EP1022361B1 - Process for cleaning metals after their thermal treatment - Google Patents

Abstract

The appts. includes a pad which is made of an insulating fabric, and is placed between the electrode (10) and the metal (8) to be cleaned. It also includes a low-voltage alternating current source (2) which is connected to the metal (7) by means of the other electrode. The pad taking the form of a tubular sock (12) or a strip with a thickness of more than 1 mm is impregnated with an acid solution (18). The pad is made of a polyether ether ketone fabric with improved insulating properties.

Description

The invention relates to a device for the purification of metals after their processing at high temperatures, i. a device that eliminates the oxidation, staining or other phenomena that can cause high temperature processing such as welding and laser or plasma cutting of metals on the surface thereof.

The current state of the art knows a device which consists of a plug of glass fiber fabric, which is wrapped around the end of a beak-shaped electrode. This plug is soaked in an acidic solution based on phosphoric acid (81% by weight) and quinoline (0.01% by weight) and water, and then placed near the surface to be worked. In addition, a current source with alternating current and low voltage is present, one conductor of which is connected to the mass of the workpiece and the other conductor to the metal body of the plug holder. This results in the solution of the conditions of an electrolytic cell, which removes the oxide or stains in a short time.
However, in the system just described, the user's work is often disturbed by technical disadvantages resulting from the frequent maintenance and frequent replacement of the fiberglass insulation material, since this is burned due to the high heat development to which it is exposed or due to the tissue accumulate large amounts of dirt that prevent the formation of suitable electrical conditions, and because this plug must be soaked with the acidic solution often. Not soaking the device sufficiently often will result in mechanical damage to the tissue and a reduction in electrolytic action.
In addition, the dissolved residues remain so firmly on the treated surface that it must be washed several times before it can be finally dried. Moreover, by virtue of its characteristics, the acidic solution has a very high density, which is also required so that, when applied to vertical surfaces to be treated or to underside surfaces, it does not drip onto the operator or run down the wall.
In addition, it is not very practical for the operator to have a container of acidic solution and a large amount of fiberglass insulating fabric to wrap the electrode beak beside him, making the work non-continuous, and thus not very productive and sometimes too is dangerous.
The current state of the art also knows devices for the purification of metals with dilute acidic solutions - based on citric acid - which is continuously fed to the plug by means of an electric submersible pump installed in the acid tank.
However, due to the low performances and the low aggressiveness of the acidic solution, the above apparatus has never been industrially applied on a larger scale.
In addition, the current flowing through the electrode and surrounded by the plug heats up, since it is not only a good electrical conductor, but also a good conductor of heat: The temperature rise in this way due to the heat accumulated by the plugging leads to a rapid evaporation of said acidic solution, so that it can also lead to unwanted combustion of this Propfens, which in turn causes a short circuit between the electrode and the surface to be cleaned. Therefore, the plug must be replaced relatively frequently.
Finally, none of the previously known devices provide protection to the operator from during cleaning occurring fumes before.

This prior art can be improved in several ways in order to overcome the above drawbacks and to make the device safer and easier to use and to achieve a longer life of the graft.

From the foregoing, there is a need for a solution to the technical problem of reconfiguring the device and finding a new application of the electrolytic function for removing oxides, oxidations and stains from metals, as well as constructing the electrode and plug in such a way that the above-mentioned combustion phenomena are avoided.

With the invention, the above technical problem is solved by the use of the following device: apparatus for cleaning metals with a plug of insulating material placed between the electrode and the metal to be cleaned, a low voltage alternating current source connected to the other electrode Metal, with an acidic solution impregnating the plug, the plug consisting of a tubular stocking or an insulating fabric band of thickness greater than 1 mm, characterized in that the material for insulating the electrode has been improved; the plug is made of polyetheretherketone fabric (tradename PEEK from Hoechst) and wrapped around the metal end of the beak-shaped electrode.
In addition: The above-mentioned polyetheretherketone fabric can also be used in the form of a felt. In addition: The above-mentioned polyetheretherketone fabric can also be used in the form of a net, which is coated with a felt layer of any heat-resistant insulating material, which layer can be subsequently applied or provided directly in the production.
In addition: The above-mentioned fabric of polyetheretherketone may be coated with a felt layer, wherein this felt may consist of polyetheretherketone. In addition: The said layer of felt is applied to the beak on the outside of the fabric layer of polyetheretherketone.

In addition: The above beak may consist of a metal body and a removable end of insulating material in the interior of which at least one metal body is located, which ends at the end surface of the beak and activates the electrolytic action.
In addition: The said interchangeable end of the beak metal material is coated on the side walls with insulating material, so that in the contact area with the beak body and the non-insulated end surface is given electrical continuity. This end face is provided with holes through which the acidic solution is passed.
In addition: The said insulating coating consists of a Teflon film with a thickness of 0.1 - 0.3 mm to protect against short circuits and from 0.6 to 1.2 mm for thermal insulation.
Finally, the material used for the beak, ie both the body and the interchangeable metal end, can be selected from high-strength stainless steel. As a high-strength stainless steel for the interchangeable metal end, the steel grade AISI 316 should preferably be used.

This invention offers the following advantages: The supply of acid is done directly by the operator and as often as required; In this case, a very aggressive solution can be used, the loss of time for the impregnation of the prog is eliminated and no acid during transport from the container to the processing more can get lost. The plug is better soaked with acid and thus heats up less or wears less due to thermomechanical stress. The beak of the electrode can have a variety of shapes, which depend on the respective processing position; If the beak is cone-shaped, the sock can be changed more quickly. The supply of the acidic solution inside the prion avoids that acid is spilled or gets to parts not to be cleaned. The less concentrated acid, higher thinning and better suitability to remove treatment residues with a simple washing operation make the treatment more efficient and can be used for large scale productions, with a cost advantage over the prior art technique.
The life of the stocking, even though it is made of fiberglass, has been improved by the fact that the end of the electrode is made of insulating material, or if it is made of metal, by being coated with a thick insulating material layer existing electrode significantly improved.
Maximum life can be achieved by using a double layered plug having a fabric layer on the inside and a felt layer on the outside: The inside fabric can be polyetheretherketone.
With the polyetheretherketone fabric highest lifetime values can be achieved, as it has a very high resistance to heating and acids. The outer felt layer of any suitable material, such as the aforementioned glass fiber, maintains the solution at the cleaning site and allows for adaptation to the workpiece shape, thereby greatly increasing the life of the sock.
By using stockings with double polyetheretherketone layer, ie both the fabric and the felt, maximum performance in terms of service life, work precision and quantity can be achieved.
In view of the high material wear on the active end of the beak, the fact that the end of the beak is interchangeable makes it possible to make the beak of ordinary stainless steel, whereas the end can be made of special stainless steel, which is more expensive but less likely to wear. This results in an improvement of the efficiency of the cleaning process.

Figure 1 is an overall view of the acid feed and stocking apparatus of insulating fabric. Figure 2 is an enlarged view of the sock-wrapped beak of the prick. Figure 3 shows the hydraulic scheme of the pump sucking in the acidic solution. Figure 4 is the hydraulic / pneumatic scheme of the pump, which injects the air into the acid tank, causing the acidic solution to be discharged. Figure 5 shows the section through a billet with a frusto-conical metal insert and stocking of improved insulating material. Figure 6 is the section VI-VI through the frusto-conical insert. Figure 7 illustrates the inventive scheme of extracting the gases and vapors resulting from the heating of the acidic solution and their precipitation in the wet process. Figure 8 is a partial outline of a gun with improved replaceable beak with plug-in connection adapted to the respective ones Working position allows. Figure 9 shows the improved beak wrapped with the stocking of insulating material. Figure 10 is a rear elevational view of the improved beak showing the internal conduits are. Figure 11 is an outline view of the front of this beak. Figures 12 and 13 show the views of two beaks that are designed for the treatment of hard to reach places. Figure 14 is a view of a beak with a brush of insulating material to treat hard to reach areas. Figure 15 is the outline of the electrode whose end according to the invention is made of insulating material. Figure 16 is the enlarged section through a longitudinal plane of the beak of the electrode. Figure 17 is the view of a beak with a brush of insulating material for the treatment of hard to reach places. Figure 18 shows the section FF through the enlarged Figure 17 with limitation to two of the thread-like tubes. Figure 19 is an outline view of a double layer of special material for wrapping the beak. Figure 20 shows the end of the beak where the plug is wrapped in the double layer. Figure 21 is an outline view of a replaceable end metal beak bolted to the body and covered with a thick insulating layer.

It shows: with 1, Figure 1, the electrical supply unit, consisting of a transformer 2 for converting mains voltage into low voltage, a selector switch / 3 for regulating the output voltage, two terminals 4 for the conductors 5 and 6, one of which a forceps 9 to the body 7 of the surface 8 to be treated and the other to the body 10 of the electrode, which ends with the beak 11, which in turn is surrounded by the stocking 12, which is held by the clamp 13 connected; with 14 a small tube for supplying the acidic solution in or outside of the Iso-liergriffs 15, wherein the acidic solution by means of a pump 16 is sucked from the tank 17 containing the acid solution 18 and isolated from the rest of the apparatus; with 19 the tank cap with ventilation; at 20, Figure 2, the piece of stocking of insulating material fabric with which the beak 11 and the end of the body 10 of the electrode are wrapped; with 21 of bent at the beak tip and held by the clamp 13 sock; 22, a pump which compresses the air in the tank 23 and generates pressure which causes the acid solution 18 to flow into the tube 14; with 24 a check valve; at 25 a check valve in the aforementioned tube 14, which is mounted in the vicinity of the Propfengriffs.

Also shown are: at 26, Figure 5, the end of the electrode with the frusto-conical portion 27 into which a hollow beak 28 is inserted, also provided with a frusto-conical end 29 made flexible by the longitudinal cut 30; 31, the inner tube through which the acidic solution is passed and which is mounted with the seal 32 on the said end of the electrode and ends in the vicinity of the axial slot 33; 34, the insulating material fabric secured to said hollow beak with a ring 35 of resilient material or of hardening shrinkage material; with 36, Figure 7, near the beak-mounted slots for sucking the gases and vapors produced during operation; 37 with the anatomical handle with push button 38 for actuating the pump 16 or the valve 25; 39, a hose for extracting the said gases or vapors, which is connected to a centrifugal fan 40, which directs the gases into a suitable wet filter 41, whereupon the gases emerge cleaned out of the opening 42; 43, the tube in which the acidic solution is passed, and 44, the electrical conductor, possibly with a pair of wires to operate the pump 16, if this as an electric pump is equipped, equipped.

Also shown are: at 45, Figure 8, a standard handle with bent electrode body 46, operating button 47, similar to the pushbutton 38; 48 with the bayonet-type beak consisting of the slots 49 of the closure, a first portion 50 and a second slightly conical portion 51, and finally a tapered beak 52 connected to the end 53 of the acid solution well ends; 54 the stocking of the beak open and secured at the ends 56 and 57 by the clamp 58 or by an elastic member Isoliermaterialgewebe 55; at 59, Figure 10, said acidic supply bore which is tightly connected to the electrode 46 in the pilot bore 60 and in which the solution flows; with 61, Figure 12, a flattening of the beak 52 to accommodate the part of the open stocking 54 with three times the thickness and thereby reach smaller depressions can; at 62, Figure 13, a pointed and angled beak for the treatment of acute internal corners; at 63, Figure 14, a thin, tapered beak with a fine brush 64 with stiffened bristles 65 of insulating material: The bore 59 directs the acid solution into the center of this brush.

Also shown are: at 71, Figure 15, the body of the tapered metal beak that represents the electrode; 72, the end of this beak of insulating material with a bore 73 for supplying the acid solution to the stocking, which represents the plug and is not shown for clarity; with 74 the head of the screws for attachment to this body, which is mounted near the end face S: The shaft of these screws extends into the corresponding threaded hole 75, Figure 16; 76, the bore through which the acidic solution is directed into said body; with 77, the contact surfaces between the body 71 and the end 72: due to the sufficient flexibility of the material used, ie glass fiber reinforced Teflon, no seals are used. If leaks nevertheless occur, they are collected by the stocking of insulating material, not shown, which completely surrounds said electrode.

Also shown are: at 78, Figure 17, the body of the electrode with a brush with tubes of insulating material 79; 80, the bore through which the acidic solution is conveyed into the chamber 81 located in the metal head 82 of the brush in which the said tubes are inserted; at 83, Figure 18, the retaining block of said tubes of insulating material. In the figure, only two tubes are shown, but conveniently they should cover the entire area of said head; with 84 the bore of these tubes, through which the acid solution from the aforementioned chamber 81 passes into the metal bulge to be cleaned.

Finally, at 91, Figure 19, the plug consisting of a layer of insulating material 92, preferably formed of polyetheretherketone, and an insulating layer of felt 93; P being the width of the plug strip which is greater than the width of the beak for which the plug is intended; at 94, Figure 20, the end of the beak seen from the side around which the two sides of the graft of the previous figure are wrapped, with the fabric layer 92 inside and the felt layer 93 laid out on the outside; at 95 the bore through which the acidic solution is passed; with 96 an attachment ring made of insulating material, the plug 91st holding on said beak 94; 97 a metal beak with a replaceable metal end 98, which is fastened by screws 99 to this beak; 100, the insulating coating of the interchangeable end, which can also be made stronger; 101, the thinner coating on the body of said beak 97 for protection against short circuits; with 102 the metal surface on which the largest metal wear is given by the electrolytic cleaning action; with 103 the bore to promote the acidic solution.

In the apparatus for the electrolytic cleaning of metal surfaces, an acidic solution with relatively low proportions of phosphoric acid (52.5 weight percent) and quinoline (0.01 weight percent) in water is used: due to the dilution of this acidic solution as opposed to the high density of those previously used Solution, smaller volumes of solution are required, which are passed directly inside the stocking plug 12 or 54 or the prong 34 of the hollow beak 28, thereby avoiding the dripping of solution onto surrounding surfaces and resulting in relatively few and easily washable surfaces after brushing, which represents a cost advantage.
This solution is then conveyed continuously, so that the plug 12, 34 or 54 is constantly soaked.
The electrolytic action of the acid solution flowing through the stream is always constant, since the operator does not have to interrupt the work to moisten the plug, but only the push button 25, 38 or 47 to supply the solution on the handle 37, 45 must operate ,
The hydraulic circuit shown in Figure 3 works with a pump 16, which can be both designed as a manual pump and can be operated directly by the operator, this direct operation both by means of a In the case of a system operating with air pressure, the tanks 17 or 27 should be made of insulating material which, from the instant at which the acidic solution is introduced, passes through the electrode into the interior of the tank Tension stands, as the acid column in the pipe conducts the tension up to the tank. In this way, the pneumatic-hydraulic circuit shown in Figure 4 also works with a manual pump 22 which pressurizes the tank 23, and the further the solution gets to the beak by opening the valve 25, the more the pressure in the tank drops, whereby a new pressure generation by means of said pump 22 is required. The maintenance of the pressure can be done automatically by a non-pictured pressure switch, which detects the pressure inside the above-mentioned tank.

The tubular sock 12, 54 of insulating fabric is assembled by placing the first end 20, 56 on the beak 11, 52 until it completely envelopes it. The sock has twice the length so that it can be turned over, with the other end 21, 57 coming to lie exactly on the first end. The clamp 13, 58 is placed so that it fixes both ends simultaneously on the body of the beak 11, 48.
Analogous, but easier is the assembly or replacement of the hollow beak 28, which is provided with a stable pre-assembled Isoliermaterialgewebe 34. This beak must be snapped with its frusto-conical end 29 on the frusto-conical portion 27 of the end 26 of the electrode. The replacement is analogous, by the said beak completely removed and another beak is mounted. The hollow beak with frusto-conical snap closure may be formed in various shapes, as in the beaks in the figures 12 and 13 can be seen or with a brush as shown in Figure 14.
The beaked latches close tightly between the pilot hole 60 and the arcuate electrode 46 to prevent leakage of acidic solution so that it is completely directed to the supply bore 59. By the flattened shape 61 shown in Figure 12, the beak can be provided with the flattened over the flattened tubular stocking that a much lower thickness is achieved than the normal beak 48. Finally, allows the sharp and angled design 62 of the beak, depressions and to reach pointed inner corners with limited space, which otherwise can not be easily reached.
In addition, the beaks may be formed instead of a latching connection with a screw connection.
The beak 63 formed with a brush 64 having bristles of insulating material 65 is employed by being moved in the longitudinal or transverse direction to the angle application weld, the bristles stiffened with a top layer of Teflon or other similar material occupying the bottom of the cavity between the wall and reach the weld and clean it completely.

The gun with the slots 36 for evacuating the gases and vapors allows the operator to work completely safely. The extracted air containing the gases and vapors is passed through the wet filter 41, which is designed according to the products used for cleaning metal surfaces by treatment with acid.

In operation, the end 72 does not conduct electrical current, but does so through the heads of the screws 74, which are installed so that they are parallel to the end surface S of that end. The electricity is from these Threaded heads on the soaked in acid solution stocking, whereby the electrolytic cleaning action arises. Also, because the end 72 is non-conductive, it does not heat up due to the electrolytic action that the stocking applies to the surface to be cleaned, and consequently the stocking is not sustainably damaged by burns.
The operation of the electrode with body 78 with a brush of tubes 79 of insulating material is obtained by passing electrical current in the acidic solution from said metal body 78 to the surface of the cavity to be cleaned, also reaching the innermost portions of this cavity.

Tests in which the end of the electrode has been made with glass fiber reinforced teflon have given a substantially longer lifespan of the stocking than with conventional stockings on fully metallic ends, the magnitude of the improvement being about one working shift.

The plug 91 reinforced with double-layer fabric 92,93, whose outer layer of felt 93 is improved, is put on by wrapping the beak end and fixing the plug with a fixing ring 96. On the side flank of the end, the plug does not necessarily have to have a perfect overlap, but the middle part of this plug must cover the active face 102 of the metallic end 98, since it is preferably made as a Teflon film with a thickness of 0.6 - 1.2 mm Insulating coating 100 avoids electrolytic action on the flanks of the end, whereas completely uncoated side 102 is completely exposed to the action. The end can, even if this is less recommended, even with a thin layer of insulating material, such as a Teflon film coated with 0.1 - 0.3 mm thickness, which also protects it from damage and short circuits on the flanks, as is the case for the body of the beak 97 with the coating 101.
Even if various insulating materials can be used for the two layers 92, 93 of the above-mentioned plug, maximum life is achieved for the double-layer plug 91 when polyetheretherketone is used in the inner fabric layer 92 and a polyetheretherketone-based felt is used in the outer layer 93. The double-layered tape can be made by subsequently joining the two layers or by applying one layer to the other directly during manufacture.
The worn plug can be easily replaced by removing the fixing ring 96 and replacing the ribbon at the end of the beak. The ring 96 of insulating material can be used several times.
After the provided with a thick or less thick insulating layer 100 metallic end 98 is worn and the cleaning function can not provide as desired, it is replaced by removing the screws 99.
The highest lifetime values for the metallic beak end are achieved by AISI 316 stainless steel; Although the costs are lower for all other stainless steels, the wear is greater. In the prior art, the technical problem of wear of the electrode was not due to the low power. With these devices, however, only very low efficiencies could be achieved.

Claims (11)

1. Device for cleaning metal surfaces after they have been worked at high temperatures comprising a fabric pad of insulating material placed between the electrode (10) and the metal (8) to be cleaned, a low voltage alternate current power supply (2) applied to the metal (7) with the other electrode (9), an acid solution in which the pad is soaked, the pad consisting of a tubular-shaped sheath (12) or a strip (34, 91) of fabric of insulating material which is more than 1 mm thick, characterised in that the pad is made of an improved electrode-insulating material, that is, a polyetheretherketone fabric, covering the metal tip of the nib of electrode.
2. Device for cleaning metals, as claimed in the previous claim 1, characterised in that the said polyetheretherketone material is in the form of felt.
3. Device for cleaning metals, as claimed in the previous claim 1, characterised in that the said polyetheretherketone material (92) is coated with a felt layer (93) of any heat-resistant insulating material which is either applied afterwards or directly at the time of production.
4. Device for cleaning metals, as claimed in the previous claim, characterised in that the said polyetheretherketone material can also be in the form of a mesh coated with a felt layer made of polyetheretherketone.
5. Device for cleaning metals, as claimed in one of the previous claims 3 or 4, characterised in that the said layer is in the form of felt (93) placed on the outside of the layer of material (92) of polyetheretherketone in relation to the nib (94).
6. Device for cleaning metals, as claimed in claim 1, characterised in that the said nib consists of a metal body (71) and a replaceable tip of insulating material (72), which has inside it at least one metallic element (74) with an extremity near the tip (S) of the nib and which activates electrolytic action.
7. Device for cleaning metals, as claimed in the previous claim 6, characterised in that the said replaceable tip (94, 98) of the nib (97) is made of a metallic material coated with an insulating material (100) on the lateral walls so that there is electric continuity in the area of contact with the body of the nib and on the uninsulated end surface (102); the said end surface has holes (103) through which the acid solution is conveyed.
8. Device for cleaning metals, as claimed in the previous claim 7, characterised in that the said insulating layer (101) consists of a 0.1-0.3 mm-thick layer of Teflon for protection against short circuits.
9. Device for cleaning metals, as claimed in the previous claim 8, characterised in that the said insulating layer (100) consists of a 0.6-1.2 mm-thick layer of Teflon for thermal insulation.
10. Device for cleaning metals, as claimed in one of the previous claims 6 or 7, characterised in that the material of which the nib is made, that is, both the body and the replaceable tip, is a highly resistant stainless steel.
11. Device for cleaning metals, as claimed in the previous claim 10, characterised in that the replaceable tip is made of high strength stainless steel AISI 316.

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