DE4221093C1 - Casting sand recovery - detaches sand from the casting in two cleaning stages to give separate types bonded only with clay and only with resin - Google Patents

Abstract

To regenerate casting sand, when bonded with clay and resin when taken from a mould, the clinging sand is initially detached from the casting as the casting is removed horizontally to remove only the sand containing a clay bonding. When the casting is vertical, or at an angle, the remaining sand containing bonded resin is detached and cleaned off. USE/ADVANTAGE - The two-stage operation removes the sand from the casting, in separate types of sand according to the bonding with clay and with resin, so that the casting sand material can be regenerated and recovered for further use, to reduce disposal vols. and with less loading on the environment.

Description

The invention relates to a method according to the preamble of patent claim 1.

A method of this type is described in DE 41 09 167 A1. There will proposed to regenerate mixed foundry sands by the fact that the clay-bound molding sand of a mechanical cleaning to remove the Black matter and separated from it the resin-bound core sand at temperatures is subjected to a thermal treatment at 800 ° C. A separate treatment Both types of sand are also found in DE-Z Gießerei 78, 1991, No. 22, pp. 822-825 and in DE-Z foundry 78, 1991, No. 21, S 733-744 proposed. There are also clues Given that a change in the emptying and gutting technology facilitate a separation can.

With regard to the prior art, reference is also made to DE 22 52 217 A1 and DE 22 52 259 A1 and DE 28 08 773 A1. In all cases, it comes down to mixed foundry sands clay-bound molding sand and resin-bound core sand to regenerate them as To be able to reuse basic material for mold and / or core production. Here thermal, pneumatic and mechanical process steps are proposed. The thermal treatment serves to remove the resinous binders. The pneumatic and mechanical treatment is used for crushing and as a result Rubbing against each other the detachment of the black substances adhering to the molding sand. It will The aim was to get as much of the molding sand and core sand as possible Recycle to relieve the landfill and thus the environment spare. Furthermore, the use of new sand can be significantly reduced.  

It has been shown that none of these methods described in practice usable result. Numerous attempts have shown that it is not it is possible to produce regenerated sand from mixed molding and core sand, the quality required for the production of cores using the warm box process owns. Due to the still existing clay - (= bentonite) components of the molding sand, the even with the most intensive treatment, cannot be completely removed, strong ones result Losses in bending strength and longer curing times, which is due to the basic proportion in the Regenerate is due. As a result, the hardener cannot react accordingly. The still dead clay and the shift of the core fraction to more Fine fractions also reduce strength. During the tests it was determined that a maximum of 10% regenerated used sand in the core production after the warm box Procedures can be used. However, that's far too little to the landfills to provide significant relief and to reduce the use of new sand.

The separate treatment of shaped and core sand described at the beginning brings significantly better results. However, there are no indications of how the separation should take place.

The invention was based on the problem of proper separation of the shape and To allow core sand to make the advantageous separate treatment can.

The method according to the invention consists in the application of the Claim 1 specified measures.

To achieve the necessary separation of the two types of sand, there are a few things noticed, about which no one has thought so far. It's not like that creates a sand mixture and then separates. That way an adequate degree of purity cannot be achieved. Instead, the Molding process ensured that the sands separated in the following steps stay. In the case of hollow bodies such as boiler sections for sectional boilers, they are down pointing core brands designed so that a destruction of the core in a lying position not possible. For example, a thin gap can surround the inserted core  fills with cast iron when pouring. This creates a stable cap, which in some places can be interrupted to achieve contact surfaces for the core. It is also possible to close the lower core brands with a stable protective layer or edge zone Mistake. The casting is now poured horizontally, emptied and a first Subjected to cleaning. When emptying and cleaning, e.g. B. by rotating brushes only the clay-bound molding sand is removed, which is then in its own process is regenerated.

After the process described, there is an externally cleaned casting. Now will the cap or protective layer destroyed and in a vertical or inclined arrangement in a second cleaning process in a manner known per se, the resin-bound core sand away. This is then subjected to a known thermal treatment and returned to core sand processing.

Claims (1)

Process for the regeneration of foundry sands, namely clay-bound molding sand and resin-bound core sand, with the aim of reusing them for the production of casting molds or cores, in which the clay-bound molding sand is subjected to a mechanical cleaning to remove the black substances and then the molding sand preparation and separately therefrom the resin-bound core sand is subjected to a thermal treatment at temperatures around 800 ° C and is fed to the core sand preparation after classification, characterized in that the castings are horizontally molded, poured, emptied with a stable boundary of the core brands pointing downwards and only a first cleaning process for removal be subjected to the clay-bound molding sand and then, after destroying the stable boundary in a vertical or inclined arrangement, the second cleaning operation for removing only the resin-bound core sand takes place.