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
  • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
• • 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
  • 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
• • 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
  • B22C1/186—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 contaming ammonium or metal silicates, silica sols
• • 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
  • B22C1/186—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 contaming ammonium or metal silicates, silica sols
  • B22C1/188—Alkali metal silicates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
• • 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

Definitions

• the invention relates to a multi-component system for obtaining molding material mixtures for the foundry industry, comprising one or more powdery oxidic boron compounds in combination with refractory molding raw materials, a water glass-based binder system and amorphous particulate silicon dioxide, in particular for the production of castings from aluminum, and a process for the production thereof of molds and cores from the molding material mixtures, which easily disintegrate after metal casting.
• Casting molds essentially consist of cores and molds, which represent the negative molds of the casting to be produced. These cores and molds consist of a refractory material, for example quartz sand, and a suitable binder, which gives the casting mold sufficient mechanical strength after removal from the mold.
• a refractory base material is used, which is coated with a suitable binder.
• the refractory mold raw material is preferably in a free-flowing form, so that it can be filled into a suitable hollow mold and compacted there.
• the binder creates a firm bond between the particles of the base material, so that the casting mold is given the required mechanical stability.
• Casting molds have to meet various requirements. During the casting process itself, they must first have sufficient strength and temperature resistance in order to be able to absorb the liquid metal into the cavity formed from one or more casting (partial) molds. After the solidification process begins, the mechanical stability of the casting is ensured by a solidified metal layer that forms along the walls of the casting mold. The material of the casting mold must now decompose under the influence of the heat given off by the metal in such a way that it loses its mechanical strength, that is to say the cohesion between individual particles of the refractory material is broken. Ideally, the mold disintegrates into fine sand that can be easily removed from the casting.
• inorganic binders Compared to organic binders, inorganic binders have the disadvantage that the casting molds produced therefrom have relatively low strengths. This is particularly evident immediately after the mold is removed from the tool. Good strengths at this point are particularly important for the production of complicated and / or thin-walled molded parts and their safe handling. The resistance to air humidity is also significantly reduced compared to organic binders.
• EP 1802409 B1 discloses that higher instant strengths and greater resistance to atmospheric moisture can be achieved by using a refractory molding base, a water glass-based binder and addition of particulate amorphous silicon dioxide. This addition ensures safe handling of even complicated molds.
• Inorganic binder systems have the disadvantage over organic binder systems that the coring behavior, i.e. the ability of the casting mold to disintegrate quickly (under mechanical stress) into a free-flowing form after casting, in purely inorganic casting molds (e.g. those that use water glass as a binder ) is often worse than in molds made with an organic binder.
• the invention was therefore based on the object of providing a multicomponent system for obtaining a molding material mixture for producing casting molds for metal processing, which particularly effectively improves the disintegration properties of the casting mold after metal casting and at the same time achieves a level of strength which is necessary in the automated production process is.
• casting molds with a complex geometry should be made possible, which can also include thin-walled sections, for example.
• the casting mold should also have a high storage stability and remain stable even at higher temperatures and air humidity.
• a key advantage is that the addition of powdered borates leads to significantly improved disintegration properties of the casting mold after metal casting. This advantage is associated with significantly lower costs for the production of a casting, in particular for castings which have a complex geometry with very small cavities from which the casting mold has to be removed.
• the multi-component system contains organic components with a proportion of up to a maximum of 0.49% by weight, in particular up to a maximum of 0.19% by weight, so that only very small amounts of emissions of CO 2 and other pyrolysis products are produced ,
• the use of the molding material mixture also contributes to the reduction of climate-damaging emissions from CO 2 and other organic pyrolysis products.
• Common and known materials can be used as the refractory mold base material for the production of casting molds. Suitable are, for example, quartz, zircon or chrome ore sand, olivine, vermiculite, bauxite, chamotte as well as artificial mold raw materials, in particular more than 50% by weight quartz sand based on the refractory mold raw material. It is not necessary to use only new sands. In terms of conserving resources and avoiding landfill costs, it is even advantageous to use the highest possible proportion of regenerated old sand, as can be obtained from used forms by recycling.
• a refractory molded raw material is understood to mean substances that have a high melting point (melting temperature).
• the melting point of the refractory mold base material is preferably greater than 600 ° C., preferably greater than 900 ° C., particularly preferably greater than 1200 ° C. and particularly preferably greater than 1500 ° C.
• the refractory molding base material preferably makes up greater than 80% by weight, in particular greater than 90% by weight, particularly preferably greater than 95% by weight, of the molding material mixture obtained from the multicomponent system according to the invention.
• regenerates can also be used, which can be obtained by washing and then drying shredded used molds. As a rule, the regenerates can make up at least about 70% by weight of the refractory base material, preferably at least about 80% by weight and particularly preferably greater than 90% by weight.
• the average diameter of the refractory mold raw materials is generally between 100 ⁇ m and 600 ⁇ m, preferably between 120 ⁇ m and 550 ⁇ m and particularly preferably between 150 ⁇ m and 500 ⁇ m.
• the particle size can e.g. determine by sieving according to DIN ISO 3310. Particle shapes with the greatest linear expansion to the smallest linear expansion (perpendicular to one another and in each case for all spatial directions) from 1: 1 to 1: 5 or 1: 1 to 1: 3, i.e. those that e.g. are not fibrous.
• the refractory molding base material preferably has a free-flowing state, in particular in order to be able to process the molding material mixture obtained from the multi-component system according to the invention in conventional core shooters.
• the water glasses contain dissolved alkali silicates and can be prepared by dissolving glass-like lithium, sodium and potassium silicates in water.
• the water glass preferably has a molar module SiO 2 / M 2 O (cumulative for different M's, ie in total) in the range from 1.6 to 4.0, in particular 2.0 to less than 3.5, where M is Lithium, sodium and / or potassium is available.
• a proportion of lithium ions in particular amorphous lithium silicates, lithium oxides and lithium hydroxide, or a ratio [Li 2 O] / [M 2 O] or [Li 2 O active ] / [M 2 O] as in FIG DE 102013106276 A1 described used.
• the water glasses have a solids content in the range from 25 to 65% by weight, preferably from 30 to 55% by weight, in particular from 30 to 50% by weight and very particularly preferably from 30 to 45% by weight.
• the solids content relates to the amount of SiO 2 and M 2 O contained in the water glass.
• the above values are based on a solids content of 35% by weight (see examples), regardless of which solids content is actually used.
• Powdery or particulate in each case means solid powder (including dusts) or also granules which can be poured and thus can also be sieved.
• the molding material mixture contains one or more powdery, oxidic boron compounds.
• the average particle size of the oxidic boron compounds is preferably less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.25 mm.
• the particle size of the oxidic boron compounds is preferably greater than 0.1 ⁇ m, preferably greater than 1 ⁇ m and particularly preferably greater than 5 ⁇ m.
• the average particle size can be determined using a sieve analysis.
• the screen residue on a screen with a mesh size of 1.00 mm is preferably less than 5% by weight, particularly preferably less than 2.0% by weight and particularly preferably less than 1.0% by weight.
• the screen residue is less than 20% by weight, preferably less than 15% by weight, particularly preferably less than 10% by weight and particularly preferably less, regardless of the information given above on a screen with a mesh size of 0.5 mm than 5% by weight.
• the sieve residue is preferably less than 50% by weight, preferably less than 25% by weight and particularly preferably less than 15% by weight, independently of the preceding information on a sieve with a mesh size of 0.25 mm.
• the screening residue is determined using the machine screening method described in DIN 66165 (Part 2), with a chain ring also being used as a screening aid.
• Oxidic boron compounds are understood to mean compounds in which the boron is in the oxidation state +3. Furthermore, the boron is coordinated with oxygen atoms (in the first coordination sphere, i.e. as the closest neighbor) - either 3 or 4 oxygen atoms.
• the oxidic boron compound is preferably selected from the group of borates, boric acids, boric anhydrides, borosilicates, borophosphates, borophosphosilicates and mixtures thereof, the oxidic boron compound preferably not containing any organic groups.
• Boric acids are understood to mean orthoboric acid (empirical formula H 3 BO 3 ) and meta or polyboric acids (empirical formula (HBO 2 ) n ).
• Orthoboric acid occurs, for example, in water vapor sources and as a mineral sassolin. It can also be produced from borates (eg borax) by acid hydrolysis.
• meta or polyboric acids can be produced from orthoboric acid by intermolocular condensation by heating.
• Boric anhydride (empirical formula B 2 O 3 ) can be produced by annealing boric acids. Boric anhydride is obtained as a mostly glassy, hygroscopic mass that can then be crushed.
• borates are derived from boric acids. They can be of both natural and synthetic origin. Borates are made up, among other things, of borate structural units in which the boron atom is surrounded by either 3 or 4 oxygen atoms as the closest neighbors. The individual structural units are mostly anionic and can either be isolated within a substance, for example in the case of orthoborate [BO 3 ] 3- , or linked together, such as Metaborate [BO 2 ] n- n , whose units are linked to form rings or chains can be - if you look at such a linked structure with corresponding BOB bonds, it is anionic in the overall view.
• orthoborate [BO 3 ] 3- or linked together, such as Metaborate [BO 2 ] n- n , whose units are linked to form rings or chains can be - if you look at such a linked structure with corresponding BOB bonds, it is anionic in the overall view.
• Borates which contain linked BOB units are preferably used. Orthoborates are suitable, but not preferred. Counterions to the anionic borate units are, for example, alkali and / or alkaline earth cations, but also, for example, zinc cations.
• M x O B 2 O 3
• M stands for the cation and x for divalent cations 1 and for monovalent cations 2 is.
• the lower limit is preferably greater than 1:20, preferably greater than 1:10 and particularly preferably greater than 1: 5.
• Borates in which trivalent cations serve as counterions to the anionic borate units are also suitable, for example aluminum cations in the case of aluminum borates.
• Natural borates are mostly hydrated, ie water is contained as structural water (as OH groups) and / or as water of crystallization (H 2 O molecules).
• Borax or borax decahydrate (di-sodium tetraborate decahydrate) can be regarded as an example, the empirical formula in the literature either as [Na (H 2 O) 4 ] 2 [B 4 O 5 (OH) 4 ] or for the sake of simplicity is given as Na 2 B 4 O 7 ⁇ 10H 2 O. Both hydrated and non-hydrated borates can be used, but the hydrated borates are preferred.
• Amorphous borates are understood to mean, for example, alkali or alkaline earth borate glasses.
• Perborates are not preferred due to their oxidative properties.
• fluoroborates is also conceivable, but due to the fluorine content not particularly preferred in aluminum casting. Since the use of ammonium borate with an alkaline water glass solution produces significant amounts of ammonia, which endangers the health of the people working in the foundry, such a substance is not preferred.
• Borosilicates, borophosphates and borophosphosilicates are understood to mean compounds which are usually amorphous / glass-like.
• the structure of these compounds contains not only neutral and / or anionic boron-oxygen coordinates (eg neutral BO 3 units or anionic BO 4 - units), but also neutral and / or anionic silicon-oxygen and / or phosphorus - Oxygen coordinations - the silicon is in the oxidation level +4 and the phosphorus is in the oxidation level +5.
• the coordinations can be linked to one another via bridging oxygen atoms, such as for Si-OB or POB.
• Metal oxides, in particular alkali and alkaline earth metal oxides, which serve as so-called network modifiers, can be built into the structure of the borosilicates, borophosphates and borophosphosilicates.
• the proportion of boron (calculated as B 2 O 3 ) in the borosilicates, borophosphates and borophosphosilicates is preferably greater than 15% by weight, preferably greater than 30% by weight, particularly preferably greater than 40% by weight, based on the total mass of the corresponding borosilicate, borophosphate or borophosphosilicate.
• boric acids from the group of borates, boric acids, boric anhydride, borosilicates, borophosphates and / or borophosphosilicates, however, the borates, borophosphates and borophosphosilicates, and in particular the alkali and alkaline earth borates, are clearly preferred.
• One reason for this selection is the strong hygroscopicity of the boric anhydride, which impairs its possible use as a powder additive when it is stored for a long time. In casting experiments with an aluminum melt, it was also shown that borates lead to significantly better casting surfaces than boric acids, which is why the latter are less preferred. Borates are particularly preferably used. Alkali and / or alkaline earth borates are particularly preferred, of which sodium borates and / or calcium borates are preferred.
• the proportion of the oxidic boron compound, based on the refractory mold raw material is preferably less than 1.0% by weight, preferably less than 0.4% by weight, particularly preferably less than 0.2% by weight, particularly preferably less than 0.1% by weight and particularly preferably less than 0.075% by weight.
• the lower limit is preferably greater than 0.002% by weight, preferably greater than 0.005% by weight, particularly preferably greater than 0.01% by weight and particularly preferably greater than 0.02% by weight.
• alkaline earth borates in particular calcium metaborate, increase the strength of molds and / or cores which have been cured with acidic gases such as CO 2 . It has also surprisingly been found that the moisture resistance of the molds and / or cores is improved by the addition of oxidic boron compounds according to the invention.
• the molding material mixture contains a portion of a particulate amorphous silicon dioxide in order to increase the strength level of the casting molds produced with such molding material mixtures.
• An increase in the strengths of the casting molds, in particular the increase in the hot strengths, can be advantageous in the automated production process. Synthetically produced amorphous silicon dioxide is particularly preferred.
• the particle size of the amorphous silicon dioxide is preferably less than 300 ⁇ m, preferably less than 200 ⁇ m, particularly preferably less than 100 ⁇ m and has, for example, an average primary particle size between 0.05 ⁇ m and 10 ⁇ m.
• the sieve residue of the particulate amorphous SiO 2 when passing through a sieve with a mesh size of 125 ⁇ m (120 mesh) is preferably not more than 10% by weight, particularly preferably not more than 5% by weight and very particularly preferably not more than 2% by weight. %. Independently of this, the sieve residue on a sieve with a mesh size of 63 ⁇ m is less than 10% by weight, preferably less than 8% by weight.
• the screening residue is determined using the machine screening method described in DIN 66165 (Part 2), with a chain ring also being used as a screening aid.
• the particulate amorphous silicon dioxide which is preferably used according to the present invention has a water content of less than 15% by weight, in particular less than 5% by weight and particularly preferably less than 1% by weight.
• the particulate amorphous SiO 2 is used as a powder (including dusts).
• Both synthetically produced and naturally occurring silicas can be used as amorphous SiO 2 .
• the latter are out, for example DE 102007045649 are known, but are not preferred since they generally contain not insignificant crystalline components and are therefore classified as carcinogenic.
• Synthetic is not understood to mean naturally occurring amorphous SiO 2 , that is to say the production thereof comprises a deliberately carried out chemical reaction, as is caused by a human, For example, the production of silica sols by ion exchange processes from alkali silicate solutions, the precipitation from alkali silicate solutions, the flame hydrolysis of silicon tetrachloride, the reduction of quartz sand with coke in an electric arc furnace in the production of ferrosilicon and silicon.
• the amorphous SiO 2 produced by the latter two processes is also referred to as pyrogenic SiO 2 .
• amorphous silicon dioxide means only precipitated silica (CAS No. 112926-00-8) and flame-hydrolytically produced SiO 2 (pyrogenic silica, fumed silica, CAS No. 112945-52-5), while that in the case of ferrosilicon or Silicon production product is only referred to as amorphous silicon dioxide (Silica Fume, Microsilica, CAS No. 69012-64-12).
• the product formed in the manufacture of ferrosilicon or silicon is also understood to be amorphous SiO 2 .
• Precipitated silicas and pyrogenic, ie flame hydrolytic or arc-produced silicon dioxide are preferably used.
• Amorphous silicon dioxide produced by thermal decomposition of ZrSiO 4 (described in US Pat DE 102012020509 ) and SiO 2 produced by oxidation of metallic Si using an oxygen-containing gas (described in US Pat DE 102012020510 ).
• quartz glass powder mainly amorphous silicon dioxide, which was produced from crystalline quartz by melting and rapid cooling again, so that the particles are spherical and not splintered (described in US Pat DE 102012020511 ).
• the average primary particle size of the particulate amorphous silicon dioxide can be between 0.05 ⁇ m and 10 ⁇ m, in particular between 0.1 ⁇ m and 5 ⁇ m, particularly preferably between 0.1 ⁇ m and 2 ⁇ m.
• the primary particle size can be determined, for example, with the aid of dynamic light scattering (for example Horiba LA 950) and checked by scanning electron microscope images (SEM images with, for example, Nova Nano-SEM 230 from FEI). Furthermore, with the help of the SEM images, details of the primary particle shape down to the order of 0.01 ⁇ m could be made visible.
• the silicon dioxide samples were dispersed in distilled water and then applied to an aluminum holder stuck with copper tape before the water was evaporated.
• the specific surface area of the particulate amorphous silicon dioxide was determined using gas adsorption measurements (BET method) in accordance with DIN 66131.
• the specific surface area of the particulate amorphous SiO 2 is between 1 and 200 m 2 / g, in particular between 1 and 50 m 2 / g, particularly preferably between 1 and 30 m 2 / g. If necessary. the products can also be mixed, for example to obtain specific mixtures with specific particle size distributions.
• the purity of the amorphous SiO 2 can vary widely. Types with a content of at least 85% by weight of silicon dioxide have proven suitable, preferably of at least 90% by weight and particularly preferably of at least 95% by weight. Depending on the application and the desired level of strength, between 0.1% and 2% by weight of the particulate amorphous SiO 2 are used, preferably between 0.1% and 1.8%, particularly preferably between 0.1%. % and 1.5% by weight, based in each case on the basic molding material.
• the ratio of water glass binder to particulate amorphous silicon dioxide can be varied within wide limits. This offers the advantage that the initial strengths of the cores, i.e. improve the strength immediately after removal from the tool without significantly affecting the final strength. This is of particular interest in light metal casting. On the one hand, high initial strengths are desired so that the cores can be easily transported after assembly or assembled into whole core packages; on the other hand, the final strengths should not be too high to avoid difficulties in the core disintegration after casting, i.e. the base material of the mold should be able to be easily removed from the cavities of the mold after casting.
• the amorphous SiO 2 is preferably present in a proportion of 1 to 80% by weight, preferably 2 to 60% by weight, particularly preferably 3 to 55% by weight. % and particularly preferably between 4 to 50% by weight. Or independently of this, based on the ratio of solids content of the water glass (based on the oxides, ie total mass of alkali metal oxide and silicon dioxide) to amorphous SiO 2, from 10: 1 to 1: 1.2 (parts by weight) is preferred.
• the amorphous SiO 2 is preferably added to the refractory before the binder is added.
• barium sulfate can be added to the molding material mixture in order to further improve the surface of the casting, in particular made of aluminum.
• the barium sulfate can be synthetically produced as well as natural barium sulfate, ie added in the form of minerals that contain barium sulfate, such as heavy spar or barite. This, as well as other features of the suitable barium sulfate and the molding mixture produced with it, are described in the DE 102012104934 described in more detail and their disclosure content is thus made by reference to the disclosure of the present property right.
• the barium sulfate is preferably used in an amount of 0.02 to 5.0% by weight, particularly preferably 0.05 to 3.0% by weight, particularly preferably 0.1 to 2.0% by weight or 0.3 to 0 , 99% by weight, based in each case on the entire molding mixture, added.
• the additive component (A) as in the DE 102012113073 or the DE 102012113074 described in more detail.
• Such additives can be used to obtain castings, in particular made of iron or steel, with a very high surface quality after the metal casting, so that after the removal of the casting mold, little or no post-processing of the surface of the casting is required.
• the molding material mixture can comprise a phosphorus-containing compound .
• a phosphorus-containing compound preferably inorganic phosphorus compounds in which the phosphorus is preferably in the +5 oxidation state.
• the phosphorus-containing compound is preferably in the form of a phosphate or phosphorus oxide.
• the phosphate can be present as an alkali metal or as an alkaline earth metal phosphate, alkali metal phosphates and in particular the sodium salts being particularly preferred.
• Both orthophosphates and polyphosphates, pyrophophates or metaphosphates can be used as phosphates.
• the phosphates can be prepared, for example, by neutralizing the corresponding acids with an appropriate base, for example an alkali metal base, such as NaOH, or optionally also an alkaline earth metal base, it not necessarily being necessary for all the negative charges of the phosphate to be saturated by metal ions.
• Both the metal phosphates and the metal hydrogen phosphates and the metal dihydrogen phosphates can be used, such as Na 3 PO 4 , Na 2 HPO 4 , and NaH 2 PO 4 .
• the anhydrous phosphates and hydrates of the phosphates can also be used.
• the phosphates can be introduced into the molding material mixture both in crystalline and in amorphous form.
• Polyphosphates are understood to mean, in particular, linear phosphates which comprise more than one phosphorus atom, the phosphorus atoms in each case being connected to one another via oxygen bridges.
• Polyphosphates are obtained by the condensation of orthophosphate ions with elimination of water, so that a linear chain of PO 4 tetrahedra is obtained, which are each connected via corners.
• Polyphosphates have the general formula (O (PO 3 ) n) (n + 2) - , where n corresponds to the chain length.
• a polyphosphate can comprise up to several hundred PO 4 tetrahedra. However, polyphosphates with shorter chain lengths are preferably used.
• N preferably has values from 2 to 100, particularly preferably 5 to 50.
• Highly condensed polyphosphates can also be used, ie polyphosphates in which the PO 4 tetrahedra are connected to one another via more than two corners and therefore show polymerization in two or three dimensions.
• Metaphosphates are understood to be cyclic structures which are made up of PO 4 tetrahedra which are connected to one another via corners. Metaphosphates have the general formula ((PO 3 ) n) n- , where n is at least 3. N preferably has values from 3 to 10.
• Both individual phosphates and mixtures of different phosphates and / or phosphorus oxides can be used.
• the preferred proportion of the phosphorus-containing compound, based on the refractory base material, is between 0.05 and 1.0% by weight.
• the proportion of the phosphorus-containing compound is preferably chosen to be between 0.1 and 0.5% by weight.
• the phosphorus-containing, inorganic compound preferably contains between 40 and 90% by weight, particularly preferably between 50 and 80% by weight, phosphorus, calculated as P 2 O 5 .
• the phosphorus-containing compound can in itself be added to the molding material mixture in solid or dissolved form.
• the phosphorus-containing compound is preferably added to the molding material mixture as a solid.
• the molding material mixture according to the invention contains a proportion of platelet-shaped lubricants, in particular graphite or MoS 2 .
• the amount of the platelet-shaped lubricant, in particular graphite, added is preferably 0.05 to 1% by weight, particularly preferably 0.05 to 0.5% by weight, based on the basic molding material.
• surface-active substances in particular surfactants
• surfactants can also be used which improve the flowability of the molding material mixture .
• Anionic surfactants are preferably used for the molding material mixture.
• Surfactants with sulfuric acid or sulfonic acid groups should be mentioned here in particular.
• the pure surface-active substance, in particular the surfactant, based on the weight of the refractory base material is preferably present in the molding material mixture in a proportion of 0.001 to 1% by weight, particularly preferably 0.01 to 0.2% by weight.
• the molding material mixture is an intensive mixture of at least the above-mentioned components of the multi-component system.
• the particles of the refractory molding material are preferably coated with a layer of the binder. By evaporating the water present in the binder (approx. 40-70% by weight, based on the weight of the binder), a firm cohesion can then be achieved between the particles of the refractory base material.
• the casting molds produced with the molding material mixture surprisingly show very good disintegration after casting, in particular when casting aluminum.
• the molding material mixture can be used to produce casting molds which also show very good disintegration when cast iron, so that the molding material mixture can be poured out again from narrow and angled sections of the casting mold after the casting.
• the use of the moldings produced from the molding material mixture is therefore not only restricted to light metal casting and / or non-ferrous metal casting.
• the casting molds are generally suitable for casting metals, such as non-ferrous metals or ferrous metals.
• the molding material mixture is particularly preferably suitable for the casting of aluminum.
• the procedure is generally such that the refractory molding raw material (component (F)) is initially introduced and then the binder or component (B) and the additive or component (A) are stirred is added.
• component (F) refractory molding raw material
• component (B) binder or component
• additive or component (A) are stirred is added.
• the additives described above can be added in any form to the molding material mixture. They can be added individually or as a mixture.
• the binder is provided as a two-component system, a first liquid component containing the water glass and possibly a surfactant (see above) (components (B)) and a second but solid component containing one or more oxidic boron Compounds and the particulate silicon dioxide (components (A)) and all other solid additives mentioned above, with the exception of the basic molding materials, in particular the particulate amorphous silicon dioxide and possibly a phosphate and possibly a preferably platelet-shaped lubricant and possibly barium sulfate or possibly other components such as described include.
• the refractory molding raw material is placed in a mixer and then preferably the solid component (s) of the binder is first added and mixed with the refractory molding material.
• the mixing time is chosen so that the refractory base material and solid binder component are thoroughly mixed.
• the mixing time depends on the amount of the molding material mixture to be produced and on the mixing unit used.
• the mixing time is preferably chosen between 1 and 5 minutes.
• the liquid component of the binder is then added, preferably with further movement of the mixture, and the mixture is then mixed further until a uniform layer of the binder has formed on the grains of the refractory base molding material.
• the mixing time depends on the amount of molding material mixture to be produced and on the mixing unit used.
• the duration for the mixing process is preferably chosen between 1 and 5 minutes.
• a liquid component is understood to mean both a mixture of different liquid components and the entirety of all liquid individual components, the latter also being able to be added individually.
• a solid component is understood to mean both the mixture of individual or all of the solid components described above and the entirety of all solid individual components, the latter being able to be added to the molding material mixture together or in succession.
• the liquid component of the binder can first be added to the refractory base material and only then can the solid component be added to the mixture.
• 0.05 to 0.3% by weight of water, based on the weight of the mold base is first added to the refractory mold base and only then are the solid and liquid components of the binder added.
• a surprising positive effect on the processing time of the molding material mixture can be achieved.
• the inventors believe that the dehydrating effect of the solid components of the binder is reduced in this way and the curing process is thereby delayed.
• the molding material mixture is then brought into the desired shape.
• the usual methods for shaping are used.
• the molding material mixture can be shot into the molding tool by means of a core shooting machine with the aid of compressed air.
• the molding material mixture is then cured, it being possible to use all processes which are known for binders based on water glass, for example hot curing, gassing with CO 2 or air or a combination of both, and curing by means of liquid or solid catalysts. Hot curing is preferred.
• the heating can take place, for example, in a mold which preferably has a temperature of 100 to 300 ° C., particularly preferably a temperature of 120 to 250 ° C. It is possible to fully harden the casting mold in the mold. However, it is also possible to harden the casting mold only in its edge region, so that it has sufficient strength to be able to be removed from the molding tool.
• the mold can then be fully cured by removing more water from it. This can be done in an oven, for example. The water can also be removed, for example, by evaporating the water under reduced pressure.
• the hardening of the casting molds can be accelerated by blowing heated air into the mold.
• the water contained in the binder is rapidly removed, as a result of which the casting mold is solidified in periods of time suitable for industrial use.
• the temperature of the air blown in is preferably 100 ° C. to 180 ° C., particularly preferably 120 ° C. to 150 ° C.
• the flow rate of the heated air is preferably set so that the casting mold is cured in time periods suitable for industrial use.
• the time periods depend on the size of the molds produced. The aim is to cure in a period of less than 5 minutes, preferably less than 2 minutes. For very large molds, however, longer periods of time may be required.
• the water can also be removed from the molding material mixture in such a way that the heating of the molding material mixture is effected or assisted by irradiation with microwaves. It would be conceivable, for example, to mix the basic molding material with the solid, powdery component (s), to apply this mixture in layers on a surface and to print the individual layers with the aid of a liquid binder component, in particular with the aid of water glass, the layer-by-layer application of the Solid mixture, one printing process with the help of the liquid binder follows.
• the entire mixture can be heated in a microwave oven.
• the methods according to the invention are suitable per se for the production of all casting molds customary for metal casting, that is to say for example of cores and molds. Casting molds which comprise very thin-walled sections can also be produced particularly advantageously.
• the casting molds produced from the molding material mixture or with the method according to the invention have a high strength immediately after production, without the strength of the casting molds being so high after curing that difficulties arise after the production of the casting when removing the casting mold. Furthermore, these molds have a high stability with increased air humidity, i.e. the casting molds can surprisingly be stored without problems for a long time. As an advantage, the casting mold has a very high stability under mechanical stress, so that thin-walled sections of the casting mold can also be realized without being deformed by the metallostatic pressure during the casting process. Another object of the invention is therefore a casting mold, which was obtained by the inventive method described above.
• Examples 1.01 and 1.02 illustrate that the addition of amorphous SiO 2 can achieve a significantly improved strength level (according to EP 1802409 B1 and DE 102012020509 A1 ).
• a comparison of Examples 1.02 to 1.14 shows that the strength level is not noticeably influenced by the addition of powdery oxidic boron compounds.
• Examples 1.06 and 1.11 to 1.14 show a slight deterioration in the strength levels with an increasing proportion of the additive according to the invention. However, the effect is very weak.
• Examples 1.01 and 1.02 show that adding a particulate, amorphous silicon dioxide to the molding material mixture significantly deteriorates the disintegration behavior of the molds produced with it.
• a comparison of Examples 1.02 to 1.09 clearly shows that the use of powdery oxidic boron compounds leads to significantly improved disintegration properties of the forms bonded with water glass.
• a comparison of Examples 1.07 and 1.10 shows that it makes a difference whether the borate (in this case) was pre-dissolved in the binder before use in the molding mixture or whether the borate was added to the molding mixture as a solid powder. Such an effect is surprising.
• Examples 1.06 and 1.11 to 1.14 illustrate that the disintegration behavior can be increased significantly with an increasing proportion of the additive according to the invention. It also becomes clear that even small additions are sufficient to significantly increase the disintegration ability of the hardened molding material mixture after thermal stress.

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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)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 2013
  • 2013-10-22 DE DE201310111626 patent/DE102013111626A1/de not_active Withdrawn
• 2014
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