Method for slowing down the reaction of metal particles

Abstract

Method for slowing down the reaction of metal particles, preferably from an additive manufacturing process, in particular a laser sintering or laser melting process, wherein the metal particles are combined, in particular mixed, with at least partially meltable inert material, in particular wherein the inert material comprises particles with a particle size of less than or equal to 100 pm.

Description

Technical Field

[0001] This invention relates to a method for slowing the reaction of metal particles, particularly metal condensates, the use of fusible inert materials, additive manufacturing processes, manufacturing equipment for additive manufacturing of objects, and compositions, particularly mixtures, containing metal particles. Technical Background

[0003] In various applications, especially in additive manufacturing processes such as laser sintering or laser melting, metal particles (particularly metal condensates) are generated. These particles can ignite due to the corresponding chemical reactions (particularly oxidation) and pose a corresponding hazard.

[0004] To mitigate the risk of overheating, particularly spontaneous combustion, it is known to add lime powder (CaCO3) to such metal particles. However, it has been shown that known methods for slowing the reaction of metal particles still carry considerable risks.

[0005] Therefore, the object of the present invention is to provide a method for mitigating the reaction of metal particles, thereby preventing overheating of the metal particles, particularly spontaneous combustion (or reducing the corresponding risk), in a manner that is as simple yet safe as possible. Furthermore, the object of the present invention is to provide a corresponding use of a fusible inert material (passivating material), a corresponding additive manufacturing process, a corresponding manufacturing apparatus, and a corresponding composition comprising metal particles. Summary of the Invention

[0006] This task is solved by the following features:

[0007] A method for mitigating the reaction of metal particles, particularly metal condensates, wherein the metal particles are preferably derived from an additive manufacturing process, particularly laser sintering or laser melting, wherein the metal particles are combined, particularly mixed, with at least partially fusible inert materials, wherein the inert materials comprise particles with a particle size of less than or equal to 100 μm.

[0008] Preferably, this task is accomplished by slowing the reaction of metal particles, particularly metal condensates, which are preferably derived from additive manufacturing processes, particularly laser sintering or laser melting processes, wherein the metal particles are combined, particularly mixed, with at least partially fusible inert material (passivating material). Particularly preferably, the inert material (passivating material) comprises particles with a particle size less than or equal to 100 µm. Preferably, the particle size is less than or equal to 50 µm, more preferably less than or equal to 30 µm, depending on the situation less than or equal to 20 µm, and / or greater than or equal to 0.1 µm, preferably greater than or equal to 1 µm. A preferred range is, for example, a particle size from 5 µm to 30 µm (for at least 10% by weight, preferably at least 50% by weight of particles).

[0009] The first central idea of ​​this invention is to provide an at least partially meltable inert or passivating material for slowing the reaction of metal particles, wherein the inert material preferably comprises particles with a relatively small particle size (particularly less than or equal to 100 µm). By melting the inert / passivating material, a potential ignition source can be at least partially (and possibly completely) covered, thereby potentially extinguishing it. A particular advantage of melting is that a relatively large amount of heat (enthalpy of fusion) can be absorbed through this process. Due to the relatively small particle size, the inert material may have relatively high viscosity. This improves the slowing of the reaction. Overall, the risk of spontaneous combustion (metal particles in air or an O2-containing atmosphere) is thus synergistically reduced.

[0010] In particular, according to the present invention, lime powder (CaCO3) thermally decomposes at (about) 800°C and releases CO2. Carbon dioxide can decompose at relatively high temperatures (at least about 1500°C) and contribute to combustion via carbon monoxide (CO) and possible oxygen free radicals. In particular, flames may form when fresh or additional oxygen is added (e.g., when removing metal particles from a collecting or receiving device).

[0011] The particle size considered (independent of material; this also applies particularly to metal particles) is preferably the diameter of an individual particle or nucleus. If the particles form at least partial agglomerates (preferably to be avoided as much as possible), the diameter of the individual particles (nuclei) of the agglomerates should be considered. The diameter of an individual particle (particle size) is preferably its respective maximum diameter (= supremum of all distances between any two points of the particle) and / or sieve aperture diameter and / or (especially volume-related) equivalent sphere diameter.

[0012] The individual particles of the inert / passivating material preferably (at least approximately) have the same size (monodispersed). Alternatively, a particle size distribution may exist. If a particle size distribution exists, for example, the d50 particle size may be at least 2 times, preferably at least 4 times, and / or at most 10 times, preferably at most 8 times, the d10 particle size. Optionally or additionally, the d90 particle size may be at least 1.1 times, preferably 1.3 times, and / or at most 3 times, preferably at most 1.7 times, the d50 particle size. Particle size can be determined by sieving, depending on the situation. Optionally or additionally, particle size can also be determined by laser diffraction (particularly by laser diffraction measurement according to ISO 13320 or ASTM B822). Optionally or additionally, particle size can be determined by measurement (e.g., by microscopy) and / or dynamic image analysis (preferably according to ISO 13322-2, optionally by CAMSIZER of Retsch Technology GmbH). ® The particle size is determined by (XT). If the particle size is determined based on a two-dimensional image (e.g., a microscope, especially an electron microscope), it is preferable to use the corresponding diameter (maximum diameter or equivalent diameter) given by the two-dimensional image.

[0013] The diameter perpendicular to the maximum diameter (= the supremum of all distances between the two points of the particle whose connecting line is perpendicular to the maximum diameter) is preferably at least 0.1 times the maximum diameter, more preferably at least 0.5 times, more preferably at least 0.7 times and / or at most 1.0 times, preferably 0.9 times (in three dimensions, or especially in two dimensions relative to the image plane when determining the respective diameter from an image).

[0014] The metal particles may (at least proportionally, optionally all) be round or spherical, and (in the case of non-uniform particles) / or (at least proportionally, optionally all) have angular edges (e.g., produced by grinding or at least can be produced by grinding), and optionally be cubic.

[0015] Preferably, the metal particles comprise at least partially, and optionally, atomic percent primarily: at least one metal, preferably at least one catalytically active metal (e.g., Ni, Co, Fe, Rh, Ru, Pt, Pd, and / or Zr) and / or at least one electrochemically active metal and / or at least one autogenous metal (e.g., Mg, Ti, Ni, Co, Fe, Pb, at least one lanthanide element, and / or at least one actinide element), particularly preferably Al, Fe, Ti, Ni, Co, Pt, Ag, Pd, Sc, Au, Zn, Zr, Mg, V, Si, Cu, Mn, W, Nb, and / or Cr. Furthermore, they may comprise, partially and optionally, atomic percent primarily: Mo, C, and / or O. Each element may preferably be present at at least 5 atomic percent, more preferably at least 20 atomic percent, optionally at least 50 atomic percent, or even at least 90 atomic percent.

[0016] In the addition of manufacturing processes, particularly laser sintering or laser melting processes, manufacturing equipment is preferably used, which is configured to manufacture objects by assembling structural materials, said structural materials comprising at least substantially metallic and / or ceramic components, layering and selectively curing said structural materials, particularly by providing radiant energy at locations in each layer related to the cross-section of the object in that layer. Particularly preferably, at least one laser is used here or a laser sintering process is performed.

[0017] The metal particles preferably have a (optionally average) particle size of at least 1 nm, preferably at least 3 nm, more preferably at least 4 nm and / or up to 1000 nm, preferably up to 100 nm, optionally up to 50 nm. In this case, the particle size is preferably defined or determined according to the particle size of the inert material particles as described above. Individual particles may be (at least substantially or at least approximately) equal in size, or a particle size distribution may exist. If a particle size distribution exists, the d10 particle size may be at least 0.1 times, preferably at least 0.2 times and / or up to 1.0 times, preferably up to 0.9 times, the d50 particle size. Optionally or additionally, the d90 particle size may be at least 1.0 times, preferably at least 1.2 times, more preferably at least 1.4 times and / or up to 10 times, preferably up to 5 times, more preferably up to 4 times, the d50 particle size.

[0018] The metal particles are preferably at least approximately spherical.

[0019] The metal particles may (at least proportionally, optionally all) be round or spherical, and (in the case of non-uniform particles) / or (at least proportionally, optionally all) have angular edges (e.g., produced by grinding or at least can be produced by grinding), and optionally be cubic.

[0020] The diameter perpendicular to the maximum diameter (= the supremum of all distances between the two points of the particle whose connecting line is perpendicular to the maximum diameter) is preferably at least 0.1 times the maximum diameter, more preferably at least 0.5 times, more preferably at least 0.7 times and / or at most 1.0 times, and preferably 0.9 times (in three dimensions, or especially in two dimensions relative to the image plane when determining the respective diameter from an image).

[0021] Preferably, the metal particles have a particle size of at least 0.01 μm. 2 / g, preferably at least 1 m 2 / g, more preferably at least 5 m 2 / g, still more preferably at least 10 m 2 / g and / or up to 1000 m 2 / g, preferably up to 500 m 2 / g, more preferably up to 200 m 2 / g, and more preferably up to 50 m 2The specific surface area is measured per g. Specific surface area can be determined by measuring at least 100, preferably at least 1000 randomly selected particles (e.g., identifiable on a REM image and adjacent to each other) (especially in the case of non-porous particles) so that their surface area and weight (given material density) can be calculated. BET measurements may also be performed, preferably according to DIN ISO 9277 (applicable in the Federal Republic of Germany at the time of application). Gas adsorption (e.g., N2) during the measurement process can depend on the relative pressure P / P0. The amount of adsorbed gas can be determined by the static volumetric method (isotherm). The sample size can be 100 mg. "Quantachrome Nova" ® The 4200e analyzer can be used for measurement.

[0022] At least partially fusible inert materials (passivating materials) are preferably understood as materials that are therefore fusible (i.e., without prior chemical transformation). Materials in which only the residual products are fusible (e.g., after thermal decomposition of the starting products) should not be particularly understood as partially fusible inert materials. In particular, when a certain temperature is exceeded (at a pressure of 1 bar), the partially fusible inert material should (therefore) transform into a liquid phase (before its chemical transformation, e.g., thermal decomposition). Preferably, (when the predetermined temperature is exceeded and at a pressure of 1 bar) the inert material (e.g., in the case of a mixture) should be at least 10% by weight, preferably at least 25% by weight, more preferably at least 50% by weight, more preferably at least 80% by weight, and optionally (at least approximately) completely fusible.

[0023] Inert or passivating materials are preferably understood as materials that slow down the reaction of metal particles, especially in the sense that they can absorb the heat of reaction and thus slow down the reaction.

[0024] The mitigation of the reaction may include: endothermic reaction of the inert material (mitigating material) (especially by heating it), and / or endothermic phase change (e.g., melting) of the inert material (mitigating material) and / or thermal (endothermic) decomposition or transformation of the inert material (mitigating material), for example, for lime (CaCO3->CaO+CO2).

[0025] Optionally or additionally, the slowing down of the reaction may include: spatial separation of the metal particles by an inert material (the slowing material) (so that the metal is no longer next to or on the metal, thereby preferably resulting in a slowing down of thermal conduction), for example, by forming a cladding (protective shell) of an inert material (e.g., potassium glass).

[0026] Optionally or additionally, the mitigation of the reaction may include (or not include, or at least not only include): reducing reactivity by an inert material, preferably by a specific chemical interaction between the metal particles and the inert material, preferably a chemical reaction (optionally, for example, the inert material present as potassium permanganate may release O2). For example, it can be imagined that oxygen molecules attached to the surface of the inert material (e.g., glass powder) react with condensates (through absorption and / or adsorption), thereby reducing reactivity. This can be facilitated, as appropriate, when the inert material becomes very fine (particle size <10 µm) and therefore has a relatively high surface area and / or (also as an optional, independent further development idea, without the aforementioned features of this paragraph) when the inert material is mesoporous (average pore size between 2 and 50 nm) or microporous (average pore size less than 2 nm). In this way, for example, O2 can be carried from the interior of the inert material (in the pores) to the metal particles.

[0027] The specific thermal conductivity (at 25°C) of inert materials can be at least 0.4 W / (m²). K), optionally at least 0.6 W / (m K) and / or up to 2.0 W / (m K) or at most 1.2 W / (m K).

[0028] The specific heat capacity (at 25℃) of inert materials can be at least 0.5 kJ / (kg). K), optionally at least 0.7 kJ / (kg K) or at least 0.8 kJ / (kg) K), and / or at most 3.0 kJ / (kg) K) or at most 2.0 kJ / (kg) K).

[0029] Inert materials may contain oxygen (chemically bonded, surface-attached, and / or internally trapped, such as by adsorption).

[0030] Inert materials may include expandable materials, particularly expanded glass and / or hollow bodies, especially hollow spheres.

[0031] Preferably, the inert material (passivating material) comprises at least 10% by weight, more preferably at least 50% by weight, particles with a diameter less than or equal to 100µm, preferably less than or equal to 50µm, more preferably less than or equal to 30µm, optionally less than or equal to 20µm and / or greater than or equal to 0.1µm, preferably greater than or equal to 1µm. For example, a preferred range is a particle size (at least 10% by weight, preferably at least 50% by weight) in the range of 5µm to 30µm.

[0032] Preferably, the inert material is relatively sticky or flour-like.

[0033] In specific embodiments, the inert material includes glass, particularly glass particles, and / or at least one, preferably low-melting-point and / or hygroscopic (optionally: non-hygroscopic) salt, particularly (corresponding) salt particles. The salt may be present in pure form or as a mixture of different (inherently pure) salts. In this regard, the broader concept of "salt" without further explanation should be understood as pure salt (e.g., NaCl) or a mixture of salts. Hygroscopic salt should be particularly understood as salt that absorbs water at a normal pressure of 1.0 bar and an ambient relative humidity of 50%. Non-hygroscopic salt should be particularly understood as salt that does not absorb water at a normal pressure of 1.0 bar and an ambient relative humidity of 50%. Where appropriate, the salt, particularly salt particles, may include NaCl, sucrose, SiO2 (silica gel), sodium hydroxide, potassium hydroxide, nitrates, salicylates, and / or calcium chlorite. Any of the salts and / or any combination of the salts may be present in the inert material at least 10% by weight. In particular, the salt can be formed from a mixture of salts with a low melting point (eutectic point) (e.g., a mixture of LiCl (e.g. 56 mol%) and KCl (e.g. 44 mol%), which can melt at, for example, 355 °C).

[0034] The inert material may optionally or additionally contain at least one mineral, such as kaolin and / or dolomite and / or (mineral-containing) fly ash, preferably fly ash.

[0035] The inert material may optionally or additionally contain trivalent iron oxide (Fe2O3).

[0036] The inert material may optionally or additionally include quicklime (CaO) and / or water glass (CaOH). The inert material preferably contains less than 10% by weight of lime (CaCO3), more preferably less than 5% by weight of lime, and even more preferably less than 1% by weight. In particular, the inert material is (at least substantially) lime-free.

[0037] Low melting points are generally preferred (e.g., low-melting-point salts or salt mixtures). The melting temperature of at least one fusible component of the inert material (at a normal pressure of 1.0 bar) can be up to 1200°C, preferably up to 800°C, more preferably up to 600°C, and, depending on the situation, up to 450°C or up to 300°C. Relatively low melting temperatures have the particular advantage that (at correspondingly higher temperatures) metal particles can be effectively encapsulated by the inert material, thereby improving safety. The melting temperature mentioned here and below can be understood as the temperature at which at least part of the inert material transforms into a liquid state. Depending on the situation, this can be understood as the state of the inert material (or, in terms of melting temperature, higher and lower), in which at least a portion of the inert material (optionally at least 10% by weight) has a Pa value of less than or equal to 200 Pa. s, especially less than or equal to 25 Pa The viscosity (s at 1.0 bar ambient pressure). Any upper temperature limit given in this paragraph may be combined with any other upper temperature limit to form the scope according to the invention, wherein the lower temperature limit is the smaller of the two respective upper temperature limits.

[0038] The melting temperature of at least one fusible component of the inert material at a normal pressure of 1.0 bar may be at least 100°C, preferably at least 300°C, optionally at least 500°C, or at least 800°C. This, where appropriate, prevents the particles of the inert material from melting during use and from permanently bonding with metal particles during re-curing. This is advantageous in terms of handling and / or recycling. The lower temperature limits given in this paragraph may be combined with any upper temperature limits given in the preceding paragraph to form the corresponding ranges according to the invention, provided that this is not logically excluded. Any lower temperature limit given in this paragraph may be combined with any other lower temperature limit to form the ranges according to the invention, wherein the upper temperature limit is the larger of the two respective lower temperature limits.

[0039] Sodium glass is preferably used as the glass, especially glass particles (at least in proportion, especially at least 10% by weight), and soda-lime glass and / or borosilicate glass and / or expanded glass (expanded glass particles) is particularly preferred.

[0040] The above task is further addressed by using fusible inert materials or passivating materials to slow down the reaction of metal particles (especially metal condensates) from additive manufacturing processes (especially laser sintering or laser melting processes), wherein the inert materials include particles with a particle size of less than or equal to 100 µm.

[0041] In particular, if the material can be converted into a liquid state (by heating) and / or at least converted to a viscosity less than or equal to 200 Pa. s, preferably less than or equal to 25 Pa If the material is in the state of s (at an ambient pressure of 1.0 bar), it should be called a fusible material.

[0042] The above-mentioned task was further addressed by adding manufacturing processes, particularly laser sintering or laser melting processes, which include the aforementioned methods for mitigating the reaction of metal particles, particularly metal condensates.

[0043] The aforementioned task is further addressed by manufacturing equipment for the addition manufacturing of objects, preferably according to the above-described addition manufacturing process, particularly by laser sintering or laser melting equipment, which includes a fusible inert / passivating material for mitigating the reaction of metal particles, particularly metal condensates, originating from the corresponding addition manufacturing process (particularly laser sintering or laser melting), wherein the inert material comprises particles with a particle size less than or equal to 100 µm. According to this aspect of the invention, the manufacturing equipment should, for example, already contain the passivating material (inert material) according to the invention in the container and / or feeding device so that it can be fed into the corresponding metal condensate (in the addition manufacturing process).

[0044] The manufacturing equipment is preferably configured to facilitate the implementation of the above-described method for slowing down the reaction of metal particles and / or the use of the above-described fusible inert material.

[0045] The above-mentioned tasks are further addressed by compositions, particularly mixtures, comprising metal particles, particularly metal condensates, from additive manufacturing processes, particularly the aforementioned additive manufacturing processes, especially laser sintering or laser melting processes, and a fusible inert material (passivating material), wherein the inert material has particles with a particle size of less than or equal to 100 µm. The compositions are specifically configured to facilitate the implementation of the aforementioned methods for mitigating the reaction of metal particles and / or the use of the aforementioned fusible inert material.

[0046] When metal particles are combined with inert materials, especially mixed, or present as a composition, especially a mixture, the weight percentage of inert materials in the composition (mixture) should preferably be at least 2% by weight, more preferably at least 5% by weight, more preferably at least 10% by weight, more preferably at least 30% by weight and / or at most 95% by weight, preferably at most 80% by weight.

[0047] Compositions, especially mixtures, may be present in or (according to the process) placed in containers.

[0048] The inert material may include an oxidant. However, the inert material may, depending on the circumstances, contain less than 50% by weight, more preferably less than 25%, further preferably less than 5%, possibly less than 1% or 0.1% of a material (e.g., lime powder) as a source of the oxidant.

[0049] The inert material (passivating material) can be used in filtration systems, particularly recirculating air filtration systems for manufacturing equipment used in the production of objects, especially laser sintering or laser melting equipment, and / or for materials derived from such filtration systems.

[0050] Other specific embodiments of the present invention will each have the following features:

[0051] - The inert material comprises at least 10% by weight, preferably at least 50% by weight, particles with a diameter less than or equal to 100 μm, preferably less than or equal to 50 μm, more preferably less than or equal to 30 μm, more preferably less than or equal to 20 μm, and / or greater than or equal to 0.1 μm, preferably greater than or equal to 1 μm.

[0052] - The inert material includes glass, particularly glass particles and / or at least one, particularly low-melting-point and / or hygroscopic or non-hygroscopic salts, particularly salt particles.

[0053] - The inert material contains less than 10% by weight of lime, and preferably is at least substantially free of lime.

[0054] - The melting temperature of at least one fusible component of the inert material at a normal pressure of 1.0 bar is at most 1200°C, preferably at most 800°C, more preferably at most 600°C, and, depending on the circumstances, at most 450°C or at most 300°C.

[0055] - At least one fusible component of the inert material has a melting temperature of at least 100°C, preferably at least 300°C, and in some cases at least 500°C or at least 800°C under a normal pressure of 1.0 bar.

[0056] In the following description, the invention will be described with reference to specific embodiments, and these embodiments will be explained in more detail with reference to the accompanying drawings. Attached Figure Description

[0057] This is displayed here:

[0058] Figure 1 A schematic diagram of a cross-section of a device used for layer-by-layer construction of three-dimensional objects;

[0059] Figure 2 A schematic diagram of metal particle formation;

[0060] Figure 3 A schematic diagram showing the minimum ignition temperature in °C and the proportion of inert material in % by weight; and

[0061] Figure 4 A schematic diagram showing the combustion rate in cm / s and the proportion of inert material in weight percent.

[0062] In the following description, the same reference numerals are used for parts that are the same and have the same function.

[0063] Figure 1The apparatus shown is a known laser sintering or laser melting apparatus a1. To construct an object a2, it includes a processing chamber a3 with chamber walls a4. Within the processing chamber a3, an upwardly opening construct container a5 with walls a6 is arranged. A working surface a7 is defined by the upper opening of the construct container a5, and the area of ​​the working surface a7 within the opening (which can be used to construct the object a2) is referred to as the construct region a8. Within the container a5, a support a10 movable in the vertical direction V is arranged, on which a substrate a11 is connected, which closes the construct container a5 at the bottom, thus forming its base. The substrate a11 can be a plate constructed separately from the support a10 and fixed to the support a10, or it can be integrally constructed with the support a10. Depending on the powder used and the process, a construct platform a12 can also be connected to the substrate a11, on which the object a2 is constructed. However, the object a2 can also be constructed on the substrate a11 itself, with the substrate a11 serving as the construct platform. Figure 1 In the laser sintering apparatus a1, the object a2 to be formed on the construction platform a12 in the construction container a5 is displayed in an intermediate state below the working plane a7, surrounded by multiple cured layers of uncured construction material a13. The laser sintering apparatus a1 also includes a storage container a14 for storing powdered construction material a15 that can be cured by electromagnetic radiation and a coater a16 movable in the horizontal direction H for coating the construction material a15 onto the construction area a8. The laser sintering apparatus a1 also includes an irradiation device a20 with a laser a21, which generates a laser beam a22 as an energy beam. This energy beam is deflected by a deflection device a23 and focused by a focusing device a24 onto the working plane a7 through a coupling window a25 disposed on the upper side of the processing chamber a3 in its wall a4.

[0064] Furthermore, the laser sintering apparatus a1 includes a control unit a29, which coordinately controls the various components of apparatus a1 to execute the construction process. The control unit a29 may include a CPU, the operation of which is controlled by a computer program (software). The computer program may be stored separately from the device on a storage medium, from which it can be loaded into the device, particularly into the control unit. In operation, to apply the powder coating, the support a10 is first lowered to a height corresponding to the desired layer thickness.

[0065] A layer of powdered build material a15 is applied by moving the applicator a16 on the working surface a7. For safety, the amount of build material a15 pushed forward by the applicator a16 is slightly larger than the amount required to build this layer. The applicator a16 pushes the predetermined excess build material a15 into the overflow container a18.

[0066] An overflow container a18 is arranged on each side of the build container a5. The powdered build material a15 is applied at least over the entire cross-section of the object a2 to be manufactured, preferably over the entire build area a8, i.e., the area of ​​the working surface a7 lowered by the vertical movement of the support a10. Subsequently, a laser beam a22 scans the cross-section of the object a2 to be manufactured with a radiation area (not shown), which schematically represents the intersection of the energy beam and the working surface a7. In this way, the powdered build material a15 solidifies at the location corresponding to the cross-section of the object a2 to be manufactured. These steps are repeated until the object a2 is completed and can be removed from the build container a5.

[0067] To generate a preferred laminar process gas flow a34 in the processing chamber a3, the laser sintering apparatus a1 also includes a gas supply channel a32, an inlet nozzle a30, an exhaust port a31, and an exhaust channel a33. The process gas flow a34 moves horizontally through the build zone a8. Gas supply and exhaust can also be controlled by a control unit a29 (not shown). Gas discharged from the processing chamber a3 can be conveyed to a filter (not shown), and the filtered gas can be fed back to the processing chamber a3 through the gas supply channel a32, thereby forming a recirculation system with a closed gas loop. In each case, multiple nozzles or openings can be provided instead of just one gas inlet nozzle a30 and one exhaust opening a31.

[0068] In this case, the condensed metal particles can now be present, for example, on wall a4 or (not shown) a filter device and / or removed therefrom. The material should then be preferably slowed down according to the invention.

[0069] exist Figure 2 The diagram schematically illustrates how metal particles are generated based on a hypothetical scenario. Here, a laser beam 10 moves across a surface 11. The corresponding direction of motion is indicated by arrow 12. The laser beam 10 melts the starting material 13, causing a portion of the starting material to vaporize. The molten starting material is marked with reference numeral 16, and the gaseous starting material with reference numeral 17. A so-called vapor capillary is formed at the point of impact of the laser beam. This capillary contains vaporized material (e.g., metal) that exists as plasma at high temperatures. Due to buoyancy and the upward flow of the material from below or subsequent evaporation, it is ejected at high speed from the vapor capillary (keyhole). By cooling the metal vapor, the gas phase becomes supersaturated, leading to condensation (homogeneous condensation). Metal particles 14 are formed by this condensation. Aggregates 15 can still form over a longer period of time.

[0070] exist Figure 3 and Figure 4 The paper explains the effect of inert materials (glass powder in this case) on the minimum ignition temperature and combustion rate of iron condensate (initial point of high alloy steel MS1).

[0071] according to Figure 3 Adding glass powder can significantly increase the minimum ignition temperature at which spontaneous combustion occurs. In contrast, lime powder, at high proportions, results in a significantly lower minimum ignition temperature.

[0072] Using relatively fine particle size, especially to make inert materials relatively sticky, can yield particularly good results.

[0073] according to Figure 4 The combustion rate can be gradually reduced by adding glass powder. It was also found that a relatively fine particle size (core size) is advantageous, as this gives the inert material cohesiveness and allows it to mix well with the metal condensate.

[0074] In this respect, it should be noted that all the foregoing parts, considered individually and in any combination, especially the details shown in the accompanying drawings, are considered essential claims of the invention. Modifications thereof are well known to those skilled in the art.

[0075] Reference Identifier List

[0076] a1 Laser sintering or laser melting equipment

[0077] a2 object

[0078] a3 Processing Room

[0079] a4 Room Wall

[0080] a5 Container Building

[0081] a6 wall

[0082] a7 working surface

[0083] a8 Construction Area

[0084] a10 movable stand

[0085] a11 substrate

[0086] a12 building platform

[0087] a13 Uncured building materials

[0088] a14 storage container

[0089] a15 Powdered Building Material / Aluminum Alloy

[0090] a16 Portable Coating Device

[0091] a20 irradiation device

[0092] a21 laser

[0093] a22 laser beam

[0094] a23 Deflection Device

[0095] a24 focusing device

[0096] a25 Coupling Window

[0097] a29 control unit

[0098] A30 intake nozzle

[0099] a31 Exhaust Opening

[0100] A32 Gas Supply Channel

[0101] A33 Exhaust Channel

[0102] a34 Laminar Flow Process Airflow

[0103] H horizontal direction

[0104] V Vertical direction

[0105] 10 laser beams

[0106] 11 Surface

[0107] 12 arrows

[0108] 13 Starting Materials

[0109] 14 Metal particles

[0110] 15 Aggregates (composed of metal particles)

[0111] 16. Molten starting material

[0112] 17. Starting materials for vaporization

Claims

1. A method for mitigating the reaction of a metal condensate derived from a laser sintering or laser melting process, wherein the metal condensate is mixed with at least partially fusible inert material, the metal condensate having a particle size of 1 nm to 1000 nm, the inert material comprising particles having a particle size of 0.1 µm to 100 µm, wherein melting the inert material at least partially covers a potential ignition source.

2. The method according to claim 1, characterized in that The inert material comprises at least 10% by weight particles with a particle size of 0.1µm to 100µm.

3. The method according to claim 2, Its features are, The inert material comprises at least 50% by weight particles with a particle size of 0.1µm to 100µm.

4. The method according to claim 2, Its features are, The particle size of the inert material is less than or equal to 50µm.

5. The method according to claim 2, Its features are, The particle size of the inert material is less than or equal to 30µm.

6. The method according to claim 2, Its features are, The particle size of the inert material is less than or equal to 20µm.

7. The method according to claim 2, Its features are, The particle size of the inert material is greater than or equal to 1µm.

8. The method according to any one of claims 1 to 7, Its features are, The inert material comprises salt in the form of glass particles and / or at least one salt particle, wherein the salt has a low melting point and / or is hygroscopic or non-hygroscopic.

9. The method according to any one of claims 1 to 7, Its features are, The inert material contains less than 10% by weight of lime.

10. The method according to claim 9, Its features are, The inert material is essentially free of lime.

11. The method according to any one of claims 1 to 7, Its features are, The melting temperature of at least one fusible component of the inert material is up to 1200°C under normal pressure of 1.0 bar.

12. The method according to claim 11, Its features are, The maximum melting temperature is 800°C.

13. The method according to claim 11, Its features are, The maximum melting temperature is 600°C.

14. The method according to claim 11, Its features are, The maximum melting temperature is 450°C.

15. The method according to any one of claims 1 to 7, Its features are, At least one fusible component of the inert material has a melting temperature of at least 100°C under a normal pressure of 1.0 bar.

16. The method according to claim 15, wherein the melting temperature is at least 300°C.

17. The method according to claim 15, wherein the melting temperature is at least 500°C.

18. The method according to claim 15, wherein the melting temperature is at least 800°C.

19. Use of at least partially fusible inert material for mitigating the reaction of metal condensates from laser sintering or laser melting processes, wherein the metal condensate is mixed with the at least partially fusible inert material, the metal condensate having a particle size of 1 nm to 1000 nm, and the inert material comprising particles having a particle size of 0.1 µm to 100 µm, such that by melting the inert material, a potential ignition source can be at least partially covered.

20. A laser sintering or laser melting process, comprising the method for mitigating the reaction of metal condensates according to any one of claims 1 to 18.

21. A laser sintering or laser melting apparatus for additive manufacturing of objects, comprising at least a partially fusible inert material for mitigating the reaction of a metal condensate from a corresponding additive manufacturing process, said additive manufacturing process being the laser sintering or laser melting process of claim 20, wherein the metal condensate has a particle size of 1 nm to 1000 nm and the inert material comprises particles with a particle size of 0.1 µm to 100 µm.

22. A mixture comprising a metal condensate from a laser sintering or laser melting process according to claim 20, and at least partially fusible inert material, wherein the metal condensate has a particle size of 1 nm to 1000 nm, and the inert material comprises particles with a particle size of 0.1 µm to 100 µm.

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