JP7401742B2 - Manufacturing method for integrally molded parts, iron alloy powder, and integrally molded parts - Google Patents

Description

The present invention relates to an integrally molded part, an iron alloy powder for forming the integrally molded part, and a method for manufacturing the integrally molded part.

In the robot industry and automobiles, which are expected to develop significantly in the future, the shapes of gears and shafts are expected to become smaller or more complex.As small robots are expected to become even more popular in the future, parts will need to be made smaller than ever before. requested. Therefore, as parts become smaller, deflection and buckling of the parts become a problem. This is because even parts made of materials with guaranteed strength lack rigidity. That is, in order to realize a small robot, a material that has not only strength but also rigidity is required.

Manufacturing methods for materials that achieve high rigidity include particle composites, textures, and element additions, but since increasing rigidity isotropically is required in mechanical design, a method that combines hard particles is promising.

Patent Document 1 discloses a reciprocating member made of an iron-based composite material in which a reinforcing phase mainly composed of _TiB2 is dispersed, with the aim of expanding the degree of freedom in designing the reciprocating member and making the reciprocating device lighter and more compact. Disclosed.

Patent Document 2 discloses a structural member in which high Young's modulus particles of 20 vol% or less are dispersed in an Fe-based metal matrix, with the aim of providing a high-rigidity material with improved ductility and toughness that is suitable as a material for automobiles and robots. Disclosed.

Patent Document 3 discloses that the material has a high Young's modulus and is made of at least one type of boride mainly composed of group 4A elements (Ti, Zr, Hf, Rf) for the purpose of providing a highly rigid structural metal material. Iron-based alloys are disclosed.

Patent Document 4 discloses, for the purpose of providing a particle-reinforced high-strength, low-density steel having an elastic modulus equivalent to conventional steel, the steel contains 3% by weight of Σ(TiB ₂ +Fe ₂ B+TiC) particles, and , −0.5≦(Ti−2.22×B)≦1.6 is disclosed.

Patent Document 5 discloses that Ti carbide, boride, or a composite compound thereof is added to a matrix made of iron or iron alloy for the purpose of providing a high-rigidity, high-toughness steel with high toughness and excellent machinability. It is disclosed that it is dispersed at 5 to 50 vol%.

Patent No. 3409301 Japanese Patent Application Publication No. 5-239504 Japanese Unexamined Patent Publication No. 7-188874 Patent No. 6370787 Patent No. 3478930

“Stiff, light, strong and ductile: nano-structured High Modulus Steel”, D. Raabe et al, Max-Planck-Institute, Published online June 5, 2017

A method is known in which an iron alloy and hard particles are mixed, molded, and sintered as in Patent Documents 2 and 3, but in this case, the particle size of the hard particles is on the order of μm, and finer particles are required. However, it was not possible to obtain a product in which hard particles were dispersed, and there was a limit to achieving high strength and high rigidity.

In addition, in the method described in Patent Documents 1, 4, and 5, in which the necessary elements are dissolved in solid solution in the powder of the starting material and hard particles are precipitated during molding, not only the expected hard particles but also soft particles are formed. The inventor has discovered that there is a problem in that the required strength and rigidity cannot be obtained because the particles are damaged or the expected hard particles are not formed but only soft particles are formed.

Non-Patent Document 1 discloses that strength, hardness, and ductility could be achieved in a low-density steel by dispersing nano-sized TiB ₂ particles in the steel. However, the fatigue properties of the steel are not disclosed in Non-Patent Document 1.

The present invention has been made in view of these circumstances. That is, the present invention provides an integrally molded component with improved strength and rigidity by controlling the particle size of hard particles to several hundred nanometers, an iron alloy powder for forming the integrally molded component, and a method for manufacturing the integrally molded component. The purpose is to

The present inventors have made extensive studies on controlling the strength and rigidity by including hard particles in the molded article.

As a result, we first came up with the idea that in order to include hard particles with a fine particle size in a molded product, crystal nuclei are necessary in the process of crystallizing the hard particles in the molded product. In the case of metal lamination technology that uses laser sintering, because there are crystal nuclei of hard particles in the iron alloy powder, this phenomenon occurs when the iron alloy powder is melted by energy rays, and the hard particles that are initially included in the iron alloy powder are used as starting points. By growing up.

In addition, the present inventors found that it is necessary to use, as the above-mentioned iron alloy powder, one in which the difference between the liquidus temperature and the solidus temperature of the hard particles is sufficiently large, and the driving force for crystallizing the hard particles is large. I found out that there is. For example, it has been found that it is preferable for the iron alloy powder to have a component richer in boride or carbide than in a eutectic component of iron and boride or carbide.

The gist of the present invention for solving the above problems is as follows:
(1) An integrally molded part of an iron alloy in which one or more particles selected from TiB ₂ , TiC, and WC are dispersed;
The average particle size of the particles is 300 nm or less,
The volume fraction of the particles is 10 vol% or more and 30 vol% or less,
The volume fraction of particles having a particle size of more than 500 nm among the particles is 1 vol% or less,
The average particle diameter of the particles is determined by selecting 10 fields of view of 0.5 mm x 0.5 mm from the cross section of the integrally molded part using FE-SEM, and selecting one of the TiB ₂ , TiC, and WC in each field of view. Determine the area of each of the selected one or more types of particles, calculate the diameter in terms of a circle from the area, and calculate the area of the ten selected particles for particles whose diameter in terms of a circle is 1 nm or more among the particles. Calculated by arithmetic averaging over the number of circle equivalent diameters over the entire field of view,
The volume fraction of the particles is determined by adding up the area of the particles in each of the fields of view for particles with a circular equivalent diameter of 1 nm or more, and calculating the area fraction of the particles in the entire field of view of the 10 selected locations. Calculated by averaging the area fractions of the particles over
An integrally molded part characterized by:
(2) The integrally molded part according to (1), wherein the integrally molded part is a sintered body.
(3) It is an integrally molded part of an iron alloy in which one or two kinds of particles selected from TiB ₂ and TiC are dispersed, and has a first region and a second region, and has an average Vickers of the first region. The integrally molded part according to (1) or (2), wherein the hardness is more than 200 Hv, and the average Vickers hardness of the second region is 150 Hv or more and 200 Hv or less.
(4) In the first region, the value obtained by subtracting the volume fraction of particles with a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles with a particle size of 1 nm or more and less than 300 nm is
(3), characterized in that it is larger than the value obtained by subtracting the volume fraction of particles with a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles with a particle size of 1 nm or more and less than 300 nm in the second region. One-piece molded part.
(5) The integrally molded part according to any one of (1) to (4), wherein the particles are a boride or carbide of a Group 4 element.
(6) A compound constituting one or more particles selected from TiB ₂ and TiC and an iron alloy are dissolved to form droplets, and the droplets are rapidly cooled to crystallize the particles. forming a layer of iron alloy powder using iron alloy powder;
irradiating the layer of iron alloy powder with an energy beam having a first energy density to form a first region;
irradiating the layer of iron alloy powder with an energy beam having a second energy density greater than the first energy density to form a second region;
The method for manufacturing an integrally molded part according to any one of (3) to (5), characterized by comprising:
(7) The first energy density is 30 J/mm ³ or more and less than 100 J/mm ³ ,
The method for manufacturing an integrally molded part according to (6), wherein the second energy density is 100 J/mm ³ or more and 200 J/mm ³ or less.

According to the present invention, by controlling the content of particles having a Young's modulus of 210 GPa or more and an average particle size of 300 nm or less in the range of 10 to 30 vol%, the strength and rigidity of the integrally molded part can be controlled. Strength and rigidity can be improved.

(a) is an example of the particle size distribution of particles having a Young's modulus of 210 GPa or more and 600 GPa or less dispersed in the first region constituting the second embodiment, and (b) is a schematic diagram of the structure of the second embodiment. be. FIG. 3 is an explanatory diagram of the manufacturing process of iron alloy powder according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the apparatus which implements the gas atomization method which manufactures the iron alloy powder based on this invention. FIG. 7 is a diagram showing the particle size distribution of particles (hard particles) contained in the first region and the second region of the second embodiment. It is a schematic explanatory diagram of a destructive test. FIG. 2 is a schematic explanatory diagram of a method for measuring Vickers hardness (Hv). It is a front view and a top view of a tensile test piece used for a destructive test. It is a schematic diagram of the measurement surface of Vickers hardness of a 1st area|region and a 2nd area|region.

Hereinafter, the integrally molded part of the present invention, the iron alloy powder for forming the integrally molded part, and the method for manufacturing the integrally molded part will be described in detail. "%" with respect to elements means mass % unless otherwise specified. Moreover, the particle size means the diameter of the relevant particle unless otherwise specified.

[Integrated molded parts]
(First embodiment)
The integrally molded part of the first embodiment is made of an iron-based composite material in which particles having a Young's modulus of 210 GPa or more are dispersed in a matrix made of an iron alloy. Examples of the iron alloy include carbon steel, low alloy steel, carbon steel for mechanical structures, nickel chromium steel, nickel molybdenum steel, chromium steel, chromium molybdenum steel, manganese steel, manganese chrome steel, high carbon chromium steel, and the like.

Particles with a Young's modulus of less than 210 GPa have a Young's modulus lower than that of the base material, and no improvement in rigidity as a composite material can be expected. Examples of the particles having a Young's modulus of 210 GPa or more include carbides and borides of group 4a and 5a elements, particularly particles containing TiB ₂ , TiC, or two or more of their compounds (hereinafter referred to as "composite compounds"). It is preferable to use particles (referred to as "particles").

When the volume fraction of the particles is less than 10%, they often precipitate at the grain boundaries of the iron matrix phase, increasing the possibility of brittle fracture. Moreover, if the volume fraction of the particles is 30% or more, the melting point becomes high and it becomes difficult to control the particle size. Therefore, it is preferable that the particles are dispersed in an amount of 10 to 30 vol% in the iron alloy. Furthermore, since particles with a particle size of more than 500 nm tend to act as starting points for destruction, the amount of particles with a particle size of more than 500 nm among the particles is 1 vol % or less.

The particles have an average particle size of 300 nm or less. When the average particle size of particles having a Young's modulus of 210 GPa or more is 300 nm or more, the average particle size after solidification increases due to aggregation. Therefore, the coarse particles act not as a reinforcing mechanism but as a starting point for fracture, resulting in a decrease in the overall mechanical properties.

(Second embodiment)
The second embodiment is an integrally molded part of an iron alloy in which particles having a Young's modulus of 210 GPa or more and 600 GPa or less are dispersed, and the first region has an average Vickers hardness of 200 Hv or more, and the first region has an average Vickers hardness of 150 Hv or more and and a second region whose hardness is less than the average Vickers hardness of the first region.

If the Vickers hardness is 150 Hv or higher and sufficiently high, the effect can be exhibited, but if the Vickers hardness of the modeling material is less than 150 Hv, the energy beam modeling conditions are not sufficient and pores are the starting point of fracture. becomes.

When the Young's modulus of the particles contained in the first region and the second region exceeds 600 GPa, minute cracks may occur at the interface between the particles and the base material. In such a case, despite the existence of an intensity distribution, there is a risk that destruction will occur even from regions with relatively high strength. From the viewpoint of controlling the starting point of fracture, the Young's modulus of the particles in the first region and the second region is preferably 210 GPa or more and 600 GPa or less.

The particles dispersed in each of the first region and the second region may be carbides or borides of group 4a and 5a elements, similar to the particles in the first embodiment. Further, the particles are contained in the integrally molded part in an amount of 10 to 30 vol% based on the iron alloy.

Note that the matrix made of iron alloy in the first region and the second region can be made of the same iron alloy as the matrix made of iron alloy in the first embodiment.

Further, in the second region, the average Vickers hardness of the integrally molded part is 150 Hv or more and less than the average Vickers hardness of the first region.

In the first region, the value obtained by subtracting the volume fraction of particles with a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles with a particle size of 1 nm or more and less than 300 nm is equal to the value of the particle size of 1 nm or more in the second region. It is preferably larger than the value obtained by subtracting the volume fraction of particles having a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles less than 300 nm. More preferably, the difference in volume fraction is 10% or more, and the effect becomes significant.

By configuring the first region and the second region in this way, the second region has a larger particle size, specifically, a volume fraction occupied by particles with a size of 300 nm or more and 500 nm or less, compared to the first region. As a result, the fatigue life becomes lower than that in the first region. Therefore, the second region is more likely to be destroyed than the first region. FIG. 1(a) shows an example of the particle size distribution of the particles in the above-described preferred first region. FIG. 1(b) is a schematic diagram of the particle size distribution in the first region and the second region having the above-described preferable particle size distribution.

The second embodiment makes it possible to control the origin of failure of the integrally molded part and to protect the parts that are subject to destructive damage that are present inside the structure. For example, by applying the second embodiment to a reinforced component such as a robot skeleton, the starting point of destruction can be controlled to avoid destructive damage to the inside of the structure.

[Iron alloy powder]
The integrally molded part according to the present invention can be manufactured by sintering iron alloy powder containing particles having a Young's modulus of 210 GPa or more. Examples of the iron alloy include carbon steel, low alloy steel, carbon steel for mechanical structures, nickel chromium steel, nickel molybdenum steel, chromium steel, chromium molybdenum steel, manganese steel, manganese chrome steel, high carbon chromium steel, and the like. Further, as the particles contained in the iron alloy powder, carbides and borides of group 4a and 5a elements can be exemplified, and it is particularly preferable to use TiB ₂ , TiC, or composite compound particles thereof. Moreover, it is preferable that the particles contained in the iron alloy powder have a Young's modulus of 600 GPa or less and an average particle size of 300 nm or less.

The iron alloy powder according to the present invention includes a step of melting a compound and an iron alloy constituting particles having a Young's modulus of 210 GPa or more to form droplets, and rapidly cooling the droplets to prevent the particles from agglomerating. It can be manufactured by a step of crystallizing the particles. FIG. 2 is an explanatory diagram of the manufacturing process of iron alloy powder according to the present invention. Moreover, such a manufacturing process can be implemented by the gas atomization method shown in FIG.

[Method for manufacturing integrally molded parts according to the present invention]
The integrally molded part according to the present invention can be manufactured using a metal 3D printer that is capable of manufacturing complex shapes with high precision. A metal 3D printer is one of additive manufacturing technologies that forms a target object based on 3D data created with CAD or the like. In metal 3D printers, a layer of metal powder is irradiated with energy beams such as lasers or electron beams to melt, cool, and sinter, and this process is repeated until the desired object is obtained.

For example, a method for manufacturing an integrally molded part according to the present invention will be explained by taking a laser sintering lamination method using a metal 3D printer as an example. In this case, the energy beam is a laser beam, and the energy density is expressed as laser energy [J/mm ³ ] per unit volume of the irradiated area. Further, laser scanning is realized using a scanning optical system including a galvanometer mirror and the like.

First, a layer of iron alloy powder according to the present invention is formed (step 1). A base material is placed on a base material mounting table that can be raised and lowered of a metal 3D printer, and a layer of iron alloy powder is formed on the base material to a predetermined thickness.

Next, the layer of iron alloy powder is irradiated with an energy beam having a predetermined energy density while scanning (Step 2). Here, according to the data of the 3D model of the integrally molded part to be formed, a portion corresponding to the first region is irradiated with an energy beam having a first energy density to form the first region. On the other hand, a portion corresponding to the second region is irradiated with a laser having a second energy density to form the second region. Note that both the first region and the second region do not necessarily exist in one layer of iron alloy powder. Moreover, the energy density can be controlled by adjusting the laser output [W], adjusting the laser scanning speed, or both. After the required laser irradiation is completed, unmelted iron alloy powder is removed by air blasting.

Next, the base material mounting table is lowered by a predetermined height to form the next layer of iron alloy powder (Step 3).
Repeat step 2 above. At this time, the energy density is controlled to be the first or second energy density determined depending on the part according to the data of the 3D model.
Thereafter, steps 2 and 3 are repeated a required number of times to form an integrally molded part.

Through the step 2, the agglomeration state of particles contained in the iron alloy powder can be controlled in the first region and the second region using the iron alloy powder according to the present invention. FIG. 4 is a diagram illustrating the effects of the steps 2 and 3, in which the agglomeration state of particles having a Young's modulus of 210 GPa or more is changed in the first region and the second region, respectively. By making the second energy density larger than the first energy density, the second region remains in a molten state for a longer time than the first region, so that stirring caused by Marangoni convection, etc. As a result, the rate of particle aggregation is greater in the area irradiated with the second energy density, and the second area thus obtained has a fatigue life lower than that of the first area. When it receives an impact exceeding a certain size, it will be destroyed before the first area.

Furthermore, the composite compound particles contained in the raw material powder may be remelted by energy irradiation. In that case, the average particle size of the composite compound particles in the integrally molded part may be smaller than the average particle size of the composite compound particles in the raw material powder.

Note that the first energy density is preferably 30 J/mm ³ or more and less than 100 J/mm ³ , and the second energy density is preferably 100 J/mm ³ or more and 200 J/mm ³ or less. A strength distribution can be created by controlling the agglomeration state of particles contained in the iron alloy powder or the particle size of crystallized substances of the particles. Note that the energy density is appropriately selected within the above range depending on the type of particles so as not to completely dissolve the particles.

[Method for measuring particle size and average particle size]
Measurement of particle size is performed by the following method. A sample is cut out from a predetermined area of the integrally molded part, embedded in resin, and mirror-polished. When measuring the average particle size of the particles contained in the iron alloy powder used to manufacture the integrally molded part, the iron alloy powder is molded using a binder such as a resin, and the molded body is mirror-polished. do.

The mirror-polished portion is magnified using an FE-SEM until the grain size is observed, and the grain size is measured. The area of each particle in a field of view of 0.5 mm x 0.5 mm is determined, and the equivalent circular diameter is determined. Here, the lower limit of the yen-equivalent diameter to be measured is 1 nm, and the upper limit is not limited. Furthermore, assuming that each particle is spherical, the particle size is determined. Furthermore, the elemental composition of each particle is measured using SEM-EDS or the like to identify the type of particle. A method for measuring the Young's modulus of particles whose type has been identified in this manner will be described later.

In the case of the first embodiment, one observation area is arbitrarily selected from the integrally molded part, and the mirror-polished observation surface obtained as described above is observed. Ten visual fields of 0.5 mm x 0.5 mm are arbitrarily selected on the observation surface, and the particle size of each particle is determined in each visual field as described above. The arithmetic mean of the number of determined grain sizes over the entire visual field of the ten selected locations is taken as the overall average grain size.

In the case of the second embodiment, one observation area is selected from each of the first area and the second area. For each selected observation area, the mirror-polished observation surface obtained as described above is observed. Ten visual fields of 0.5 mm x 0.5 mm are arbitrarily selected on the observation surface, and the particle size of each particle is determined in each visual field as described above. The arithmetic mean of the number of determined grain sizes over the entire visual field of the ten selected locations is taken as the average grain size of each of the first region and the second region. Further, the average particle diameters of the first region and the second region are weighted averaged using the volume fractions of the first region and the second region in the integrally molded part to obtain the overall average particle diameter.

[Method of measuring volume fraction of particles]
Since there is little difference between the area fraction and volume fraction obtained by observing the cut surface, the volume fraction of the particles is measured by the following method. A sample is cut out from a predetermined area of the integrally molded part, embedded in resin, and mirror-polished. Using FE-SEM, expand until the particle size is observed, determine the area of each particle, determine the circle-equivalent diameter, and approximate it to a spherical shape, and consider it as a spherical particle with the diameter equal to the circle-equivalent diameter. . Here, the lower limit of the yen-equivalent diameter to be measured is 1 nm, and the upper limit is not limited. In a field of view of 0.5 mm x 0.5 mm, areas corresponding to particles included in a specific particle size range are added together to determine the area fraction of particles included in the specific particle size range in the field of view. A similar operation is applied to a plurality of fields of view of 0.5 mm x 0.5 mm, the average of the area fractions is determined, and the average of the area fractions is taken as the volume fraction of particles included in the specific particle size range.

In the case of the first embodiment, one observation area is arbitrarily selected from the integrally molded part, and the mirror-polished observation surface obtained as described above is observed. On the observation surface, 10 visual fields of 0.5 mm x 0.5 mm are arbitrarily selected, and in each visual field, the area fraction of all particles having a circular equivalent diameter of 1 nm or more is determined. The average value of the area fraction is determined over the entire field of view of the ten selected locations, and this is taken as the volume fraction of particles in the integrally molded part.

In the case of the second embodiment, one observation area is selected from each of the first area and the second area. For each selected observation area, the mirror-polished observation surface obtained as described above is observed. Ten visual fields of 0.5 mm x 0.5 mm are arbitrarily selected on the observation surface, and the particle size of each particle is determined in each visual field as described above. For the first region, the area fraction occupied by particles in the specific particle size range is determined for the entire field of view of the ten selected locations, and the average value of this area fraction is calculated as follows: Let it be the volume fraction occupied. For the second region as well, the volume fraction of particles in the specific particle size range is determined in the same manner as for the first region.

[Method of measuring Vickers hardness]
Vickers hardness is measured according to JIS7735. 10 kgf was used as the test weight. A sample is cut out from a predetermined area of an integrally molded part, embedded in resin, and mirror-polished.

In the case of the first embodiment, one observation area is arbitrarily selected from the integrally molded part, and the Vickers hardness of the mirror-polished surface obtained as described above is measured. Randomly select 10 areas of 0.5 mm x 0.5 mm from the mirror-polished surface, measure 5 arbitrary points within each of the 10 selected areas, and calculate the average of all measured values. The value is the hardness of the integrally molded part.

In the case of the second embodiment, one measurement area is selected from each of the first area and the second area. For each of the selected measurement areas, arbitrarily select 10 areas of 0.5 mm x 0.5 mm on the mirror-polished surface obtained as described above, and Measure at 5 points. In each of the first region and the second region, the average value of all the measured values obtained is defined as the hardness of the first region and the second region, respectively.

In the case of the second embodiment, the second region is the starting point of destruction. Therefore, a destructive test may be performed to form a fractured surface as shown in FIG. 8, and the vicinity thereof may be used as the second region of the molded part. More specifically, as shown in FIG. 8, a fractured surface is formed, and a plane perpendicular to the longitudinal direction (the "first" As described above, 10 areas of 0.5 mm x 0.5 mm were arbitrarily selected from the Vickers hardness measurement surface of 2 areas, and measurements were taken at 5 arbitrary points within each of the 10 selected areas. , the average value of all measured values may be used as the hardness of the second region. Incidentally, the above-mentioned "Vickers hardness measurement surface of the second region" may be used as a region for measuring the particle size of the particles, the average particle size of the particles, and the volume fraction of the particles in the second region.

Further, the first region is a region that is more difficult to destroy than the second region. Therefore, a cut plane perpendicular to the longitudinal direction of the molded part is cut out from a portion spaced a predetermined length away from the fractured surface in the direction of the non-destructive region, and the average Vickers hardness of the cut plane is measured. By repeating such measurement of the average Vickers hardness at predetermined intervals from the fracture surface in the direction of the non-destructive area, a cut having an average Vickers hardness that is higher than the Vickers hardness of the second area and 150 Hv or more can be obtained. A plane may be specified, and the vicinity of the specified cut plane may be set as the first region of the molded part.

When specifying the first region, the average Vickers hardness of the cut surface is measured in the same manner as the hardness of the second region. Specifically, as described above, 10 areas of 0.5 mm x 0.5 mm were arbitrarily selected from the vertical cut plane, and measurements were taken at 5 arbitrary points within each of the 10 selected areas. The average value of all measured values is calculated as the average Vickers hardness of the cut surface. Such average Vickers hardness measurements are repeated to identify a cut surface having an average Vickers hardness higher than the Vickers hardness of the second region and 150 Hv or more, and the vicinity of the identified cut surface is subjected to the molding. It may also be the first area of the component. Note that the cut plane specified as the first region may be used as a region for measuring the particle diameter, average particle diameter, and volume fraction of particles in the first region.

FIG. 8 shows an example in which the first region can be specified within a range of 5.5 to 6.5 mm in the longitudinal direction of the molded part from the "Vickers hardness measurement surface of the second region."

[Method for measuring Young's modulus of particles]
The Young's modulus of the particles is the Young's modulus measured by the resonance method specified in JIS-Z-2280 on a test piece produced by sintering the powder. For example, the Young's modulus of TiB ₂ particles is measured using a resonance method specified in JIS-Z-2280 using a test piece obtained by sintering TiB ₂ powder with a purity of 99.99% or higher.

Examples of the present invention will be shown below, but these are provided for better understanding of the present invention, and are not intended to limit the present invention.

The iron alloy powder shown in Table 1 was produced using a gas atomization device having the structure shown in FIG. The matrix portion excluding particles contained in the iron alloy powder is composed of 90% or more Fe. Iron alloy powder No. Nos. 1 to 8 were molded into a certain shape by compaction using a resin as a binder, and the molded bodies were mirror-polished. For these compacts, the mirror-polished portions were examined using FE-SEM using the method described above to obtain iron alloy powder No. The average particle diameter of each particle in Table 1 contained in each of Nos. 1 to 8 was measured. In addition, as mentioned above, the Young's modulus of the particles is determined based on the JIS-Z-2280 standard for test pieces obtained by sintering particles (particle compound purity: 99.99%) contained in each iron alloy powder. This is the value measured using the resonance method.

Using the iron alloy powder in Table 1, an integrally molded part having the structure shown in Table 2 was manufactured using a 3D printer under the following conditions.
Energy density of energy ray irradiation when forming the first region: 50 J/mm ³
Energy density of energy ray irradiation when forming the second region: 150 J/mm ³
The iron alloy powder was classified using a sieve, and the iron alloy powder with a diameter of 10 μm to 200 μm was used.

Each integrally molded part No. shown in Table 2. A destructive test was conducted using the method shown in FIG. 5, and the fractured locations were measured. The results are shown in Table 3. The shape of the tensile test piece was as shown in FIG. 7, with the parallel portion having a thickness of 1 mm, a length of 25 mm, and a width of 12 mm. In the integrally molded parts No. 1 and No. 2, the second region was formed at a position 5.5 mm to 6.5 mm from the end of the parallel portion. The tensile test conditions were conducted in accordance with JIS Z2241.

[Measurement of Young's modulus of integrally molded parts]
The Young's modulus of each integrally molded part was measured by the resonance method specified in JIS-Z-2280. The test piece has a thickness of 1 mm, a length of 60 mm, and a width of 10 mm. Table 3 shows the measurement results of Young's modulus of each integrally molded part.

A destructive test is performed on each integrally molded part, and the sample, including the fractured part, is embedded in resin and mirror-polished. As shown in FIG. 6, the region including the fracture site and a plurality of regions adjacent thereto were enlarged using FE-SEM until the particle size was observed, and the particle size was measured. Measurement of each particle diameter and average particle diameter of particles in a field of view of 0.5 mm x 0.5 mm, and measurement of the volume fraction of each particle size range of particle diameters of 1 nm or more and less than 300 nm and 300 nm or more and 500 nm or less are as described above. I did it the way I did.

Further, the Vickers hardness of each region was measured according to the method described above, and the test force was all set to 10 kgf. As the Vickers hardness of the first region of the molded part, the Vickers hardness near the fracture surface of the fractured part was measured. As shown in FIG. 8, the Vickers hardness of the first region is determined by cutting out a plane perpendicular to the longitudinal direction that is 0.1 mm away from the fracture surface in the longitudinal direction of the molded part in the direction of the non-destructive region. The Vickers hardness was measured as described above, and the average value was taken as the average value. Further, as shown in FIG. 8, the Vickers hardness of the second region of the molded part is 5.5 mm to 6.5 mm away from the fracture surface in the longitudinal direction of the molded part in the direction of the non-destructive area. A perpendicular surface was cut out, and the Vickers hardness was measured from the perpendicular surface as described above, and the average value was taken as the average value.

Integrally molded part no. 6 and no. No. 14 contains 12 vol% of particles having a Young's modulus of 210 GPa or more and an average particle size of 285 nm, and has high Young's modulus and strength. Integrally molded part no. The particles contained in the iron alloy powder (No. 5 in Table 1) used to manufacture No. 12 have a Young's modulus of 210 GPa or more, but the average particle size exceeds 300 nm, making it possible to form an integrally molded part. No. No. 12 had insufficient strength because the particles contained in the raw material powder were coarse and the particles contained in the integrally molded part were coarse. Integrally molded part no. In No. 13, the particles contained in the iron alloy powder (No. 7 in Table 1) have a Young's modulus of 210 GPa or more and an average particle size of 300 nm or less, but the content of particles in the iron alloy powder is 30 vol% or more. The particles contained in the integrally molded part became coarse. Therefore, the strength of the integrally molded part was not sufficient.

Integrally molded part no. 1, 2, and 11, as shown in Table 2, have a region 1 and a region 2 that meet the requirements of the present invention. As a result of the destructive test, as shown in Table 3, only area 2 was destroyed. Integrally molded part no. No. 3 has a region 1 with a relatively high average hardness, but the average hardness of this region 1 was less than 200 Hv, and fracture occurred in region 1 and region 2 in some cases.

Integrally molded part no. No. 4 is an invention example containing 12 vol% of particles having a Young's modulus of 210 GPa or more and an average particle size of 300 nm or less. Integrally molded part no. 4 has a region 1 and a region 2, but as a result of a destructive test, there were cases where destruction occurred in region 1 and cases where destruction occurred in region 2. No. This is because, in No. 4, the Young's modulus of the particles is too high compared to the Young's modulus of the whole part, so that regardless of regions 1 and 2, destruction occurs at the boundary between the particles and the matrix.

Integrally molded part no. Sample No. 5 had an average particle diameter of more than 300 nm, and therefore sufficient strength could not be obtained. Integrally molded part no. No. 5 has Region 1 with a relatively high average hardness, but fracture occurred in Region 1 in some cases and in Region 2 in other cases. Integrally molded part no. 5 is because the average particle size of particles in both region 1 and region 2 is large.

Integrally molded part no. No. 7 does not form an integrally molded part because not enough energy is applied to melt the particles.
Integrally molded part no. 8, under the manufacturing conditions, the energy density of the laser is too high in both regions 1 and 2, and the average particle size of the particles becomes too large, causing fracture to occur in region 1 and region 2. In some cases, the strength is not sufficient.
Integrally molded part no. No. 9 has a small volume fraction of particles contained in the iron alloy powder, and the difference in hardness between region 1 and region 2 is small. Therefore, there were cases where destruction occurred in area 1 and cases where it occurred in area 2. Integrally molded part no. Although No. 9 has a small average particle size, the strength is not sufficient because the number of particles is small.
Integrally molded part no. No. 10 has a large volume fraction of particles contained in the iron alloy powder, and agglomeration of particles cannot be avoided. Therefore, the average particle size of the particles became large, and the fracture occurred in region 1 in some cases and in region 2 in other cases.

From the measurement results of Vickers hardness at the fractured location, integrally molded part No. 1, which is an example of the invention, was found. 1, 2, and 11 were destroyed only in region 2, as shown in FIG. This indicates that the fracture origin of the integrally molded component of the present invention is controlled. On the other hand, integrally molded part No. 1, which is a comparative example. When we measured the Vickers hardness of the fracture points for Samples Nos. 3, 5, 8 to 10, we found that these comparative examples were also fractured in area 1, indicating that the fracture origin was not controlled.

The integrally molded part of the present invention, the iron alloy powder for forming the integrally molded part, and the integrally molded part have a complex shape formed with precision, and the integrally molded part has a controlled fracture origin; It is possible to provide an iron alloy powder for forming the integrally molded part and a method for manufacturing the integrally molded part.

Claims (7)

An integrally molded part of an iron alloy in which one or more particles selected from TiB ₂ , TiC, and WC are dispersed, and the average particle size of the particles is 300 nm or less,
The volume fraction of the particles is 10 vol% or more and 30 vol% or less,
The volume fraction of particles having a particle size of more than 500 nm among the particles is 1 vol% or less,
The average particle diameter of the particles is determined by selecting 10 fields of view of 0.5 mm x 0.5 mm from the cross section of the integrally molded part using FE-SEM, and selecting one of the TiB ₂ , TiC, and WC in each field of view. Determine the area of each of the selected one or more types of particles, calculate the diameter in terms of a circle from the area, and calculate the area of the ten selected particles for particles whose diameter in terms of a circle is 1 nm or more among the particles. Calculated by arithmetic averaging over the number of circle equivalent diameters over the entire field of view,
The volume fraction of the particles is determined by adding up the area of the particles in each of the fields of view for particles with a circular equivalent diameter of 1 nm or more, and calculating the area fraction of the particles in the entire field of view of the 10 selected locations. Calculated by averaging the area fractions of the particles over
An integrally molded part characterized by: The integrally molded part according to claim 1, wherein the integrally molded part is a sintered body. An integrally molded part of an iron alloy in which one or two types of particles selected from TiB ₂ and TiC are dispersed, and has a first region and a second region,
The average Vickers hardness of the first region is more than 200 Hv,
The integrally molded part according to claim 1 or 2, wherein the second region has an average Vickers hardness of 150 Hv or more and 200 Hv or less. In the first region, the value obtained by subtracting the volume fraction of particles with a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles with a particle size of 1 nm or more and less than 300 nm is:
4. The second region is larger than the value obtained by subtracting the volume fraction of particles with a particle size of 300 nm or more and 500 nm or less from the volume fraction of particles with a particle size of 1 nm or more and less than 300 nm in the second region. One-piece molded part. The integrally molded part according to any one of claims 1 to 4, wherein the particles are a boride or carbide of a Group 4 element. An iron alloy powder obtained by dissolving one or more particles selected from TiB ₂ and TiC and an iron alloy to form droplets, and rapidly cooling the droplets to crystallize the particles. forming a layer of iron alloy powder using
irradiating the layer of iron alloy powder with an energy beam having a first energy density to form a first region;
irradiating the layer of iron alloy powder with an energy beam having a second energy density greater than the first energy density to form a second region;
A method for manufacturing an integrally molded part according to any one of claims 3 to 5, characterized in that the method comprises: The first energy density is 30 J/mm ³ or more and less than 100 J/mm ³ ,
The method for manufacturing an integrally molded part according to claim 6, wherein the second energy density is 100 J/mm ³ or more and 200 J/mm ³ or less.

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