Method and apparatus for manufacturing metal structures

Abstract

The present disclosure provides a method for manufacturing a metal structure (1). The method includes depositing a molten metallic material to form a first deposition region on a support (102) and depositing additional molten metallic material to form a plurality of additional deposition regions and, together with the first deposition region, form the metal structure. Each additional deposition region is positioned to at least partially contact and overlap at least one previously solidified deposition region of the first deposition region and each of the plurality of additional deposition regions when cooled until all of the deposited metallic material forming the at least one previously solidified deposition region has a temperature within a threshold temperature range. The threshold temperature range has an upper limit below the solidification temperature of the metallic material and a lower limit above 100 degrees Celsius.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing metal structures and associated apparatus for carrying out the method. [Background technology]

[0002] Metal components are used in a variety of devices, and in some cases it is desirable to have large components formed from metal.

[0003] One method used to form some components of this type involves machining the required shape of the component from a large billet of material. Initially, the billet has a substantially uniform cross-sectional shape (such as a rectangular solid of material). For many parts, the final required component occupies only a small portion of the initial volume, but the extent of each of the three lateral dimensions may extend nearly to the edge of the billet. Removing all of the excess material by machining is an energy-intensive, time-consuming process, and often produces a significant amount of waste material that must be reprocessed for reuse (requiring even more energy) or is discarded.

[0004] For some components, metal casting or forging is used to obtain a shape that closely or exactly matches the final shape of the required component. Machining processes may be used to finish the fabrication by removing small amounts of excess material. Such processes produce less excess material than machining a full billet, thus reducing the need for machining, but casting and forging require long lead times.

[0005] Additive manufacturing techniques represent a different approach to producing components by depositing material one layer at a time. However, some prior art additive manufacturing techniques can result in a columnar microstructure in the deposited metal, leading to anisotropic mechanical properties and, as a result, reduced structural performance of the component.

[0006] The present invention was devised against this background. Summary of the Invention

[0007] According to one aspect of the disclosure, a method of manufacturing a metal structure is provided, the method including depositing a molten metallic material to form a first deposition region on a support, and depositing additional molten metallic material to form a plurality of additional deposition regions to form the metal structure together with the first deposition region, each additional deposition region being disposed to at least partially contact and overlap at least one previously solidified deposition region of the first deposition region and each of the plurality of additional deposition regions when cooled until all of the deposited metallic material forming the at least one previously solidified deposition region has a temperature within a threshold temperature range. The threshold temperature range has an upper limit below a solidification temperature of the metallic material and a lower limit above 100 degrees Celsius.

[0008] The first deposition zone and the plurality of further deposition zones may be considered together to comprise a plurality of deposition zones. It will also be understood that all of the deposited metallic material forming the at least one previously solidified deposition zone may be considered to have cooled to a temperature within the threshold temperature range, even if different portions of the at least one previously solidified deposition zone are at different temperatures, so long as no portion of the at least one previously solidified deposition zone is outside the threshold temperature range.

[0009] Thus, by depositing the molten metal material in multiple deposition zones, sometimes also referred to as spots, the molten metal material forming each deposition zone can be solidified in a more controlled manner than if the molten metal material were deposited continuously. By ensuring rapid solidification of the deposition zones, the grain structure is usually less columnar and more equiaxed. Furthermore, once all of the deposited metal material forming at least one previously solidified deposition zone is at a temperature within the threshold temperature range, depositing a further deposition zone allows the previously solidified deposition zone to completely solidify, but still remain hot enough that the stresses in the deposition zone are reduced. By reducing the stresses, cracking of the metal material during cooling is also reduced or even completely eliminated. This therefore results in a metal structure with particularly good mechanical properties, such as elongation and tensile strength.

[0010] According to another aspect of the present disclosure, an apparatus for manufacturing a metal structure is provided. The apparatus is configured to perform the method described herein. Typically, the apparatus comprises a support on which the metal structure is formed, a deposition arm configured to provide a source of metal material, and a controller configured to: cause the deposition arm to deposit molten metal material to form a first deposition region on the support; and cause the deposition arm to deposit additional molten metal material to form a plurality of additional deposition regions and, together with the first deposition region, form the metal structure, each additional deposition region being positioned to at least partially contact and overlap at least one previously solidified deposition region of the first deposition region and each of the plurality of additional deposition regions when cooled until all of the deposited additional metal materials forming the at least one previously solidified deposition region have a temperature within the threshold temperature range. The threshold temperature range has an upper limit below the solidification temperature of the metal material and a lower limit above 100 degrees Celsius.

[0011] Thus, the device can be used to obtain the advantages of the method described above.

[0012] It will be appreciated that the metallic material may be virtually any metallic material having a solidification temperature above 100 degrees Celsius. Typically, the metallic material is one in which an undesirable microstructure forms when the metal is allowed to cool slowly from the molten deposition temperature. The metallic material may be an alloy. The metallic material may include titanium. The metallic material may be a titanium alloy. The titanium alloy may include aluminum. The titanium alloy may include vanadium. The titanium alloy may be partially present in an alpha phase. The titanium alloy may be partially present in a beta phase. The titanium alloy may be an alpha-beta titanium alloy. The titanium alloy may be Ti-6Al-4V. The metallic material may be an iron alloy, such as steel. The metallic material may be a nickel alloy.

[0013] The upper limit of the threshold temperature range may be greater than 20 degrees below the freezing temperature. The upper limit of the threshold temperature range may be greater than 50 degrees below the freezing temperature. The upper limit of the threshold temperature range may be greater than 100 degrees below the freezing temperature. The upper limit may be greater than 500 degrees below the freezing temperature. The upper limit may be greater than 200 degrees below the freezing temperature. The upper limit of the threshold temperature range may be less than 1,500 degrees below the freezing temperature. The upper limit of the threshold temperature range may be less than 1,000 degrees below the freezing temperature. If the metallic material is a titanium alloy, the upper limit may be greater than 1,500 degrees Celsius. If the metallic material is a titanium alloy, the upper limit may be less than 1,600 degrees Celsius.

[0014] The lower limit of the threshold temperature range may be greater than 500 degrees below the solidification temperature. The lower limit of the threshold temperature range may be greater than 1,000 degrees below the solidification temperature. The lower limit of the threshold temperature range may be greater than 150 degrees Celsius. The lower limit of the threshold temperature range may be greater than 200 degrees Celsius. The lower limit of the threshold temperature range may be less than 1,000 degrees Celsius. The lower limit of the threshold temperature range may be less than 600 degrees Celsius. The lower limit of the threshold temperature range may be less than 500 degrees Celsius. Thus, at least a portion of the at least one previously solidified deposition region may not be allowed to cool significantly before the further molten metallic material is deposited to form a respective further deposition region at least partially contacting and overlapping the at least one previously solidified deposition region. This in turn promotes the formation of stronger bonds between the contacting deposition regions each having a temperature close to the solidification temperature. In particular, the surface tension of metallic materials remains relatively low at temperatures within 500 degrees Celsius of the solidification temperature, thereby allowing contacting deposition regions to bond without significant unevenness in the bond. Furthermore, the deposition of additional molten metallic material forming an additional deposition region when at least one previously solidified deposition region cools excessively may result in the formation of fusion defects in the metallic structure, thereby reducing the strength of the bond between the deposition regions. Thus, the lower end of the threshold temperature range may be high enough to reduce or even substantially prevent the formation of fusion defects between the deposition regions.

[0015] The method may include determining whether a temperature of the at least one previously solidified deposition region is below a first threshold temperature. The controller may be configured to determine whether a temperature of the at least one previously solidified deposition region is below the first threshold temperature. Deposition of the additional molten metallic material to form each additional deposition region may depend on the temperature of the at least one previously solidified deposition region being below the first threshold temperature. The first threshold temperature may be less than or equal to an upper limit of a threshold temperature range. The first threshold temperature may be substantially equal to an upper limit of the threshold temperature range.

[0016] The molten metallic material may be deposited by welding. In other words, the deposition arm may be a welding arm. The welding may be short circuit transfer welding. The welding may be cold metal transfer welding.

[0017] It will be understood that welding encompasses virtually any process in which a portion of a metallic material source is heated until it melts for deposition to form a metallic structure. The portion of metallic material may be heated by virtually any known heating method used in a welding process. Although welding is sometimes used to join two components together, with the molten metallic material forming a structural connection between the two components, this is not typically the case in the methods and apparatus described herein, where it is the molten metallic material itself that is used to form the metallic structure. However, it will be understood that this is still considered to be a welding process.

[0018] It will be further appreciated that the molten metallic material may be deposited to form the deposition area continuously, in one continuous stream, or as a number of separate molten droplets.

[0019] Depositing the further molten metal material to form the plurality of further deposition regions may include depositing a first volume of the further molten metal material to form a first subset of the plurality of further deposition regions to provide a first portion (e.g., a layer) of the metal structure, and depositing a second volume of the further molten metal material to form a second subset of the plurality of further deposition regions to provide a second portion (e.g., a layer) of the metal structure.

[0020] The controller may be configured to cause the deposition arm to deposit a first volume of the further molten metal material to form a first subset of the plurality of further deposition regions to provide a first portion (e.g., a layer) of the metal structure, and to deposit a second volume of the further molten metal material to form a second subset of the plurality of further deposition regions to provide a second portion (e.g., a layer) of the metal structure.

[0021] Thus, the metal structure can be made in several layers, each layer being formed from a number of further deposition regions.

[0022] The method may further include depositing one or more further volumes of the further molten metal material to form one or more further subsets of a plurality of further deposition regions to provide one or more further respective portions (e.g., one or more further respective layers) of the metal structure, each of the further subsets being deposited on a previous subset to provide a previous respective portion (e.g., a previous respective layer) of the metal structure. Similarly, the controller may be configured to cause the deposition arm to deposit one or more further volumes of the further molten metal material to form one or more further subsets of the plurality of further deposition regions to provide one or more further respective portions (e.g., one or more further respective layers) of the metal structure, each of the further subsets being deposited on a previous subset to provide a previous respective portion (e.g., a previous respective layer) of the metal structure.

[0023] Each of a first subset of the plurality of further deposition regions may be deposited to provide the first portion before any of a second subset of the plurality of further deposition regions is deposited on the first portion. Thus, the metal structure is formed layer by layer, with each layer being completely formed in its entirety before the next layer is formed.

[0024] The second portion may be provided on the first portion. During depositing a second volume of the further molten metallic material to form a second subset of the plurality of further deposition regions to provide the second portion of the metal structure, a first subset temperature of a surface of each of the first subset of the plurality of further deposition regions at which the further molten metallic material for forming the second subset of the plurality of further deposition regions is deposited may be below a temperature at which environmental contamination occurs. During depositing a second volume of the further molten metallic material to form the second subset of the plurality of further deposition regions to provide the second portion of the metal structure, a second subset temperature of at least one surface of the second subset of the plurality of further deposition regions that will be contacted by a deposition region already deposited and currently being deposited within the plurality of further deposition regions may be above a temperature at which environmental contamination occurs. Thus, previously deposited portions of the metal structure can be allowed to cool to a temperature where environmental contamination is significantly reduced or even entirely prevented, but remain pre-heated to obtain the attendant mechanical advantage during fabrication, while deposition areas that will form the current portion of the metal structure and be contacted by the current deposition can remain at a higher temperature, ensuring stronger bonds are provided between such deposition areas over the current portion of the metal structure.

[0025] While depositing a second volume of further molten metal material to form a second subset of the plurality of further deposition regions to provide a second portion of the metal structure, a second subset temperature of a surface of the second subset of the plurality of further deposition regions, or of each surface of the second subset, that will be contacted by a deposition region already deposited and currently being deposited within the plurality of further deposition regions may be higher than a temperature at which environmental contamination occurs.

[0026] The first subset temperatures may be less than 500 degrees Celsius. The first subset temperatures may be less than 420 degrees Celsius. The first subset temperatures may be less than 400 degrees Celsius. The first subset temperatures may be substantially equal to a lower limit of a threshold temperature range.

[0027] The second subset of temperatures may be greater than 500 degrees Celsius. The second subset of temperatures may be greater than 1,000 degrees Celsius. The second subset of temperatures may be greater than 1,300 degrees Celsius. The second subset of temperatures may be substantially equal to an upper limit of a threshold temperature range.

[0028] It will be appreciated that virtually any deposition pattern of deposition areas for each layer may be used.

[0029] The method may include polishing one or more of the plurality of deposition regions after deposition.The method may include at least partially polishing each of the plurality of deposition regions after deposition of each respective deposition region.

[0030] The method may include polishing an exposed surface of the first portion after a first subset of the plurality of further deposition regions has been deposited to provide the first portion and before depositing any of a second subset of the plurality of further deposition regions onto the exposed surface of the first portion.

[0031] The apparatus may include an abrasive tool movable relative to the support. The controller may be configured to cause the abrasive tool to abrade one or more solidified deposition regions after deposition. The controller may be configured to cause the abrasive tool to abrade the first portion after a first subset of the plurality of deposition regions are deposited to form the first portion and before any of a second subset of the plurality of deposition regions are deposited on the first portion.

[0032] Thus, dirt, soot, oxide, sputter, or topographical irregularities can be removed from one layer before depositing the next layer.

[0033] The abrasive may comprise brushing. The abrasive may comprise grinding. The abrasive may comprise cleaning. The abrasive tool may comprise a brush. The abrasive tool may comprise a grinding tool.

[0034] At least one of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 2,500 square millimeters. At least 50 percent of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 2,500 square millimeters each. Each of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 2,500 square millimeters each.

[0035] At least one of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,500 square millimeters. At least 50 percent of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,500 square millimeters each. Each of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,500 square millimeters each.

[0036] At least one of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,000 square millimeters. At least 50 percent of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,000 square millimeters each. Each of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 1,000 square millimeters each.

[0037] At least one of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 500 square millimeters. At least 50 percent of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 500 square millimeters each. Each of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​less than 500 square millimeters each.

[0038] The foregoing surface areas herein will be understood to be the surface area of ​​the deposition region exposed immediately after solidification of the molten metallic material and prior to any covering of the deposition region as a result of further deposition of the deposition region in the same layer or any overlying layer.

[0039] At least one of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​greater than 10 square millimeters. At least 50 percent of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​greater than 10 square millimeters each. Each of the plurality of deposition regions may be in the form of a coagulation spot having a surface area of ​​greater than 10 square millimeters each.

[0040] It will be understood that the term "square millimeters" (such as "500 square millimeters") refers to an area consisting of the specified number of square millimeters (1 mm x 1 mm).

[0041] Thus, at least a portion of the deposition region is sized to be sufficiently small so that the molten metallic material forming the deposition region cools and solidifies in a controlled manner, thereby reducing, or even almost completely preventing, the columnar microstructure, which may result in particularly good mechanical properties for the metallic structure.

[0042] The surface area of ​​the deposition area may be selected to be small enough so that the molten metal material solidifies in less than 1 second. The surface area of ​​the deposition area may be selected to be small enough so that the molten metal material solidifies in less than 0.5 seconds. The surface area of ​​the deposition area may be selected to be small enough so that the molten metal material solidifies in less than 0.25 seconds. Thus, when the molten metal material is deposited using short-circuit transfer welding, the time between the end of the first welding arc used to deposit the first deposition area and the start of the second welding arc used to deposit the second deposition area may approximately correspond to the minimum non-welding time between two successive welding arcs. In other words, the deposition area may be small enough to ensure that the molten metal material solidifies after deposition of the first deposition area before it is possible to start deposition of further molten metal material to form the second deposition area.

[0043] Each of the multiple deposition regions may have substantially the same size.

[0044] The solidification spot may define a contour with a length to width aspect ratio in the plane of the support of less than 2. It will be appreciated that particularly elongated shapes may be considered to have a significant length to width aspect ratio when the length is the largest dimension (e.g., much greater than 2), but a very small aspect ratio when the width is the largest dimension (e.g., much less than 0.5). Thus, the length to width aspect ratio in the plane of the support region may be greater than 0.5. In other words, the solidification spot may define a contour whose length and width do not differ by more than a factor of two, or vice versa. In some instances, the solidification spot may define a substantially circular contour. It has been found that having an aspect ratio relatively close to 1 ensures a significant reduction in the formation of columnar microstructures compared to the deposition of elongated portions of metal material (having aspect ratios significantly away from 1). Thus, reducing the presence of columnar crystallites (i.e., columnar grains) in the microstructure ensures improved mechanical properties of the resulting metal structure.

[0045] The method may include heating to a preheat temperature. The support may be heated to the preheat temperature. At least an outer surface of the deposition area where the further deposition area will be formed may be heated to the preheat temperature. The method may include maintaining a temperature at the preheat temperature during deposition of the plurality of deposition areas on the support or the outer surface of the deposition area. The apparatus may include a heater. The heater may be configured to heat the support. The heater may be configured to heat the outer surface of the deposition area where the further deposition area will be formed. The controller may be configured to cause the heater to heat to the preheat temperature. The controller may be configured to cause the heater to maintain the temperature at the preheat temperature. Thus, the interfacial tension of the plurality of deposition areas forming the metal structure may be relaxed, thereby reducing residual stresses in the metal structure during fabrication. As a result, the risk of cracks in the deposition area during solidification is reduced. It will be appreciated that the control of the heating may be manual, semi-automatic, or fully automatic and may be achieved using substantially any conventional heating technique, including substantially any heating control system, such as a proportional integral derivative (PID) control system.

[0046] The preheat temperature may be greater than 100 degrees Celsius. The preheat temperature may be less than the solidification temperature of the metallic material. The preheat temperature may be greater than 150 degrees Celsius. The preheat temperature may be less than 1,000 degrees Celsius. The preheat temperature may be less than 500 degrees Celsius.

[0047] Depositing the molten metallic material to form a plurality of deposition regions to form a metallic structure may include flooding an area including each deposition region with an inert gas during deposition, thus reducing the ability of the deposition regions to oxidize after deposition.

[0048] The controller may be configured to cause the apparatus to flood an area including each deposition zone with an inert gas while depositing the molten metallic material to form the multiple deposition zones.

[0049] The inert gas may be a mixture of gases. The inert gas may include helium. The inert gas may include argon. The apparatus may include a shielding member arranged to partially retain the inert gas in an area including the deposition region while providing cooling.

[0050] Depositing the molten metallic material to form the multiple deposition regions may include inducing vibration (e.g., mechanical vibration) in the multiple deposition regions such that any gas bubbles in the deposition regions may shrink and / or be removed from the deposition regions prior to solidification.

[0051] The controller may be configured to cause the apparatus to vibrate (eg, mechanically vibrate) the multiple deposition regions during deposition of the molten metallic material onto the support.

[0052] The vibration may continue for at least a first period of time after deposition of each deposition region. The vibration may continue for at least 1 second after deposition of each deposition region.

[0053] The method may further include machining the metal structure, such that the final shape of the metal component may be formed by machining the metal structure to remove remaining excess material, the machining of the metal structure may be performed after the deposition of the molten metal material to form the metal structure has formed a plurality of deposition regions on the support.

[0054] The apparatus may further comprise a machining tool configured to machine the metal structure, and the controller may be configured to cause the machining tool to machine the metal structure after the plurality of deposition regions are formed on the support by deposition of the molten metallic material to form the metal structure.

[0055] In some examples, the metal structure may be machined during deposition of the multiple deposition regions on the support. For example, the method may include depositing a first subset of the multiple deposition regions on the support, depositing a second subset of the multiple deposition regions on the support subsequent to depositing the first subset of the multiple deposition regions, and machining the metal structure after the first subset of the multiple deposition regions is deposited and before any of the second subset of the multiple deposition regions is deposited. The metal structure may be machined multiple times between when a first deposition region of the multiple deposition regions is deposited and when a last deposition region of the multiple deposition regions is deposited.

[0056] The deposition regions within a given layer may be arranged in a predetermined pattern, for example, the predetermined pattern may be either a square, a hexagon, or any other suitable pattern.

[0057] The multiple deposition regions may be deposited in substantially any order, in other words, the deposition region immediately prior to being deposited need not be the same as the deposition region that the current deposition region will contact.

[0058] The weave pattern during deposition of each deposition zone may be substantially any weave pattern, for example, triangular, trapezoidal, rectangular, circular, spiral, or any other suitable pattern. The weave pattern may be the same for each deposition zone. In some instances, there may be no weave pattern, and the deposition zones may be deposited without any further lateral movement of the deposition arm relative to the support during deposition of the deposition zone.

[0059] According to a further aspect of the invention, there is provided a metal component manufactured according to the method disclosed herein or using the apparatus disclosed herein. Thus, a final component can be produced with particularly good mechanical properties compared to machining the metal component from a rectangular billet of metal material, and furthermore, the metal component can be manufactured by a process that does not generate a large amount of waste material. It will be appreciated that upon inspection of the microstructure of the metal component, it will become apparent that the metal component is formed by depositing molten metal material on a support to form a plurality of deposition zones, adjacent deposition zones being deposited on adjacent deposition zones only when the adjacent deposition zones have been cooled such that their temperatures are within a threshold temperature range. If the metal component were instead cast or formed using any other manufacturing technique, the microstructure would look different.

[0060] According to yet another aspect of the present invention, there is provided a computer-readable storage medium having instructions stored thereon that, when executed by one or more processors of a controller as described herein, are configured to cause an apparatus to perform one or more, or all, of the steps of the methods described herein.

[0061] The controller may comprise one or more processors and a memory configured to store instructions that, when executed by the one or more processors, cause the device to execute the commands of the controller. The memory may be a non-transitory computer-readable memory. The memory may have instructions stored on it. The invention extends to a non-transitory computer-readable medium (e.g., a memory) having instructions stored thereon for controlling the device described herein. The memory may be a solid-state memory. The controller may be provided within a single device. In other examples, the controller may be distributed having multiple processors. A first processor may be separate from a second processor in a distributed manner.

[0062] The controller may be configured to perform substantially any of the methods and / or steps described herein, except where not essentially compatible.

[0063] Exemplary embodiments of the present invention will now be described with reference to the following drawings. [Brief description of the drawings]

[0064] [Figure 1] 1 illustrates an example of an apparatus for manufacturing a metal structure according to an embodiment of the present invention. [Diagram 2] 1 illustrates the microstructure of a metal structure formed without using the deposition techniques described herein. [Diagram 3] 1 illustrates the microstructure of a metal structure formed using a deposition technique according to one embodiment of the present invention. [Figure 4] 1 illustrates a layer view of a metal structure during a manufacturing process according to one embodiment of the present invention. [Diagram 5] 2 is a flow chart illustrating steps of a method according to one embodiment of the present invention. [Figure 6] 1 illustrates generally an apparatus including a controller, according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] FIG. 1 shows an example of an apparatus for manufacturing a metal structure according to an embodiment of the present invention. The apparatus 100 comprises a support area 102, sometimes simply referred to as support 102. The support area 102 is in the form of a platform 102 on which the metal structure 1 can be formed. Typically, the support area 102 is formed from the same material as the metal structure 1 or from another material to which the metal structure 1 can be easily bonded. The metal structure 1 can be considered as an additively manufactured part 1, as will be further explained below. The apparatus 100 further comprises a deposition arm 4 in the form of a robot arm 4, comprising a welding tool 2 in the form of a welding torch 2. The welding tool 2 is supplied with a source of metal material for depositing on the support area 102 using the welding tool 2 to form the metal structure 1. In this example, the welding tool 2 is provided with a trailing shield 3, which also includes an integrated camera and other sensors, in particular to monitor the deposition of the metal material from the welding tool 2. The metal material is provided to the deposition arm 4 by a wire feed mechanism 8. It will be appreciated that the deposition arm 4, and in particular the welding tool 2 of the deposition arm 4, may be supplied with power for operating the welding tool 2 from a welding power source, which in this example is integrated with the wire feed mechanism 8. The deposition arm 4 is typically movable to change the position of the welding tool 2 relative to the metal structure 1. The apparatus 100 further comprises a preheat source 6 arranged to heat the support area 102 during operation, thereby also heating the metal structure 1 to a preheat temperature. In this example, the apparatus 100 further comprises an external positioner 5 for moving the support area 102, and thus also the metal structure 1, thereby allowing the movement and / or reorientation of the metal structure 1 relative to the welding tool 2 during operation. In this example, the external positioner 5 also includes an exciter and transducer operable to induce vibrations of the metal structure 1 during manufacture, which are also used for ultrasonic testing of the metal structure 1 during manufacture. The apparatus 100 also includes a deposition arm 4 containing the welding tool 2, a preheat source 6, an external positioner 5, and a controller 7 for controlling a wire feed mechanism 8. The metallic material in this example is an alloy of titanium, Ti-6Al-4V.

[0066] FIG. 2 illustrates the microstructure of a metal structure formed without the use of the deposition techniques described herein. Specifically, the metal structure shown in FIG. 2 is formed using a metal deposition technique that deposits a metal material (in this case, titanium alloy Ti-6Al-4V) in elongated sections at a time. The resulting microstructure 200 is characterized by the formation of columnar crystallites (grains) oriented along the build direction. It has been found that this type of columnar microstructure results in anisotropic mechanical properties and therefore reduced structural performance of the resulting metal component.

[0067] Figure 3 illustrates the microstructure of a metal structure formed using a deposition technique according to one embodiment of the present invention. In contrast to the microstructure of Figure 2, the deposited metal material shown in Figure 3 is deposited in multiple separate deposition zones, each of which is cooled to within a threshold temperature range having an upper limit below the solidification temperature of the metal before depositing further metal material to form another deposition zone in contact with the previous deposition zone. As a result, the formation of columnar crystallites (grains) is significantly reduced, which reduces the anisotropic variation of mechanical properties, thus avoiding a significant degradation of the structural performance of the resulting metal component.

[0068] Figure 4 illustrates a diagram of a layer of a metal structure during a manufacturing process according to an embodiment of the present invention. The layer 400 is formed from a number of deposition regions 402, 404 according to a method further described below with reference to Figure 5. As can be seen, a first deposition region 402 is deposited and allowed to solidify, and a second deposition region 404 is deposited in contact with and overlapping the first deposition region 402. In this manner, the entire layer 400 can be built up. In this example, the layer 400 is also brushed to remove soot, oxide, sputters, and morphological irregularities, ready for depositing the next layer thereon.

[0069] Figure 5 is a flow chart illustrating steps of a method according to an embodiment of the present invention. The method 500 is also described with reference to the apparatus shown in Figure 1 and previously described herein. The method 500 is for manufacturing a metal structure 1. Briefly, the method 500 comprises depositing 510 a molten metallic material to form a first deposition zone, and depositing 520 further molten metallic material to form a plurality of further deposition zones each in contact with a respective previously solidified deposition zone when the temperature of the previously solidified deposition zone falls below an upper limit of a threshold temperature range.

[0070] Specifically, the method 500 includes depositing 510, 520 molten metallic material to form a plurality of deposition regions on the support region 102 to form the metallic structure 1. As shown in FIG. 5, depositing the molten metallic material to form a plurality of deposition regions includes depositing 510 the molten metallic material on the support region 102 to form a first deposition region, and then depositing 520 further molten metallic material to form a plurality of further deposition regions that together with the first deposition region form the metallic structure. Each of the further deposition regions is positioned to at least partially contact and overlap a respective at least one previously solidified deposition region when cooled until all of the deposited metallic material forming the at least one previously solidified deposited region has a temperature within the threshold temperature range. The threshold temperature range has an upper limit below the solidification temperature of the metallic material and a lower limit above 100 degrees Celsius.

[0071] There are typically hundreds, if not thousands, and perhaps tens of thousands or more of deposition zones formed by depositing molten metallic material to form metallic structures. Each of these (except the first) is deposited in at least partial contact with and overlapping with at least one of the other deposition zones of the previously solidified deposition zones once the temperatures of all of the molten metallic material forming each of the other deposition zones are below the upper limit of the threshold temperature range. In this way, metallic structures can be formed by overlapping the deposition zones to build the required structure, while the metallic material is deposited in a small deposition zone, allowing it to solidify rapidly and cool below the upper limit of the threshold temperature range.

[0072] The method further includes pre-heating the support area 102 (and thus the metal structure 1 being fabricated) using a pre-heat source 6 to ensure that the temperature of the metal structure 1 does not drop too low, which may also adversely affect the structural properties of the fabricated metal structure 1. In this example, the pre-heat source 6 pre-heats the support area 102 to about 200 degrees Celsius.

[0073] The process in which molten metallic material is deposited to form a plurality of deposition zones on the support area 102 is commonly referred to as welding, in which a source of metallic material (titanium alloy) is fed to the welding tool 2 of the deposition arm 4 using a wire feed mechanism 8. The titanium alloy is heated at the welding tool 2 until it melts, at which point the titanium alloy is deposited as one or more droplets to form a deposition zone on the support area 102 (or a layer of deposition zones already deposited on the support area 102). In this example, the particular welding form is cold metal transfer welding, specifically short circuit transfer welding, which also promotes the formation of smaller grain sizes because overheating of the metallic material is avoided. Nevertheless, it will be understood that substantially any method of forming molten metallic material for deposition, such as any other welding technique, can be used to achieve at least some of the advantages described herein.

[0074] The deposition regions in this example are sized to provide substantially circular spots having diameters between 4 mm and 20 mm, e.g., 10 mm. The degree of overlap between adjacent deposition regions and post-flow times are arranged to maintain the desired interpass temperatures and also allow for a more isotropic residual stress distribution within the construct.

[0075] It will be understood that substantially any weave pattern and / or substantially any deposition zone stacking pattern and / or substantially any deposition zone stacking sequence can be used to deposit the molten metal material to form the multiple deposition zones, as long as the overlapping deposition zones in contact with the newly deposited deposition zones have already solidified and cooled below the upper limit of the threshold temperature range. To deposit the molten metal material to form the deposition zones in the support zone 102, one or both of the deposition arm 4 and the external positioner 5 move relative to each other to change the position in the support zone 102 where each deposition zone is formed by the deposition of the molten metal material. In situations where the same relative position of the deposition arm 4 to the support zone 102 can be achieved by moving the deposition arm 4, or the external positioner 5, or a combination of the deposition arm 4 and the external positioner 5, it is usually preferred that the support zone 102 and the deposition arm 4 are oriented such that gravity acts on the metal structure 1 to support the production of the metal structure 1, bearing in mind that the molten metal material is deposited such that it falls from the deposition arm 4 in the direction of gravity.

[0076] It will also be appreciated that the interpass temperature may be controlled by virtually any known method, for example, using a subsystem including a suitable heating source (e.g., flame, induction heating, or laser) receiving feedback from a temperature measurement device (e.g., thermocouple, infrared camera, etc.) Properly set post-flow times are also relevant to interpass temperature control.

[0077] During welding, a trailing shield 3 is used to deliver a suitable inert gas (e.g., argon, helium, or any mixture of gases) to the welded area to reduce or even substantially prevent oxidation by excluding oxygen (or any other contaminating gas) from the welded area. In particular, the use of a trailing shield ensures that the contaminating gas cannot react with the deposited metallic material until the temperature is low enough that no spontaneous reaction occurs, typically below 420 degrees Celsius for titanium alloy Ti-6Al-4V.

[0078] During and for a predetermined period of time after the deposition of the molten metal material to form each deposition zone, the exciter of the external positioner 5 is operated to apply multi-directional mechanical vibrations to the metal structure. The purpose of the vibrations is twofold: (1) to achieve polycrystalline grain refinement and reduced porosity by degassing the weld pool, and (2) to relieve residual stresses. Vibration detectors (transducers) are used to measure the parameters of the vibrations. The frequency and intensity of the vibrations are optimized for each part using one of the following methods: (1) rule of thumb: a frequency sweep is performed using a standard part, a vibration spectrum of the part is obtained, from the spectrum obtained the optimal vibration frequency and intensity are selected and applied during deposition, (2) numerical simulation, (3) analytical calculation. A shock absorber (not labeled in FIG. 1) is used to mechanically decouple the metal structure 1 from the external positioner 5.

[0079] Furthermore, the mechanical properties of the metal structure 1 can be estimated and potential defects can be detected based on the vibration spectrum (acoustic quality monitoring). If significant deviations from the determined optimal vibration properties are detected, indicating defects in the deposited part, the further deposition of molten metal material to form further deposited areas can be interrupted, while the defects are evaluated and, if necessary, the metal structure 1 is repaired. Alternatively, the additive manufacturing process can also be stopped completely if the identified defects cannot be corrected.

[0080] The methods described herein can also include applying multi-directional ultrasonic vibrations to control the microstructure of the construct. The frequency of the vibrations is optimized for the specific geometry. The ultrasonic vibrations can be delivered by a suitable sonotrode or induced using an electromagnetic acoustic transducer (EMAT).

[0081] After deposition of a complete layer of metal structure 1 formed by molten metal material and deposited to form a number of solidified deposition areas, the completed layer is subjected to a mechanical treatment such as brushing and / or grinding, in this way morphological irregularities, soot, oxides, sputters or any other undesirable surface features can be removed before starting the deposition of the next layer of metal structure 1.

[0082] During deposition, the deposition process can be remotely monitored, either manually or automatically, for example by using sensors and cameras provided as part of the trailing shield 3.

[0083] After the deposition of the metal structure 1 is completed, further manufacturing steps are typically performed. In this example, further heat treatment of the metal structure 1 is performed to achieve the desired mechanical properties of the metal structure 1. Furthermore, the metal structure 1 is typically further machined to remove any excess material to obtain a final shape that matches the desired shape of the finished metal component.

[0084] Although only a single welding tool 2 is shown in FIG. 1, it will be appreciated that in other examples multiple independently controlled welding tools and / or multiple wire feeding mechanisms may be used.

[0085] The apparatus may also include an in-process non-destructive testing subsystem for detecting virtually any known type of defect.

[0086] The apparatus may be configured to check the geometric metrology of the metal structure 1 during deposition (such as after deposition of a first layer) and thereby monitor the geometric dimensions. The deposition of subsequent layers can be controlled accordingly, for example to ensure the desired geometric metrology of the next layer.

[0087] FIG. 6 illustrates a schematic of an apparatus including a controller, according to an embodiment of the present invention. The apparatus 600 can be considered to be the apparatus 100 of FIG. 1 and includes a controller 610 for controlling one or more electronic components 650 of the apparatus 600. The one or more electronic components include a deposition arm 4, a wire feed mechanism 8, a preheat source 6, an external positioner 5, and a trailing shield 5 (including any integrated sensors such as a camera). In this example, the controller 610 is configured to control the deposition arm 4, and specifically the welding tool 2 of the deposition arm 4 via a controller 7, although it will be understood that in other examples the controller 7 may be considered to be part of the controller 610. The controller exchanges signals (such as control signals and sensor data signals) via a data communication path 625. It will be understood that the data communication path may include wired and / or wireless portions of the data communication path. The controller 610 comprises one or more processors 620 and a non-transitory computer-readable memory 630. The computer-readable memory 630 stores instructions that, when executed by the one or more processors 620, cause the apparatus 600 to perform the methods described herein.

[0088] In summary, a method (1) for manufacturing a metal structure is provided. The method includes depositing a molten metal material on a support (102) to form a first deposition region, and depositing further molten metal material to form a plurality of further deposition regions and, together with the first deposition region, form the metal structure. Each further deposition region is positioned to at least partially contact and overlap at least one previously solidified deposition region of the first deposition region and each of the plurality of further deposition regions when cooled until all of the deposited metal material forming the at least one previously solidified deposition region has a temperature within a threshold temperature range. The threshold temperature range has an upper limit below the solidification temperature of the metal material and a lower limit above 100 degrees Celsius.

[0089] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations thereof mean "including, but not limited to," and are not intended to, and do not, exclude other elements, integers, or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context dictates otherwise. In particular, where the indefinite article is used, the specification should be understood as contemplating the plural as well as the singular, unless the context dictates otherwise.

[0090] It should be understood that features, integers, properties, or groups described in connection with a particular aspect, embodiment, or example of the invention are applicable to any other aspect, embodiment, or example described herein, unless inconsistent therewith. All features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel, or any novel combination of features disclosed in this specification (including any accompanying claims, abstract, and drawings), or any novel, or any novel combination of steps of any method or process so disclosed.

Claims

1. A method for manufacturing a metal structure, A step of depositing molten metal material to form a first deposit region on a support, The process involves depositing further molten metal material to form multiple further deposit regions, thereby forming the metal structure together with the first deposit region. Each of the further deposition regions is positioned such that, when all of the deposited metallic material forming at least one previously solidified deposition region is cooled to a threshold temperature range, it is at least partially in contact with and overlaps with the corresponding at least one previously solidified deposition region and each of the plurality of further deposition regions of the first deposition region. The threshold temperature range has an upper limit lower than the solidification temperature of the metal material and a lower limit higher than 100°C. The molten metal material is deposited by welding, The step of depositing the molten metal material to form the plurality of deposit regions, including the first deposit region and the plurality of further deposit regions, includes the step of flooding the region containing each corresponding deposit region with an inert gas during the deposit process. At least one of the plurality of deposition regions, including the first deposition region and the plurality of further deposition regions, is a solidification spot having a surface area of ​​less than 1000 mm². The solidification spot has an aspect ratio of length to width in the plane of the support that is less than 2. method.

2. An apparatus for manufacturing a metal structure, A support on which the metal structure is formed, A deposition arm configured to be supplied with a metallic material source, control device Equipped with, The control device is The configuration is such that the metal structure is formed together with the first deposition region by depositing further molten metal material on the deposition arm to form a plurality of further deposition regions. Each of the further deposition regions is positioned such that, when all of the deposited metallic material forming at least one previously solidified deposition region is cooled to a threshold temperature range, it is at least partially in contact with and overlaps with the corresponding at least one previously solidified deposition region and each of the plurality of further deposition regions of the first deposition region. The threshold temperature range has an upper limit lower than the solidification temperature of the metal material and a lower limit higher than 100°C. The aforementioned deposition arm is a welding arm, The control device is configured to form the plurality of deposition regions by flooding the region containing each corresponding deposition region with an inert gas during the deposition of the molten metal material. At least one of the plurality of deposition regions, including the first deposition region and the plurality of further deposition regions, is a solidification spot having a surface area of ​​less than 1000 mm². The solidification spot has an aspect ratio of length to width in the plane of the support that is less than 2. Device.

3. The method according to claim 1, wherein the metal material is a titanium alloy.

4. The method according to claim 1, wherein the lower limit is greater than 150 degrees Celsius.

5. The method according to claim 1, wherein the upper limit is a temperature greater than 200 degrees below the solidification temperature of the metal material.

6. The method according to claim 1, wherein the metal structure is manufactured solely from the deposited molten metal material.

7. The method according to claim 1, wherein the molten metal material is deposited by short-circuit transfer welding.

8. The step of depositing further molten metal material to form the plurality of further deposit regions includes the step of depositing a first volume of the further molten metal material to form a first subset of the plurality of further deposit regions, thereby providing a first part of the metal structure, and the step of depositing a second volume of the further molten metal material to form a second subset of the plurality of further deposit regions, thereby providing a second part of the metal structure. Optionally, each of the first subset of the plurality of further deposit regions is deposited to provide a first portion before any of the second subset of the plurality of further deposit regions is deposited to provide a second portion. The method according to claim 1, optionally comprising the step of polishing the exposed surface of the first portion after the first subset of the plurality of further deposition regions has been deposited to provide the first portion, and before depositing any of the second subset of the plurality of further deposition regions onto the exposed surface of the first portion.

9. The second portion is provided in the first portion and, during the deposition of the second volume of the further molten metal material to form the second subset of the plurality of further deposition regions for providing the second portion of the metal structure, The first subset temperature of each surface of the first subset of the plurality of further deposition regions, to which the further molten metal material is deposited to form the second subset of the plurality of further deposition regions, is below a temperature at which environmental contamination occurs (e.g., below 500 degrees Celsius). The method according to claim 8, wherein the second subset temperature of at least one surface of the second subset of already deposited further deposit regions, which will be in contact with the deposit region currently being deposited within the plurality of further deposit regions, is above a temperature at which environmental pollution occurs (e.g., above 500 degrees Celsius, such as above 1300 degrees Celsius).

10. The method according to claim 1, wherein at least one of the plurality of deposition regions, including the first deposition region and the plurality of further deposition regions, is in the form of a solidified spot having a surface area of ​​less than 500 square millimeters.

11. The method according to claim 1, wherein at least one of the plurality of deposition regions, including the first deposition region and the plurality of further deposition regions, is in the form of a solidified spot having a surface area of ​​more than 10 square millimeters.

12. The method according to claim 1, wherein at least 50% of the plurality of deposition areas are solidification spots with a surface area of ​​less than 1,000 mm².

13. The method according to claim 1, comprising heating the outer surface of the support or the deposition region on which further deposition regions are formed to a preheating temperature, and maintaining the temperature of the outer surface of the support or the deposition region at the preheating temperature during the deposition of the plurality of deposition regions, including the first deposition region and the plurality of further deposition regions, on the outer surface of the support or the deposition region.

14. The method according to claim 1, wherein depositing the molten metal material and the molten metal material to form the plurality of deposit regions includes causing mechanical vibration of the plurality of deposit regions.

15. The method according to claim 14, wherein the mechanical vibration continues for at least a first period after deposition in each deposition area.

16. The method according to claim 1, further comprising machining the metal structure.

17. A metal component manufactured according to the method described in any one of claims 1 or 3 to 16.

18. A computer-readable storage medium on which instructions are stored, wherein the instructions, when executed by one or more processors of the controller described in claim 2, are configured to cause the device to carry out the method described in any one of claims 1 or 3 to 16.

19. The apparatus according to claim 2, wherein the metal material is a titanium alloy.

20. The apparatus according to claim 2, wherein the lower limit is higher than 150°C.

21. The apparatus according to claim 2, wherein the upper limit is higher than 200°C, which is lower than the solidification temperature of the metal material.

22. The apparatus according to claim 2, wherein the metal structure is manufactured solely from the deposited metal material.

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