FR2865218A1 - Cylindrical bore coating procedure uses two-wire thermal torch to project atomised metal onto bore surface after lightly threading it - Google Patents

Abstract

The procedure consists of lightly threading the inner surface of the cylindrical bore (4) and then raising the block with the bore on a support (3) so that it is aligned with a two-wire arc torch (7). The block is then moved towards the torch so that their axes of symmetry are in line, and the bore is coated with metal atomised by a gas as an electric arc passes between the two wires and projected onto the bore surface by a second gas passing through a 90-degree nozzle and diffusion cone. An independent claim is given for a device used to implement the outlined procedure.

Description

Fax received from: 0139186708 16/01/04 15:12 Pg: 5

  The present invention relates to a method for coating at least one cylindrical bore by arc-wire thermal spraying. The cylindrical bore 5 to be coated is for example aluminum alloy, and is for example part of a motor unit. The present invention also relates to a device for implementing the method according to the invention.

  It is known in the prior art from EP 0 818 554 a method of coating the inner surface of a cylindrical bore by plasma steel powder projection or arc-wire projection with a steel wire, after preparation. Honing surface, washing with alkaline solution so as to deposit a residue on the surface to prevent oxidation, and rinsing. The honing is done with a diamond-set handle and allows overlapping spiral abrasions to create peaks and valleys. A disadvantage of this method is that it is relatively slow and unsuitable for mass production.

  It is known from US 5,468,295 a device for coating the inner surface of a cylindrical bore by two-wire arcfil thermal spray. The nozzle located at the end of the device consists of a plurality of bent tubes, arranged in a circle and oriented towards the inside of the circle, at an angle slightly greater than 90 °, the outlet of these tubes being situated between 2 and 5 mm after the arc. The throwing gas, sent successively by each of these bent tubes, makes it possible to redirect the flow of particles at a small inclination with respect to the radius of the bore.

  To process several cylindrical bores at the same time, this document teaches mounting several devices on a hydraulic mechanism that allows each device to be lowered into a bore to coat the surface thereof. A disadvantage of this device is that it is complicated. Furthermore, the shape of the nozzle does not allow to deposit the coating perpendicular to the surface, but at an inclination, which is unfavorable to obtain a coating of good cohesion and low porosity.

  Referring now to the present invention, EP 1 238 711 discloses a two-wire arc-wire thermal spray torch whose end of the wire guide is bent just before the arc, at an angle. up to 30, and the deflected projection gas just before the arc, so that the particle flow is projected against the surface of the bore to be coated at an angle between 10 and 45. A disadvantage of this device is that the coating is not deposited perpendicularly to the surface, but in an inclination, which is unfavorable to obtain a coating of good cohesion and low porosity .. In addition, the projection air being guided by an opening of large caliber, it certainly results in a fairly wide diffusion of particles. However, to better control the deposition, it is necessary to better control the trajectory of the particles.

  It is known from WO 97/49497 and WO 91/12183 a two-wire arc-wire thermal spray torch in which projection gas is sent through one or more bent tubes to the particle stream just after the arc.

  The present invention aims to overcome some disadvantages of the prior art by providing a method of coating a cylindrical bore which is fast and which allows to obtain a coating as regular as possible.

  This object is achieved by a method of coating at least one cylindrical bore by thermal arc-wire projection with two metal wires, characterized in that it comprises at least the following successive stages: - realization of a light threading of the cylindrical bore, conveying of the cylindrical bore on a support to a coating station by means of conveying means, - translation of the cylindrical bore to the two-wire arc-wire thermal spray torch in one direction parallel to both the axis of symmetry of the cylindrical bore and the axis of symmetry of the torch, - realization of the coating of the cylindrical bore by the torch, from the inlet of the bore to bottom of the bore during translation rat received a 171371eb (tl i lb / 71 / Cri) lÉÉÉ rÉÉ r from the cylindrical bore to the torch, the free end of the torch being located in the bore, and the material coating being atomized p ar atomizing gas from the electric arc created between the two son, then projected by a throwing gas leaving at least one rotary nozzle towards the inner surface of the bore, said nozzle being constituted by a tube substantially 90 ° bent to project the melted droplets according to a diffusion cone, which is substantially symmetrical with respect to the perpendicular to the inner surface of the cylindrical bore.

  According to another feature, the method according to the invention comprises, before the step of translation of the cylindrical bore to the torch, a step of locking the support of the cylindrical bore in front of the coating station by means of blocking, the blocking being triggered by a sensor at the passage of the support in front of the coating station.

  According to another feature, the method according to the invention comprises, before the step of translation of the cylindrical bore towards the torch, a step of locking the support of the cylindrical bore in front of the coating station by stopping the means of during a given period, this stop being controlled by an automated system.

  According to another feature, the thickness, the roughness and the chemical composition of the coating formed on the inner surface of the bore depend at least on the flow rates of the atomizing and spraying gases, the speed of displacement of the bore by relative to the torch, the rotational speed of the nozzle, the chemical composition of the wires and the nature of the atomizing gas.

  According to another feature, the simultaneous coating of a plurality of cylindrical bores parallel to each other and arranged next to each other is achieved by means of a plurality of parallel projection lamps, arranged next to one another, said torches being controlled by a common mechanical system.

  According to another feature, the threading is inclined or not relative to the plane perpendicular to the cylindrical bore.

  rax received ae 111.i71Ubrots lb / O1 / sort 1, É 1G r y. According to another particular feature, the method according to the invention comprises, after the step of producing the cylindrical bore of the torch, a step of plugging the pores formed by coating a friction agent which penetrates into the pores.

  According to another feature, the method according to the invention comprises, after the step of producing the coating of the cylindrical bore by the torch, a step of machining and / or running in the bore.

  In another feature, the thickness of the coating is substantially between 1.5 and 10 times the thickness of the thread.

  It is another object of the invention to provide a device for coating at least one cylindrical bore by two-wire arc wire thermal spraying, characterized in that it comprises at least one conveying means, resulting in less a support of the cylindrical bore, and a coating station, the conveying means for conveying said support along the device according to the invention at least up to the coating station, and the support consists of at least two trays, the first plate being in contact with the conveying means and the second plate being mounted movable in translation relative to the first plate, on the latter.

  According to another feature, the second plate is connected to the first plate by at least one telescopic arm controlled by a servo system, making it possible to translate the second plate relative to the first plate in a direction parallel to the axis of symmetry of the bore.

  According to another feature, each telescopic arm is an electric jack associated with a guide rail.

  According to another feature, the conveying means consists of a plurality of rollers arranged parallel to each other, each rotating about its axis and each being provided with drive means.

  According to another feature, the conveying means consists of a belt driven by drive rollers.

S

  According to another feature, the coating station comprises a frame on which is mounted a means for holding at least one arc-wire projection torch with two metal wires, each torch comprising a rod of outside diameter smaller than the inside diameter of the wire. cylindrical bore and at least equal in length to that of the bore, said rod having two wire guide each guiding one of the metal son from a winding to the free end of the cane, each son being connected to a electrode so as to create an electric arc causing the free ends of the wires to be melted in the form of droplets, said droplets being atomized by atomizing gas from the electric arc towards the outside of the cane and then thrown by a gas projecting from at least one rotating nozzle towards the inner surface of the bore.

  According to another particularity, the coating station comprises a plurality of projection torches parallel to each other and arranged next to each other, said torches being controlled by a common mechanical system so as to effect the simultaneous coating of a plurality of cylindrical bores parallel to each other, arranged next to one another.

  According to another feature, each nozzle is in the form of a bent tube 20 substantially 90, turned towards the inside of the torch and the nozzle rotates about the axis of symmetry of the torch.

  According to another feature, the coating station comprises two identical nozzles located in two pans perpendicular to each other and intersecting substantially on the axis of symmetry of the torch.

  According to another particularity, the coating station comprises at least one motor equipped with toothed wheels for unwinding the son of the windings on a regular basis.

  According to another feature, a second means for unwinding the wire is integrated in the cane.

  According to another particularity, the atomizing gas is air, nitrogen or another gas, chosen according to the physicochemical properties of the coating to be obtained.

  received ae: n1.371ebrou 10/01 / Ot 1D. 1G r9. In another feature, the wires are made of steel containing at least 80% iron.

  Other features and advantages of the present invention will emerge more clearly on reading the following description, with reference to the accompanying drawings, in which: - Figure 1 shows a side view of the coating device according to a FIG. 2 shows a perspective view of a first embodiment of the torch of the coating device according to the invention; FIG. 3 represents a perspective view of a second embodiment of FIG. embodiment of the torch of the coating device according to the invention, - Figure 4 shows a longitudinal sectional view of the front portion of the torch of the coating device according to the first embodiment of the invention, inserted into the cylindrical bore - Figure 5 shows a detail sectional view of the surface of the cylindrical bore after threading.

  The coating device according to the invention, shown in particular in Figure 1, comprises at least one conveying means (1), driving at least one support (3) of cylindrical bore (4), and a coating station (2). The conveying means (1) consists for example of a plurality of rollers (10) arranged parallel to each other, each rotating about its axis and each being provided with drive means (11). In an alternative embodiment, the conveying means (1) consists of a belt driven by drive rollers. The conveying means (1) makes it possible to convey at least one cylindrical bore support (3) along the device according to the invention at least to the coating station (2).

  Each support (3) consists of at least two plates (30, 31), the first plate (30) being in contact with the conveying means (1) 30 during the entire coating process according to the invention and the second plate (31) being mounted movable in translation relative to the first plate (30) on the latter. The cylindrical boring (s) (4) are fixed in a manner Fax received from: 8139186708 16/01/04 15:12 Py: 11 removable on the second plate (31) at least during the production of the coating according to the invention. The cylindrical bores (4) are for example, but not limited to, part of a motor unit, as shown in Figure 1.

  Each support (3) must remain stopped in front of the coating station (2) for a determined period of time to achieve the coating. To do this, in a first variant, the device comprises locking means (5) of the support (3) while the transport station (1) continues to scroll, each support (3) being simply in contact with the io means of routing, but not fixed on it. These locking means (5) are located transversely to the running direction of the transport station (1) at the coating station (2). The locking means (5) are, for example, tongues which, when the support (3) passes in front of the coating station (2), fit into cavities of complementary shape formed in the first plate (30) of the support (3). ) to block. This insertion is for example triggered by a sensor (not shown) detecting the passage of the support (3) in front of the coating station (2). In this first variant, it is necessary that two successive supports are arranged at a minimum distance determined from each other to avoid collisions between moving media and supports blocked by the locking means (5). In a second variant, the routing means (1) is controlled by an automated system (not shown) provided with at least one processor programmed to stop the routing means (1) during said determined duration, allowing zs to achieve the coating, after a second determined duration, corresponding to the time required for another support comes to replace the one supporting the bore just coated. This second variant requires that all the supports (3) are arranged at a determined constant distance from each other. It is therefore necessary to fix them 3o to the routing means (1).

  The coating station (2) comprises a frame on which is mounted a means (6) for holding at least one two-wire arc-wire projection torch (7). The holding means (6) can hold as many torches arranged parallel to each other as cylindrical bores parallel to each other that comprises a part. For example, for coating an engine block comprising four cylindrical bores in series or eight cylindrical bores distributed in two series of four cylindrical bores parallel to each other, the holding means (6) can maintain four torches spaced from each other the same distance that separating the cylindrical bores parallel to each other of the engine block. The different torches arranged next to each other are in this case controlled by a common mechanical system so that the coatings of all the cylindrical bores of the part are made simultaneously.

  Each torch (7), visible in particular in Figures 2 and 4 comprises a cane (70), one end of which is inserted into the cylindrical bore (4) to effect the coating. The other end of the rod (70) of the torch (7) is fixed to the holding means (6). The cane (70) of the torch (7) is cylindrical, of outside diameter less than the inside diameter of the bore, so as not to hinder the penetration of the cane (70) into the latter, and of length at least equal to to that of the bore, to be able to coat the entire inner surface (40) of the bore. The cane (70) of the torch (7) comprises two wire guides (71) each guiding a wire (72) from a coil, located in the holding means (6), to the free end of the cane (70). Each of the wires is connected to an electrode (not shown), so that one of the wires is at a positive potential and the other wire is at a negative potential. The two wires are preferably arranged symmetrically to one another with respect to the axis of the cane (70), as shown in FIG. 4. The free ends of the two wires (72) must be sufficiently close to each other. one of the other to create an electric arc causing the melting of the free ends of the son (72) in the form of droplets. A channel (73) conveying an atomizing gas along the cane (70) from a distribution site of this atomizing gas (not shown) to the free end of the cane (70) is located substantially along the axis of symmetry of the cane (70). This atomizing gas makes it possible to project the received Faxes of: 0139186708 16/01/04 15:12 Py: 13 droplets melted from the electric arc towards the outside of the cane according to a first scattering cone (74) of the droplets , this first diffusion cone (74) being substantially symmetrical with respect to the axis of symmetry of the cane (70). In order to maintain the production of droplets, the son (72) are regularly unwound windings through a motor (not shown) equipped with toothed wheels, this motor being located in the holding means (6). A second means for unwinding the wire can be integrated with the torch if the wires are relatively distant from the windings. This second means is for example a second toothed wheel motor or a pull-pushed system.

  The atomizing gas is, for example, air, nitrogen or another gas. It is chosen according to the chemical reactions that it is desired to obtain between the atomizing gas and the material constituting the yarns (72) to have a coating with the desired physicochemical properties.

  In the case of cylindrical bores (4) of the engine block, the bores are made of aluminum alloy. To improve the mechanical properties of the bores for use in a vehicle, the latter are coated by the method according to the invention. For this, the son are preferably steel containing at least 80% iron.

  To obtain the most regular coating possible, it is necessary to project the melted droplets as perpendicularly as possible to the inner surface (40) of the cylindrical bore to be coated. For this, each torch (7) comprises a rotary portion (75) of ring-shaped section disposed near the edge of the rod (70). This rotating part (75) comprises a channel (76) leading a throwing gas (preferably air) along the cane (70), from a distribution site of this throwing gas (not shown) until at the free end of the cane (70). The channel (76) of the throwing gas is extended outside the rod (70) by a nozzle (77), in the form of a tube bent substantially 90e, turned towards 3o the inside of the torch (7). At the outlet of the nozzle (77), the projection gas is diffused along a second diffusion cone (78), which is substantially symmetrical with respect to the perpendicular to the inner surface (40) of E clA zc YU RC El 1.37 100 C 00 1D / Cl the UY 1D É iG ay É .iz 2865218 io the cylindrical bore (4) to be coated. The outlet of the nozzle (77) is located downstream of the electric arc, preferably 1 cm later, so that the first and second diffusion cones (74, 78) interfere with each other. The interference between the first and second diffusion cones (74, 78) allows, thanks to adapted flow rates of the atomization and projection gases, to project the melted droplets in a third diffusion cone (79), which is substantially symmetrical with respect to the perpendicular to the inner surface (40) of the cylindrical bore (4) to be coated.

  In an alternative embodiment, shown in FIG. 3, the torch (7) comprises two nozzles (77), each located in the extension of a channel (76) containing the throwing gas and turned towards the inside of the torch (7), in order that the droplets are diffused as perpendicularly as possible to the inner surface (40) of the bore (4), the two nozzles (77) are situated in two mutually perpendicular planes which intersect substantially on the axis of symmetry fa cane (70) of the torch (7).

  In the torch (7) of the device according to the invention, the rotating part (75) rotates about the axis of symmetry of the rod (70) at a constant speed, together with a relative translational movement of the cylindrical bore (4) relative to the rod (70) occurs, covering the entire inner surface (40) of the cylindrical bore (4) of the material constituting the melted droplets.

  The relative translational movement of the cylindrical bore (4) relative to the rod (70) can occur in two ways: either the torch (7) moves to the bore, or the bore moves to the torch (7). In the device according to the invention, this relative translation movement is preferably a displacement of the bore towards the torch (7). To do this, the second plate (31) of the support (3) of the device slides relative to the first plate (30) in a direction parallel to the axis of the cylindrical bore (4) and to the axis of the torch (7), as shown in Figure 1.

  This is achieved for example by at least one telescopic arm (32) connecting the second plate (31) to the first plate (30). Each arm is c-QC. 0137100 (00 lbf tJlf 7g 15 É 1G ry>> telescopic is for example an electric jack associated with a guide rail The support (3) comprises a servo system of the second plate (31) to control its rise up to the torch (7), for the coating to be carried out in the cylindrical bore, and then down to the first tray (30) once the coating has been completed, and the rising speed of the second tray (31) can be relatively fast until the open end of the bore reaches the free end of the torch (7), at this time triggered for example by means of a sensor system detecting the position of the boring (4) with respect to the torch (7), the torch (7) ro is started, the rise speed of the second plate (31) is then determined according to parameters such as the flow rates of the atomizing gases. and projection, so as to obtain the desired coating.

  In order for the coating to adhere better to the inner surface (40) of the cylindrical bore (4), a slight threading is made just after the machining of the bore, before coating of its inner surface (40). After this threading, the internal surface (40) of the cylindrical bore (4) is for example as shown in Figure 5, sawtooth. The thickness of the thread is, for example, 300 μm.

  The thickness of the coating to be produced is for example between 1, 5 and 10 times the thickness of the thread, preferably 2 times, namely 600 pm if the thread has a thickness of 300 pm.

  The threading made may be inclined or not relative to the plane perpendicular to the cylindrical bore.

  In an alternative embodiment, a sandblasting is performed in place of the thread.

  The user of the coating method according to the invention can control the thickness, the roughness, the chemical composition, etc., of the final coating by correctly selecting the coating parameters, namely the flow rates of the atomization and projection gases. , the relative speed of displacement of the bore relative to the torch, the rotational speed of the rotational part of the torch, the chemical composition of the metal wires, the nature of the atomizing gas, etc.

  Pax received from: 1113 1Ub-rbii 1b /! 71 / F74 15.16 ry. If the coating is relatively rough, the inner surface (40) of the cylindrical bore (4) is either re-machined or coated with a friction agent, for example known under the trade name "regul", for to clog the pores formed during the coating by penetrating the pores, or both.

  After completion of the coating, the inner surface of the bore may be lapped.

  It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration, but may be modified in the field defined by the scope of the appended claims, and the invention should not be limited to the details given above.

  Fax received from: M13'31UbY08 16/01/04 15:12 P9: 17

Claims (22)

REYENDICATIONS   1. Method for coating at least one cylindrical bore (4) by thermal arc-wire projection with two metal wires (72), characterized in that it comprises at least the following successive stages: - realization of a light threading the cylindrical bore (4), - conveying the cylindrical bore (4) on a support (3) to a coating station (2) by means of a conveying means (1), - translation of the cylindrical bore (4) to the two wire arc-wire thermal spray torch (7) (72) in a direction parallel to both the axis of symmetry of the cylindrical bore (4) and the axis of symmetry of the torch (7), - realization of the coating of the cylindrical bore (4) by the torch (7), from the inlet of the bore to the bottom of the bore during the translation of the cylindrical bore (4) to the torch (7), the free end of the torch (7) being located in the bore, and the coating material being atomised by an atomizing gas from the electric arc created between the two wires (72), then projected by a throwing gas leaving at least one rotary nozzle (77) towards the inner surface (40) of the bore ( 4), said nozzle (77) consisting of a substantially 90-degree bent tube for projecting the molten droplets into a diffusion cone (79), which is substantially symmetrical with respect to the perpendicular to the inner surface (40) of the cylindrical bore (4), 2. Method according to claim 1, characterized in that it comprises, before the step of translation of the cylindrical bore (4) to the torch (7), a step of locking the support (3) of the bore cylindrical (4) in front of the coating station (2) by means of locking means (5), the locking being triggered by a sensor at the passage of the support (3) in front of the coating station (2).   3. Method according to claim 1, characterized in that it comprises, 30o before the step of translation of the cylindrical bore (4) to the torch (7), a rat received ae. 1b / U1 / b4 lb: 1Z 'g: the step of blocking the support (3) of the cylindrical bore (4) in front of the coating station (2) by stopping the conveying means (1) during a fixed period, this stop being controlled by an automated system.   4. Method according to one of claims 1 to 3, characterized in that the thickness, the roughness and the chemical composition of the coating made on the inner surface (40) of the bore (4) depend at least on the flow rates of the gases. atomization and projection, the speed of displacement of the bore (4) with respect to the torch (7), the speed of rotation of the nozzle (77), the chemical composition of the wires (72) and the nature of the atomizing gas.   io 5. Method according to one of claims 1 to 4, characterized in that the simultaneous coating of a plurality of cylindrical bores (4) parallel to each other and arranged next to each other is achieved through a plurality of torches (7). ) projecting parallel to each other, arranged next to each other, said torches being controlled by a common mechanical system.   6. Method according to one of claims 1 to 5, characterized in that the thread is inclined or not with respect to the plane perpendicular to the cylindrical bore.   7. Method according to one of claims 1 to 6, characterized in that it comprises, after the step of producing the coating of the cylindrical bore (4) by the torch (7), a step of capping the pores formed by coating of a friction agent that penetrates the pores.   8. Method according to one of claims 1 to 6, characterized in that it comprises, after the step of producing the coating of the cylindrical bore (4) by the torch (7), a machining step and / or break-in the bore.   9. Method according to one of claims 1 to 8, characterized in that the thickness of the coating is substantially between 1.5 and 10 times the thickness of the thread.   10. Apparatus for coating at least one cylindrical bore (4) by two-wire arc-wire thermal projection (72), characterized in that it is received from: 0139116 (0016/01 / e4 15: 1Z Py: 19 comprises at least one conveying means (1), driving at least one support (3) of the cylindrical bore (4), and a coating station (2), the conveying means (1) for conveying said support (3) along the device according to the invention at least to the coating station (2), and s in that the support (3) consists of at least two plates (30, 31), the first plate (30) being in contact with the conveying means (1) and the second plate (31) being mounted in translation relative to the first plate (30) on the latter.   11. Device according to claim 10, characterized in that the second plate (31) is connected to the first plate by at least one telescopic arm (32) controlled by a servo system, for translating the second plate (31). relative to the first plate (30) in a direction parallel to the axis of symmetry of the bore (4).   12. Device according to claim 11, characterized in that each telescopic arm (32) is an electric jack associated with a guide rail   13. Device according to one of claims 10 to 12, characterized in that the conveying means (1) consists of a plurality of rollers (10) arranged parallel to each other, each rotating about its axis and each being provided with drive means (11).   14. Device according to one of claims 10 to 12, characterized in that the conveying means (1) consists of a belt driven by drive rollers.   15. Device according to one of claims 10 to 14, characterized in that the coating station (2) comprises a frame on which is mounted a means (6) for holding at least one torch (7) projection arc-wire with two wires (72), each torch (7) comprising a cane (70) of outside diameter smaller than the inside diameter of the cylindrical bore (4) and of length at least equal to that of the bore, said blade ( 70) having two wire guides (71) each guiding one of the wires (72) 30 from a winding to the free end of the cane (70), each of the fax wires received from: 0139186708 16/01/04 15:12 Py: 20 being connected to an electrode so as to create an electric arc causing the free ends of the wires (72) to melt in the form of droplets, said droplets being atomized by an atomizing gas from the electric arc towards the outside of the cane, then projected by a projection gas out of at least s a rotating nozzle (77) to the inner surface (40) of the bore (4).   16. Device according to claim 15, characterized in that the coating station (2) comprises a plurality of projection torches (7) parallel to each other and arranged next to one another, said torches being controlled by a mechanical system. common so as to achieve the simultaneous coating of a plurality of cylindrical bores (4) parallel to each other, arranged next to each other.   17. Device according to claim 15 or 16, characterized in that each nozzle (77) is in the form of a tube bent at substantially 90, turned is towards the inside of the torch (7) and in that the nozzle (77) rotates around the axis of symmetry of the torch (7).   18. Device according to one of claims 15 to 17, characterized in that the coating station comprises two identical nozzles (77) located in two planes perpendicular to each other and intersecting substantially on the axis of symmetry of the torch (7).   19. Device according to one of claims 15 to 18, characterized in that the coating station comprises at least one motor equipped with toothed wheels for unwinding the son (72) of the coils regularly.   20. Device according to claim 19, characterized in that a second means for unwinding the wire is integrated in the cane (70).   21. Device according to one of claims 15 to 20, characterized in that the atomizing gas is air, nitrogen or another gas, selected according to the physicochemical properties of the coating to be obtained.   r ax RECEIVED 1.17 LUC> f 22. Device according to one of claims 15 to 21, characterized in that the fries (72) are steel containing at least 80% iron.