Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
• • 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
  • B22C1/14—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 for separating the pattern from the mould

Definitions

• the present invention relates to a size for the production of mold coatings by application to inorganic or organic bonded moldings in lost molds or on cores for iron and steel casting.
• Casting in a lost form is a common process for making end-to-end components. After casting, the mold is destroyed and the casting is removed.
• Shapes are negatives, they contain the emptying cavity, which results in the casting to be produced.
• the inner contours of the future casting are formed by cores.
• the cavity is shaped into the molding material by means of a model of the casting to be produced.
• Inner contours are represented by cores formed in a separate core box.
• refractory granular materials such as washed
• classified quartz sand are used as molding materials.
• Other materials include zirconium, chromite sands, chamottes, olivine sands, feldspathic sands and andalusite sands.
• the molding materials are bound with inorganic or organic binders.
• bentonites or other clays are used as inorganic binders.
• the molded materials are compacted to increase the strength.
• corresponding molding materials are also gassed for curing.
• the curing of the binder can be done by heating the molding material and expelling a solvent, which then causes hardening.
• the surfaces of the molds and cores are coated with a size.
• Ready-to-use sizes for coating molds and cores are suspensions of fine-grained, refractory to highly refractory inorganic materials in a carrier liquid, e.g. Water or a solvent.
• the sizing is applied by a suitable application method, for example spraying, dipping, flooding or brushing on the inner contour of the casting mold or on the core and dried there, so that a sizing coat (sizing film) is formed.
• the drying of the size coat may be accomplished by the application of heat or radiant energy, e.g. by microwave radiation, or by drying in the room air done. In the case of solvent-containing sizing, the drying can also be carried out by burning off the solvent.
• the size coatings should u.a. fulfill the following functions:
• the aforementioned functions 1 to 3 are usually fulfilled by combinations of various suitable refractory materials.
• fireproof materials are here and
• Resistant to molten iron, materials and minerals that can withstand the pouring heat of molten steel in the short term are regarded as highly refractory.
• refractory material for example, mineral oxides such as corundum, magnesite, quartz, chromite and olivine, furthermore silicates such as zirconium silicate, chamotte, andalusites, pyrophyllite, kaolinite, mica and other clay minerals are used individually or in combination. Graphite and coke are also used.
• the refractories are in a carrier liquid suspended. Solvents such as ethanol or isopropanol can serve as the carrier liquid, but today water is usually preferred as the carrier liquid.
• suspending agents e.g. water swellable clays such as smectites, attapulgites or sepiolites or swellable organic thickeners such as e.g. CeIIu losederivate or polysaccharide.
• a size includes a binder to fix the refractories on the molding material.
• synthetic resins or synthetic resin dispersions are used here, e.g. Polyvinyl alcohol, polyacrylates, polyvinyl acetates and corresponding copolymers. Natural resins, dextrins, starches and peptides can also be used as binders.
• the aforementioned swellable clays can also take over the functions of the binder.
• Finishes may contain further additives, in the case of aqueous sizes in particular preservatives and rheologically active additives and adjusters.
• Rheologically active additives and / or adjusting agents are used to adjust the flowability of the size desired for processing.
• wetting agents can also be used to achieve better wetting of the molding material.
• ionic and nonionic wetting agents For example, dioctylsulfosuccinates are used as ionic wetting agents and alkynediols or ethoxylated alkynediols are used as nonionic wetting agents.
• gas error is e.g. from Gy. Nandori and J. PaI. Miskoloc and K. Peukert in Foundry 83 (1996) 16 describe. These are gas bubbles that occur associated with slag jobs.
• the cause of such gas slag faults are "exogenous,” i.e., from the molding material and mold cavity, and "endogenous,” i. to look at the gases coming from the melt. These gases partially react with the melt, resulting in oxide-rich slags. These slags together with the remaining gases form gas faults.
• An influencing factor for the formation of these gas defects is the gas permeability of the molding material coated with the size coat.
• the sizing coating may peel off the core or the mold if a high gas pressure due to pyrolysis of the molding material binder builds up in the core and the sizing presents a high resistance to this pressure due to a low gas permeability. If the gas pressure exceeds the adhesive forces of the sizing coating on the core or the mold, the sizing will be abated. Casting errors caused by melting in the melt size particles are the result.
• the patent application WO 2007/025769 describes sizing agents (where they are also referred to as molding compositions together with molding material mixtures) which contain borosilicate glass in an amount of at least 0.001%, preferably at least 0.005% by weight, in particular at least 0.01% by weight contained on the solids content of the size.
• the proportion of borosilicate glass is preferably less than 5% by weight, more preferably less than 2% by weight and most preferably within a range of 0.01 to 1% by weight, in each case based on the solids content of the size.
• borosilicate glass in the form of hollow microspheres ie hollow beads having a diameter in the order of preferably 5 to 500 .mu.m, more preferably 10 to 250 .mu.m, whose shell is constructed of borosilicate glass, is used. It is believed that the borosilicate glass melts under the influence of the temperature of the liquid metal, thereby releasing voids which can compensate for the volume expansion of the molding material caused by the casting heat.
• the softening point of the borosilicate glass in the range of less than 1500 0 C, more preferably in the range of 500 to 1000 0 C is set. When using these sizes, flaking off the size coat under the influence of the liquid metal is expected to occur only extremely rarely. In addition, it was found that no leaf ribs form and a smooth casting surface is obtained.
• the hollow spheres consist, for example, of silicates, in particular of aluminum, calcium, magnesium and / or zirconium, of oxides such as aluminum oxide, quartz, magnesite, mullite, chromite, zirconium oxide and / or titanium oxide, of borides, carbides and nitrides such as silicon carbide, titanium carbide, titanium boride, Boron nitride and / or boron carbide, or carbon.
• silicates in particular of aluminum, calcium, magnesium and / or zirconium
• oxides such as aluminum oxide, quartz, magnesite, mullite, chromite, zirconium oxide and / or titanium oxide
• borides, carbides and nitrides such as silicon carbide, titanium carbide, titanium boride, Boron nitride and / or boron carbide, or carbon.
• metal or glass can also be used.
• hollow spheres are effective in several ways.
• the dense packing of the base particles in the sizing which may be considered to be the main cause of the low gas permeability, is lightened by the beads and made more gas permeable.
• the insulating properties of the hollow spheres and the gas-permeable size coatings cause a delayed heat transfer through the size into the molding material. Later, the hollow spheres melt in the casting heat and / or break under the casting pressure, causing numerous micro-defects in the size coat, thus increasing the gas permeability of the size coat.
• hollow spheres made of glass inorganic hollow body of materials ie he a similar or similar composition as the above. also contained in the sizing refractory materials, in particular the platelet-shaped refractory materials and / or which react very slowly with the refractories contained in the sizing.
• the inorganic hollow body should have a high softening temperature, so that they do not melt during the casting process, and a higher mechanical stability than hollow spheres made of glass.
• the proportion of inorganic hollow bodies which consist partly or completely of crystalline material is in the range of 0.001 to 0.99% of the weight of the ready-to-use size.
• Ready-to-use sizing is understood to mean that the base mass of the sizing has been diluted with a carrier liquid, for example water, such that one for coating molds or cores by means of one of the abovementioned techniques in the desired suspension is present in the desired layer thickness.
• the sizes are diluted with a carrier liquid, for example water to a suitable viscosity.
• the sizes to achieve the desired layer thickness of the size coat of, for example, 0.1 to 0.6 mm are typically at viscosities of 11, 5 sec. to 16 sec. measured in a 4 mm immersion discharge cup based on DIN 2321 1 diluted.
• other viscosities must be chosen accordingly.
• the determination of suitable viscosities and layer thicknesses is one of the skills of the skilled person.
• the inorganic materials of which the inorganic hollow bodies are formed are distinguished by the presence of X-ray diffraction analysis of detectable crystalline structures. That In the materials of the hollow bodies there are regions with three-dimensionally-periodic order, whose extents are larger than the coherence length of the X-rays (about 10 nm), so that sharp reflections are observed in the X-ray diffraction analysis.
• the crystalline fraction is preferably 5% by weight or more, more preferably 20% by weight or more.
• the material of the hollow spheres of borosilicate glass known from WO 2007/025769 is non-crystalline, because glass is a supercooled melt, i. it is in the amorphous state.
• the inorganic hollow body have a softening point of 1000 0 C or higher, preferably 1 100 0 C or higher, determined by a heating microscope.
• Particularly preferred inorganic hollow body with a softening point between 1200 0 C nd 1450 0 C, determined ngsmikroskop with a Erhitzu are.
• the determination of the softening point and the melting point of ceramics in a heating microscope is based on the measurement of the projection area of a cylindrical sample and its change with temperature.
• the softening point is the temperature at which the first detectable melt phenomena occur, which are manifested by smoothing of rough surfaces and the beginning of edge rounding.
• the hemisphere or melting point is the temperature at which the sample is deformed to a hemisphere by the formation of melt phases.
• the inorganic hollow bodies of the size according to the invention which consist partially or completely of crystalline material, contain no boron oxides, which act as a network image ner for glasses, and thus no borosilicate glass.
• a network converter acting compounds such as sodium and potassium oxide, which also as Flux act and reduce the melting temperature, are at best contained as impurities. Therefore, in the sizings of the present invention, the formation of low melting point compounds is suppressed by the reaction of the network walling agents and fluxes of sodium oxide and potassium oxide and the network former boron oxide with platy clay minerals and silicates commonly contained in the sizing.
• the content of the compounds which act as flux medium and network converter is preferably less than 4% by weight of sodium oxide and / or potassium oxide.
• the inorganic hollow bodies consist for example of silicates, preferably of aluminum, calcium, magnesium or zirconium, or of oxides, preferably aluminum oxide, quartz, mullite, chromite, zirconium oxide and titanium oxide, or of carbides, preferably silicon carbide or boron carbide or of nitrides, preferably boron nitride or mixtures of these materials, or mixtures of inorganic hollow bodies of these materials are used.
• hollow bodies are meant, without limitation to the spherical shape arbitrarily shaped three-dimensional structures having a cavity inside which occupies 15% or more, preferably 40% or more, more preferably 70% or more of the volume of the three-dimensional structure. This cavity can be completely enclosed by a shell of inorganic material, as in the case of hollow spheres, or incompletely enclosed, as in the case of a tube open at the ends, for example.
• These inorganic hollow bodies are preferably hollow spheres having a diameter of less than 400 ⁇ m, preferably 10 to 300 ⁇ m, particularly preferably 10 to 150 ⁇ m.
• the inorganic hollow bodies are characterized by a high mechanical stability, so that they can withstand the pressure load that inevitably occurs in the production of sizings.
• the inorganic hollow bodies to be used according to the invention preferably have compressive strengths of 10
• Hollow bodies of glass are generally lower than 10 MPa.
• the hollow microspheres used in the embodiments of WO2007 / 025769 have a
• Compressive strength of only 4 MPa Compressive strength of only 4 MPa.
• the compressive strengths can be in an isostatic
• inorganic hollow body in particular hollow balls, having a Mohs hardness of 5 to 6.
• hollow body in particular hollow balls with a compressive strength of 25 MPa or more.
• inorganic hollow body in particular hollow balls, with a cavity which occupies 70% or more of the total volume of the hollow body or the hollow sphere.
• Individual or all of the preferred properties of the inorganic hollow bodies are preferably realized in combination with each other.
• inorganic hollow bodies used which are inorganic hollow spheres which form during the combustion of coal in power plants as part of the fly ash.
• These hollow spheres are deposited from the flue gas stream and are described under the name cenospheres (Cenospheres CAS No .: 93924-19-7).
• cenospheres Cenospheres CAS No .: 93924-19-7.
• These inorganic hollow spheres preferably have the following properties:
• inorganic hollow bodies of carbon are used, preferably nano-hollow bodies
• Carbon for example carbon nanotubes or / and fullerenes. It is also possible to use mixtures of inorganic hollow bodies of carbon and inorganic hollow bodies of one or more of the other materials mentioned above.
• suspending agents e.g. water-swellable clay minerals
• the present invention also relates to the use of a sizing agent of the invention for the production of a coating on a mold or core for use in the foundry.
• the present invention also relates to a mold or a core for iron and steel casting, wherein the mold or the core on the surface facing the casting metal has a sizing coating u M Anlagend the Trocknu ngsprod ukt a sizing invention, wherein the thickness of the sizing coat 0.05 mm or more, preferably 0.15 mm or more and more preferably 0.25 to 0.6 mm, and the use of such a mold or such a core for producing an iron or cast steel piece.
• the present invention also encompasses a concentrate for the production of a ready-to-use size according to the invention, the concentrate having the following composition, based on its total weight:
• suspending agents e.g. water-swellable clay minerals
• those substances which can be assigned to more than one of the components (a) to (h) are to be assigned to the former of these components.
• the present invention also provides a process for the preparation of a size from a concentrate according to the invention described above, the process comprising the following steps:
• the present invention furthermore relates to a process for producing a size coat on a shaped body or core, comprising the steps:
• a size coat having a thickness of 0.05 mm or more, preferably 0.15 mm or more, and more preferably 0.25 mm to 0.6 mm.
• the sizings according to the invention are applied to the lost molds or cores, for example by dipping, flooding, spraying or brushing, and then dried, preferably by the application of heat or microwave radiation, so that sizing coatings are formed on the molds or cores.
• a size having the composition shown in Table 1 is prepared by mixing the components with a stirrer and then breaking up by shearing for 10 minutes with a high speed rotating dissolver.
• Corresponding production methods are known to the person skilled in the art and e.g. described in patent application WO 94/26440.
• the sizings were applied by dipping on cored boxes prepared by the CoId Box method.
• the achieved coating thicknesses of the size coatings were 0.5 mm in the wet, matted state.
• the cores were dried in a drying oven at 150 ° C. for 30 minutes. All further investigations were carried out with the sized cores thus prepared (see Table 2). It turns out that when using the sizes according to the invention on the castings fewer leaf ribs and distortions are formed than when using a size according to the prior art with a higher proportion of inorganic hollow bodies.
• FIG. 1 shows the results of measurements of the gas pressure as a function of time in a core coated with the abovementioned size A, B, C, D or E.
• the measuring method for determining the gas pressure in cores has been described by HG Levelink, FPMA Julien and HCJ de Man in Foundry 67 (1980) 109.
• the test temperature is 1445 ° C.
• the composition of the cores is as follows:
• Example C With a size according to Example C cores were coated for the manufacture of engine parts, which were manufactured by the CoId box process. For a batch of 500 pieces, no exogenous gas faults and, in particular, gas faults associated with slag were observed.

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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)

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• 2009
  • 2009-07-09 DE DE102009032668A patent/DE102009032668A1/de not_active Ceased
  • 2009-07-31 DE DE202009010423U patent/DE202009010423U1/de not_active Expired - Lifetime
• 2010
  • 2010-04-21 PL PL10717104T patent/PL2451596T3/pl unknown
  • 2010-04-21 US US13/383,169 patent/US8771412B2/en active Active
  • 2010-04-21 EP EP10717104.3A patent/EP2451596B1/de active Active
  • 2010-04-21 JP JP2012518834A patent/JP2012532027A/ja active Pending
  • 2010-04-21 CN CN201080040222.6A patent/CN102481622B/zh active Active
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• 2015
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