Lubrication of a glassmaking mold by cold spraying of a metallic powder

Abstract

This description relates to a method for lubricating a molding surface (2) of a glass mold (1). This method comprises a step of cold spraying a solid metal powder (4) onto the molding surface (2) of the glass mold (1) to obtain a solid deposit (5). It also comprises a step of machining (120) the solid deposit (5) to obtain a lubricating coating (6). This description also relates to a metal powder, a surface treatment machine, and a surface treatment installation for implementing such a method, as well as a glass mold obtained by such a method. Figure for the abstract: Fig. 1

Description

Title of the invention: Lubrication of a glass mold by cold spraying of a metallic powder technical field

[0001] This application relates generally to foundry parts in the field of glassmaking, in particular cast iron, brass, bronze (and other alloys including copper and tin) or steel molds used to make glass objects such as bottles.

[0002] The present application relates more particularly to the lubrication of the metal molding surface of these molds which comes into contact with the parison during the manufacture of glass objects during the roughing phase in order to improve the loading and unloading of the molds. STATE OF THE ART

[0003] The manufacture of a glass object, in particular a hollow glass object such as a bottle, is done in several stages.

[0004] In a first step called the roughing stage, viscous glass is melted (at a temperature between 700 °C and 1200 °C) and poured in the form of a parison (drop) into a mold, called a roughing mold. The viscous glass is compressed in the roughing mold and then pierced to bring it into contact with the walls of the roughing mold and obtain a rough shape. The rough shape then has a temperature that can reach 900 °C, depending on the area and thickness of the rough shape.

[0005] Then, during a second step known as the blowing stage, the blank thus formed is transferred into a finishing mold to be blown and give it its final shape. Upon contact between the blank and the finishing mold, a significant decrease in temperature occurs, as well as an elongation of the glass. The final product is obtained after this blowing stage. It then has a temperature of approximately 600°C.

[0006] During the roughing stage, several loading defects can appear (bone- or banana-shaped parison, parison misalignment, etc.). In the case of a bottle-type object, if these defects are minimal, only a few creases appear on the body of the bottle and / or at the shoulder. However, if the misalignment is too significant, the parison cannot penetrate to the bottom of the roughing mold. The pressure against the walls of the roughing mold will therefore be impaired, which can lead to the formation of defects at the neck of the bottle, and thus the rejection of the bottle.

[0007] It has therefore been proposed to lubricate the molding surface of the roughing molds, that is to say the surface which comes into contact with the parison, by regularly depositing a lubricant on this surface. The lubricant generally includes a graphite-loaded grease to allow the parison to penetrate the roughing mold and facilitate the removal of the roughing.

[0008] However, this lubrication operation must be repeated very regularly to be effective, typically every twenty minutes, which reduces the productivity of the molding process. Furthermore, it is generally performed manually by the operators: however, the temperature around the blank mold is very high, creating a difficult working environment for the operators, as the blank molds themselves are at a temperature of around 500°C. In addition, fouling of the mold and the production machine can occur due to the presence of carbon residues from the use of graphite grease. Because of the successive opening and closing of the mold to allow lubrication, the mold temperature is also heterogeneous, which destabilizes the molding process.Finally, as the lubrication of the molds is not controlled (and is therefore not homogeneous over the entire molding surface of the roughing mold), localized wear due to abrasion can occur, and the lubricant can decompose under the effect of high temperatures.

[0009] It has also been proposed to replace lubrication with a semi-complete combustion of acetylenes. However, this combustion requires a constant presence of fuel-based propellant gas on site, which is costly. EXPOSED

[0010] One purpose of the present application is to remedy the aforementioned inconveniences.

[0011] To this end, the invention relates, according to a first aspect, to a method for lubricating a molding surface of a glass mold comprising the following steps: - cold projection of a solid metallic powder onto the molding surface of the glass mold to obtain a solid deposit; and - machining of the solid deposit to obtain a lubricating coating.

[0012] According to particular embodiments of the invention, the lubrication process also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the metal powder is projected using a projection gas subjected to a pressure greater than thirty bars, for example between forty bars and seventy bars, for example about fifty bars; - the metal powder is projected using a projection gas heated to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C; - during the projection stage, a projection distance, corresponding to the distance between a metal powder projection nozzle and the surface of molding, is between 15 millimeters and 30 millimeters, preferably equal to about 20 millimeters; - during the projection stage, a speed of movement of a projection nozzle of the metal powder during projection is between 500 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example equal to about 800 millimeters per second (mm / s); - the projection step is carried out for a sufficient duration to obtain a solid deposit with a thickness between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter; and - an injection rate of the metal powder into the projection gas is between 5.936 and 17.808 cmVmin, preferably between 8.904 and 14.840 cmVmin, for example in the order of 11.872 cmVmin.

[0013] The invention also relates, according to a second aspect, to a metallic powder for the lubrication of a glass mold in accordance with a lubrication process according to the first aspect.

[0014] According to particular embodiments of the invention, the metal powder has one or more of the following characteristics, taken individually or in any technically possible combination(s): - said metal powder comprises and is advantageously essentially composed of, by mass relative to the total mass of the powder: • between 90 and 97%, for example 95%, of NiCr powder, and • between 3 and 10%, for example 5%, of titanium dioxide powder,

[0015] the nickel content in the NiCr powder being between 40 and 50% by mass and the chromium content being between 50% and 60% by mass, relative to the total mass of the NiCr powder; - the particle size of NiCr powder is between 10 and 40 micrometers and the particle size of titanium dioxide powder is between 5 and 40 micrometers; - said metallic powder comprises and is advantageously essentially composed of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminium; • between 5 and 15%, preferably between 8 and 12%, of zinc; and - the particle size of the metal powder is greater than or equal to 15 microns and less than or equal to 45 microns.

[0016] The invention also relates, according to a third aspect, to a glass mold comprising: - a molding surface; and - a lubricating coating covering all or part of the molding surface and comprising a metallic alloy obtained by cold spraying a metallic powder onto the molding surface in accordance with a lubrication process according to the first aspect.

[0017] According to particular embodiments of the invention, the glass mold also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the metal powder is mainly composed of nickel, chromium and titanium dioxide; - the molding surface comprises at least one of the following materials: graphite cast iron with a lamellar, vermicular or spheroidal micrographitic structure, a copper and tin-based alloy such as bronze, iron-carbon steel, refractory steel or stainless steel, brass; - the lubricating coating is obtained by cold spraying of a metallic powder according to the second aspect.

[0018] Finally, the invention relates, according to a fourth and a fifth aspect, to a machine for lubricating a glass mold, comprising a support configured to receive a glass mold having a molding surface and a projection nozzle configured to cold project a solid metallic powder onto the molding surface so as to obtain a solid deposit, and an installation comprising a lubrication machine according to the fourth aspect and a machining station configured to machine the solid deposit and obtain a lubricating coating. DESCRIPTION OF THE FIGURES

[0019] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which: Fig. 1 schematically illustrates an example of an installation for the lubrication of a glass mold according to an embodiment;

[0020] Fig. 2 is a flowchart illustrating steps of a process for lubricating a glass mold according to an embodiment; Fig. 3 is a schematic cross-sectional view of a glass mold comprising a lubricating coating according to an embodiment; Fig. 4 is a schematic view representing a drop of parison on the free surface of a typical glass mold substrate;

[0021] Fig. 5 is a curve illustrating the viscosity of the glass composing the parison droplet of Fig. 4 as a function of temperature.

[0022] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0023] With reference to [Fig. 1], this application relates to the lubrication of all or part of the molding surface 2 of a glass mold 1. The glass mold 1 may, in particular, include a blank mold 1 configured to receive a drop of glass (parison) and form a blank. The molding surface 2 corresponds to the surface of the mold 1 that is likely to come into contact with the parison during the molding process. The molding surface 2 may, in particular, comprise at least one of the following materials: graphite cast iron with a lamellar, vermicular, or spheroidal micrographitic structure; bronze (and other alloys including copper and tin); iron-carbon steel, refractory steel, or stainless steel; or brass. Preferably, the glass mold 1 is formed entirely from the same constituent material as the molding surface 2.

[0024] In order to lubricate the molding surface 2 of a glass mold 1, it is proposed to project, cold and at a very high speed, by a projection gas 3 under high pressure transporting it, a metallic powder 4 onto all or part of the molding surface 2.

[0025] Cold spraying, also known as high-pressure cold spray, allows for a deposition density very close to the theoretical density of the solid metallic material constituting the powder, without heating the molding surface 2 during deposition. This avoids altering the metallurgical quality of the molding surface 2 and the solid deposit 5. Furthermore, it allows for thick deposits (up to several millimeters) with low roughness and a material yield of over 90%, as well as high interparticle cohesion. In addition, this cold spraying process does not require any prior preparation of the molding surface 2 or masking of the mold 1 to be treated. LUBRICATION SYSTEM 9

[0026] An installation 9 for lubricating all or part of the molding surface 2 of a glass mold 1 is shown in [Fig. 1]. This installation 9 comprises a lubrication machine 10 and a machining station 11.

[0027] The lubrication machine 10 is configured to cold-spray the metal powder 4, in solid form, onto the molding surface 2 of the mold 1. For this purpose, it includes a spray nozzle 7, preferably made of ceramic, comprising: - a heating and pressurization system for a projection gas 3, typically nitrogen or helium, in a pressurization chamber 12; - a powder dispenser 13 to supply the metal powder 4; - an injection system 18 for injecting the metal powder 4 into the gas projection 3 downstream of the pressurization chamber 12 so that it is not heated by the lubrication machine 10 and therefore remains in a solid state; - a transport system 19 for transporting the metal powder 4 from the powder dispenser 13 to the injection system 18 by means of a carrier gas (typically identical to the projection gas 3); - a convergent-divergent nozzle 8 placed downstream of the injection system 18 and configured to accelerate the blasting gas 3 when it carries the metal powder 4, the divergent part of the nozzle 8 forming a deposition tube 14; and - a cooling system 15 which may include a conduit which surrounds the deposition tube 14 in order to cool the blasting gas 3, which carries the metal powder 4, by conduction by circulating a cooling fluid around the deposition tube 14; the cooling fluid may in particular include distilled water at a temperature lower than the temperature of the blasting gas 3, typically at a temperature between 8 and 20°C.

[0028] The lubrication machine 10 further includes a support 17 configured to fix the glass mold 1 relative to the spray nozzle and actuators configured to move the spray nozzle 7 relative to the molding surface 2 in the three spatial directions. These actuators can move the spray nozzle 7, the support 17 on which the mold 1 is mounted, or both the spray nozzle 7 and the support 17. The actuators are configured to move the nozzle relative to the molding surface 2 at a speed between 600 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example, on the order of 800 millimeters per second (mm / s) (to within 5%). The actuators are further configured to offset the impact zone by a distance of between 0.5 millimeters and two millimeters (no projection between two adjacent cords), for example on the order of one millimeter (to within 10%).

[0029] The heating system is configured to heat the projection gas 3 to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C. The projection gas 3 is also pressurized in the pressurization chamber to a pressure greater than or equal to thirty-five bar, preferably between forty bar and seventy bar, for example in the order of fifty bar.

[0030] The spray nozzle 7 can be controlled by a remote control station 16, located near the lubrication machine 10 or at a distance.

[0031] The machining station 11 includes a support configured to receive the mold 1 coated with the solid deposit 5 and a machining tool, such as a milling machine, configured to machine the solid deposit 5 and obtain the lubricating coating 6. The machining tool can be operated by an operator or mounted on the installation 8 and controlled by a station. Remote control, for example the same control station 16 of the projection nozzle 7. LUBRICATION PROCESS 100

[0032] A method 100 for lubricating the molding surface 2, implemented by the lubrication installation 9, is shown in [Fig. 2]. It comprises the following steps: - cold projection 110 of a solid metallic powder 4 onto the molding surface 2 of the glass mold 1 so as to obtain a solid deposit 5; and - machining 120 of the solid deposit 5 so as to obtain a lubricating coating 6 ([Fig.3]).

[0033] The process 100 can be applied to the entire molding surface 2 of the mold 1 or to only a part of this surface 2.

[0034] During the projection step 110, a high-temperature (typically nitrogen or helium) and high-pressure projection gas 3 is used to propel the metal powder 4 at supersonic speed (greater than 300 m / s) onto the molding surface 2 to create a solid deposit 5 intended to form the lubricating coating 6 by impact of the metal powder 4 on the molding surface 2, the impact force ensuring the quality of the deposit. In the present application, the deposit is referred to as "solid" insofar as the grains of the metal powder 4 remain in a solid state throughout the projection and adhesion step 110 to the molding surface 2, as opposed to processes in which the temperature of the metal powder 4 exceeds its melting point so that all or part of the powder 4 melts at some point during the process 100.When the metal powder 4 comes into contact at high speed with the molding surface 2, it mechanically adheres to the molding surface 2 through plastic deformation with strong adhesion, thus preventing high-temperature defects such as oxidation, residual stresses, phase transformations, etc. The solid deposit 5 is then bonded to the molding surface 2; that is, it can only be separated from the molding surface 2 by being wholly or partially damaged.

[0035] The projection step 110 is said to be cold insofar as the metal powder 4 is not heated before or during deposition, other than by its contact with the projection gas 3 or the molding surface 2.

[0036] During the projection step 110, the projection gas 3 is heated and pressurized to ensure that the metal powder 4 is projected at a projection velocity (velocity of the metal powder 4 exiting the nozzle 7) sufficient to allow the metal powder 4 to undergo plastic deformation upon impact with the contact surface. It should be noted that the gas is heated and pressurized before the solid powder is injected into the gas and projected onto the molding surface 2 to ensure that the metal powder 4 remains in a solid state. To this end, said projection velocity is greater than or equal to the critical velocity of the metal powder 4. This velocity The critical velocity corresponds to the speed at which the adhesion of the solid deposit 5 is possible: when the impact velocity is lower than the critical velocity of the material, the metal powder particles 4 do not deform plastically and can rebound and / or erode the molding surface 2. The critical velocity depends on the nature of the material and the grain size of the metal powder 4. For example, the critical velocity is higher for a metal powder 4 containing a hard material, such as a titanium dioxide-based material (above 1250 m / s), than for a metal powder 4 containing a ductile material, such as a copper-based material (around 600 m / s). An equation ε₀ for determining the critical velocity of a material was developed by T. Schmidt, F. Gartner, H. Assadi, and H. Kreye, "Development of a generalized parameter window for cold spray deposition," Acta Mater.54 (2006) 729-742; . https: / / doi.org / 10.1016 / j.actamat.2005.10.005): where: or is the breaking strength of the material; p is the density of the material to be characterized; T; is the initial temperature of the material to be characterized; Tm is the melting temperature of the material to be characterized; cp is the specific heat; Tr is a reference temperature equal to 293 K; and Fi and F2 are calibration coefficients used to recalibrate the calculated value on measured speed values.

[0037] The pressure applied to the projection gas 3 is therefore chosen so as to exceed the critical velocity of the metal powder 4 used for the solid deposition 5. A pressure greater than or equal to thirty-five bars, preferably greater than or equal to forty bars, for example equal to fifty bars, is suitable for most metal powders that can be used in the lubrication of a glass mold 1.

[0038] Furthermore, the temperature to which the projection gas 3 is heated is typically greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C. This heating temperature is advantageously at least 300°C below the melting temperature of the constituent of the metal powder 4 with the lowest melting temperature and for example between 300 and 700°C below this melting temperature.

[0039] Where appropriate, the projection gas 3 can further be accelerated by the configuration of the projection nozzle 7 (modification of the gas passage cross-section, for example in a convergent-divergent nozzle 8, etc.).

[0040] For a nickel-chromium-based powder as described below, the critical velocity is, for example, on the order of 574 m / s.

[0041] If necessary, the projection gas 3 can be cooled downstream of the point of injection of the metal powder 4 into the gas in order to ensure that the metal powder 4 remains solid without reducing the projection velocity of the powder.

[0042] The projection step 110 is carried out so as to obtain a solid deposit 5 of sufficient thickness to allow machining of the solid deposit 5 and the application of the lubricating coating 6. This thickness of the solid deposit 5 is typically between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter. The thickness of the coating 6 (after machining) can thus be between 0.1 millimeters and 1.5 millimeters.

[0043] For this purpose, the molding surface 2 is moved relative to the lubrication machine 10 during the spraying step 110 in order to deposit the material onto all or part of the molding surface 2. The spray nozzle 7 can be moved while the glass mold 1 is stationary, or alternatively the glass mold 1 can be moved while the spray nozzle 7 is stationary, or both the spray nozzle 7 and the glass mold 1 are moved. The relative speed of movement and the number of passes over a given surface determine the thickness of the deposit. For example, the relative speed of movement of the projection nozzle 7 and the molding surface 2 of the glass mold 1 can be between 600 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example on the order of 800 millimeters per second (mm / s) (to within 5%).

[0044] The supply rate of the metal powder 4 by the distributor 13 is between 5,936 and 17,808 cmVmin, preferably between 8,904 and 14,840 cmVmin, for example on the order of 11,872 cmVmin. The metal powder 4 thus supplied is entirely transported by the carrier gas to the injection system 18, so that this supply rate also constitutes an injection rate of the metal powder 4 into the projection gas 3 by the injection system 18. For this purpose, the carrier gas flow rate is typically between 3 and 6 cubic meters per hour (m³ / h), for example on the order of 4.5 cubic meters per hour (m³ / h).

[0045] The size (bead width) of the solid deposit 5 is preferably between 0.5 millimeters and two millimeters, for example on the order of one millimeter (to within 10%). This size depends on the distance between the outlet of the spray nozzle 7 of the lubrication machine 10 and the molding surface 2 and on the outlet diameter of the spray nozzle 7. In order to obtain the aforementioned solid deposit size, said distance is typically between fifteen millimeters and sixty millimeters, for example on the order of twenty millimeters (to within 10%), for an outlet diameter of the spray nozzle 7 between two and ten millimeters, for example on the order of six millimeters.

[0046] The projection pitch (distance between the centers of two solid deposition beads 5 adjacent) is between 0.5 millimeters and two millimeters, for example on the order of one millimeter (to within 10%). It is preferably approximately equal to the size of the solid deposit 5.

[0047] After machining, the porosity of the coating 6 can be between 0.2% and 15%, knowing that the lower the porosity of the coating 6, the closer the behavior (in terms of parison sliding) of the lubricating coating 6 is to the behavior of a graphite grease. This porosity is a function of the parameters of projection used during step 110. It is evaluated as follows: - a color image of coating 6 is obtained with a Leica DMi8 C optical microscope using a magnification x5 and the automatic exposure parameters of the microscope; - This image is then binarized using ImageJ software (version 1.53f51), this binarization comprising the following steps: converting the image to 8-bit greyscale using the software's dedicated function, then black and white conversion using the software's automatic thresholding function (Yen method) (thresholding function defining the gray intensity establishing the threshold between pixels converted to white and those converted to black); Finally, the surface fraction of black pixels relative to the rest of the image is calculated (equation E2), this surface fraction being considered equivalent to the porosity rate:

[0048] %porosity = # (E2) METALLIC POWDER 4

[0049] The metal powder 4 preferably comprises 75% by mass or more of spherical grains, relative to the total mass of the powder.

[0050] Laser particle size is measured according to ISO 13320:2019.

[0051] The diameter of the powder grains is advantageously between 10 and 50 pm, in particular between 12 and 45 pm, and preferably has a D50 value between 20 and 30 pm.

[0052] The melting temperature of the powder components is typically higher than the parison temperature—which can reach 1100 °C—in order to prevent thermal degradation of the lubricating coating 6 during molding. Preferably, the melting temperature of the powder component with the lowest melting temperature is 300 °C higher than the parison temperature.

[0053] The "packed density" is evaluated according to the basis of standard NF EN ISO 3923 (2018) relating to "Metal powders - Determination of apparent density after compaction". Typically, a 25 cm³ volume test cylinder and a KERN SEAL balance with a maximum capacity of 6000 g and a resolution of 0.1 g are used. Compaction is stopped after 3000 blows.

[0054] The "true density" is evaluated according to the basis of standard NF EN ISO 8130-2 (2011) relating to "Coating powders - Determination of density using a gas pycnometer (reference method)". A helium pycnometer (Quantachrome Upyc 1200 e) with a 10 cm³ cell is used. The mass of the powder is measured with a balance, for example METTLER TOLEDO AB 104 with a maximum capacity of 110 g and a resolution of 0.1 mg.

[0055] The packed density of the metal powder is typically between 3 and 7 g / cm3

[0056] The true density is typically between 6 and 10 g / cm3, preferably with a low standard deviation, for example of 0.001. Metallic powders having such a true density make it possible to obtain a denser solid deposit.

[0057] For the purposes of the present invention, a powder is "essentially made up" of a compound A when the powder comprises at least 99% by mass of compound A, relative to the total mass of the powder.

[0058] The metal powder 4 comprises a first powder called "matrix" to enable its adhesion to the molding surface 2. This first matrix powder gives the coated mold improved thermomechanical and / or heat diffusion properties.

[0059] The metal powder 4 also includes, in addition to the matrix powder, a lubricating powder, to facilitate the penetration of the parison into the glass mold 1 and to facilitate the demolding of the blank.

[0060] The metal powder 4 has a lubricating powder content of 3% to 10% by mass, typically 5% by mass, relative to the total mass of the metal powder 4.

[0061] The metal powder 4 is advantageously obtained by simply mixing the matrix powder and the lubricating powder. Those skilled in the art will be able to determine the duration, type, and intensity of agitation necessary to obtain a homogeneous lubricating metal powder.

[0062] Lubricating powder

[0063] The lubricating powder may comprise or consist of a metal oxide in powder form. Preferably, the lubricating powder comprises or is essentially composed of titanium oxide (denoted TiO2).

[0064] The lubricating powder advantageously comprises at least 95% by mass, very advantageously at least 98% by mass of spherical grains, relative to the total weight lubricating powder.

[0065] The packed density of the lubricating powder is typically between 0.8 and 1.8 g / cm3, in particular between 1.0 and 1.5 g / cm3. The true density of the lubricating powder is typically between 3.5 and 4.5 g / cm3, in particular between 3.8 and 4.2 g / cm3.

[0066] The particle size of the lubricating powder is advantageously between 5 and 40 µm. The D50 value of the lubricating powder is typically between 15 and 20 µm.

[0067] Matrix powder comprising a NiCr alloy

[0068] According to a first embodiment, the matrix powder comprises or is essentially composed of a nickel-chromium alloy (called a nickel-chromium alloy and denoted NiCr). A coating comprising NiCr provides the mold with thermomechanical protection. In particular, a coating comprising NiCr gives the mold improved abrasion resistance, which is particularly useful in the case of molds for borosilicate glasses.

[0069] The nickel content in the NiCr alloy is advantageously between 40% and 85% by mass, preferably between 45% and 80% by mass, relative to the total mass of the NiCr alloy, the remainder being essentially made up of chromium.

[0070] For example, the nickel content in the NiCr alloy is between 40 and 50% by mass, while the chromium content is between 50% and 60% by mass, relative to the total mass of the NiCr alloy.

[0071] The particle size of the NiCr matrix powder is advantageously between 10 and 40 pm. The D50 value of the NiCr powder is typically between 20 and 30 pm.

[0072] The packed density of the NiCr matrix powder is typically between 4 and 5 g / cm3, in particular between 4.3 and 4.8 g / cm3. The true density of the NiCr matrix powder is typically between 7.5 and 8.5 g / cm3, in particular between 7.6 and 8.0 g / cm3.

[0073] According to an example of an implementation of this first embodiment, the metal powder 4 comprises or is essentially composed of: - 90 to 97% by mass, for example 95% by mass, of NiCr; and - 3 to 10% by mass, in particular 5% by mass, of titanium dioxide.

[0074] According to this example, the metal powder 4 can be obtained by mixing NiCr powder with titanium dioxide powder for 15 to 24 hours to obtain a homogeneous powder, for example, for 17.5 hours, and then the mixture is placed in an airtight container until use. To improve the homogeneity of the deposit, the mixture can be placed under an inert atmosphere in the airtight container.

[0075] Matrix powder comprising a cupronickel-type alloy

[0076] According to a second embodiment, the matrix powder comprises or is essentially It is essentially composed of an alloy of copper, nickel, aluminum, and zinc, which, for the sake of simplicity, will be referred to as "cupronickel" hereafter. A coating containing this "cupronickel" alloy gives the mold better heat diffusion properties, allowing the glass to cool more evenly upon contact with the coated mold. Such a coating is particularly advantageous in the case of molds for soda-lime glasses.

[0077] According to this second embodiment, the matrix powder comprises or is essentially composed of a powder of an alloy comprising, by mass relative to the total mass of the alloy: between 60 and 70%, preferably between 62 and 68%, of copper; between 7 and 17%, preferably between 10 and 15%, of nickel; between 5 and 15%, preferably between 8 and 12%, of aluminium; between 5 and 15%, preferably between 8 and 12%, of zinc; the possible supplement preferably consisting mainly of chromium, manganese and / or iron.

[0078] Typically, the additive represents at most 3% by mass relative to the total mass of the alloy. Preferably, the additive comprises, by mass relative to the total mass of the alloy: at most 1% chromium; at most 1% manganese; and at most 1% iron.

[0079] The packed density of the "cupronickel" matrix powder is typically between 1 and 6 g / cm3, in particular between 4.5 and 5.5 g / cm3. The true density of the "cupronickel" matrix powder is typically between 4 and 9 g / cm3, in particular between 7.5 and 9.0 g / cm3.

[0080] The particle size of the "cupronickel" matrix powder is advantageously between 15 and 45 µm. The D50 value of the "cupronickel" powder is typically between 20 and 30 µm.

[0081] According to an example of an implementation of this second embodiment, the metal powder 4 then comprises or is essentially made up of: - 90 to 97% by mass, for example 95% by mass, of cupronickel; and - 3 to 10% by mass, in particular 5% by mass, of titanium dioxide.

[0082] According to this example, the metal powder 4 can be obtained by mixing the cupronickel powder with the titanium dioxide powder for 15 to 24 hours to obtain a homogeneous powder, for example, for 17.5 hours, and then the mixture is placed in an airtight container until use. To improve the homogeneity of the deposit, the mixture can be placed under an inert atmosphere in the airtight container.

[0083] EXAMPLE OF MOLD LUBRICATION 1 GLASSWARE

[0084] An example of the lubrication of a glass mold 1 will now be described, with reference to [Fig.4]. I - Materials and methods

[0085] Preparation of the metal powder 4

[0086] The metal powder 4 is obtained by mixing a NiCr matrix powder with a TiO2 lubricating powder, in the following proportions:

[0087] - 95% by mass of NiCr powder comprising 50% by mass of nickel and 50% of mass of chromium (i.e., in the total powder, 47.5% by mass of nickel and 47.5% by mass of chromium); and - 5% by mass of titanium dioxide powder.

[0088] These powders are mixed for 17.5 hours to obtain a homogeneous metal powder 4, which is placed in a hermetically sealed container until use.

[0089] The NiCr powder used consists of an alloy comprising approximately 50% by mass of Nickel and approximately 50% by mass of Chromium. It is marketed by SANDVIK OSPREY.

[0090] The melting point of the NiCr compound is 1345 °C.

[0091] The NiCr powder comprises at least 75% by mass, advantageously at least 80% by mass of spherical grains, relative to the total weight of the NiCr powder.

[0092] The average value of the packed density after three measurements is 4.7 g / cm3.

[0093] The test portion of powder for measuring the true density was 30.8561 g. The The average value of the true density after five measurements was 7.71 g / cm3 with a standard deviation of 0.001.

[0094] Three measurements were carried out to determine the parameters D10, D50 and D90 (laser particle size analysis). The average of these parameters is as follows: -D10= 14.7 pm; - D50 = 26.1 pm; and - D90 = 44.0 pm.

[0095] The TiO2 powder used is marketed by Saint Gobain under the name "TiO2 anastase nanostructured powder".

[0096] The TiO2 powder comprises at least 95% by mass, advantageously at least 98% by mass, of spherical grains, relative to the total weight of the TiO2 powder. The surface appearance of the grains is very smooth. At least 80% by weight of the grains exhibit internal porosity, relative to the total weight of the TiO2 powder.

[0097] The average value of the packed density after three measurements is 1.2 g / cm3.

[0098] The true density was measured under the same conditions as for the NiCr compound, with a test dose of 7.3359 g of powder. The average value of the true density after five measurements was 4.16 g / cm3 with a standard deviation of 0.002.

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[0103]

[0104]

[0105] Laser particle size analysis was performed under the same conditions as for the NiCr compound: the average of these parameters is as follows: - D10 = 8.80 pm; - D50 = 17.8 pm; and - D90 = 33.9 pm. Preparation of representative plates of the molding surface of a glass mold Four flat plates 22 are prepared. Each plate 22 has a free surface 21 representative of the molding surface 2 of a glass mold 1 and intended to receive a drop of glass. The four plates 22 are made of graphite cast iron with a lamellar micrographitic structure of the same composition. One of these plates 22 is untreated, that is to say that neither the lubricating coating 6 nor even a conventional lubricant such as graphite-loaded grease is applied to its free surface 21. A second of these plates 22 has its free surface 21 coated with a conventional lubricant comprising a graphite-filled grease. This grease, of the KleenMold® brand, comprises: - the following solid particles: calcium (Ca), sulfur (S), carbon (C), oxygen (O) and calcium carbonate (CaCO3), and - the following binders: sulfur (S), silicon (Si) and chlorine (Cl). A third of the plates 22 has its free surface 21 covered with a first lubricating coating 6 obtained according to the lubrication process 100 of this presentation, with the following parameters: - 7 Laval type ceramic projection nozzle (convergent divergent) with an outlet diameter of 6 mm; - projection gas 3: nitrogen; - temperature and pressure of the gas in the pressurization chamber 12: 1000°C, 50 bars; - cooling fluid: distilled water; - distance between the exit of the projection nozzle 7 and the impact zone on the molding surface 2: 20 mm; - projection nozzle travel speed 3: 800 mm / s; - metallic powder 4: consisting of nickel-chromium and titanium dioxide, as described above, at room temperature (20°C); - flow rate of supply of the metal powder 4 by the distributor 13: 11.872 cmVmin; - carrier gas flow rate: 4.5 m3 / h; - thickness of solid deposit 5: 0.5 mm; - thickness of the lubricating coating after machining of the solid deposit: 0.2 mm; - porosity of the coating (after machining of the solid deposit 5): approximately 1.3%; - adhesion of the lubricant coating 6 (after machining of the solid deposit 5): between 35 MPa and 45 MPa.

[0106] A fourth of the plates 22 has its free surface 21 covered with an adhesion undercoat, itself coated with a second lubricating coating 6 obtained according to the lubrication process 100 of the present exposition.

[0107] The bonding undercoat is obtained by cold spraying a powder consisting essentially of a NiCr alloy comprising approximately 80% by mass of Nickel and approximately 20% by mass of Chromium, with the following parameters: - Laval type ceramic projection nozzle (convergent divergent) with an outlet diameter of 6 mm; - projection gas: helium; - temperature and pressure of the gas in the pressurization chamber 12: 750°C, 42 bars; - cooling fluid: distilled water; - distance between the outlet of the projection nozzle and the impact zone on the molding surface: 30 mm; - projection nozzle travel speed: 800 mm / s; - powder supply flow rate: 8.904 cmVmin; - carrier gas flow rate: 3 mVh; - thickness of the solid deposit: between 250 and 350 pm.

[0108] The solid deposit 5 intended to form the second lubricating coating 6 is obtained with the following parameters: - 7 Laval type ceramic projection nozzle (convergent divergent) with an outlet diameter of 6 mm; - projection gas 3: nitrogen; - temperature and pressure of the gas in the pressurization chamber 12: 1000°C, 50 bars; - cooling fluid: distilled water; - distance between the exit of the projection nozzle 7 and the impact zone on the molding surface 2: 20 mm; - projection nozzle travel speed 3: 800 mm / s; - metallic powder 4: consisting of nickel-chromium and titanium dioxide, as described above, at room temperature (20°C); - flow rate of supply of the metal powder 4 by the distributor 13: 11.872 cmVmin; - carrier gas flow rate: 4.5 m3 / h; - thickness of solid deposit 5: 1 mm.

[0109] The solid deposit 5 was then machined to obtain a lubricant coating thickness 6, including the tack coat, of approximately 1 mm. The porosity of the second lubricant coating (excluding the tack coat) was measured at approximately 7.6%. II - Implementation

[0110] The four plates 22 are tested. For this purpose, each plate 22 is placed on a support, the free surface 21 of this plate 22 being oriented horizontally on the support, and a drop of glass 20a, 20b, 20c, 20d is applied to the free surface 21 of the plate 22 while the plate 22 is heated: - a first drop of glass 20a is applied to the free surface 21 of the first plate 22, - a second drop of glass 20b is applied to the free surface 21 of the second plate 22, - a third drop of glass 20c is applied to the free surface 21 of the third plate 22, and - a fourth drop of glass 20d is applied to the free surface 21 of the fourth plate 22.

[0111] The temperature of each plate 22 is measured between 440 °C and 450 °C when the glass drop 20a, 20b, 20c, 20d is deposited on the plate 22.

[0112] The glass composing the drops 20a, 20b, 20c, 20d is the same for the four plates 22. It has the following composition (the contents are expressed as mass percentages): B2O3: 0.66% Na2O: 18.9% MgO: 3.14% A12O3:1.87% SiO2: 69.7% SO3: 0.15% K2O: 0.06% CaO: 5.24% TiO2: 0.025% Cr2O3: < 0.020% Fe2O3: 0.072% ZrO2:0.021% BaO: < 0.02% PbO: 0.014%.

[0113] For all elements except boron, the content was determined by quantitative analysis of the glass using X-ray fluorescence spectrometry (XRF). To this end, a first glass sample was obtained by grinding and forming molten beads, which were then dissolved in a lithium tetraborate stream. The sample was subsequently analyzed using a BRUKER S4 Pioneer wavelength-dispersive sequencing spectrometer.

[0114] For boron, the content was determined by plasma-excited atomic emission spectrometry. For this purpose, a second glass sample was obtained by acid dissolving the sample after alkaline fusion and removal of interfering cations. The sample was then analyzed using a Varian Vista MPX plasma-excited atomic emission spectrometer.

[0115] From the element contents thus obtained, the oxide contents were deduced by calculation.

[0116] The glass composing the drops 20a, 20b, 20c, 20d also has the following physical parameters: - coefficient of thermal expansion (between 20°C and 300°C): 9.9x10 6+0.1x106 K1; - glass transition temperature: 513±6°C; - softening temperature (Littleton point): 676±4°C; - working temperature: 967+3°C; - density: 2.484+0.003 g / cm3.

[0117] Finally, the viscosity curve of said glass is shown in [Fig. 5]. These parameters and this curve are determined by applying ISO 7884.

[0118] The flow temperature of the glass droplets (parison) 20a, 20b, 20c, 20d is measured to be between 1050 °C and 1200 °C upon contact with the free surface 21 of the plate 22. Their flow velocity is approximately 4 m / s. The diameter of each glass droplet 20a, 20b, 20c is approximately 7 mm and its mass is 0.38 ± 0.04 g. III - Results

[0119] The geometric properties of the drops 20a, 20b, 20c, 20d obtained are measured in order to determine the ability of the lubricating coating 6 to improve the sliding and / or promote the detachment of the drop 20 on the free surface 21 of the plate 22.

[0120] For this purpose, each glass droplet 20a, 20b, 20c, 20d is filmed using a high acquisition frequency camera in order to determine its geometric characteristics between 0 and 3 seconds after impact (i.e. while the droplet is liquid, before it sets) and to deduce the ability of the lubricating coating to allow the sliding and / or detachment of the droplet 20a, 20b, 20c, 20d on the free surface 21 of the plate 22.

[0121] The measurements are performed by image processing and polynomial interpolation of the drop shape 20a, 20b, 20c, 20d on the four plates 22.

[0122] The average measurements (obtained after measurements taken on three hundred images and related to the initial diameter d0 of the drop during the fall, before impact) are as follows: First drop 20a (plate without lubricant or lubricant coating 6) Second drop 20b (plate coated with a conventional lubricant) Third drop 20c (plate with lubricant coating 6 (NiCr-TiO2) having an average porosity of 1.3%) Fourth drop 20d (plate with lubricant coating 6 (NiCr-TiO2) having an average porosity of 7.6%) Drop diameter at the interface with plate 22 (dsut / do) 1.15 1.25 1.16 0.90 Maximum drop diameter (dmax / d0) 1.24 1.24 1.24 1.12 Maximum drop height (hmax / d0) 0.60 0.55 0.55 0.65 Drop wetting angle (0) 125° 115° 130° 145°

[0123] The wetting angle 0 of a drop 20a, 20b, 20c, 20d corresponds to the angle formed between the tangent to the free surface 21 of the plate 22 and the tangent to the surface of the drop 20a, 20b, 20c, 20d at the interface between the drop 20a, 20b, 20c, 20d and the free surface 21 of the plate 22.

[0124] Thus, all the measured geometric parameters show that the wetting of a glass drop on the free surface 21, when coated with the lubricating coating 6 of the plate 22, is reduced compared to the wetting of a substantially identical glass drop on the free surface of a conventionally lubricated plate 22 treated (graphite grease) or untreated.

[0125] The lubricating coating 6 therefore reduces the adhesion of the parison to the molding surface 2 and facilitates its detachment and penetration (sliding) into the glass mold 1 and the demolding of the blank. Thus, it is possible to reduce the frequency of lubrication of the mold 1, or even to eliminate the need for any further lubrication of the mold 1, without compromising the lubrication performance of the mold 1. Lubrication costs can therefore be reduced, and the production rate increased.

Claims

Demands

1. Method for lubricating (100) a molding surface (2) of a glass mold (1) comprising the following steps: - cold spraying (110) of a solid metallic powder (4) onto the molding surface (2) of the glass mold (1) so as to obtain a solid deposit (5); and - machining (120) of the solid deposit (5) so as to obtain a lubricating coating (6).

2. Lubrication method (100) according to claim 1, wherein the metal powder (4) is projected using a projection gas (3) subjected to a pressure greater than thirty bars, for example between forty bars and seventy bars, for example about fifty bars.

3. A lubrication method (100) according to any one of claims 1 or 2, wherein the metal powder (4) is projected using a projection gas (3) heated to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C.

4. Lubrication method (100) according to any one of claims 1 to 3, wherein during the projection step (110), a projection distance, corresponding to a distance between a projection nozzle (7) of the metal powder (4) and the molding surface (2), is between 15 millimeters and 30 millimeters, preferably equal to about 20 millimeters.

5. Lubrication method (100) according to any one of claims 1 to 4, wherein during the projection step (110), a displacement speed of a projection nozzle (7) of the metal powder (4) during projection is between 500 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example equal to about 800 millimeters per second (mm / s).

6. Lubrication method (100) according to any one of claims 1 to 5, wherein the projection step (110) is carried out for a sufficient duration to obtain a solid deposit (5) having a thickness of between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter.

7. A lubrication method (100) according to any one of claims 1 to 6, wherein an injection rate of the metal powder (4) into the gas of projection (3) is between 5,936 and 17,808 cmVmin, preferably between 8,904 and 14,840 cmVmin, for example of the order of 11,872 cm3 / min.

8. Lubrication method (100) according to any one of claims 1 to 7, wherein said metal powder (4) comprises and is advantageously essentially made up of, by mass relative to the total mass of the powder: - between 90 and 97%, for example 95%, of NiCr powder; and - between 3 and 10%, for example 5%, of titanium dioxide powder, the nickel content in the NiCr powder being between 40 and 50% by mass and the chromium content being between 50% and 60% by mass, relative to the total mass of the NiCr powder.

9. Lubrication method (100) according to claim 8, wherein a particle size of the NiCr powder is between 10 and 40 micrometers and a particle size of the titanium dioxide powder is between 5 and 40 micrometers.

10. A lubrication method (100) according to any one of claims 1 to 7, wherein said metal powder (4) comprises and advantageously consists essentially of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminum; • between 5 and 15%, preferably between 8 and 12%, of zinc

11. Lubrication method (100) according to claim 10, wherein a particle size of the metal powder (4) is greater than or equal to 15 microns and less than or equal to 45 microns.

12. Glass mold (1) comprising: - a molding surface (2); and - a lubricating coating (6) covering all or part of the molding surface (2) and comprising a metallic alloy obtained by cold spraying a metallic powder (4) onto the molding surface (2) according to a lubrication process (100) according to any one of claims 1 to 7.

13. Glass mold (1) according to claim 12, wherein the metal powder (4) is essentially made up of nickel, chromium and titanium dioxide.

14. Glass mold (1) according to any one of claims 12 and 13, wherein the molding surface (2) comprises at least one of the following materials: graphite cast iron with a lamellar, vermicular or spheroidal micrographitic structure, a copper and tin-based alloy such as bronze, iron-carbon steel, refractory steel or stainless steel, brass.

15. Glass mold (1) according to any one of claims 12 to 14, wherein the lubricating coating (6) is obtained by cold spraying: * either of a metallic powder comprising and advantageously consisting essentially of, by mass relative to the total mass of the powder: - between 90 and 97%, for example 95%, of NiCr powder; and - between 3 and 10%, for example 5%, of titanium dioxide powder, the nickel content in the NiCr powder being between 40 and 50% by mass and the chromium content being between 50% and 60% by mass, relative to the total mass of the NiCr powder and a particle size of the NiCr powder being between 10 and 40 micrometers and a particle size of the titanium dioxide powder being between 5 and 40 micrometers;* either of a metallic powder (4) comprising and advantageously consisting essentially of, by mass relative to the total mass of the powder: - between 60 and 70%, preferably between 62 and 68%, of copper; - between 7 and 17%, preferably between 10 and 15%, of nickel; - between 5 and 15%, preferably between 8 and 12%, of aluminum; - between 5 and 15%, preferably between 8 and 12%, of zinc, a particle size of the metallic powder (4) being greater than or equal to 15 microns and less than or equal to 45 microns.

16. An installation comprising a lubrication machine (10) for a glass mold (1) including: - a support (17) configured to receive a glass mold (1) having a molding surface (2); and - a projection nozzle (7) configured to cold-project a solid metal powder (4) onto the molding surface (2) so as to obtain a solid deposit (5); and a machining station (11) configured to machine the solid deposit (5) and obtain a lubricating coating (6).

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