KR20000071196A - Method for the Manufacture of Cores for Metal Casting Processes - Google Patents

Abstract

In the process of producing sand cores for the metal casting process by means of a urethane cold box process, the gaseous trimethylamine is guided through the parts of the metering device 3 and then 0.01 based on the amount of sand used for the coarse sugar. To a concentration of 0.12% by weight into the core injection machine (4) where it comes into contact with the sand, and a cleaning gas is introduced before introducing the gaseous trimethylamine into the core injection machine (4), trimethylamine The ratio of the cleaning gas to the amount of the cleaning gas used (L) relative to the amount (T) of trimethylamine is in the ratio of T: L of 1: 1000 to 1: 10000.

Description

Core manufacturing method in the metal casting process {Method for the Manufacture of Cores for Metal Casting Processes}

Methods for the preparation of cores for metal casting processes are known. One such method is the urethane cold box process and the process uses amines as catalysts or curing agents (Giesserei 78 (1991), volume ll, in the articles in the special editions of pages 372 to 374). In the above known process for core and mold production, a molding composition containing benzyl ether resin (oso-phenol resol) and isocyanate was used and the molding composition was prepared using a third amine as catalyst. Since the catalytic effect of amines is particularly favorable in the gas phase, tests have been carried out using trimethylamine (TMA), which has a boiling point of about 3 ° C., and for this reason the curing operation is relatively easy with gaseous amines. It is possible in a simple way: a third subtype by the formation of reactive transition compounds during the polyurethane reaction The synergistic effect of Min is described by the following equation.

When making cores by the known methods described above, it is disadvantageous that the third amine is charged to the core injection machine in a significant excess of the required amount. Although it has been shown that the application of trimethylamine makes it possible to advantageously reduce the amount of amine used by 50% over other amines, the application of trimethylamine still has its associated disadvantages. One problem is the extreme discomfort generated by odors, which makes it important that all parts of the equipment used are absolutely leakproof. All pipe connections must be isolated here at a relatively high cost.

From the Giesserei article it can also be seen that the reactivity of different amines increases from "inert" to "active" in the order of TEA, DMIA, DMEA, TMA. Apart from this poor reactivity, TEA also suffers from the fact that it forms an aerosol.

Binders for casting materials for casting light metals are described in DE-A-3017925, which discusses the details of the cold box process technology. For example, it has been shown that trimethylamine or triethylamine can be used as the third amine. In the described process it is advantageous to use a flow of inert gas such as air, carbon dioxide or nitrogen comprising from 0.01 to 30% by volume of the third amine.

Giesserei 58 (1971), NO. 9, 6May, pages 249-254, describes the application of triethylamine in G.Engels of Stuttgart's "Oeffentliche Diskussion Cold-Box-Verfahren (Open Discussion Cold Box Proless) It has been shown here that the amount of triethylamine to be used depends in particular on the size of the core, which in theory indicates that a small amount of catalyst can be used, such as 0.01 to 0.02% by volume. Not only because, but also because it leads to a decrease in core quality, in no case should the addition ratio of 0.05 to 0.1% by volume be exceeded.

The present invention relates to a method of manufacturing a core for a metal casting process.

1 is a simplified schematic process diagram relating to a core manufacturing method for a metal casting process according to the present invention,

2 is a simplified schematic process diagram of another embodiment of the method of the present invention.

It is an object of the present invention to provide a method of preparing cores for metal casting processes, which provides a method in which the above mentioned disadvantages in one method can be largely avoided and at the same time implemented in a relatively cost effective manner.

The present invention thus provides a process for producing sand cores for metal casting processes in which gaseous trimethylamine is guided through the parts of the metering device 3 and then 0.01 based on the amount of sand used per coa. To a concentration of 0.12% by weight, which is guided into the core injection machine 4 where it comes into contact with the sand, where a washing gas is introduced prior to the introduction of gaseous trimethylamine into the core injection machine 4 and here The amount L of washing gas used relative to the amount T of trimethylamine lies in the ratio of T: L from 1: 1000 to 1: 10000.

In general, sand charged to a core injection machine is already mixed with benzyl ethylene and isocyanate so that core production can be carried out according to the principle of the urethane gold box process. For example, a general conveying facility for a gas such as a metering device in which trimethylamine is suitably controlled by a control chain or regulator can be used. Thus, this facility can be made up of several components, such as transport equipment, measuring devices, controllers, etc., or it can be manufactured as a single unit. The gaseous trimethylamine is guided through one part of the meter, although it does not have to flow through all the parts. It is therefore possible for liquid trimethylamine to flow through several parts of the metering device and then to be converted into the gas phase and in the gaseous form through the rest of the metering device. Surprisingly, it has been found that extreme odor discomfort can be largely avoided when using the method of the invention and as a result no costly insulation of the components of the core making facility is required. In addition, advantageously there is no odor discomfort during the subsequent storage of the prepared cores. A near stoichiometric conversion of the trimethylamine is achieved, as a result of which the process of the present invention results in a relatively small amount of trimethylamine used. It is also surprising that cost can be done efficiently.

The introduction of the cleaning gas can be done before or after the measuring device. The core is cleaned by the cleaning gas and at the same time it is exposed to trimethylamine so that the sand in the core injection is simultaneously brought into contact with the trimethylamine and the cleaning gas so that extreme odor discomfort can also be completely avoided during core storage. It is advantageous.

In a preferred embodiment of this invention the cleaning gas is introduced directly into the metering device. This measure allows the amount of conduits or pipe piping to be reduced and this is particularly advantageous when space for installation of co-production facilities is limited.

In a preferred embodiment of this invention the trimethylamine is supplied in liquid form to the measuring bellows forming part of the measuring device and thereafter it is in gaseous form, via a measuring, regulating or control unit which also forms part of the measuring device. You are guided. Trimethylamine is normally available in liquid form on the market. However, it is advantageously converted to gaseous phase before triethylamine is brought into contact with the sand and core injection machines already brought into contact with benzyl ether resin and isocyanate. This allows for a relatively simple and uniform mixing of the sand with trimethylamine and at the same time increases the reactivity of the trimethylamine. Surprisingly it has been shown that the conversion of trimethylamine from the liquid phase to the gas phase can be achieved by bringing trimethylamine into the metering bellows. Heat is absorbed from the environment during the conversion of trimethylamine from the liquid phase to the gas phase, but the metering bellows remain able to function better than other transport equipment. The trimethylamine of the gas is then passed through a measurement, control or control unit that can dispense the desired amount of trimethylamine to be used. This information is communicated directly to the weighing bellows using a circuit and from there it is changed to the corresponding setting for the stroke of the weighing bellows. It is particularly advantageous that the metering bellows can have a relatively simple form because it can be easily adapted for use in existing co-production plants.

The invention is illustrated by way of example in the accompanying drawings:

1, sand already mixed with benzyl ether resin and isocyanate is taken out of the sand mixer 5 and conveyed to the core injection machine 4 by a conduit 10. The cylinder 1 contains trimethylamine in liquid and is heated with the aid of a water bath 8. Heating takes place by means of a heating coil 7 directly connected to the heating device 6. The conversion of trimethylamine from the liquid phase to the gaseous phase results from the application of heat. The gaseous trimethylamine passes through conduit 2 to the metering device 3. The amount of trimethylamine in the metering device 3 is measured and adjusted to the desired amount according to the given specific value. Trimethylamine then passes through conduit 9 into coa injection machine 4 at a concentration of 0.01 to 0.12% by weight based on the weight of the sand used for the coa sugar and is in contact with the sand there. In order to avoid causing extreme discomfort due to the smell of trimethylamine, cleaning air is introduced into the conduit 2 through the conduit 11 and the valve 12 and consequently the core ejector 4 through the conduit 9. The sand in the core injection machine 4 is cleaned at the same time while the trimethylamine is introduced into the shell.

Referring to FIG. 2, the metering bellows 3a and the measurement, adjustment and control unit 3b together form a metering device corresponding to the metering device 3 of FIG. 2. Trimethylamine appears as a liquid in the cylinder 11. When the valve 15 is closed, the liquid trimethylamine is guided into the metering bellows 3a via the open valve 13. This causes the trimethylamine to swell and convert largely into the gas phase. The setting of the stroke of the metering device 3a is made by the circuit 14 in accordance with a given specific value of the measurement, adjustment or control unit 3b. Next, when the valve 13 is closed, the gaseous trimethylamine is guided into the measurement, regulation or control unit 3b via the open valve 15. The addition of cleaning air is made by conduit 11 and valve 12. Since the metering bellows 3a and the measuring, regulating or control unit 3b together correspond to the metering device 3 of FIG. 1, the addition of cleaning air in the second embodiment is also done directly into the metering device. .

Applicable to the core manufacturing method for metal casting process.

Claims (3)

In the method of manufacturing a sand core metal casting process, In this method, the gaseous trimethylamine is guided through the components of the metering device 3 and then guided to a concentration of 0.01 to 0.12% by weight based on the amount of sand used for coarse sugar which is brought into contact with the sand. To the core injection machine (4), where a cleaning gas is introduced before entering the gas injection machine (4) into the gaseous trimethylamine, and here the amount of cleaning gas used relative to the amount of trimethylamine (T) (L) is in the ratio of T: L from 1: 1000 to 1: 10000. The method of claim 1, The cleaning gas is introduced directly into the metering device (3). The method according to claim 1 or 2, Trimethylamine is supplied in liquid form to the metering bellows 3a forming part of the metering device 3 and then in gaseous form to measure, adjust or otherwise form part of the metering device 3. Guided through the control unit (3b).