Abstract
According to the invention, a method is provided for additively manufacturing a component, in particular a metallic component, said method having the steps of: ? providing at least one substrate (I), in particular a substrate plate, the substrate being formed from one or more metallic substrate materials which has a martensite start temperature (Ms) below 140? C., the martensite start temperature (Ms) being below the manufacturing temperature (Tp); ? building the component on a building surface (5) of the substrate (I) by layered application of at least one material at a manufacturing temperature (Tp) to form a component-substrate composite (7) over a boundary surface (6); ? after building of the component (3) is complete, cooling at least the substrate (I) in the component-substrate composite (7) to a temperature below the martensite start temperature (Ms), wherein, as a result of martensitic transformation and the associated volume expansion of the metallic substrate material, a transformation stress is induced in the substrate (I), at least in the boundary surface (6) to the component (3); and ? separating the component (3) from the substrate (I). The invention further relates to a substrate (I) for use in such a method.
Claims
1. A method for the additive manufacturing of a component (3) at a manufacturing temperature T.sub.F, having the steps of providing at least one substrate (1), in particular a substrate plate, wherein the substrate (1) is formed or will be formed from one or several metallic substrate materials, which is a low transformation temperature (LTT) alloy, wherein the LTT alloy has a martensite start temperature Ms of below 140? C., which is calculated according to the formula whereby: C=percentage by mass of carbon Mn=percentage by mass of manganese Ni=percentage by mass of nickel Cr=percentage by mass of chrome Mo=percentage by mass of molybdenum by Steven and Haynes and the martensite start temperature Ms lies below the manufacturing temperature T.sub.F, and the LTT alloy furthermore is an alloy system on the basis of the main alloying elements iron-chrome-nickel or iron-manganese, construction of the component (3) on a construction surface (5) of the substrate (1) by layered application of at least one material at a manufacturing temperature T.sub.F by forming a component-substrate composite (7) via a boundary surface (6), cooling down at least the substrate (1) in the component-substrate composite (7) after the complete construction of the component (3) to a temperature below the martensite start temperature Ms, wherein, as a result of a martensite transformation and associated volume expansion of the metallic substrate material, a transformation stress is induced in the substrate (1) at least in the boundary surface (6) to the component (3), Separating the component (3) from the substrate (1).
2. The method according to claim 1, characterized in that the provision of the substrate (1) comprises a metal wire-based additive manufacturing by means of laser beams, electron beams or arcs, preferably a wire arc additive manufacturing (WAAM).
3. The method according to claim 1, characterized in that the provision of the substrate (1) comprises a WAAM with a multi-wire supply and/or an in situ alloying.
4. The method according to claim 1, characterized in that the substrate material has a martensite start temperature Ms of below 130? C., preferably below 100? C., particularly preferably below 70? C., which is calculated according to the formula by Steven and Haynes.
5. The method according to claim 1, characterized in that the cool-down of the substrate (1) in the component-substrate composite (7) takes place by immersion into a cooling medium.
6. The method according to claim 1, characterized in that the cool-down of the substrate (1) in the component-substrate composite (7) takes place in two or more cool-down/heat-up cycles.
7. The method according to claim 1, characterized in that a separation of the component (3) from the substrate (1) already takes place at least partially with the cool-down.
8. The method according to claim 1, characterized in that the substrate (1) is used in a method for the additive manufacturing again after the separation and a treatment.
9. The method according to claim 1, characterized in that the substrate (1) is formed from an LTT alloy, which undergoes a martensitic phase transformation and has a martensite start temperature Ms of below 100? C., preferably of below 70? C., which is calculated according to the formula by Steven and Haynes.
10. The method according to claim 1, characterized in that the substrate (1) is formed from at least two different metallic substrate materials.
11. The method according to claim 1, characterized in that the substrate is formed from at least two layers (L1, L2) of different metallic substrate material, which are arranged flat one on top of the other essentially parallel to the construction surface (5), wherein the substrate material of the layer (L1), which comprises the construction surface (5) or which is arranged closer to the construction surface (5), in each case has a higher martensite start temperature Ms than the substrate material of the layer (L2) arranged therebelow.
12. The method according to claim 1, characterized in that the substrate has brittle phases, which are formed in the construction surface (5), in the substrate material.
13-15. (canceled)
Description
BRIEF DESCRIPTION OF THE FIGURES
[0061] FIG. 1a-c schematically show steps of a method according to the invention for the additive manufacturing
[0062] FIG. 2 schematically shows an arc wire welding process with GMAW welding,
[0063] FIG. 3a-b schematically show the manufacturing of a substrate according to the invention,
[0064] FIG. 4a shows a photographic image of the substrate from Example 1,
[0065] FIG. 4b shows a bar chart with the determined chemical compositions of the substrate from Example 1, assigned to the measuring points marked in FIG. 4a,
[0066] FIG. 5 shows the temperature strain curve of the substrate material from Example 1 in a diagram.
[0067] FIG. 6 shows the calculated martensite start temperatures for the measuring points from Example 1 in a bar chart
[0068] FIG. 7a shows a photographic image of the component-substrate composite from Example 1 after the cool-down
[0069] FIG. 7b shows the enlargement of the region X of the component-substrate-composite marked in FIG. 7a
[0070] FIG. 8 schematically shows a preferred embodiment with a multi-material substrate.
[0071] The invention will be described in more detail below with reference to the figures. It is important to note thereby that different aspects are described, which can each be used individually or in combination. This means that any aspect can be used with different embodiment of the invention, unless explicitly described as pure alternative.
[0072] For the sake of convenience, reference will generally always be made only to one entity. Unless noted explicitly, however, the invention can in each case also have several of the entities in question. In this respect, the use of the word one is to be understood only as an indication that at least one entity is used in a simple embodiment.
[0073] Insofar as methods are described below, the individual steps of a method can be arranged and/or combined in any order, unless specified otherwise by the context. The methods can furthermore be combined with one anotherunless explicitly characterized otherwise.
[0074] FIGS. 1a-c schematically show a process of a method according to the invention for the additive manufacturing.
[0075] In FIG. 1a, a substance for constructing a component 3 in layers 4 (coats) is applied to a provided substrate 1 by means of a print head 2. In the shown embodiment, the substrate 1 is a substrate plate. According to the invention, the substrate 1 is formed from a metallic material. The layered construction (in coats) of the component 3 of the substance takes place at a specified manufacturing temperature T.sub.F. At this temperature T.sub.F, the material of the substrate 1 is present in a material phase, for example in an austenite phase (?) with an assigned volume. When applying the first layer 4a of the substance to the construction surface 5 of the substrate 1, the boundary surface 6 to the component 3 is created and thus a component-substrate composite 7. The material of the substrate 1 (substrate material) The substrate 1 according to the invention is formed from a metallic material, which undergoes a martensitic phase transformation below the manufacturing temperature T.sub.F and preferably has a martensite start temperature of below 140? C., for example below 100? C., for example of below 70? C. particularly preferably of below 60? C. The substrate 1 can have, for example, a martensite start temperature Ms of approx. 55? C., 50? C., 40? C., 30? C. or 20? C. or of below 20? C., for example 0? C. In an embodiment, which is preferred according to the invention, the metallic substrate material is a low transformation temperature (LTT) alloy.
[0076] In FIG. 1b, the created component-substrate composite 7 is cooled down according to the invention in a next step after the complete construction of the component 3 on the substrate plate 1. The cool-down can take place, for example, by immersion into a cooling medium, such as, for example, liquid nitrogen. A phase transformation (?.fwdarw.?) of the substrate material from ? towards the martensite phase ? martensitic phase transformation (martensite transformation) takes place during the cool-down. A volume expansion 8 of the substrate 1 is associated therewith, which is illustrated schematically in the figure by means of the dashed illustration. A compressive stress is induced in the boundary surface 7 by means of the volume expansion 8 of the substrate 1.
[0077] The component 3 is separated from the substrate plate in FIG. 1c. At the time of the separation from the component 3, the substrate 1 in the illustrated form is present completely of substrate material in martensite phase ? with the maximum martensitic volume expansion 8, which, according to the invention, effects at least a partial separation of the component 3 from the substrate 1. In a preferred embodiment of the method according to the invention, the substrate 1 already detaches completely from the component 3 during the cool-down with the martensite transformation and the volume expansion 8 created therewith and the resulting compressive stresses in the boundary surface 6. A complex subtractive removal of the substrate 1 from the component 3 is thus no longer required. This in particular also represents significant time and costs savings in the manufacturing process for an industrial series production. The substrate 1, thus for example a substrate plate, can furthermore be reused, optionally after slight treatment, for example by means of superficial grinding or milling, thus resulting in further options for cost savings.
[0078] FIG. 2 schematically shows an arc wire welding method, for example GMAW welding, which, in a preferred embodiment, can be used in a method according to the invention, as also illustrated in FIGS. 1a-c. A welding torch 2 is used as print head 2. During the GMAW welding, a consumable electrode D2 is used, which simultaneously also serves as welding filler material. For this purpose, a continuously conveyed wire-shaped welding filler material (welding wire) D1 and the material of the consumable electrode as welding filler material D2, as well as at least partially the construction surface 5 of the substrate plate 1 is melted with the help of a created electric arc 9 as heat source during the GMAW welding. In the effective region of the arc 9 (process zone), the welding filler material D1, supplied as cold wire, and the welding filler material D2 transitions, mostly in drop form, into the resulting weld pool 10 in the substrate plate 1 and form a first welding bead after solidification. By moving the welding torch 2 in the welding direction SR and of the supplied wire D1, any contour material can be applied along a specified path. The process of the layered application is then repeated until the complete construction of the component 3. The GMAW method is usually carried out by using a protective gas in order to prevent an oxidation of the weld pool 10 in the process zone.
[0079] FIGS. 3a and 3b schematically show the manufacturing of a blank 1a of a substrate 1 according to the invention by means of additive manufacturing. An arc wire welding method, as illustrated in FIG. 2, is preferably used for this purpose.
[0080] The construction of a blank 1a for a substrate 1 by means of layered application of substrate material on a base 11 is illustrated in FIG. 3a. The manufacturing of the substrate plate 1 according to the invention preferably takes place by means of layered construction of a wall-shaped structure with the help of a cold wire-supported GMAW welding process, as it has been described with regard to FIG. 2. In a further preferred embodiment, several continuously supplied welding wires D (welding filler materials) of identical or different alloys and can be conveyed into the process zone and can be melted. If welding filler materials of a different chemical composition are used, they are mixed in the process zone into the desired alloy. By means of layered deposition welding, a blank 1a is then produced for the substrate plate 1 with individually set desired alloy with the desired martensite start temperature Ms. The Ms temperature (martensite start temperature) is set up so that a martensitic phase transformation below the manufacturing temperature of the downstream construction of a desired component 3 is induced by means of additive manufacturing.
[0081] The post-processing of the manufactured substrate blank 1a by a machining of the surfaces to a flat substrate plate 1 (dashed contour) with the dimensions 180?50?5 mm, for example by means of a milling machine 12, is illustrated schematically in FIG. 3b.
[0082] FIG. 4a shows a photographic image of the substrate 1, thus of the manufactured substrate plate 1 from Example 1. Measuring points, at which the chemical composition of the substrate 1 was determined by means of spark spectrometric analysis, are displayed in the image. The marked measuring points are distributed over the length of the substrate plate 1 in three clusters P1, P2 and P3.
[0083] FIG. 4b shows a bar chart with the determined chemical compositions of the substrate 1 from Example 1, assigned to the measuring points marked in FIG. 4a. In other words, they represent the results of the spark spectrometric analysis (OES) of the chemical composition of the bar chart assigned in the produced imaged substrate 1 from FIG. 4a. The results of the OES measurements are illustrated in the bar chart as average values of the measuring values in the measuring cluster P1, P2 and P3. The averaged composition of the substrate material has already been specified above in the description of Example 1.
[0084] FIG. 5 shows the temperature strain curve of the substrate material from Example 1 in a diagram. In addition to the thermal strain, the jump of the strain curve can be seen at the start of the martensite transformation at Ms=55? C. The substrate material experiences the largest volume expansion 8 during the cool-down at the martensite finish temperature Mf, which lies approximately at ?145? C. in the case of the substrate material from Example 1. LTT alloys are characterized in that a shift towards lower temperatures is attained by adapting the alloying elements and composition. Compressive stresses, which counteract the thermal shrinkage stresses (LTT effect), are induced by means of the volume change during the martensite transformation. While this mechanism is used during the joint welding to reduce the residual welding stress in that the alloys are adapted so that the martensite transformation is concluded at room temperature, the martensite transformation and the associated volume expansion 8 is thus used according to the invention to induce compressive stresses in the boundary surface 6 from the substrate 1 to the component 3 applied thereon and to thus provide for an at least significantly simplified separation.
[0085] FIG. 6 shows the determined martensite start temperatures Ms for the chemical compositions of the substrate plate 1 from Example 1 determined in the measuring clusters P1, P2 and P3, in a bar chart.
[0086] FIG. 7a shows a photographic image of the component-substrate composite 7 from Example 1 after the cool-down in liquid nitrogen with a holding time of 5 minutes. While it was determined prior to the cool-down that no substance separation whatsoever is present between component 3 and substrate 1, a significant substance separation, which extends over approx. 25% of the sample length, was observed in the marked edge region X after quenching the component-substrate composite 7.
[0087] FIG. 7b shows the enlargement of the region X of the component-substrate composite 7 marked in FIG. 7a, in which the crack formation and thus the partial separation of the component 3 from the substrate 1 can be seen clearly.
[0088] FIG. 8 schematically shows a preferred embodiment with a multi-material substrate. In this preferred embodiment, the substrate 1 is formed from at least two layers L1, L2 of different metallic substrate materials, which are arranged one on top of the other essentially parallel to the construction surface 5, wherein the substrate material of the layer L1 which comprises the construction surface 5 (top side) or which is arranged closer to the construction surface 5, in each case has a higher martensite start temperature Ms than the substrate material of the layer L2 arranged there below. The first layer L1, which comprises the construction surface 5, can have, for example, a martensite start temperature Ms of, for example Ms=20? C. and the layer L2 arranged therebelow, which is further away from the construction surface 5, can have a martensite start temperature Ms of >>0? C. In such a multi-material substrate plate, a preferred direction is provided to the deformation effect during the cool-down, which even further simplifies the separation from the constructed component 3. The preferred directions, which result from the illustrated volume expansion 8 (illustrated in a dashed manner) of the layers L1 and L2, which are pronounced differently at the same temperature, are illustrated schematically with the help of the plotted arrows.
[0089] The invention describes the use of the volume expansion effect of a martensitic phase transformation of a substrate, for example in a substrate plate, which is made, for example, of an LTT alloy, in a method for the additive manufacturing of a component for the significantly simplified separation of the component from the substrate. The chemical composition and the construction of the substrate are thereby set so that a martensitic phase transformation below the manufacturing temperature takes place during the additive construction of the component. According to the invention, a component can thus be constructed in layers on the substrate plate according to the invention, and at least the substrate plate can be cooled down to a temperature, which causes the martensite transformation thereof and the associated volume expansion, after the concluded construction of the component. Compressive stresses, which provide for a simplified or even automatic release of the component from the substrate plate, are created in the boundary surface between component and substrate plate by means of the volume expansion of the substrate plate. A complex subtractive removal of the substrate is no longer required. This also represents significant time and cost savings in the manufacturing process in particular also for an industrial series production. The substrate, thus for example a substrate plate, can furthermore be reused after slight post-processing, for example by means of superficial grinding or milling, whereby further options for cost savings result.
LIST OF REFERENCE NUMERALS
[0090] 1 substrate (1a blank of the substrate) [0091] 2 print head/welding torch [0092] 3 component [0093] 4 substance layers [0094] 5 construction surface of the substrate [0095] 6 boundary surface [0096] 7 component-substrate composite [0097] 8 volume expansion [0098] 9 arc [0099] 10 weld pool [0100] 11 base (substrate plate for the substrate construction) [0101] 12 milling machine (tool for machining) [0102] T.sub.F manufacturing temperature [0103] Ms martensite start temperature [0104] Mf martensite finish temperature [0105] P1,P2,P3 measuring clusters for the OES analysis [0106] D1 welding filler material (for example cold wire) [0107] D2 welding filler material (for example consumable electrode) [0108] D welding wire/welding filler material [0109] SR welding direction [0110] R edge region with crack formation [0111] L1 material layer [0112] L2 material layer
