WO2014011074A1 - Procédé de traitement électrochimique - Google Patents

Procédé de traitement électrochimique Download PDF

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Publication number
WO2014011074A1
WO2014011074A1 PCT/RU2012/000566 RU2012000566W WO2014011074A1 WO 2014011074 A1 WO2014011074 A1 WO 2014011074A1 RU 2012000566 W RU2012000566 W RU 2012000566W WO 2014011074 A1 WO2014011074 A1 WO 2014011074A1
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WO
WIPO (PCT)
Prior art keywords
pulses
current
polarity
chromium
value
Prior art date
Application number
PCT/RU2012/000566
Other languages
English (en)
Russian (ru)
Inventor
Вячеслав Александрович ЗАЙЦЕВ
Насих Зиятдинович ГИМАЕВ
Тимур Рашитович ИДРИСОВ
Original Assignee
Общество С Ограниченной Ответственностью "Есм"
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Общество С Ограниченной Ответственностью "Есм" filed Critical Общество С Ограниченной Ответственностью "Есм"
Priority to PCT/RU2012/000566 priority Critical patent/WO2014011074A1/fr
Publication of WO2014011074A1 publication Critical patent/WO2014011074A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
    • C25D5/611—Smooth layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/18—Electroplating using modulated, pulsed or reversing current
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance

Definitions

  • the present invention relates to the field of metalworking, in particular, to electrochemical dimensional processing and can be used in the manufacture of complex shaped surfaces of machine parts and forming tools from chromium-containing steels and alloys operating in an aggressive environment and high friction.
  • it is aimed at creating a protective chrome layer on a machined surface of a part during one technological operation, which has a low roughness - a mirror gloss, and provides high corrosion resistance and a low friction coefficient, as well as a decrease in the concentration of toxic hexavalent chromium ions in the spent electrolyte solution .
  • the disadvantage of this method is that the application to the interelectrode gap (MEP) of a constant voltage below the decomposition potential of the electrolyte, firstly, does not improve accuracy, since the localization of the process decreases due to the constant charge of the double electric layer at the metal-electrolyte interface anodic dissolution and, secondly, does not provide an increase in surface quality (decrease in roughness and increase corrosion resistance), due to the fact that the conditions for creating the surface of the part of a high-quality lame layer. Disadvantage is also the lack of information about when and under what conditions a layer of chromium should be created and how to control its occurrence.
  • a disadvantage of the known method is that the conditions for creating a chrome layer having a mirror shine and a decrease in the concentration of toxic hexavalent chromium ions in the spent electrolyte solution in the treatment of chromium-containing steels and alloys are not defined. In addition, the constant alternation of the forward and backward half-waves will lead to the anode
  • the direct half-wave will simply dissolve the layer of chromium even if it arises there with the reverse previous half-wave. There is also no information about at what point and under what conditions a layer of chromium should be created and how to control its occurrence.
  • Patent Number 4,213,834, B23H3 / 02; B23NZ / 00 / Jul. 22, 1980] in which a signal characterizing the distortion of the shape of the voltage pulse (when using a current source) is used to conduct the process at small interelectrode gaps.
  • a signal characterizing the distortion of the shape of the voltage pulse when using a current source
  • 25 is proportional to the maximum value of the second derivative of the voltage in the pulse.
  • This method allows processing at the minimum possible interelectrode gaps, providing high copy accuracy when performing copy-and-flash operations using a hard electrode - tool (EI).
  • EI hard electrode - tool
  • creating a chromium layer on the treated surface which ensures the creation of a specular gloss on the treated surface, as well as reducing the concentration of toxic hexavalent chromium ions in the spent electrolyte solution during the treatment of chromium-containing steels and alloys. It is also not determined at what point and under what conditions a layer of chromium should be created and how to control its occurrence.
  • Umin is the minimum voltage value.
  • This method allows processing at the minimum possible interelectrode gaps, providing high copy accuracy when performing copy-firmware operations using hard EI.
  • a known method is ECHO of an electrically conductive part in an electrolyte by applying bipolar pulses between the part and the electrically conductive electrode, in which one or more current pulses of direct polarity alternate with voltage pulses of reverse polarity [United States Patent, Patent Number 5,833,835, B23H3 / 02; B23H3 / 00; Nov. 10, 1998].
  • a reverse polarity pulse is supplied at relatively large interelectrode gaps, when the oscillating electrode is removed from the surface of the workpiece being processed over a large distance, and this reduces the efficiency of the pulses reverse polarity to obtain a shiny surface by precipitation of chromium from an electrolyte. So, at large gaps, the hydraulic resistance of the MEC decreases, the electrolyte speed increases and the flow is turbulized, which prevents relatively slow cathodic deposition processes. Changing the external pressure at the entrance to the MEP with a frequency of 10-100 Hz is technically difficult to implement.
  • the direct half-wave will simply dissolve the layer of chromium even if it occurs there in the previous previous half-wave.
  • each of the known ECHO methods separately when processing parts of chromium steels does not provide, within the framework of a single technological operation, the achievement of high copying accuracy, and the creation of a chromium layer having a specular gloss on the treated surface, as well as a decrease in the concentration of toxic hexavalent ions in the spent electrolyte solution chromium.
  • the objective of the present invention is to improve the quality of processing by creating on the treated surface a layer having a specular gloss, and reducing the concentration of toxic hexavalent chromium ions in the spent electrolyte solution by processing on. small interelectrode gaps with pulses of direct polarity at high current density, creating a polished surface and subsequent deposition of chromium pulses of reverse polarity on the treated surface to create a mirror shine.
  • the problem is solved by the fact that by the method of electrochemical treatment of chromium-containing steels and alloys in electrolytes based on aqueous solutions of alkali metal nitrates, including the processing of the part by current pulses supplied synchronously with the phase of maximum approximation of the oscillating electrode-tool and the part when adjusting the feed speed of the electrode-tool or the parts according to the invention first carry out electrochemical treatment with working pulses of current of direct polarity, forming in the electrolyte zone the layer adjacent to the surface of the part enriched with chromium ions, then, upon reaching the specified processing depth, shape and size of the part, the working pulses of the current of direct polarity and the electrode supply of the tool are turned off, a group of test high-frequency pulses of current of the direct polarity are turned on, and the value of the residual polarization is measured on the interelectrode gap, then reverse current pulses are turned on, supplied synchronously with the phase of maximum approximation of the oscil
  • the upper limit of the amplitude and duration of current pulses of reverse polarity is limited from the condition that there is no raster of the working surface of the electrode-tool, and the lower limit of the amplitude and duration of reverse current pulses polarity is limited due to the formation of a continuous chrome layer on the treated surface of the part.
  • the duration of the test high-frequency current pulses of direct polarity is set in the 5th range of 10-50 ⁇ s with a frequency of 5-10 kHz, and the voltage amplitude of 6 - 8 V.
  • the value of the increment of the residual polarization relative to its value after the working pulses of the current of direct polarity is established empirically on the first 2-3 parts from the batch.
  • the pressure of the electrolyte at the inlet of the interelectrode gap is reduced to 50-150 kPa and chromium is deposited.
  • the interelectrode gap when processing by working pulses of current of direct polarity, the interelectrode gap
  • the processing of working current pulses of direct polarity is carried out under the following conditions: voltage at the MEP 5-15V, the pressure of the electrolyte at the input of the MEP 50-500kPa, the concentration of the electrolyte 7-15% and the temperature of the electrolyte 18-40 ° C, providing current density 50-1000A / cm2.
  • the value of the residual polarization is measured at the end of the last test pulse at the starting point of the decay curve of the residual polarization, while the duration of the group of test high-frequency pulses of the current of direct polarity is selected from the condition that the residual polarization value reaches a steady state value.
  • figure 1 depicts a process diagram according to the invention
  • figure 2 depicts the waveform of the voltage and current in the MEP at the stage of forming pulses of direct polarity and at the finish stage when the deposition of chromium on the treated surface, according to the invention
  • S is the trajectory of the oscillating electrode - the tool, mm depending on the time t, sec
  • U is the voltage of the pulses of direct polarity
  • V is the voltage of the residual polarization after the test pulses after the shaping stage, V
  • j is the technological current density of pulses of direct polarity, A / cm 2 .
  • FIG. Za depicts the waveforms of the residual polarization voltage after the pulses of direct polarity determined by high-frequency pulses of direct polarity (curve 1), and the waveforms of the current of high-frequency pulses (curve 2) in the MEP at the stage of shaping by pulses of direct polarity,
  • FIG. 36 shows the waveforms of the residual polarization voltage after pulses of reverse polarity determined by high-frequency pulses of direct polarity (curve 1), and the waveforms of the current of high-frequency pulses (curve 2) in the MEP on the final stage when processing pulses of reverse polarity during the deposition of chromium on the treated surface,
  • figure 4. depicts the structure of a control system for a technological current generator and a reverse polarity current source of an electrochemical machine according to the invention; where: 3 -controlled source of technological current; 4 - controlled current source of reverse polarity; 5 - controlled source of test pulses of current of direct polarity; 6 - electronic key to turn on the technological current source; 7 - electronic key to turn on the current source of reverse polarity; 8 - electronic key to turn on the source of test pulses, 9 - automatic process control system, 10 - generator control unit.
  • Figure 5 depicts the appearance of the surfaces of the machined parts with their corresponding profilograms after ECHO using unipolar current pulses of direct polarity (A) and after reverse polarity pulses of ECHO (B) according to the proposed method;
  • the essence of the technological scheme of pulsed bipolar electrochemical processing (ECHO) by vibrating EI used on machines of the ET series is as follows ( Figure 1).
  • the electrode-tool 1 makes periodic oscillations S (t) relative to the workpiece surface of the electrode-workpiece (parts) 2, coaxial with the feed direction V, First, in the region of the phase of closest proximity of the electrodes, a working pulse or a group of current pulses of direct polarity, high density (in the range of 50 ...
  • test high-frequency pulses of direct polarity current are switched on again to determine the residual polarization voltage after reverse polarity pulses U E.
  • low-voltage pulses of reverse polarity current are turned on again, and cathodic deposition of chromium onto the treated surface from the electrolyte is repeated at small interelectrode gaps.
  • test high-frequency pulses of direct polarity current are switched on again to determine the total value of the residual polarization after the reverse polarization pulses UE, this is repeated until the necessary increment of the residual polarization value is obtained.
  • the measurement of the polarization values UA and U is determined after turning off the current, due to which the ohmic component is excluded from the measured voltage value and the reliability of measuring the difference between U A and U B , which is taken as an informative parameter about the enrichment of the treated surface with chromium, is increased (Fig. 3).
  • Test pulses provide a recharge of the capacitance of the double electric layer, establishing the polarization value, the components of which are the anodic and cathodic potentials.
  • the cathode potential is established faster than the anode one and its steady-state value at a fixed current density has a stable value, and the value of the anode potential depends on the properties of the treated surface and makes the main contribution to the increment of the residual polarization U A and U E.
  • the duration of the group of test high-frequency current pulses of direct polarity is selected from the condition that the residual polarization of the steady state is achieved.
  • test high-frequency pulses of current of direct polarity can provide more favorable conditions for the deposition of chromium on the treated surface, as it is considered (Povetkin V.V. Structure of electrolytic coatings / V.V. Povetkin, I. M. Kovensky. - M .: Metallurgy, 1989. - 136 s), that the best way to prepare the surface for metal deposition is electrolytic polishing, which provides a large number of nuclei and good adhesion to the substrate.
  • the invention is implemented as follows:
  • the proposed method for the electrochemical treatment of chromium-containing steels in electrolytes based on aqueous solutions of alkali metal nitrates is carried out in a flowing electrolyte with superposition of vibrations on one of the electrodes (Fig. 1).
  • a power source 3 of direct polarity a source with a steeply falling current-voltage characteristic (Fig. 4) is used, which is periodically connected to the MEP by an electronic switch to turn on the technological current source 6 in the region of the phase of closest proximity of the electrodes.
  • the closed-state time of the electronic switch on the technological current source 6 determines the duration of the current pulse of direct polarity.
  • the experiments were carried out in a 9.5% solution of sodium nitrate NaNO 3 at a current pulse density of ⁇ 100 A / cm and a pulse duration of 1.5 ms, current density and reverse polarity pulse duration of ⁇ 5 A / cm and 2 ms, respectively.
  • the moment of supply of working pulses and pulses of reverse polarity was synchronized with the phase of maximum approximation of the EI with the surface being treated.
  • the duration of the test pulses was 50 ⁇ s, the voltage amplitude was selected no more than 8 V.
  • the friction coefficient decreases and the fatigue strength, wear resistance and corrosion resistance increase.
  • the resistance of a tool steel punch for the manufacture of Togh recesses in steel screws increased by more than 2 times compared to a similar punch made by traditional technology (metalwork-mechanical method) and coated with titanium nitride. Similar results are expected when using punches in the manufacture of tablets (pharmaceutical industry).
  • chromium-containing steels are usually depleted in chromium. Due to the specifics of bipolar processing, according to the invention, they form chromium-containing layers on a wide range of chromium-containing steels and automatically control this process.
  • the proposed method of ECM by current pulses was implemented on an electrochemical copy-piercing machine model ET500 of the company ESM LLC, the material of the sample (part) and electrode-tool was 40X13 steel.
  • the treatment was carried out in a 9.5% aqueous solution of sodium nitrate to a depth of 5 mm with an area of 200 mm2.
  • Electrolyte temperature (° ⁇ ) - 20.
  • the electrolyte supply is direct through the central hole of the tool electrode.
  • the feed rate was 0.1 mm / min. Then, as the electrode-tool 1 further deepens into the workpiece 2, the electrolyte pressure is gradually increased to 350 kPa. In the process of processing by pulses of direct polarity, the feed rate was gradually increased until the first breakdown occurred, which corresponded to the feed rate of EI - 0.16 mm min, then the feed rate of EI was reduced by about 7% and the further processing was continued to a predetermined depth.
  • EI supply measured the value of the residual polarization by turning on the test high-frequency pulses of the current of direct polarity with a voltage amplitude of 8 V and a pulse duration of 50 ⁇ s.
  • low-voltage rectangular pulses of reverse polarity voltage were turned on, creating a current density of 5 A / cm and a duration of 2 ms, synchronizing the time of supply of reverse polarity current pulses with the phase of maximum electrode proximity and performing cathodic deposition of chromium onto the treated surface from the electrolyte at small interelectrode gaps periodically measuring the value of residual polarization with test high-frequency pulses of current of direct polarity.
  • reverse polarity current pulses alternated with test high-frequency pulses of direct polarity current, providing control of chromium deposition to the necessary increment of the residual polarization value relative to its value after direct polarity pulses, the value of which was previously determined on 2 ... 3 details this party.
  • the electrolyte pressure was reduced to 10 ° C, creating a laminar flow in the interelectrode gap, which provided good conditions for the deposition of chromium from the electrolyte composition onto the treated surface.
  • the amplitude and duration of the reverse polarity current pulses were limited from the condition that there is no raster of the working surface of the electrode-tool, but sufficient for the discharge of chromium ions on the treated surface of the part.

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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)
  • Electroplating Methods And Accessories (AREA)

Abstract

L'invention se rapporte au domaine du traitement électrochimique de pièces en acier et alliages contenant du chrome. Le traitement de la pièce s'effectue avec des impulsions de courant à polarité directe, après quoi on les stoppe en même temps que l'alimentation de l'électrode outil, et on déclenche un groupe d'impulsions test haute fréquence à polarité directe et on mesure la valeur de la polarisation résiduelle dans l'espace entre électrodes. On enclenche ensuite les impulsions de courant à polarité inverse qui sont envoyées simultanément avec la phase de rapprochement maximal de l'électrode outil en oscillation et de la pièce, et on effectue le dépôt de chrome à la surface en faisant alterner les impulsions de courant à polarité inverse et les impulsions de test haute fréquence à polarité directe tout en contrôlant le dépôt de chrome en termes d'augmentation de la polarisation résiduelle par rapport à sa valeur après le traitement par des impulsions de courant à polarité directe. L'invention permet d'améliorer la qualité de traitement grâce à la formation à la surface à traiter d'une couche à brillance miroir et de baisser dans la solution usée d'électrolyte la concentration d'ions toxiques du chrome hexavalent.
PCT/RU2012/000566 2012-07-13 2012-07-13 Procédé de traitement électrochimique WO2014011074A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114888379A (zh) * 2022-06-02 2022-08-12 江苏悦达起亚汽车有限公司 一种振动进给电解加工镍基高温合金阵列微方孔的方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU862493A1 (ru) * 1980-03-14 1988-07-15 Экспериментальный научно-исследовательский институт металлорежущих станков Способ изготовлени формообразующего инструмента дл электроэрозионной обработки
RU2038928C1 (ru) * 1990-10-10 1995-07-09 Гимаев Насих Зиятдинович Способ электрохимической размерной обработки
US5833835A (en) * 1995-07-18 1998-11-10 U.S. Philips Corporation Method and apparatus for electrochemical machining by bipolar current pulses
EP0998366A2 (fr) * 1998-04-06 2000-05-10 Koninklijke Philips Electronics N.V. Procede et montage d'usinage electrolytique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU862493A1 (ru) * 1980-03-14 1988-07-15 Экспериментальный научно-исследовательский институт металлорежущих станков Способ изготовлени формообразующего инструмента дл электроэрозионной обработки
RU2038928C1 (ru) * 1990-10-10 1995-07-09 Гимаев Насих Зиятдинович Способ электрохимической размерной обработки
US5833835A (en) * 1995-07-18 1998-11-10 U.S. Philips Corporation Method and apparatus for electrochemical machining by bipolar current pulses
UA29511C2 (en) * 1995-07-18 2000-11-15 Koninkl Philips Electronics Nv Method and device for electrochemical working by bipolar pulses and power source used in the method
EP0998366A2 (fr) * 1998-04-06 2000-05-10 Koninklijke Philips Electronics N.V. Procede et montage d'usinage electrolytique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114888379A (zh) * 2022-06-02 2022-08-12 江苏悦达起亚汽车有限公司 一种振动进给电解加工镍基高温合金阵列微方孔的方法

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