Metal powder for additive manufacturing, and additively manufactured object

Abstract

Disclosed is a metal powder for additive manufacturing, which is used for the formation of an additively manufactured object by an additive manufacturing method in order to form a stable powder bed for achieving a high-density additively manufactured object that has a relative density of 99% or more, the metal powder having a -63 µm + 45 µm sieve particle size (mass%) of 9% or more and a particle diameter D5 of 9 μm or more. Also disclosed is an additively manufactured object which is formed by an additive manufacturing apparatus with use of the metal powder for additive manufacturing, the additively manufactured object being characterized by having a relative density of 99.0% or more.

Description

Metal powder for additive manufacturing and additive manufactured body

[0001] The present invention relates to a metal powder for additive manufacturing and an additive manufactured product.

[0002] In the above-mentioned technical field, Patent Document 1 discloses that when additive manufacturing is performed by forming a powder bed using a metal powder having properties defined by an average particle diameter D50 and TD (tap density), an additive manufactured body having a relative density of 95% or more can be obtained.

[0003] Japanese Patent Application Laid-Open No. 2021-017639

[0004] However, at a relative density of 95%, open pores occur, which can lead to errors such as leakage when handling fluids in additive manufacturing applications. Therefore, to obtain high-density additive manufacturing objects with a relative density of 99% or higher, it is necessary to form a more stable powder bed. The object of the present invention is to provide a technology that solves the above-mentioned problems.

[0005] In order to achieve the above object, the metal powder for additive manufacturing according to the present invention is a metal powder for additive manufacturing used to manufacture an additive manufacturing body by an additive manufacturing method, and has a -63 μm+45 μm sieve particle size (mass%) of 9% or more and a particle diameter D5 of 9 μm or more.

[0006] In order to achieve the above object, the layered object of the present invention is a layered object manufactured by an layered manufacturing device using the above metal powder for layered manufacturing, and the relative density of the layered object is 99.0% or more.

[0007] According to the present invention, a stable powder bed can be formed to obtain a high-density layered object with a relative density of 99% or more.

[0008] 1 is a diagram showing the particle size distribution of the average particle size D50, and the relationship between the particle size D5 corresponding to the particle size distribution and the -63 μm+45 μm sieve particle size (mass %).

[0033] FIG. 1 is a diagram showing the evaluation results of the powder beds in this example and a comparative example.

[0034] FIG. 1 is a diagram showing the relationship between the particle size D5 of the metal powder for additive manufacturing in this example and a comparative example and the -63 μm+45 μm sieve particle size (mass %).

[0035] FIG. 1 is a diagram showing the particle size distribution in each region of FIG. 3, with the value of the particle size D5 on the horizontal axis.

[0036] FIG. 1 is a diagram showing air leakage of the cylinder as the additive manufacturing body in this example and a comparative example.

[0037] FIG. 1 is a diagram showing the experimental results of the relationship between the -63 μm+45 μm sieve particle size (mass %) and the particle size D5 (μm) and the quality and stability of the powder bed formation, and the stable height of the relative density of the additive manufacturing body, for various combinations of metals and elements. 1 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of powder bed formation, and the stable height of the relative density of an additive manufacturing body for various combinations of metals and elements. 2 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of powder bed formation, and the stable height of the relative density of an additive manufacturing body for various combinations of metals and elements. 3 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of powder bed formation, and the stable height of the relative density of an additive manufacturing body for various combinations of metals and elements. 1 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of the powder bed formation, and the stable height of the relative density of the layered object, for various combinations of metals and elements. 2 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of the powder bed formation, and the stable height of the relative density of the layered object, for various combinations of metals and elements.1 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of the powder bed formation, and the stable height of the relative density of the layered object, for various combinations of metals and elements. 2 is a diagram showing experimental results regarding the relationship between the -63 μm+45 μm sieve particle size (mass %) and particle diameter D5 (μm) and the quality and stability of the powder bed formation, and the stable height of the relative density of the layered object, for various combinations of metals and elements.

[0009] Hereinafter, embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, the components described in the following embodiments are merely examples and are not intended to limit the technical scope of the present invention.

[0010] Copper alloy powder (alloy powder containing copper as a main component) will be described as the metal powder for additive manufacturing in this embodiment. Before that, the current state of copper alloy powder for additive manufacturing will be described.

[0011] <Current status of metal powders for additive manufacturing> Patent Document 1 discloses that when additive manufacturing is performed by forming a powder bed using metal powder with properties specified by the average particle diameter D50 and TD (tap density), an additive manufactured body with a relative density of 95% or more can be obtained.

[0012] However, the average particle diameter D50 represents the median value in the particle size distribution of the powder. Therefore, as shown in particle diameter distribution 110 in Figure 1, even powders with the same average particle diameter D50 value can have a broad powder diameter distribution 111 with a large amount of fine and coarse powder, or a sharp powder diameter distribution 112 with almost no fine or coarse powder. Therefore, since the amount of fine and coarse powder cannot be clearly determined from the average particle diameter D50 value, adjusting the average particle diameter D50 may not stabilize the powder bed. If the relative density of the additive manufacturing object falls below 99%, problems such as leakage may occur, especially when handling fluids.

[0013] The powder size distributions 113 and 114 in Figure 1 are intermediate between the broad powder size distribution 111 and the sharp powder size distribution 112, and it is believed that among these there is a powder size distribution in which a powder bed is stably generated and the relative density of the layered manufactured body is stabilized at 99% or more.

[0014] Metal Powder for Additive Manufacturing According to the Present Embodiment The inventors focused on the particle diameter D5 (μm), which represents the size of fine particles that inhibit the powder bed, and the -63 μm + 45 μm sieve particle size (mass %), which represents the amount of coarse powder required to improve fluidity and powder bed density and form a stable powder bed, as characteristics that define the powder size distribution that will stably generate a powder bed and stabilize the relative density of the additive manufacturing body at 99% or higher. Here, the particle diameter D5 is a value obtained by laser diffraction, and the -63 μm + 45 μm sieve particle size is a value obtained by the sieving test method specified in JIS Z8815:1994.

[0015] Powder size distributions 111 to 114 of powders having the same average particle size D50 value were plotted on a graph 120, with the horizontal axis representing the particle size D5 (μm), which indicates the size of fine particles, and the vertical axis representing the amount of coarse powder required to form a stable powder bed, -63 μm + 45 μm sieve particle size (mass %). Based on the results of the example and comparative example, a particle size threshold 121 (particle size D5 is 9 μm) and a sieve particle size threshold 122 (-63 μm + 45 μm sieve particle size (mass %) is 9%) were obtained to separate powder size distribution 113, which generates a stable powder bed and stabilizes the relative density of the layered manufactured object at 99% or more, from the other powder size distributions 111, 112, and 114.

[0016] Powders with a particle diameter D5 smaller than 9 μm and a −63 μm+45 μm sieve particle size (mass %) of 9% or more have a broad particle size distribution, as shown in powder diameter distribution 111. Therefore, segregation occurs during storage of the metal powder for additive manufacturing in the additive manufacturing device, and a stable powder bed cannot be formed until additive manufacturing is completed.

[0017] Powders with a particle diameter D5 of 9 μm or more and a -63 μm + 45 μm sieve particle size (mass %) of less than 9% have a sharp particle size distribution like powder diameter distribution 112 and good fluidity. However, if the particle sizes are too uniform, the density of the powder bed decreases, leading to a decrease in relative density. Furthermore, powders produced by atomization methods, etc., require sieving within a very narrow particle size range, which results in poor productivity.

[0018] A powder having a particle size D5 smaller than 9 μm and a −63 μm+45 μm sieve particle size (mass %) of less than 9% is a powder whose particle size distribution has a certain balance, such as powder size distribution 114. However, if the powder as a whole is pulverized, the flowability is impaired, and a powder bed cannot be formed in the first place.

[0019] In this way, by using a metal powder having a particle size distribution of powder size distribution 113 in which the -63 μm + 45 μm sieve particle size (mass%) is 9% or more and the particle diameter D5 (volume distribution) by laser diffraction method is controlled to be 9 μm or more, high-density (relative density of 99% or more) additively manufactured bodies can be stably obtained.

[0020] First Embodiment Copper powder and copper alloy powder (alloy powder containing copper as the main component) will be described as metal powders for additive manufacturing according to a first embodiment.

[0021] The copper powder of this embodiment contains copper and unavoidable impurities, such as elements P and Al, in an amount of 0.01% by mass or less.

[0022] The copper alloy powder of the present embodiment contains 0.01 mass % or more and 32.0 mass % or less of an additive element M (at least one element of the elements Mg, Al, Si, P, Cr, Fe, Ni, Zn, Zr, Ag, and Sn), with the remainder being copper and unavoidable impurities.

[0023] The additive element M is added to improve the properties of the copper alloy powder (e.g., fluidity), the properties during additive manufacturing (e.g., laser reflectivity and laser absorptivity), and the properties of the additive manufactured body (mechanical properties: strength, abrasion resistance, toughness, etc.; physical properties: electrical conductivity, heat resistance, etc.). However, in this embodiment, conditions have been found to specify a copper alloy powder that stably generates a powder bed and stabilizes the relative density of the additive manufactured body at 99% or more.

[0024] Each element of the additive element M is added in the following range so that the total amount of the additive element M falls within the range of 0.01 mass % to 32.0 mass %. For example, Al is in the range of 0.01 mass % to 3.92 mass %, Si is in the range of 0.03 mass % to 0.97 mass %, P is in the range of 0.01 mass % to 0.14 mass %, Cr is in the range of 0.01 mass % to 1.33 mass %, Fe is in the range of 0.01 mass % to 0.29 mass %, Ni is in the range of 0.06 mass % to 4.08 mass %, Zr is in the range of 0.04 mass % to 0.31 mass %, and Sn is in the range of 0.24 mass % to 5.09 mass %, etc.

[0025] <Method for producing copper alloy powder> The method for producing the copper alloy powder for additive manufacturing of this embodiment is not particularly limited, but a method in which powder particles are rapidly cooled and solidified from a molten state, such as gas atomization, water atomization, centrifugal atomization, plasma atomization, or plasma rotating electrode method, is preferred. From the viewpoint of mass production, gas atomization is particularly preferred. The produced powder can be classified under predetermined classification conditions using a known classification method to adjust the copper alloy powder for additive manufacturing to an appropriate particle size. An air classifier can be suitably used as a classification device for performing classification. The copper alloy powder may also be subjected to mechanical milling or the like. For example, a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, or a vibration ball mill method can be used.

[0026] <Method for manufacturing additive manufacturing object> Various known metal additive manufacturing techniques can be used to manufacture copper alloy additive manufacturing objects. For example, in powder bed fusion, metal powder is spread evenly on a manufacturing stage using a blade or roller to form a powder layer, and then a laser or electron beam is irradiated at predetermined positions on the powder layer to sinter and melt the metal powder, repeatedly producing an additive manufacturing object. In the metal additive manufacturing process, a large number of process parameters must be controlled to obtain high-quality additive manufacturing objects.

[0027] In the laser-based powder bed fusion method, there are many scanning conditions such as laser output and laser scanning speed. Therefore, in order to set the optimal scanning conditions, the main parameters are adjusted using the energy density, which is an index that summarizes the main parameters. Energy density E [J / mm ３ ] is determined by E = P / (v × s × t), where P [W] is the laser output, v [mm / s] is the laser scanning speed, s [mm] is the laser scanning pitch, and t [mm] is the powder layer thickness. In the laser-based powder bed fusion method, the energy density is 150 J / mm ３ More than 450J / mm ３ The energy density is preferably 150 J / mm or less. ３ If the melting time is less than this, the powder layer will not melt or will not fuse properly, resulting in defects such as voids in the additive manufacturing product.

[0028] Energy density is 450 J / mm ３If the temperature exceeds this range, sputtering occurs, destabilizing the surface of the powder layer and resulting in defects such as voids in the additive manufacturing object. In electron beam powder bed fusion (EBFM), when the powder layer is irradiated with an electron beam, negative charges accumulate in the powder layer, causing the powder to rise into a mist, resulting in a "smoke" phenomenon and insufficient melting. Therefore, to prevent this charge-up, a preliminary step of preheating and pre-sintering the powder layer is required. However, if the preheating temperature is too high, sintering progresses, causing necking, making it difficult to remove the remaining powder from inside the additive manufacturing object after shaping. For this reason, the preheating temperature for copper alloy powder for AM is preferably set to 400 to 800°C. While the metal AM technology using the powder bed fusion method has been exemplified here, general AM methods for producing additive manufacturing objects using the copper alloy powder for AM of the present invention are not limited to this method. For example, AM methods using directed energy deposition may also be employed.

[0029] <Method for Measuring Relative Density> Methods for measuring relative density include: (1) a method in which an additively shaped body is produced using a 3D powder additive manufacturing machine, and the relative density (%) is calculated as a cross-sectional area ratio obtained by subtracting the porosity of the cross section of the additively shaped body from 100; and (2) a method in which an additively shaped body is produced using a 3D powder additive manufacturing machine, the density of the produced additively shaped body is measured by Archimedes' method, and the relative density (%) is calculated by setting the theoretical density (the density of an ingot material having the same composition as the additively shaped body) to 100%. In this embodiment, method (1) was adopted.

[0030] According to this embodiment, the copper powder or copper alloy powder for additive manufacturing is (1) specified as a powder characteristic by the amount of coarse powder required to form a high-density, stable powder bed without reducing the apparent density, using the "-63 μm + 45 μm sieve particle size (mass %)" obtained by "JIS Z8815:1994 Sieving Test Method," and (2) specified as "D5 (μm)" by the laser diffraction method, which specifies the particle size of fine powder that affects fluidity. This makes it possible to stably form a powder bed that allows for the production of additive manufacturing bodies with a high relative density (99% or more).

[0031] Second Embodiment Nickel alloy powder (alloy powder containing nickel as a main component) will be described as a metal powder for additive manufacturing according to a second embodiment.

[0032] The nickel alloy powder of this embodiment contains 50.88 mass% of the additive element N (at least one element of the elements Al, Si, Ti, Cr, Mn, Fe, Co, Nb, and Mo), with the remainder being nickel and unavoidable impurities.

[0033] The additive element N is added to improve the properties of the nickel alloy powder, the properties during additive manufacturing, and the properties (mechanical properties, physical properties) of the additive manufactured body. However, in this embodiment, conditions have been found to specify a nickel alloy powder that stably generates a powder bed and stabilizes the relative density of the additive manufactured body at 99% or higher. Therefore, the range of the amount of each element added to the additive element N is not limited and can be selected appropriately.

[0034] The method for manufacturing the nickel alloy powder, the method for manufacturing an additive manufacturing body using the nickel alloy powder, and the method for measuring the relative density are the same as those for the copper alloy powder of the first embodiment, so redundant explanations will be omitted.

[0035] According to this embodiment, the nickel alloy powder for additive manufacturing is (1) specified as a powder characteristic by the amount of coarse powder required to form a high-density, stable powder bed without reducing the apparent density, using the "-63 μm + 45 μm sieve particle size (mass %)" obtained by "JIS Z8815:1994 Sieving Test Method," and (2) specified as "D5 (μm)" by the laser diffraction method, which specifies the particle size of fine powder that affects fluidity. This makes it possible to stably form a powder bed that allows for the production of additive manufacturing bodies with a high relative density (99% or more).

[0036] Other Embodiments The metal powder or alloy powder for additive manufacturing that forms a stable powder bed for obtaining a high-density additive manufacturing object with a relative density of 99% or more, having a −63 μm+45 μm sieve particle size (mass %) of 9% or more and a particle diameter D5 (μm) of 9 μm or more, is not limited to copper, nickel, or alloys thereof as shown in the first and second embodiments. The requirement that the −63 μm+45 μm sieve particle size (mass %) of 9% or more and a particle diameter D5 (μm) of 9 μm or more is a general requirement that does not depend on the type of metal or the type of alloy.

[0037] Below, we conducted experiments on various combinations of metals and elements, including metals containing only unavoidable impurities or alloys with different main component elements, to examine the relationship between the -63 μm + 45 μm sieve particle size (mass %) and particle diameter D5 (μm), the quality and stability of powder bed formation, and the stable height of the relative density of the additive manufacturing body. The experimental results are shown in Figures 6A to 9B. Examples 101 to 122 and Comparative Examples 101 to 111 are experimental results for copper powder or copper alloy powder, while Example 201 is experimental results for nickel alloy powder.

[0038] The quality of the powder bed formation shown in Figures 6A to 9B (○: good, △: unstable, X: unsuccessful) was evaluated by forming a powder bed using a metal powder for additive manufacturing or an alloy powder for additive manufacturing, as shown in Figure 2. In Example 110 (201 in Figure 2), a uniform powder bed was formed (○). In Comparative Example 104 (202 in Figure 2), powder clumps occurred in some areas, making the powder bed unstable (△). In Comparative Example 109 (203 in Figure 2), a complete powder bed could not be formed, and molding was not possible (X). The bold frame in Figure 7B indicates a -63 μm + 45 μm sieve particle size (mass%) or particle diameter D5 (μm) outside the specified range.

[0039] The relative densities of the layered objects shown in Figures 6A to 9B were determined by producing layered objects using a 3D powder additive manufacturing machine and calculating the relative density (%) as the cross-sectional area ratio obtained by subtracting the porosity of the cross section of the layered object from 100.

[0040] 6A, 6B and 7A, 7B (Examples 101 to 122, 201), for metals containing only unavoidable impurities or alloys with different main component elements, in various combinations of metals and elements, the -63 μm+45 μm sieve particle size (mass%) is 9% or more and the particle diameter D5 is 9 μm or more, so a high-density, stable powder bed is formed and additive manufacturing objects with a relative density of 99% or more are stably manufactured.

[0041] On the other hand, Figures 8A, 8B and 9A and 9B show metal powders and alloy powders for which the -63 μm+45 μm sieve particle size (mass %) is less than 9% and / or the particle diameter D5 is less than 9 μm in various combinations of metals and elements, for metals containing only unavoidable impurities or alloys with different main component elements, and therefore a spotted, unstable powder bed is formed, and an additive manufacturing object with a relative density of 99% or more is not manufactured.

[0042] 6A to 9B are plotted on a graph with particle diameter D5 on the horizontal axis and -63 μm+45 μm sieve particle size (mass %) on the vertical axis. As shown in FIG. 3, powder groups 311 to 314, which indicate whether the powder bed is formed or not, exist with a threshold value as a boundary, as in FIG. 1. FIG. 4 shows the powder diameter distribution corresponding to powder groups 311 to 314 in FIG. 3, with particle diameter D5 on the horizontal axis.

[0043] 4, powders with a particle diameter D5 smaller than 9 μm and a −63 μm+45 μm sieve particle size (mass %) of 9% or more have a broad particle size distribution as shown in powder diameter distribution 311. Therefore, segregation occurs during storage of the metal powder for additive manufacturing in the additive manufacturing device, and a stable powder bed cannot be formed until additive manufacturing is completed.

[0044] In Figure 4, powders with a particle diameter D5 of 9 μm or more and a -63 μm + 45 μm sieve particle size (mass %) of less than 9% have a sharp particle size distribution like powder diameter distribution 312 and good fluidity. However, if the particle sizes are too uniform, the density of the powder bed decreases, leading to a decrease in relative density. Furthermore, powders produced by methods such as atomization require sieving within an extremely narrow particle size range, which results in poor productivity.

[0045] In Figure 4, powders with a particle size D5 smaller than 9 µm and a -63 µm + 45 µm sieve particle size (mass %) of less than 9% are powders with a particle size distribution that is balanced to a certain extent, such as powder size distribution 314. However, if the powder as a whole is pulverized, the flowability is impaired, and it becomes impossible to form a powder bed in the first place.

[0046] In this way, by using a metal powder having a particle size distribution of powder size distribution 313 in Figure 4, in which the -63 μm + 45 μm sieve particle size (mass%) is 9% or more and the particle diameter D5 (volume distribution) measured by laser diffraction method is controlled to 9 μm or more, a high-density (relative density of 99% or more) additively manufactured object can be stably obtained.

[0047] Using the copper alloy powders of Example 110 and Comparative Example 102, cylinders with a maximum thickness of 2 mm and a minimum thickness of 1 mm were fabricated, and a leak check was performed using compressed air at 0.2 MPa. The results of the leak check using compressed air at 0.2 MPa are shown in Figure 5.

[0048] As shown in Figure 5, a tube 501 with a maximum thickness of 2 mm and a minimum thickness of 1 mm was produced. Compressed air of 0.2 MPa was applied to this tube 501, and it was checked for air leakage in water. There was no air leakage in tube 502, which was produced by additive manufacturing using the copper alloy powder of Example 110. On the other hand, air leakage occurred in tube 503, which was produced by additive manufacturing using the copper alloy powder of Comparative Example 102. It is believed that the relative density of tube 503 was in the 98% range, which resulted in open pores, causing air leakage.

[0049] This application claims priority based on Japanese Patent Application No. 2023-188963, filed November 3, 2023, the disclosure of which is incorporated herein in its entirety.

Claims

1. A metal powder for additive manufacturing containing copper as a main component, used for manufacturing an additive body by an additive manufacturing method that forms a powder bed, the powder powder containing at least one of the following additive elements: Al: 0.01% by mass to 3.92% by mass; Si: 0.01% by mass to 0.97% by mass; P: 0.01% by mass to 0.14% by mass; Cr: 0.01% by mass to 1.33% by mass; Fe: 0.01% by mass to 0.29% by mass; Ni: 0.06% by mass to 4.08% by mass; Zr: 0.04% by mass to 0.31% by mass; Sn: 0.24% by mass to 5.09% by mass; Mg: 0.01% by mass to 0.21% by mass; and Zn: 0.01% by mass to 32.0% by mass; and the remainder being copper and unavoidable impurities; A metal powder for additive manufacturing, having a -63 μm + 45 μm sieve particle size (mass%) of 9% or more and a particle diameter D5 of 9 μm or more.

2. A metal powder for additive manufacturing containing nickel as its main component, used for manufacturing additive objects by an additive manufacturing method that forms a powder bed, containing 50.88% by mass of an added element N, at least one of the elements Al, Si, Ti, Cr, Mn, Fe, Co, Nb, and Mo, with the remainder being nickel and unavoidable impurities, having a -63 μm + 45 μm sieve particle size (mass %) of 9% or more, and a particle diameter D5 of 9 μm or more.

3. The metal powder for additive manufacturing according to claim 1 or 2, wherein the -63 μm + 45 μm sieve particle size (mass%) is a value obtained by a sieving test method defined in JIS Z8815:1994, and the particle diameter D5 is a value obtained by a laser diffraction method.

4. An additive body produced by additive manufacturing using the additive metal powder for additive manufacturing according to claim 1, comprising at least one of the following additive elements: Al: 0.01% by mass to 3.92% by mass; Si: 0.01% by mass to 0.97% by mass; P: 0.01% by mass to 0.14% by mass; Cr: 0.01% by mass to 1.33% by mass; Fe: 0.01% by mass to 0.29% by mass; Ni: 0.06% by mass to 4.08% by mass; Zr: 0.04% by mass to 0.31% by mass; Sn: 0.24% by mass to 0.97% by mass; Mg: 0.01% by mass to 0.21% by mass; and Zn: 0.01% by mass to 32.0% by mass; with the remainder being copper and unavoidable impurities; An additive manufacturing object having a cross-sectional area ratio of 99.0% or more, calculated by subtracting the porosity of the cross section of the additive manufacturing object from 100.

5. An additive manufactured body produced by an additive manufacturing method in which a powder bed is formed using the metal powder for additive manufacturing according to claim 2, the additive manufactured body containing 50.88 mass% of added element N, which is at least one of the elements Al, Si, Ti, Cr, Mn, Fe, Co, Nb, and Mo, with the remainder being nickel and unavoidable impurities, and the cross-sectional area ratio, calculated by subtracting the porosity of the cross section of the additive manufactured body from 100, is 99.0% or more.

Images