Metal cutting, welding, cladding or additive manufacturing process using laser beam with improved inerting, Installation with associated inerting system.

Abstract

Method for cutting, welding, cladding, or additive manufacturing of metal using an enhanced inert gas laser beam, Installation with associated inert gas system. The invention relates to a method for cutting, welding, cladding, or additive manufacturing using a laser beam, comprising the following steps: a / performing, within an inert gas chamber under an inert atmosphere, at least one cutting, welding, cladding, or additive manufacturing operation of a part using at least one laser beam directed towards a zone in which the part is defined; b / injecting an inert gas into the chamber, towards the zone; c / extracting the injected gas, which may carry dust and / or fumes from step a, from the chamber. Figure for the abstract: Fig. 1

Description

Title of the invention: Method for cutting, welding, cladding or additive manufacturing of metal by laser beam with improved inerting, Installation with associated inerting system. technical field

[0001] The present invention relates mainly to the field of metal additive manufacturing.

[0002] More particularly, the invention relates to an improvement of inerting during an additive manufacturing process using a laser beam.

[0003] Although described in particular with reference to a wire laser additive manufacturing process for metals, known by the Anglo-Saxon acronym WLAM for "Wire Laser Additive Manufacturing", the invention relates more generally to any process for cutting, welding, cladding, metal additive manufacturing, by laser beam in all industrial, engineering and parts manufacturing fields, particularly in the nuclear field. Previous technique

[0004] The WLAM process is a relatively recent process currently under development. This process allows for the design of parts or shapes using design software. A part is produced layer by layer to obtain the thinnest possible layers. The layers are then deposited successively by the additive manufacturing system. Thus, the WLAM process is comparable to traditional 3D printing, but with the use of a metal filament melted by a laser instead of plastic filament melted by a nozzle.

[0005] Compared to selective laser melting (SLM) and laser powder deposition (LMD), a WLAM process offers numerous advantages, notably its suitability for designing large parts and its ability to meet high production rates. The laser uses 1 to 2 mm spots, producing much more localized heat. A WLAM process thus makes it possible to build parts that could not be produced using wire arc additive manufacturing (WAAM).

[0006] In addition, the use of wire makes it possible to guarantee a material yield of 100%.

[0007] Furthermore, in a WLAM process, the risks associated with the use of a powder are eliminated. A WLAM process thus allows for a significant reduction in costs related to personal protective equipment and the health monitoring of operators.

[0008] Despite all the aforementioned advantages, the level of technological maturity of a WLAM process is lower than for the WAAM process.

[0009] In general, laser-based metal welding and additive manufacturing processes differ mainly from arc processes such as TIG welding, an Anglo-Saxon acronym for "Tungsten Inert Gas" or MIG, an Anglo-Saxon acronym for "Metal Inert Gas", in that they are carried out at higher welding speeds, higher power densities and higher melting temperatures.

[0010] This implies significant temperature gradients around the molten pool, resulting in the convection of contaminated gas around the molten pool. This generates impurities that impair the technical performance of the parts produced: appearance of cracks, crevices, bubbles, impurities, etc.

[0011] In particular, it is observed in the case of a WLAM process that the solutions usually employed for inerting do not limit the defects mentioned above. It should be noted here that inerting involves the use of inert gases such as argon, nitrogen, or helium. These inert gases can ensure the quality of the parts produced by protecting the molten materials during manufacturing. It also allows for control of the atmosphere during the additive manufacturing process.

[0012] Thus, conventional inerting systems are not sufficiently effective in protecting the molten pool. The thermodynamic effects of very hot inerting gases do not ensure optimal protection.

[0013] There is therefore a need to improve the inerting solutions of a WLAM process, and more generally, of any cutting, welding, cladding or additive manufacturing process using a laser beam, in particular in order to overcome the aforementioned disadvantages, that is to say in order to reduce the defects generated by the polluted gas around the melt pool, to increase the quality of the latter, to increase the mechanical resistance of parts obtained by such a process in order to get closer to the standards in force.

[0014] The aim of the invention is to meet at least part of this need. Description of the invention

[0015] To this end, the invention relates, in one of its aspects, to a method of cutting, welding, cladding or additive manufacturing by laser beam, comprising the following steps:

[0016] a / carrying out, within an inerting chamber under an inert atmosphere, at least one cutting operation, at least one welding operation, at least one hardfacing operation, or at least one additive manufacturing of a part using at least one laser beam directed towards an area in which the part is defined;

[0017] b / injection of an inerting gas into the enclosure, towards the zone;

[0018] c / aspiration of the injected gas, which may carry dust(s) and / or smoke(s) from step a / , outside the enclosure.

[0019] The inerting gas to be injected can be argon or nitrogen.

[0020] According to a first advantageous embodiment, the process includes, before step b / , at least one step al / of filtration and / or cleaning of the gas to be injected.

[0021] According to this first mode and according to an advantageous variant, the process includes a collection step a2 / of the dust(s) and / or fume(s) from the filtration according to step al / .

[0022] According to a second advantageous embodiment, the process includes, before step b / , a step a3 / of refrigerating the gas to be injected.

[0023] Advantageously, step b / and step c / are carried out in a closed fluidic circuit including the enclosure so that the gas aspirated according to step c / is that to be injected according to step b / , having been previously filtered and / or cleaned, and where appropriate, refrigerated.

[0024] The invention also relates to a laser beam cutting, welding, cladding or additive manufacturing installation, comprising:

[0025] - an inerting chamber, under an inert atmosphere, housing a support for a part to be produced by cutting, welding or additive manufacturing, and at least part of at least one laser adapted to emit a beam for cutting, welding, cladding or additive manufacturing;

[0026] - at least one fluidic line for injecting an inerting gas into the enclosure, towards an area for the production of the part;

[0027] - at least one fluidic line for suction of the injected gas, capable of being a carrier dust(s) and / or smoke(s) from step a / , outside the enclosure.

[0028] According to a first advantageous embodiment, the installation includes at least one filter and / or a device for cleaning the gas to be injected, arranged on the fluidic injection line.

[0029] According to this first mode and an advantageous embodiment, the fluidic injection line includes a collection container, of the ash-box type, for the dust(s) and / or smoke(s) resulting from filtration by the filter(s).

[0030] According to a second advantageous embodiment, the installation includes a refrigeration unit for the gas to be injected, arranged on the fluid injection line.

[0031] Advantageously, the installation includes a closed fluidic circuit comprising the enclosure, a suction pump, the suction fluidic line being connected downstream to the injection fluidic line so that the gas aspirated by the pump is that to be injected, previously filtered and / or cleaned, and where appropriate refrigerated.

[0032] According to another advantageous embodiment, the installation includes a control unit for regulating the operation of the components of the fluidic circuit, including at least the suction pump and, where applicable, the refrigeration unit.

[0033] State-of-the-art laser-based cutting, welding and additive manufacturing processes make it possible to achieve high working speeds at high temperatures.

[0034] On the other hand, it has been observed that these processes generate more or less pollution, in particular dust(s) and / or smoke(s) from the melting bath generated by the laser, depending on the materials melted.

[0035] The inventors carried out thermodynamic analyses of inerting gas which showed that the very hot flows are violently disturbed and do not perform at their best what they are dedicated to, which deteriorates the quality of the inerting, and is therefore likely to cause defects during manufacturing.

[0036] However, in a process for industrial purposes, it is imperative to obtain precise and reproducible technical characteristics on the parts cut, welded or manufactured by addition.

[0037] The inventors therefore sought to optimize these characteristics as much as possible by eliminating as many defects as possible during the manufacture of said parts.

[0038] The invention essentially consists of ensuring the quality of the inerting gas injected into the inerting chamber in which the laser beam is used for manufacturing, by filtering and / or cleaning it before its injection, and simultaneously extracting the gases from the manufacturing process that may carry any pollution, from outside the chamber.

[0039] Advantageously, a closed cycle is implemented which allows the inerting gases to be filtered and advantageously cooled, in order to reinject them into the inerting chamber during the operating cycles of the manufacturing process.

[0040] The advantages of the invention are numerous, among which we can mention: - an improvement in the quality of the melting baths of a manufacturing process by cutting, welding or laser additive manufacturing by reducing the defects / impurities that may be retained during manufacturing; - an advantageous reduction in the cost of operations through closed-cycle recycling of the inerting gas; - an improvement in the quality of welds and parts produced with laser cutting, or laser beam welding and laser metal additive manufacturing processes.

[0041] The potential applications of the described invention are that its installation can be carried out on all types of hermetic inerting chambers / enclosures, whether rigid or flexible.

[0042] All industrial applications of laser welding and additive manufacturing are concerned, particularly nuclear, aeronautical, naval, and automotive.

[0043] Other advantages and features of the invention will become clearer from the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0044] [Fig-1] [Fig.1] is a schematic view of an additive manufacturing installation Laser-cut metallic structure with a hermetically sealed inerting chamber implementing a system for inerting the injected gas, which is then recycled for reinjection according to the invention. Detailed description

[0045] Throughout this application, the terms "upstream", "downstream", "inlet" and "outlet", "above" are to be understood by reference to the direction of fluid flow in an installation according to the invention, as it is in its operating configuration.

[0046] A laser-based metal additive manufacturing installation 1 according to the invention is shown in [Fig.1].

[0047] This installation first comprises an inerting chamber 10, under an inert atmosphere, housing a support 11 for a part P undergoing treatment by welding, cladding, or additive manufacturing. The inert atmosphere can be controlled by means of an oxygen sensor 12 and advantageously by means of water. The temperature inside the chamber 10 can be controlled by means of a temperature sensor 13.

[0048] A laser head 14 is also housed in the enclosure 10. The laser is adapted to emit an additive manufacturing beam towards a zone Z within which the part P is manufactured.

[0049] To perform the fusion by the laser 14, powder or a metal wire is fed by a feeding device 2 comprising a reservoir 20 and a fluidic feed line 21 connected downstream to the reservoir 20 and which opens into zone Z. The feed can be interrupted by the actuation of a solenoid valve 22 on the line 21. A flow meter 23, preferably downstream of the solenoid valve 22, allows the flow rate of metallic material (powder or wire) to be injected into zone Z to be regulated as desired.

[0050] The inerting chamber is equipped with an airlock (not shown), adapted for extracting small parts produced without breaking the inerting process. For the larger For large parts that can be manufactured within the enclosure, the airlock may not be large enough. In this case, one of the side panels delimiting the enclosure can be removed to extract the parts.

[0051] According to the invention, a closed fluidic circuit 3 comprising the enclosure 10 is arranged in the installation to inject into the zone Z an inerting gas, such as argon or nitrogen, and to draw the gases likely to carry pollutants (dust, fumes) from the melting process of the metallic material out of the enclosure and filter them and where appropriate clean them for re-injection as the inerting gas.

[0052] Thus, the circuit includes first of all at least one fluidic line 30 for injecting the inerting gas into the enclosure 10, towards the zone Z and at least one fluidic line 31 for sucking up the injected gas, which may carry dust(s) and / or smoke(s) from the manufacturing process, outside the enclosure.

[0053] A suction pump 4 on line 31 allows the desired suction to be achieved.

[0054] As illustrated, the suction fluid line 31 is connected downstream to the injection fluid line 30.

[0055] A filter 32, preferably two filters 32, 33 are arranged on the fluid line of aspiration 31 and therefore of injection 30.

[0056] A collection container 320, of the ashtray type, for dust(s) and / or smoke(s) from filtration by the upstream filter 32.

[0057] A refrigeration unit 5 for the gas to be injected is arranged on the injection fluid line 30.

[0058] Thus, the operation of the closed inerting circuit 3 allows the gas aspirated by the pump 4 to be reinjected from the enclosure 10, which has previously been filtered by the filters 32, 33, and cooled by the unit 5.

[0059] The injection of the gas and the aspiration of the polluting gases can be interrupted by the actuation of a solenoid valve 35, 36 respectively on line 30 and on line 31.

[0060] The inert atmosphere can be controlled by means of one, preferably two oxygen sensors 37, 38 and advantageously water sensors, respectively downstream of the solenoid valve 34 and upstream of the solenoid valve 35.

[0061] A flow meter 38, preferably upstream of the solenoid valve 35, allows the flow of inerting gas to be injected into zone Z to be regulated as desired.

[0062] The installation advantageously includes a control unit to regulate the operation of the components of the fluidic circuit 3, including at least the suction pump 4 and the refrigeration unit 5.

[0063] The closed inerting circuit 3 makes it possible to remove the greatest number of impurities generated by the process, by drawing in, by means of the pump 4, the hot gases carrying dust and fumes from zone Z. These hot gases are then filtered by filters 32, 33 with the filtered solid particles collected in the ash 320. Then, this filtered gas, which can be cleaned if necessary, is cooled by unit 5 and then reinjected into enclosure 10.

[0064] Thus, with such a closed circuit 3, not only is the quality of the part P improved by reducing the defects / impurities likely to be retained during its manufacture, but also operating costs are reduced due to the recycling of the inerting gas in a closed circuit.

[0065] The invention is not limited to the examples just described; in particular, characteristics of the illustrated examples can be combined within unillustrated variants.

[0066] Other variants and embodiments may be envisaged without departing from the scope of the invention.

Claims

Demands

1. Installation for laser beam cutting, welding, cladding or additive manufacturing, comprising: - an inerting chamber, under an inert atmosphere, housing a support for a part to be produced by cutting, welding or additive manufacturing, and at least part of at least one laser adapted to emit a beam for cutting, welding, cladding or additive manufacturing; - at least one fluidic line for injecting an inerting gas into the chamber, towards a part production area;- at least one fluid line for the suction of the injected gas, which may carry dust and / or fumes from step a, outside the enclosure; - at least one filter and / or a device for cleaning the gas to be injected, arranged on the injection fluid line; - a closed fluid circuit comprising the enclosure, a suction pump, the suction fluid line being connected downstream to the injection fluid line so that the gas sucked in by the pump is that to be injected, previously filtered and / or cleaned; - a control unit to regulate the operation of the components of the fluid circuit, including at least the suction pump.

2. Installation according to claim 1, the fluidic injection line comprising a collection container, of the ash-box type, for the dust(s) and / or smoke(s) resulting from filtration by the filter(s).

3. Installation according to any one of claims 1 and 2, comprising a refrigeration unit for the gas to be injected, arranged on the fluid injection line.

4. Installation according to claim 3, the control unit being configured to regulate the operation of the refrigeration unit.

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