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
• • 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
  • B22C1/08—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 decreasing shrinkage of the mould, e.g. for investment casting
• • 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
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/10—Cores; Manufacture or installation of cores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/12—Treating moulds or cores, e.g. drying, hardening

Definitions

• the invention relates to a method for producing castings from a molten metal, in particular a light metal melt, such as molten aluminum.
• the invention relates to a molding material and its use for the production of moldings, which are used for the casting of molten metal, in particular light metal melt, such as molten aluminum.
• mold parts may be, for example, by casting cores through which cavities in the interior of the be formed to be produced casting.
• casting mold parts according to the invention may be components from which a multi-part casting mold is assembled, by means of which the outer shape of the casting to be produced is determined.
• such casting parts can be casting cores, through which cavities are formed in the interior of the casting to be produced, or casting mold elements that make up a multi-part casting mold is composed, which determines the outer shape of the casting to be produced.
• molding material systems are generally used, which are composed of a molding material and a binder. These two components are mixed together, shaped and processed into a compact body in a suitable curing process.
• the molding material used is usually quartz sand, which is bound in the majority of applications with an organic binder.
• quartz sand as a raw material for the production of mold parts has proven itself in many ways, especially in the field of casting of light metal materials.
• quartz sand can be obtained inexpensively and is characterized by a simple processability and a good quality in the image of the mold elements of each mold part to be produced.
• the molding material used for the production of the moldings must have high strength and dimensional accuracy, which is maintained even when occurring during the construction of the mold and the casting of the melt loads.
• the molding material should be removed easily after pouring. The latter proves to be particularly important when casting cores are used, which form in the casting complex shaped interiors.
• the molding materials should be so regenerable after use that the mold base material as high a rate of reuse is achieved. This can be achieved in a manner known per se by using inorganic binders which release low emissions during the production of the moldings and can be incinerated almost without residue after the end of the casting process by the action of sufficiently high temperatures.
• DE 44 46 352 A discloses a casting core composition
• a casting core composition comprising refractory grains consisting essentially of mullite, which have a substantially spherical shape, and a binder for binding the refractory grains.
• the binder used in the known casting core composition is an organic binder, in particular a thermosetting resin such as phenolic resin.
• From JP 54 004817 A is a self-hardening molding sand, consisting of quartz sand and, as a binder, water glass known.
• the known molding sand further contains fireclay particles, in particular mullite fireclay particles.
• JP 07 164102 A discloses a casting mold, in particular a casting core, which is produced from a molding base material and a thermosetting resin.
• a casting mold in particular a casting core, which is produced from a molding base material and a thermosetting resin.
• existing free spaces are then filled under pressure with a filler between the sand and resin binder components.
• the filling material may in particular consist of a refractory material and an inorganic liquid material of water glass. In this way, the temperature and pressure resistance of the known mold to the molten metal to be increased.
• JP 55 084251 A a casting method is known in which a molded part is produced using an organic binder.
• the parts of the casting mold which depict regions of the casting of large thickness, are replaced by a molding material of a molding sand and a water glass binder. In this way, high temperature cracks due to different cooling rates in the casting should be avoided.
• the known molding material systems regardless of whether they contain organic or inorganic binders, have the properties required for an optimum working result under normal conditions Especially with thin-walled moldings, as used for example for the casting of engine blocks or cylinder heads as forming cores for oil channels, it may come as a result of unavoidable thermal expansion that the requirements for dimensional accuracy of the casting are no longer met.
• Another problem with casting complex molded castings using conventionally made mold parts is that the sand is difficult to remove from the casting after cooling.
• the casting is shaken or subjected to shocks that cause disintegration of the casting cores located in the interior of the casting and the outside adhering to the casting moldings and promote trickling out of the resulting molding material particles.
• these mechanical methods of removing the moldings involve the risk of damaging the casting. This can lead to cracking, especially with filigree or thin-walled components.
• the object of the invention was to provide a method by which can produce high quality, complex molded castings and in which after completion of the casting process, the mold parts can be removed easily and safely from or from the casting.
• a molding material should be provided, with which moldings can be produced which are suitable for producing high-quality, complex-shaped castings and can be removed after completion of the casting process in a simple manner and safely from or from the casting.
• the invention is based on the recognition that it is possible by the choice of a suitable molding material to produce casting moldings which optimally combine the properties required for the simple, safe and environmentally friendly production of high-quality, dimensionally stable castings.
• the molding material according to the invention contains a granular or comparable particle-like form present and as such free-flowing base material, which exhibits a significantly low thermal expansion compared to conventionally used quartz sand during its warming unavoidably occurring during the casting.
• the molding material thus ensures a high dimensional stability in the production of complex molded castings even with low material thickness.
• the free-flowing in the unbound state base material is mixed with a binder, which has a different from the base expansion behavior when heated. Due to the different thermal expansion of mold base and binder occurs after the heat input from the casting heat to detach the binder from the grains of the molding material. As a result, therefore, when the binder expands more than the base, the binder breaks up so that it loses its solid shape and can be easily removed from the casting. Conversely, the expansion behavior of the molding base material can be such that the binding to the binder is broken by a change in volume associated with the heating and the base material again becomes free-flowing. It is essential that it comes along with the heating to break up the core or mold component, so that this has decayed after cooling of the casting in easily removable, loose items.
• the thermal expansion behavior of the molding material according to the invention in accordance with the invention is adapted to the thermal expansion behavior of the molten metal to be cast and by simultaneously this molding material based on a produced free-flowing base material, it is achieved that after cooling of the casting each of the casting at least partially encompassed or adjacent to the casting molding is broken due to the forces occurring in the course of cooling into loose individual pieces that can be easily removed.
• the fracture of the mold parts is effected by the forces occurring as a result of the different expansion of cast metal and mold material.
• the invention affects the casting of components made of aluminum melts.
• Aluminum has a high coefficient of thermal expansion, so that in the course of pouring and solidification of the melt on the molded parts in contact with the molded parts so high forces are exerted that the relevant molding safely breaks into smaller parts. This proves to be particularly favorable when the molding is a core mold.
• a further feature of the molding material obtained and used according to the invention which is favorable for the invention is that the binder and mold base material are coordinated so that the particles of the base material are thermally stable and not elastically bound by the binder in the molded parts produced from the molding material.
• the molded part produced from a molded base material of this kind behaves brittle over the entire temperature interval during the casting of the melt, which promotes the breaking of the molded parts which is desirable according to the invention.
• the binder of the moldings is preferably chosen so that it does not decompose by the action of heat. In this way it is avoided that volumes are released in the core, which could lead to a according to the invention undesirable flexibility of the molding in question.
• a further advantageous embodiment of the invention consists in that the particles of the molding base material have a substantially round, spherical shape.
• the spherical shape of the molding material and the associated prevalence of point contacts between the mold base particles promotes the automatic disintegration of the moldings as a result of the mechanical forces occurring during casting and solidification of the melt.
• a molding material that meets this requirement particularly well is synthetically produced mullite.
• a further advantageous embodiment of the invention provides that the mold base material more than 50%, preferably more than 70% of the quartz sand subsituierende alumina sand (mullite) has.
• Mullite has a round grain shape and a density comparable to quartz sand.
• the moldings produced therefrom are much easier to process than, for example, known ZrO 2 sands.
• the spherical spherical shape of the mullite particles in practice leads to a simplified processability of the molded materials produced from such molding base materials and concomitantly to a reduced wear of the tools and machines used for the production of moldings , About it owns a molding material with high Due to its low thermal expansion, mullite has a high degree of dimensional stability in the production of complex shaped castings even with low material thickness.
• molding material composed according to the invention is particularly suitable for the production of casting cores. These can be removed after casting without the risk of damaging the finished casting.
• a molding base material composed of a mullite quartz sand mixture and a molding material produced therefrom have a rather insulating effect. Therefore, these substances can be used specifically for such casting applications, where it comes to a temperature above the critical for quartz sands temperature of 573 ° C warming, but in which the thermal conductivity of the molded parts produced from the substances concerned plays a minor role or the heat conduction should be deliberately restricted.
• molding material binder and base material are also preferably matched to one another such that a molded part produced from the molding material has a low thermal conductivity. This property causes that after the casting of the molten metal, the temperature difference between the casting material and the molded part remains large, so that the risk of premature thermally or chemically induced decomposition of the molded part is reduced to a minimum.
• the disintegration of the casting cores can be assisted by matching the constituents of the molding material so that the molding base and binder expand differently when heated, with the result that the bonds between them break during a heating associated with the casting of the melt.
• the invention can be realized in a particularly practical manner by processing a molding material which consists of a mixture of one in granular or comparable particle-like form and as such free-flowing base material and an inorganic binder is formed.
• inorganic binders are their better environmental compatibility and the fact that the moldings produced with such binders can be easily recycled into the cycle of the molding material.
• molding materials which have been mixed out of a water glass-based binder and a molding base material composed according to the invention have proven particularly suitable. It is essential, however, that the expansion behavior of the mixed components sufficiently different from each other.
• mold base material and binder expand differently. In this case, it comes after the heat input from the casting heat to detach the binder from the grains of the molding material. For example, if the binder expands more than the base material, it breaks up the molding so that it loses its solid shape and breaks up into fragments. These can easily be shaken off or from the casting without the risk of mechanical damage.
• the binder expands more than the base material, it breaks up the molding so that it loses its solid shape and breaks up into fragments. These can easily be shaken off or from the casting without the risk of mechanical damage.
• essential for the fact that it comes in this variant to the inventively desired automatic disintegration of the molding consequently, the different thermal expansion of mold base and binder in the way that under the action of Gietihitze the binder as a result of resulting between mold base and binder thermal stresses from the mold base particles flakes off or breaks in itself.
• the respective casting mold part is also produced in the process according to the invention by injecting a molding material mixture composed according to the invention into the core box of a core molding machine in a known manner. Subsequently, the molding material is cured, for example, according to the method described in DE 196 32 293 Al, by applying to the mold of the core box heated to a temperature of 100 ° C to 160 ° C, a negative pressure and the core molding over a period of 20 to 30 seconds is heated by the core box.
• the mold part becomes so strong that it can be taken out of the core box and set in a heater outside the core box, for example, a microwave oven.
• a heater outside the core box, for example, a microwave oven.
• it is heated sufficiently with sufficient heat output that it is withdrawn sufficient for complete curing amount of water.
• the removal of water can also be achieved by sufficient heating of the core box itself or by hot-air gassing respectively. These measures can each be combined with a heating taking place outside the core box. It is likewise possible to effect the removal of water by means of microwave heating acting directly on the core molding still located in the core box.
• the respective molded part can be sprayed with binder liquid to increase the core surface strength.
• the moldings treated in this way have an increased stability with likewise increased abrasion resistance, so that they can be stored without problems and meet the highest demands on their dimensional accuracy. This proves to be particularly favorable with regard to an optimized quality of the casting to be produced when a water glass binder is used.
• Two recesses are formed in the underside of the camshaft core at a distance from one another in the longitudinal direction, by means of which the shape of the bearing blocks of the cylinder head to be produced for the purpose of supporting the camshaft is determined.
• the recesses extends in each case a branch of an extending with its main portion parallel and at a distance from the camshaft core ⁇ lkanalkerns.
• the length of the branches is many times bigger than theirs Diameter.
• the length of the main portion of the oil channel core is many times greater than its diameter.
• the oil channel core has been prepared in a conventional manner in a conventional form-casting machine from a molding material according to the invention, which has been produced by mixing a molding material consisting of mullite sand and quartz sand with a Wasserglaabinder. Due to the proportion of mullite sand is ensured that the Olkanalkern evenly and thus clearly unambiguously expands even when it rises in the course of the casting of the cylinder head to above 573 ° C heating.
• the casting cores deform due to the invention in accordance with wise matched characteristics of mold base and binder only slightly.
• the low thermal expansion of Formgrunastoffs thus supports the process reliable achievement of the dimensional requirements of the casting.
• the respective casting core is subjected to high mechanical stresses as a result of the considerably higher solid contraction of the casting metal compared with the casting cores.
• the treatment of the G confusekernbruch Swisse may include a gentle breaking into granular particles. Then, the obtained granular particles may be subjected to metal deposition and dedusting to restore the condition necessary for their reuse. Subsequently, the molded parts recycled to granular material are again used as the base material for the molding material composed according to the invention.
• molding materials are used in accordance with the invention which consist of mold base material mixed with waterglass binder, such as synthetic mullite, no appreciable emissions occur during the production of the moldings. This can be avoided in conventional procedure as a result of gas formation recurring casting defects, extensive provisions for the extraction of gases and complex tool cleaning. Pollution of the environment and the operating staff are reduced to a minimum.
• mullite or a comparable inert refractory material is used as the base material of the molding material system according to the invention
• another advantage of the invention is the chemical resistance of the molding material to binder and melt. This feature ensures that in the inventive procedure, a casting is obtained, the surface of which, after the emptying of the fragments of the mandrels and moldings without additional cleaning measures is completely free of Restsandanhaftept.

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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)
• Powder Metallurgy (AREA)

Applications Claiming Priority (7)

Publications (2)

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• 2002
  • 2002-09-13 MX MXPA04002424A patent/MXPA04002424A/es active IP Right Grant
  • 2002-09-13 JP JP2003528331A patent/JP2005502473A/ja active Pending
  • 2002-09-13 BR BR0212534-0A patent/BR0212534A/pt not_active IP Right Cessation
  • 2002-09-13 EP EP02772298A patent/EP1425121B1/de not_active Expired - Lifetime
  • 2002-09-13 WO PCT/EP2002/010301 patent/WO2003024642A1/de active IP Right Grant
  • 2002-09-13 PL PL02367736A patent/PL367736A1/xx unknown
  • 2002-09-13 HU HU0401547A patent/HUP0401547A2/hu unknown
  • 2002-09-13 DE DE50206490T patent/DE50206490D1/de not_active Expired - Fee Related
  • 2002-09-13 ES ES02772298T patent/ES2262845T3/es not_active Expired - Lifetime
  • 2002-09-13 US US10/489,485 patent/US20040261969A1/en not_active Abandoned
  • 2002-09-13 KR KR10-2004-7003845A patent/KR20040070330A/ko not_active Application Discontinuation
  • 2002-09-13 CA CA002461797A patent/CA2461797A1/en not_active Abandoned
  • 2002-09-13 AT AT02772298T patent/ATE323563T1/de not_active IP Right Cessation
  • 2002-09-13 CN CNB02820431XA patent/CN1298456C/zh not_active Expired - Fee Related

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