pickled before the plating treatment to remove the scale (oxide film) on the surface. One of the pickling treatments is electrolytic pickling. In electrolytic pickling, scale removal can be performed in a shorter time than chemical pickling by energizing a steel material immersed in an electrolytic solution such as sulfuric acid or hydrochloric acid.

  In the electrolytic pickling treatment, a current flows through the steel material indirectly by connecting the power source to the steel material and the electrode facing the steel material, and by connecting the power source to the anode and the cathode arranged opposite the steel material. There is an indirect energization method. In any energization method, the material of the electrode used in the state of being immersed in the electrolytic solution is selected in consideration of corrosion resistance and cost. In general, the electrode used as the anode is a platinum group which is not easily dissolved by the anode reaction. Titanium coated with a metal or its oxide is used. On the other hand, a stainless steel that is cheaper than the anode material is often used for the cathode in which the cathode reaction occurs, and among them, a SUS316 type having excellent corrosion resistance is often used (for example, see Patent Document 1). .

However, although the conventional cathode electrode formed of the above stainless steel does not cause electrochemical dissolution, it is inevitable that the mass is gradually reduced by being corroded by an acid that is an electrolytic solution. If the mass of the electrode decreases in the electrolytic pickling, the electric resistance in the electrolytic cell increases and the energized state deteriorates, so that the temperature and voltage rise and the electrolysis ability decreases. As the electrolytic capacity decreases, the scale and smut (dirt) are not sufficiently removed, and the surface quality and productivity of the steel material are adversely affected. For this reason, in general, electrode replacement is frequently performed in order to prevent the occurrence of poor quality due to a decrease in electrolytic capacity and the decrease in productivity, and the problem is that the electrode life is short.
Japanese Patent Application Laid-Open No. 64-4500 (page 5, FIG. 1)

  The subject of this invention is providing the electrode for steel pickling which is excellent in acid resistance and can obtain the stable electroconductivity over a long period of time.

  In order to solve the above-described problems, the present invention provides a steel pickling electrode used for electrolytic pickling treatment of steel materials in mass%, C is 0.03% or less, Si is 1% or less, and Cr is used. 22-24%, Ni is contained in 24-26%, Mo is contained in 5-6%, and the balance is made of stainless steel made of Fe and inevitable impurities.

  That is, SUS316L (mass%, C is 0.03% or less, Si is 1% or less, Mn is 2% or less, Cr is 16 to 18%, Ni is 12 to 15 which is generally used as a high corrosion resistance stainless steel. %, Those containing 2 to 3% of Mo), and not adding Mn, which is a component that deteriorates acid resistance, and the contents of Cr, Ni, and Mo, which are components that increase acid resistance, respectively. By increasing to the above range, the acid resistance was improved. Moreover, the upper limit of the component which raises acid resistance was determined in consideration of suppression of material cost.

  Since the steel pickling electrode of the present invention has improved acid resistance compared to the conventionally used high corrosion resistance stainless steel (SUS316L), the rate of corrosion weight loss by acid is slow and stable over a long period of time. Conductivity can be obtained. Therefore, in the electrolytic pickling treatment using this electrode, the cycle of electrode replacement, that is, the electrode life is long, and the processing cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an electrolytic pickling apparatus using the steel pickling electrode of the embodiment as a cathode plate 1. This electrolytic pickling apparatus is of an indirect energization type for steel wire A, and is placed in an electrolytic tank 3 filled with electrolytic solution 2 so as to face the steel wire A traveling in the direction of the arrow in the figure. A plate 1 and an anode plate 4 are arranged, and a power source 5 is connected to each of these electrode plates 1 and 4 so that a current flows through the steel wire A indirectly. The steel wire A has a diameter of 0.7 to 2.5 mm, is supplied to this apparatus from a heat treatment (patenting) process, and is sent to a plating process after electrolytic pickling. In this apparatus, a plurality of steel wires A can be simultaneously processed by passing them through the electrolytic cell 3 in parallel.

  The electrolytic solution 2 is concentrated sulfuric acid having a concentration of 25 to 30% and a temperature of 40 to 50 ° C., sent from the storage tank 6 to the electrolytic tank 3 through the feed pipe 8 by the pump 7, and returned from the electrolytic tank 3. 9 is returned to the liquid storage tank 6.

Each of the electrode plates 1 and 4 is supplied with a current from the power source 5 via the rectifier 10 so that the current density is 30 to 40 mA / cm ² . In this device, two anode plates 4 and one cathode plate 1 constitute one set of electrode plate rows, and each electrode plate row has a rectangular shape with a side of about 1000 mm.

  The cathode plate 1 contains, by mass%, C of 0.03% or less, Si of 1% or less, Cr of 22 to 24%, Ni of 24 to 26%, and Mo of 5 to 6%, and the balance. Is made of stainless steel made of Fe and inevitable impurities. On the other hand, the anode plate 4 is made of titanium with an iridium oxide coating.

  This electrolytic pickling apparatus has the above-described configuration. When performing the pickling process, an electric current is passed through each of the electrode plates 1 and 4 so that the portion facing the cathode plate 1 of the steel wire A is added to the positive electrode plate. 4 is charged negatively and the steel wire A is energized indirectly. As a result, in the positively charged portion of the steel wire A, the anode reaction occurs and the substrate and scale are dissolved in the electrolyte 2, and in the negatively charged portion, a large amount of hydrogen gas peels off the scale. The scale can be efficiently removed in a shorter time than chemical pickling.

  Here, the cathode plate 1 does not contain Mn, which is a component that degrades acid resistance, compared to SUS316L, which is a typical representative high corrosion resistance stainless steel, and is made of Cr, Ni, and Mo that are components that increase acid resistance. Since it is formed of stainless steel having a high content and has extremely high acid resistance, the rate of corrosion weight loss by the electrolytic solution 2 is slow, and stable current conduction can be obtained over a long period of time.

Next, in order to confirm the performance of the cathode plate, the following experiment was performed. In the experiment, first, in addition to the stainless steel (Example) used as the material for the cathode plate, a plurality of comparative materials generally considered to be excellent in acid resistance were prepared, and a sulfuric acid resistance test was conducted in a non-energized state and a conductive state. To compare the weight loss. The comparative materials are SUS316L (Comparative Example 1), lead (Comparative Example 2), and two types of Ni—Cr—Mo alloys (Comparative Examples 3 and 4) having the following composition (numerical values are mass%).
Comparative Example 3 C ≦ 0.015, Si ≦ 0.08, Cr: 19.0, Mo: 19.0, Ni: Balance
Comparative Example 4 C ≦ 0.015, Si ≦ 0.018, Cr: 20 to 22.5, Mo: 12.5 to 14.6, Ni: Balance

  Tables 1 and 2 show the test conditions (composition of the test solution) and the weight loss of each experimental material in the non-energized state and the energized state, respectively. From these tables, it can be seen that the stainless steel of the example has less weight loss than each comparative example and is most excellent in acid resistance, regardless of the presence or absence of energization and the composition of the test solution.

  Next, when the weight loss was measured by using the cathode plate of the embodiment for 3 months in the above-described electrolytic pickling apparatus, the weight loss was only 0.3%, and the acid resistance of this cathode plate was extremely high. It was confirmed that the electrode life was long.

  The electrode of the present invention is not limited to the cathode of an indirect energization type electrolytic pickling apparatus intended for steel wires as in the embodiment, but is also applied to a cathode in the case of using a steel material as an anode in a direct energization type apparatus. it can. Of course, the present invention can also be applied to the cathode of an electrolytic pickling apparatus for steel strips regardless of the energization method. On the other hand, if the present invention is applied to the anode of an electrolytic pickling apparatus, the material cost can be greatly reduced even if the electrode life is somewhat shortened compared to the case of using a conventional anode material.

Schematic of an electrolytic pickling apparatus using the steel pickling electrode of the embodiment as a cathode

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cathode plate 2 Electrolytic solution 3 Electrolytic tank 4 Anode plate 5 Power supply 6 Liquid storage tank 7 Pump 8, 9 Piping 10 Rectifier

Claims (1)

  In the steel pickling electrode used for electrolytic pickling treatment of steel materials, by mass%, C is 0.03% or less, Si is 1% or less, Cr is 22 to 24%, Ni is 24 to 26%, Mo An electrode for pickling a steel material, characterized in that it is made of stainless steel containing 5 to 6% and the balance being Fe and inevitable impurities.

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