DE10312782A1 - Water-soluble salt cores and process for producing water-soluble salt cores - Google Patents

Abstract

Water-soluble salt cores, which are produced by compressing water-soluble salts under pressure and then sintering, characterized in that they contain from 0.5 to 15% by weight of a porosity-producing additive such as sugar, phenolic resin solution, wheat semolina or oat bran or a combination contain at least two of these substances.

Description

The present invention relates to water-soluble Salt cores and process for the production of water-soluble salt cores.

Such salt cores for foundry purposes, which are washed out after the casting of parts, have long been known, as have attempts to optimize them by adding additives. So in the DE-C-14 83 641 found that an addition of up to 10% borax, magnesium oxide or talc improves the resilience of salt cores made of NaCl and / or KCl. The DE-C-19 24 991 suggests adding water glass to further increase the compressive and bending strength. Other salts have also been proposed, such as an alkaline metal halide in the US-A-33 56 129 , In recent times there have been attempts to make the surface of salt cores as smooth and pore-free as possible, such as through the use of ceramic additives as in PCT-WO-98/00251 or similarly from aluminum oxide in Japanese Patent Laid-Open 60118350. So smooth surfaces can be used an RZ <40 can be achieved.

However, it has been found that with very smooth surfaces when circulating around the salt core 1 through the melt 2 binding problems due to the formation of an oxide wedge 3 comes from the melting melt 2 ' is enclosed and forms an air cushion that can no longer escape, as in the 1 and 2 is shown. Attempts are being made to counteract this by means of very complex processes, by avoiding cold runs by pouring under protective gas and complex cleaning of the melt.

Object of the present invention is the problems outlined by the formation of an oxide wedge and thus to avoid the complex manufacturing processes and one To create a salt core with a controlled adjustable porosity, where there is no loss of strength.

This task is accomplished with the 1 mentioned features solved. Advantageous designs and further developments of the invention and in particular a method according to the invention are in the further claims includes.

According to the invention, water-soluble salt cores are by compressing water soluble Salt under pressure and then Sintering are produced, characterized in that they have a Portion of 0.5 to 15 wt .-% of a porosity-producing additive such as Sugar, phenolic resin solution, Wheat semolina or Oat bran or a combination of at least two of these substances contain.

When using sugar, this shows preferably a grain size of 0.2 up to 1.6 mm.

The water-soluble salt cores according to the invention can further a share of 0 to 10% each of other known additives such as Contain borax, magnesium, graphite and / or talc.

• – Mischen wasserlöslicher Salze wie NaCl oder KCl mit einem Anteil von 0,5 bis zu 15 Gew.-% eines Porosität erzeugenden Zusatzes wie Zucker, Phenolharzlösung, Weizengrieß oder Haferkleie oder eine Kombination wenigstens zweier dieser Stoffe und jeweils 0 bis 10 Gew.-% Borax, Magnesium, Graphit oder Zucker in einer Mischtrommel,
• – Einfüllen der Mischung in eine Form,
• – Pressen der Mischung in der Form mit einem Presdruck von zwischen 1.500 und 2.500 KN/cm²,
• – Sintern des gepressten Salzkerns bei einer Temperatur von 500 bis 740°C während 1,5 bis 2,5 Stunden,
• – Entnehmen des Salzkerns und Abkühlen.

An inventive. The process for producing water-soluble salt cores is characterized by the steps:

• - Mixing water-soluble salts such as NaCl or KCl with a proportion of 0.5 to 15% by weight of a porosity-producing additive such as sugar, phenolic resin solution, wheat semolina or oat bran or a combination of at least two of these substances and in each case 0 to 10% by weight Borax, magnesium, graphite or sugar in a mixing drum,
• - filling the mixture into a mold,
• Pressing the mixture in the mold with a pressure of between 1,500 and 2,500 KN / cm ² ,
• - Sintering the pressed salt core at a temperature of 500 to 740 ° C for 1.5 to 2.5 hours,
• - Remove the salt core and cool.

The result is a salt core 11 in the like in the 3 and 4 shown the ascending melt 12 generates no air wedge, but existing air 13 in the pores 11 ' of the porous salt core 11 repressed.

Claims (7)

Water-soluble salt cores, which are produced by compressing water-soluble salts under pressure and then sintering, characterized in that they contain from 0.5 to 15% by weight of a porosity-producing additive such as sugar, phenolic resin solution, wheat semolina or oat bran or a combination contain at least two of these substances. water-soluble Salt core according to claim 1, characterized in that the sugar a grain size of 0.2 up to 1.6 mm. water-soluble Salt cores according to claim 1 or 2, characterized in that they contain a proportion of 0 to 10 wt .-% borax. water-soluble Salt cores according to claim 1, 2 or 3, characterized in that they contain a proportion of 0 to 10 wt .-% magnesium. water-soluble Salt cores according to one of the claims 1 to 4, characterized in that they have a share of 0 to Contain 10% by weight of graphite. water-soluble Salt cores according to one of the claims 1 to 5, characterized in that they have a share of 0 to Contain 10% by weight talc. A process for producing water-soluble salt cores according to one of claims 1 to 6, characterized by the steps: - Mixing water-soluble salts with a proportion of 2 to 10 wt.% Sugar and 0 to 10 wt with a pressure of between 1,500 and 2,500 KN / cm ² , - sintering the pressed salt core at a temperature of 500 to 740 ° C for 1.5 to 2.5 hours, - removing the salt core and cooling.