EP0233478A1 - Giessform, Verfahren zur ihrer Herstellung und Giessverfahren - Google Patents

Giessform, Verfahren zur ihrer Herstellung und Giessverfahren Download PDF

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Publication number
EP0233478A1
EP0233478A1 EP19870100559 EP87100559A EP0233478A1 EP 0233478 A1 EP0233478 A1 EP 0233478A1 EP 19870100559 EP19870100559 EP 19870100559 EP 87100559 A EP87100559 A EP 87100559A EP 0233478 A1 EP0233478 A1 EP 0233478A1
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EP
European Patent Office
Prior art keywords
mold
cao
calcia
casting
metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP19870100559
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English (en)
French (fr)
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EP0233478B1 (de
Inventor
Seiju Uchida
Akio Hashimoto
Gen Okuyama
Toru Degawa
Takashi Sato
Kozo Fujiwara
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsui Engineering and Shipbuilding Co Ltd
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Mitsui Engineering and Shipbuilding Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Priority claimed from JP766286A external-priority patent/JPH0628775B2/ja
Priority claimed from JP766486A external-priority patent/JPH0628776B2/ja
Priority claimed from JP766186A external-priority patent/JPH0628774B2/ja
Priority claimed from JP765886A external-priority patent/JPS62168659A/ja
Priority claimed from JP765986A external-priority patent/JPS62168628A/ja
Priority claimed from JP766386A external-priority patent/JPS62168630A/ja
Priority claimed from JP766086A external-priority patent/JPS62168632A/ja
Priority claimed from JP1091686A external-priority patent/JPH0635029B2/ja
Application filed by Mitsui Engineering and Shipbuilding Co Ltd filed Critical Mitsui Engineering and Shipbuilding Co Ltd
Publication of EP0233478A1 publication Critical patent/EP0233478A1/de
Application granted granted Critical
Publication of EP0233478B1 publication Critical patent/EP0233478B1/de
Expired legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • 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
    • B22C9/061—Materials which make up the mould

Definitions

  • the present invention relates to a mold containing calcia (CaO) as the main constituent, a method of producing such a mold and a casting method using such a mold.
  • a mold according to the present invention is capable of casting even an active metal and a high-melting point metal.
  • Japanese Patent Publication No. 849/1979 discloses a method of deoxidizing and desulfurizing a molten steel by adding aluminum to the molten steel which is accommodated in a container lined with a basic refractory material containing much CaO under vacuum or an argon atmosphere.
  • a mold used for casting an active metal (including alloy) such as titanium and zirconium rammed mold, investment mold, water-cooled copper mold, sand mold (using zirconium sand, olivine sand etc.) etc. are conventionally known.
  • a rammed mold is made by molding a material of graphite powder with a carbon or resin binder, drying and baking the molded body.
  • tungsten powder coated mold which is made of a slurry of tungsten and a metal binder
  • oxide mold which is made of a combination of a slurry of an oxide and an oxide binder
  • graphite mold which is made of a graphite slurry and a binder containing carbon
  • a first mold of the present invention is a porous calcia mold containing not less than 40 wt% CaO.
  • a second mold of the present invention is a calcia mold containing not less than 40 wt% CaO and 0.1 to 8 wt% halide.
  • a third mold of the present invention is a calcia graphite mold containing 95 to 10 wt% CaO and 5 to 50 wt% graphite.
  • a fourth mold of the present invention is a calcia mold containing not less than 40 wt% CaO, not more than 5 wt% low-eutectic temperature oxide, and nor more than 40 wt% high-eutectic temperature oxide.
  • a fifth mold of the present invention is provided with a layer of a calcia refractory material containing 40 wt% CaO on the surface of the mold which comes into contact with a molten metal.
  • a method of producing a mold according to the present invention comprises the steps of pouring a slurry of a non-aqueous solution of calcia powder or particles containing not less than 40 wt% CaO into a liquid-absorbing master mold to make a deposit on the surface of the master mold, removing the master mold, drying the deposit, and baking the deposit at a baking temperature for a baking time which are so determined that a sintered body to be obtained will be porous.
  • Another method of producing a porous calcia mold according to the present invention comprises the steps of kneading calcia particles with an organic binder, injection molding the kneaded material, removing the binder, and baking the molded body at a baking temperature for a baking time which are so determined that a sintered body to be obtained will be porous.
  • Still another method of producing a calcia mold according to the present invention comprises the steps of baking a molded body of a calcia particulate molding material while bringing a member for preventing the deformation of a molded body into contact at least with a part of the molded body.
  • one of the above-described molds is used to cast a highly active and/or high-melting point metal (including an alloy).
  • a casting method comprises the steps of placing a bottomless calcia mold on a metal chill plate, pouring a molten metal by top-pouring, and gradually solidifying the molten metal from the lower part while insulating the riser of the mold.
  • a first mold according to the present invention is a calcia mold containing not less than 40 wt% CaO.
  • Calcia has a high melting points, as described above, and thermodynamically stable even at a high temperature. Since the stability and the heat resistance of the molds increase with the increase in CaO content, the molds contain at least 40 wt% (herinunder % means wt% unless otherwise specified), preferably at least 50 %, and more preferably at least 60 % CaO.
  • the material of the first mold is calcia, which has a high melting point and is thermodynamically stable even at a high temperature, it is easy to cast a high-melting point and/or highly active metal and it is possible to obtain a casting free from contamination on the surface thereof. Furthermore, since the mold is porous, it is efficient in resistance to thermal shock, and has high heat retaining properties and good durability. In addition, it is possible to reuse the calcia material many times, and since the position of the shrinkage cavity is high, the yield is enhanced.
  • the first mold Since the first mold is cheap, and reusable due to the high resistance to thermal shock, it greatly reduces casting costs.
  • the first to fifth molds of the present invention are adaptable to an inner mold called a core as well as an outer mold. Since CaO has slaking properties, it is possible to remove these molds by hydrating them by utilizing the slaking properties.
  • the materials which the molds can contain as well as CaO are exemplified by an oxide, a carbide, a nitride, carbon and a halide.
  • an oxide an oxide having a high melting point such as magnesia (MgO) and zirconia (ZrO2) is preferable.
  • MgO magnesia
  • ZrO2 zirconia
  • a carbide and a nitride silicon carbide, silicon nitride, and aluminum nitride will be cited.
  • halide an alkaline metal, an alkaline earth metal, a fluoride and a chloride of lead, and a double salt containing these elements will be mentioned.
  • they are, for example, CaF2, MgF2, BaF2, SrF2, NaF, LiF, KF, PbF2, CsF, Na3AlF6, CaCl2, MgCl2, NaCl, and KCl.
  • the molds can contain carbon (C) as a material except CaO.
  • C carbon
  • Graphite is preferable as a carbon material. Both natural graphite and artificial graphite are usable. Since graphite is scaly, the molding properties are poor, and since it is inherently poor in reactivity, it is difficult to form graphite into a ceramic bond and the strength of the sintered body is therefore apt to be lowered. Therefore, when graphite is used as a material for a calcia mold, it is effective to add a small amount of metallic aluminum.
  • calcium hydroxide as well as limestone, calcinated limestone, namely, quick lime, and electrofused calcia which is melted in an arc furnace is usable as a material.
  • a mineral containing CaO such as larnite, merwinite, anorthosite and dolomite is also usable.
  • At least one selected from the group consisting of the above-described oxide, carbide, nitride, carbon and halide is added to such a calcia material, as desired, and a slurry is made by mixing them into a non-aqueous solution.
  • a slurry is made, if the particle diameter of the particulate molding material is too small, it is often the case that the shrinkage at a later step of baking becomes excessively large or the sintered body becomes pressure tight. Therefore, it is preferable to classify the particulate molding material so that the fine particles having a particle diameter of not more than 0.1 mm is at least 40 % and at most 50 %.
  • the particle diameter of the particles is too large, the surface of the mold becomes rough, so that the largest particle diameter is at most 1 mm, preferably at most 0.5 mm.
  • a liquid used for preparing the slurry is a non-aqueous solution, namely, a liquid containing no water, because calcia has slaking properties.
  • a solution having an appropriate viscosity As a non-aqueous solution, a solution having an appropriate viscosity is used.
  • alcohol monovalent or polyvalent alcohol
  • toluene with oleic acid dissolved therein alcohol with oleic acid dissolved therein
  • oil with oleic acid dissolved therein oil with oleic acid dissolved therein
  • carbon tetrachloride with beeswax dissolved therein and isobutyl acetate are preferable, but the present invention is not limited thereto and any non-aqueous liquid which does not slake calcia is usable.
  • a non-aqueous solution it is preferable to adjust the viscosity of such a non-aqueous solution so that when in is made into a slurry, it has an appropriate viscosity to be poured into a master mold at ordinary temperature.
  • Other additives used in a slip casting method such as deflocculant, antifoamer, germicide, and cheleating agent for inactivating unnecessary ions may be added to the slurry.
  • a slurry is poured into a liquid-absorbing master mold.
  • a master mold a mold having properties of absorbing the above-described non-aqueous solution is used, and a gypsum mold is most preferable.
  • the configuration of the master mold is not specified so long as it has a configuration of a female mold of a mold to be obtained.
  • the non-aqueous solution of the slurry is absorbed by the master mold, and the solid content of the slurry adheres to the inner surface of the master mold, in other words, what is called deposition progresses.
  • the slurry in the master mold is discharged, if necessary, and thereafter the liquid of the deposit on the inner surface of the master mold is left to be further absorbed by the master mold. This step of liquid absorption reduces the liquid of the deposit, and therefore facilitates the release of the deposit.
  • the mother mold is removed.
  • the molded body obtained is dried.
  • the molded body is preferably dried gradually at a temperature lower than the boiling point of the non-aqueous solution. In the latter period of the step of drying, the molded body may be dried at a temperature higher than the boiling point.
  • the dried molded body is next baked.
  • the molded body is first calcinated at a temperature at which the organic material which has been dissolved in the non-aqueous solution is oxidized away, and thereafter the molded body is baked to be sintered.
  • the temperature and the time for baking are selected so that the sintered body to be obtained will be porous.
  • These baking conditions are different depending upon the components in the mold other than CaO. For example, if a comparatively large amount of halide or oxide which constitutes a compound having a low melting point together with CaO is contained, the baking temperature is low and the baking time is short.
  • the baking temperature is high, the baking time is short, while a low baking temperature requires a long baking time.
  • the molded body contains 40 to 80 % CaO, it is ordinarily baked at about 850 to 1,350°C for about 1 to 10 hours. If the CaO content exceeds 80 %, the molded body is preferably baked at a comparatively high temperature of 1,200 to 1,700°C for about 1 to 5 hours.
  • the sintered body obtained is ground, if necessary, to finish a mold.
  • the mold of the present invention is porous.
  • the porosity is preferably 10 to 40 vol%, more preferably 15 to 30 vol%. If the porosity is less than 10 vol%, the resistance to thermal shock and the insulating effect of the mold are lowered.
  • Another method of producing the porous calcia mold is as follows.
  • At least one selected from the group consisting of the above-described oxide, carbide, nitride, carbon and halide is added to the above-described calcia material, as desired, to make a particulate molding material. If the particle diameter of the particulate molding material is too small, it is often the case that the shrinkage at a later step of baking becomes excessively large or the sintered body becomes pressure tight. Therefore, it is preferable to classify the particulate molding material so that the fine particles having a particle diameter of not more than 0.1 mm is at most 20 %, preferably at most 10 %. On the other hand, if the particle diameter of the particles is too large, injection is difficult and the surface of the mold becomes rough, so that the largest particle diameter is at most 1 mm, preferably at most 0.5 mm, and more preferably at most 0.3 mm.
  • An organic binder is added to the particulate molding material and they are kneaded.
  • the kneaded material is injection molded.
  • a non-aqueous binder which does not slake calcia is used.
  • a thermoplastic resin such as polystyrene, polyethylene, cellulose acetate, polyvinyl alcohol, acryl and polypropylene
  • a thermosetting resin such as novolak is usable.
  • a plasticizer, a lubricant and an auxiliary may be used together with the organic agent.
  • plasticizer diethyl phthalate, paraffin, dibutyl phthalate, wax, dioctyl phthalate, fatty ester, etc. are preferable.
  • lubricant zinc stearate, aluminum stearate, magnesium stearate, diglycol stearate, bread crumb, mineral oil, etc. are preferable.
  • atactic polypropylene a group of a plurality of resins having different decomposition temperatures, a sablimating material such as naphthalene, natural vegetable oil such as peanut oil and soybean oil, natural animal oil, etc. are preferable.
  • the amount of organic binder to be added is preferably about 0.1 to 20 wt% with respect to 100 wt% of particulate molding material.
  • a plasticizer, a lubricant and an auxiliary are preferably added at most 10 wt% in total amount.
  • the material After the addition of an organic binder etc., the material is heated to, for example, about 80 to 150°C, if necessary, stirred and kneaded, and thereafter it is cooled to be solidified.
  • the solidified material is then crushed and dressed into particles of a diameter of not more than 0.5 mm, preferably not more than 0.3 mm. In place of crushing, the material may be granulated by extrusion or the like.
  • the thus-obtained injection molding material is supplied to an injection molding machine, injected into the die to obtain a molded body.
  • an injection molding machine various kinds of molding machines such as a screw in-line type injection molding machine and a plunger injection molding machine are usable.
  • the injection molding material is heated in a heating cylinder, kneaded to be plasticized, and injected into a die by the advancement of a screw or a plunger.
  • the die has a configuration of a female mold of a mold to be obtained.
  • the obtained molded body is cut or ground, as occasion demands, to finish it into a predetermined configuration, and the binder is removed.
  • the temperature is gradually raised to about 350 to 500°C in the air atmosphere, and the resin content is removed by decomposition, sublimation or oxidation.
  • the molded body is baked to obtain a sintered body.
  • the baking conditions are the same as those described above.
  • the molded body contains 40 to 80 % CaO, it is ordinarily baked at about 850 to 1,350°C for about 1 to 10 hours. If the CaO content exceeds 80 %, the molded body is preferably baked at a comparatively high temperature of 1,000 to 1,500°C for about 1 to 5 hours.
  • the sintered body obtained is ground, if necessary, to finish a mold.
  • a member for preventing the deformation of a molded body may be brought into contact with at least a part of the molded body while it is being baked. This member greatly lessens the deformation of the body to be sintered in the step of baking, and enhances the dimensional accuracy of the mold. Since the member for preventing the deformation of a molded body is reusable many times, it is possible to produce a multiplicity of molds of the same inner dimension with accuracy.
  • the member for preventing the deformation of a molded body is made of a material which does not react with the calcia particulate molding material during baking the molded body.
  • a ceramic material such as alumina is preferable.
  • the member for preventing the deformation of a molded body has an outer surface having the configuration in conformity with that of the inner surface of a mold to be obtained.
  • This member may have a configuration which makes the member in close contact with either the entire part of the inner surface of the mold, or only a part thereof.
  • the member for preventing the deformation of a molded body may also consist of a combination of a plurality of parts. If the configuration of the inner surface of the mold is a rectangular parallelopiped, a plate-like or box-shaped member for preventing the deformation of a molded body is used. If the configuration of the inner surface of the mold is a column, a columnar or cylindrical member is used.
  • the member for preventing deformation may be charged into the master mold before molding the particulate molding material, or may be charged into the cavity of the molded body after the particulate molding material has been molded.
  • the member for preventing the deformation of a molded body maintains the state in which it is in close contact with at least a part of the molded body during the step of baking.
  • the close contact of the member securely prevents the deformation of the molded body during the step of baking.
  • the method of molding is not limited to the above-described methods, and the methods of die casting, slip casting, rubber press, injection molding, hot press, stamping and so forth are usable.
  • the sintering method adopting the member for preventing deformation is adaptable to a method of sintering molds other than the above-described porous mold. It is possible to provide a pressure tight calcia mold by the sintering method adopting the above-described step of preventing deformation. If the step of baking is carried out at a higher temperature than the above-described baking temperature and/or for a longer timer than the above-described baking time, the molded body will be sintered adequately and produce a sintered body having high density. If a particulate molding material has a wide range of particle size, the sintered body will also become pressure tight.
  • a member 2 for preventing the deformation of a molded body had been charged into a master mold, and the calcia particulate molding material was charged into the space between the inner surface of the master mold and the outer peripheral surface of the member 2 for preventing the deformation of a molded body in such a manner as to be rammed.
  • the calcia particulate molding material used was reagent CaO particles having a CaO purity of 98 %.
  • the dimensions of the mold at the time of molding was 5 cm in length, 15 cm in width, 13 cm in height and 12 cm in depth.
  • the member for preventing the deformation of a molded body is an alumina plate 0.5 cm in length, 10 cm in width and 15 cm in height.
  • a second mold of the present invention is composed of a calcia refractory material which contains not less than 40 wt% CaO and 0.1 to 8 wt% halide.
  • the second mold which is a calcia mold, is also capable of casting a high-melting point metal, a highly active metal and an alloy containing such a metal with high purity. Since the second mold contains a halide, the surface of the mold is smooth, which produces a casting having a smooth casting surface.
  • the halide in the mold facilitates the baking and enables a molded body of a mold of a predetermined dimension to be provided even under a low pressure.
  • Halides suitable for the mold have been exemplified above.
  • the halides have a low melting point and many of them have much higher resistance to slaking than CaO. Therefore, the existence of a halide itself improves the resistance to hydration and accelerates the sintering of the material during the step of baking, thereby enhancing the density of the structure of the sintered body. These effects provide in cooperation the mold with high resistance to hydration.
  • the action of accelerating sintering also greatly increases the strength of the mold to be obtained.
  • the halide often exists in grain boundaries, and a layer containing much halide surrounds a CaO particle. It is considered that this fact also improves the resistance to hydration of the mold. Since addition of too much halide reduces the refractoriness of the mold, the content is not more than 8 %, preferably not more than 5 %. Needless to say, since addition of too small amount of halide does not bring about the above-described effects and actions, the content is not less than 0.1 %, preferably not less than 0.3 %. Since the stability and the heat resistance of the mold increases with the increase in CaO content, the mold of the present invention contains at least 40 wt%, preferably at least 70 wt%, and more preferably at least 80 wt% CaO.
  • the mold may contain an oxide, a carbide, a nitride, carbon as well as CaO. These compounds suitable for the mold have already been exemplified.
  • the mold may either be porous or pressure tight.
  • At least one selected from the group consisting of the above-described oxide, carbide, nitride and carbon is added to the above-described calcia material and halide, as desired, to make the main raw material.
  • the main raw material with an appropriate binder added thereto, if necessary, is molded and baked to make a mold.
  • a non-aqueous binder is used. It may be either a liquid or a solid binder.
  • a liquid binder alcohol, toluene, alcohol (monovalent or polyvalent alcohol) with anhydrous calcium chloride, mastic gum, acacia gum or the like dispersed therein, toluene with oleic acid dissolved therein, alcohol with oleic acid dissolved therein, oil with oleic acid dissolved therein, carbon tetrachloride with beeswax dissolved therein, and isobutyl acetate are preferable, but any non-aqueous liquid which does not slake calcia such as, for example, various mineral oils such as asphalt, tar and pitch and the residue thereof, animal oil and vegetable oil is usable.
  • the amount of binder to be used is preferably 1 to 5 wt% of a particulate molding material.
  • thermoplastic resin such as polyethylene, polypropylene, cellulose acetate, acrylic resin and polyvinyl alcohol, a thermosetting resin such as novolak and paraffin are preferable, but other materials which provide molding properties for the raw material are also usable.
  • the material may be hot pressed with no or a small amount of binder.
  • the molded or the stamped mold is dried, if necessary, and after it is calcinated at a temperature, preferably lower than the baking temperature, it is baked to be sintered.
  • the baking temperature is not lower than 800°C, preferably 1,200 to 1,800°C.
  • the step of baking is carried out in the air atmosphere, but another atmosphere is possible.
  • the material for the mold is cheap and is capable of being collected after casting and molded for reuse, so that it is possible to greatly reduce casting costs.
  • the second mold facilitates the casting of a high-melting point and/or highly active metal.
  • a mold containing a large amount of, for example, not less than 80 wt% CaO is suitable for casting a high-melting pure metal such as chromium and vanadium and an alloy containing a large amount of such metal.
  • a mold containing a large amount of CaO is also suitable for casting a highly active pure metal such as titanium and zirconium and an alloy containing a large amount of such metal.
  • a third mold is composed of a calcia graphite refractory material containing 95 to 10 wt% CaO and 5 to 50 wt% graphite. Since the main material of the mold is CaO and graphite having high heat resistance, it facilitates the casting of a high-melting point and/or highly active metal and is capable of producing a casting free from contamination on the surface. Since the third mold contains a comparatively large amount of graphite, the inner surface of the mold is smooth and is therefore capable of producing a casting having a smooth surface. In addition, since the mixing ratio of CaO and graphite is appropriate, the heat retaining properties and the fluidity are better than those of a graphite mold.
  • the heat resistance of the mold is improved by adding not less than 5 % graphite to the material, thereby facilitating the casting of a high-melting point metal. If the graphite content exceeds 50 %, carbon is likely to mix into the molten metal and contaminate it, so that the content of graphite is not more than 50 %.
  • the content of graphite is preferably 10 to 40 %, more preferably 15 to 30 %. Any of natural graphite and artificial graphite such as crushed electrode graphite, pyrolytic graphite and kish graphite is usable in the present invention.
  • graphite Since graphite is scaly, it has poor molding properties, and since it is inherently poor in reactivity, it is difficult to form graphite into a ceramic bond and the strength of the sintered body is therefore apt to be lowered. Therefore, when graphite is used as a material for a calcia mold, it is effective to add a small amount of metallic aluminum. When aluminum is baked in a non-oxidizing atmosphere, a highly corrosion-resistant reaction product such as aluminum carbide and aluminum nitride is produced, which enhances the corrosion resistance of the mold and the bonding strength between graphite and the surrounding structure, thereby improving the strength of the mold.
  • the third mold may contain various kinds of halides described above as well as CaO and graphite. Since addition of too much halide lowers the refractoriness, the content is not more than 5 %, preferably not more than 3 %.
  • the third mold may also contain an oxide, a carbide and a nitride. These compounds have been exemplified above. Since the stability and the heat resistance of the third mold in an oxidizing atmosphere increases with the increase in CaO content, the third mold contains at least 10 wt%, preferably at least 30 wt %, and more preferably at least 50 wt% CaO.
  • a fourth mold is composed of a calcia refractory material containing not less than 40 wt% CaO, not more than 5 wt% low-eutectic temperature oxide and not more than 40 wt% high-eutectic temperature oxide. Since the mold contains an appropriate amount of metal oxide, sintering is easy and has high strength and resistance to slaking.
  • the low-eutectic temperature oxide is at least one selected from the group consisting of metal and semi-metal oxides which have a eutectic temperature below 1,450°C
  • the high-eutectic temperature oxide is at least one selected from the group consisting of metal oxides which have a eutectic temperature of not lower than 1,450°C.
  • the content of a low-eutectic temperature oxide is not more than 5 %, preferably not more than 3 %, and more preferably not more than 2 %.
  • the content of P2O5, B2O3 and FeO which greatly lower the heat resistance of the mold, is preferably not more than 1 %.
  • the fourth mold contains not more than 40 % high-eutectic temperature oxide.
  • the content of a high-eutectic oxide is preferably as small amount as possible in the above-described range.
  • the content of a high-eutectic temperature oxide is at least 5 %, preferably at least 10 %.
  • the content of oxides such as TiO2 and Cr2O3 is preferably not more than 20 %, more preferably not more than 15 %.
  • the fourth mold may contain various kinds of halides described above as well as CaO. Since addition of too much halide lowers the refractoriness, the content is not more than 5 %, preferably not more than 2 %.
  • the fourth mold may also contain an oxide, a carbide, a nitride exemplified above and carbon (C).
  • the fourth mold contains at least 40 wt%, preferably at least 70 wt %, and more preferably at least 80 wt% CaO.
  • a fifth mold is a mold provided with a layer of a calcia refractory material containing not less than 40 wt% CaO on the surface which comes into contact with a molten metal.
  • the mold Since the surface of the fifth mold which comes into contact with molten metal is made of calcia which has a high melting point and is thermodynamically stable even at a high temperature, the mold facilitates the casting of a high-melting point and/or highly active metal.
  • a casting to be obtained is a highly purified casting free from contamination of C, O, N etc., and dispenses with any after-treatment such as the removal of the contaminated layer on the surface of the casting.
  • the fifth mold is cheap and since it has high resistance to hydration and strength, it is reusable many times, thereby enabling much reduction in casting costs.
  • the fifth mold can be composed of a conventional mold material except for the surface which comes into contact with molten metal, it is possible to utilize an existing equipment and to compensate for the defects in the strength and the hydrating properties of a calcia refractory material.
  • a layer 22 of a calcia refractory material is formed on the surface of a mold body 21 which comes into contact with a molten metal.
  • the mold is a non-calcia mold such as a graphite mold or a low-calcia mold.
  • the layer 22 of a calcia refractory material is formed on the surface of the mold body 21 with an intermediate layer 23 containing a comparatively small amount of CaO interposed therebetween.
  • the composition of the intermediate layer 23 is preferably intermediate between that of the material of the mold body 21 and that of the material of the refractory layer 22.
  • the layer 22 of a calcia refractory material is formed on the surface of the mold body 21 so that the CaO content of the refractory layer 22 gradually increases toward the surface which comes into contact with a molten metal.
  • the material of the refractory layer on the side of the mold body 21 is preferably approximate to the material of the mold body 21.
  • Figs. 4(d), 4(e) and 4(f) show the distribution of the CaO contents in Fig. 4(a), 4(b) and 4(c), respectively.
  • the thickness of the layer of a calcia refractory material is not specified, and may be determined appropriately in accordance with the size of the mold, and the activity and the melting point of a metal to be cast. Preferably, it is about 0.3 to 2 cm.
  • Calcia of the refractory layer formed on the fifth mold has a high melting point and is thermodynamically stable even at a high temperature, as described above. Since the stability and the heat resistance of the mold increases with the increase in CaO content in the layer of a calcia refractory material, the layer of a calcia refractory material of the fifth mold contains at least 40 wt%, preferably at least 50 wt %, and more preferably at least 60 wt% CaO.
  • the layer of a calcia refractory material may contain a halide, an oxide other than CaO, a carbide, a nitride exemplified above and carbon (C) as well as CaO. Since addition of too much halide lowers the refractoriness of the mold, the content is not more than 8 %, preferably not more than 5 %. Needless to say, since addition of too small amount of halide does not bring about the above-described effects and actions, the content is not less than 0.1 %, preferably not less than 0.3 %.
  • the mold body on which the layer of a calcia refractory material is formed may be composed of graphite or a heat-resistant oxide except calcia such as alumina, which is ordinarily adopted as a mold material. It may also be a low calcia mold containing less than 40 % CaO.
  • the above-described calcia material and at least one selected from the group consisting of the above-described halide, oxide, carbide, nitride and carbon are prepared as the main raw material, and an appropriate binder is added thereto to constitute a molding material.
  • the molded body When the molded body is baked, it is preferable that it is dried, if necessary, calcinated at a temperature lower than the baking temperature, and is thereafter baked to be sintered.
  • the baking temperature is not lower than 900°C, preferably 1,100 to 1,700°C.
  • the step of baking may be carried out in the air atmosphere if the body to be sintered contains no carbon, but another atmosphere is possible.
  • the CaO content of the slurry in the slip cast is increased with time in the method (a), thereby facilitating the formation of the refractory layer containing CaO which gradually increases toward the surface.
  • the fifth mold may be composed by a hot pressing method or using the calcia refractory material as a stamp material.
  • the mold may be also formed by using the layer of a calcia refractory material as ordinary casting sand.
  • the binder used for molding the refractory layer As the binder used for molding the refractory layer, the above-described non-aqueous binders are ordinarily used.
  • High-melting point metals and highly active metals suitable for casting in the present invention are, for example, lanthanoid elements such as Sc, Y, La, Ce of atomic numbers 58 to 71, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Ru, Os, Co, Ni, Rh, Pd, Ir and Pt.
  • An alloy containing at least one of these elements is also suitable for casting in the present invention.
  • casting is preferably carried out in an inert gas atmosphere, for example, under vacuum or in an argon atmosphere.
  • a mold containing a large amount of CaO for example, not less than 80 wt% CaO is preferably used.
  • a mold containing a large amount of CaO is also preferably used.
  • a calcia mold having a porosity of 30 to 70 vol% is placed on a metal chill plate, a molten metal is poured by top-pouring, and the molten metal is gradually solidified from the lower part while insulating the riser of the mold, the metal chill plate increases the cooling speed appropriately, so that it is possible to refine the crystal grain and restrict the position of the shrinkage cavity to the top portion of the casting, thereby improving the yield. Since a calcia mold is used, it is possible to cast a fragile metal without producing a crack.
  • Figs. 5 and 6 are respectively side elevational views of preferred embodiments of the casting method.
  • a bottomless calcia mold 31 (having a cylindrical configuration and the cavity has a slightly tapered configuration toward the lower side in this embodiment) is placed on a metal chill plate 32, and a riser sleeve 33 of the same calcia is placed on the upper side of the mold 31.
  • the metal chill plate 32 in Fig. 5 is a single-sheet plate, and the central part of the upper surface is recessed in this embodiment for receiving the calcia mold 31 (the recessed portion is not essential).
  • the embodiment shown in Fig. 6 has the same structure as that of the embodiment in Fig. 5 except that an insulating member 34 is used in place of the calcia riser sleeve 33.
  • a molten metal is poured into the bottomless calcia mold 31 by top-pouring.
  • the poured molten metal is cooled by the metal chill plate 32 and gradually solidified from the lower part.
  • the cooling speed is higher than that of a calcia mold having no metal chill plate, so that the position of the shrinkage cavity becomes higher.
  • the riser of the mold is insulated by the calcia riser sleeve 33 or the insulating member 34, whereby the position of the shrinkage cavity become even higher.
  • the calcia riser sleeve 33 and the insulating member 34 may incorporate a heating medium, or the calcia riser sleeve 33 and the insulating member 34 may have a structure which is capable of heating so as to retain the heat of the riser of the mold by providing heat therefor. It will be possible to make the position of the shrinkage cavity still higher by heating in this way.
  • a calcia mold which is made by molding a calcia particulate molding material together with an appropriate non-aqueous binder, and baking the molded body is preferably used.
  • the calcia particulate molding material preferably contains not less than 60 %, more preferably not less than 80 % calcia.
  • a high-­purity calcia mold containing not less than 90 % calcia is preferably used.
  • the metal chill plate 32 ordinary steel plate, cast iron plate, copper plate and the like are preferable. In the case of using a metal chill plate of a water-cooling system, a copper plate is preferable.
  • a graphite insulating member facilitates the heating and the heat retaining of the riser of the mold by electrically heating or induction heating.
  • a calcia insulating member is used, if the member is made of metal powder which is mixed, molded and baked, heat retaining is also possible by induction heating.
  • the calcia mold has a porosity of 30 to 70 vol%, more preferably about 40 to 50 vol%.
  • a chromium alloy was poured in accordance with the embodiments shown in Figs. 5 and 6.
  • the dimensions of the mold 31, the metal chill plate 32 and the insulating member 34 are described in Figs. 5 and 6.
  • the riser sleeve 33 was an insulating sleeve made of calcia which was the same material as that of the mold.
  • the metal chill plates 32 in Figs 5 and 6 were made of copper.
  • the shrinkage cavity in Fig. 5 was produced at a position 1.4 cm deep from the top surface of the mold, and the shrinkage cavity in Fig. 6 at a position 0 cm deep from the top surface of the mold 31.
  • a chromium alloy was poured in the same way as in the method shown in Fig. 6 except that the bottom part of the mold 31 was closed by a calcia refractory material in place of the metal chill plate 32. As a result, the shrinkage cavity was produced at a position of 2.8 cm deep from the top surface of the mold.
  • a gypsum mold having a configuration and dimensions shown in Fig. 7 was prepared.
  • the slurry was poured into the gypsum mold, and after 30 minutes had passed the excess slurry was discharged. After this state was maintained for 1 hour more, the gypsum mold was removed.
  • the molded body was dried at 70°C for 1 hour, and thereafter calcinated at 850°C for 3 hours.
  • the molded body was then baked at 1,100°C for 3 hours to be sintered. These steps of calcinating and baking were carried out in the air atmosphere.
  • the thus-obtained sintered body 40 had a configuration and dimensions shown in Fig. 8.
  • the porosity was 25 vol%.
  • the reference numeral 41 denotes a cover, 42 a gypsum mold, 43 a vent hole, and 44 a hole for pouring and discharging a slurry.
  • a mold was produced and casting was carried out in the same way as in Example 1 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 1 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 1 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 1 except for the following conditions (a) to (g).
  • the present invention it is easy to cast a highly active metal, a high-melting point metal, and an alloy containing such a metal.
  • the casting obtained is a highly purified casting free from contamination of C, O, N, etc., and dispenses with any after-treatment such as the removal of a contaminated layer on the casting surface.
  • the molded body was dried at 100° C for 1 hour, and thereafter baked at 950°C for 3 hours in the air atmosphere to be sintered.
  • the thus-obtained sintered body had a configuration and dimensions shown in Fig. 8.
  • a mold was produced and casting was carried out in the same way as in Example 6 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 6 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 6 except for the following conditions (a) to (c).
  • a mold was produced and casting was carried out in the same way as in Example 7 except that the material for the mold was commercially available silica sand.
  • a mold was produced and casting was carried out in the same way as in Example 8 except that the material for the mold was commercially available silica sand.
  • the present invention it was easy to cast a highly active metal, a high-melting point metal, and an alloy containing such a metal.
  • the castings obtained were highly purified castings free from contamination of C, O, N, etc., and dispensed with any after-treatment such as the removal of a contaminated layer on the casting surface.
  • the thus-obtained sintered body had a configuration and dimensions shown in Fig. 8.
  • a mold was produced and casting was carried out in the same way as in Example 9 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 9 except for the following conditions (a) to (g).
  • a graphite mold having the dimensions shown in Fig. 8 was produced by machining a commercially available graphite electrode, and by using this mold pure titanium was cast in the same way as in Example 9.
  • a mold was produced and casting was carried out in the same way as in Example 10 except for the following conditions (a) to (c).
  • Table 3 shows that according to the present invention, it is easy to cast a highly active metal, a high-melting point metal, and an alloy containing such a metal.
  • the casting obtained is a highly purified casting free from contamination of C, O, N, etc., and dispenses with any after-treatment such as the removal of a contaminated layer on the casting surface.
  • the surfaces of the molds according to the present invention were smooth and the casting surfaces were also smooth.
  • the molded body was dried and calcinated at 100°C for 1 hour, and thereafter baked at 950°C for 3 hours to be sintered. These steps of calcinating and baking were carried out in the air atmosphere.
  • the thus-obtained sintered body had a configuration and dimensions shown in Fig. 8.
  • a mold was produced and casting was carried out in the same way as in Example 12 except for the following conditions (a) to (g).
  • a mold was produced and casting was carried out in the same way as in Example 12 except for the following conditions (a) and (b).
  • a mold was produced and casting was carried out in the same way as in Example 13 except for the conditions (a) and (b) in Reference Example 1.
  • Table 4 shows that according to Examples 12 and 13, it is possible to cast a highly purified alloy of approximately the same level as those of Reference Examples 1 and 2.
  • the baking temperature of the molds are considerably low and the baking time is short in comparison with those of Reference Examples 1 and 2.
  • a CaO material was prepared by crushing sintered calcia (having a CaO purity of 98 %) into particles of not more than 0.5 mm in diameter and classifying them, and other components were added thereto to prepare molding materials having the compositions shown in 1 to 3 of Table 5.
  • a calcia layer was formed of each of the molding materials on the entire inner surface of a graphite mold body by a slip casting method. The mold was dried at 250°C for 30 hours and thereafter baked at 1,200°C for 2 hours in vacuo to be sintered, whereby a layer of a calcia refractory material was formed. The step of baking was carried out in the air atmosphere.
  • the thus-obtained mold had a configuration and dimensions shown in Fig. 9. In Fig.
  • the reference numeral 51 denotes a mold body, and 52 a layer of a calcia refractory material.
  • an alloy consisting of 80 % Ti and 20% Ni was cast at 0.2 atm in an argon atmosphere.
  • the temperature of the molten metal at the time of casting was 1,600°C.
  • the molten metal was poured into the mold, and after solidification chemical analysis of O, N and C on the surface of the casting was carried out. The results are shown in Table 6.
  • Casting was carried out in the same way as in Example 14 by using an Al2O3 mold and a graphite mold.
  • the present invention it is easy to cast a highly active metal, a high-melting point metal, and an alloy containing such a metal.
  • the casting obtained is a highly purified casting free from contamination of C, O, N, etc., and dispenses with any after-treatment such as the removal of a contaminated layer on the casting surface.
  • the sintering ability and the resistance to hydration of the molds were very high.
  • Examples 15 to 17 production of a porous mold by utilizing an injection molding process and casting by using the mold
  • the particulate molding material and polyethylene powder were charged into a sand mill provided with a heater. After the temperature was raised to 150°C to knead the materials adequately, the mixture was cooled. The mixture was crushed by an attrition mill and thereafter sieved so that the particle diameter was not more than 0.3 mm. The sieved material was charged into a screw in-line type injection molding machine and was injected into the die.
  • Fig. 8 shows the dimensions of this mold.
  • a mold was produced and casting was carried out in the same way as in Example 15 except for the following conditions (a) to (g).
  • a mold having a porosity of 56 vol% was produced and casting was carried out in the same way as in Example 15 except for the following conditions (a) to (g).
  • Casting was carried out under the same conditions as in Example 17 except that the mold was a metal (steel) mold.
  • the results of the chemical analysis of the surface of the casting obtained and the measurement of the shrinkage cavity are shown in Table 7.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
EP19870100559 1986-01-17 1987-01-16 Giessform, Verfahren zur ihrer Herstellung und Giessverfahren Expired EP0233478B1 (de)

Applications Claiming Priority (16)

Application Number Priority Date Filing Date Title
JP766486A JPH0628776B2 (ja) 1986-01-17 1986-01-17 鋳 型
JP7664/86 1986-01-17
JP766186A JPH0628774B2 (ja) 1986-01-17 1986-01-17 鋳 型
JP765886A JPS62168659A (ja) 1986-01-17 1986-01-17 カルシア鋳型を用いた鋳込方法
JP7663/86 1986-01-17
JP7662/86 1986-01-17
JP7661/86 1986-01-17
JP765986A JPS62168628A (ja) 1986-01-17 1986-01-17 鋳型、鋳型の製造方法及び鋳造方法
JP7659/86 1986-01-17
JP766386A JPS62168630A (ja) 1986-01-17 1986-01-17 鋳型
JP7658/86 1986-01-17
JP766286A JPH0628775B2 (ja) 1986-01-17 1986-01-17 鋳 型
JP766086A JPS62168632A (ja) 1986-01-17 1986-01-17 多孔質カルシア鋳型の製造方法
JP7660/86 1986-01-17
JP1091686A JPH0635029B2 (ja) 1986-01-21 1986-01-21 カルシア鋳型の製造方法
JP10916/86 1986-01-21

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EP0233478A1 true EP0233478A1 (de) 1987-08-26
EP0233478B1 EP0233478B1 (de) 1991-04-24

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Cited By (2)

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Publication number Priority date Publication date Assignee Title
EP0320811A1 (de) * 1987-12-16 1989-06-21 Eta SA Fabriques d'Ebauches Verfahren zur Herstellung einer Form zum Herstellen sehr kleiner Formkörper
JP2014205897A (ja) * 2013-04-16 2014-10-30 国立大学法人富山大学 Ａｌ−Ｌｉ系合金の製造方法

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US1902419A (en) * 1931-07-30 1933-03-21 Dow Chemical Co Molding composition and method of treating
US2201366A (en) * 1939-08-02 1940-05-21 Vladimir A Grodsky Mold composition and method of producing same
US2876122A (en) * 1953-08-26 1959-03-03 Norton Co Calcium oxide articles and method of making the same
US3460606A (en) * 1965-07-19 1969-08-12 Foseco Int Method of forming a casting mold
DE2047041A1 (en) * 1969-09-26 1971-04-01 Toyoda Chuo Kenkyusho Kk Iron melt containers with protective oxide - layers
GB1346576A (en) * 1971-04-19 1974-02-13 Secr Defence Method of making a mould or mould piece
USB511885I5 (de) * 1974-10-03 1976-01-27
JPS54849A (en) 1977-06-03 1979-01-06 Nec Corp Pll oscillator circuit

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1902419A (en) * 1931-07-30 1933-03-21 Dow Chemical Co Molding composition and method of treating
US2201366A (en) * 1939-08-02 1940-05-21 Vladimir A Grodsky Mold composition and method of producing same
US2876122A (en) * 1953-08-26 1959-03-03 Norton Co Calcium oxide articles and method of making the same
US3460606A (en) * 1965-07-19 1969-08-12 Foseco Int Method of forming a casting mold
DE2047041A1 (en) * 1969-09-26 1971-04-01 Toyoda Chuo Kenkyusho Kk Iron melt containers with protective oxide - layers
GB1346576A (en) * 1971-04-19 1974-02-13 Secr Defence Method of making a mould or mould piece
USB511885I5 (de) * 1974-10-03 1976-01-27
US3981346A (en) 1974-10-03 1976-09-21 United Technologies Corporation Method and apparatus for directional solidification
JPS54849A (en) 1977-06-03 1979-01-06 Nec Corp Pll oscillator circuit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0320811A1 (de) * 1987-12-16 1989-06-21 Eta SA Fabriques d'Ebauches Verfahren zur Herstellung einer Form zum Herstellen sehr kleiner Formkörper
FR2624770A1 (fr) * 1987-12-16 1989-06-23 Ebauchesfabrik Eta Ag Procede de realisation d'un moule destine a la fabrication de pieces de tres petites dimensions
US4923672A (en) * 1987-12-16 1990-05-08 Eta Sa Fabriques D'ebauches Method of obtaining a mould intended for the manufacture of very small parts
JP2014205897A (ja) * 2013-04-16 2014-10-30 国立大学法人富山大学 Ａｌ−Ｌｉ系合金の製造方法

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EP0233478B1 (de) 1991-04-24

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