JP2005048234A - Metallic powder for metal light beam fabrication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape-formed material which has superior shape formability when being shape-formed by metal light beam (directed energy beam) fabrication, excellent machinability of the obtained shape-formed article, and no microcrack. <P>SOLUTION: A metallic powder for metal light beam fabrication is a powdery material used in a method for manufacturing a shaped material having a desired three-dimensional shape by irradiating a light beam on the powdery material to form a hardened layer, and stacking it; and includes 60-80 wt.% ferrous powder made from chrome molybdenum steel, 5-25 wt.% non-ferrous powder made from phosphor copper or copper-manganese, and more than 10 wt.% non-ferrous powder made from nickel. The metallic powder includes an increased amount of the non-ferrous powder made from nickel, so that it provides a shape-formed article having superior machinability, few microcracks, high strength and high toughness, though having hardness slightly decreased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metal powder for use in metal stereolithography to form a sintered layer by irradiating a powder layer made of metal powder with a light beam and laminating this sintered layer. It is.

  A sintered layer is formed by irradiating a specific area of the powder layer formed of metal powder with a light beam (directed energy beam, for example, a laser), and a new powder layer is formed on the sintered layer to identify the powder layer. There is known a technique for manufacturing a three-dimensional shaped article as a laminate of sintered layers by repeatedly forming a sintered layer by irradiating an area with a light beam.

  In this technology, which is called metal stereolithography, by adjusting the energy density of the light beam, the metal powder is solidified after almost completely melting from the state in which there are many gaps (holes) in the modeled object. It is possible to obtain a state, that is, a modeling density (sintered density) of almost 100%, and for this purpose, a molding die or the like that is required to have a smooth surface is also formed. You can also. In addition, it is possible to form the surface with a high density, the inside with a low density, and a medium density in the meantime, and when changing the density in this way, a smooth surface without sacrificing the modeling speed. Obtainable.

  However, in order to obtain a shaped object having such a density difference between the surface and the interior by metal stereolithography, a metal powder having characteristics different from those of metal powder used for normal powder sintering is required.

  For example, the particle size of the metal powder needs to be smaller than the thickness of the powder layer. At this time, the smaller the particle size, the higher the packing density of the powder, and the better the light beam (laser) absorption during modeling. In addition, the modeling density can be increased and the surface roughness can be decreased. However, if the powder is too fine and agglomerates, the packing density of the powder is decreased, and the powder cannot be spread uniformly and thinly.

  Further, in order to obtain a certain degree of modeling strength, it is necessary that the bonding area between the laser-irradiated modeling part and the underlying sintered layer is large and that the adhesion strength is high.

  Furthermore, the upper surface of the laser-irradiated portion should not rise so much. This is because, when the next powder layer is laid to form the next layer, if the bulge amount is equal to or greater than the thickness of the powder layer, the formation of the powder layer itself becomes difficult.

  In addition, since the metal powder has adhered to the surface of the modeled object, the processing when performing processing such as cutting finish to remove this unnecessary metal powder and expose the high-density surface It is desirable that the property is good.

  Of course, there should be no large cracks in the appearance, and it is desirable that the internal structure should be free of microcracks in consideration of the case of flowing a fluid (cooling water) inside an injection mold or the like.

  Here, a part or all of the metal powder irradiated with the laser is once melted and then rapidly solidified to form a sintered product. If the bonding area is large and the fluidity is large, the rise is small. Therefore, it is desirable that the fluidity when melted is large and the wettability is good.

From this point of view, the present applicant has disclosed in Japanese Patent Application No. 11-335178 (Japanese Patent Laid-Open No. 2001-152204: Patent Document 1) an iron-based powder of 70 to 90% by weight made of chromium molybdenum steel, phosphorous copper or A metal powder for metal stereolithography was proposed that includes 5 to 30% by weight of non-ferrous powder made of manganese copper and 0 to 10% by weight of non-ferrous powder made of nickel. Chrome molybdenum steel is adopted from the viewpoint of strength and toughness, phosphorous copper or manganese copper is adopted from the viewpoint of wettability and fluidity, and nickel is adopted from the viewpoint of strength and workability.
JP 2001-152204 A

  Although the metal powder for metal stereolithography of the above composition can obtain a generally preferable result in terms of obtaining a model having a density difference between the surface and the interior by metal stereolithography, the wet In addition to the problem of forming and fluidity, there are some problems during modeling, and cutting is difficult and chipping occurs at the cutting edge of the carbide end mill. This is not due to the fact that the hardness after modeling is as high as Hv400, but is considered to be caused by extremely hard metal powder particles remaining in the modeled object, and cannot be solved only by reducing the hardness. In addition, many microcracks are generated in the high-density sintered portion, and the microcracks cause a decrease in strength and toughness, and the obtained shaped article is used as a molding die. This is especially a problem.

  The present invention has been made in view of these points, and the object of the present invention is a modeled article that is excellent in the moldability in metal stereolithography and the cutting workability of the resulting modeled article, and has no microcracks. It is in providing the metal powder which can obtain.

  The metal powder for metal stereolithography according to the present invention is a powder used in a method for producing a shaped article having a desired three-dimensional shape by irradiating a powder material with a light beam to form a cured layer and stacking the cured layers. 60 to 80% by weight of iron-based powder made of chromium molybdenum steel, 5 to 25% by weight of non-ferrous powder made of phosphorous copper or manganese copper, and more than 10% by weight of non-ferrous powder made of nickel It has the feature in being. By increasing the blending amount of the non-ferrous powder made of nickel as compared with the conventional example, the hardness of the resulting molded article is slightly reduced, but it has excellent cutting workability and has few microcracks and has high strength and toughness. You can get something expensive. However, if the amount of non-ferrous powder made of nickel is too large, the adhesion strength with the base for modeling will decrease and the model will peel off from the base, so it should be kept within 30% by weight. Preferably, the blending amount of the chromium molybdenum steel powder is 60 to 80% by weight, the blending amount of the non-ferrous powder composed of phosphor copper or copper manganese alloy powder is 5 to 15% by weight, and the blending amount of the non-ferrous powder composed of nickel. When the content is 15 to 25 weight percent, particularly preferable results can be obtained.

  The average particle diameter of the iron-based powder and the non-ferrous powder is preferably 5 to 50 μm, and the average particle diameter of the iron-based powder is preferably smaller than the average particle diameter of the non-ferrous powder in terms of reducing microcracks.

  Further, when carburized iron-based powder is used, it is possible to improve wettability during melting and further reduce the occurrence of microcracks during solidification.

  In the metal stereolithography metal powder of the present invention, the non-ferrous powder made of nickel was more than 10% by weight, which was effective in improving wettability during melting and reducing the occurrence of microcracks during solidification. .

  Hereinafter, the present invention will be described in detail based on an embodiment. In addition, although the example of illustration shows what has the removal means 4 for the cutting process in the middle of modeling, and performs the cutting process of the surface of the modeled object modeled so far in the middle of the modeling, this invention is this removal The present invention can also be applied to normal metal stereolithography that does not have the means 4 and does not perform cutting work during modeling.

  FIG. 2 shows an example of an apparatus for metal stereolithography. By using a squeezing blade 21, the metal powder supplied on a lifting table 20 that moves up and down by a cylinder in a space surrounded by an outer periphery is smoothed. The powder layer forming means 2 for forming the powder layer 10 having a predetermined thickness Δt1 and the powder outputted from the laser oscillator 30 are irradiated onto the powder layer 10 through a scanning optical system such as a galvano mirror 31 to burn the metal powder. And a removal layer 4 formed by providing a milling head 41 via an XY drive mechanism 40 at the base portion of the powder layer formation unit 2. ing.

  As shown in FIG. 3, the manufacture of the three-dimensional shaped article in this product is a modeling base 22 on the upper surface of the lifting table 20 which is an adjusting means for adjusting the relative distance between the sintered layer forming means and the sintered layer. The first powder layer 10 is formed by supplying metal powder to the surface with the blade 21 and at the same time with the blade 21, and a portion of the powder layer 10 to be cured is irradiated with a light beam (laser) L to produce powder. Is sintered to form the sintered layer 11 integrated with the base 22.

  After that, the lifting table 20 is slightly lowered, the metal powder is supplied again, and the blade 21 is used to form the second powder layer 10. A light beam (laser) is applied to the portion of the powder layer 10 to be cured. L is irradiated to sinter the powder to form the sintered layer 11 integrated with the lower sintered layer 11.

  By lowering the elevating table 20 to form a new powder layer 10 and irradiating a light beam to make the required portion a sintered layer 11, a desired three-dimensional shaped object is manufactured. Yes, a carbon dioxide laser can be suitably used as the light beam, and the thickness Δt1 of the powder layer 10 is about 0.05 mm when the obtained three-dimensional shaped object is used for a molding die or the like. It is preferable to do this.

  The irradiation path of the light beam is created in advance from three-dimensional CAD data. That is, the contour shape data of each cross section obtained by slicing STL data generated from a three-dimensional CAD model at an equal pitch (0.05 mm pitch when Δt1 is 0.05 mm) is used. At this time, irradiation with a light beam is performed so that at least the outermost surface of the three-dimensional shaped object can be sintered at a high density (porosity of 5% or less), and the inside is baked to a low density. In other words, the shape model data is preliminarily divided into the surface layer part and the inside, and the inside is a sintering condition that becomes porous, and the surface layer part is a condition that the powder almost melts and becomes high density By irradiating with a light beam, a shaped object having a dense surface can be obtained at high speed.

  Then, the powder layer 10 is formed and the light beam is irradiated to repeatedly form the sintered layer 11. The total thickness of the sintered layer 11 is, for example, the tool length of the milling head 41. When the required value obtained from the above is reached, the removal means 4 is once activated to cut the surface of the shaped object that has been shaped so far. For example, if the tool (ball end mill) of the milling head 41 is capable of cutting with a diameter of 1 mm, an effective blade length of 3 mm and a depth of 3 mm, and the thickness Δt1 of the powder layer 10 is 0.05 mm, 60 layers of fired When the binder layer 11 is formed, the removing means 4 is operated.

  By removing the low-density surface layer of the powder adhering to the surface of the modeled object by cutting by the removing means 4, the high-density part is entirely exposed on the surface of the modeled object by cutting into the high-density part.

  The cutting path by the removing means 4 is created in advance from three-dimensional CAD data in the same manner as the light beam irradiation path. At this time, the machining path is determined by applying contour processing, but the Z-direction pitch does not need to stick to the lamination pitch at the time of sintering, and in the case of a gentle inclination, by interpolating with a finer Z-direction pitch, Keep a smooth surface.

  In manufacturing a three-dimensional shaped object in such metal stereolithography, what kind of metal powder is used as described above has a great influence on the point of formability and the quality of the object. However, from the aforementioned points required as metal powder for metal stereolithography, iron-based powder made of chromium molybdenum steel, non-ferrous powder made of phosphorous copper or manganese copper, and non-ferrous powder made of nickel In the present invention, 60 to 80% by weight of iron-based powder made of chromium molybdenum steel, 5 to 25% by weight of non-ferrous powder made of phosphorous copper or manganese copper, and non-ferrous made of nickel A system powder containing more than 10% by weight is used.

  The average particle diameter of the iron-based powder and the non-ferrous powder is preferably 5 to 50 μm. However, if the particle diameter is too small, aggregation occurs, so that the thickness Δt1 of the powder layer 10 is 0.05 mm. In this case, the average particle size is preferably about 30 μm. The generation of microcracks in the high density portion was small, and good formability could be obtained in both the high density portion and the low density portion.

Further, when carburized iron-based powder was used, it was possible to improve wettability during melting and further reduce the occurrence of microcracks during solidification. Carburizing may be performed by a conventional method such as carburizing in a mixed gas atmosphere of CO and CO ₂ (preferably adding several percent (3 to 15%) of methane gas or butane gas for promotion).

[Example]
Chrome-molybdenum steel SCM440 powder (see FIG. 4) with non-spherical particles and an average particle size of 20 μm, nickel Ni powder (see FIG. 5) with spherical particles and an average particle size of 30 μm, and spherical particles with an average particle size of 30 μm of copper manganese alloy CuMnNi (for example, Cu-10% Mn-3% Ni) powder (see FIG. 6) is prepared,
a 70% SCM440-21% Ni-9% CuMnNi
b 80% SCM440-10% Ni-10% CuMnNi
The metal powder for metal stereolithography was formed with the compounding amount. Each% is% by weight.

  Metal stereolithography was performed using this metal powder. The thickness of the powder layer was 0.05 mm, and the laser used was a carbon dioxide laser (90% output of 200 W output). When sintered at a laser scan speed of 75 mm / sec and a scan pitch of 0.25 mm, the nickel Ni compound was added. The amount of 20% a (see Fig. 1) is less microcracked than the amount of nickel Ni blended to 10% b. Chipping occurred at the cutting edge of No. 1, but chipping did not occur with the tool a, and the machinability was good.

  In addition, when sintered in the same conditions using copper phosphorus (CuP) alloy powder (spherical particles with an average particle size of 30 μm) instead of the copper manganese alloy in the above composition, the same results as in the above a and b were obtained. Met.

  Moreover, when sintered under the same conditions as the chromium molybdenum steel in a above, which has been carburized by the above-mentioned carburizing treatment, it is possible to obtain a shaped product with less microcrack generation than in the above a. did it.

  The metal powder in each of the above examples may be formed as a granulated powder. It becomes easy to handle.

It is a cross-sectional photograph of magnification 25 times of the metal stereolithography thing manufactured with the metal powder of an example of embodiment of this invention. It is a schematic perspective view of an example of the apparatus which performs metal stereolithography using the metal powder same as the above. It is explanatory drawing same as the above. It is a SEM photograph of the non-spherical particle-like chromium molybdenum steel powder same as the above. It is a SEM photograph of the spherical particle-like nickel powder same as the above. It is a SEM photograph of the spherical particulate copper manganese alloy powder same as the above.

Claims (3)

A powder material used for a method of forming a hardened layer by irradiating a powder material with a light beam and stacking the hardened layer to produce a shaped article having a desired three-dimensional shape,
60-80% by weight of iron-based powder made of chromium molybdenum steel,
5 to 25% by weight of non-ferrous powder composed of phosphorous copper or manganese copper,
A metal powder for metal stereolithography, characterized by containing more than 10% by weight of non-ferrous powder made of nickel.   The average particle size of each of the iron-based powder and the non-ferrous powder is 5 to 50 µm, and the average particle size of the iron-based powder is smaller than the average particle size of the non-ferrous powder. Metal powder for metal stereolithography.   The metal powder for metal stereolithography according to claim 1 or 2, wherein the iron-based powder is carburized.