Classifications

• • 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
  • B22C9/126—Hardening by freezing

Definitions

• the invention relates to a method of producing frozen casting moulds or cores of a granular material and a binder in a mould chamber or a core box, comprising the use of a freezable binder which is in a gas or liquid state at positive temperatures calculated in °C.
• US-A-4 150 704 teaches a method in which the mould sand is admixed with a controlled quantity of water which after moulding is frozen to ice in a certain depth from the surface that is caused to contact molten metal e.g. by placing a layer of so-called dry ice or spraying liquid nitrogen on the surface.
• the water melts and evaporates so that the mould begins collapsing without the use of mechanical means. Practically no smoke is developed in the casting process, and the mould sand can be reused right away.
• Freezing of the added water is by nature a rather slow process, and consequently it takes a relatively long time from the moment when the moulding process is finished until the mould has frozen deep enough to be able to resist the effect of molten metal for a sufficiently long time, and this in turn causes the overall mould production to become considerably more time- consuming than the conventional mould manufacturing process.
• SU-A-428843 it has been proposed to shorten the process time by the application of a hollow pattern, to the cavity of which a cooling medium is continuously supplied.
• Another proposal set forth in PL-A-21861 1 is to freeze liquid in sand moulds or cores by precooling the pattern or core box in question which is to be engaged by the sand.
• PL-A-224193 describes the application of a disposable pattern of a permeable material which disintegrates when exposed to the molten metal and through which liquid gas is applied to the mould sand.
• DE-Al-29 09 839 discloses a mould forming process, in which two streams of sand lead to a mixing device. In one stream water is added to the sand, whereas the sand in the other stream is subjected to a cooling agent such as liquid nitrogen. From the mixing device the mixture of moistened and cooled sand is supplied to the mould box.
• a still further reduction of the time needed for the production of frozen casting moulds or cores may be obtained by a method in which the binder has been frozen before it is mixed with granular material.
• the moulding time is substantially reduced to the time it takes to fill the flask or core box with the mixture of and and binder and to compress said mixture sufficiently around the pattern or adjacent the walls of the core box cavity to enable the binder to putty the sand corns together.
• a mould binder may be used which is present in the form of fine, dendritic particles, e.g. snow, in the mould material, and a compression during the moulding process may entail that the binder obtains part of or its entire binding capacity depending upon the temperature conditions at the time of the mould manufacturing process.
• the mould binder used may, as stated in claim 3, also be present in the form of a finely divided powdered material, e.g. ice, in the mould material, and a compression during the moulding process may entail that the binder obtains part of or its entire binding capacity depending upon the temperature conditions at the time of the mould manufacturing process.
• a finely divided powdered material e.g. ice
• the snow or the ice When a suitable mixture of granular material and snow or broken ice is compressed in a mould box, the snow or the ice may thus be caused to bind the grains of the material together to impart a cohesive force to the mould or the core sufficient for it to resist the effect from liquid metal which is poured down into the finished mould with or without cores.
• a corresponding effect can be achieved by injecting one of the mentioned mixtures of mould material into a core box with a sufficiently great force and at a sufficiently great rate.
• the precooled binder in the form of pulverized material may, as stated in claim 4, also be combined with liquid gas. This permits the temperature of the mould material to be reduced to a very low value before and during the moulding process and during the immediately following casting process.
• the mixture must be homogeneous and easy flowing.
• binder there is nothing to prevent the use of conventional setting binders.
• water glass and liquid carbon dioxide as stated in claim 5, or a mixture of polyisocyanate and phenol resin which is activated by precooled, liquid dimethylethyl amine or triethyl amine, as stated in claim 6. This provides for a reduction in the use of an environmentally harmful binder.
• the granular material used for the formation of the mould or the core may have been deep frozen in advance in a manner known per se.
• the process ingredients may have been deep-frozen in advance by means of an admixed freezing agent such as liquid gas.
• an inert gas obviates any risk of chemical attacks on the equipment used for the process or for chemical reactions with the casting metal.
• the required cooling may also in a manner known per se be effected or be supported by deep-freezing the parts of the apparatus which the mould material contacts during the moulding process.
• the pattern board which contacts the same mould surface as the molten metal does later may have been deep-frozen in advance, and a core box deep-frozen in advance may be used in the production of cores.
• the core box with the core or cores may be cooled simultaneously and additionally, e.g. with liquid gas.
• a specific embodiment of the method of the invention in the production of casting moulds comprises the use of deep-frozen disposable patterns of a material which evaporates when heated, as stated in claim 7, and this material may expediently have been deep-frozen and foamed, as stated in claim 8.
• Such patterns may be produced currently in a particular bifurcate pattern mould box corresponding to a conventional core box and be placed in a closed chamber, following which the space between the pattern and the walls of the chamber is filled with the moulding material which is cooled by the pattern and may additionally have been cooled in advance as mentioned above. After the moulding process is finished the pattern evaporates rapidly owing to the heat received. This obviates the inconvenient development of gas, which otherwise takes place in the moulding of disposable patterns.
• This embodiment of the method results in particularly accurate castings because the inaccuracies which in the conventional mould manfacturing process result from wear on the pattern board caused by shootings of sand, are avoided. Moreover, bifurcation of the mould box is not required when readily evaporable patterns are used.
• apparatus for the production of casting moulds and/or apparatus for the production of cores are used, the apparatus or parts of it being contained in a cooling chamber.
• the necessary temperature conditions may be readily and constantly maintained so that valuable production time is not lost in waiting for cooling.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=8114515

Family Applications (1)

Country Status (13)

Families Citing this family (2)

Citations (5)

Family Cites Families (6)

• 1980
  • 1980-06-23 DK DK267580A patent/DK151776C/da active
• 1981
  • 1981-06-19 IT IT22460/81A patent/IT1136695B/it active
  • 1981-06-22 EP EP81901923A patent/EP0054061B1/en not_active Expired
  • 1981-06-22 CS CS814707A patent/CS257755B2/cs unknown
  • 1981-06-22 JP JP56502323A patent/JPH0144424B2/ja not_active Expired
  • 1981-06-22 WO PCT/DK1981/000062 patent/WO1982000015A1/en active IP Right Grant
  • 1981-06-22 ES ES503284A patent/ES503284A0/es active Granted
  • 1981-06-23 BE BE0/205189A patent/BE889350A/fr not_active IP Right Cessation
  • 1981-06-23 ZA ZA814230A patent/ZA814230B/xx unknown
  • 1981-06-23 CA CA000380444A patent/CA1183320A/en not_active Expired
  • 1981-06-23 DD DD81231059A patent/DD159531A5/de not_active IP Right Cessation
  • 1981-09-23 PL PL1981231819A patent/PL130506B1/pl unknown
• 1982
  • 1982-02-22 SU SU823398237A patent/SU1366043A3/ru active

Patent Citations (5)

Non-Patent Citations (2)

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