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
  • B22C1/16—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
  • 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
  • B22C1/167—Mixtures of inorganic and organic binding agents

Definitions

• the invention relates to a binder mixture for solidifying the molding sand for foundry purposes, consisting of an alkali metal silicate, preferably sodium silicate, a polyhydric alcohol, and other additives, and a method for producing foundry molds.
• Binder mixtures cast forms show partly hygroscopic properties and. therefore their dimensional stability is short-lived. This phenomenon complicates a certain stockpiling and therefore a rational way of working.
• the actual binder burns at about 200 ° C during the casting process.
• the bonds that he creates break down between the grains of sand, with the result that the sand mold disintegrates and crumbles out of complicated spatial shapes. This eliminates the need for an additional work step previously required, in which the casting mold had to be removed from the cast model with great difficulty.
• the casting molds made from sand and the binder mixture according to the invention are absolutely resistant to the effects of moisture.
• the sodium silicate and the modified carbohydrate are main components and have the following characteristic properties of this binder system: It is characterized by a low viscosity and a moisture resistance due to these components. This system also exhibits complete chemical reactions with the gelling reagents and increased reaction rates over the unmodified ones Sodium silicate binder systems. Another difference compared to the unmodified sodium silicate binder systems lies in the lower freezing point and an increased elasticity of the bonds between the grains of sand after the gelling process. This system is also characterized by a reduced catalyst consumption.
• the modified carbohydrate is a non-hygroscopic starch hydrolyzate with a reducing power of 6-15%, which can also be added as a powder with -100 mesh to -200 mesh.
• non-hygroscopic starch and the metal oxide are added in powder form and in an amount of 0.25 to% by weight of the amount of sand. This achieves a certain fluidity and through hardening.
• the non-hygroscopic starch and the metal oxide are added to the sand before the sodium silicate and the modified carbohydrate are added.
• a lubricant for example in powder form, is added in an amount of 1 to 2% by weight of the amount of sand or as an oil in an amount of 0.10-0.25% by weight of the amount of sand becomes.
• the flowability of the sand mixture is improved by the addition of this lubricant.
• the non-hygroscopic starch, the metal oxide and the lubricant increase the tensile strength in the binder system according to the invention. of the binder of almost 25%. This characteristic property can be improved by using CO 2 or a chemical catalyst. Due to rapid drying, the mixture according to the invention shows high strength within a short time. It is also noteworthy that the set sand forms to achieve a Dehydration does not need to be oven dried or burned. This advantage is reflected in a large saving in energy and labor and thus in manufacturing costs.
• ester compounds from a polyhydric alcohol and organic acids are used as catalysts.
• the following acids have proven to be particularly suitable: acetic acid, carboxylic acid, citric acid, glutaric acid and succinic acid. These different esters are mixed in different amounts and combinations.
• the type and amount of the catalyst influence the production time of the molds, which can range from 2 minutes to several hours.
• any sand customary in foundry technology such as e.g. Zircon, chromite, olivine, and silicate can be used.
• the proportion of molding sand is approximately 96.5%, that of sodium silicate solution 3%, that of starch and metal oxide 0.5% and that of the lubricant up to 0.25%. If a catalyst is used, it is added in an amount of approximately 0.3%.
• the ratio of the preparation time to the hardening time is 1: 2.
• the casting molds produced with the binder mixture according to the invention and the method according to the invention have a long shelf life, which amounts to approximately 30 days, with no special requirements being placed on the storage of the finished foundry molds.
• the binder burns at about 200 ° C during the casting process, whereby the sand structure becomes loose and crumbles.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Mold Materials And Core Materials (AREA)
• Reinforced Plastic Materials (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6226549

Family Applications (1)

Country Status (4)

Cited By (3)

Families Citing this family (2)

Family Cites Families (9)

• 1984
  • 1984-02-02 DE DE19843403583 patent/DE3403583A1/de active Granted
• 1985
  • 1985-01-12 AT AT85100275T patent/ATE61258T1/de not_active IP Right Cessation
  • 1985-01-12 EP EP85100275A patent/EP0150745B1/fr not_active Expired - Lifetime
  • 1985-02-01 DD DD85272973A patent/DD233959A5/de unknown

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