Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
  • C25F1/02—Pickling; Descaling
  • C25F1/04—Pickling; Descaling in solution
  • C25F1/06—Iron or steel
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F7/00—Constructional parts, or assemblies thereof, of cells for electrolytic removal of material from objects; Servicing or operating

Definitions

• the invention relates to a method and a device for the electrolytic pickling of flat metal products, in particular stainless steel and / or carbon steel strips.
• Metallic flat products are primarily metallic strips and plates.
• the invention can also be applied to metallic long products (for example wires, profiles, tubes) or even to metal surfaces.
• DE3937438A1 describes a way to pickle metallic surfaces, in combination of Fe 3+ salts and / or gaseous or liquid oxygen carrier, such as: H 2 O 2 , air and additional oxygen, which is obtained from anodic oxidation. In this case 0.5 to 1.0 A / dm 2 are introduced for the electrolysis.
• AT373922B discloses a method of electrolytic plating strip. This is a vertical arrangement of the electrodes. The electrolyte fluid is directed into the gap between the anode and belt. The voltage is stamped directly onto the belt - the cathodes are designed as power rollers.
• the object is achieved by a method according to claim 1 or by a device according to claim 15.
• at least one diamond electrode and / or at least one lead / tin electrode for example a lead93 / tin7 electrode
• the special property of diamond electrodes or lead / tin electrodes is the form of water decomposition. While water is usually split into hydrogen and oxygen during electrolysis, the diamond electrode and / or lead / tin electrode provides a working region in which, instead of oxygen, either ozone or highly reactive hydroxyl radicals are formed.
• One of the outstanding results of this invention is that the pickling times are significantly shortened over the conventional chemical descaling, and also over the conventional electrolytic pickling.
• the reason for this is the formation of highly efficient OH radical, oxygen in statu nascendi and simultaneous chemical removal or dissolution of the oxide on the metal surface.
• synthetic produced diamond electrodes and / or lead / tin electrodes can be formed in the electrolysis of the pickling solution, instead of oxygen here the extremely effective OH radicals. These oxidize all dissolved ingredients within the pickling solution.
• the diamond electrode and / or lead / tin electrode also has a high stability against aggressive pickling solutions.
• One possible embodiment of the invention provides that the current application takes place on the one hand directly on the flat product (for example via current rollers or current brushes) and on the other hand on a pair of electrodes. It can be provided, for example, that the flat product and an electrode are connected as the anode and the other electrode as the cathode. Oxygen in statu nascendi is generated by the direct application of the electrical current at the anode (on the flat product), and at the same time OH - radicals are formed by the use of the diamond electrode and / or lead / tin electrode as the anode Allow metal surfaces.
• the generation of the oxygen at the anode (steel strip or steel plate) and / or the formation of OH radicals at the anode (electrode) thus replace the nitric acid HNO 3 , wherein the pickling solution form the metal complexes and thus the surface of the stainless steel and / or C -Stahls from the scale can free.
• the pickling solution (mineral acids such as HF, H 2 SO 4 , H 3 PO 4 , HCl, mixed acid or Na 2 SO 4 ) serves here as a transport medium of the electrical direct current, and at the same time as a pickling solution for the chemical descaling of the steel surface.
• the metallic band can be oxygen in statu nascendi, generated by the anodic oxidation.
• the anode can also consist of a synthetically produced diamond electrode and / or lead / tin electrode, wherein the diamond is applied to a corresponding carrier material and made conductive by doping of suitable elements.
• Production methods for diamond electrodes are known to the person skilled in the art. Examples include the following types of production:
• a favorable embodiment of the invention is characterized in that the direct current is preferably stamped directly onto the flat product (strip) to be picked and the diamond electrode or lead / tin electrode. But it can also be provided that the direct current is continuously, ie constantly, abandoned.
• An advantageous development of this invention is characterized in that the
• electrolyte mineral acids, mixed acid and / or alkaline electrolytes such as Na 2 SO 4 can be used.
• the metallic flat product for example, a mixture of mineral acids and water in the concentration of 10 g / l to 250 g / l mineral acid can be used, the concentration of Mineral acids, in particular between 50 and 200 g / l, preferably 150 g / l.
• the electrolyte liquid may be a mixture of water and Na 2 SO 4 (sodium sulfate), wherein the electrolyte composition is specifically adjusted to the flat product to be picked and wherein the concentration of Na 2 SO 4 between 100 and 350 g / l, preferably 150 g / l Na 2 SO 4 .
• the electrolyte liquid mixed acid (mixture of HF and HNO 3 ) is used and the mixed acid composition is adjusted specifically to the flat product to be picked (band), wherein the concentration of the mixed acid between 20 and 100 g / l HF and 50 and 300 g / l HNO 3 , preferably 50 g / l HF and 150 g / l HNO 3 .
• the concentration of the mixed acid between 20 and 100 g / l HF and 50 and 300 g / l HNO 3 , preferably 50 g / l HF and 150 g / l HNO 3 .
• the electrolyte liquid mixed acid in which the concentration and composition corresponds to that which is usually used in the conventional chemical pickling.
• the direct current which replaces HNO 3 , no measures for the reduction of the inevitably resulting NO x need to be set.
• the use of urea, or hydrogen peroxide falls away.
• facilities can be provided to ensure that precise compliance with the pickling bath concentration is possible. This makes it possible to increase the quality of the surface of the flat product, for example the steel strip.
• the current densities (amperes per unit area) can be adjusted specifically to the flat product to be picked, the current densities at the electrodes being between 0.5 and 150 A / dm 2 .
• the electrolyte temperature can be adjusted specifically to the strip to be coated, wherein the electrolyte temperature between 20 and 90 0 C, preferably 75 0 C, is.
• a favorable embodiment of the invention is characterized in that the amount of electrolyte feed (pickling solution amount) in the gap is regulated between the diamond electrode pair and / or lead / tin electrode pair and the strip. This allows the belt to be hydraulically or mechanically positioned exactly midway between the pair of electrodes.
• An advantageous embodiment of the invention is characterized in that the gap between the diamond electrodes and / or lead / tin electrodes can be changed. Thus, the band can be easily adapted to the band ripple.
• Tape waviness is determined and the diamond electrodes and / or lead / tin - electrodes are removed from the tape, so that a contact between tape and diamond electrodes and / or lead / tin
• the adjustable distance between tape and diamond electrodes and / or lead / tin electrodes allows the current flow to be adjusted and, subsequently, a reduction in electricity costs.
• a possible embodiment of a device is a Beizzelle, where the direct electrical current is directly imprinted on an electrically conductive contact between tape and electrode (cathode and / or anode).
• It can guide means are provided with which a band can be performed at an angle to the horizontal, that electrodes are arranged at the same angle, and that means are provided, with which electrolyte fluid between the belt and electrodes can be introduced.
• a band obliquely at an acute angle, in particular an angle of 30 to 45 °, downwards and then after at least one guide roller obliquely at an angle, in particular an angle 30 to 45 °, are guided upward, so that the band and simple can be efficiently introduced into the Beizzelle.
• the cell is space-saving by the oblique arrangement.
• the space requirement is much less compared to the conventional chemical pickling plants.
• a very good tape guide results in that the tape has no slack.
• Pair of electrodes and the guide roller is adjustable normal to the direction of movement of the flat product.
• the electrodes and the pulley can be lifted during the introduction of the tape hydraulically and / or mechanically away.
• Such an inclined pickling cell can be used both in push pickling and in so-called contact pickling, since the introduction of the band by the unfolding of the diamond electrodes and / or lead / tin electrodes and simultaneous lifting of the deflection roller is considerably simplified.
• An advantageous variant of the invention is given by the fact that a control device for the feed quantity of the electrolyte liquid (pickling solution) is provided, wherein a separate control device is provided per liquid inlet between the belt and diamond electrodes and / or lead / tin electrodes, thereby the flow to the Bandwidth adapted and optimally used for bands of different widths. Due to the resulting hydraulic or mechanical guidance of the band, the position of the band can be adjusted in a targeted manner between the diamond electrode pairs and / or lead / tin electrode pairs.
• An advantage of the invention is that the old pickle, that is, the spent pickling solution, contains no nitrates and thus can be much cheaper and easier to regenerate. The energy expenditure in the hydropyrolysis of the old solutions are much lower than in conventional techniques.
• An advantageous variant of the invention is characterized in that
• Fig. 1 shows the scheme of a conventional pickling plant with chemical removal by the mixed acid
• Fig. 2 shows a plant according to the "neutral electrolyte" method
• Fig. 3 is a Beizzelle by the method according to the invention
• Fig. 4 shows a plant according to the inventive method.
• Fig. 1 shows a pickling tank 1 according to the prior art.
• the metal strip 2 is passed through the Abhaspei 44 through the degreasing tank 5, then cleaned with deionized water in the sink 4 to then in the pickling tank 1 with the mixed acid 3 (HF / HNO 3 ) to begin the chemical removal of the scale.
• the mixed acid 3 is passed from a pump 7 via a line 6 into the pickling tank 1 and via a line 8, for example, in an intermediate container 9, derived where the mixed acid 3 is recirculated again.
• the metered addition of a urea solution 10 takes place via a pump 11 directly into the pickling tank 1 and is made for environmentally conscious reason, thus the NOX content is reduced.
• the metal strip 2 is cleaned after the pickling tank 1 with deionized water in the sink 12 of adhering mixed acid, then freed by means of blowers in the dryer 16 from the water and rolled up on the reel 45.
• the metal strip 2 shows a pickling tank 1 according to the prior art.
• the metal strip 2 is passed through the electrolyte 3, for example Na 2 SO 4 , between the cathodes 34 and anodes 35.
• the distance between electrodes and tape is usually about 70 to 150 mm, wherein the metal strip 2 has a certain sag, which can be reduced by support rollers, for example in the center of the plant.
• the electrolyte 3 is discharged from a line 8, for example, into an intermediate container 9, and returned by a pump 7 via the line 6 to the pickling tank 1, from where the electrolyte 3 is recirculated.
• 3 shows a Beizzelle 13, which fulfills the function of the pickling tank 1, according to the
• the metal band 2 e.g. Stainless steel and / or C-steel strip, is guided into the gap between the electrodes 15 of a pair of electrodes.
• one electrode of a pair of electrodes 15 and a current roller 14 (or the metal strip 2) is connected to a rectifier 19.
• the respective upper electrodes 15 can be moved in the direction 20, and the deflection roller 14 'in the direction 20', so that the distance between the metal strip 2 and the electrodes 15 is adjustable. This allows optimal use of electricity.
• the electrolytic or pickling solution task 3 is again carried out by means of pump 7 via a line 6, wherein lines 21,21 ', 21 "21'” are provided, which the electrolyte 3 in the column 24,24 ', 24 ", 24'” between metal strip 2 and electrodes 15 feed.
• the electrolyte or pickling solution task can now be adjusted by the control valves 22,22 ', 22 ", 22'" to the required conditions.
• the electrolyte 3 After passage between the metal strip 2 and electrodes 15, the electrolyte 3 is collected in the lower part 23 of the electrolytic Beizzelle 13 and in turn fed to the pump 7.
• the spacers 25,25'25 "25 '" are arranged in the running direction of the band.
• the lower electrode is connected to the negative output of the rectifier 19, and the positive output of the rectifier 19 is connected to the current roller 14.
• the upper electrode 15 is connected to the negative output of the rectifier 19, the metal strip 2 is connected to the positive output of the rectifier 19.
• the electrodes 15, which are designed as diamond electrodes or lead / tin electrodes to be able to be operated as an anode, the direct current would have to be impressed alternately.
• a more advantageous embodiment of the invention (which is not limited to the concrete example) is to connect the lower electrode of the inlet side with the positive output of a rectifier, so that it serves as an anode.
• the metal band is also put on positive potential.
• the upper electrode is then connected to the negative output of the rectifier and serves as a cathode.
• the electrodes are reversed: the lower electrode serves as cathode, the upper as anode. In this way, both the top and the bottom of the tape in the range of OH radicals formed at the anode. It could be provided in this embodiment, both for the inlet side and for the outlet side only ever a rectifier 19.
• An alternative to the last possible embodiment is to switch the metal strip 2 de-energized, so only to act on the pair of electrodes as the cathode and anode with power.
• the treatment consists of a chemical and / or electrolytic degreasing 5 in order to clean the oiled band, and an electrolytic Beizzelle 13.
• the Beizzelle 13 is connected to 4 rectifiers.
• the arrangement of the electrode pairs 15 was chosen so that in each case only one pair of electrodes 15 is connected to a power roller 14 and to a rectifier.
• variable electrical voltages, pulsating, alternating and / or continuous can be embossed on the electrodes, which if necessary polish the surface of the metal strip 2.
• the metal strip 2 is deflected via the current rollers 14 and the deflection roller 14 '.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Electroplating Methods And Accessories (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2004
  • 2004-07-19 AT AT0121804A patent/AT413707B/de not_active IP Right Cessation
• 2005
  • 2005-07-08 TW TW094123142A patent/TW200604388A/zh unknown
  • 2005-07-11 CN CNA2005800311654A patent/CN101052752A/zh active Pending
  • 2005-07-11 MX MX2007000707A patent/MX2007000707A/es not_active Application Discontinuation
  • 2005-07-11 ZA ZA200701240A patent/ZA200701240B/xx unknown
  • 2005-07-11 EP EP05759974A patent/EP1781842A1/de not_active Withdrawn
  • 2005-07-11 BR BRPI0513474-9A patent/BRPI0513474A2/pt not_active IP Right Cessation
  • 2005-07-11 JP JP2007521848A patent/JP2008506847A/ja not_active Withdrawn
  • 2005-07-11 WO PCT/EP2005/007480 patent/WO2006008017A1/de active Application Filing
  • 2005-07-11 US US11/632,757 patent/US20070289878A1/en not_active Abandoned
  • 2005-07-11 RU RU2007105890/02A patent/RU2375506C2/ru not_active IP Right Cessation
  • 2005-07-11 AU AU2005263476A patent/AU2005263476A1/en not_active Abandoned
  • 2005-07-11 CA CA002573988A patent/CA2573988A1/en not_active Abandoned
• 2007
  • 2007-02-19 NO NO20070938A patent/NO20070938L/no not_active Application Discontinuation

Non-Patent Citations (1)

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