EP1250971A1 - Agent de démoulage pour procédé de moulage - Google Patents

Agent de démoulage pour procédé de moulage Download PDF

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Publication number
EP1250971A1
EP1250971A1 EP01810379A EP01810379A EP1250971A1 EP 1250971 A1 EP1250971 A1 EP 1250971A1 EP 01810379 A EP01810379 A EP 01810379A EP 01810379 A EP01810379 A EP 01810379A EP 1250971 A1 EP1250971 A1 EP 1250971A1
Authority
EP
European Patent Office
Prior art keywords
release agent
agent according
casting
metal
colloid particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01810379A
Other languages
German (de)
English (en)
Inventor
Thomas Imwinkelried
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3A Composites International AG
Original Assignee
Alcan Technology and Management Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcan Technology and Management Ltd filed Critical Alcan Technology and Management Ltd
Priority to EP01810379A priority Critical patent/EP1250971A1/fr
Priority to PCT/EP2002/003226 priority patent/WO2002083338A2/fr
Publication of EP1250971A1 publication Critical patent/EP1250971A1/fr
Withdrawn legal-status Critical Current

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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

Definitions

  • the present invention relates to a release agent for use in molds, in particular Casting molds of metal, of casting devices for the production of metal castings, in particular metal castings from a light metal, and the use of the release agent.
  • metal casting molds are used to directly cast or molded parts cast.
  • die casting processes such as permanent mold casting, tilt casting, vacuum casting or low pressure casting known, which is characterized by comparatively slow Mark mold filling times.
  • other molding processes such as die casting, Thixoguss or Vacural known, which is characterized by comparatively short mold filling times distinguished.
  • the melt is in the die casting, low pressure casting and Thixo casting process with pressurization, possibly with the generation of a negative pressure or vacuum, pressed into the mold.
  • the pressures used in a die casting process can sometimes be very high be and for example in the range of 100-1000 bar, so that the metal melt to some extent is shot into the mold.
  • the one intended for a molded part Molten metal is dosed ready in the so-called filling can or casting chamber placed and pressed into the mold cavity by means of a piston over the sprue channel. After the molten metal has solidified into the casting, the mold can be opened and that Cast part can be removed. Die casting is particularly suitable for efficient production of large series as well as for the production of thin-walled castings.
  • the mold cavity of the casting mold is evacuated or a negative pressure is generated before the molten metal is shot in.
  • Such methods are, for example, under the name MFT method (M inimum F illing T ime) or Vacural method known.
  • permanent molds i.e. reusable Casting molds used, with these permanent forms predominantly around metallic permanent forms from e.g. Steel, in particular from nitrided hot-work steel, is.
  • release agents are used before the actual casting process be applied to the surface of the mold cavity of the casting mold. Release agents are responsible for the adhesive forces between the melt and the mold decrease, i.e. prevent their sticking by placing them between both surfaces form an easily separable film. The separation effect of this film is mostly based on reducing the intermolecular forces, using the release agent as a shear surface acts.
  • the cleaned air is blown out, for example with compressed air Mold surface after demoulding in preparation for next pouring process again with release agent.
  • the release agent is usually sprayed on, the temperature of the mold being sufficient must be high so that the solvent evaporates within a reasonably short time and a release agent film can form.
  • the temperature of the mold must not be too high.
  • release agents are in the form of suspensions, i.e. as coarsely disperse systems with particle sizes larger than 1 ⁇ m, or as emulsions.
  • the main common classes of release agents are silicones in the form of oils, Oil emulsions in water or fats and resins, waxes, such as polyethylene and ester waxes, Metal soaps, greases, polymers, hydrocarbons and inorganic release agents in the form of powders (such as graphite, talc and mica).
  • solvent-based release agents often contain or consist of organic components that decompose on contact with the hot melt and release gases which are enclosed in the casting when the mold is filled can and affect its mechanical properties and weldability. As a result, good mechanical properties can only be achieved by low-fumigation Reach release agent.
  • the object is achieved in that the separating agent contains colloidal particles with particle diameters in the range of 1 - 1000 nm and the colloid particles for application to the mold surface in a disperse system, and the Colloid particles on the mold surface after evaporation of the solvent to form layers.
  • the release agent preferably consists essentially or completely (with the exception of of additives) from the aforementioned colloid particles. After evaporation of the solvent Colloidal particles present on the parting surface of the casting mold preferably form an uncrosslinked solid structure.
  • the colloid particles preferably have a diameter in the range from 1 to 500 nm, in particular from 1 to 200 nm, advantageously from 5 to 100 nm.
  • particle is the maximum particle diameter without further specification meant.
  • the diameter of the colloid particles depending on the one used Casting pressures, preferably in the range from 5 to 100 nm.
  • the colloid particles are preferably in 3-dimensional, rounded circumferential geometries before and are advantageously spherical. Globular colloids or spherical colloids are preferred.
  • the colloid particles can also be 3-dimensional polygonal circumferential geometries exhibit.
  • the colloidal particles can also take the form of fractal spatial geometries be constructed.
  • the maximum diameter of the individual colloid particle preferably does not deviate more than 100%, especially not more than 50%, from its smallest diameter.
  • the size distribution of the colloid particles in the release agent is preferably mono- or iso-disperse, i.e. the colloidal particles are essentially uniform in size.
  • the Colloidal particles can also be in a poly- or heterodisperse size distribution.
  • the size distribution preferably corresponds to a Gaussian distribution.
  • colloids can also be obtained by chemical reaction from a solution, e.g. by Hydrolysis of a sol.
  • the colloids can be lyophilic colloids, i.e. the colloids are formed by the direct dissolution of solid or liquid substances or by the solvent solvated.
  • the colloids can be lyophobic colloids, i.e. the colloids can only be produced in liquid separation media in which the substance in question is insoluble is.
  • the release agent solution is preferably in the form of an incoherent system or as a sol, i.e. the colloidal particles are free to move and are not related to other colloidal particles.
  • the solvent of the release agent according to the invention is preferably aqueous built up.
  • Organic-based solvents, especially alcoholic ones, are also possible Base like methanol or ethanol.
  • the release agent is available for application to the mold surface in the form of a solution.
  • the release agent is applied using known methods, such as spraying or To brush.
  • the solvent is used for evaporation brought so that colloidal particles of the size mentioned on the mold surface stay behind.
  • the colloidal particles can be seen on the interface after the solvent has evaporated form single or multi-layer layers, the number of layers being the number of colloidal particles arranged one above the other in layer thickness.
  • the number the layer layers can e.g. from 1 to 100, preferably 1 to 50 and in particular 1 to 20.
  • the effect of the colloidal release agent layer according to the invention is based on the fact that the contact area or contact area between the molten metal and the release agent is considerably reduced, ie the molten metal only lies on the colloid particles at certain points or areas, so that there is no direct contact between the liquid metal and the casting mold is formed, and due to the specifically optimized colloid size, the liquid metal cannot penetrate between the colloid particles because of its surface tension.
  • the colloidal particles should not be wetted by the liquid metal or only slightly.
  • the wetting angle or wetting angle ⁇ is preferably in the range from 90 ° to 180 °, preferably in the range from 150 ° to 180 °, and in particular around 180 ° (degrees of angle) (see “Measurement of the Surface Tension of Liquid Aluminum Alloys", S. Engler u. R. Ellerbrok., Foundry Research, 1/1974 , p. 47 ).
  • the geometric shape and the size of the colloidal particles are therefore crucial for the release agent to work optimally.
  • the size of the colloidal particles is specifically optimized depending on the physical properties of the molten metal, such as surface tension, and on the mold filling pressures used or the contact pressure of the molten metal on the mold surface.
  • the colloid particles are preferably inorganic colloids, and contain or consist from oxides or metal oxides. Furthermore, the colloidal particles can also be organometallic Compounds, in particular based on alkolates, ketones or carbonic acids, contain or consist of.
  • the colloid particles are preferably made of metal oxides.
  • metal oxides are ZnO, Fe 2 O 3 , SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , SnO 2 , Li 2 O, CeO 2 or V 2 O 5 and in particular SiO 2 , and Al 2 O 3 or mixtures of two or more of the aforementioned metal oxides.
  • Suitable mixed oxides are, for example, ZnO / Al 2 O 3 , Fe 2 O 3 / SiO 2 , and in particular Al 2 O 3 / SiO 2 .
  • the colloid particles of a release agent solution are, for example, in a weight-based one Concentration from 1: 100 to 1: 1000 (colloids: solvents), especially from 1: 500 to 1: 1000, before.
  • release agent solutions according to the invention are shown below:
  • Examples of such disperse systems based on silica are Particlear® from Dupont, Ludox® from Grace Davison or Snowtex® from Nissan Chemical America Corp.
  • Dispersal® from Condea.
  • colloidal-based disperse systems listed above are as such for various Known applications, their use as release agent systems in metal casting processes is not yet known.
  • Additives can also be added to the release agent or release agent solution, e.g. Additives such as acids or bases to adjust the pH, additives for stabilization of the release agent or colloidal solution, inhibitors as corrosion protection, additives such as fungicides or bactericides for preventing fungus formation or the like, surfactants for wetting the surfaces, or additives for preservation or preservation of the release agent. Additives can also be used to increase the viscosity of the Release agent solution can be used.
  • the optimal diameter of the colloid particles can be determined of release agents for casting certain metals under specific Calculate pressure ratios at which the effects described above are optimal come.
  • L is the distance between the two support points 2
  • P is the pressure prevailing in the molten metal
  • Fp the force acting on the surface 1 from the molten metal
  • Fs is the tension force of the surface 1.
  • the maximum distance of the molten metal between the two support points 2 is according to Equation (3) proportional to the surface tension ⁇ and inversely proportional to the applied pressure P.
  • the maximum diameter of the colloidal particles at which the above-mentioned effect still occurs, according to equation (3) of the 2-D model, is around 9 nm and at a prevailing pressure P of 100 bar and constant surface tension ⁇ around 90 nm.
  • the maximum diameter of the colloidal particles can further approximate realistic conditions can be calculated using a 3D model.
  • the colloid particles are simplified as balls 11, the arrangement of the balls for subsequent ones Calculation method corresponds to the densest spherical packing (see Fig. 2a and 2b).
  • the surface 15 of the liquid metal is not approximate to the three neighboring colloid particles 11, 12, 13 for the following calculations, rather the surface tension acts on a certain arc length, the so-called contact line 14.
  • the arc length 14 is around ⁇ * r / 3.
  • the maximum distance of the molten metal between the two contact lines (arc lines) 14 (approximated by the center point distance 2 * R of two balls) according to equation (7) also proportional to the surface tension ⁇ and inversely proportional to the applied pressure P.
  • the maximum diameter 2 * R of the colloid particles according to equation (7) (3-D model) is approximately 8 nm and at one prevailing pressure P of 100 bar and constant surface tension ⁇ approximately 80 nm.
  • Fig. 2a shows the deflection of the surface 15 of the liquid metal between three spherical ones Colloid particles 11, 12, 13.
  • 2b schematically shows the arrangement of the colloid particles 11, 12, 13 in the densest Ball packing and the contact surface of the molten metal with the contact lines 14 in plan view.
  • the release agent according to the invention is suitable for all molding processes in which Permanent forms, in particular permanent forms made of metal, are used.
  • the inventive Release agent is particularly suitable for applications on permanent metal molds, in particular from steel, such as hot-work steel, or from gray cast iron and for permanent molds made of aluminum and its alloys.
  • the release agent according to the invention can, provided the diameter of the colloid particles are in accordance with the aforementioned physical properties of the molten metal or the pressures used, for casting a variety of Metals are used, in particular for casting tin and tin alloys, Copper and copper alloys, bronze, lead and lead alloys, zinc and zinc alloys, Silver and silver alloys, gallium and gallium alloys, and in particular Aluminum as well as magnesium and their alloys.
  • Other castable metals, for which the release agent according to the invention can be used, should be by preceding Enumeration cannot be excluded.
  • the release agent according to the invention is suitable for all molding processes, in particular for the casting processes mentioned in the introduction, such as vacuum casting, low pressure casting, die casting, Thixo casting, vacural or squeeze casting processes.
  • a release agent of the structure and composition according to the invention is distinguished due to its excellent separating effect and the lack of or reduced gas generation upon contact with the molten metal. Furthermore, the release agent in relatively small amounts are used, e.g. in an amount of less as 1g colloid particles per casting process. Furthermore, there is no wetting of the release agent through the metal, especially the aluminum or magnesium melt. The Release agent does not undergo chemical reactions with the molten metal, especially with the aluminum or magnesium melt, yet it has a corrosive effect the casting mold, in particular compared to casting molds made of steel. The proposed Release agents, especially the resulting waste when cleaning the mold, are also environmentally friendly.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
EP01810379A 2001-04-17 2001-04-17 Agent de démoulage pour procédé de moulage Withdrawn EP1250971A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP01810379A EP1250971A1 (fr) 2001-04-17 2001-04-17 Agent de démoulage pour procédé de moulage
PCT/EP2002/003226 WO2002083338A2 (fr) 2001-04-17 2002-03-22 Agent de demoulage pour procede de coulee

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP01810379A EP1250971A1 (fr) 2001-04-17 2001-04-17 Agent de démoulage pour procédé de moulage

Publications (1)

Publication Number Publication Date
EP1250971A1 true EP1250971A1 (fr) 2002-10-23

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EP01810379A Withdrawn EP1250971A1 (fr) 2001-04-17 2001-04-17 Agent de démoulage pour procédé de moulage

Country Status (2)

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EP (1) EP1250971A1 (fr)
WO (1) WO2002083338A2 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3357481A (en) * 1965-08-27 1967-12-12 Nalco Chemical Co Method of inhibiting erosion on mold surfaces
US3852085A (en) * 1974-01-09 1974-12-03 Du Pont Stable refractory slurry composition
DE3120582A1 (de) * 1981-05-21 1982-12-09 Schweizerische Aluminium AG, 3965 Chippis Kokille mit waermeisolierender schutzschicht

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3357481A (en) * 1965-08-27 1967-12-12 Nalco Chemical Co Method of inhibiting erosion on mold surfaces
US3852085A (en) * 1974-01-09 1974-12-03 Du Pont Stable refractory slurry composition
DE3120582A1 (de) * 1981-05-21 1982-12-09 Schweizerische Aluminium AG, 3965 Chippis Kokille mit waermeisolierender schutzschicht

Also Published As

Publication number Publication date
WO2002083338A3 (fr) 2003-05-01
WO2002083338A2 (fr) 2002-10-24

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