Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00939—Uses not provided for elsewhere in C04B2111/00 for the fabrication of moulds or cores
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material
  • C04B2111/1018—Gypsum free or very low gypsum content cement compositions
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the invention relates to an embedding or molding compound dry ischung for metal casting according to the preamble of claim 1 and embedding or molding compounds thereof and their use.
• the lost wax process is used in particular for precision casting.
• the lost wax process requires a wax model for each cast part to be produced.
• This wax model is coated with a liquid embedding compound, in particular made of plaster.
• a solid container is then built around the wax model coated with the plaster and filled with a liquid embedding compound, in particular also plaster.
• the completely dried casting compound is heated in the oven until the wax melts, evaporates and burns inside.
• a hollow body has now been created in the container that corresponds to the model.
• the metal casting can then be carried out.
• the liquid metal alloy is poured into the cavity in the casting compound.
• the casting is slowly removed let cool.
• the sheath is broken out of the hardened embedding compound.
• various chemicals act on the metal surface, for example to achieve an antique effect.
• plaster molds are usually produced. Plaster molds contain up to 20 M% crystal water even after the wax has been driven out. Therefore, hot metal must not be poured into these molds at first. The plaster molds must be dried and dewatered before casting.
• phase changes typical of the plaster take place, which, however, can bring about undesirable structural changes.
• these cause shrinkage and thus the formation of shrinkage cracks and, after cooling, cooling cracks.
• the. Porosity and gas permeability increased.
• certain metals magnesium
• can also cause chemical reactions in the gypsum which is also undesirable.
• Another disadvantage when using gypsum is that these gypsum masses are usually produced with a vacuum stirrer in order to degas the gypsum mass before pouring.
• the object of the invention is to provide an embedding or molding compound dry mixture for embedding or molding compounds for metal casting, which enables a long controllable processing time, high temperature resistance and simple and fast processing.
• Another object is to provide an embedding or molding compound for metal casting, which enables a long controllable processing time, high temperature resistance and simple and quick processing, as well as castings with a given structure.
• a binder mixture for embedding or molding compounds for metal casting has a hydraulic binder as the binder component of the constituents of the binder mixture, this binder being, according to the invention, a hydraulic binder free of sulfate carriers and in particular a hydraulic fine binder free of sulfate carriers. Finely or very finely ground Portland cement clinker is used as the sulphate carrier-free hydraulic binder.
• a binder mixture or an embedding or molding compound can be adjusted very sensitively over a very wide range with regard to the solidification process, the hardening process and the viscosity with the sulfate-carrier-free hydraulic binder used according to the invention. It has also been found that very smooth surfaces can be achieved with the binder mixture or embedding or molding compositions according to the invention using the binder according to the invention, so that the reworking of a casting is minimized.
• the mass according to the invention can in principle be used in all molding processes, in those with a lost one Shape is worked. Particularly in the lost wax process, when molding with half molds, etc. With a correspondingly stable design of the molding box, even high pressure die casting processes can be implemented due to the high strength of the hardened molding compound. In molding processes in which a molded body is cast in a mold with two mold halves and then removed by moving the two mold halves apart, it is also possible due to the high stability and strength of the hardened molding compound to mold the mold several times in succession, in particular for to use the production of small series.
• influence can be exerted on the material properties of the molded part by presetting the thermal conductivity of the composition in the molding composition according to the invention, so that the cooling rates of the poured-in metal are adjustable and in particular are significantly higher than in the case of known molding compositions.
• the binder free of sulfate carrier used according to the invention is, for example, Portland cement clinker powder.
• Portland cement clinker is the kiln-falling good that leaves the cement rotary kiln. This kiln-falling material is usually ground together with so-called sulfate carriers such as gypsum or anhydrite or mixtures thereof to form Portland cement, then sifted and then optionally packaged.
• the hydraulic binder that is free from sulfate carriers is a Portland cement clinker that is ground without the addition of sulfate carrier.
• the sulfate carrier additive has the task of regulating the setting by the formation of the mineral ettringite on the surface of the tricalcium aluminate (C 3 A).
• combinations of Portland cement clinker powders and / or latent hydraulic substances such as blastfurnace slag powders and / or pozzolanic substances such as trass and microsilica, metakaolinite, untreated or tempered zeolites, and / or inert, finely ground rock powders, such as Limestone powder and / or hydraulic limes and / or calcium silicates and / or calcium aluminates or any combination of these components can be used.
• the fineness of the clinker flours used or the binder constituents used range from normal cement fineness to the highest fineness.
• the binder component can also be composed of fractions of different fineness.
• the individual components of the binder component listed can also have different finenesses.
• the binder component preferably has the fineness of very fine cements.
• Ultra-fine cements are very fine-grained hydraulic binders, especially with continuously and narrowly graded grain distributions and a limitation of the largest grain.
• the properties and the usual use of ultra-fine cements can be found, for example, in a preliminary leaflet for press-in work with ultra-fine binders in loose rock (Bautechnik 70, [1993], number 9, Ernst & Sohn, pages 550 to 560, and ZTV-RISS 93, pulpblatt -Document B 5237, pulpblatt-Verlag).
• the grain distribution of the dry batch is advantageously adjusted in accordance with a modified Gaudin-Schumann function, which is also known as the 3,r-Funk function (Funk, James G.; 3,r, Dennis R.; Predictive process control of crowded particulate suspensions; Cluver Academic Publishers Group, Distribution Center 3300AH Dordrecht, NL).
• An exponent n ⁇ 0.2 is set in the 3,r radio function, whereby negative values are also possible. This makes it possible to produce a hardened mass with a maximally dense structure.
• the binder mixture or the embedding or molding composition has, for example, a binder component free of sulfate carriers and a flow agent free of sulfonate groups as an additive.
• the flow agent which is free from sulfonate groups, in particular polycarboxylates also has a delaying effect on the early solidification of the sulfate-free binder component within a short period of time, for example 2 to 10 minutes. This is attributed to the fact that the flow agents which are free from sulfonate groups, in particular polycarboxylates, apparently hinder undesired crystal growth in the short term.
• modified polycarboxylates used are described, for example, in DE 196 53 524 AI. They are mostly homo- or copolymeric carboxyl-containing monomers whose side chains are modified. Substances from the group of polyaspartic acids and / or polyacrylates are also suitable as flow agents free of sulfonate groups.
• the binder composition can optionally contain accelerators.
• Suitable accelerators are, for example, alkali carbonates or alkali bicarbonates and calcium nickel alkali silicates, alkali hydroxides, alkaline earth hydroxides, chlorides of polyvalent cations (eg calcium chloride), A compounds as well as calcium formate and other known accelerators and of course mixtures of the accelerators mentioned.
• the accelerators are used in particular when a lot of polycarboxylate is added due to the need for liquefaction with a low water-binding agent value.
• the decelerator can be used to set the deceleration, especially if it goes beyond a desired level.
• the sulfate-free flow agent in particular polycarboxylate, is added in particular in amounts of 0.25 to 2% by mass, based on the binder. For example, delays of 2 to 10 minutes can be achieved with very good liquefaction. Due to the strong liquefaction effect, the amount of water added and thus the porosity of the binder glue or the hardened binder stone can be reduced, which increases the strength.
• the components of the binder mixture i.e. the binder component, the sulfate-free plasticizer (s) and, if applicable, accelerators and other known additives and / or additives, such as defoamers or additives, can, if they are present in a dry state, be kept pre-mixed as a factory dry mix, which is kept before the Manufacture of the mold only needs to be mixed with water.
• Stabilizers can also be used in the binder mixture.
• stabilizers from the group of the microbial polysaccharides are used. These are synthetic
• Biopolymers of which xanthan and welan in particular are suitable for the purposes according to the invention. Particularly suitable biopolymers are described, for example, in a Velco brochure "Xanthan Gurrt", pages 1 to 24, and in particular on page 1, column "Microbial polysac ⁇ harides”. These are dextran, gellan gum, rhamsan gum, welan gum and xanthan gum.
• a hydraulic binder composition according to the invention can hereby easily be e.g. regarding the processability, the onset of solidification, the level of early strength, the level of final strength and durability of final strength. adjusted in the factory to meet the specific requirements.
• the binder composition can alternatively or additionally contain a solidification retarder, optionally a plasticizing solidification retarder.
• alkali metal gluconates are used in conjunction with alkali metal carbonates and / or alkali metal bicarbonates for sensitive control of the solidification behavior.
• customary plasticizing solidification retarders containing sulfonate groups are used in particular as additives. These are, for example, lignin sulfonates, sulfon soaps, sulfonic acids, alkylbenzene sulfonates, naphthalene sulfonates and sulfonated melamine formaldehyde condensates. However, these can in particular also be partially replaced by other sulfonate group-free retarders.
• cellulose ethers methyl, ethyl and / or propyl ether
• mono- and / or polysaccharides fructtose, glucose
• acrylic acids and their salts eg citric acid
• oxycarboxylic acids and their salts eg citric acid
• phosphoric acids and their salts eg citric acid
• boric acid and their salts alkylamides, styrene-butadiene.
• the use of the polycarboxylates together with known sulfonate group-containing retarders, which at the same time also act as a plasticizer, in combination with accelerators known per se has the effect that the agents containing sulfonate groups are only effective with regard to the delay and do not influence the liquefying effect of the polycarboxylates.
• the sulfonate-containing plasticizers can be added without observing very precise limit values, because it is sufficient to add at least the amount necessary for decelerating a predetermined amount of binder. Larger quantities do not interfere with the delaying process or the liquefying effect of the polycarboxylates.
• the use of the additive combination mentioned not only enables the above-mentioned properties to be controlled very precisely, but also ensures that unusually high early strengths and permanently higher final strengths can be achieved. • In spite of the presence of retarders containing sulfonate groups and conventional accelerators, a sticky, rubbery consistency which interferes with the use surprisingly no longer develops.
• Property influences serve, for example, to use grinding aids. Further control of the above-mentioned properties by means of certain grain fractions and / or grain belts can be carried out, for example, with the following clinker meal fractions from selected fine meal:
• additives can also be saved or the processability, early strength and / or final strength controlled, e.g. be increased.
• additives can also be saved in other hydraulic binder compositions and the processability, early strength and / or final strength can be controlled with a certain quantity and type of additives.
• the plasticizer (superplasticizer) can be included in the factory in a factory dry mix in the binder mix.
• Ligin sulfonates in conjunction with alkali carbonates can also be used for solidification and hardening control.
• Sodium and potassium carbonate are used as alkali carbonates in any mixing ratio depending on the task.
• the early strength of the binder paste that is to say the embedding compound
• the strength development of the prepared binder mixture can thus be adjusted in the factory by a suitable mixture of sodium and potassium carbonate be, the strength development in particular in the range of 2 to 24 h can be controlled by the ratio of alkali metal carbonates.
• the Na 2 0 equivalent - matched to these parameters - is kept constant and only the ratio of K 2 C0 3 / (K 2 C0 3 + Na 2 C0 3 ) changed within the constant Na 2 0 equivalent.
• the processing time can be set by additional additives such as lignin sulfonate within a limited time window without sustained loss of strength at early times. In this respect, a wide variability in the beginning of the strength and the level of strength of the paste is created. Another possibility of influencing the strength development and the beginning of the strength development lies in the fineness of the binder component used.
• these parameters can also be controlled by individually mixing the binder constituent, in this case the clinker meal, from different grain fractions for the application.
• Quartz sand up to 2 mm grain size
• fireclay flour sillimanite flour
• kernel flour kernel flour
• metakaolinite metallurgical flour
• the temperature resistance can be increased significantly, particularly with chamotte, sillimanite, kyanite and metakaolinite.
• the thermal conductivity of the mass is adjustable. It is known that the cooling rate of a metallic workpiece has an influence on its crystalline structure and thus on the material properties. With the invention it is possible due to the controllable, presettable thermal conductivity of the embedding compound To influence material properties in a targeted manner.
• the thermal conductivity can be adjusted via the grain distribution of the dry batch and the controllable porosity or packing density. This is particularly successful if the already mentioned grain distribution is put together in accordance with a 1973r radio function, the exponent n in the distribution function being set, for example, to n ⁇ 0.2 and in particular being negative, in order to set the highest possible packing density and thus thermal conductivity.
• the set porosity is ⁇ 10%.
• the thermal conductivity can also or additionally be influenced by the type of addition of the mass.
• the aggregates such as quartz or sand or other residue minerals are completely or partially replaced by inorganic solids with a significantly higher specific thermal conductivity.
• silicon nitride, silicon carbide, nitrides, grenades, sintered corundum and feldspars are used for this.
• the composition may also contain for increasing the thermal conductivity of metals, 'in particular in the form of cooling in iron rod or bar form, metallic fibers and / or metal granules and / or metal dusts. Correspondingly classified metal waste can also be used for this.
• a model is preferably first coated with a layer of a composition according to the invention with inorganic additives and then a composition containing metal granules or dust is applied. This prevents a possible reaction of the cast metal with the metal in the mass, if one has to be expected.
• cooling irons known per se can also be introduced into the compound. These cooling irons are metal objects in the form of bars or bars that are embedded by the mass and because of their high thermal conductivity they can absorb the heat from the casting well. Such cooling irons can also be used for a mass with only inorganic additives.
• compositions according to the invention which enable a high thermal conductivity, with inorganic additives, thermal conductivities can already be set which are clearly above 0.006 J • s "1 • K " 1 .
• the mixture can also contain carbon in the form of carbon black and / or graphite.
• carbon in the form of carbon black and / or graphite As a result, the wettability of the surface of the mold with metal can be influenced and in particular reduced.
• reaction partners in the mass which react endothermically when the metal is poured in and thereby additionally remove heat from the system. These are e.g. Mixtures of calcium carbonate and metakaolinite or calcium carbonate and microsilica.
• the compositions according to the invention solidify and harden hydraulically in a concrete-like manner, they are completely water-resistant.
• the mold can be filled with water both from the outside and through channels.
• the channels can - especially in the case of larger fittings - also be formed by molding wax or the like and installed accordingly in the molding box.
• the models of the channels are then also melted out or burned out.
• appropriate connectors which may be present on the molding box, these channels can then be flowed through with water.
• the structure of the cast metal can be influenced in a targeted manner. Since large-scale castings are made in metal molds, they have a different one Structure and other material properties than prototypes or small series parts, which were made in plaster or other known forms. By using the compositions according to the invention, small series or prototypes can also be produced in such a way that the material properties of the moldings come very close to those of the large series. This makes it possible for the first time to estimate the suitability of a component cast in a lost mold considerably easier using the prototype, since the prototype almost corresponds to the large-scale part.
• burnout substances to the binder mixture according to the invention for an embedding or molding compound, which are also burned out after a thermal treatment, in particular after the wax has burned out, and specifically have pores or channels in the hardened mass leave. This is important in order to discharge the hydrogen or other gases dissolved in the metal into the mass via the channels and thus to obtain a blow-free cast body.
• burn-out substances are polypropylene fibers (3 to 20 mm in length), dolamite fibers, generally plastic fibers which burn out up to approx. 200 °, as well as cellulose fibers and wood chips or wood flour. It has also proven to be advantageous to add animal meal or bone meal, since the fats and tissue fibers contained also produce pores and tubules in an excellent manner when burned out. In addition, the remaining phosphate increases the fire resistance significantly.
• the setting and hardening in place of the sulfate carrier is regulated very sensitively and over a wide range by the addition of the additives mentioned.
• binders of this type are described as inorganic systems made of clinker flour with very high specific surfaces, plasticizers and alkali salts. The observed liquefaction The effect of the additives appears to be related to their ability to effectively disperse the clinker particles in an aqueous suspension.
• binders do not contain a sulfate carrier, lower-water calcium carboaluminates form on the surface of the tricalcium aluminate instead of ettringite (a sulfoaluminate with 32 water molecules) as the earliest hydrate phases.
• the embedding or molding compound according to the invention based on Portland cement free from sulphate carrier resists the influence of elevated and high temperatures better than the mortar made of conventional Portland cement.
• Their resistance to high temperatures and temperature shock corresponds to that of a mortar with alumina cement, which is the typical cement for the refractory industry, but the compositions according to the invention have a considerably higher long-term stability. Combinations with microsilica are also possible, which further improve their resistance to high temperatures.
• the properties of the contact zone between the aggregate and the sulfate-free binder were examined. The contact zone proved to be very compact and ensured a high bond strength of the matrix.
• the bond between the aggregate and the sulfate-free binder in the embedding or molding compound according to the invention is twice higher than the corresponding bond strength of the aggregate with Portland cement.
• gypsum-bonded investment materials are preheated before melting, for example depending on the size of the mold with temperature increases of 40 to 60 ° C per hour with different dwell times (2 hours at temperatures up to 300 ° C, 4 hours at temperatures of about 700 ° C) this is not necessary in the case of the embedding or molding compositions according to the invention based on the sulfate-free binders used according to the invention.
• the pre-tempering is related to the high bound and unbound water content of the gypsum mass, which leads to cracking when heated quickly.
• the mix The ratio for gypsum-bonded investment materials is 100 parts powder to 38 to 40 parts water.
• the processing time of the gypsum-bound investment materials is about 10 to 12 minutes.
• the embedding or molding compounds with a binder that does not contain sulfate carriers are produced with a low water cement value. Because no ettringite forms, these systems are low in water.
• the embedding or molding compound according to the invention flows quickly and easily into the mold, the products from this compound surprisingly showing a pore-free surface that is considerably smoother than that of a plastering compound used comparatively.
• the processing time of the compositions according to the invention is, for example, 30 to 40 minutes at 20 °, but it is very sensitive for the respective application and can be controlled over a very wide range from a few minutes to several hours.
• the mass results in strengths that are many times higher than the strength of known molding compositions.
• the embedding or molding compound according to the invention can advantageously be used in a large number of molding processes.
• the composition according to the invention can be used in the lost wax process, in particular in the production of individual castings or small series for prototype construction.
• the invention can also be used with advantage in all other molding processes with a lost mold. All possible metals can be cast, and magnesium in particular can also be cast. Magnesium cannot be poured into molding compounds for lost molds, especially in plaster. Due to the high strength of the compositions according to the invention after hardening, molds with mold halves which can be moved towards and away from one another can also be produced, in which Small series can be produced because the high strength means that the molds are not already destroyed by a casting. Furthermore, with a suitable design of the molding box, it is also possible to produce castings using moderate pressure.
• compositions according to the invention are also outstandingly suitable in the refractory sector as binders, refractory mortar and concrete as well as repair and ramming compositions, in particular in the case of alkaline attack.
• the drying time of the hardened molding compound is a major advantage compared to plaster molds.
• molding compositions according to the invention result in a shape which has a very high strength, in particular with respect to plaster molds. After hardening, the molding compositions according to the invention are resistant to high temperatures, to thermal shock and have an adjustable thermal conductivity. Ease of disposal is particularly advantageous compared to other molding materials, since the molding material is harmless from an environmental point of view and corresponds to building rubble in this regard.
• the molding material - even if it contains iron granules to increase the thermal conductivity - can be taken back by the manufacturer and reused in a simple manner in the cement manufacturing process. It has also been found that the molding compositions can be removed from the molding easily and in particular considerably better than gypsum by sandblasting.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Mold Materials And Core Materials (AREA)
• Soil Conditioners And Soil-Stabilizing Materials (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)

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• 2001
  • 2001-04-04 DE DE2001164824 patent/DE10164824B4/de not_active Expired - Fee Related
• 2002
  • 2002-04-04 JP JP2002579150A patent/JP2004519334A/ja not_active Withdrawn
  • 2002-04-04 CZ CZ20031273A patent/CZ20031273A3/cs unknown
  • 2002-04-04 WO PCT/EP2002/003732 patent/WO2002081122A2/de not_active Application Discontinuation
  • 2002-04-04 US US10/471,222 patent/US20040083926A1/en not_active Abandoned
  • 2002-04-04 EP EP02745215A patent/EP1341626A2/de not_active Withdrawn
  • 2002-04-04 PL PL02365855A patent/PL365855A1/xx unknown
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  • 2002-04-04 HU HU0303305A patent/HUP0303305A3/hu unknown
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