EP0590186B1 - Noyaux pour la coulée à la cire perdue - Google Patents

Noyaux pour la coulée à la cire perdue Download PDF

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Publication number
EP0590186B1
EP0590186B1 EP92116699A EP92116699A EP0590186B1 EP 0590186 B1 EP0590186 B1 EP 0590186B1 EP 92116699 A EP92116699 A EP 92116699A EP 92116699 A EP92116699 A EP 92116699A EP 0590186 B1 EP0590186 B1 EP 0590186B1
Authority
EP
European Patent Office
Prior art keywords
core
wax
zircon
quartz
weight
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.)
Expired - Lifetime
Application number
EP92116699A
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German (de)
English (en)
Other versions
EP0590186A1 (fr
Inventor
Klaus Hanke
Peter Spiegel
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.)
H Seelmann & Co GmbH
Original Assignee
H Seelmann & Co GmbH
Seelmann & Co H GmbH
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Filing date
Publication date
Application filed by H Seelmann & Co GmbH, Seelmann & Co H GmbH filed Critical H Seelmann & Co GmbH
Publication of EP0590186A1 publication Critical patent/EP0590186A1/fr
Application granted granted Critical
Publication of EP0590186B1 publication Critical patent/EP0590186B1/fr
Anticipated expiration legal-status Critical
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • 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

Definitions

  • the invention relates to a core for the investment casting of carbon steels according to the lost wax process, which consists of quartz (SiO 2 ) and smaller parts by weight of zircon (ZrO 2 ) and aluminum oxide (Al 2 O 3 ), and before the core is fired (greener Core) comprises a binder with wax.
  • cores are used in addition to the actual shape.
  • the core is dimensioned so that it describes the shape and dimensions of the later cavities in the casting. Its material should be selected so that it can withstand the pressures and temperatures prevailing there without affecting the shape during casting, and is dimensionally stable and, on the other hand, can be quickly and easily released from the casting after application of liquids such as alkalis, acids, salts .
  • the castings are produced using the lost wax process with the aid of the core.
  • the so-called green core is first produced in accordance with the later shape of the cavity, which contains binding agents and lubricants - according to the process name, these are usually wax and similar material compounds - which in a later firing process leave no residue burn and thereby leave pores in the material.
  • Only the core obtained in this way is used to manufacture the steel casting by placing it in a mold and casting it with wax.
  • the cavities in the casting are exposed by washing out with the aid of alkalis, acids, salts and other liquids, for which experience has shown that all types of silicate compounds are suitable.
  • cores for investment casting using the lost wax process are known, the structure of which consists predominantly of quartz in the form of christobalite and / or tridynite and / or quartz glass with the addition of a binder in the form of stearin or plastic and zirconium silicate.
  • a binder in the form of stearin or plastic and zirconium silicate.
  • additives in the form of sintering aids that are intended to support caking at low temperatures.
  • the SiO 2 in the above compound is in the form of a needle or plate.
  • GB-A-2 202 541 also describes a core consisting of quartz, aluminum oxide and zircon, and a method for its production, wherein wax is used as a binder.
  • a disadvantage is that, despite intensive efforts, it has so far not been possible to achieve a sufficiently high dimensional accuracy and a low shrinkage.
  • the invention has the further development of such cores that can be used for investment casting by the lost wax process Task made to achieve a higher dimensional accuracy due to less shrinkage.
  • the proportion by weight of aluminum oxide and zirconium is approximately the same, the binder contains stearin, the proportion by weight of wax and stearin is the same and the quartz consists of grains of round or polyhedral shape.
  • the predominant part consists of normal, not pretreated SiO 2 with grains of polyhedral or spherical shape.
  • SiO 2 the following is decisive for the invention:
  • SiO 2 experiences a volume increase of up to 20% when heated and, conversely, shrinks when it cools down.
  • the disadvantageous consequence is a high tendency to crack. It is crucial that at a temperature of 1200 ° and the high pressures prevailing in the green core in the contact points of the individual SiO 2 grains, cross-linking takes place through physical force in the sense of caking in the contact points. The result is a high strength, which gives the ceramic the properties of a tightly burning ceramic with pores, with the consequence of significantly higher temperature resistance with water permeability. It is a ceramic with pore formation.
  • quartz grains are approximately spherical. This shape inevitably results from the mechanical comminution of SiO 2 in the systems provided for this purpose.
  • the needle and plate-shaped structures of SiO 2 as used in the prior art, are created by crushing in crushers or tube mills. The roughly spherical grain is therefore the cheapest grain on the market.
  • the amount of SiO 2 outweighs the other constituents in percent by weight and they are chosen so that together with the other components the mathematically exact 100% results.
  • the result is a volume-stabilizing influence on the ceramic, a high, far above the metal's softening temperature of 2715 ° C (when casting metal temperatures between 1450 ° to 1780 ° C occur in the mold), which also has a high dimensional stability and low shrinkage.
  • the advantage compared to the aluminum oxide mentioned later in detail is the ease of processing and the comparatively high degree of softness.
  • the naturally high purity of the material also contributes to a high softening temperature, since impurities naturally lower the softening temperature.
  • magnesium (Mg) stabilized zirconium oxide In terms of volume stabilization, it is particularly advantageous to use magnesium (Mg) stabilized zirconium oxide.
  • the components just described determine the material structure of a core after the firing process. It has a high strength, good, i.e. smooth surfaces, no shrinkage, advantageous resistance to temperature changes and homogeneous pores. Furthermore, the dimensional accuracy is very high, since there is little tension during burning and degassing, which would give rise to delay.
  • the advantages of the ceramic core offer superior properties, which are expressed numerically as follows.
  • the shrinkage is only 0.1% compared to the cores of the prior art, in which it is at least 0.5%.
  • the high dimensional accuracy results in tolerances of ⁇ 0.023% over a length of 100 mm.
  • binders are also present, which burn and evaporate without residue during the later firing process, thereby creating the voids forming the pores.
  • stearin and wax are used in approximately the same percentages by weight, i.e. 5.5 weight percent used.
  • Stearin has the property of being very hard and therefore difficult when the green core is removed from the mold. It sticks, is inelastic and therefore highly prone to breakage and is expensive to buy. The melting interval is small. The advantage is the timely setting when injected into the mold so that sticking is prevented, high hardness and thus a correspondingly low scratch sensitivity and a very good ability to evaporate.
  • Wax on the other hand, has the advantage of a large softening interval and therefore never becomes completely liquid like water. Due to the high surface tension, it has the property of completely enclosing the surrounding particles. It has good wettability and is endeavored to always take the spherical shape of the surface tension.
  • the binders enclose the raw materials, so that the green cores remain stable. A uniform shaping of the mold cavities in the injection mold is also achieved. Furthermore, the complete orientation of the grains with binder and additional cooling during the spraying process largely eliminates the particle orientation.
  • the binders consisting of wax, stearin or the like and in this way leaving voids and pores within the core which is now being formed.
  • the core obtained in this way is placed in a mold, overmolded with wax, the wax part is dipped together with the ceramic core in immersion ceramic as a mask and after melting and Firing the immersed ceramic steel bowl. To uncover the cavities in the casting, the quartz is then released from the workpiece using alkalis and acids.
  • the firing curve of the green core slowly increases up to 450 ° with the addition of air, so that oxidations are present which prevent carbon from being deposited.
  • the freedom from carbon means that no adverse reactions with steel can occur.
  • the binders and lubricants must burn as little as possible in this part of the firing curve.
  • the holding time can be two to five hours and the subsequent one Depending on the time, the cooling phase can be designed as desired.
  • the binder is in the form of wax and stearin, which does not swell and prevent contribute to any chemical reaction.
  • the binders also ensure that the "green core” remains stable, ie the core before it burns out.
  • the mold cavities are uniformly shaped during injection molding, ie the production of the green core.
  • the coating requires the particle orientation to be largely eliminated and eliminated.
  • the drawing shows the green core, ie the unfired core, so that the binders, which consist of wax and stearin (4) in the case according to the invention, are indicated.
  • the structure shown in the drawing changes in such a way that the binder (4) is completely burned and cavities and pores are formed in its place.
  • the result is a ceramic core for investment casting using the lost wax process, which is characterized by its high dimensional accuracy and strength, its homogeneous pores with minimal shrinkage.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Dental Preparations (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Claims (6)

  1. Noyau pour le moulage à moule perdu d'aciers au carbone selon le procédé de moulage à la cire perdue composé de quartz (SiO2) et d'une faible proportion en poids de zircon (ZrO2) et d'oxyde d'aluminium (Al2O3) et qui, avant la cuisson du noyau (noyau primaire) entoure un liant avec de la cire, caractérisé en ce que
    - la proportion en poids d'oxyde d'aluminium et de zircon est à peu près la même
    - le liant contient de la stéarine,
    - la proportion en poids de cire et de stéarine est la même
    - et le quartz est constitué par des grains ronds ou ayant la forme de polyèdres.
  2. Noyau selon la revendication 1, caractérisé en ce que la proportion de zircon (ZrO2) et/ou d'oxyde d'aluminium (Al2O3) est comprise dans une plage de 18 à 26,5 pour cent du poids.
  3. Noyau selon les revendications 1 ou 2, caractérisé en ce que les liants qui sont de la cire et/ou de la stéarine ont une proportion d'environ 5,5 pour cent du poids.
  4. Procédé pour la cuisson du noyau brut (noyau primaire) conformément à la revendication 1, caractérisé par les pas suivants:
    - lente augmentation de la température de cuisson pour atteindre 450° avec alimentation en air (cuisson oxydante)
    - augmentation légèrement plus rapide de la température de cuisson pour passer de 450° à 700° sans alimentation en air (cuisson neutre)
    - rapide échauffement pour passer de 700 à 1200°
    - maintien de la température pendant 2 à 5 heures dans une atmosphère neutre
    - phase de refroidissement avec dépendance temporelle quelconque.
  5. Noyau pour le moulage à moule perdu d'aciers au carbone selon le procédé de moulage à la cire perdue fabriqué selon la revendication 4 qui est composé de quartz (SiO2) et d'une faible proportion en poids de zircon (ZrO2) et d'oxyde d'aluminium (Al2O3) après la cuisson du noyau caractérisé en ce que
    - la proportion en poids d'oxyde d'aluminium et de zircon est la même,
    - et le quartz est constitué par des grains ayant la forme de boules ou de polyèdres.
  6. Noyau selon la revendication 5 caractérisé en ce que le noyau présente des pores en une proportion de 17 pour cent du volume.
EP92116699A 1991-09-30 1992-09-30 Noyaux pour la coulée à la cire perdue Expired - Lifetime EP0590186B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4132477A DE4132477A1 (de) 1991-09-30 1991-09-30 Kern nach dem wachsausschmelzverfahren
DE4132477 1991-09-30

Publications (2)

Publication Number Publication Date
EP0590186A1 EP0590186A1 (fr) 1994-04-06
EP0590186B1 true EP0590186B1 (fr) 1997-03-19

Family

ID=6441779

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92116699A Expired - Lifetime EP0590186B1 (fr) 1991-09-30 1992-09-30 Noyaux pour la coulée à la cire perdue

Country Status (4)

Country Link
EP (1) EP0590186B1 (fr)
AT (1) ATE150346T1 (fr)
DE (2) DE4132477A1 (fr)
ES (1) ES2103336T3 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19615896C2 (de) * 1995-04-21 1998-01-22 Beermann Norbert Dipl Volksw Starrer Sandkörper, Verfahren zu dessen Herstellung, dessen Verwendung und Verfahren zur Herstellung von mit Wachs umhüllten Sandkörnern
ES2177985T3 (es) 1997-06-12 2002-12-16 Norbert Beermann Cuerpo de arena rigido, procedimiento para su produccion, su utilizacion y procedimiento para la produccion de granos de arena revestidos decera.
CN104086161B (zh) * 2014-04-29 2016-06-01 中国科学院金属研究所 一种可调节热膨胀系数的硅基陶瓷型芯的制备方法
CN109346306A (zh) * 2018-10-26 2019-02-15 合肥工业大学 一种用于钕铁硼磁体表面防护的原位复合涂层及其制备方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2042951B (en) * 1978-11-08 1982-08-04 Rolls Royce Investment casting core
GB2096523B (en) * 1981-03-25 1986-04-09 Rolls Royce Method of making a blade aerofoil for a gas turbine
GB2126569B (en) * 1982-09-04 1986-01-15 Rolls Royce Non-silica based ceramic cores for castings
GB2202541A (en) * 1987-02-24 1988-09-28 United Technologies Corp Method for manufacturing investment casting cores
FR2626794B1 (fr) * 1988-02-10 1993-07-02 Snecma Pate thermoplastique pour la preparation de noyaux de fonderie et procede de preparation desdits noyaux
JPH0333060A (ja) * 1989-06-28 1991-02-13 Morita Mfg Co Ltd 高温造形用焼成型及びこれに用いる高温造形用型材並びに高温造形用焼成型の製造法

Also Published As

Publication number Publication date
DE59208246D1 (de) 1997-04-24
DE4132477A1 (de) 1993-04-01
ES2103336T3 (es) 1997-09-16
ATE150346T1 (de) 1997-04-15
EP0590186A1 (fr) 1994-04-06

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