Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/10—Other heavy metals
  • C23G1/106—Other heavy metals refractory metals
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/36—Regeneration of waste pickling liquors
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G3/00—Apparatus for cleaning or pickling metallic material
  • C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G3/00—Apparatus for cleaning or pickling metallic material
  • C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
  • C23G3/023—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously by spraying

Definitions

• the present invention relates to an acid pickling process for metallic materials, in particular alloy steel, stainless steel or titanium alloys.
• the pickling of steel materials is done in a bath consisting of an aqueous solution containing ferric ions and hydrofluoric acid.
• This bath has the advantage of not containing nitric acid and therefore of not generating toxic compounds derived from nitric acid during pickling.
• hydrofluoric acid which can be dangerous to handle, it has been proposed in FR-A-2 657 888 to use non-oxidizing organic acids of iron, in particular formic acid or acetic acid.
• mineral acids such as sulfuric acid or phosphoric acid can also be used in the composition of such pickling baths.
• the pickling solution is sprayed on the part to be pickled.
• the solution is recovered after contact with the piece and is recycled in a closed circuit of pickling solution.
• the solution is usually regenerated by bubbling air or an oxygen-containing gas at a point in the recirculation circuit of the pickling solution.
• the object of the invention is to provide an acid pickling process for metal parts by spraying, in which the pickling speed is significantly improved during the entire period of use of the same solution.
• the object of the invention is also to improve the pickling speed of the processes of the aforementioned type in a particularly economical manner.
• the subject of the invention is a process for pickling metallic materials, in particular alloy steel, stainless steel or titanium alloys, using a pickling solution S containing ferric ions in an acid medium comprising at least one acid.
• halogen acid in particular hydrofluoric acid, a mineral acid, in particular sulfuric acid or phosphoric acid, and non-oxidizing organic acids of iron, in particular formic acid or acetic acid, in wherein said solution is sprayed onto the material, recovered and recycled in a closed circuit of pickling solution and said spraying is carried out in an atmosphere confined in a spray enclosure with an oxygen supply by introduction into the spray enclosure d '' a gas G containing oxygen.
• the pickling process of the invention can also be applied to alloys based on zirconium, cobalt or nickel, or to non-alloy steels.
• the materials to be stripped can be in the form of strips, wires, tubes, plates or any metal parts.
• the introduction into the confined atmosphere of an oxygen-containing gas makes it possible to maintain a high pickling speed throughout the pickling operation.
• the oxygen contained in said gas can be introduced, even partially, in the form of ozone.
• This oxygen supply can advantageously be carried out continuously by maintaining the circulation in the spraying enclosure of a gas G containing oxygen, and very advantageously by uniformly distributing the continuous circulation of said gas in the enclosure for ensure a homogeneous composition of the atmosphere in the enclosure.
• the oxygen content of said gas G containing oxygen is greater than 10%.
• the gas may for example be air.
• the flow rate of said gas G containing oxygen is at least equal to the spraying flow rate of said solution S.
• the flow rate of said gas G makes it possible to renew the atmosphere in the spraying enclosure on average at least every fifteen minutes, and preferably every five minutes.
• the supply of oxygen makes it possible to maintain an oxygen content of the atmosphere in the spray enclosure at least equal to 10%.
• the ratio between the spray rate of said solution S on the metal surface expressed in liters / minute and the surface to be stripped per unit of time expressed in square meters per minute is at least five.
• the pickling solution is sprayed in the form of small droplets which provide a large exchange surface between the sprayed liquid and the atmosphere prevailing in the spraying enclosure.
• the size of the droplets depends on the liquid and especially gas flow rates in said enclosure and is advantageously in the range corresponding to the atomization processes.
• At least part of the pickling solution is introduced into said enclosure by atomization.
• the stripping process can be discontinuous, the spraying of the parts to be stripped taking place in a closed enclosure provided with means for introducing oxygen.
• This enclosure can for example be a spray tunnel.
• the enclosure is also provided with means for introducing oxygen.
• an etching solution S which contains hydrofluoric acid and Fe 3+ ions, present in the form of fluorinated complexes, the concentration of Fe 3+ ferric ions being included between 1 and 150 grams per liter, and which has a pH between 0 and 3; it also contains Fe 2+ ions and its redox potential measured with respect to a saturated calomel reference electrode is between -200 mV and + 800 mV; such a pickling solution is described in particular in European patent application No. 0 188 975 filed by the applicant.
• the pickling speed remains durably much higher than the pickling speed that is would be obtained by immersion of said parts in said solution and oxidative regeneration by bubbling oxygen in said solution.
• the consumption and aging of the pickling solution can be monitored by measuring the redox potential and the pH of the solution in the recirculation circuit.
• the pickling process can be implemented by checking the re ⁇ ox potential of the solution.
• the value of the potential can be maintained at a predetermined value by modifying the flow rate of gas G introduced, by adding an oxidizing agent to the solution S in the recirculation circuit or by modifying the spraying rate of solution S.
• the control of the redox potential of the pickling solution proves to be particularly advantageous in the context of the present invention because it allows the use of the recycled pickling solution for a very long time with good pickling efficiency while spacing the interruptions for equipment maintenance.
• the present inventors have been able to determine that it is possible to carry out pickling by spraying with a solution having a sufficiently high redox potential, to ensure good pickling efficiency, but sufficiently low to limit the precipitation and crystallizations of ferric compounds and thus limit the risks of clogging in the installation, in particular at the level of the spraying members.
• the measurement of the redox potential of the pickling solution makes it possible, by comparison with the initial value of the potential of the solution at the start of pickling, to assess the aging of said solution or to detect any anomalies.
• a strong oxidation means temporarily supplementing and / or locally the action of the oxygen carrier gas introduced into the spray enclosure to quickly return to an advantageous redox potential allowing good pickling.
• the process according to the invention can be used for pickling with solutions containing ferric ions in acidic media comprising acids other than hydrofluoric acid, in particular organic acids, used in closed circuit and therefore requiring a regeneration by an oxidizing agent, for example by a gas containing oxygen or hydrogen peroxide, regeneration controlled by measuring the redox potential of the solution.
• an oxidizing agent for example by a gas containing oxygen or hydrogen peroxide
• the process of the invention remains economical by comparison with an immersion process where the same regulation of the redox potential is carried out .
• a smaller amount of auxiliary oxidant is used in the spraying process of the invention.
• the pickling solution is maintained in a predetermined temperature range, preferably at a constant temperature, with the exception of operating variations, in the closed solution recirculation circuit.
• a heating and / or reheating operation at any point of the recirculation circuit, according to any suitable technique.
• a stream of hot gas containing oxygen is circulated in the solution, advantageously a stream of hot air, so as to simultaneously heat and regenerate the pickling solution.
• the reheating preferably takes place just before spraying the solution.
• the method according to the invention applies to the continuous pickling, in particular of metal strips, and in discontinuous, in particular of metal wire crowns or metal parts.
• the invention also relates to a device for pickling by spraying surfaces of metal parts which implements a method as described above.
• This device comprises: - a spray enclosure provided with a receptri ⁇ tank,
• the device according to the invention may include one or more of the following characteristics: - said ventilation means deliver said oxygen-containing gas at a minimum flow rate representing the volume of said enclosure at least every fifteen minutes, and preferably every five minutes ;
• Said means for spraying said pickling solution are of the pneumatic atomization type
• said means for spraying said pickling solution comprise means of the conventional spray type and of the pneumatic spray type.
• the device according to the invention may further comprise means for maintaining the temperature of said solution, which can provide heating or cooling.
• the pickling processes employ solutions at a temperature above ambient temperature which tend to cool during use.
• the temperature maintenance means are therefore preferably means for reheating the pickling solution.
• Reheating means may comprise a conventional heating tank by conduction or alternatively means for insufflation in the solution of a hot gas containing oxygen, in particular hot air, these two types of means possibly being associated. They are preferably arranged just upstream of the spraying means.
• the device can further comprise liquid / solid separation means, in particular by decantation, to rid the pickling solution circulating in a closed circuit of the solid particles resulting from pickling which are entrained with the solution. in the receiving tank.
• said separation means can be provided with means for blowing a hot gas containing oxygen into the zone where the liquid resides.
• the device can advantageously include control means comprising at least one measurement probe, in particular the temperature, pH or redox potential of the solution, located at any point of the circuit for recirculating the pickling solution.
• control means may in particular comprise a probe for measuring the redox potential of the pickling solution.
• the device may also comprise means for injecting an oxidizing agent, in particular hydrogen peroxide, into the recirculation circuit of said solution, controlled by said potential measurement probe.
• an oxidizing agent in particular hydrogen peroxide
• said ventilation means can be provided with a gas flow control valve controlled by said potential measurement probe.
• said spraying means can be provided with a valve for adjusting the flow rate of solution controlled by said potential measurement probe.
• FIG. 1 is a schematic view of a device for continuously stripping metal strips by spraying according to the invention
• - Figure 2 is a sectional view of the device of Figure 1 showing two spray bars of the pickling device according to the invention
• - Figure 3 is a side view of a device spraying of metal wire crowns, forming part of a pickling device according to the invention.
• the device represented in FIG. 1 comprises a spraying enclosure, means for spraying a pickling solution into said enclosure, means for ventilating said enclosure, control means, recirculation means, treatment means and means for maintaining the temperature of said solution.
• Said spraying enclosure comprises a tunnel 1 provided with a receiving tank 2 and a cover 3, an entry airlock 4A and an exit airlock 4B for the strip to be scoured and means for transferring the said strip strip composed of rollers 5 which define a strip path or pickling plane P.
• the spraying means comprise spray booms 6 parallel to the rollers 5, regularly spaced apart and arranged above and below said pickling plane P, as shown in detail in FIG. 2; the booms 6 are rigid tubular conduits which open into a multitude of spray nozzles 7 arranged regularly along the boom 6. Said spray nozzles 7 are of a type known per se intended to produce a flat jet.
• the distance between the orifices of the nozzles 7 of the pickling plane P along the direction of the jet is between 5 cm and 70 cm, and preferably equal to approximately 30 cm.
• the nozzles 7 of the same ramp 6 are oriented to create flat jets which extend over the width of the strip path and the distance between the nozzles 7 is less than the width of the jet at the pickling plane P of such so that the flat jets of each nozzle of the same ramp partially overlap over the entire width of the strip path, as shown in FIG. 2.
• the ventilation means include a supply circuit and a gas evacuation circuit from the enclosure. These circuits are preferably adapted in a manner known per se to ensure a homogeneous composition of the atmosphere of the enclosure.
• the ventilation means of the tunnel comprise a fan 8 connected to one end of the tunnel by a gas supply pipe and a gas evacuation chimney 9 located at the other end of the tunnel.
• the intake of the fan 8 is connected to an air suction mouth not shown and the fan is provided with a flow control valve not shown; the chimney 9 is connected to a gas treatment device (not shown) which allows the recovery of part of the mist or droplets discharged in the gas flow.
• Said recirculation means comprise a buffer tank 10 connected to the receiving tank 2 and a pump 11 for re-injecting under pressure the solution coming from the buffer tank 10 towards each of the ramps 6.
• the pump 11 has characteristics which make it possible to supply said ramps at a pressure of between 0.5 ⁇ 10 5 and 7.10 5 Pa, and preferably equal to 3.10 5 Pa; pump 11 is fitted with a flow control valve not shown
• the buffer tank 10 is provided with a feed orifice, in particular to supplement the quantity of pickling solution S.
• Said control means consist of a redox potential measurement probe implanted at the level of the buffer tank 10, not shown.
• said redox potential measurement probe can be installed at other points in the recirculation circuit of the pickling solution.
• Said processing means comprise a decanter 12.
• the decanter 12 is installed on a secondary recirculation circuit connected to the buffer tank 10, the flow rate of which is regulated by a pump 12 '; the decanter 12, known in itself, is not described here in detail and is provided with a discharge of solid residues R.
• Said temperature maintenance means comprise a heater 13 which is installed on the pipe connecting the pump 11 to the ramps 6; the heater 13, known in itself, is not described here in detail.
• the method according to the invention is used HERE to strip a strip of stainless steel B of width Lb.
• the buffer tank 10 is filled with a pickling solution
• the means for spraying, recircu ⁇ lation, treatment and heating of the pickling solution are started up as well as the means for ventilating the spray tunnel 1.
• the strip B is continuously passed through the spray tunnel 1 on the rollers 5 at a running speed Vb, successively by the entry airlock 4A then the exit airlock 4B.
• the total volume of the spray tunnel being V in m 3 , using the fan flow control valve 8, the air flow pushed by said fan 8 into said tunnel is adjusted to V / 15 m 3 / minutes, so that the atmosphere of said tunnel is on average renewed at less every fifteen minutes, and preferably every five minutes.
• the strip B When passing through the spray tunnel 1, and in particular between the spray booms 6, the strip B is sprayed homogeneously on both sides by the pickling solution S sprayed by the nozzles 7 of the booms 6.
• the spent solution comprising solid pickling residues in suspension is poured by gravity into the receiving tank 2 and then into the buffer tank 10.
• the redox potential measurement probe makes it possible to measure the redox potential of the solution S in the buffer tank 10.
• the solid residues of solution S are separated by the decanter 12 when said solution passes through the secondary recirculation circuit connected to the buffer tank 10.
• the solution S is reinjected by the pump 11, freed of solid residues in suspension, towards the ramps 6 and the spray nozzles 7, by reheating it by the reheater 13.
• the heater 13 advantageously maintains the temperature of the solution between 15 and 80 ° C, and preferably between 40 and 70 ° C.
• the solution S is sprayed continuously on said strip in an atmosphere constantly renewed in oxygen and recirculates in a closed circuit in the pickling device.
• the value of the redox potential measured by the probe can be maintained at a value predetermined constant by modifying the air flow rate of the fan 8 or by adding to the buffer tank 10 an additional oxidant more powerful than air, for example a peroxide, a persalt or ozone, or by modifying the flow rate spray.
• the spray nozzles 7 are replaced by pneumatic atomization nozzles supplied as before with liquid by the pump 11 and supplied with pressurized gas by an air compressor or an oxygen-containing gas.
• the pneumatic atomization nozzles are known per se and are not described here; the characteristics of the pump 11 are adapted to the specifications for supplying liquid to said nozzles.
• the solution S is advantageously sprayed on the two faces of the strip to be stripped and the atmosphere of the stripping tunnel is advantageously renewed at the level of the spraying means themselves by pneumatic atomization itself.
• the spray tunnel is vertical; this arrangement can be advantageous for the pickling of wires or metal tubes.
• the device is suitable for pickling crowns or coils of metal wire. It comprises a spray enclosure, provided with a support for the crown, means for spraying a pickling solution on the crown in said enclosure, control means, recirculation means, treatment means and means. maintaining the temperature of said solution.
• Figure 3 shows a detail of such a device and illustrates the spraying of a wire crown
• the device comprises a support 14 in the form of a hook which supports on its lower part a ring of metal wire C.
• the spraying means comprise two spray bars 6 arranged above and below the wire ring C and provided with spray nozzles 7 similar to the nozzles
• the ramps 6 are arranged horizontally in the enclosure one above the other, the nozzles 7 of the upper ramp opposite the nozzles 7 of the lower ramp. They are sufficiently spaced that the coil C carried by the support 14 can be inserted into the intermediate space.
• the power and orientation of the jets produced by the nozzles 7 are such that the entire crown is brought into contact with the pickling solution.
• This spraying device can be integrated into a device for discontinuous pickling of wire rings, the support 14 being fixed relative to the closed and ventilated pickling enclosure. It can also be integrated into a device for continuously stripping wire crowns which comprises several pairs of ramps 6 defining a horizontal space in which circulate mobile supports 14 carrying crowns C and in which the stripping solution S is sprayed onto the succession of crowns C.
• the pickling of a steel plate is carried out by immersion in a pickling bath containing ferric ions and hydrofluoric acid.
• This solution is placed in a pickling tank provided with a redox potential measurement probe and air bubbling means in the bottom of the tank to stir the solution in the tank.
• Said plate is scoured by immersion in the tank and air is bubbled there at a flow rate of between 10 and 20 l / min.
• the bath temperature is maintained between 50 and 60 ⁇ C and the pH is maintained at its initial value by addition of hydrofluoric acid.
• the initial change in weight of the steel plate is measured every thirty seconds for two minutes, then the average change in weight after four hours and the change in the redox potential of the solution as a function of time over four hours, indicative of the aging of the solution.
• the spray device models a spray tunnel and includes an enclosure provided with a cover and a tank filled with the pickling solution S and provided with a redox potential measurement probe.
• the scouring plate is placed horizontally above the tank, approximately 30 cm below the spray nozzle.
• a fan ventilates the spray enclosure continuously.
• the pickling solution S is sprayed homogeneously over the entire surface of the plate; the used solution is collected by the tank under the plate; the pump extracts the collected solution and returns it to the spray nozzle.
• the temperature of the solution is maintained between 50 and 60 ⁇ C and the pH is maintained at its initial value by addition of hydrofluoric acid.
• the initial change in weight of the steel plate is measured every thirty seconds for two minutes, then the average change in weight after four hours and the change in the redox potential of the solution as a function of time over four hours.
• solution S has a much longer lifespan without adding more oxidizing agent. oxidizing than air, like oxygenated water
• the average change in weight in 3 hours is 10 g / m 2 / min.
• the average change in weight over 3 hours is 14 g / m 2 / min.
• the oxygen-jet method of the invention remains economical since it makes it possible to halve the quantity of this expensive reagent to achieve equal efficiency.
• Example 2 the same plate is etched by spraying under conditions identical to those of Example 1. The following results are obtained: - Initial change in weight: 33 g / m 2 / min; - Average variation in 4 h: 1 g / m 2 / min.
• the pickling solution used in the previous examples can be used for continuous pickling, in the spray tunnel, of a steel strip of grade AISI 304.
• the spray tunnel has a total volume of 50 m 3 . It is equipped at one end with a fan connected to an air intake vent blowing air into the tunnel at a rate of 3.5 rrrVminute.
• the steel strip 1.3 m wide, runs through the tunnel at a speed of 25 m / min.
• Common type spray bars have spray nozzles spaced 30 cm apart.
• the pickling solution pumped into the receiving tank of the tunnel feeds the spray bars at a pressure of 3.10 ⁇ Pa for a flow rate of 2 m 3 / min.
• a reheating device keeps the temperature of the pickling solution between 50 and 60 ⁇ C.
• This pickling device was able to operate for periods of several weeks while retaining a satisfactory redox potential with good pickling quality.
• This solution is used to continuously strip cold-rolled AISI 304 stainless steel strips in a spray tunnel with a volume of approximately 31 m 3 .
• This tunnel has three outlets connected to an air suction device and the air flow sucked in is 160 m 3 / mi ⁇ ; the three mouths are arranged regularly along one of the side walls of the enclosure, parallel to the strip running path.
• the tunnel is equipped with 32 spray bars arranged approximately 25 cm below and above the scrolling band and distributed regularly along the tunnel; each boom is fitted with spray nozzles uniformly spaced 35 cm apart.
• the ramps are supplied with pickling solution under a pressure of 3.10 5 Pa (3 bar) and deliver a total of 2 m 3 / min of solution.
• a reheating device keeps the pickling solution at around 75 ° C.
• the redox potential of the solution is maintained at 220 mV by regular addition of hydrogen peroxide.
• the 1.24 m wide steel strip runs through the tunnel at a speed of 48 m / min.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• ing And Chemical Polishing (AREA)

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• 1994
  • 1994-06-15 FR FR9407328A patent/FR2721328B1/fr not_active Expired - Fee Related
• 1995
  • 1995-06-07 DE DE69509527T patent/DE69509527T2/de not_active Expired - Lifetime
  • 1995-06-07 KR KR1019960706746A patent/KR100361114B1/ko not_active Expired - Fee Related
  • 1995-06-07 EP EP95922577A patent/EP0766751B1/de not_active Expired - Lifetime
  • 1995-06-07 US US08/727,630 patent/US6033485A/en not_active Expired - Lifetime
  • 1995-06-07 JP JP50171596A patent/JP3735691B2/ja not_active Expired - Fee Related
  • 1995-06-07 WO PCT/FR1995/000744 patent/WO1995034695A1/fr not_active Ceased
  • 1995-06-07 CA CA002190779A patent/CA2190779C/fr not_active Expired - Fee Related
  • 1995-06-07 AT AT95922577T patent/ATE179763T1/de not_active IP Right Cessation
  • 1995-06-07 KR KR10-2002-7007450A patent/KR100427795B1/ko not_active Expired - Lifetime
  • 1995-06-07 ES ES95922577T patent/ES2132680T3/es not_active Expired - Lifetime

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