JPH0321257B2

JPH0321257B2 -

Info

Publication number: JPH0321257B2
Application number: JP63027442A
Authority: JP
Inventors: Toshio Ogiwara; Hideaki Ootake; Masaaki Kudo
Original assignee: Izumi Automotive Industry Co Ltd
Current assignee: Mahle Engine Components Japan Corp
Priority date: 1988-02-10
Filing date: 1988-02-10
Publication date: 1991-03-22
Also published as: JPH01205846A

Description

[Detailed description of the invention]

〔産業上の利用分野〕本発明は、溶融金属を鋳込んで各種鋳造品を精
密に形成するための金属鋳造用金型の改良に関す
る。〔従来の技術〕溶融金属を鋳型内のキヤビテイ部に鋳込んで精
密な鋳造品を大量生産する場合、その鋳型には一
般に金属鋳造用金型が広く用いられている。この種金属鋳造では精密な鋳物が得られるが、
金型は鋳込まれる溶融金属を冷却する力が大きい
ので溶融金属の温度の急変によりガスが発生し、
その発生ガスの圧力及び湯温の低下等により、溶
融金属の充填が不十分となり、鋳物にひけ、鋳巣
等が生じ、品質を損ねると云う問題があつた。このため従来では鋳込まれるときの溶融金属の
温度を比較的高く保つ必要のある部分、例えば、
鋳造品の薄肉部、複雑形状部、コーナー部等を成
形する金型キヤビテイの表面に保温用塗型を厚め
に施し、これにより鋳込まれる溶融金属の温度降
下を防止し、鋳造品の薄肉部等における溶融金属
の流動性を良くする必要があつた。〔発明が解決しようとする問題点〕然しながら、前記保温用塗型を金型に施しても
キヤビテイ内での溶融金属の温度降下は避けられ
ず、このため鋳込み温度を高する必要がある。しかし、鋳込み温度を高くすれば、それだけ加
熱用エネルギの費用がかゝり、又、溶融金属の化
学成分によつては溶損を生じ不都合である。又、鋳造品の薄肉部等の品質を確保するために
保温用塗型を厚めに施すと寸法精度が落ち、かつ
鋳造品の鋳肌面が粗くなり、このため従来鋳放し
で充分な寸法精度が得られていた部分も機械加工
を施すことが必要となり、加工工数が増す上鋳肌
が部分的に失われるという不具合も生じる。更に、鋳造品の薄肉部の形状及び品質を確保す
るために鋳造時に多めの余肉を設け、その余肉部
分を機械加工して所定の寸法を得る方法もある
が、この場合も材料費及び加工工数が増加する要
因となる。又、鋳型の通気性を高めるため部分的に多孔質
材を用いる技術も提案されているが、従来のこの
種技術はガス抜のみを目的としていたので、鋳肌
を直接画成する部分をこの種の多孔質材料で形成
し、金型の温度降下を制御する技術は知られてい
ない。本発明は、叙上の問題点を解決するためになさ
れたものであり、本発明の目的とするところは、
金型鋳型の溶融金属の温度降下を避けたい部分に
通気性を有する多孔性材料を配置し、その断熱性
を利用して金型の温度降下を制御して、鋳造品を
高精度に形成することができる金属鋳造用金型を
提供することにある。〔問題点を解決するための手段〕一部を多孔性の材料で形成した金属鋳造用金型
に於いて、少なくとも薄肉部を鋳造すべき部分の表面の一
部が上記多孔質材料により形成されており、か
つ、上記多孔性の材料が、鉄系金属粉末をカサ密度
4.0〜6.5ｇ／cm³に焼結して成る多孔性焼結体であ
る上記の金属鋳造用金型とすることによつて達成
される。本発明を実施する場合には、鉄系金属粉末とし
て粒度100メツシユ以下、250メツシユ以上のステ
ンレス粉末を使用することが推奨される。〔作用〕上記多孔性の材料には多くの連続する気孔が存
在し、そのため断熱性に優れた被覆層が形成され
るので、叙上の如く構成することにより、このキ
ヤビテイ面に接する溶融金属は確実に保温される
ことになる。又、本発明の金属鋳造用金型を用いて鋳造する
場合、鋳型内のガスを積極的に外部へ逃がし、ガ
ス抜き後の鋳型内に充填された溶融金属の凝固を
促進させるため、減圧／空冷装置を用いることが
推奨される。上記減圧装置によれば、鋳型内に溶融金属を供
給する前に、上記多孔質材料の細孔を通して、鋳
型内のガスを外部に吸引してキヤビテイ内を減圧
し、溶融金属の鋳型内での充填性をより一層向上
させることができ、又、溶融金属の充填後、上記
空冷装置により、多孔性材料の細孔内に外部より
低温のエア等を流通させることにより、鋳型を冷
却し、鋳型内の溶融金属の凝固時間を短縮するこ
とができる。更には、本発明の如く、一部に多孔性材料を用
いた鋳型は、上記減圧／空冷装置の有無に拘わら
ず、前述の如く溶融金属の充填性が良くなるの
で、鋳型形状に対応した高精度の製品が得られ
る。又、塗型を用いないので鋳肌面の粗さが細か
くなり、従来機械加工を必要としていた部分が鋳
造品のまゝでも使用可能となる。〔実施例〕以下、図面により本発明の詳細を具体的に説明
する。第１図は、本発明にかゝる金属鋳造用金型の一
実施例を示す説明図、第２図は、従来の金属鋳造
用金型の一例を示す説明図である。尚、第１図及び第２図に示す金属鋳造用金型は
いずれもVTR用Al合金製下部シリンダを鋳造す
るためのものであるが、本発明は他の鋳造品、例
えば内燃機関用ピストンを鋳造するために用いる
ことや電動機用ロータの鋳造にも用いることがで
きるものである。又、第１図に示す実施例は、第２図に示す従来
の金属鋳造用金型の一部に通気性を有する多孔性
材料を配置したものであり、両図中、同一の構成
要素には同一の符号を付するものとする。而して、第１図中、１は本発明にかゝる金属鋳
造用金型、２は外型、３及び４は上記外型２に設
けた湯口及び湯道、６は上記外型２内部に嵌合し
てその下部に着脱自在に取り付けた中子型、７は
上記中子型６の中心軸に着脱自在に設けた中子型
入れ子、８は上記外型２内部に嵌合してその上部
に着脱自在に付けた上型、９は上記上型８の下部
に取り付けた多孔性材料、１０はキヤビテイ、１
１は上記上型８の中心軸に設けた保温材、１２は
押湯、１３は上記多孔性材料９と上記上型８との
境界部分に設けた吸引、冷却用ポートとなる空洞
部、１４は上記空洞部１３に通じるように設けた
給排気管である。尚、図では、省略したが、給排気管１４には空
洞部１３を通じてキヤビテイ１０内の吸引、冷却
を行うための減圧、冷却装置が設けられている。而して、第２図中、１′は従来の金属鋳造用金
型であり、２′は外型、５は上記外型２′に設けた
オーバーフロー部、８′は上記外型２′内部に嵌合
してその上部に着脱自在に取り付けた上型、１５
は突端面である。而して、この金属鋳造用金型１では、前記
VTR用Al合金製下部シリンダを鋳出し成形する
ために、上型８を多孔性材料９で構成する。本発明で用いる加工性材料９としては、粒度
100メツシユ以下250メツシユ以上の鉄系金属粉末
をカサ密度4.0〜6.5ｇ／cm³に焼結したものを使用
することが推奨される。このような粒度範囲のものを使用すると、容易
にカサ密度4.0〜6.5ｇ／cm³の焼結体が得られ、こ
れによると、極めて容易に本発明の目的を達成し
得るものである。多孔性材料９のカサ密度を4.0〜6.5ｇ／cm³（気
孔率・50〜18％）と範囲を限定した理由はカサ密
度がこの範囲より大きい（即ち、気孔率が小さ
い）と通気性が不十分となり、この範囲より小さ
い（即ち、気孔率が大きい）と鋳型としての強
度、耐久性が不十分となるためである。又、多孔
性材料９に接して形成される鋳造品の鋳肌部分を
機械加工することなく鋳出しのまゝ使用する場合
は多孔性材料９のカサ密度の大きいものを採用
し、平滑な鋳肌が得られるようにすることが望ま
しい。本実施例に用いる多孔性材料９は、粒度100〜
250メツシユのステンレス鋼（JIS記号：
SUS316L）粉末より成る焼結金属であり、その
カサ密度は5.0ｇ／cm³（気孔率：37％）である。本実施例で多孔性材料９のカサ密度を5.0ｇ／
cm³とやゝ小さく（気孔率を大きく）した理由は、
鋳造方法の関係からキヤビテイ１０内の上型の方
により多くガスが溜まるため、これをいち早く外
部へ逃がしキヤビテイ１０内への充填性を良くす
るためである。又、本実施例での前記VTR用Al合金製下部シ
リンダはその全高寸法の精度が厳しく要求される
ものであり、このため下部シリンダ突端面に機械
加工を必要とするが、上型８の前記突端面１５に
対応する部分には多孔性材料９を配置せず、押湯
部を廃止し全面を鋳出し成形することもできる。上記のような構成によれば、多孔性材料９中の
気孔内には断熱性に優れた空気が存在するので、
キヤビテイ内での鋳造品の薄肉部、複雑形状部及
びコーナー部等で溶融金属が充填時に保温されて
湯流れが良くなる。又、前述の如く、外部からの
吸引又は減圧手段により多孔性材料９中の連続す
る気孔を通してキヤビテイ１０内を減圧し、キヤ
ビテイ１０内のガスを外部に放出するので、キヤ
ビテイ１０内への溶融金属の充填性がより一層良
くなると共に、安定した高精度の鋳造品を得る。
これによつて所望形状の滑らかな鋳肌面を有する
製品が形成され、従来機械加工を必要としていた
鋳造品も鋳放しのまゝで製品とするとが可能とな
る。又、前述の如く、キヤビテイ１０内へ溶融金属
を充填した後の凝固時間を短縮するために多孔性
材料９の細孔を通して外部よりエアを供給してキ
ヤビテイ１０を冷却することもできる。一方、第２図に示す従来の金属鋳造用金型１′
では湯道部４の周辺の外径３に溶融金属の保温の
ための断熱性塗型材が施され、又、湯道部４側と
は反対側の外径３の薄肉部では溶融金属の温度が
低下し、湯止まりが発生するのを防止するため、
この部分にはオーバーフロー部５が形成されてい
る。又、溶融金属の凝固による収縮巣をなくすた
めに比較的大きな押湯部１２が設けられている。次に本発明の金属鋳造用金型１と従来の金属鋳
造用金型１′で鋳造したときのそれぞれの条件及
び効果を対比して表に示す。 [Industrial Application Field] The present invention relates to improvements in metal casting molds for precisely forming various cast products by casting molten metal. [Prior Art] When mass producing precision cast products by pouring molten metal into a cavity in a mold, metal casting molds are generally widely used as the molds. This type of metal casting produces precision castings, but
Since the mold has a large cooling force on the molten metal being cast, gas is generated due to sudden changes in the temperature of the molten metal.
Due to the pressure of the generated gas and the drop in the temperature of the hot water, filling of the molten metal becomes insufficient, causing sink marks and cavities in the casting, which impairs quality. For this reason, in the past, parts where it was necessary to keep the temperature of molten metal relatively high during casting, for example,
A thick heat-retaining coating is applied to the surface of the mold cavity that molds thin-walled parts, complex-shaped parts, corner parts, etc. of cast products, and this prevents the temperature of the molten metal being cast from dropping. There was a need to improve the fluidity of molten metal. [Problems to be Solved by the Invention] However, even if the heat-retaining coating is applied to the mold, a drop in the temperature of the molten metal within the cavity cannot be avoided, and therefore it is necessary to increase the casting temperature. However, if the casting temperature is increased, the cost of heating energy increases accordingly, and depending on the chemical composition of the molten metal, melting loss may occur, which is inconvenient. In addition, if a thicker heat-insulating coating is applied to ensure the quality of the thin-walled parts of the casting, dimensional accuracy will drop and the cast surface of the casting will become rough. It is now necessary to perform machining on the parts where the cast surface was previously obtained, resulting in the problem that the cast surface is partially lost, which increases the number of machining steps. Furthermore, in order to ensure the shape and quality of the thin-walled parts of the cast product, there is a method of adding a large amount of extra wall thickness during casting, and then machining that extra wall part to obtain the specified dimensions, but this also reduces material costs and costs. This causes an increase in processing man-hours. In addition, a technique has been proposed in which a porous material is partially used to increase the air permeability of the mold, but since this type of technology has been used only for the purpose of degassing, this technique is used to directly define the casting surface. There is no known technique for controlling the temperature drop in the mold by forming it with a porous material. The present invention has been made to solve the above-mentioned problems, and the purpose of the present invention is to:
A porous material with air permeability is placed in the part of the mold where the temperature drop of the molten metal is to be avoided, and its insulating properties are used to control the temperature drop in the mold to form cast products with high precision. The object of the present invention is to provide a metal casting mold that can be used for metal casting. [Means for solving the problem] In a metal casting mold partially formed of a porous material, at least a part of the surface of the portion where the thin wall portion is to be cast is formed of the porous material. The porous material has a bulk density of ferrous metal powder.
This is achieved by using the metal casting mold described above, which is a porous sintered body sintered to a density of 4.0 to 6.5 g/cm ³ . When carrying out the present invention, it is recommended to use stainless steel powder with a particle size of 100 mesh or less and 250 mesh or more as the iron-based metal powder. [Function] The porous material described above has many continuous pores, and therefore a coating layer with excellent heat insulation is formed. It will definitely keep you warm. In addition, when casting using the metal casting mold of the present invention, in order to actively release the gas in the mold to the outside and promote solidification of the molten metal filled in the mold after degassing, depressurization / It is recommended to use air cooling equipment. According to the pressure reducing device, before supplying molten metal into the mold, the gas inside the mold is sucked outside through the pores of the porous material to reduce the pressure inside the cavity, and the molten metal is pumped inside the mold. The filling performance can be further improved, and after filling with molten metal, the above-mentioned air cooling device cools the mold by circulating air at a lower temperature than the outside through the pores of the porous material. The solidification time of molten metal within can be shortened. Furthermore, as in the present invention, a mold partially made of a porous material can be filled with molten metal better as described above, regardless of the presence or absence of the above-mentioned decompression/air cooling device. Accurate products are obtained. Furthermore, since no coating mold is used, the roughness of the casting surface becomes finer, and parts that conventionally required machining can now be used as cast products. [Example] The details of the present invention will be specifically explained below with reference to the drawings. FIG. 1 is an explanatory diagram showing an embodiment of a metal casting mold according to the present invention, and FIG. 2 is an explanatory diagram showing an example of a conventional metal casting mold. The metal casting molds shown in FIGS. 1 and 2 are both for casting Al alloy lower cylinders for VTRs, but the present invention is also applicable to other casting products, such as pistons for internal combustion engines. It can be used for casting and also for casting rotors for electric motors. Furthermore, the embodiment shown in Fig. 1 is an example in which a porous material having air permeability is placed in a part of the conventional metal casting mold shown in Fig. 2, and in both figures, the same component is shall be given the same symbol. In FIG. 1, 1 is a metal casting mold according to the present invention, 2 is an outer mold, 3 and 4 are sprues and runners provided in the outer mold 2, and 6 is the outer mold 2. A core mold 7 is fitted inside and removably attached to the lower part of the core mold, 7 is a core mold nest removably provided on the central axis of the core mold 6, and 8 is a core mold insert that is fitted inside the outer mold 2. 9 is a porous material attached to the lower part of the upper mold 8; 10 is a cavity;
1 is a heat insulating material provided on the central axis of the upper mold 8; 12 is a feeder; 13 is a cavity provided at the boundary between the porous material 9 and the upper mold 8, serving as a suction and cooling port; 14; is an air supply/exhaust pipe provided to communicate with the cavity 13. Although not shown in the figure, the supply/exhaust pipe 14 is provided with a depressurization and cooling device for suctioning and cooling the inside of the cavity 10 through the cavity 13. In Fig. 2, 1' is a conventional metal casting mold, 2' is an outer mold, 5 is an overflow part provided in the outer mold 2', and 8' is the inside of the outer mold 2'. an upper mold that fits into the mold and is removably attached to the upper part of the mold, 15
is the tip surface. Therefore, in this metal casting mold 1, the above-mentioned
In order to cast and mold an Al alloy lower cylinder for a VTR, an upper mold 8 is made of a porous material 9. The processable material 9 used in the present invention has a particle size of
It is recommended to use iron-based metal powder of 100 meshes or less and 250 meshes or more sintered to a bulk density of 4.0 to 6.5 g/cm ³ . When particles having a particle size in this range are used, a sintered body having a bulk density of 4.0 to 6.5 g/cm ³ can be easily obtained, and the object of the present invention can thereby be achieved very easily. The reason why the bulk density of the porous material 9 is limited to 4.0 to 6.5 g/cm ³ (porosity: 50 to 18%) is that if the bulk density is larger than this range (i.e., the porosity is small), the air permeability will decrease. This is because if the porosity is smaller than this range (that is, the porosity is large), the strength and durability of the mold will be insufficient. In addition, when using the cast surface part of the cast product that is formed in contact with the porous material 9 as cast without machining, use a porous material 9 with a large bulk density to create a smooth casting surface. It is desirable that the skin be obtained. The porous material 9 used in this example has a particle size of 100 to
250 mesh stainless steel (JIS symbol:
It is a sintered metal made of SUS316L) powder, and its bulk density is 5.0 g/cm ³ (porosity: 37%). In this example, the bulk density of the porous material 9 was set to 5.0 g/
The reason for making it a little smaller (increasing the porosity) at cm ³ is as follows.
Due to the casting method, more gas accumulates in the upper die in the cavity 10, so this is to quickly release the gas to the outside and improve the ability to fill the cavity 10. In addition, the lower cylinder made of Al alloy for VTR in this embodiment is required to have strict precision in its overall height dimension, and therefore requires machining on the tip end surface of the lower cylinder. The porous material 9 may not be disposed in the portion corresponding to the protruding end surface 15, and the feeder portion may be omitted and the entire surface may be cast and molded. According to the above configuration, air with excellent heat insulation properties exists in the pores of the porous material 9.
The molten metal is kept warm during filling in the thin-walled parts, complex-shaped parts, corner parts, etc. of the cast product in the cavity, improving the flow of the molten metal. Further, as described above, the pressure inside the cavity 10 is reduced through the continuous pores in the porous material 9 by external suction or pressure reduction means, and the gas inside the cavity 10 is released to the outside, so that the molten metal inside the cavity 10 is reduced. In addition to improving the filling properties of the product, a stable and highly accurate cast product can be obtained.
As a result, a product having a smooth cast surface of a desired shape is formed, and a cast product that conventionally required machining can be made into a product in an as-cast state. Further, as described above, in order to shorten the solidification time after the molten metal is filled into the cavity 10, the cavity 10 can be cooled by supplying air from the outside through the pores of the porous material 9. On the other hand, a conventional metal casting mold 1' shown in FIG.
In this case, a heat insulating coating material is applied to the outside diameter 3 around the runner 4 to keep the molten metal warm, and the thin part of the outside diameter 3 on the opposite side from the runner 4 is coated with the temperature of the molten metal. In order to prevent the water from decreasing and causing hot water to stop,
An overflow portion 5 is formed in this portion. Further, a relatively large feeder portion 12 is provided to eliminate shrinkage cavities due to solidification of molten metal. Next, the conditions and effects of casting with the metal casting mold 1 of the present invention and the conventional metal casting mold 1' are compared and shown in a table.

〔Effect of the invention〕

本発明は叙上の如く構成されるので、本発明に
よるときには、鋳造品を高精度、かつ安価、大量
に製造できる金属鋳造用金型を提供し得るもので
ある。而して、本発明の金属鋳造用金型によれば、従
来の金属鋳造用金型１′と比較して溶融金属の鋳
込み温度を低下させて経済的にすることができ、
かつ鋳造品の薄肉部の形状が不完全であつたり、
押湯効果の不完全による鋳巣が生じたりする等の
不良発生率を低下させることができる。又、薄肉部の余肉及び押湯量を減少させること
ができる。更には従来の金型１′の構成のうちオ
ーバーフロー部及び断熱性塗型が不要となる。更
に又、鋳込み温度と鋳込み溶融金属量の減少によ
り鋳造サイクルを短縮することができる。尚、本発明は叙上の実施例に限定されるもので
はなく、他の用途としては薄肉、複雑形状を有す
る金属鋳造品に広く用いることができ、例えば内
燃機関用ピストンを鋳造するのに適しており、特
にそのバルブリセス部を有するピストン頂面やピ
ン孔外周の逃げ部を鋳出し形成する部分に好適で
あり、又、電動機用ロータの鋳造用金型にも適用
でき、特にロータ内の複数のキヤビテイからのガ
ス抜き促進させる部分等の少なくとも一部に適用
することができ、更に又、本発明の目的の範囲内
において前述の説明から当業者が容易に想到し得
る全ての変更実施例を包摂するものである。 Since the present invention is configured as described above, it is possible to provide a metal casting mold that can produce cast products in large quantities with high precision and at low cost. According to the metal casting mold of the present invention, the casting temperature of molten metal can be lowered and made more economical compared to the conventional metal casting mold 1'.
Also, the shape of the thin wall part of the cast product is incomplete,
It is possible to reduce the incidence of defects such as formation of blowholes due to incomplete feeder effect. Moreover, the excess thickness of the thin-walled portion and the amount of feeder can be reduced. Furthermore, the overflow part and the heat insulating coating mold of the conventional mold 1' configuration are no longer necessary. Furthermore, the casting cycle can be shortened by reducing the casting temperature and the amount of molten metal poured. It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be widely used in other applications such as metal castings having thin walls and complex shapes.For example, it is suitable for casting pistons for internal combustion engines. It is particularly suitable for the top surface of a piston with a valve recess and the part where a relief part on the outer periphery of a pin hole is formed by casting.It can also be applied to a mold for casting a rotor for an electric motor, and is particularly suitable for forming a relief part on the top surface of a piston having a valve recess. The present invention can be applied to at least a part of the part that promotes degassing from the cavity of the present invention, and furthermore, all modifications that can be easily figured out by a person skilled in the art from the foregoing description within the scope of the present invention. It is inclusive.

[Brief explanation of the drawing]

第１図は、本発明にかゝる金属鋳造用金型の一
実施例を示す説明図、第２図は、従来の金属鋳造
用金型の一例を示す説明図である。１……金属鋳造用金型、２……外型、３……湯
口、４……湯道、６……中子型、７……中子型入
れ子、８……上型、９……多孔性材料、１０……
キヤビテイ、１１……保温材、１２……押湯、１
３……空洞部、１４……給排気管。 FIG. 1 is an explanatory diagram showing an embodiment of a metal casting mold according to the present invention, and FIG. 2 is an explanatory diagram showing an example of a conventional metal casting mold. 1... Metal casting mold, 2... Outer mold, 3... Sprue, 4... Runway, 6... Core mold, 7... Core mold insert, 8... Upper mold, 9... Porous material, 10...
Cavity, 11...Heat insulation material, 12...Riser, 1
3...Cavity part, 14...Intake and exhaust pipe.

Claims

[Scope of Claims] 1. In a metal casting mold partially formed of a porous material, the surface of the portion where the thin wall portion is to be cast is formed of the porous material, and The bulk density of iron-based metal powder is
The metal casting mold described above is a porous sintered body sintered to a density of 4.0 to 6.5 g/cm ³ . 2. The metal casting mold according to claim 1, wherein the iron-based metal powder is stainless steel powder. 3. The metal casting mold according to claim 2, wherein the stainless steel powder has a particle size of 100 mesh or less and 250 mesh or more.