JP6754844B2 - Die-casting mold manufacturing method and die-casting mold - Google Patents

Die-casting mold manufacturing method and die-casting mold Download PDF

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JP6754844B2
JP6754844B2 JP2018552609A JP2018552609A JP6754844B2 JP 6754844 B2 JP6754844 B2 JP 6754844B2 JP 2018552609 A JP2018552609 A JP 2018552609A JP 2018552609 A JP2018552609 A JP 2018552609A JP 6754844 B2 JP6754844 B2 JP 6754844B2
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water cooling
hardness
cooling hole
mold
die
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JPWO2018097165A1 (en
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秀治 稲垣
秀治 稲垣
雅稔 鳴海
雅稔 鳴海
春幸 森
春幸 森
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KOYAMA STEEL, LTD.
Hitachi Metals Ltd
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Hitachi Metals Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/06—Permanent moulds for shaped castings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/22—Dies; Die plates; Die supports; Cooling equipment for dies; Accessories for loosening and ejecting castings from dies

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Heat Treatment Of Articles (AREA)

Description

本発明は、ダイカスト金型の製造方法およびダイカスト金型に関するものである。 The present invention relates to a method for manufacturing a die casting die and a die casting die.

特許文献１に金型の熱処理方法が知られている。金型には、成形面の温度を低減させるために金型の内部に水冷孔が設けられている。使用中の金型において、この水冷孔には熱応力が生じる。また、水冷孔をなす面には鋼材が錆び、水素が侵入しやすく、水素脆化を起こしやすい。これらのことによって、水冷孔周囲には割れが生じる懸念がある。そこで、特許文献１は、金型に設ける水冷孔に局部的に焼鈍処理を行うことを提案している。これにより、金型自体の硬さを保ちつつ、水冷孔の周囲のみ硬さを下げて水冷孔周囲に割れが生じにくくしている。 A method for heat-treating a mold is known in Patent Document 1. The mold is provided with water cooling holes inside the mold in order to reduce the temperature of the molding surface. Thermal stress is generated in the water cooling holes in the mold in use. In addition, the steel material rusts on the surface forming the water cooling hole, hydrogen easily penetrates, and hydrogen embrittlement easily occurs. Due to these factors, there is a concern that cracks may occur around the water cooling holes. Therefore, Patent Document 1 proposes that the water cooling holes provided in the mold are locally annealed. As a result, while maintaining the hardness of the mold itself, the hardness is lowered only around the water cooling hole to prevent cracks from occurring around the water cooling hole.

日本国特開平8-31557号公報Japanese Patent Application Laid-Open No. 8-31557

特許文献１に記載の方法では、高周波熱処理装置を用いて水冷孔の孔面における表層部の軟化熱処理をしている。ところが、特許文献１の方法においては、高周波熱処理装置の加熱部は水冷孔の側面は加熱しやすいが、底面は加熱しにくい。しかしながら、水冷孔は成形面に向かって形成され、成形面の冷却を目的としている。このため、特に水冷孔の底面にこそ軟化熱処理を行いたい。この点で、特許文献１の方法に改善の余地があった。 In the method described in Patent Document 1, a high-frequency heat treatment apparatus is used to soften and heat-treat the surface layer portion on the pore surface of the water-cooled hole. However, in the method of Patent Document 1, in the heating portion of the high-frequency heat treatment apparatus, the side surface of the water cooling hole is easily heated, but the bottom surface is not easily heated. However, the water cooling holes are formed toward the molding surface and are intended for cooling the molding surface. For this reason, it is particularly desirable to perform softening heat treatment on the bottom surface of the water cooling holes. In this respect, there is room for improvement in the method of Patent Document 1.

また、一般的に、水冷孔はドリルで側面を形成したときに、その底面にドリル先端部の形状跡である隅（コーナー）が残る。つまり、ドリルで穿孔加工したときの水冷孔の底面には、そのドリルの先端に対応した中央の位置（つまり、水冷孔の最深の位置）と、ドリルの外周コーナーに対応した中央周りの位置とに、ドリル先端部の形状に起因する隅が形成される。そして、この隅を起点に割れが生じやすい。そこで、この隅をなくして、割れを生じ難くするために、底面が半球状となるようにアール加工している。そして、このアール加工をした後の水冷孔の底面の形状は、一般的に、水冷孔の内径をＤとしたときに、底面の中央からおおよそＤ／２の高さの位置を球の中心とした半球状となる。そして、水冷孔の底面から割れがさらに生じにくくするために、上記の半球状の面でなる水冷孔の底面に軟化熱処理を行いたい。
そこで本発明は、水冷孔の底面を含む領域に確実に軟化熱処理を施すことができるダイカスト金型の製造方法およびダイカスト金型を提供する。Further, in general, when the side surface of the water cooling hole is formed by a drill, a corner, which is a trace of the shape of the tip of the drill, remains on the bottom surface thereof. In other words, the bottom surface of the water-cooled hole when drilled with a drill has a central position corresponding to the tip of the drill (that is, the deepest position of the water-cooled hole) and a position around the center corresponding to the outer peripheral corner of the drill. A corner is formed due to the shape of the tip of the drill. Then, cracks are likely to occur starting from this corner. Therefore, in order to eliminate this corner and prevent cracking, the bottom surface is rounded so as to be hemispherical. The shape of the bottom surface of the water cooling hole after this rounding is generally such that the position at a height of approximately D / 2 from the center of the bottom surface is the center of the sphere, where D is the inner diameter of the water cooling hole. It becomes a hemispherical shape. Then, in order to make it more difficult for cracks to occur from the bottom surface of the water cooling hole, it is desired to perform a softening heat treatment on the bottom surface of the water cooling hole formed of the hemispherical surface.
Therefore, the present invention provides a method for manufacturing a die-casting die and a die-casting die capable of reliably performing a softening heat treatment on a region including the bottom surface of the water cooling hole.

本開示の一形態によれば、
内径Ｄの有底の水冷孔が設けられたダイカスト金型の製造方法であって、
前記水冷孔をなす孔面は、前記水冷孔の底をなす底面と、前記底面から入口に向かって延びる側面を有し、
前記水冷孔に挿入した外径ｄの管の先端から前記底面に向けて過熱蒸気を送り込み、前記底面を加熱して軟化させる熱処理工程を有する、ダイカスト金型の製造方法が提供される。According to one form of the disclosure
This is a method for manufacturing a die casting die provided with a bottomed water cooling hole having an inner diameter D.
The hole surface forming the water cooling hole has a bottom surface forming the bottom of the water cooling hole and a side surface extending from the bottom surface toward the inlet.
Provided is a method for manufacturing a die casting mold, which comprises a heat treatment step of sending superheated steam from the tip of a tube having an outer diameter d inserted into the water cooling hole toward the bottom surface to heat and soften the bottom surface.

本開示の一形態によれば、
前記管の先端と前記底面の最深の位置との離間距離をｈと定義したとき、
０．５×（Ｄ−ｄ）／２ ≦ ｈ ≦ １．５×（Ｄ−ｄ）／２
となる位置に前記管の先端を保持して前記熱処理工程を行ってもよい。According to one form of the disclosure
When the distance between the tip of the pipe and the deepest position of the bottom surface is defined as h,
0.5 × (Dd) / 2 ≦ h ≦ 1.5 × (Dd) / 2
The heat treatment step may be performed by holding the tip of the tube at a position where

本開示の一形態によれば、
前記管の先端が円錐台形状であってもよい。According to one form of the disclosure
The tip of the tube may have a truncated cone shape.

本開示の一形態によれば、
前記底面が略半球状となるように加工して前記水冷孔を形成してもよい。According to one form of the disclosure
The water cooling hole may be formed by processing so that the bottom surface is substantially hemispherical.

本開示の一形態によれば、
内径Ｄの有底の水冷孔が設けられたダイカスト金型であって、
前記水冷孔をなす孔面は、前記水冷孔の底をなす底面と、前記底面から入口に向かって延びる側面を有し、
前記底面の最深の位置の硬さＨ１が、前記水冷孔の入口の入口硬さＨ２よりも低い、ダイカスト金型が提供される。According to one form of the disclosure
A die-casting die provided with a bottomed water cooling hole with an inner diameter D.
The hole surface forming the water cooling hole has a bottom surface forming the bottom of the water cooling hole and a side surface extending from the bottom surface toward the inlet.
A die casting die is provided in which the hardness H1 at the deepest position of the bottom surface is lower than the inlet hardness H2 at the entrance of the water cooling hole.

本開示の一形態によれば、
前記孔面のうち、前記底面の最深の位置から高さＤの位置までの領域の硬さＨ３が、前記入口硬さＨ２より低くてもよい。According to one form of the disclosure
The hardness H3 of the region of the hole surface from the deepest position of the bottom surface to the position of height D may be lower than the entrance hardness H2.

本開示の一形態によれば、
前記底面の最深の位置から前記金型内部に向かって、前記水冷孔の径方向と直角の方向に１ｍｍ入った位置の金型内部の硬さＨ１２が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％より低くてもよい。According to one form of the disclosure
The hardness H12 inside the mold at a position 1 mm from the deepest position on the bottom surface toward the inside of the mold in the direction perpendicular to the radial direction of the water cooling hole is compared with the Rockwell hardness HRC on the C scale. When this is done, it may be lower than 95% of the entrance hardness H2.

本開示の一形態によれば、
前記底面の最深の位置から前記金型内部に向かって、前記水冷孔の径方向と直角の方向に５ｍｍ入った位置の金型内部の硬さＨ１５が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％より高くてもよい。According to one form of the disclosure
The hardness H15 inside the mold at a position 5 mm in the direction perpendicular to the radial direction of the water cooling hole from the deepest position of the bottom surface toward the inside of the mold is compared with the Rockwell hardness HRC of the C scale. When it is, it may be higher than 95% of the entrance hardness H2.

本開示の一形態によれば、
前記底面の最深の位置から高さＤ／２の位置の前記側面から金型内部に向かって前記水冷孔の径方向に３ｍｍ入った位置の金型内部の硬さＨ３３が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口の硬さＨ２の９５％より低くてもよい。According to one form of the disclosure
The hardness H33 inside the mold at a position 3 mm in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface toward the inside of the mold is a C-scale Rockwell. When compared in terms of hardness HRC, it may be lower than 95% of the hardness H2 at the inlet.

本開示の一形態によれば、
前記底面の最深の位置から高さＤ／２の位置の前記側面から金型内部に向かって前記水冷孔の径方向に７ｍｍ入った位置の金型内部の硬さＨ３７が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口の硬さＨ２の９５％より高くてもよい。According to one form of the disclosure
The hardness H37 inside the mold at a position 7 mm in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface toward the inside of the mold is a C-scale Rockwell. When compared in terms of hardness HRC, it may be higher than 95% of the hardness H2 at the inlet.

本開示の一形態によれば、
前記金型内部の領域において、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％以下となっている領域を軟化領域と呼び、
前記底面の最深の位置から前記水冷孔の径方向と直角する方向における前記軟化領域の厚みをＤ１と呼び、
前記底面の最深の位置から高さＤ／２の位置の前記側面から前記水冷孔の径方向における前記軟化領域の厚みをＤ２と呼ぶとき、
前記厚みＤ１が前記厚みＤ２より小さくてもよい。According to one form of the disclosure
In the region inside the mold, the region where the Rockwell hardness HRC of the C scale is 95% or less of the entrance hardness H2 is called a softening region.
The thickness of the softened region in the direction perpendicular to the radial direction of the water cooling hole from the deepest position of the bottom surface is called D1.
When the thickness of the softened region in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface is referred to as D2.
The thickness D1 may be smaller than the thickness D2.

本開示の一形態によれば、
前記底面が略半球状であってもよい。According to one form of the disclosure
The bottom surface may be substantially hemispherical.

本発明によれば、水冷孔の底面を含む領域に確実に軟化熱処理を施すことができるダイカスト金型の製造方法およびダイカスト金型が提供される。 According to the present invention, there is provided a method for manufacturing a die-casting die and a die-casting die capable of reliably performing a softening heat treatment on a region including the bottom surface of a water cooling hole.

（ａ）は本実施形態のダイカスト金型の上面図（水冷孔の入口側から見た図）であり、（ｂ）はその側面図である。(A) is a top view (a view seen from the entrance side of the water cooling hole) of the die casting die of the present embodiment, and (b) is a side view thereof. 本発明の実施形態に係るダイカスト金型の熱処理工程を行う際の模式図である。It is a schematic diagram at the time of performing the heat treatment process of the die casting die which concerns on embodiment of this invention. 水冷孔の内部に管を挿入した様子を示す断面図である。It is sectional drawing which shows the state that the pipe was inserted in the water cooling hole. φ１５の水冷孔が設けられたテストピースの各部の寸法と、温度測定点を示す図である。It is a figure which shows the dimension of each part of the test piece provided with the water cooling hole of φ15, and the temperature measurement point. 過熱水蒸気を供給した際の温度履歴を示す図である。It is a figure which shows the temperature history when superheated steam is supplied. （ａ）は水冷孔の中心軸線に沿ったテストピースの断面図であり、（ｂ）は水冷孔の中心軸線に直交する面のテストピースの断面図である。(A) is a cross-sectional view of a test piece along the central axis of the water cooling hole, and (b) is a cross-sectional view of the test piece having a surface orthogonal to the central axis of the water cooling hole. 水冷孔の底面の最深の位置から上方へ７．５ｍｍに位置する断面Ｂにおける硬さを示すレーダーチャートである。It is a radar chart which shows the hardness in the cross section B which is located 7.5mm upward from the deepest position of the bottom surface of a water cooling hole. 水冷孔の底面の最深の位置から上方へ１５ｍｍに位置する断面Ｃにおける硬さを示すレーダーチャートである。It is a radar chart which shows the hardness in the cross section C located 15mm upward from the deepest position of the bottom surface of a water cooling hole. テストピースの上面Ｅにおける硬さを示すレーダーチャートである。6 is a radar chart showing the hardness of the upper surface E of the test piece. 図１１に示す硬さを測定した測定点を示す図である。It is a figure which shows the measurement point which measured the hardness shown in FIG. 水冷孔の孔面からの離間距離と硬度との関係を示すグラフである。It is a graph which shows the relationship between the separation distance from a hole surface of a water cooling hole, and hardness. 金型内部の領域における軟化領域を示した模式図である。It is a schematic diagram which showed the softening region in the region inside a mold. ダイカスト金型の各部の硬さを示す図である。It is a figure which shows the hardness of each part of a die-casting die. φ２０の水冷孔が設けられたテストピースの各部の寸法と、温度測定点を示す図である。It is a figure which shows the dimension of each part of the test piece provided with the water cooling hole of φ20, and the temperature measurement point. 過熱水蒸気を供給した際の温度履歴を示す図である。It is a figure which shows the temperature history when superheated steam is supplied. 水冷孔の底面の最深の位置から上方へ１０ｍｍに位置する断面における硬さを示すレーダーチャートである。It is a radar chart which shows the hardness in the cross section located 10mm upward from the deepest position of the bottom surface of a water cooling hole. 水冷孔の底面の最深の位置から上方へ２０ｍｍに位置する断面における硬さを示すレーダーチャートである。It is a radar chart which shows the hardness in the cross section located 20mm upward from the deepest position of the bottom surface of a water cooling hole. テストピースの上面における硬さを示すレーダーチャートである。It is a radar chart which shows the hardness on the upper surface of a test piece. 水冷孔の孔面からの離間距離と硬さの関係を示すグラフである。It is a graph which shows the relationship between the separation distance from a hole surface of a water cooling hole, and hardness.

以下、本発明の実施形態について図面を参照しながら説明する。尚、本実施形態の説明において既に説明された部材と同一の参照番号を有する部材については、説明の便宜上、その説明は省略する。また、本図面に示された各部材の寸法は、説明の便宜上、実際の各部材の寸法とは異なる場合がある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience of explanation, the description of the member having the same reference number as the member already described in the description of the present embodiment will be omitted. Further, the dimensions of each member shown in this drawing may differ from the actual dimensions of each member for convenience of explanation.

図１は、本実施形態のダイカスト金型１の略直方体状のテストピースを示している。図１の（ａ）は、ダイカスト金型１を、その水冷孔の入口側（上面１ｂ）から見た図、（ｂ）は、その側面図である。実際のダイカスト金型１は複雑な形状をしているが、以降の説明では、この直方体状のテストピースをダイカスト金型１と呼ぶことにする。
ダイカスト金型１は鋼材で形成されている。ダイカスト金型１の下面が成形面１ａをなす。ダイカスト金型１の使用時には、この成形面１ａがキャビティを構成する。成形面１ａの形状がダイカストで製造される製品の表面に転写される。ダイカスト金型１の使用時には、成形面１ａは高温の溶湯に曝され、成形面１ａを含むダイカスト金型１全体が高温になる。そこで、この成形面１ａが高温になることを防止するために、ダイカスト金型１には水冷孔２が設けられている。FIG. 1 shows a substantially rectangular parallelepiped test piece of the die casting die 1 of the present embodiment. FIG. 1A is a view of the die casting die 1 as viewed from the inlet side (upper surface 1b) of the water cooling hole, and FIG. 1B is a side view thereof. The actual die-casting die 1 has a complicated shape, but in the following description, this rectangular parallelepiped test piece will be referred to as the die-casting die 1.
The die casting die 1 is made of steel. The lower surface of the die casting mold 1 forms the molding surface 1a. When the die casting mold 1 is used, the molding surface 1a constitutes a cavity. The shape of the molding surface 1a is transferred to the surface of the product manufactured by die casting. When the die casting mold 1 is used, the molding surface 1a is exposed to a high temperature molten metal, and the entire die casting mold 1 including the molding surface 1a becomes hot. Therefore, in order to prevent the molding surface 1a from becoming hot, the die casting mold 1 is provided with a water cooling hole 2.

水冷孔２は、ダイカスト金型１の上面１ｂに開口している。水冷孔２は、上面１ｂから下方（つまり、成形面１ａ）に向かって延びる有底の穴である。水冷孔２を構成するダイカスト金型１の面を孔面３と呼ぶ。この孔面３として、水冷孔２の底をなす部位を底面４と呼び、底面４から入口に向かって延びる部位を側面５と呼ぶ。水冷孔２は底面４を含む半球状の領域（半球状領域）と、それより上方に位置する略円柱状の領域（円柱状領域）で構成されている。以降の説明において、水冷孔２の直径（内径）をＤと呼ぶ。ダイカスト金型１の使用時には、水冷孔２の入口６から内部に冷却管が差し込まれ、水冷孔２の内部に水等の冷却媒体を流し込むことによりダイカスト金型１を冷却する。 The water cooling hole 2 is opened in the upper surface 1b of the die casting mold 1. The water cooling hole 2 is a bottomed hole extending downward from the upper surface 1b (that is, the molding surface 1a). The surface of the die casting mold 1 constituting the water cooling hole 2 is called a hole surface 3. As the hole surface 3, the portion forming the bottom of the water cooling hole 2 is referred to as a bottom surface 4, and the portion extending from the bottom surface 4 toward the inlet is referred to as a side surface 5. The water cooling hole 2 is composed of a hemispherical region (hemispherical region) including the bottom surface 4 and a substantially cylindrical region (cylindrical region) located above the hemispherical region. In the following description, the diameter (inner diameter) of the water cooling hole 2 is referred to as D. When the die casting mold 1 is used, a cooling pipe is inserted into the inside from the inlet 6 of the water cooling hole 2, and a cooling medium such as water is poured into the water cooling hole 2 to cool the die casting mold 1.

ところで、ダイカスト金型１の使用時には、水冷孔２に応力が生じる。そして、このように水冷孔２は水に曝されるので、鋼材が錆びたり水素脆化を起こしたりしやすい。これらのことによって、水冷孔２の孔面３には割れが生じることが懸念される。そこで水冷孔２に焼鈍処理を施して、硬さを下げ、割れが生じにくくすることが行われている。また、焼入れ処理後に施される焼戻し処理を利用して、水冷孔２の周囲の硬さを下げることも可能である。ダイカスト金型１の使用時には、水冷孔２の底面４側の領域は入口６側に比べて高温に曝される。このため、水冷孔２の底面４側の硬さは下げたいが、入口６側はそれほど硬さを下げなくてもよい。そこで、この硬さ分布を達成するための、上記の焼鈍工程や焼戻し工程に適用することが可能な熱処理工程について次に説明する。 By the way, when the die casting die 1 is used, stress is generated in the water cooling hole 2. Since the water cooling hole 2 is exposed to water in this way, the steel material is liable to rust or hydrogen embrittlement. Due to these factors, there is a concern that the hole surface 3 of the water cooling hole 2 may be cracked. Therefore, the water cooling holes 2 are annealed to reduce the hardness and prevent cracks from occurring. It is also possible to reduce the hardness around the water cooling hole 2 by utilizing the tempering treatment performed after the quenching treatment. When the die casting mold 1 is used, the region on the bottom surface 4 side of the water cooling hole 2 is exposed to a higher temperature than the inlet 6 side. Therefore, although it is desired to reduce the hardness of the bottom surface 4 side of the water cooling hole 2, it is not necessary to reduce the hardness of the inlet 6 side so much. Therefore, a heat treatment step that can be applied to the above-mentioned annealing step and tempering step to achieve this hardness distribution will be described below.

図２は、本発明の実施形態に係るダイカスト金型１の熱処理工程を行う際の模式図である。図２に示すように、ダイカスト金型１の水冷孔２に管１０を挿入する。この管１０の末端は、過熱蒸気発生装置１１に接続されている。この管１０の先端から水冷孔２の底面４に向けて過熱蒸気を送り込む。すると、過熱蒸気により少なくとも底面４が温められ、底面４を含むダイカスト金型１の孔面３が軟化される。最深の位置Ａの硬さＨ１が、水冷孔２の入口６の硬さＨ２よりも低くされている。 FIG. 2 is a schematic view when performing a heat treatment step of the die casting die 1 according to the embodiment of the present invention. As shown in FIG. 2, the pipe 10 is inserted into the water cooling hole 2 of the die casting mold 1. The end of the pipe 10 is connected to the superheated steam generator 11. Superheated steam is sent from the tip of the pipe 10 toward the bottom surface 4 of the water cooling hole 2. Then, at least the bottom surface 4 is warmed by the superheated steam, and the hole surface 3 of the die casting mold 1 including the bottom surface 4 is softened. The hardness H1 at the deepest position A is lower than the hardness H2 at the inlet 6 of the water cooling hole 2.

過熱蒸気は、例えば、およそ１２００℃にも達する程の高温の水蒸気である。過熱蒸気は、空気に比べて単位体積当たりの熱容量が大きく、また、熱伝導性に優れている。このため、管１０から噴き出された過熱蒸気が底面４に接触すると、過熱蒸気の持つ熱量はすぐに底面４に伝わり底面４を素早く軟化温度にまで加熱することができる。このように、管１０の先端から底面４に向けて過熱蒸気を送り込むことにより、底面４の温度を上げやすく、底面４の熱処理を確実に行うことができる。 The superheated steam is, for example, steam having a high temperature as high as about 1200 ° C. Superheated steam has a larger heat capacity per unit volume than air, and has excellent thermal conductivity. Therefore, when the superheated steam ejected from the pipe 10 comes into contact with the bottom surface 4, the amount of heat of the superheated steam is immediately transmitted to the bottom surface 4, and the bottom surface 4 can be quickly heated to the softening temperature. By sending superheated steam from the tip of the tube 10 toward the bottom surface 4 in this way, it is easy to raise the temperature of the bottom surface 4, and the heat treatment of the bottom surface 4 can be reliably performed.

ところで、上述した特許文献１に記載の高周波熱処理装置は、加熱源が周囲の空気を加熱し、加熱された空気を介して金型が加熱される。特許文献１の空気に比べて、本実施形態の過熱蒸気は非常に高い熱伝導性を有する。
本実施形態によれば、このように高い熱伝導性を有する過熱蒸気が移動しながら孔面３に接し、孔面３の極表層を狙って目標温度まで速やかに加熱する。金型内部の深い領域まで高温にせず、表層を狙って高温にすることができる。このため、本実施形態の熱処理工程は、金型全体の硬度は下げずに水冷孔２の孔面３付近の硬度のみを下げたいという要求に極めて好都合である。また本実施形態の熱処理工程は、金型内部の深い領域まで加熱しないので、表層のみを短時間で目標温度に加熱して軟化することができる点でも優れている。
また、上述した特許文献１に記載の高周波熱処理装置では、底面４を効率的に加熱することができない。したがって、どうしても底面４の硬さを下げることが難しい。しかし本実施形態によれば、まず過熱蒸気が底面４に吹き付けられるため、底面４の硬さＨ１を簡単にかつ優先的に下げることができる。By the way, in the high-frequency heat treatment apparatus described in Patent Document 1 described above, the heating source heats the surrounding air, and the mold is heated through the heated air. Compared to the air of Patent Document 1, the superheated steam of this embodiment has extremely high thermal conductivity.
According to the present embodiment, the superheated steam having such high thermal conductivity moves in contact with the pore surface 3 and quickly heats up to the target temperature aiming at the polar surface layer of the pore surface 3. It is possible to aim at the surface layer and raise the temperature without raising the temperature to the deep area inside the mold. Therefore, the heat treatment step of the present embodiment is extremely convenient for the request that the hardness of the entire mold is not reduced but only the hardness of the water cooling hole 2 near the hole surface 3 is reduced. Further, since the heat treatment step of the present embodiment does not heat the deep region inside the mold, it is also excellent in that only the surface layer can be heated to the target temperature in a short time to be softened.
Further, the high-frequency heat treatment apparatus described in Patent Document 1 described above cannot efficiently heat the bottom surface 4. Therefore, it is difficult to reduce the hardness of the bottom surface 4. However, according to the present embodiment, since superheated steam is first blown to the bottom surface 4, the hardness H1 of the bottom surface 4 can be easily and preferentially lowered.

次に、熱処理の好ましい態様について詳しく説明する。図３は、水冷孔２の内部に管１０を挿入した様子を示す断面図である。図３に示すように、管１０の先端から水冷孔２の底面４の最深の位置Ａとの距離がｈとなるように、水冷孔２に管１０を挿入する。この距離ｈは、水冷孔２の直径（内径）Ｄと管１０の直径（外径）ｄを使って、下記式（１）を満たす位置に管１０の先端を保持して熱処理工程を行う。
０．５×（Ｄ−ｄ）／２ ≦ ｈ ≦ １．５×（Ｄ−ｄ）／２ 式（１）Next, a preferred embodiment of the heat treatment will be described in detail. FIG. 3 is a cross-sectional view showing a state in which the pipe 10 is inserted inside the water cooling hole 2. As shown in FIG. 3, the pipe 10 is inserted into the water cooling hole 2 so that the distance from the tip of the pipe 10 to the deepest position A of the bottom surface 4 of the water cooling hole 2 is h. For this distance h, the tip of the pipe 10 is held at a position satisfying the following formula (1) by using the diameter (inner diameter) D of the water cooling hole 2 and the diameter (outer diameter) d of the pipe 10, and the heat treatment step is performed.
0.5 × (Dd) / 2 ≦ h ≦ 1.5 × (Dd) / 2 Equation (1)

底面４に向かって管１０から吹き出された過熱蒸気は、底面４にぶつかった後に側面５に向かって流れ、側面５に沿って入口６に向かって流れる。ここで、管１０と底面４との離間距離ｈが、管１０の外面と水冷孔２の側面５との間の距離（Ｄ−ｄ）／２と近い大きさであることが好ましい。そこで上記式（１）を満たせば、管１０から底面４に向かって流れる過熱蒸気の流路の断面積が、側面５に沿って流れる過熱蒸気の流路の断面積に近くなる。このため、過熱蒸気の流れが妨げられにくく、底面４に向かった過熱蒸気が側面５に沿って流れやすくなる。これにより、側面５も効率的に過熱蒸気によって温められ、側面５の広い範囲を熱処理しやすくなる。このため、水冷孔２の底面４から側面５に至る領域を均一に加熱しやすく、この領域を確実に熱処理することができる。
式（１）において、ｈは、好ましくは「０．７×（Ｄ−ｄ）／２以上」であり、より好ましくは「０．８×（Ｄ−ｄ）／２以上」である。また、ｈは、好ましくは「１．３×（Ｄ−ｄ）／２以下」であり、より好ましくは「１．２×（Ｄ−ｄ）／２以下」である。The superheated steam blown out from the pipe 10 toward the bottom surface 4 flows toward the side surface 5 after hitting the bottom surface 4, and flows toward the inlet 6 along the side surface 5. Here, it is preferable that the separation distance h between the pipe 10 and the bottom surface 4 is close to the distance (Dd) / 2 between the outer surface of the pipe 10 and the side surface 5 of the water cooling hole 2. Therefore, if the above formula (1) is satisfied, the cross-sectional area of the superheated steam flow path flowing from the pipe 10 toward the bottom surface 4 becomes close to the cross-sectional area of the superheated steam flow path flowing along the side surface 5. Therefore, the flow of superheated steam is not easily obstructed, and the superheated steam toward the bottom surface 4 easily flows along the side surface 5. As a result, the side surface 5 is also efficiently heated by the superheated steam, and a wide range of the side surface 5 can be easily heat-treated. Therefore, it is easy to uniformly heat the region from the bottom surface 4 to the side surface 5 of the water cooling hole 2, and this region can be reliably heat-treated.
In the formula (1), h is preferably "0.7 × (Dd) / 2 or more", and more preferably “0.8 × (Dd) / 2 or more”. Further, h is preferably "1.3 x (Dd) / 2 or less", and more preferably "1.2 x (Dd) / 2 or less".

なお、上述した距離ｈの調整は、図２に示したダイカスト金型１の上部に取り付けた調整機構２０により行うことができる。調整機構２０は、過熱蒸気を流す管１０を支持する支持部２１と、水冷孔２の中心軸線Ａｘの方向に延びる第一調整ボルト２２と、水冷孔２の径方向に延びる第二調整ボルト２３とを有している。第一調整ボルト２２をねじ込むことにより、支持部２１とダイカスト金型１の上面１ｂとの距離を調整可能とされている。これにより、支持部２１と、支持部２１により支持された管１０を水冷孔２の中心軸線Ａｘ方向に変位させることができる。つまり、第一調整ボルト２２により距離ｈを調整することができる。
なお、第二調整ボルト２３により、管１０の水冷孔２内部の径方向の位置を調整することができる。The above-mentioned adjustment of the distance h can be performed by the adjustment mechanism 20 attached to the upper part of the die casting mold 1 shown in FIG. The adjustment mechanism 20 includes a support portion 21 that supports a pipe 10 through which superheated steam flows, a first adjustment bolt 22 that extends in the direction of the central axis Ax of the water cooling hole 2, and a second adjustment bolt 23 that extends in the radial direction of the water cooling hole 2. And have. By screwing in the first adjusting bolt 22, the distance between the support portion 21 and the upper surface 1b of the die casting die 1 can be adjusted. As a result, the support portion 21 and the pipe 10 supported by the support portion 21 can be displaced in the Ax direction of the central axis of the water cooling hole 2. That is, the distance h can be adjusted by the first adjusting bolt 22.
The position of the pipe 10 in the radial direction inside the water cooling hole 2 can be adjusted by the second adjusting bolt 23.

図３に戻り、管１０の先端は円錐台形状であることが好ましい。
水冷孔２はドリルで側面５を形成したときに、その底面４にドリル先端部の形状跡である隅（コーナー）が残る。そこで本実施形態において、この隅をなくして割れを生じ難くするために、底面４が半球状となるようにアール加工して水冷孔２を形成している。
管１０の先端が円錐台形状であると、このようにして加工された半球状の底面４に対応した形状となりやすく、管１０の先端と底面４との距離を広い範囲に亘って均一に保ちやすい。このため、過熱蒸気の流路の断面積を一定にしやすく、過熱蒸気の流れを妨げにくい。これにより、過熱蒸気を底面４から側面５に亘って円滑に流すことができ、底面４から側面５に亘る広い範囲を効率的に熱処理できる。Returning to FIG. 3, it is preferable that the tip of the tube 10 has a truncated cone shape.
When the side surface 5 of the water cooling hole 2 is formed by a drill, a corner, which is a trace of the shape of the tip of the drill, remains on the bottom surface 4. Therefore, in the present embodiment, in order to eliminate this corner and make it difficult for cracks to occur, the bottom surface 4 is rounded so as to be hemispherical to form the water cooling hole 2.
If the tip of the tube 10 has a truncated cone shape, the shape tends to correspond to the hemispherical bottom surface 4 processed in this way, and the distance between the tip of the tube 10 and the bottom surface 4 is kept uniform over a wide range. Cheap. Therefore, it is easy to make the cross section of the flow path of the superheated steam constant, and it is difficult to obstruct the flow of the superheated steam. As a result, superheated steam can be smoothly flowed from the bottom surface 4 to the side surface 5, and a wide range from the bottom surface 4 to the side surface 5 can be efficiently heat-treated.

また、このアール加工をした後の水冷孔２の底面４の形状は、水冷孔２の内径をＤとしたときに、底面４の中央からおおよそＤ／２の高さの位置を球の中心とした半球状となる。このため、底面４の最深の位置からＤ／２の高さ位置付近の側面５には、側面５を形成するときのドリルで形成された面と、アール加工する際に形成された面との境界７が位置する。ドリルの刃先の形状精度、アール加工する際の刃物の刃先の形状寸法などに起因して、この境界７に段差が生じることがある。このような段差も、ダイカスト金型１の割れの原因となる場合がある。
しかし本実施形態によれば、底面４から側面５に亘る広い範囲を効率的に熱処理して硬度を下げることができるため、段差が生じている場合であっても割れにくいダイカスト金型１を提供できる。Further, the shape of the bottom surface 4 of the water cooling hole 2 after this rounding is such that the position at a height of approximately D / 2 from the center of the bottom surface 4 is the center of the sphere when the inner diameter of the water cooling hole 2 is D. It becomes a hemispherical shape. Therefore, on the side surface 5 near the height position of D / 2 from the deepest position of the bottom surface 4, a surface formed by a drill when forming the side surface 5 and a surface formed during the rounding process are formed. Boundary 7 is located. A step may occur at the boundary 7 due to the shape accuracy of the cutting edge of the drill, the shape and dimensions of the cutting edge of the cutting tool during rounding, and the like. Such a step may also cause cracking of the die casting mold 1.
However, according to the present embodiment, since it is possible to efficiently heat-treat a wide range from the bottom surface 4 to the side surface 5 to reduce the hardness, the die-casting die 1 that is hard to break even when a step is generated is provided. it can.

なお、上述の説明では、水冷孔がダイカスト金型の上面に開口する例を説明したが、これに限られない。水冷孔はダイカスト金型の側面や下面に開口していてもよい。 In the above description, an example in which the water cooling hole opens on the upper surface of the die casting mold has been described, but the present invention is not limited to this. The water cooling holes may be opened on the side surface or the lower surface of the die casting mold.

＜φ１５の実施例＞
次に、本発明の実施例について説明する。図４は、実施例に係る製造方法で加工するダイカスト金型のテストピースの各部の寸法を示している。図４に示すように、本実施形態のテストピースは、縦１００ｍｍ、横１００ｍｍ、高さ１５０ｍｍの直方体の鋼材である。テストピースの上面の中央に、直径Ｄが１５ｍｍ、深さが１２０ｍｍの水冷孔が開口している。水冷孔は、入口から深さ１１２．５ｍｍまでの領域が円柱形状であり、深さ１１２．５ｍｍから１２０ｍｍまでの領域が半球状である。テストピースは、ＪＩＳ−Ｇ−４４０４の規格鋼種ＳＫＤ６１の鋼材からなる。そして、１０２０℃からの焼入れ処理と、これに続く６００℃での焼戻し処理とによって、Ｃスケールのロックウェル硬さで、４５ＨＲＣの狙い硬さに調整されている。<Example of φ15>
Next, examples of the present invention will be described. FIG. 4 shows the dimensions of each part of the test piece of the die casting die processed by the manufacturing method according to the embodiment. As shown in FIG. 4, the test piece of the present embodiment is a rectangular parallelepiped steel material having a length of 100 mm, a width of 100 mm, and a height of 150 mm. A water cooling hole having a diameter D of 15 mm and a depth of 120 mm is opened in the center of the upper surface of the test piece. The water cooling hole has a cylindrical shape in a region from the inlet to a depth of 112.5 mm and a hemispherical region in a depth of 112.5 mm to 120 mm. The test piece is made of a standard steel grade SKD61 of JIS-G-4404. Then, by quenching treatment from 1020 ° C. and subsequent tempering treatment at 600 ° C., the Rockwell hardness of C scale is adjusted to the target hardness of 45 HRC.

水冷孔の最深の位置Ａから高さ２ｍｍの位置（距離ｈ＝２ｍｍ）に、管の先端が位置するように、外径ｄが１２ｍｍの管を水冷孔に挿入した。過熱水蒸気発生装置にて１２００℃の過熱水蒸気を発生させ、管を介して水冷孔の内部に供給した。管の先端から水冷孔の底面に向けて過熱水蒸気を送り込み、底面を加熱して軟化させた。過熱水蒸気の供給を１時間３０分続けた。過熱水蒸気発生装置として、ＴＯＫＵＤＥＮ ＵＰＳＳ−Ｄ２０（登録商標）を用いた。 A pipe having an outer diameter d of 12 mm was inserted into the water cooling hole so that the tip of the pipe was located at a height of 2 mm (distance h = 2 mm) from the deepest position A of the water cooling hole. Superheated steam at 1200 ° C. was generated by a superheated steam generator and supplied to the inside of the water cooling hole through a pipe. Superheated steam was sent from the tip of the pipe toward the bottom of the water cooling hole, and the bottom was heated and softened. The supply of superheated steam was continued for 1 hour and 30 minutes. TOKUDEN UPSS-D20 (registered trademark) was used as the superheated steam generator.

図４に示すように、テストピースに第一温度測定点ａ１〜第五温度測定点ａ５を設定し、各測定点に熱電対を設置して、水冷孔に管を介して過熱水蒸気を送り込んでからの温度変化を測定した。
第一温度測定点ａ１は、水冷孔の最深の位置Ａから７．５ｍｍ（つまり、Ｄ／２）上方の円柱状領域と半球状領域との境界の高さ位置で、水冷孔の中心軸線Ａｘに対して直交する方向に孔面から１０ｍｍ金型の内部に入った位置に設けられている。
第二温度測定点ａ２は、水冷孔の中心軸線Ａｘ上で、水冷孔の最深の位置Ａから５ｍｍ下方の金型内部に設けられている。
第三温度測定点ａ３は、水冷孔の中心軸線Ａｘ上で、水冷孔の最深の位置Ａから２５ｍｍ下方の金型内部に設けられている。
第四温度測定点ａ４は、水冷孔の最深の位置Ａの孔面の表面上に設けられている。
第五温度測定点ａ５は、水冷孔の最深の位置Ａから７．５ｍｍ上方の円柱状領域と半球状領域との境界の高さ位置で、水冷孔の中心軸線Ａｘに対して直交する方向に孔面から５ｍｍ金型の内部に入った位置に設けられている。As shown in FIG. 4, the first temperature measurement point a1 to the fifth temperature measurement point a5 are set in the test piece, a thermocouple is installed at each measurement point, and superheated steam is sent to the water cooling hole through a pipe. The temperature change from was measured.
The first temperature measurement point a1 is the height position of the boundary between the columnar region and the hemispherical region 7.5 mm (that is, D / 2) above the deepest position A of the water cooling hole, and the central axis Ax of the water cooling hole. It is provided at a position inside the mold 10 mm from the hole surface in a direction orthogonal to the hole surface.
The second temperature measurement point a2 is provided inside the mold on the central axis Ax of the water cooling hole, 5 mm below the deepest position A of the water cooling hole.
The third temperature measurement point a3 is provided inside the mold 25 mm below the deepest position A of the water cooling hole on the central axis Ax of the water cooling hole.
The fourth temperature measurement point a4 is provided on the surface of the hole surface at the deepest position A of the water cooling hole.
The fifth temperature measurement point a5 is at the height of the boundary between the columnar region and the hemispherical region 7.5 mm above the deepest position A of the water cooling hole, in the direction orthogonal to the central axis Ax of the water cooling hole. It is provided at a position inside the mold 5 mm from the hole surface.

過熱水蒸気を供給した際の、各温度測定点で測定された温度履歴を図５に示す。
第四温度測定点ａ４の温度履歴から分かるように、過熱水蒸気の吹き付けを開始してすぐに、水冷孔の底面の表面温度が９００℃近くに上昇する。さらに吹き付け開始から３０分後に１０００℃程度に達し、その後は１時間３０分まで１０００℃が維持されている。
第二温度測定点ａ２および第五温度測定点ａ５は同様の温度履歴を示した。第二温度測定点ａ２および第五温度測定点ａ５のいずれも、吹き付け開始から３０分後に５５０℃程度まで上昇し、１時間後に６００℃程度に達する。その後は１時間３０分まで６００℃が維持されている。
第一温度測定点ａ１においては、吹き付け開始から３０分後に５００℃程度まで上昇し、１時間後に５７０℃程度に達する。その後は１時間３０分まで５７０℃が維持されている。
第三温度測定点ａ３においては、吹き付け開始から３０分後に４７０℃程度まで上昇し、１時間後に５２５℃程度に達する。その後は１時間３０分まで５２５℃が維持されている。FIG. 5 shows the temperature history measured at each temperature measurement point when superheated steam was supplied.
As can be seen from the temperature history of the fourth temperature measurement point a4, the surface temperature of the bottom surface of the water cooling hole rises to nearly 900 ° C. immediately after the start of spraying the superheated steam. Further, it reaches about 1000 ° C. 30 minutes after the start of spraying, and is maintained at 1000 ° C. for 1 hour and 30 minutes thereafter.
The second temperature measurement point a2 and the fifth temperature measurement point a5 showed a similar temperature history. Both the second temperature measurement point a2 and the fifth temperature measurement point a5 rise to about 550 ° C. 30 minutes after the start of spraying and reach about 600 ° C. one hour later. After that, the temperature is maintained at 600 ° C. for up to 1 hour and 30 minutes.
At the first temperature measurement point a1, the temperature rises to about 500 ° C. 30 minutes after the start of spraying and reaches about 570 ° C. 1 hour later. After that, the temperature is maintained at 570 ° C. for up to 1 hour and 30 minutes.
At the third temperature measurement point a3, the temperature rises to about 470 ° C. 30 minutes after the start of spraying and reaches about 525 ° C. one hour later. After that, the temperature is maintained at 525 ° C. for up to 1 hour and 30 minutes.

ＳＫＤ６１製のテストピースの今回の焼戻し温度は約６００℃である。この焼戻し温度を大きく超えて加熱された第四温度測定点ａ４は軟化されたと推測される。また、焼き戻し温度に達しなかった第一温度測定点ａ１、第三温度測定点ａ３は軟化しなかったものと推測される。 The tempering temperature of the test piece made of SKD61 this time is about 600 ° C. It is presumed that the fourth temperature measuring point a4, which was heated far beyond the tempering temperature, was softened. Further, it is presumed that the first temperature measurement point a1 and the third temperature measurement point a3, which did not reach the tempering temperature, did not soften.

そこで、過熱水蒸気の吹き付けをして得られたテストピースに図６に黒点で示した複数の位置を設定し、これらの位置について硬さを測定した。図６の（ａ）は水冷孔の中心軸線Ａｘに沿った断面図であり、図６の（ｂ）は水冷孔の中心軸線Ａｘに直交する面の断面図である。
図６の（ａ）に示すように、水冷孔の底面の最深の位置Ａから上方へ７．５ｍｍ（円柱状領域と半球状領域の境界）に位置する断面Ｂの硬さ、水冷孔の底面の最深の位置Ａから上方へ１５ｍｍに位置する断面Ｃの硬さ、水冷孔の底面の最深の位置Ａから上方へ１２０ｍｍに位置する面Ｅ（テストピースの上面１ｂ）の硬さを測定した。これにより、水冷孔の底面からの高さ方向における硬さの変化を確認する。
それぞれの高さ位置における面Ｂ，Ｃ，Ｅにおいて、図６の（ｂ）に示すように、周方向に互いの離間距離が等しい８つの軸線に沿って、それぞれ水冷孔の孔面表面から２ｍｍ、４ｍｍ、６ｍｍ、１０ｍｍ離間した位置の硬さを測定した。これにより、水冷孔の周方向の硬さの変化、および、水冷孔の孔面からの離間距離に応じた硬さの変化を確認する。
以上のように設定した合計９６（３×８×４）点の位置の硬さの測定結果を図７〜図９に示す。Therefore, a plurality of positions shown by black dots in FIG. 6 were set on the test piece obtained by spraying superheated steam, and the hardness was measured at these positions. FIG. 6A is a cross-sectional view taken along the central axis Ax of the water cooling hole, and FIG. 6B is a cross-sectional view of a plane orthogonal to the central axis Ax of the water cooling hole.
As shown in FIG. 6A, the hardness of the cross section B located at 7.5 mm (the boundary between the columnar region and the hemispherical region) upward from the deepest position A of the bottom surface of the water cooling hole, and the bottom surface of the water cooling hole. The hardness of the cross section C located 15 mm upward from the deepest position A of the water cooling hole and the hardness of the surface E (upper surface 1b of the test piece) located 120 mm upward from the deepest position A of the bottom surface of the water cooling hole were measured. In this way, the change in hardness in the height direction from the bottom surface of the water cooling hole is confirmed.
As shown in FIG. 6B, in the surfaces B, C, and E at the respective height positions, 2 mm from the surface of the water cooling hole along the eight axes having the same distance from each other in the circumferential direction. The hardness at positions separated by 4 mm, 6 mm and 10 mm was measured. As a result, the change in hardness in the circumferential direction of the water cooling hole and the change in hardness according to the distance from the hole surface of the water cooling hole are confirmed.
The measurement results of the hardness at the positions of a total of 96 (3 × 8 × 4) points set as described above are shown in FIGS. 7 to 9.

図７は、水冷孔の底面の最深の位置Ａから上方へ７．５ｍｍ（つまり、Ｄ／２）に位置する断面Ｂにおける硬さを示すレーダーチャートである。図８は、水冷孔の底面の最深の位置Ａから上方へ１５ｍｍに位置する断面Ｃにおける硬さを示すレーダーチャートである。図９は、テストピースの上面Ｅにおける硬さを示すレーダーチャートである。水冷孔の孔面からの離間距離が等しい測定点の硬さを示す点を結ぶ線で示している。なお、図７〜９の縦軸の硬さは、Ａスケールのロックウェル硬さＨＲＡで示している。 FIG. 7 is a radar chart showing the hardness in the cross section B located 7.5 mm (that is, D / 2) upward from the deepest position A on the bottom surface of the water cooling hole. FIG. 8 is a radar chart showing the hardness in the cross section C located 15 mm upward from the deepest position A on the bottom surface of the water cooling hole. FIG. 9 is a radar chart showing the hardness of the upper surface E of the test piece. It is shown by a line connecting the points indicating the hardness of the measurement points with the same distance from the hole surface of the water cooling hole. The hardness on the vertical axis in FIGS. 7 to 9 is indicated by A-scale Rockwell hardness HRA.

図７と図８に示すように、水冷孔に過熱水蒸気を供給することにより、水冷孔の近傍の領域が軟化することが確認できた。テストピースの狙い硬さである４５ＨＲＣ（ＨＲＡに換算して、約７３ＨＲＡ）に対して、水冷孔の孔面から６ｍｍ未満の領域の硬さが低下した。
また図７と図８より、水冷孔の孔面から離れるほど硬くなっていく傾向が読み取れる。つまり、離間距離が最も短い２ｍｍの位置の硬さはおよそ６９ＨＲＡであり、これをＨＲＣに換算すると約３７ＨＲＣである。これに対し、離間距離が４ｍｍの位置の硬さはおよそ７１ＨＲＡ（約４１ＨＲＣ）、離間距離が６ｍｍの位置の硬さはおよそ７２ＨＲＡ（約４３ＨＲＣ）、離間距離が１０ｍｍの位置の硬さはおよそ７３ＨＲＡ（約４５ＨＲＣ）であった。As shown in FIGS. 7 and 8, it was confirmed that the region near the water cooling hole was softened by supplying superheated steam to the water cooling hole. The hardness of the region less than 6 mm from the hole surface of the water cooling hole was reduced with respect to the target hardness of the test piece, 45 HRC (about 73 HRA in terms of HRA).
Further, from FIGS. 7 and 8, it can be seen that the water cooling hole tends to become harder as the distance from the hole surface increases. That is, the hardness at the position of 2 mm having the shortest separation distance is about 69 HRA, which is about 37 HRC when converted to HRC. On the other hand, the hardness at the position where the separation distance is 4 mm is about 71HRA (about 41HRC), the hardness at the position where the separation distance is 6 mm is about 72HRA (about 43HRC), and the hardness at the position where the separation distance is 10 mm is about 73HRA. It was (about 45 HRC).

図７と図８とを比較すると、水冷孔の孔面からの距離が等しくても、図７の断面Ｂは図８の断面Ｃよりも硬さが小さいことが読み取れる。断面Ｂは断面Ｃより、過熱水蒸気が吹き付けられる水冷孔の底面からの距離が近い。過熱水蒸気の供給中に断面Ｂは断面Ｃよりも高温となっている。このため、断面Ｂは断面Ｃよりも軟化が進み、軟らかくなったものと考えられる。
さらに、図９に示すように、水冷孔の底面から遠く離れた水冷孔の入口付近では、もはや過熱水蒸気の供給によっても温度が焼戻し温度付近まで上昇せず、軟化しなかったことが読み取れる。Comparing FIG. 7 and FIG. 8, it can be read that the cross section B of FIG. 7 is smaller in hardness than the cross section C of FIG. 8 even if the distances of the water cooling holes from the hole surface are the same. The cross section B is closer to the bottom surface of the water cooling hole into which the superheated steam is sprayed than the cross section C. The cross section B is hotter than the cross section C during the supply of superheated steam. Therefore, it is considered that the cross section B is softened more than the cross section C and becomes softer.
Further, as shown in FIG. 9, it can be read that in the vicinity of the inlet of the water cooling hole far from the bottom surface of the water cooling hole, the temperature did not rise to the vicinity of the tempering temperature even by the supply of superheated steam and did not soften.

図７と図８からは、孔面の表面から１０ｍｍ離れると軟化していないことが読み取れる。断面Ｂ，Ｃは、過熱水蒸気が吹き付けられる底面から比較的近い位置にある。しかし、孔面の表面から１０ｍｍ離れた領域は焼戻し温度に達することなく、軟化しなかった。また、図７と図８より、水冷孔の孔面の表面から４ｍｍ程度離れると、軟化はするものの、軟化しにくくなることが確認できる。 From FIGS. 7 and 8, it can be read that the holes are not softened at a distance of 10 mm from the surface of the hole surface. The cross sections B and C are located relatively close to the bottom surface on which superheated steam is sprayed. However, the region 10 mm away from the surface of the hole surface did not reach the tempering temperature and did not soften. Further, from FIGS. 7 and 8, it can be confirmed that when the water cooling hole is separated from the surface of the hole surface by about 4 mm, the water cooling hole softens but becomes difficult to soften.

次に、水冷孔の底面からの離間距離に応じた硬度の変化を評価した。図１０に示すように、方向ｓ〜方向ｕについて、水冷孔の底面からの離間距離に応じた硬度を測定した。
方向ｓ：水冷孔の底面の最深の位置Ａから下方に向かう方向について複数の点で硬さを測定した。
方向ｔ：半球状領域の球の中心Ｏから水冷孔の中心軸線Ａｘに対して４５°をなす方向について複数の点で硬さを測定した。
方向ｕ：半球状領域の球の中心Ｏから水冷孔の中心軸線Ａｘに対して４５°をなす方向について複数の点で硬さを測定した。方向ｕは、方向ｔに対して、水冷孔の中心軸線Ａｘ回りに１８０°離れた位置にある。Next, the change in hardness according to the distance from the bottom surface of the water cooling hole was evaluated. As shown in FIG. 10, the hardness was measured in the directions s to u according to the distance from the bottom surface of the water cooling hole.
Direction s: Hardness was measured at a plurality of points in the downward direction from the deepest position A on the bottom surface of the water cooling hole.
Direction t: Hardness was measured at a plurality of points in a direction forming 45 ° from the center O of the sphere in the hemispherical region with respect to the central axis Ax of the water cooling hole.
Direction u: Hardness was measured at a plurality of points in a direction forming 45 ° from the center O of the sphere in the hemispherical region to the central axis Ax of the water cooling hole. The direction u is located 180 ° away from the direction t around the central axis Ax of the water cooling hole.

図１１に、水冷孔の底面からの離間距離に応じた硬度の変化を示す。なお、図１１の縦軸の硬さはＨＲＣで示している。図１１に示すように、水冷孔の底面の最深の位置Ａの硬さは約３０ＨＲＣであり、テストピースの狙い硬さである４５ＨＲＣに対して大きく軟化していた。そして、方向ｓ〜ｕのいずれの方向の点についても底面から離れるにしたがって硬くなる傾向を有する。特に底面から４ｍｍも離れると軟化しにくくなることが読み取れ、離間距離が５ｍｍの位置では、もはやテストピースの狙い硬さである４５ＨＲＣと同等である。一方で、離間距離が０〜２ｍｍの範囲では硬さが大きく低化していることが読み取れる。 FIG. 11 shows the change in hardness according to the distance from the bottom surface of the water cooling hole. The hardness of the vertical axis in FIG. 11 is indicated by HRC. As shown in FIG. 11, the hardness of the deepest position A at the bottom surface of the water cooling hole was about 30 HRC, which was significantly softened with respect to the target hardness of the test piece, 45 HRC. Then, points in any of the directions s to u tend to become harder as they move away from the bottom surface. In particular, it can be read that softening becomes difficult when the distance from the bottom surface is as much as 4 mm, and at a position where the separation distance is 5 mm, it is already equivalent to the target hardness of the test piece, 45HRC. On the other hand, it can be read that the hardness is greatly reduced in the range of 0 to 2 mm.

また、図１１に示すように、方向ｓ〜ｕはほぼ同様の硬さを示している。したがって、水冷孔の半球状領域においては、過熱水蒸気による熱が均等に広がり、水冷孔の半球状領域は均等に軟化が進んでいる。もっとも、管から噴き出される過熱水蒸気が最初にぶつかる半球状頂点に相当する領域は、高温になりやすく最も軟化が進むことがわかる。 Further, as shown in FIG. 11, the directions s to u show substantially the same hardness. Therefore, in the hemispherical region of the water cooling hole, the heat generated by the superheated steam spreads evenly, and the hemispherical region of the water cooling hole is uniformly softened. However, it can be seen that the region corresponding to the hemispherical apex where the superheated steam ejected from the pipe first collides tends to become hot and softens most.

図１２は、以上のような硬さの測定に基づき、金型内部の領域において入口硬さの９５％以下の硬さ（つまり、４５ＨＲＣに対して、４２．７５ＨＲＣ以下）となる領域（以降、軟化領域ＳＦと呼ぶ）を示した模式図である。
底面の最深の位置Ａから水冷孔の径方向と直角する方向における軟化領域ＳＦの厚みをＤ１と呼ぶ。底面の最深の位置Ａから高さＤ／２の位置の側面から水冷孔の径方向における軟化領域ＳＦの厚みをＤ２と呼ぶ。すると、図１２に示すように、厚みＤ１は厚みＤ２より小さい。
水冷孔の底面から底に向かう方向には成形面が設けられているため、この方向には軟化部を大きく形成したくない。本実施例のように、厚みＤ１が厚みＤ２より小さいと、軟化領域ＳＦを水冷孔の周囲に大きく形成しつつ、成形面の近傍の硬さを維持しやすい。
なお、Ｄ１、Ｄ２に関する上記の「厚み」とは、水冷孔の孔面に対して垂直な方向に延びる寸法を言う。図１２の水冷孔の場合、Ｄ１の厚みが定義される方向とＤ２の厚みが定義される方向とは直交している。FIG. 12 shows a region (hereinafter, 42.75 HRC or less with respect to 45 HRC) that is 95% or less of the inlet hardness in the region inside the mold based on the hardness measurement as described above. It is a schematic diagram which showed the softening region SF).
The thickness of the softening region SF in the direction perpendicular to the radial direction of the water cooling hole from the deepest position A on the bottom surface is called D1. The thickness of the softening region SF in the radial direction of the water cooling hole from the side surface at the position of the height D / 2 from the deepest position A on the bottom surface is called D2. Then, as shown in FIG. 12, the thickness D1 is smaller than the thickness D2.
Since the molding surface is provided in the direction from the bottom surface of the water cooling hole to the bottom, it is not desired to form a large softened portion in this direction. When the thickness D1 is smaller than the thickness D2 as in this embodiment, it is easy to maintain the hardness in the vicinity of the molded surface while forming a large softening region SF around the water cooling hole.
The above-mentioned "thickness" with respect to D1 and D2 means a dimension extending in a direction perpendicular to the hole surface of the water cooling hole. In the case of the water cooling hole of FIG. 12, the direction in which the thickness of D1 is defined and the direction in which the thickness of D2 is defined are orthogonal to each other.

図１３は、ダイカスト金型の各部の硬さを示す図である。
本実施例において、水冷孔の孔面のうち、底面の最深の位置Ａから高さＤ（Ｄ＝水冷孔の直径）の位置までの領域の硬さＨ３（該領域の平均の硬さ）が、入口硬さＨ２よりも低い。
図６に示したように、断面Ｃは底面の最深の位置Ａから高さＤの位置の断面である。断面Ｃの硬さを示す図８より、底面の最深の位置Ａから高さＤの位置の孔面（離間距離０ｍｍ）の硬さは６７ＨＲＡ（約３３ＨＲＣ）未満となることが読み取れる。また、図７と図８とを合わせて参照すると、高さＤよりも位置Ａに近い領域の硬さは、高さＤにおける硬さよりも低くなることが読み取れる。したがって、底面の最深の位置Ａから高さＤの位置までの領域の硬さＨ３は、６７ＨＲＡ（約３３ＨＲＣ）未満となることが読み取れる。
一方で、図９は入口硬さＨ２を示している。図９より、入口硬さＨ２は７３ＨＲＡと読み取れ、これは約４５ＨＲＣ（テストピースの狙い硬さ）である。
したがって本実施例において、硬さＨ３は硬さＨ２よりも低くなっている。水冷孔の底面と側面のそれぞれの硬さが入口硬さＨ２より下げられているため、水冷孔の周囲から割れが生じにくいダイカスト金型を提供できる。FIG. 13 is a diagram showing the hardness of each part of the die casting mold.
In this embodiment, the hardness H3 (average hardness of the region) of the region from the deepest position A to the height D (D = diameter of the water cooling pore) on the bottom surface of the hole surface of the water cooling hole is , The entrance hardness is lower than H2.
As shown in FIG. 6, the cross section C is a cross section at a position from the deepest position A to the height D of the bottom surface. From FIG. 8 showing the hardness of the cross section C, it can be read that the hardness of the hole surface (separation distance 0 mm) at the position from the deepest position A to the height D of the bottom surface is less than 67 HRA (about 33 HRC). Further, referring to FIGS. 7 and 8 together, it can be read that the hardness of the region closer to the position A than the height D is lower than the hardness at the height D. Therefore, it can be read that the hardness H3 of the region from the deepest position A to the height D on the bottom surface is less than 67 HRA (about 33 HRC).
On the other hand, FIG. 9 shows the entrance hardness H2. From FIG. 9, the entrance hardness H2 can be read as 73HRA, which is about 45HRC (the target hardness of the test piece).
Therefore, in this embodiment, the hardness H3 is lower than the hardness H2. Since the hardness of each of the bottom surface and the side surface of the water cooling hole is lower than the inlet hardness H2, it is possible to provide a die casting mold in which cracks are less likely to occur from around the water cooling hole.

本実施例において、半球状領域の球の中心Ｏから水冷孔の中心軸線Ａｘの方向に金型内部に向かって１ｍｍ入った位置の金型内部の硬さＨ１２が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、入口硬さＨ２の９５％より低い。
硬さＨ１２は、図１０の方向ｓに沿った硬さの変化を示す図１１から読み取ることができる。図１１のｓの線において、離間距離１ｍｍの位置の硬さはおよそ４０ＨＲＣである。入口硬さＨ２である７３ＨＲＡはおよそ４５ＨＲＣに相当する。入口硬さＨ２の９５％は４２．７５ＨＲＣである。したがって本実施例において、Ｈ１２＜０．９５×Ｈ２が成立している。そして、これについては、上記の硬さＨ１２が、入口の硬さＨ２の９０％の硬さ（４０．５ＨＲＣ）よりも低くなっており、水冷孔の割れの抑制に更に効果的である。なお、半球状領域の球の中心Ｏから水冷孔の中心軸線Ａｘに対して４５°をなす方向に金型内部に向かって１ｍｍ入った位置の金型内部の硬さも、入口硬さＨ２の９５％より低くなっている。そして更には、９０％より低くなっている。水冷孔の底面に向かって吹き付けられた過熱蒸気により、管の直下のみならず底面の最深の位置Ａから高さＤ／２の位置の孔面についても軟化される。In this embodiment, the hardness H12 inside the mold at a position 1 mm from the center O of the sphere in the hemispherical region toward the inside of the mold in the direction of the central axis Ax of the water cooling hole is the Rockwell hardness of the C scale. When compared by HRC, it is lower than 95% of the entrance hardness H2.
The hardness H12 can be read from FIG. 11, which shows the change in hardness along the direction s in FIG. In the line s of FIG. 11, the hardness at the position where the separation distance is 1 mm is about 40 HRC. 73HRA, which is the entrance hardness H2, corresponds to approximately 45HRC. 95% of the entrance hardness H2 is 42.75 HRC. Therefore, in this embodiment, H12 <0.95 × H2 is established. Regarding this, the hardness H12 is lower than the hardness of 90% (40.5 HRC) of the hardness H2 at the inlet, which is more effective in suppressing the cracking of the water cooling hole. The hardness inside the mold at a position 1 mm from the center O of the sphere in the hemispherical region toward the inside of the mold in a direction forming 45 ° with respect to the central axis Ax of the water cooling hole is also 95 of the inlet hardness H2. It is lower than%. And even more, it is below 90%. The superheated steam blown toward the bottom surface of the water cooling hole softens not only the hole surface directly below the pipe but also the hole surface at a height D / 2 from the deepest position A on the bottom surface.

本実施例において、底面の最深の位置Ａから金型内部に向かって、水冷孔の軸方向に５ｍｍ入った位置の金型内部の硬さＨ１５が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、入口硬さＨ２の９５％より高い。
図１１のｓの線において、離間距離５ｍｍの点より、硬さＨ１５はおよそ４５ＨＲＣである。一方で、７３ＨＲＡである入口硬さＨ２の９５％は約４２．７５ＨＲＣである。したがって、本実施例においてＨ１５＞０．９５×Ｈ２が成立している。そして、これについては、上記の硬さＨ１５が、入口の硬さＨ２の９７％の硬さ（４３．６５ＨＲＣ）よりも高くなっており、成形面の硬さの維持に更に効果的である。
成形面には所定の硬さが求められる。本実施例とは異なり、熱処理により軟化する領域が大きく、底面の最深の位置から５ｍｍより離れた領域まで軟らかくなってしまうと、軟化が金型の成形面にまで及んでしまうことがある。すると、水冷孔を成形面の近くまで設けることが難しくなってしまう。この点において、本発明に関する過熱蒸気を利用した軟化熱処理であれば、特に水冷孔の底面において金型内部が軟化する熱影響部を浅くできるので、上記の軟化領域ＳＦの厚みを小さくすることが可能である。また、逆に熱処理により軟化する領域が小さく、十分に軟らかくなっている領域が１ｍｍより浅いと、水冷孔に近い領域で軟らかくなっていない領域に割れが生じやすくなってしまう。In this embodiment, the hardness H15 inside the mold at a position 5 mm in the axial direction of the water cooling hole from the deepest position A on the bottom surface toward the inside of the mold was compared with the Rockwell hardness HRC on the C scale. Sometimes it is higher than 95% of the entrance hardness H2.
In the line s of FIG. 11, the hardness H15 is about 45 HRC from the point where the separation distance is 5 mm. On the other hand, 95% of the entrance hardness H2, which is 73HRA, is about 42.75HRC. Therefore, in this embodiment, H15> 0.95 × H2 is established. Regarding this, the hardness H15 is higher than the hardness of 97% (43.65 HRC) of the hardness H2 at the inlet, which is more effective in maintaining the hardness of the molded surface.
The molded surface is required to have a predetermined hardness. Unlike this embodiment, the region softened by the heat treatment is large, and if the region softens to a region more than 5 mm away from the deepest position on the bottom surface, the softening may extend to the molding surface of the mold. Then, it becomes difficult to provide the water cooling hole close to the molding surface. In this respect, in the softening heat treatment using superheated steam according to the present invention, the heat-affected zone where the inside of the mold softens can be made shallow especially at the bottom surface of the water cooling hole, so that the thickness of the softening region SF can be reduced. It is possible. On the contrary, if the region softened by the heat treatment is small and the region that is sufficiently softened is shallower than 1 mm, cracks are likely to occur in the region close to the water cooling hole that is not softened.

本実施例において、底面の最深の位置Ａから高さＤ／２（水冷孔の半球状領域と円柱状領域の境界）の位置の水冷孔の側面から金型内部に向かって水冷孔の径方向に３ｍｍ入った位置の金型内部の硬さＨ３３が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、入口の硬さＨ２の９５％より低い。
硬さＨ３３は、図６における断面Ｂの硬さを示す図７から読み取れる。図７より、硬さＨ３３は、２ｍｍと４ｍｍの線の間のおよそ７０ＨＲＡであり、換算すると約３９ＨＲＣである。一方で、入口の硬さＨ２は約４５ＨＲＣであり、Ｈ２の９５％は約４２．７５ＨＲＣである。本実施例において、Ｈ３３＜０．９５×Ｈ２が成立している。そして、これについては、上記の硬さＨ３３が、入口の硬さＨ２の９０％の硬さ（４０．５ＨＲＣ）よりも低くなっており、水冷孔の割れの抑制に更に効果的である。In this embodiment, the radial direction of the water cooling hole from the side surface of the water cooling hole at the position of height D / 2 (the boundary between the hemispherical region and the columnar region of the water cooling hole) from the deepest position A on the bottom surface toward the inside of the mold. The hardness H33 inside the mold at the position of 3 mm is lower than 95% of the hardness H2 at the entrance when compared with the Rockwell hardness HRC of the C scale.
The hardness H33 can be read from FIG. 7, which shows the hardness of the cross section B in FIG. From FIG. 7, the hardness H33 is approximately 70 HRA between the 2 mm and 4 mm lines, which translates to approximately 39 HRC. On the other hand, the hardness H2 at the entrance is about 45 HRC, and 95% of H2 is about 42.75 HRC. In this embodiment, H33 <0.95 × H2 is established. Regarding this, the hardness H33 is lower than the hardness of 90% (40.5HRC) of the hardness H2 at the inlet, which is more effective in suppressing the cracking of the water cooling hole.

本実施例において、底面の最深の位置Ａから高さＤ／２（水冷孔の半球状領域と円柱状領域の境界）の位置の水冷孔の側面から金型内部に向かって水冷孔の径方向に７ｍｍ入った位置の金型内部の硬さＨ３７が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、入口の硬さＨ２の９５％より高い。
硬さＨ３７は、図６における断面Ｂの硬さを示す図７から読み取れる。図７より、硬さＨ３７は、６ｍｍと１０ｍｍの線の間のおよそ７２．５ＨＲＡであり、換算すると約４４ＨＲＣである。一方で、入口の硬さＨ２の９５％は約４２．７５ＨＲＣである。本実施例において、Ｈ３７＞０．９５×Ｈ２が成立している。そして、これについては、上記の硬さＨ３７が、入口の硬さＨ２の９７％の硬さ（４３．６５ＨＲＣ）よりも高くなっており、金型自体の硬さの維持に更に効果的である。
水冷孔から７ｍｍより離れた領域まで軟化させてしまうと金型自体の硬さを低下させてしまうおそれがある。また、軟らかくなっている領域が３ｍｍより浅いと、水冷孔に近い領域で軟らかくなっていない領域に割れが生じやすくなってしまう。In this embodiment, the radial direction of the water cooling hole from the side surface of the water cooling hole at the position of height D / 2 (the boundary between the hemispherical region and the columnar region of the water cooling hole) from the deepest position A on the bottom surface toward the inside of the mold. The hardness H37 inside the mold at the position where 7 mm is inserted is higher than 95% of the hardness H2 at the entrance when compared with the Rockwell hardness HRC of C scale.
The hardness H37 can be read from FIG. 7, which shows the hardness of the cross section B in FIG. From FIG. 7, the hardness H37 is approximately 72.5 HRA between the 6 mm and 10 mm lines, which translates to approximately 44 HRC. On the other hand, 95% of the hardness H2 at the entrance is about 42.75 HRC. In this embodiment, H37> 0.95 × H2 is established. Regarding this, the above-mentioned hardness H37 is higher than the hardness of 97% (43.65 HRC) of the hardness H2 at the entrance, which is more effective in maintaining the hardness of the mold itself. ..
If it is softened to a region more than 7 mm away from the water cooling hole, the hardness of the mold itself may be reduced. Further, if the softened region is shallower than 3 mm, cracks are likely to occur in the non-softened region in the region close to the water cooling hole.

＜φ２０の実施例＞
次に、上述したφ１５を設けたテストピースと同じ大きさのテストピースに、直径Ｄが２０ｍｍ、深さが１２０ｍｍの水冷孔を形成し、同様に過熱水蒸気を水冷孔の底面に吹き付けた。φ２０のテストピースについても、上述したφ１５のテストピースと同様に温度履歴、硬さを測定した。水冷孔の最深の位置Ａから高さ３ｍｍの位置（距離ｈ＝３ｍｍ）に、管の先端が位置するように、外径ｄが１５ｍｍの管を水冷孔に挿入した。<Example of φ20>
Next, a water cooling hole having a diameter D of 20 mm and a depth of 120 mm was formed in the test piece having the same size as the test piece provided with φ15 described above, and superheated steam was similarly sprayed onto the bottom surface of the water cooling hole. The temperature history and hardness of the φ20 test piece were measured in the same manner as the φ15 test piece described above. A pipe having an outer diameter d of 15 mm was inserted into the water cooling hole so that the tip of the pipe was located at a height of 3 mm (distance h = 3 mm) from the deepest position A of the water cooling hole.

図１４に示すように、テストピースに第一温度測定点ｂ１〜第五温度測定点ｂ５を設定し、各測定点に熱電対を設置して、水冷孔に管を介して過熱水蒸気を送り込んでからの温度変化を測定した。
第一温度測定点ｂ１は、水冷孔の最深の位置Ａから１０ｍｍ（つまり、Ｄ／２）上方の円柱状領域と半球状領域との境界の高さ位置で、水冷孔の中心軸線Ａｘに対して直交する方向に孔面から１０ｍｍ金型の内部に入った位置に設けられている。
第二温度測定点ｂ２は、水冷孔の中心軸線Ａｘ上で、水冷孔の最深の位置Ａから５ｍｍ下方の金型内部に設けられている。
第三温度測定点ｂ３は、水冷孔の中心軸線Ａｘ上で、水冷孔の最深の位置Ａから２５ｍｍ下方の金型内部に設けられている。
第四温度測定点ｂ４は、水冷孔の最深の位置Ａの孔面の表面上に設けられている。
第五温度測定点ｂ５は、水冷孔の最深の位置Ａから１０ｍｍ上方の円柱状領域と半球状領域との境界の高さ位置で、水冷孔の中心軸線Ａｘに対して直交する方向に孔面から５ｍｍ金型の内部に入った位置に設けられている。As shown in FIG. 14, the first temperature measurement point b1 to the fifth temperature measurement point b5 are set in the test piece, a thermocouple is installed at each measurement point, and superheated steam is sent to the water cooling hole through a pipe. The temperature change from was measured.
The first temperature measurement point b1 is the height position of the boundary between the columnar region and the hemispherical region 10 mm (that is, D / 2) above the deepest position A of the water cooling hole, with respect to the central axis Ax of the water cooling hole. It is provided at a position inside the mold 10 mm from the hole surface in the direction orthogonal to each other.
The second temperature measurement point b2 is provided inside the mold on the central axis Ax of the water cooling hole, 5 mm below the deepest position A of the water cooling hole.
The third temperature measurement point b3 is provided inside the mold 25 mm below the deepest position A of the water cooling hole on the central axis Ax of the water cooling hole.
The fourth temperature measurement point b4 is provided on the surface of the hole surface at the deepest position A of the water cooling hole.
The fifth temperature measurement point b5 is the height position of the boundary between the columnar region and the hemispherical region 10 mm above the deepest position A of the water cooling hole, and the hole surface in the direction orthogonal to the central axis Ax of the water cooling hole. It is provided at a position inside the 5 mm mold.

図１５は、図５と同様の温度履歴を示すグラフである。図１５に示すように、図５のφ１５のテストピースの温度履歴と同様の温度履歴となった。第一温度測定点ｂ１、第二温度測定点ｂ２、第五温度測定点ｂ５でほぼ同じ温度履歴となった。これは、φ１５の水冷孔に比べて水冷孔の直径が大きくなったため、水冷孔の底面から側面に過熱水蒸気が流れ込みやすくなり、側面の温度が上がりやすくなり第一温度測定点の温度が高まったものと思われる。 FIG. 15 is a graph showing the same temperature history as in FIG. As shown in FIG. 15, the temperature history was similar to the temperature history of the φ15 test piece of FIG. The temperature history was almost the same at the first temperature measurement point b1, the second temperature measurement point b2, and the fifth temperature measurement point b5. This is because the diameter of the water cooling hole is larger than that of the φ15 water cooling hole, so that superheated steam easily flows from the bottom surface to the side surface of the water cooling hole, the temperature of the side surface tends to rise, and the temperature of the first temperature measurement point rises. It seems to be.

図１６は、図７と同様の硬さのばらつきを示すレーダーチャートである。図１７は、図８と同様の硬さのばらつきを示すレーダーチャートである。図１８は、図９と同様の硬さのばらつきを示すレーダーチャートである。図１６は、水冷孔の底面の最深の位置Ａから上方へ１０ｍｍ（円柱状領域と半球状領域の境界）に位置する断面における硬さのばらつきを示す。図１７は、水冷孔の底面の最深の位置Ａから上方へ２０ｍｍに位置する断面における硬さのばらつきを示す。図１８は、テストピースの上面の硬さのばらつきを示す。
図１９は、図１１と同様の水冷孔の孔面からの離間距離と硬さの関係を示すグラフである。
図１６〜図１９を図７〜図９、図１１と比較すると、φ２０の水冷孔が形成されたテストピースにおいてもφ１５の水冷孔が形成されたテストピースと同様に軟化されていることが確認できた。FIG. 16 is a radar chart showing the same hardness variation as in FIG. 7. FIG. 17 is a radar chart showing variations in hardness similar to those in FIG. FIG. 18 is a radar chart showing the same hardness variation as in FIG. FIG. 16 shows the variation in hardness in the cross section located 10 mm upward (the boundary between the columnar region and the hemispherical region) from the deepest position A on the bottom surface of the water cooling hole. FIG. 17 shows the variation in hardness in the cross section located 20 mm upward from the deepest position A on the bottom surface of the water cooling hole. FIG. 18 shows variations in hardness of the upper surface of the test piece.
FIG. 19 is a graph showing the relationship between the distance from the hole surface and the hardness of the water cooling hole similar to that in FIG.
Comparing FIGS. 16 to 19 with FIGS. 7 to 9 and 11, it was confirmed that the test piece having the water cooling hole of φ20 was softened in the same manner as the test piece having the water cooling hole of φ15. did it.

本出願は、2016年11月22日出願の日本特許出願（特願2016-226449）に基づくものであり、その内容はここに参照として取り込まれる。 This application is based on a Japanese patent application filed on November 22, 2016 (Japanese Patent Application No. 2016-226449), the contents of which are incorporated herein by reference.

本発明によれば、水冷孔の底面を含む領域に確実に軟化熱処理を施すことができるダイカスト金型の製造方法およびダイカスト金型が提供される。 According to the present invention, there is provided a method for manufacturing a die-casting die and a die-casting die capable of reliably performing a softening heat treatment on a region including the bottom surface of a water cooling hole.

１ ダイカスト金型
２ 水冷孔
３ 孔面
４ 底面
５ 側面
６ 入口
７ （半球状領域と円柱状領域の）境界
１０ 管
1 Die casting mold 2 Water cooling hole 3 Hole surface 4 Bottom surface 5 Side surface 6 Inlet 7 Boundary (hemispherical region and columnar region) 10 pipe

Claims (12)

内径Ｄの有底の水冷孔が設けられたダイカスト金型の製造方法であって、
前記水冷孔をなす孔面は、前記水冷孔の底をなす底面と、前記底面から入口に向かって延びる側面を有し、
前記水冷孔に挿入した外径ｄの管の先端から前記底面に向けて過熱蒸気を送り込み、前記底面を加熱して軟化させる熱処理工程を有する、ダイカスト金型の製造方法。 This is a method for manufacturing a die casting die provided with a bottomed water cooling hole having an inner diameter D.
The hole surface forming the water cooling hole has a bottom surface forming the bottom of the water cooling hole and a side surface extending from the bottom surface toward the inlet.
A method for manufacturing a die casting mold, which comprises a heat treatment step of sending superheated steam from the tip of a pipe having an outer diameter d inserted into the water cooling hole toward the bottom surface to heat and soften the bottom surface. 前記管の先端と前記底面の最深の位置との離間距離をｈと定義したとき、
０．５×（Ｄ−ｄ）／２ ≦ ｈ ≦ １．５×（Ｄ−ｄ）／２
となる位置に前記管の先端を保持して前記熱処理工程を行う、請求項１に記載のダイカスト金型の製造方法。 When the distance between the tip of the pipe and the deepest position of the bottom surface is defined as h,
0.5 × (Dd) / 2 ≦ h ≦ 1.5 × (Dd) / 2
The method for manufacturing a die casting die according to claim 1, wherein the tip of the pipe is held at a position where the pipe is located, and the heat treatment step is performed. 前記管の先端が円錐台形状である、請求項１に記載のダイカスト金型の製造方法。 The method for manufacturing a die casting die according to claim 1, wherein the tip of the tube has a truncated cone shape. 前記底面が半球状となるように加工して前記水冷孔を形成する、請求項１に記載のダイカスト金型の製造方法。 The method for manufacturing a die casting die according to claim 1, wherein the bottom surface is processed to have a hemispherical shape to form the water cooling hole. 内径Ｄの有底の水冷孔が設けられたダイカスト金型であって、
前記水冷孔をなす孔面は、前記水冷孔の底をなす底面と、前記底面から入口に向かって延びる側面を有し、
前記底面の最深の位置の硬さＨ１が、Ａスケールのロックウェル硬さＨＲＡで比較したときに、前記水冷孔の入口の入口硬さＨ２よりも低い、ダイカスト金型。 A die-casting die provided with a bottomed water cooling hole with an inner diameter D.
The hole surface forming the water cooling hole has a bottom surface forming the bottom of the water cooling hole and a side surface extending from the bottom surface toward the inlet.
A die casting mold in which the hardness H1 at the deepest position of the bottom surface is lower than the inlet hardness H2 at the inlet of the water cooling hole when compared with the Rockwell hardness HRA of A scale . 前記孔面のうち、前記底面の最深の位置から高さＤの位置までの領域の硬さＨ３が、Ａスケールのロックウェル硬さＨＲＡで比較したときに、前記入口硬さＨ２より低い、請求項５に記載のダイカスト金型。 Claimed that the hardness H3 of the region of the hole surface from the deepest position of the bottom surface to the position of height D is lower than the inlet hardness H2 when compared with the Rockwell hardness HRA of A scale. Item 5. The die casting mold according to Item 5. 前記底面の最深の位置から金型内部に向かって、前記水冷孔の径方向と直角の方向に１ｍｍ入った位置の金型内部の硬さＨ１２が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％より低い、請求項５に記載のダイカスト金型。 The hardness H12 inside the mold at a position 1 mm from the deepest position on the bottom surface toward the inside of the mold in the direction perpendicular to the radial direction of the water cooling hole was compared with the Rockwell hardness HRC of the C scale. The die casting die according to claim 5, which is sometimes lower than 95% of the inlet hardness H2. 前記底面の最深の位置から金型内部に向かって、前記水冷孔の径方向と直角の方向に５ｍｍ入った位置の金型内部の硬さＨ１５が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％より高い、請求項５に記載のダイカスト金型。 The hardness H15 inside the mold at a position 5 mm in the direction perpendicular to the radial direction of the water cooling hole from the deepest position on the bottom surface toward the inside of the mold was compared with the C scale Rockwell hardness HRC. The die casting die according to claim 5, which is sometimes higher than 95% of the inlet hardness H2. 前記底面の最深の位置から高さＤ／２の位置の前記側面から金型内部に向かって前記水冷孔の径方向に３ｍｍ入った位置の金型内部の硬さＨ３３が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口の硬さＨ２の９５％より低い、請求項５に記載のダイカスト金型。 The hardness H33 inside the mold at a position 3 mm in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface toward the inside of the mold is a C-scale Rockwell. The die casting die according to claim 5, which is lower than 95% of the hardness H2 of the inlet when compared in terms of hardness HRC. 前記底面の最深の位置から高さＤ／２の位置の前記側面から金型内部に向かって前記水冷孔の径方向に７ｍｍ入った位置の金型内部の硬さＨ３７が、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口の硬さＨ２の９５％より高い、請求項５に記載のダイカスト金型。 The hardness H37 inside the mold at a position 7 mm in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface toward the inside of the mold is a C-scale Rockwell. The die casting die according to claim 5, which is higher than 95% of the hardness H2 of the inlet when compared in terms of hardness HRC. 金型内部の領域において、Ｃスケールのロックウェル硬さＨＲＣで比較したときに、前記入口硬さＨ２の９５％以下となっている領域を軟化領域と呼び、
前記底面の最深の位置から前記水冷孔の径方向と直角する方向における前記軟化領域の厚みをＤ１と呼び、
前記底面の最深の位置から高さＤ／２の位置の前記側面から前記水冷孔の径方向における前記軟化領域の厚みをＤ２と呼ぶとき、
前記厚みＤ１が前記厚みＤ２より小さい、請求項５に記載のダイカスト金型。 In the region inside the mold, the region where the Rockwell hardness HRC of the C scale is 95% or less of the entrance hardness H2 is called a softening region.
The thickness of the softened region in the direction perpendicular to the radial direction of the water cooling hole from the deepest position of the bottom surface is called D1.
When the thickness of the softened region in the radial direction of the water cooling hole from the side surface at a height D / 2 from the deepest position of the bottom surface is referred to as D2.
The die casting die according to claim 5, wherein the thickness D1 is smaller than the thickness D2. 前記底面が半球状である、請求項５に記載のダイカスト金型。 It said bottom surface is a hemispherical die-casting die of claim 5.
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