WO2020110891A1 - Powder for shaping - Google Patents

Powder for shaping Download PDF

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Publication number
WO2020110891A1
WO2020110891A1 PCT/JP2019/045591 JP2019045591W WO2020110891A1 WO 2020110891 A1 WO2020110891 A1 WO 2020110891A1 JP 2019045591 W JP2019045591 W JP 2019045591W WO 2020110891 A1 WO2020110891 A1 WO 2020110891A1
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Prior art keywords
powder
less
present
modeling
carbide
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PCT/JP2019/045591
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French (fr)
Japanese (ja)
Inventor
功一 坂卷
範英 福澤
孝之 坂本
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日立金属株式会社
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Priority to JP2020557618A priority Critical patent/JPWO2020110891A1/en
Publication of WO2020110891A1 publication Critical patent/WO2020110891A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/12—Metallic powder containing non-metallic particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt

Definitions

  • the present invention relates to a molding powder for producing high-speed tool steel applied to forging tools such as dies and punches, dies, and the like.
  • hot tool steels such as SKD8 according to JIS and high speed tool steels such as SKH51 according to JIS having high high temperature strength are used for tools such as punches and dies for hot precision press working.
  • This hot work tool steel has a low C (carbon), and sometimes suffers fatigue, wear, and damage. Further, the above high-speed tool steel has a problem that cracks and heat cracks are likely to occur.
  • Patent Document 1 proposes a high-speed tool steel that has improved normal temperature and high temperature strength, toughness, and excellent heat crack resistance.
  • Patent Document 1 is a useful technique in that it can provide stable tool performance with high toughness and little variation.
  • ingot making such as casting or remelting process of a steel ingot is performed, and this ingot is subjected to hot plastic working such as slabbing and finishing, and then a tool or a metal. Since it is molded into a mold, it requires a great number of man-hours for processing.
  • the high-speed tool steel disclosed in Patent Document 1 coarse primary carbides are formed in the ingot due to segregation of solidification during cooling during the above-mentioned ingot making.
  • the presence of this primary carbide promotes the generation and development of cracks, and thus reduces toughness and heat crack resistance.
  • the high speed tool steel disclosed in Patent Document 1 requires soaking at 1200 to 1300° C. for 10 to 20 hours in order to obtain a uniform structure in which precipitated carbide is finely dispersed.
  • the above-mentioned heat treatment called soaking leads to the problem of increased costs due to an increase in manufacturing man-hours. Even if the high-speed tool steel is soaked to obtain a forging tool such as a die or a punch or a die, coarse carbides of 1 ⁇ m or more are deposited depending on the conditions of the quenching and tempering treatments in the subsequent process. In some cases, the toughness and heat crack resistance may be reduced.
  • the object of the present invention is suitable for additive processing to make powder into a near net shape, and a shaping powder capable of producing a high-speed tool steel containing no coarse carbide even if the soaking that was necessary for ingot making is omitted. Is to provide.
  • the present invention is configured as follows to solve the above problems.
  • the molding powder of the present invention is, in mass %, C: 0.4 to 0.9%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 4.0 to 6.0%, One or two of W and Mo are (1/2W+Mo) and 1.5 to 6.0% (however, W: 3.0% or less), and one or two of V and Nb are (V+Nb). It has a composition of 0.5 to 3.0% with the balance being Fe and inevitable impurities.
  • the powder for modeling of the present invention preferably contains Co in an amount of 5% by mass or less.
  • the molding powder of the present invention preferably has less than one carbide having a maximum length of 0.1 ⁇ m or more in the cross section of the powder.
  • the present invention can provide a modeling powder that does not contain coarse carbides even if the soaking that is necessary for ingot making is omitted.
  • the modeling powder of the present invention for example, even when applied to the powder bed fusion bonding method or the directed energy deposition method, coarse particles are less likely to be generated, soaking can be omitted, that is, in an easy process.
  • a high speed tool steel having excellent properties can be obtained. Therefore, the present invention is a useful technique for producing high speed tool steel such as dies and punches having high toughness and high heat crack resistance, and forging tools such as punches and dies.
  • the scanning electron micrograph of the powder for modeling of this invention example 2. 3 is a scanning electron micrograph of a layered model produced using the modeling powder of Example 2 of the present invention.
  • the modeling powder of the present invention is a powder used for an additional process such as a powder bed fusion bonding method or a directed energy deposition method for converting the powder into a near net shape.
  • the present invention does not need to undergo hot plastic working such as lumping and finishing, which were required in the conventional ingot making, and thus can contribute to shortening the working man-hour.
  • the modeling powder of this invention is comprised by the following component compositions.
  • the molding powder of the present invention is, in mass %, C: 0.4 to 0.9%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 4.0 to 6.0%, One or two of W and Mo are (1/2W+Mo) and 1.5 to 6.0% (however, W: 3.0% or less), and one or two of V and Nb are (V+Nb). 0.5 to 3.0%, the balance consisting of Fe and inevitable impurities.
  • C combines with carbide forming elements such as Cr, W, Mo, V and Nb to form a hard double carbide, and is effective in improving the wear resistance required as a tool. Further, C has an effect of strengthening the base by forming a solid solution in a part of the base. At this time, by setting C to 0.4% or more, the hardness required as a tool can be secured. For the same reason as above, C is preferably 0.5% or more. On the other hand, when C is 0.9% or less, it is possible to prevent the amount of carbide from becoming excessive and improve the toughness. For the same reason as above, C is preferably 0.7% or less. It is more preferably 0.6% or less.
  • Si can be prevented from decreasing in toughness by making it 1.0% or less. Further, for the same reason as above, Si is preferably 0.5% or less. It is more preferably 0.3% or less, still more preferably 0.2% or less. Then, Si is preferably contained in an amount of 0.1% or more as a deoxidizing material.
  • Mn By setting Mn to 1.0% or less, machinability can be improved. It is preferably 0.8% or less, and more preferably 0.6% or less. Further, Mn is preferably contained in an amount of 0.3% or more in order to improve hardenability. It is more preferably 0.4% or more.
  • Cr combines with C to form a carbide, which improves wear resistance and contributes to improvement of hardenability. Therefore, in the present invention, Cr is set to 4.0% or more. This makes it possible to optimize the amount of carbide formed and improve wear resistance and hardenability. For the same reason as above, Cr is preferably 4.1% or more. On the other hand, when Cr is 6.0% or less, the formation of coarse carbides can be suppressed and the toughness can be improved. For the same reason as above, Cr is preferably 5.0% or less. It is more preferably 4.8% or less, still more preferably 4.5% or less.
  • W and Mo can combine with C to form a carbide, and can form a solid solution in the matrix to increase the heat treatment hardness and improve wear resistance.
  • the Ms point can be raised and the retained austenite after quenching can be reduced, contributing to the improvement of hardness.
  • the above (1/2W+Mo) is preferably 2.0% or more. It is more preferably 2.3% or more, still more preferably 2.5% or more. Further, by reducing the content of one or two of W and Mo in (1/2W+Mo) to 6.0% or less, it is possible to suppress a decrease in machinability and toughness.
  • the above (1/2W+Mo) is preferably 5.0% or less. It is more preferably 4.0% or less, still more preferably 3.0% or less. Note that W is 3.0% or less from the viewpoint of ensuring mechanical strength. It is preferably 2.4% or less, and more preferably 1.8% or less. Further, it is preferably 1.0% or more, more preferably 1.5% or more.
  • V and Nb form carbides to improve wear resistance and seizure resistance. Further, V and Nb form a solid solution in the matrix during quenching and precipitate fine carbides that are hard to agglomerate during tempering, thereby increasing the softening resistance in the high temperature region and giving high temperature proof stress. Further, V and Nb improve the toughness by refining the crystal grains, raise the A1 transformation point, and improve the heat crack resistance together with the excellent high temperature proof stress. Further, Nb enhances softening resistance and high temperature strength, and suppresses coarsening of crystal grains during quenching. On the other hand, if the amount of Nb is too large, the Ms point is lowered and the retained austenite after quenching is increased, so that the hardness is lowered.
  • V and Nb is (V+Nb) 0.5 to 3.0%. It is preferably 0.7% or more, more preferably 0.9% or more, still more preferably 1.1% or more. Further, it is preferably 2.4% or less, more preferably 1.5% or less, still more preferably 1.3% or less.
  • the powder for modeling of the present invention may contain Co in addition to the above elements.
  • Co is preferably 0.3% or more, which forms a protective oxide film that is extremely dense and has good adhesion at the time of temperature rise during tool use to reduce metal contact with the mating material and reduce surface temperature. The rise is reduced and excellent wear resistance can be imparted.
  • Co has a heat insulating effect due to the formation of the above-mentioned protective oxide film, and can also improve heat crack resistance due to the protective action, and has an effect of suppressing generation of crack starting points.
  • the toughness may be reduced, so Co is preferably 5.0% or less. It is more preferably 3.5% or less, still more preferably 2.0% or less, still more preferably 1.0% or less. Further, it is preferably 0.3% or more, more preferably 0.5% or more, still more preferably 0.7% or more.
  • the modeling powder of the present invention may contain Ni in addition to the above elements.
  • Ni together with the above C, Cr, Mn, Mo, W, etc., imparts excellent hardenability, forms a martensite-based structure, and improves the intrinsic toughness of the matrix. % Or more is preferable.
  • Ni is preferably 1.00% or less, whereby the A1 transformation point is optimized, the tempering hardness is suppressed low, and the machinability can be improved. It is more preferably 0.80% or less, still more preferably 0.40% or less, still more preferably 0.20% or less.
  • the remainder of the powder for modeling of the present invention is Fe and unavoidable impurities.
  • the carbide contained in the modeling powder may remain in the modeled product without being melted depending on the heat input condition during modeling. Further, if the carbide contained in the modeling powder is finer, the carbide of the molded article tends to be finer, and the toughness and heat crack resistance can be improved. Therefore, the modeling powder of the present invention preferably has less than one carbide having a maximum length of 0.1 ⁇ m or more in the cross section of the powder.
  • the molded product using the molding powder of the present invention has a very high cooling rate in the solidification process, as compared with ingot casting such as ingot casting or continuous casting, so that the primary carbide formed becomes fine. Therefore, even if soaking at a high temperature of 1200 to 1300° C. for 10 to 20 hours described above for a long time is omitted, it is possible to decompose the primary carbides by a heat treatment such as annealing or quenching.
  • the powder for modeling of the present invention can be produced by, for example, a gas atomizing method, a water atomizing method, a disk atomizing method, a plasma atomizing method, a rotating electrode method, or the like.
  • the gas atomization method is capable of using scrap metal or metal crude material as a melting raw material, and it is necessary to prepare a raw material having a desired composition and shape in advance. It becomes possible to manufacture at an inexpensive cost as compared with the method and the like. Therefore, it is preferable as a method for producing the molding powder of the present invention.
  • the gas atomizing method is a method in which a molten raw material prepared to have a desired composition is heated to a temperature equal to or higher than its melting point by high frequency induction heating and melted, and then argon gas or nitrogen is applied to molten metal flown out through pores.
  • This is a method in which a molten metal is finely pulverized by injecting an inert gas such as gas and rapidly solidified to obtain a powder.
  • nitrogen gas can be used from the viewpoint of finely controlling the carbide crystallized in the powder structure.
  • the modeling powder of the present invention preferably has a 50% particle size (hereinafter referred to as “D50”) of a volume-based cumulative particle size distribution of 10 to 250 ⁇ m.
  • D50 50% particle size
  • the cumulative particle size distribution of the molding powder of the present invention is represented by a cumulative volume particle size distribution, and its D50 is represented by a value measured by a laser diffraction/scattering method defined by JIS Z8825.
  • the particle size of the powder for modeling of the present invention may be adjusted by sieving classification using a mesh, airflow classification or the like according to the molding method in which the powder is used.
  • the modeling powder used in the powder bed fusion bonding method using a laser beam removes coarse powder that is difficult to melt in order to narrow the range of heat influence as much as possible while melting the powder by the laser beam that serves as a heat source. There is a need. Further, in order to obtain the optimum fluidity for ensuring the layability of the powder, it is necessary to remove the fine powder having high adhesiveness. Therefore, when the molding powder of the present invention is applied to the powder bed fusion bonding method, it is preferable to adjust D50 in the range of 10 to 53 ⁇ m.
  • the metal powder used in the directed energy deposition method using a laser beam needs to remove coarse powder that is difficult to melt because the powder is melted by the laser beam serving as a heat source.
  • D50 is preferably 75 to 250 ⁇ m.
  • each metal crude material so as to have the composition shown in Table 1 After preparing each metal crude material so as to have the composition shown in Table 1, it is charged into a high-frequency induction melting furnace and melted, and atomized powder is obtained by crushing the molten metal with argon gas having a gas pressure of 3.0 MPa. It was The atomized powder thus obtained is classified by sieving using a metal mesh sieve having an opening of 53 ⁇ m to remove finer particles than 53 ⁇ m, and then sieving using a metal mesh sieve having an opening of 106 ⁇ m. , 106 ⁇ m, and powders for molding of Invention Example 1 and Invention Example 2 having a particle size of 53 ⁇ m to 106 ⁇ m were obtained.
  • the D50 of the above-mentioned molding powder was measured with a laser diffraction/scattering particle size distribution measuring device MasterSizer2000 manufactured by Malvern Instruments.
  • the measured D50 values were 84 ⁇ m in the present invention example 1 and 82 ⁇ m in the present invention example 2. From this, it was confirmed that the modeling powder as the example of the present invention was a powder suitable for the directed energy deposition method using a laser beam.
  • C was analyzed by an infrared absorption method, and elements other than C described in Table 1 were analyzed by ICP emission spectroscopy. From Table 1, in all the powders of the present invention, the analytical values of each element of C, Si, Mn, Cr, W, Mo, V, Nb, Ni and Co are within the specified range of the present invention. However, it was confirmed that after shaping with the powder of the present invention example, sufficient characteristics as high speed tool steel could be exhibited.
  • the set of each powder was heat-cured according to the general procedure for preparing a sample for microscopic observation so that the plurality of powders were arranged in a line on one surface.
  • the sample was prepared by buffing after embedding it in a hydrophilic resin.
  • These samples were corroded by Nital, and the secondary electron image of the cross-sectional structure was observed using a scanning electron microscope ULRTA55 manufactured by ZEISS. The results are shown in FIGS. 1 and 2.
  • none of the modeling powders of the present invention contained coarse carbide having a maximum length of 0.1 ⁇ m or more in the cross-sectional structure. This is because when the molding powder of the present invention is used for molding, it is not necessary to perform a soaking process in the manufacturing process, and it is possible to manufacture a high-speed tool steel containing few point carbides of 1 ⁇ m or more. It was confirmed that the powder was a molding powder.
  • Example 2 of the present invention additive manufacturing was carried out by the directed energy deposition method. Specifically, by using LASERTEC 65 3D manufactured by DMG MORI SEIKI on a plate made of SKD61 according to JIS while irradiating a laser heat source while supplying the modeling powder of Inventive Example 2, a linear bead By laminating, a layered product was produced. Then, this layered product was quenched at 1140°C and tempered at 560°C.
  • the structure of the cross section in the thickness direction of the tempered layered product obtained above was observed. Specifically, after embedding in a thermosetting resin so as to expose the cross section in the thickness direction of the layered product, the sample was prepared by buffing and corroded by Nital to prepare an observation sample. Then, this observation sample was observed using a scanning microscope VE-8800 manufactured by Keyence Corporation and an optical microscope. The results are shown in FIGS. 3 and 4. In the layered product obtained by using the powder for modeling of the present invention, point-like carbides indicated by arrows in FIG. 3 are confirmed from the observation result of the secondary electron image of the scanning electron microscope shown in FIG.
  • the point carbides had a maximum particle size of 0.8 ⁇ m observed in a range of 4750 ⁇ m 2 at a magnification of 5000 times.
  • the layered product obtained by using the modeling powder of the present invention has a dot shape with a particle size of 1 ⁇ m or more in the area of a magnification of 500 times and a diameter of 15 mm. No carbide was observed.
  • the shaping powder of the present invention can produce a high-speed tool steel with a small amount of point carbides of 1 ⁇ m or more by using a laser beam, even if the soaking that is required for ingot making is omitted. It was confirmed that the powder was suitable for the directed energy deposition method.

Abstract

Provided is a powder for shaping that is suitable for use in additional processing for forming a powder into near net shapes and that is capable of producing a high-speed tool steel containing no coarse carbides, even when soaking, which has been necessary for ingot making, is omitted. The powder for shaping has a composition which contains, in terms of mass%, 0.4-0.9% C, up to 1.0% Si, up to 1.0% Mn, 4.0-6.0% Cr, 1.5-6.0% W and/or Mo in terms of 1/2W+Mo (W being up to 3.0%), and 0.5-3.0% V and/or Nb in terms of V+Nb, with the remainder comprising Fe and unavoidable impurities.

Description

造形用粉末Modeling powder
　本発明は、例えば、ダイス、パンチ等の圧造工具や金型等に適用される高速度工具鋼を製造するための造形用粉末に関するものである。 The present invention relates to a molding powder for producing high-speed tool steel applied to forging tools such as dies and punches, dies, and the like.
　従来、熱間精密プレス加工用のパンチや金型等の工具には、高温強度の高いＪＩＳでいうＳＫＤ８等の熱間工具鋼や、ＪＩＳでいうＳＫＨ５１等の高速度工具鋼が使用されている。この熱間工具鋼は、Ｃ（炭素）が低く、へたり、摩耗や破損が生ずる場合があった。また、上記の高速度工具鋼は、割れやヒートクラックが発生しやすいという問題があった。 Conventionally, hot tool steels such as SKD8 according to JIS and high speed tool steels such as SKH51 according to JIS having high high temperature strength are used for tools such as punches and dies for hot precision press working. . This hot work tool steel has a low C (carbon), and sometimes suffers fatigue, wear, and damage. Further, the above high-speed tool steel has a problem that cracks and heat cracks are likely to occur.
　これらの問題点を解決するために、常温および高温強度と、靭性を改善して、かつ耐ヒートクラック性に優れた高速度工具鋼が、例えば、特許文献１で提案されている。 In order to solve these problems, for example, Patent Document 1 proposes a high-speed tool steel that has improved normal temperature and high temperature strength, toughness, and excellent heat crack resistance.
特開２００４－３０７９６３号公報JP 2004-307963 A
　特許文献１は、靭性が高く、且つ、そのばらつきが少ない、安定した工具性能を提供できるという点では有用な技術である。
　特許文献１に開示のある高速度工具鋼の製造方法では、鋼塊の鋳造または再溶解プロセスといったインゴットメイキングを行ない、このインゴットについて、分塊および仕上げという熱間での塑性加工を経て工具や金型に成形されるため、加工に多大な工数を要していた。 Patent Document 1 is a useful technique in that it can provide stable tool performance with high toughness and little variation.
In the method for producing a high-speed tool steel disclosed in Patent Document 1, ingot making such as casting or remelting process of a steel ingot is performed, and this ingot is subjected to hot plastic working such as slabbing and finishing, and then a tool or a metal. Since it is molded into a mold, it requires a great number of man-hours for processing.
　また、特許文献１に開示のある高速度工具鋼は、上記のインゴットメイキング中の冷却時における凝固の偏析により、インゴット中に粗大な一次炭化物が形成される。この一次炭化物が存在すると、クラックの発生、進展を助長するため、靭性や耐ヒートクラック性が低下する。
　そして、特許文献１に開示のある高速度工具鋼は、析出炭化物が微細に分散した均一な組織を得るために、１２００～１３００℃で１０～２０時間のソーキングを必要とする。 Further, in the high-speed tool steel disclosed in Patent Document 1, coarse primary carbides are formed in the ingot due to segregation of solidification during cooling during the above-mentioned ingot making. The presence of this primary carbide promotes the generation and development of cracks, and thus reduces toughness and heat crack resistance.
The high speed tool steel disclosed in Patent Document 1 requires soaking at 1200 to 1300° C. for 10 to 20 hours in order to obtain a uniform structure in which precipitated carbide is finely dispersed.
　上記のソーキングという熱処理は、製造工数の増大に伴うコストの上昇という問題に繋がる。また、ダイス、パンチ等の圧造工具や金型等を得るために、高速度工具鋼にソーキングを施しても、後工程の焼入れ、焼戻し処理の条件によっては、１μｍ以上の粗大な炭化物が析出する場合があり、靭性や耐ヒートクラック性を低下させる虞がある。 　The above-mentioned heat treatment called soaking leads to the problem of increased costs due to an increase in manufacturing man-hours. Even if the high-speed tool steel is soaked to obtain a forging tool such as a die or a punch or a die, coarse carbides of 1 μm or more are deposited depending on the conditions of the quenching and tempering treatments in the subsequent process. In some cases, the toughness and heat crack resistance may be reduced.
　本発明の目的は、粉末をニアネットシェイプにする付加加工に好適で、インゴットメイキングで必要であったソーキングを省略しても、粗大な炭化物を含まない高速度工具鋼を製造可能な造形用粉末を提供することである。 The object of the present invention is suitable for additive processing to make powder into a near net shape, and a shaping powder capable of producing a high-speed tool steel containing no coarse carbide even if the soaking that was necessary for ingot making is omitted. Is to provide.
　本発明は、上記の課題を解決するため、次のように構成される。
　本発明の造形用粉末は、質量％で、Ｃ：０．４～０．９％、Ｓｉ：１．０％以下、Ｍｎ：１．０％以下、Ｃｒ：４．０～６．０％、ＷおよびＭｏの１種または２種が（１／２Ｗ＋Ｍｏ）で１．５～６．０％（但し、Ｗ：３．０％以下）、ＶおよびＮｂの１種または２種が（Ｖ＋Ｎｂ）で０．５～３．０％、残部がＦｅおよび不可避的不純物からなる組成を有する。 The present invention is configured as follows to solve the above problems.
The molding powder of the present invention is, in mass %, C: 0.4 to 0.9%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 4.0 to 6.0%, One or two of W and Mo are (1/2W+Mo) and 1.5 to 6.0% (however, W: 3.0% or less), and one or two of V and Nb are (V+Nb). It has a composition of 0.5 to 3.0% with the balance being Fe and inevitable impurities.
　本発明の造形用粉末は、質量％で、Ｃｏを５％以下含有することが好ましい。 The powder for modeling of the present invention preferably contains Co in an amount of 5% by mass or less.
　本発明の造形用粉末は、粉末の断面において、最大長が０．１μｍ以上の炭化物が１個未満であることが好ましい。 The molding powder of the present invention preferably has less than one carbide having a maximum length of 0.1 μm or more in the cross section of the powder.
　本発明は、インゴットメイキングで必要であったソーキングを省略しても、粗大な炭化物を含まない造形用粉末を提供できる。これにより、本発明の造形用粉末は、例えば、粉末床溶融結合法や指向性エネルギー堆積法に適用しても、粗大化した炭化物が生成され難く、ソーキングが省略可能、すなわち、容易な工程にて、優れた特性の高速度工具鋼が得られる。このため、本発明は、高靭性、高耐ヒートクラック性を有するダイス、パンチ等の圧造工具や金型といった高速度工具鋼の製造に有用な技術となる。 The present invention can provide a modeling powder that does not contain coarse carbides even if the soaking that is necessary for ingot making is omitted. Thereby, the modeling powder of the present invention, for example, even when applied to the powder bed fusion bonding method or the directed energy deposition method, coarse particles are less likely to be generated, soaking can be omitted, that is, in an easy process. As a result, a high speed tool steel having excellent properties can be obtained. Therefore, the present invention is a useful technique for producing high speed tool steel such as dies and punches having high toughness and high heat crack resistance, and forging tools such as punches and dies.
本発明例１の造形用粉末の走査型電子顕微鏡写真。The scanning electron micrograph of the powder for modeling of this invention example 1. 本発明例２の造形用粉末の走査型電子顕微鏡写真。The scanning electron micrograph of the powder for modeling of this invention example 2. 本発明例２の造形用粉末を用いて作製した積層造形物の走査型電子顕微鏡写真。3 is a scanning electron micrograph of a layered model produced using the modeling powder of Example 2 of the present invention. 本発明例２の造形用粉末を用いて作製した積層造形物の光学顕微鏡写真。The optical microscope photograph of the layered modeling produced using the powder for modeling of this invention example 2.
　本発明の造形用粉末は、例えば、粉末床溶融結合法や指向性エネルギー堆積法といった粉末をニアネットシェイプにする付加加工に用いる粉末である。これにより、本発明は、従来のインゴットメイキングで必要とされていた分塊および仕上げという熱間での塑性加工を経る必要がないため、加工工数の短縮に寄与できる。
　そして、本発明の造形用粉末は、以下の成分組成で構成される。本発明の造形用粉末は、質量％で、Ｃ：０．４～０．９％、Ｓｉ：１．０％以下、Ｍｎ：１．０％以下、Ｃｒ：４．０～６．０％、ＷおよびＭｏの１種または２種が（１／２Ｗ＋Ｍｏ）で１．５～６．０％（但し、Ｗ：３．０％以下）、ＶおよびＮｂの１種または２種が（Ｖ＋Ｎｂ）で０．５～３．０％、残部がＦｅおよび不可避的不純物からなる。 The modeling powder of the present invention is a powder used for an additional process such as a powder bed fusion bonding method or a directed energy deposition method for converting the powder into a near net shape. As a result, the present invention does not need to undergo hot plastic working such as lumping and finishing, which were required in the conventional ingot making, and thus can contribute to shortening the working man-hour.
And the modeling powder of this invention is comprised by the following component compositions. The molding powder of the present invention is, in mass %, C: 0.4 to 0.9%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 4.0 to 6.0%, One or two of W and Mo are (1/2W+Mo) and 1.5 to 6.0% (however, W: 3.0% or less), and one or two of V and Nb are (V+Nb). 0.5 to 3.0%, the balance consisting of Fe and inevitable impurities.
　以下に、本発明が適用する成分範囲を限定した理由について説明する。尚、以下の説明では、「質量％」を単に「％」ともいう。
　Ｃは、Ｃｒ、Ｗ、Ｍｏ、Ｖ、Ｎｂ等の炭化物形成元素と結合して、硬い複炭化物を生成し、工具として必要な耐摩耗性の向上に効果がある。また、Ｃは、一部基地中に固溶して基地を強化する効果を有する。このとき、Ｃは、０．４％以上にすることで、工具として必要な硬さを確保することができる。また、上記と同様の理由から、Ｃは、０．５％以上が好ましい。
　一方、Ｃは、０．９％以下にすることで、炭化物量が過剰になることを抑制でき、靭性を向上させることができる。また、上記と同様の理由から、Ｃは、０．７％以下が好ましい。より好ましくは０．６％以下である。 The reason why the component range to which the present invention is applied is limited will be described below. In the following description, "mass%" is also simply referred to as "%".
C combines with carbide forming elements such as Cr, W, Mo, V and Nb to form a hard double carbide, and is effective in improving the wear resistance required as a tool. Further, C has an effect of strengthening the base by forming a solid solution in a part of the base. At this time, by setting C to 0.4% or more, the hardness required as a tool can be secured. For the same reason as above, C is preferably 0.5% or more.
On the other hand, when C is 0.9% or less, it is possible to prevent the amount of carbide from becoming excessive and improve the toughness. For the same reason as above, C is preferably 0.7% or less. It is more preferably 0.6% or less.
　Ｓｉは、１．０％以下にすることで、靭性の低下を抑制できる。また、上記と同様の理由から、Ｓｉは、０．５％以下にすることが好ましい。より好ましくは０．３％以下であり、さらに好ましくは０．２％以下である。そして、Ｓｉは、脱酸材として、０．１％以上含有させることが好ましい。 ㆍSi can be prevented from decreasing in toughness by making it 1.0% or less. Further, for the same reason as above, Si is preferably 0.5% or less. It is more preferably 0.3% or less, still more preferably 0.2% or less. Then, Si is preferably contained in an amount of 0.1% or more as a deoxidizing material.
　Ｍｎは、１．０％以下にすることで、被削性を向上させることができる。好ましくは０．８％以下であり、より好ましくは０．６％以下である。また、Ｍｎは、焼入れ性を向上させるため、０．３％以上含有させることが好ましい。より好ましくは０．４％以上である。 By setting Mn to 1.0% or less, machinability can be improved. It is preferably 0.8% or less, and more preferably 0.6% or less. Further, Mn is preferably contained in an amount of 0.3% or more in order to improve hardenability. It is more preferably 0.4% or more.
　Ｃｒは、Ｃと結合して炭化物を形成し、耐摩耗性を向上させるとともに、焼入性の向上にも寄与する。このため、本発明ではＣｒを４．０％以上とする。これにより、炭化物の形成量を適正化でき、耐摩耗性および焼入性を向上させることができる。また、上記と同様の理由から、Ｃｒは、４．１％以上にすることが好ましい。
　一方、Ｃｒは、６．０％以下にすることで、粗大な炭化物の形成を抑制でき、靭性を向上させることができる。また、上記と同様の理由から、Ｃｒは、５．０％以下にすることが好ましい。より好ましくは４．８％以下であり、さらに好ましくは４．５％以下である。 Cr combines with C to form a carbide, which improves wear resistance and contributes to improvement of hardenability. Therefore, in the present invention, Cr is set to 4.0% or more. This makes it possible to optimize the amount of carbide formed and improve wear resistance and hardenability. For the same reason as above, Cr is preferably 4.1% or more.
On the other hand, when Cr is 6.0% or less, the formation of coarse carbides can be suppressed and the toughness can be improved. For the same reason as above, Cr is preferably 5.0% or less. It is more preferably 4.8% or less, still more preferably 4.5% or less.
　ＷおよびＭｏは、Ｃと結合して炭化物を形成し、また、基地中に固溶して熱処理硬さを増して耐摩耗性を向上させることができる。ＷおよびＭｏの１種または２種を（１／２Ｗ＋Ｍｏ）で１．５％以上にすることで、Ｍｓ点を上げて、焼入れ後の残留オーステナイトを減少させることができ、硬さの向上に寄与する。また、上記と同様の理由から、上記の（１／２Ｗ＋Ｍｏ）は、２．０％以上にすることが好ましい。より好ましくは２．３％以上、さらに好ましくは２．５％以上である。
　また、ＷおよびＭｏの１種または２種を（１／２Ｗ＋Ｍｏ）で６．０％以下にすることで、被削性や靭性の低下を抑制できる。また、上記と同様の理由から、上記の（１／２Ｗ＋Ｍｏ）は、５．０％以下にすることが好ましい。より好ましくは４．０％以下、さらに好ましくは３．０％以下である。
　尚、Ｗは、機械的強度を確保する観点から、３．０％以下とする。好ましくは２．４％以下、より好ましくは１．８％以下である。また、好ましくは１．０％以上、より好ましくは１．５％以上である。 W and Mo can combine with C to form a carbide, and can form a solid solution in the matrix to increase the heat treatment hardness and improve wear resistance. By making one or two of W and Mo 1.5% or more in (1/2W+Mo), the Ms point can be raised and the retained austenite after quenching can be reduced, contributing to the improvement of hardness. To do. Further, for the same reason as above, the above (1/2W+Mo) is preferably 2.0% or more. It is more preferably 2.3% or more, still more preferably 2.5% or more.
Further, by reducing the content of one or two of W and Mo in (1/2W+Mo) to 6.0% or less, it is possible to suppress a decrease in machinability and toughness. Further, for the same reason as above, the above (1/2W+Mo) is preferably 5.0% or less. It is more preferably 4.0% or less, still more preferably 3.0% or less.
Note that W is 3.0% or less from the viewpoint of ensuring mechanical strength. It is preferably 2.4% or less, and more preferably 1.8% or less. Further, it is preferably 1.0% or more, more preferably 1.5% or more.
　ＶおよびＮｂは、炭化物を形成して耐摩耗性と耐焼付性を向上する。また、ＶおよびＮｂは、焼入れ時に基地に固溶して焼戻し時に微細で凝集し難い炭化物を析出し、高温域における軟化抵抗を大きくして、高い高温耐力を与える。また、ＶおよびＮｂは、結晶粒を微細化して靭性を向上させるとともにＡ１変態点を上げ、優れた高温耐力とあいまって耐ヒートクラック性を向上させる。
　また、Ｎｂは、軟化抵抗、高温強度を高め、焼入れ時の結晶粒の粗大化を抑制する。一方、Ｎｂが多すぎるとＭｓ点を下げて、焼入れ後の残留オーステナイトを増加させるため、硬さが低下する。また、Ｎｂは、少なすぎると型表面部の早期軟化を招く等上記効果が得られない。そこで、ＶおよびＮｂの１種または２種を（Ｖ＋Ｎｂ）で０．５～３．０％とする。好ましくは０．７％以上、より好ましくは０．９％以上、さらに好ましくは１．１％以上である。また、好ましくは２．４％以下、より好ましくは１．５％以下、さらに好ましくは１．３％以下である。 V and Nb form carbides to improve wear resistance and seizure resistance. Further, V and Nb form a solid solution in the matrix during quenching and precipitate fine carbides that are hard to agglomerate during tempering, thereby increasing the softening resistance in the high temperature region and giving high temperature proof stress. Further, V and Nb improve the toughness by refining the crystal grains, raise the A1 transformation point, and improve the heat crack resistance together with the excellent high temperature proof stress.
Further, Nb enhances softening resistance and high temperature strength, and suppresses coarsening of crystal grains during quenching. On the other hand, if the amount of Nb is too large, the Ms point is lowered and the retained austenite after quenching is increased, so that the hardness is lowered. On the other hand, if Nb is too small, the above effects cannot be obtained, such as causing early softening of the mold surface portion. Therefore, one or two of V and Nb is (V+Nb) 0.5 to 3.0%. It is preferably 0.7% or more, more preferably 0.9% or more, still more preferably 1.1% or more. Further, it is preferably 2.4% or less, more preferably 1.5% or less, still more preferably 1.3% or less.
　本発明の造形用粉末は、上記元素の他に、Ｃｏを含有させることができる。
　Ｃｏは、０．３％以上にすることが好ましく、これにより工具使用中の昇温時に極めて緻密で密着性の良い保護酸化被膜を形成して相手材との金属接触を減少し、表面の温度上昇が低減され、優れた耐摩耗性を付与できる。また、Ｃｏは、上記の保護酸化被膜の形成によって、断熱効果が得られ、また、保護作用により耐ヒートクラック性も向上でき、クラックの起点の生成抑制効果が得られる。
　一方、Ｃｏの含有量が多すぎると、靭性を低下させる虞があるため、Ｃｏは５．０％以下が好ましい。より好ましくは３．５％以下、さらに好ましくは２．０％以下、よりさらに好ましくは１．０％以下である。また、好ましくは０．３％以上、より好ましくは０．５％以上、さらに好ましくは０．７％以上である。 The powder for modeling of the present invention may contain Co in addition to the above elements.
Co is preferably 0.3% or more, which forms a protective oxide film that is extremely dense and has good adhesion at the time of temperature rise during tool use to reduce metal contact with the mating material and reduce surface temperature. The rise is reduced and excellent wear resistance can be imparted. Further, Co has a heat insulating effect due to the formation of the above-mentioned protective oxide film, and can also improve heat crack resistance due to the protective action, and has an effect of suppressing generation of crack starting points.
On the other hand, if the content of Co is too large, the toughness may be reduced, so Co is preferably 5.0% or less. It is more preferably 3.5% or less, still more preferably 2.0% or less, still more preferably 1.0% or less. Further, it is preferably 0.3% or more, more preferably 0.5% or more, still more preferably 0.7% or more.
　また、本発明の造形用粉末は、上記元素の他に、Ｎｉを含有させることもできる。
　Ｎｉは、上記のＣ、Ｃｒ、Ｍｎ、Ｍｏ、Ｗ等とともに、優れた焼入性を付与し、マルテンサイト主体の組織を形成し、基地の本質的な靭性を改善する観点から、０．０５％以上にすることが好ましい。
　また、Ｎｉは、１．００％以下にすることが好ましく、これにより、Ａ１変態点を適正化し、焼戻し硬さを低く抑え、機械加工性を向上できる。より好ましくは０．８０％以下、さらに好ましくは０．４０％以下、よりさらに好ましくは０．２０％以下である。
　そして、本発明の造形用粉末は、残部をＦｅおよび不可避的不純物とする。 Further, the modeling powder of the present invention may contain Ni in addition to the above elements.
Ni, together with the above C, Cr, Mn, Mo, W, etc., imparts excellent hardenability, forms a martensite-based structure, and improves the intrinsic toughness of the matrix. % Or more is preferable.
Further, Ni is preferably 1.00% or less, whereby the A1 transformation point is optimized, the tempering hardness is suppressed low, and the machinability can be improved. It is more preferably 0.80% or less, still more preferably 0.40% or less, still more preferably 0.20% or less.
And the remainder of the powder for modeling of the present invention is Fe and unavoidable impurities.
　造形用粉末に含まれる炭化物は、造形時の入熱条件によっては、溶融されずに造形物に残存する虞がある。また、造形用粉末に含まれる炭化物は、より微細であると、造形物の炭化物が微細になりやすく、靭性、耐ヒートクラック性を向上させることができる。このため、本発明の造形用粉末は、粉末の断面において、最大長が０．１μｍ以上の炭化物が１個未満であることが好ましい。 The carbide contained in the modeling powder may remain in the modeled product without being melted depending on the heat input condition during modeling. Further, if the carbide contained in the modeling powder is finer, the carbide of the molded article tends to be finer, and the toughness and heat crack resistance can be improved. Therefore, the modeling powder of the present invention preferably has less than one carbide having a maximum length of 0.1 μm or more in the cross section of the powder.
　本発明の造形用粉末を用いた造形物は、インゴット鋳造や連続鋳造等のインゴットメイキングと比較して、凝固プロセスにおける冷却速度が非常に速いため、形成される一次炭化物は微細になる。このため、上述した１２００～１３００℃で１０～２０時間という高温で長時間のソーキングを省略しても、焼きなまし、焼入れ等の熱処理によって一次炭化物を分解することが可能である。 The molded product using the molding powder of the present invention has a very high cooling rate in the solidification process, as compared with ingot casting such as ingot casting or continuous casting, so that the primary carbide formed becomes fine. Therefore, even if soaking at a high temperature of 1200 to 1300° C. for 10 to 20 hours described above for a long time is omitted, it is possible to decompose the primary carbides by a heat treatment such as annealing or quenching.
　本発明の造形用粉末は、例えば、ガスアトマイズ法や水アトマイズ法、ディスクアトマイズ法、プラズマアトマイズ法、回転電極法等によって製造することができる。
　これらの製造方法の中でも、ガスアトマイズ法は、スクラップ金属や金属粗原料等を溶解原料に使用することが可能であり、予め所望の組成および形状の原料を準備する必要があるプラズマアトマイズ法や回転電極法等と比較して、安価なコストで製造することが可能となる。このため、本発明の造形用粉末の製法として好ましい。 The powder for modeling of the present invention can be produced by, for example, a gas atomizing method, a water atomizing method, a disk atomizing method, a plasma atomizing method, a rotating electrode method, or the like.
Among these manufacturing methods, the gas atomization method is capable of using scrap metal or metal crude material as a melting raw material, and it is necessary to prepare a raw material having a desired composition and shape in advance. It becomes possible to manufacture at an inexpensive cost as compared with the method and the like. Therefore, it is preferable as a method for producing the molding powder of the present invention.
　ガスアトマイズ法は、所望の組成となるように準備した溶解原料を高周波誘導加熱により、その融点以上に加熱、溶融させた後、細孔を経由して流出させた溶融金属に対してアルゴンガスや窒素ガス等の不活性ガスを噴射することにより溶融金属を微細に粉砕し、急冷凝固させることによって粉末を得る方法である。
　本発明においては、粉末組織に晶出する炭化物をより微細に制御する観点から、窒素ガスを使用することも可能である。 The gas atomizing method is a method in which a molten raw material prepared to have a desired composition is heated to a temperature equal to or higher than its melting point by high frequency induction heating and melted, and then argon gas or nitrogen is applied to molten metal flown out through pores. This is a method in which a molten metal is finely pulverized by injecting an inert gas such as gas and rapidly solidified to obtain a powder.
In the present invention, nitrogen gas can be used from the viewpoint of finely controlling the carbide crystallized in the powder structure.
　本発明の造形用粉末は、体積基準の累積粒度分布の５０％粒径（以下、「Ｄ５０」という。）が１０～２５０μｍであることが好ましい。本発明の造形用粉末は、そのＤ５０を２５０μｍ以下とすることにより、急速な凝固速度、および凝固後の冷却速度を確保することが可能となり、粉末の組織内に最大長が０．１μｍ以上の炭化物が形成されることを抑制できる。
　また、本発明の造形用粉末は、そのＤ５０を１０μｍ以上とすることにより、雰囲気中の湿気等の影響を受けにくくなり、良好な流動性を確保することができる。
　尚、本発明の造形用粉末おける累積粒度分布は、累積体積粒度分布で表され、そのＤ５０は、ＪＩＳ　Ｚ　８８２５で規定される、レーザー回折散乱法による測定値で表される。 The modeling powder of the present invention preferably has a 50% particle size (hereinafter referred to as “D50”) of a volume-based cumulative particle size distribution of 10 to 250 μm. When the D50 of the modeling powder of the present invention is 250 μm or less, a rapid solidification rate and a cooling rate after solidification can be secured, and the maximum length within the powder structure is 0.1 μm or more. It is possible to suppress the formation of carbide.
Further, when the D50 of the modeling powder of the present invention is 10 μm or more, it is less likely to be affected by moisture in the atmosphere and good fluidity can be secured.
The cumulative particle size distribution of the molding powder of the present invention is represented by a cumulative volume particle size distribution, and its D50 is represented by a value measured by a laser diffraction/scattering method defined by JIS Z8825.
　本発明の造形用粉末は、その粉末が用いられる造形方法に合わせてメッシュを用いた篩別分級や気流分級等により粉末粒径を調整してもよい。
　レーザービームを用いた粉末床溶融結合法に使用される造形用粉末は、熱源となるレーザービームにより粉末を溶融させる一方で、熱影響の範囲を極力狭めるために溶融しづらい粗大な粉末を除去する必要がある。また、粉末の敷設性を確保するための最適な流動性を得るために、付着性の高い微細な粉末も除去する必要がある。このため、本発明の造形用粉末を粉末床溶融結合法に適用する場合は、Ｄ５０を１０～５３μｍの範囲に調整することが好ましい。 The particle size of the powder for modeling of the present invention may be adjusted by sieving classification using a mesh, airflow classification or the like according to the molding method in which the powder is used.
The modeling powder used in the powder bed fusion bonding method using a laser beam removes coarse powder that is difficult to melt in order to narrow the range of heat influence as much as possible while melting the powder by the laser beam that serves as a heat source. There is a need. Further, in order to obtain the optimum fluidity for ensuring the layability of the powder, it is necessary to remove the fine powder having high adhesiveness. Therefore, when the molding powder of the present invention is applied to the powder bed fusion bonding method, it is preferable to adjust D50 in the range of 10 to 53 μm.
　また、レーザービームを用いた指向性エネルギー堆積法に使用される金属粉末は、熱源となるレーザービームによって粉末を溶融させるために、溶融しづらい粗大な粉末を除去する必要がある。また、粉末を熱源へ供給する際の粉塵飛散を予防し、且つ粉末を容易に搬送可能とする流動性を確保する目的で微細な粉末も除去する必要がある。このため、本発明の造形用粉末を指向性エネルギー堆積法に適用する場合は、Ｄ５０を５３～１０６μｍの範囲に調整することが好ましい。
　さらに、熱源に電子ビームやプラズマを用いる場合は、より粗大な金属粒子を用いて造形することが可能となるため、Ｄ５０は７５～２５０μｍにすることが好ましい。 Further, the metal powder used in the directed energy deposition method using a laser beam needs to remove coarse powder that is difficult to melt because the powder is melted by the laser beam serving as a heat source. In addition, it is necessary to remove fine powder for the purpose of preventing dust scattering when supplying the powder to the heat source and ensuring fluidity that allows the powder to be easily transported. Therefore, when the modeling powder of the present invention is applied to the directed energy deposition method, it is preferable to adjust D50 in the range of 53 to 106 μm.
Further, when an electron beam or plasma is used as the heat source, it is possible to form using coarser metal particles, so D50 is preferably 75 to 250 μm.
　表１の組成となるように、各金属粗原料を準備した後、高周波誘導溶解炉に装入して溶融させ、溶融金属をガス圧３．０ＭＰａのアルゴンガスによって粉砕することでアトマイズ粉末を得た。
　得られたアトマイズ粉末に対して、目開き５３μｍの金属メッシュ篩を用いた篩別分級により、５３μｍよりも微細な粉末を除去してから、目開き１０６μｍの金属メッシュ篩を用いた篩別分級により、１０６μｍよりも粗大な粉末を除去し、粒径が５３μｍ～１０６μｍとなる本発明例１および本発明例２の造形用粉末を得た。 After preparing each metal crude material so as to have the composition shown in Table 1, it is charged into a high-frequency induction melting furnace and melted, and atomized powder is obtained by crushing the molten metal with argon gas having a gas pressure of 3.0 MPa. It was
The atomized powder thus obtained is classified by sieving using a metal mesh sieve having an opening of 53 μm to remove finer particles than 53 μm, and then sieving using a metal mesh sieve having an opening of 106 μm. , 106 μm, and powders for molding of Invention Example 1 and Invention Example 2 having a particle size of 53 μm to 106 μm were obtained.
　上記の造形用粉末のＤ５０を、Ｍａｌｖｅｒｎ　Ｉｎｓｔｒｕｍｅｎｔｓ製のレーザー回折散乱式粒子径分布測定装置　ＭａｓｔｅｒＳｉｚｅｒ２０００で測定した。測定したＤ５０の値は、本発明例１が８４μｍ、本発明例２が８２μｍであった。これにより、本発明例となる造形用粉末は、レーザービームを用いた指向性エネルギー堆積法に好適な粉末であることが確認できた。 The D50 of the above-mentioned molding powder was measured with a laser diffraction/scattering particle size distribution measuring device MasterSizer2000 manufactured by Malvern Instruments. The measured D50 values were 84 μm in the present invention example 1 and 82 μm in the present invention example 2. From this, it was confirmed that the modeling powder as the example of the present invention was a powder suitable for the directed energy deposition method using a laser beam.
　また、得られた造形用粉末について、Ｃを赤外線吸収法、Ｃ以外の表１に記載した元素をＩＣＰ発光分光法によって分析した。
　表１より、本発明例となる粉末は、いずれも、Ｃ、Ｓｉ、Ｍｎ、Ｃｒ、Ｗ、Ｍｏ、Ｖ、Ｎｂ、Ｎｉ、Ｃｏの各々の元素の分析値が本発明の規定範囲に収まっており、本発明例の粉末で造形した後に、高速度工具鋼として十分な特性を発現可能であることが確認できた。 Further, with respect to the obtained modeling powder, C was analyzed by an infrared absorption method, and elements other than C described in Table 1 were analyzed by ICP emission spectroscopy.
From Table 1, in all the powders of the present invention, the analytical values of each element of C, Si, Mn, Cr, W, Mo, V, Nb, Ni and Co are within the specified range of the present invention. However, it was confirmed that after shaping with the powder of the present invention example, sufficient characteristics as high speed tool steel could be exhibited.
　本発明例の造形用粉末のミクロ組織を観察するために、各々の粉末の集合を、一般的な顕微鏡観察用試料の作製要領にしたがい、その複数の粉末が概ね一面に並ぶようにして熱硬化性樹脂に埋め込んだ後、バフ研磨して試料調整した。これらの試料をナイタールによって腐食し、断面組織をＺＥＩＳＳ製の走査型電子顕微鏡　ＵＬＲＴＡ５５を用いて、その二次電子像を観察した。その結果を図１および図２に示す。 In order to observe the microstructure of the modeling powder of the present invention example, the set of each powder was heat-cured according to the general procedure for preparing a sample for microscopic observation so that the plurality of powders were arranged in a line on one surface. The sample was prepared by buffing after embedding it in a hydrophilic resin. These samples were corroded by Nital, and the secondary electron image of the cross-sectional structure was observed using a scanning electron microscope ULRTA55 manufactured by ZEISS. The results are shown in FIGS. 1 and 2.
　本発明例の造形用粉末は、いずれも、断面組織内に、最大長が０．１μｍ以上の粗大な炭化物を含んでいないことが確認できた。これは、本発明の造形用粉末を造形に使用した際に、製造工程の中でソーキング処理を施す必要がなく、且つ１μｍ以上の点状炭化物が少ない高速度工具鋼を製造することが可能な造形用粉末となっていることが確認できた。 It was confirmed that none of the modeling powders of the present invention contained coarse carbide having a maximum length of 0.1 μm or more in the cross-sectional structure. This is because when the molding powder of the present invention is used for molding, it is not necessary to perform a soaking process in the manufacturing process, and it is possible to manufacture a high-speed tool steel containing few point carbides of 1 μm or more. It was confirmed that the powder was a molding powder.
　本発明例２の粉末を用いて、指向性エネルギー堆積法により積層造形を実施した。具体的には、ＤＭＧ森精機製のＬＡＳＥＲＴＥＣ　６５　３Ｄを用いて、ＪＩＳでいうＳＫＤ６１製のプレート上に、本発明例２の造形用粉末を供給しながらレーザー熱源を照射することによって、線形のビードを積層させることにより、積層造形物を作製した。
　そして、この積層造形物に対して、１１４０℃で焼入れ、５６０℃で焼戻しを行なった。 Using the powder of Example 2 of the present invention, additive manufacturing was carried out by the directed energy deposition method. Specifically, by using LASERTEC 65 3D manufactured by DMG MORI SEIKI on a plate made of SKD61 according to JIS while irradiating a laser heat source while supplying the modeling powder of Inventive Example 2, a linear bead By laminating, a layered product was produced.
Then, this layered product was quenched at 1140°C and tempered at 560°C.
　上記で得た焼戻しした積層造形物の厚さ方向における断面の組織を観察した。具体的には、積層造形物の厚さ方向の断面を露出させるように熱硬化性樹脂に埋め込んだ後、バフ研磨して試料調整し、ナイタールによって腐食して、観察用試料を作製した。そして、この観察用試料について、キーエンス製の走査型顕微鏡　ＶＥ－８８００および光学顕微鏡を用いてそれぞれ観察した。その結果を図３および図４に示す。
　本発明の造形用粉末を用いて得た積層造形物は、図３に示す走査型電子顕微鏡の二次電子像の観察結果から、図３中の矢印で示される点状炭化物が確認される。そして、その点状炭化物は、倍率５０００倍、４７５０μｍ２の範囲において観察される最大粒径が０．８μｍであった。また、本発明の造形用粉末を用いて得た積層造形物は、図４に示す光学顕微鏡による観察結果から、倍率５００倍、直径が１５ｍｍ円の面積内において、粒径が１μｍ以上の点状炭化物は、認められなかった。
　以上のことから、本発明の造形用粉末は、インゴットメイキングで必要であったソーキングを省略しても、１μｍ以上の点状炭化物が少ない高速度工具鋼を製造することができる、レーザービームを用いた指向性エネルギー堆積法に好適な造形用粉末であることが確認できた。

  The structure of the cross section in the thickness direction of the tempered layered product obtained above was observed. Specifically, after embedding in a thermosetting resin so as to expose the cross section in the thickness direction of the layered product, the sample was prepared by buffing and corroded by Nital to prepare an observation sample. Then, this observation sample was observed using a scanning microscope VE-8800 manufactured by Keyence Corporation and an optical microscope. The results are shown in FIGS. 3 and 4.
In the layered product obtained by using the powder for modeling of the present invention, point-like carbides indicated by arrows in FIG. 3 are confirmed from the observation result of the secondary electron image of the scanning electron microscope shown in FIG. Then, the point carbides had a maximum particle size of 0.8 μm observed in a range of 4750 μm 2 at a magnification of 5000 times. From the observation result by the optical microscope shown in FIG. 4, the layered product obtained by using the modeling powder of the present invention has a dot shape with a particle size of 1 μm or more in the area of a magnification of 500 times and a diameter of 15 mm. No carbide was observed.
From the above, the shaping powder of the present invention can produce a high-speed tool steel with a small amount of point carbides of 1 μm or more by using a laser beam, even if the soaking that is required for ingot making is omitted. It was confirmed that the powder was suitable for the directed energy deposition method.

Figure JPOXMLDOC01-appb-T000001
 
Figure JPOXMLDOC01-appb-T000001
 

Claims (3)

  1. 　質量％で、Ｃ：０．４～０．９％、Ｓｉ：１．０％以下、Ｍｎ：１．０％以下、Ｃｒ：４．０～６．０％、ＷおよびＭｏの１種または２種が（１／２Ｗ＋Ｍｏ）で１．５～６．０％（但し、Ｗ：３．０％以下）、ＶおよびＮｂの１種または２種が（Ｖ＋Ｎｂ）で０．５～３．０％、残部がＦｅおよび不可避的不純物からなる造形用粉末。 % By mass, C: 0.4 to 0.9%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 4.0 to 6.0%, one or two of W and Mo. 1.5-6.0% in the case of (1/2 W+Mo) (however, W: 3.0% or less), 0.5-3.0% in the case of one or two kinds of V and Nb in the case of (V+Nb) , The balance being Fe and unavoidable impurities.
  2. 　質量％で、Ｃｏを５％以下含有する請求項１に記載の造形用粉末。 The modeling powder according to claim 1, containing 5% or less of Co in mass %.
  3. 　粉末の断面において、最大長が０．１μｍ以上の炭化物が１個未満である請求項１または請求項２に記載の造形用粉末。

          The powder for modeling according to claim 1 or 2, wherein, in the cross section of the powder, there is less than one carbide having a maximum length of 0.1 µm or more.

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