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
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
  • B22C1/185—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents containing phosphates, phosphoric acids or its derivatives
• • 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
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/167—Mixtures of inorganic and organic binding agents

Definitions

• the invention relates to a water-dispersible casting mold, in particular a casting core, for producing castings, which comprises a water-insoluble, particulate material, in particular molding sand, a binder which has at least one condensing phosphate as a first binder component.
• the invention further relates to a method for producing such a casting mold, in which a water-insoluble, particulate material, in particular molding sand, is mixed with a binder, which has at least one condensed phosphate as a first binder component, with the addition of water, the mixture is shaped and at least part of the added free water is removed.
• Casting cores of the aforementioned composition are known. They are usually manufactured in core boxes using core shooters for series production.
• the core boxes are provided with corresponding mold cavities, into which insertion openings open, via which a water-insoluble, particulate material provided with a binder is injected into the mold cavities using compressed air from a so-called shooting head.
• the particulate material is generally molding sand, such as silica, zircon, chromite or the like, which can be solidified by the binder.
• the molding sand should have good flow properties.
• Liquid synthetic resins and additional additives were conventionally used as binders for the molding sand.
• synthetic resin binders formation of vapors harmful to health during manufacture, partial burning of the binder during casting, elaborate coring, disposal of the core waste sand - the use of at least to a certain extent water-soluble inorganic binders has been proposed.
• DE 195 49 469 A1 describes a casting core on the basis of molding sand consolidated by means of a water-soluble binder, phosphoric acid or condensed phosphates, such as sodium polyphosphate and sodium hexametaphosphate, being provided as binders.
• WO 92/06808 A1 shows a casting core which, in order to solidify the molding sand, has a binder made from a water-soluble phosphate glass containing polyphosphate chains or from a water-soluble borate glass.
• the molding sand is mixed with the binder with the addition of water, the mixture is poured into the core box and the excess water is expelled from the casting mold by heating.
• the known casting cores are water-dispersible after pouring, ie they dissolve again after immersion in water, as a result of which there is no need for expensive coring.
• Another advantage of casting cores of this type is that no environmentally harmful substances are released either when the casting cores are produced and when the castings are poured off, or when the castings are cored.
• the binders used also have an inorganic chemistry, so that burning of the binder during the casting process is reliably avoided.
• binders of the aforementioned type give the casting core insufficient bending strength for many applications.
• the casting core can deform or even break during removal or storage after molding, when it is inserted into the casting mold or during the casting process, so that the castings obtained can be defective and result in rejects.
• casting cores of this type often have insufficient abrasion resistance, as a result of which grains of sand on the surface of the casting core become detached during casting and lead to a rough surface and / or sand contamination of the casting.
• the binder when using a binder based on pure condensed phosphates, the binder has an insufficient temperature resistance for alloys with a relatively high melting point, so that the production of castings from such alloys is not possible.
• the occurrence of the disadvantages mentioned cannot be effectively countered in particular by varying the process parameters during the production of the casting core, such as the composition of the casting core, the drying temperature, the residual water content, etc.
• the invention is based on the object of imparting increased bending and abrasion resistance to a casting mold, in particular a casting core, with a first binder component based on condensed phosphates and increasing the temperature resistance, while maintaining acceptable cycle times in core production and to release no or only small amounts of environmentally harmful substances Zen. It is also directed to the manufacture of such a mold.
• this object is achieved in a casting mold of the type mentioned at the outset in that the binder has at least one polyamine as a second binder component.
• both the bending and the abrasion resistance of a casting mold or a casting core made of a water-insoluble, particulate material and a binder based on condensed phosphates can be significantly increased without the addition of only small amounts of polyamines to impair the water dispersibility of the poured casting core.
• bending strengths of more than 150 N / cm 2 can be achieved, which reliably prevent failure of the casting core and the resulting defective castings.
• the abrasion resistance of the casting mold or the casting core is improved in such a way that damage to the casting by sand particles is practically impossible.
• polyamines mean saturated or unsaturated, open-chain or cyclic organic compounds with several primary, secondary and / or tertiary amino groups, in particular in liquid form.
• any known molding sands for example silica, zircon, chromite sands or the like, come as water-insoluble, particulate materials, or other temperature-resistant materials, such as aluminum oxide, aluminum silicate, quartz glass, etc., in a particulate form, are also considered.
• further binder components can also be provided.
• the polyamm is selected from the group of polymeric polyams.
• the polyethyleneimines, ie branched polymers with primary, secondary and tertiary amino groups, polyvinylam (vinylamm polymers) and / or their copolymers have proven to be particularly advantageous.
• the bending strength of a casting core consisting of a molding sand and a binder based on sodium polyphosphate can be almost doubled by adding 0.1% by weight of polyvinylamine based on the molding sand.
• the polymeric polyamides can in particular be provided with a molar mass between about 400 g / mol and about 10 7 g / mol.
• the chemical formulas for Polyammylamm (I) and Polyethyleneimm (II) are shown below as examples:
• the polyamm has a nitrogen content (N content) of between 1 and 35 mass% N / polymer unit, preferably between 10 and 33 mass% N / polymer unit, in particular between 20 and 33 mass% N / polymer unit.
• N content nitrogen content
• the casting core of more than 200 N / cm 2 could be obtained, in particular with polymeric polyamines with a relatively high amino group density in the range of 30% by mass of N / polymer, for example with polyvinylamene, which had a nitrogen content of up to 33% by mass of N / Have polymer units and can be achieved in particular with polyvinyl amines with a high proportion of free amino groups.
• the amount of the poly ms provided as the second binder component is preferably between 0.001 and 1% by mass, in particular between 0.005 and 0.5% by mass, of polyamm, based on the particulate material. It depends primarily on the type of polyamm, the amount of the polyamm generally being able to be lower, the higher the free amino group density of the polyamm, in order to improve the binder properties with regard to flexural strength and abrasion resistance.
• the first binder component based on condensed phosphates can contain or consist entirely of polyphosphates, preferably alkali metal polyphosphates, especially sodium polyphosphate, and / or metal phosphates, preferably alkali metal metaphosphates, especially sodium metaphosphates, eg sodium hexametaphosphate. Furthermore, it can be provided that the first binder component contains or consists entirely of water-soluble phosphate glass containing poly and / or metaphosphate chains, the phosphate glass preferably between 58 and 75% by mass of phosphorus pentoxide (P 2 0 5 ) and between 25 and 42% by mass of alkali metal oxide, in particular sodium oxide (Na 2 0).
• the binders mentioned are known as such and ensure that the casting core is dissolved quickly and without lumps when it is immersed in water with the finished casting. Another advantage of these binders is that they can be egg-coated even with a relatively low moisture content. lead optimal mixing with the molding sand and thereby ensure a sufficient initial strength of the casting core or the casting mold, so that only very short drying times are required and thus very short cycle times for production are possible.
• the amount of the first binder component based on condensed phosphates is advantageously between 0.25 and 25% by mass, preferably between 0.5 and 10% by mass, based on the water-insoluble, particulate material.
• the invention is characterized by at least one additive, preferably in the form of sulfates, carbonates and / or nitrates from the group of alkali metals and / or alkaline earth metals, such as alkali metal carbonates, in particular sodium carbonate (Na 2 CO 3 ).
• alkali metal carbonates in particular sodium carbonate (Na 2 CO 3 ).
• alkali metal carbonates increases the dispersibility of the casting core in water and thus facilitates the coring of the finished casting.
• a proportion of alkali metal carbonates increases the dispersibility of the casting core in water and thus facilitates the coring of the finished casting.
• between 20 and 90% by mass, in particular between 30 and 85% by mass, of alkali metal carbonate based on the first binder component based on condensed phosphates is expediently provided.
• the molding material mixture for the casting mold or the casting core generally also contains a moisture content of between 0.01 and 35% by mass, in particular between 0.1 and 5% by mass. After drying, the moisture content of the casting mold or the casting core is generally about 0.01% by mass or less.
• the method according to the invention is characterized in that a second binder component based on at least one polyamm is added.
• a second binder component based on at least one polyamm is added.
• the types described above are preferably used on the first and second binder components and, if appropriate, on additives in the amount described above.
• a preferred embodiment provides that the second binder component in liquid form is brought into contact with the particulate material and then the first binder component is added in dry form, the
• the second binder component can be present in the liquid phase or as a particularly aqueous solution. If an additive such as alkali metal carbonates is desired, this can be dissolved in the water added to the mixture and the solution added to the mixture.
• Binder component is added, and here too, if desired, the additive can be dissolved in the solution before adding the solution.
• the binder and optionally the additive can be dissolved in water and for the solution to be brought into contact with the particulate material. In any case, the most homogeneous possible distribution of the water-soluble binder and, if appropriate, of the additive with the particulate material should be achieved.
• the casting mold or the casting core is shaped e.g. except one
• Residual moisture of about 0.01% by mass, based on the particulate material is dried.
• the amount of water used is preferably kept as low as possible in order to ensure short cycle times during production, which in turn largely depend on the drying time.
• the bending strength of the casting mold or the casting core can be influenced within certain limits by the water content and the water content ensures the required flowability of the mixture when it is shot into the mold box. It has proven to be advantageous to add between 0.1 and 5% by mass, in particular between about 0.1 and 3% by mass, of water, based on the particulate material, in order to provide the molding material mixture with short flow times and satisfactory flowability to care.
• the mixture is first dried to a predetermined residual moisture, then water is again added to the mixture and the mixture is shaped, at least part of the free water added being removed again.
• the mixture can preferably first be dried to a predetermined residual moisture content of approximately 0.1% by mass.
• the cycle times for producing the casting mold or the casting core according to the invention can be further reduced by reducing the total proportion of the water added.
• the molding material mixture which has been dried to a predetermined residual moisture content can be stored well and is easy to process by adding water again.
• the casting mold or the casting core is expediently dried to a residual moisture content of about 0.01% by mass, based on the particulate material.
• FIG. 1 shows a diagram to illustrate the bending strength ⁇ of a casting core with a sodium polyphosphate binder without the addition of polyamines (A) and with
• FIG. 2 shows a comparative diagram to illustrate the bending strength ⁇ of a casting core with a binder exclusively made of polyamine at different service lives t;
• FIG. 3 shows a diagram to illustrate the bending strength ⁇ of a casting core of the composition (B) according to FIG. 1, which additionally contains an additive in the form of sodium carbonate, at different service lives t;
• Fig. 4 shows a diagram to illustrate the bending strength ⁇ of a casting core of the composition according to FIG. 3 after different storage times ti of the material mixture and after different standing times t 2 ;
• Fig. 5 is a diagram illustrating the bending strength ⁇ each of a casting core with a binder made of sodium polyphosphate and different polyamines with different ammo group density (A, B, C, D, E) at different service lives t and
• FIG. 6 shows a diagram to illustrate the bending strength ⁇ of each casting core with the compositions (A, B, C, D, E) according to FIG. 5 after different storage times ti of the molding material mixture and after different standing times t 2 .
• Composition A A:
• Composition B is a composition of Composition B:
• binder component 1 based on the molding sand
• binder component 2 0.1% by mass of liquid polyamine (binder component 2), based on the molding sand, - 1.4% by mass of moisture based on the molding sand.
• the binder was mixed dry with the molding sand.
• the second binder component in homogeneous form was mixed homogeneously with the molding sand and the first binder component was then added to the mixture dry.
• the molding material mixture was in each case shot into a core box and dried to a residual moisture of about 0.01% by mass.
• the casting cores produced in this way were examined for their bending strength ⁇ after different service lives t.
• Casting cores were produced in the manner described above as a comparative experiment, with only polyvinylamine being used as the binder. The casting cores obtained were then examined for their bending strength ⁇ after different service lives t.
• Composition B according to Example 1 (molding sand, 2% by weight of sodium polyphosphate (binder component 1), 0.1% by weight of liquid polyvinylamine (binder component 2) and 1.4% by weight of moisture, based in each case on the molding sand), became
• the example shows that the bending strength of the casting core is not affected by the addition of Na 2 C0 3 .
• the addition of Na 2 CO 3 gives the casting core a considerably better temperature resistance, so that it is suitable, for example, for the production of aluminum castings with a casting temperature of over 800 ° C, with deformations of the casting core being reliably and reliably avoided during the casting process.
• the addition of Na 2 C0 3 increases the water solubility of the casting core, so that the coring of the finished casting is facilitated.
• molding sand 2% by mass of sodium polyphosphate (binder component 1) and 0.1% by mass of liquid polyvinylamine (binder component 2), each based on the molding sand, and sodium carbonate (Na 2 C0 3 ) homogeneously mixed with approx. 1.4 mass% water based on the molding sand.
• the molding material mixture formed in this way was shot into a core box after various storage times ti of 0, 1, 2 and 3 h and dried to a residual moisture content of about 0.01% by mass, based on the molding sand.
• the example shows that the molding material mixture has a good shelf life and can be dried several hours after the mixing process to form the casting core.
• polyethylenimines A, B
• various polyethylenimines A, B
• water-modified polyethylenimines with a molar mass of about 2000 g / mol (A) or 750,000 g / mol (B).
• polyvinylamines (C, D, E) with a molecular weight of about 400,000 g / mol were used, which differ in the proportion of free amino groups, which in turn corresponds to the degree of hydrolysis.
• the polyvinylamine (C) has the highest hydrolysis segrad, the polyvinylamine (E) has a lower degree of hydrolysis and the polyvinylamine (D) the lowest degree of hydrolysis of the polyvinylamines (C, D, E).
• the casting cores were produced by the process described in Example 1. The casting cores produced in this way were then examined for their bending strength ⁇ after different service lives t.
• the molding material mixtures were shot into a core box after various storage times ti of 0, 1, 2 and 3 h and dried.
• the best values for the bending strength of the casting core were obtained after a storage time ti of the molding material mixture of one hour, where the mixture could be processed immediately or at least three hours after the individual component had been mixed, but only a slightly poorer flexural strength, so that good storage stability could also be determined here.
• the most suitable has proven to be the polyamine (C) with a high proportion of free amino groups.
• Casting core is not affected.
• the mixture has good storability and water solubility and consequently a perfect processability.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Mold Materials And Core Materials (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• External Artificial Organs (AREA)

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• 2002
  • 2002-06-15 DE DE10226817A patent/DE10226817C1/de not_active Expired - Fee Related
• 2003
  • 2003-05-08 DE DE50300900T patent/DE50300900D1/de not_active Expired - Lifetime
  • 2003-05-08 MX MXPA04001282A patent/MXPA04001282A/es active IP Right Grant
  • 2003-05-08 EP EP03740129A patent/EP1417060B1/fr not_active Expired - Lifetime
  • 2003-05-08 WO PCT/EP2003/004802 patent/WO2003106071A1/fr not_active Ceased
  • 2003-05-08 AT AT03740129T patent/ATE301013T1/de active
  • 2003-05-08 US US10/486,656 patent/US20040238156A1/en not_active Abandoned
  • 2003-05-08 AU AU2003276882A patent/AU2003276882A1/en not_active Abandoned

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