FR2518430A1 - METHOD AND HEAD FOR PROJECTING METAL COATINGS, IN PARTICULAR ON DIFFICULT ACCESS SURFACES - Google Patents

Abstract

THE INVENTION CONCERNS THE PROJECTION OF METAL COATINGS ON DIFFICULT ACCESS SURFACES. ACCORDING TO THE INVENTION, THE MELTING OF THE METAL WITH THE ELECTRIC ARC IS PROVIDED AND ITS SPRAYING BY MEANS OF A JET OF COMPRESSED GAS, AND THE MELT METAL IS APPLIED TO THE TREATED SURFACE BY MEANS OF A CLOSED SYSTEM OF THREE JETS OF SPRAYING, CONSISTING OF THE FOLLOWING JETS OF COMPRESSED GAS: A JET DIRECTED ALONG THE WIRES TO BE MELT, A SIDE JET 3 AND A COUNTER-CURRENT JET OF BLOWER 12, AGAINST THE HEAD, IN ADDITION TO THE NOZZLES FOR THE COMPRESSED GAS BENEFITLY DIRECTED, STILL CONTAINS A SPECIAL CONNECTION OF METAL WIRES 4 TO BE MELT, CONSTITUTING ELECTRODES TO A CURRENT SOURCE, IN THE FORM OF A SERIES OF RINGS 7 ELASTICALLY FIXED, INSIDE WHICH THE WIRES ARE MAINTAINED AND CONDUCTED. THE INVENTION APPLIES IN PARTICULAR TO THE INTERNAL SURFACES OF LONG LOW DIAMETER GLASS TUBES, FOUND THEIR APPLICATION AS ELECTRODES FOR OZONE GENERATORS.

Description

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  The invention relates to a method and a head for projection of metal coatings, especially on

  difficult access surfaces such as

  This process applies more particularly to

  to the coating of a metal layer on underneath surfaces of glass tubes, used as electrodes in

  ozone generators, in which the coating of

  it is the internal electrode of the discharge system.

  It is already known a projection metallization process which consists in that in the gaseous flame or in the electric arc is melting a wire material qpropri 6 and in that the molten metal is projected on the surface to be covered by a compressed gas jet This process is described in the second chapter of the memory aid Poradnik Metalizacji Natryskowej edited by PWT Warszawa

in 1959, pages 9 to 19.

  There is also a thermal projection device

  the internal walls of holes, equipped with a

  typical silencer, the nozzle of which constitutes the end

  end of the compressed air line is arranged axially-

  relative to it In the axis of the nozzle is provided a fusible wire in the acetyleno-oxygen arc Such a location of the nozzle and the templates of pistol oe implicate qoe for smaller holes the projection process is

  carried out from outside, directing the nozzle within one year.

  450 from the plane of the surface, and that for deeper holes, the projection process is

  applied, if the depth does not exceed twice the di-

  meter, both sides of the hole For an eagle less than 450

  the quality of the coating obtained is not satisfactory.

  For the projection of long holes of a fairly large diameter

  bearing, because of the jigs of the gun and its indispensable angle of inclination, an adapter is applied to

  the end, which is connected to the metalliser gun.

  With the aid of this device, it is not possible to

  the surfaces of small and long holes, or

  difficult access areas such as splines,

  Another defect is overheating

  This defect causes changes in the gas proportions, as a result of which the projected jet

  is unstable, unstable and there may be detonation

  This device is also described in this aide-memoire says Poradnik

  Metalizacji Natryskowej, pages 366, 367 and 368.

  There is also known a device in which is applied to melt the coating material an arc The projection nozzle of the arc gun is housed between two fusible metal wires Devices of this kind are built by the German company called OSU One can, by this medium, to cover holes with a diameter of less than 150 mm, but the coating obtained

  not uniform, being porous with coarse grains and

  non-uniform In devices that use the arc to melt wire, the power is turned on by rotary rollers

  on which the wire slips or is guided by

  These two methods have a characteristic of

  than a common negative: lack of continuity of functioning

  the electric arc, arising from the weak point of contact of the roller or wire guide with the wire; and

  often electrical contact stops.

  metal elements established by means of known processes and their implementation devices, are characterized by their low adhesion to surfaces, their susceptibility

  oxidation, their low uniformity and their large porosity

  During the process, the so-called surface layer

  glaze is damaged, and a metallic dust deposit

free harmful substances occurs.

  The object of the invention is to design a method

  laying a metal coating on the surface

  which is characterized by its good adherence to the

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  dielectric constituting a good conductor being durable.

  Another object of the invention is the design of a process

  in which the structure of the surface of the coating

  will not undergo any deformation, called glaze of the

  electrical system, as well as the crystalline system of this layer

  surface of the dielectric, and o the metallic dust

  that will not be deposited The invention still proposes the

  development of a projection arc projection device

  metal parts on difficult access surfaces, -

  especially on the cylindrical inner surfaces of dia-

  internal meters of 40 mm or more, by means of which the coating

  obtained is uniform and fine grained, presenting

  good adhesion to the surface-treated.

  The metal spray coating method according to the invention, consisting of the melting of the metal with the electric arc and its projection with a jet of compressed gas,

  characterized by the fact that the molten metal is

  on the treated surface by means of a closed system with three spray jets, consisting of gas jets

  following tablets: a jet directed along the metal wires

  fuses a side jet and a blowing jet.

  The lateral jet is directed from a certain angle on the

  treated in equi-current towards its movement of trans-

  unlike the desulfurizing jet, which also

  is directed from a certain angle-on the treated surface if-

  simultaneously against the current in relation to its movement

  of translation The quantity of gas constituting the jet

  Desulfurization is equal to 10 to 30% of the amount put to profit in the other jets The resulting jet of projected metal is directed at an angle of 450 to 600 towards the

treated surface.

  The projection head of metal coatings

  carrying out the process according to the invention, in its essential

  characterized in that it comprises a system of three-jet nozzles for the compressed gas.

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  is constituted by the nozzles of the central jet directed along the fusible metal wires, by a nozzle of the lateral jet directed at an angle towards the surface to be covered and by equidirection in the direction of its translational movement, and by a nozzle of the jet of blowing also directed at a certain angle towards the treated surface but

  counter-current in the sense of its translational movement.

  The connection of the metal wires between which the electric arc is created, to the current source, is realized by means of floating pads constituted by a series of

  rings mounted side by side, preferably copper,

  elastically inside the rings' are moving the metal wires, fixed in a way that allows their

  Continuous movement The wires are then con-

  in well-arranged wire guides, which is essential

  inside the jet of the central jet

  They are inclined at angles between 150 and 350.

  It is advantageous for the stabilization of the arc and the quality of the layer produced, that the inclination angle

  side nozzle is 600 in relation to the over-

  covered, on the other hand that of the nozzle of the

flage should be 45 -

  The application of a system with three jets of projection

  tion of the molten metal has eliminated the defects of the processes of the prior art, in particular by means of the désoufouflage jet,

  the free metal dust created during the

  in which we obtain a good quality of

  powder coating Because the main thermal jet is

  that it is low, and that it is further directed at a certain angle towards the covered surface, it is heated slightly, at most at 65 ', whereby the number of

  defects created during the process is close to zero.

  Power supply of metal wires

  ensures a permanent and uniform functioning of the

  tif, while simultaneously maintaining optimum projection parameters and long life of the various parts of the cast and spray assembly, as well as good arc stability, which is due to the housing of the wire guides in the nozzles and in the reciprocal positioning of the wires within the angular limits of 150 to 350. By the development of such a kind of projection head and a technology according to the invention, it has been

  possible to establish metal coatings on

  internal faces of glass tubes with a diameter of 50 mm

  and more than 2 mm wall thickness, which are used

  as electrodes in the ozonizers.

  according to the invention is characterized by a thin layer texture, a low oxidation rate, lower than that of flame metallization, and a good adhesiveness to the dielectric as well as a long

  durability The method according to the invention eliminates the

  annoying heating of the glass tubes before

  as is practiced by applying the method of metallization to the flame of glass tubes, also eliminating

  the application of expensive technical gases, such as oxy-

  Ene and acetylene The elimination of defects makes the technology according to the invention cheaper than those of the prior art. This process also improves the conditions of hygiene and occupational safety, since

  eliminates flame devices from the process, also eliminating

if the fire danger.

  Easy automation of the process undertaken

  the embodiment of the invention ensures the repetition

  production, as well as obtaining the parameters

very good coatings.

  The process according to the invention is illustrated in

the exemplary embodiment.

Example.

  55 glass tubes with a length of 1200 mm and a diameter of 50 mm are subjected to metallization.

  tubes are provided as ozonizing electrodes.

  be metallized under the same conditions The projection metallization head was introduced into the tube by a support arm The tube rotated at a speed of 200

  rpm with an advance speed of 40 mm / s.

  The metal melting temperature was generated between two aluminum wires. During metallization, the temperature of the tube wall was barely 30 ° C. The molten metal was sprayed at an angle of 450 ° C. relative to the generator of the tube This angle is the resulting angle by blowing compressed air along the

  tube, equidistant in the direction of movement of the tube to

  Tallise, and the other blowing in the opposite direction For the projection of the molten aluminum in the electric arc, compressed air was consumed in the amount of 60.0 normal liters per minute. of the tube 12

normal liters of air per minute.

  The invention will be better understood, and other purposes, features and advantages thereof

  will become clearer during the description

  explanatory text which will follow with reference to the accompanying schematic drawings given solely by way of example illustrating an embodiment of the invention, and in which: Figure 1 is a side view of the metallization head according to the invention; Figure 2 is a vie in axial section; and Figure 3 schematically shows a mode

  energizing the wires / electrodes.

  The body 1 of the head has the frenum of a nindustrial pipe narrowed in the front Close to the body 1 is located a

  air duct 2 terminated by a nozzle 3 of the lateral jet.

  f In the body 1 are housed metal wires 4 constituting

  simultaneously killing electrodes These wires 4

  converge at an angle of 200 and are housed

  In the same way, inside the nozzles 5 (FIG. 2), the central jet is arranged concentrically and inside the nozzles 5 are accommodated wire guides 6 of metal wires 4.

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  said metal wires 4 advance in resiliently fixed copper rings 7 which constitute floating slides. The tension is put on the rings 7 by means of electrical conductors 8 and a central conductor 10.

  The air is communicated to the nozzles 3 and 5 by a

central duit 9.

  In front of the front of the metallization head is disposed an air duct 11 terminated by a nozzle 12 of the jet

  The electric conductors 8 play simul-

  the role of elastic fasteners of the rings 7 implicitly

  permanent electrical contact with the metallic wire

  than in a manner as shown in Figure 3.

R E V E N I CAT I 0-N S

  1 Process for projecting metal coatings

  particularly on areas of difficult access, such as

  taking the metal cast in an electric arc created

  metal wires forming fuse electrodes fixed in a metallization head and spraying the molten metal by means of a jet of compressed gas, and its transfer to the surface to be coated which is relatively

  at the metallization head a relative movement of

  or translation with rotation, characterized in that the molten metal is applied to the surface by means of a closed system of three spraying jets, formed by a component of the central jet of compressed gas directed along the fusible metal wires. component of the lateral jet of compressed gas directed at an angle with respect to the treated surface and equidistant in the direction of the translational movement of the surface, and a component of the jet of blowing compressed gas directed angularly with respect to this treated surface but in counter-current in the sense of its translational movement, and in that the gas content of said desulfurizing jet is from 10% to 30% of the

remaining gas.

  Process according to Claim 1, characterized in that the resulting jet of projected metal is

  at an angle of 45 to 60 to the treated surface.

ted.

  3 Projection head of metallic clothing,

  particularly on surfaces with difficult access, by spraying

  production of two metal wires melted in an electric arc by means of a compressed gas, constituting electrodes, characterized in that it comprises a system * of nozzles with three jets of compressed gas, including a nozzle (5) of the central jet directed along the fusible metal wires (4), a nozzle (3) of the lateral jet directed angularly towards the surface to be covered by equating with, its movement of

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  translation and a nozzle (12) of the directed blower jet

  angularly towards the surface to be covered but against

  current to its translational movement, whereas the

  Metal wires (4) are fed to a current source by means of a series of elastically fixed rings (7) arranged side by side, in which the wires are mounted in a manner which allows them a continuous advancement, said wires (4) being

  ducts in wire guides (6) which are housed in the

  the nozzles (5) of the central jet.

Head according to claim 3,

  characterized in that the wires (4) are inclined

  reciprocally between them at an angle of 150 to 35.

Head according to claim 3,

  characterized in that the nozzle (3) of the lateral jet is

  with respect to the surface covered by an angle of

  600, against the nozzle (12) of the jet of blowing is in-

clicked at an angle of 450.