DE102018120993A1 - Process for the gassing of molding material injected into a core box for the production of casting cores with a catalyst gas - Google Patents

Abstract

The invention relates to a method for gassing molding material (FS) shot into a core box (3) for the production of a casting core with a catalyst gas (KG) which is mixed from compressed air (DL) and a catalyst (KS). The compressed air (DL) is heated to a compressed air temperature and mixed with an overpressure (PL) before mixing. The liquid catalyst (KS) is introduced into the compressed air flow (DL) and evaporates in the process. The amount of catalyst introduced is adjusted so that the concentration KK of catalyst (KS) in the catalyst gas (KG) is below a limit concentration LEL (T). The catalyst gas (KG) is fed into the core box (3) via a gassing device (8) coupled to the core box (3). In order to achieve minimized curing times and high productivity in such a process, the invention proposes to continuously inject the catalyst (KS) as a regulated catalyst volume flow (KV) into the heated and pressurized compressed air stream (DL), at least the temperature, during the gassing (T_IST) of the catalyst gas (KG), preferably also its pressure and volume flow, before it enters the core box (3) and the catalyst volume flow (KV) injected into the respective compressed air volume flow (DL) as a function of the detected temperature ( T_IST) of the catalyst gas (KG) in such a way that KK <LEL (T) always applies to the concentration KK of the catalyst (KS) in the catalyst gas (KG).

Description

The invention relates to a method for gassing core sand, which has been shot into the core box for the production of casting cores and is present as a mixture of core sand, an organic binder and optionally added additive, the gassing being carried out with a catalyst gas consisting of compressed air and a vaporous catalyst is mixed.

So-called casting cores are used to form voids in or an outer contour on the respective casting when casting cast parts from molten metal. The casting cores are inserted into a casting mold provided for casting the casting, in order to form cavities, channels, lines and the like in the casting, or serve as external molded parts which delimit the outside of the mold cavity of the casting mold which determines the shape of the casting. The casting cores arranged inside the casting mold are generally so-called “lost cores”, which are destroyed when the casting is removed from the mold. In contrast, “permanent cores” that can be used repeatedly are used as outer molded parts and are retained when the casting is removed from the mold. In the case of cast parts that also have a complex design in the area of their outer contour, however, molds, so-called “core packages”, are also used, which are composed entirely of casting cores.

There are various processes and materials for the production of the cores. One method that is widely used is the ColdBox method (see for example DE 24 13 537 A1 ).

In this process, a molding material consisting of core sand that has been tried and tested for this purpose and a binder that is also known are mixed. A large number of designs of such binder systems are known (see, for example WO 2016/165916 A1 ). In addition, additives can optionally be added to the molding material in order to adjust its properties, such as the flow behavior, the shelf life and the like.

In the production of casting cores for the production of castings from cast iron melts, the binder system is typically isocyanate and phenolic resin, which in the casting core formed from the core sand become polyurethane and thus the cohesion of the grains of the core sand via one for pouring off the molten metal in the Ensure sufficient time for each mold.

In order to be able to process the molding material industrially, the molding material must be storable for several hours. In order to achieve rapid production nevertheless, after the cores have been formed from the molding material, their curing is reduced to a few seconds by a catalyst in gaseous form.

Amines are typically used as the catalyst here (see https://www.giessereilexikon.com/giesserei-lexikon/Encyclopedia/show/coldbox-verfahren-781/), which mixes with the compressed air serving as carrier and transport gas to form the catalyst gas become.

• - Es wird ein so genannter Kernkasten zur Verfügung gestellt, der einen den herzustellenden Kern abbildenden Formhohlraum umgrenzt.
• - Der Formstoff wird in eine über den Kernkasten gesetzte Schusshaube gegeben und mittels eines Druckluftstoßes durch Öffnungen im Kernkasten in den Hohlraum des Kernkastens geschossen.
• - Als Katalysatorgas wird ein vorerwärmtes Druckluft-Amin-Gemisch in den Kernkasten geblasen. Hierzu wird eine Begasungsplatte, die Einblasdüsen trägt und dazu eingerichtet ist, das in sie einströmende Katalysatorgas auf die Einblasdüsen zu verteilen, so auf den Kernkasten gesetzt, dass die Einblasdüsen in die Öffnungen des Kernkastens reichen und so das Katalysatorgas gezielt zu dem Formstoff bringen, der im Kernkasten ausgehärtet werden soll. Über an dem Kernkasten vorgesehene Abströmöffnungen verlässt das Katalysatorgas den Kernkasten und wird aufgefangen, um es zu entsorgen oder für eine Wiederverwendung aufzubereiten.
• - Nach der Beaufschlagung mit dem Katalysatorgas wird der Kernkasten mit erwärmter Druckluft gespült, um die dort möglicherweise verbliebenen Amine auszutreiben und um durch Wärmezufuhr den Aushärtvorgang schnell zum Abschluss zu bringen.
• - Ist die Aushärtung abgeschlossen, wird der Kernkasten geöffnet und der fertige, nun formstabile Kern kann aus dem Kernkasten entnommen werden.

The casting core production using the cold box process proceeds as follows (see https://www.giessereilexikon.com/giessereilexikon/Encyclopedia/show/kemschiessmaschine-800/):

• - A so-called core box is provided, which delimits a mold cavity that maps the core to be produced.
• - The molding material is placed in a shooting hood placed over the core box and shot into the cavity of the core box through openings in the core box by means of a compressed air blast.
• - A preheated compressed air / amine mixture is blown into the core box as the catalyst gas. For this purpose, a gassing plate, which carries injection nozzles and is set up to distribute the catalyst gas flowing into it onto the injection nozzles, is placed on the core box in such a way that the injection nozzles extend into the openings in the core box and thus bring the catalyst gas specifically to the molding material which should be cured in the core box. The catalyst gas leaves the core box via outflow openings provided on the core box and is collected in order to dispose of it or to prepare it for reuse.
• - After the catalyst gas has been applied, the core box is flushed with heated compressed air in order to drive out the amines which may be left there and to bring the curing process to a conclusion quickly by applying heat.
• - When curing is complete, the core box is opened and the finished, now dimensionally stable core can be removed from the core box.

To generate the catalyst gas, the respective amine is evaporated and mixed with the compressed air in a mixing device. For this purpose, a predosed amount of amine is, for example, placed in a mixing chamber filled with compressed air and heated there, so that the amine evaporates in the compressed air. Then that's how it works with valves formed catalyst gas led via lines to the core box. In an alternative mixing process, compressed air is passed through a continuous flow heater and amine is injected into the hot air stream. The catalyst gas thus formed from the hot compressed air and the injected amine is fed directly into the core box.

Depending on the temperature, pressure and saturation with the respective amine, air-amine mixtures can be highly explosive. Therefore, the maximum temperature to which the catalyst gas may be heated is typically limited to 120 ° C. in the conventional cold box processes.

In practice, this limitation gives rise to the problem that the amine contained in the catalyst gas as a catalyst condenses on entry into the core box, and thus no optimal flushing of the molding material contained in the core box with the catalyst which accelerates the curing of the binder contained in the molding material more guarantees is. This condensation can be so strong that larger accumulations of liquid amine form in the area of the injection nozzles, which considerably impair the penetration of the molding material with the catalyst. The consequence of this is that in practice, significantly longer cycle times are required for the curing process than would be the case with an optimal flow of the molding material with a constant gaseous catalyst. In addition, the cycle time required for gassing the core box with the catalyst gas is extended, so that significantly longer flushing times are required to drive out condensed amine from the core box than with amine kept in the gas phase.

Against this background, the task has arisen of naming a method and a device with which minimized curing times and associated high productivity can be achieved in casting core production using the cold box method.

The invention has achieved this object by the method specified in claim 1.

Advantageous embodiments of the invention are specified in the dependent claims and, like the general inventive concept, are explained in detail below.

• - die Druckluft vor der Vermischung mit dem Katalysator auf eine Drucklufttemperatur erwärmt und mit einem Überdruck beaufschlagt,
• - der in flüssiger Form bereitgestellte Katalysator in den erwärmten und druckbeaufschlagten Druckluftstrom unter Dampfbildung eingebracht,
• - die in den Druckluftstrom eingebrachte Katalysatormenge so eingestellt, dass die Konzentration KK an Katalysator in dem Katalysatorgas unterhalb einer für den jeweiligen Katalysator geltenden Grenzkonzentration UEG(T) liegt,

und

• - das so gebildete Katalysatorgas über eine Begasungseinrichtung in den Kernkasten geleitet, die zu diesem Zweck an den Kernkasten angekoppelt wird.

In accordance with the state explained at the outset, in a method according to the invention for the gassing of molding material which has been injected into a core box for the production of a casting core and is present from a mixture of a core sand, an organic binder and optionally an additive, with a catalyst gas , which is a mixture of compressed air and a catalyst,

• - the compressed air is heated to a compressed air temperature and mixed with an overpressure before it is mixed with the catalyst,
• the catalyst provided in liquid form is introduced into the heated and pressurized compressed air stream with the formation of steam,
• - The amount of catalyst introduced into the compressed air flow is adjusted so that the concentration KK of catalyst in the catalyst gas is below a limit concentration UEG (T) applicable to the respective catalyst,

and

• - The catalyst gas thus formed is passed through a gassing device in the core box, which is coupled to the core box for this purpose.

• - während der Begasung
• - der Katalysator als geregelter Katalysator-Volumenstrom in den erwärmten und druckbeaufschlagten Druckluftstrom kontinuierlich eingedüst,
• - die Temperatur des Katalysatorgases vor seinem Eintritt in den Kernkasten erfasst

und

• - der in den jeweiligen Druckluftvolumenstrom eingedüste Katalysator-Volumenstrom in Abhängigkeit von der erfassten Temperatur des Katalysatorgases derart geregelt, dass für die Konzentration KK des Katalysators in dem Katalysatorgas stets gilt KK < UEG(T).

According to the invention

• - during fumigation
• the catalyst is continuously injected into the heated and pressurized compressed air stream as a regulated volume flow of catalyst,
• - Detects the temperature of the catalyst gas before it enters the core box

and

• - The catalyst volume flow injected into the respective compressed air volume flow is regulated as a function of the detected temperature of the catalyst gas in such a way that for the concentration KK of the catalyst in the catalyst gas always applies KK <LEL (T).

According to the invention, not only is an amount of liquid catalyst available, which is sufficient for curing the amount of molding material injected into the core box, injected into the amount of compressed air to produce the catalyst gas, but the catalyst is also, at least as a function of temperature, mixed with the preheated compressed air stream. The temperature measurement takes place in the critical area between the point at which the catalyst is added and the entry into the mold cavity of the core box.

The temperature-controlled addition of the catalyst to the compressed air according to the invention ensures on the one hand that only as much catalyst liquid is always introduced into the compressed air that the critical concentration limit LEL, the so-called “lower intervention limit”, drops a potentially explosive air-catalyst mixture would certainly not be exceeded. The known temperature dependence of the concentration limit LEL is taken into account.

According to the European Directive 94/9 / EC ("ATEX"), the concentration limit LEL is determined, for example, in the context of company approvals for mixtures of substances used in an industrial environment, which may be used in an explosive environment or may even be explosive. Accordingly, they are usually in the form of concentration-temperature diagrams (see 2 ) shown concentration limits UEG for substances that are used as standard in the production of casting cores in the cold box process that are used as catalysts.

By making the addition of the catalyst dependent on the temperature according to the invention, it is always ensured, even at high temperatures, that the catalyst gas mixed according to the invention is not an explosive gas mixture. In this way, it is possible in the method according to the invention to raise the temperature of the catalyst gas significantly above the temperature limit of 120 ° C., which usually applies to core production machines used today which operate according to the cold box method. The increased temperature results in an increased effectiveness of the catalyst gas blown into the core box according to the invention and, as a result, a significantly reduced curing time.

At the same time, this ensures that, according to the invention, not only is a certain catalyst portion added to a certain volume of compressed air in one fell swoop to produce the catalyst gas, but also, during the gassing, in particular continuously, a controlled catalyst is added in the manner according to the invention, that a sufficient amount of catalyst for the hardening of the molding material gets into the core box when the concentration of the catalyst in the catalyst gas is reduced due to an elevated temperature in order not to exceed the concentration limit LEL valid for this temperature.

In addition to the addition of the catalyst, which is regulated as a function of the temperature when the catalyst gas is mixed, and the increase in the effectiveness of the curing process achieved thereby, the formation of condensate from the catalyst contained in the catalyst gas can occur in the lines leading to the core box, in the gassing device coupled to the core box, or in the core box can be avoided even in that, in addition to the temperature-controlled addition of the catalyst to the compressed air during the generation of the catalyst gas, the pressure of the catalyst gas is recorded before entering the core box and the compressed air volume flow is regulated in dependence on the detected pressure of the catalyst gas in such a way that the partial pressure of the catalyst in the catalyst gas is always below a limit pressure, above which condensation of the catalyst from the catalyst gas would occur. In order to achieve an optimally precise pressure-related control of the catalyst gas, the volume flow of the catalyst gas flowing to the core box can also be measured.

The regulation of the compressed air volume flow to avoid condensation according to the invention, in addition to the temperature-related regulation, also as a function of the pressure and the volume flow of the catalyst gas, is superimposed by the temperature-dependent regulation of the concentration of the catalyst in the catalyst gas and is interdependent with the temperature-dependent regulation. If it turns out that in order to avoid the formation of condensate, the compressed air volume flow has to be reduced in order to reduce the pressure, this would lead to an increase in the catalyst concentration in the catalyst gas with a constant, unregulated admixture of catalyst, which in turn would exceed it could result in the critical concentration limit UEG. However, since, according to the invention, the concentration of the catalyst in the catalyst gas is always set in a manner dependent on the temperature so that the concentration limit LEL is not exceeded, this effect cannot occur in the method according to the invention.

In the case of the particularly practice-relevant design, in which the composition of the catalyst gas is regulated on the one hand and its pressure as a function of temperature and pressure according to the invention, short curing times, correspondingly short cycle times and, consequently, maximized productivity during production can be carried out in a particularly reliable manner of casting cores.

The method according to the invention is characterized in particular in that the compressed air temperature of the compressed air stream mixed with the catalyst and of the catalyst gas mixed from the heated compressed air stream and the catalyst can typically be more than 120 ° C. and up to 350 ° C.

The “overpressure” is the difference between the normal pressure (= 1 bar absolute) and the actual pressure of the compressed air flow. Accordingly, 1 bar overpressure corresponds to a pressure of 2 bar absolute. The overpressure with which the compressed air stream is acted upon when it is mixed with the catalyst to the catalyst gas in the manner according to the invention is typically in the range of 1-6 bar above normal pressure.

Particularly suitable catalysts in the process according to the invention are amines from the group “dimethylethylamine (DMEA), dimethylpropylamine (DMPA), triethylamine (TEA), dimethylisopropylamine (DMIPA)”.

By heating the catalyst before it is injected into the compressed air stream, good evaporation and, as a result, good mixing with the compressed air can be ensured during the generation of the catalyst gas. At the same time, heat losses that can occur when the catalyst is mixed into the compressed air are reliably avoided. For this purpose, the temperature to which the catalyst is heated before the injection is preferably 20-250 ° C.

The manner according to the invention allows gassing core boxes which have not only one but several mold cavities for the simultaneous production of two or more casting cores to be gassed without further ado.

After the amount of catalyst sufficient for the accelerated curing has been introduced into the core box via the catalyst gas formed from it and the heated and pressurized compressed air stream, the injection of the catalyst into the compressed air stream is terminated. When the core box is subsequently flushed with compressed air, the temperature-dependent and optionally additionally pressure-dependent regulation of the compressed air flow according to the invention can be maintained, on the one hand to maintain an optimal temperature level in the core box for the rapid curing of the molding material and on the other hand to ensure that the gas mixture emerging from the core box is an uncritical one Has composition. The aeration thus carried out is expediently continued until the concentration of catalyst flushed out of the core box by means of the compressed air in the gas mixture emerging from the core box is below a limit concentration below which the catalyst no longer has an environmentally harmful effect. The gas mixture escaping until this limit value is reached is collected in a manner known per se and sent for processing or disposal.

The invention thus proposes a method for the gassing of molding material shot into a core box for the production of a casting core, which is mixed from a core sand, an organic binder and optionally an additive, with a catalyst gas present as a mixture of compressed air and a catalyst. Before the catalyst and compressed air are mixed, the compressed air is heated to a compressed air temperature and pressurized. The liquid catalyst is introduced into the heated and pressurized compressed air stream and evaporates in it. The amount of catalyst introduced is adjusted so that the concentration KK of catalyst in the catalyst gas below a limit concentration LEL (T) lies. The catalyst gas thus formed is passed into the core box via a gassing device coupled to the core box. In order to achieve minimized curing times and an associated high productivity in such a method, the invention proposes to continuously inject the catalyst as a regulated volume flow of catalyst into the heated and pressurized compressed air stream during gassing, at least the temperature of the catalyst gas, preferably also its pressure and optionally also its volume flow, to be detected before it enters the core box and the catalyst volume flow injected into the respective compressed air volume flow at least as a function of the temperature of the catalyst gas detected, preferably additionally as a function of its pressure detected and optionally of its volume flow as such regulate that for concentration KK of the catalyst in the catalyst gas always applies KK < LEL (T) ,

• 1 eine Einrichtung zum Begasen von in einen Kernkasten eingeschossenem, einen Gießkern bildenden Formstoff in einem Längsschnitt;
• 2 ein Diagramm, in dem die Konzentration eines hier als Katalysator eingesetzten Amins in einem Katalysatorgas über die Temperatur aufgetragen ist;
• 3 ein Dampfdruckdiagramm für ein als Katalysator bei der Begasung in der Einrichtung gemäß 1 eingesetztes Amin.

The invention is explained in more detail below on the basis of a drawing illustrating an exemplary embodiment. Each shows schematically:

• 1 a device for gassing molded in a core box forming a casting core in a longitudinal section;
• 2 a diagram in which the concentration of an amine used here as a catalyst in a catalyst gas is plotted against the temperature;
• 3 a vapor pressure diagram for a as a catalyst in the fumigation in the device according to 1 Amine used.

The facility 1 for gassing is provided on a conventionally designed core shooter, the details of which are not shown here for the sake of clarity. A typical example of such a core shooter is in the EP 0 128 974 A1 described.

In the core shooter, molding material is used FS , which is mixed from a conventional core sand, which has been tried and tested for this purpose, and a binder, into a mold cavity 2 an equally conventionally designed core box 3 shot. The Core box 3 has an upper core box half 4 on that on a lower core box half 5 from which he sits to open the core box 3 and take it into the core box 3 each molded core can be removed. In the top half of the box 4 are conventional injection nozzles, for example 6 for blowing catalyst gas KG intended. So are the bottom half of the box 5 also conventional venting nozzles in a likewise known manner 7 arranged over which in the core box 3 injected catalyst gas KG in the usual way as a gas mixture GA from the core box 3 is derived and disposed of or processed.

After shooting the molding material FS in the mold cavity 2 of the core box 3 is used as a fumigation facility 8th a so-called "fumigation plate" on the top of the core box 3 put on, which is designed like a hood and one to the top of the core box 3 open distribution room 9 bounded, the core box-side opening that in the upper half of the core box 4 arranged injection nozzles 6 covers. At the top of the distribution room 9 opens a supply line 10 , through which the catalyst gas during gassing KG or compressed air DL in the distribution room 9 and through the injection nozzles 6 in the molding material FS in the mold cavity 2 of the core box 3 is directed.

In the distribution room 9 are at least one temperature measurement sensor known per se for these purposes 11 and at least one pressure measurement sensor which is also known per se for these purposes 12 arranged. The temperature measuring sensor 11 and the pressure measurement sensor 12 record the respective temperature in the fumigation mode T_IST and the respective pressure P_IST the one in the distribution room 9 prevailing, through the respectively injected catalyst gas KG formed atmosphere and deliver the measured temperature and pressure values to an evaluation and control device 13 ,

The the distribution room 9 bounding walls of the fumigation facility 8th are covered with thermal insulation to prevent heat loss in the distribution room 9 injected catalyst gas KG to minimize. The thermal insulation can be combined with a heater that is designed to remove heat from the catalyst gas KG over the wall of the fumigation facility 8th to prevent the environment.

The supply line is in the same way 10 Insulated and optionally heated to ensure that the temperature is maintained by the supply line 10 flowing gases (catalyst gas KG or compressed air DL ) remains largely constant.

The supply line 10 is connected to a compressed air supply 14 connected which the with a certain overpressure PL pressurized air flow DL in the supply line 10 directs. The supply line 10 leads through a controllable heating device designed as a conventional heat exchanger 15 , of which by the supply line 10 flowing compressed air flow DL is heated to a certain temperature. The heater 15 is via a control line 16 with the evaluation and control device 13 connected.

In the direction of flow S behind the heater 15 is in the supply line 10 a control valve 17 arranged, through which the through the supply line 10 flowing compressed air flow DL is regulated. Also the control valve 17 is via a control line 18th to the evaluation and control device 13 connected.

In the direction of flow behind the control valve 17 and in front of the mouth of the supply line 10 in the distribution room 9 the fumigation facility 8th passes the supply line 10 a injection device 19 that are used to inject catalyst KS in the through the supply line 10 flowing stream of compressed air DL is trained.

The injection device points to this 19 with regard to the volume flow of catalyst that they deliver KV adjustable injectors 20th on, which can be designed in the manner of the injection nozzles known from internal combustion engines. The injectors 20th are via a control line 21 with the evaluation and control device 13 connected and via a supply line 22 to a tank 23 connected, in which the comparable fluidity with water or gasoline catalyst KS is in stock.

On the supply line 22 is an adjustable heating device 24 for heating the fumigation operation by the supply line 22 flowing catalyst volume flow KV assembled. The heater 24 is also via a control line 25th with the evaluation and control device 13 connected.

The the supply line 10 flowing compressed air flow DL is by a flow measurement sensor 26 recorded in the direction of flow S after the control valve 17 and in front of the injection device 19 in the supply line 10 is arranged. The flow measurement sensor 26 also delivers its measurement results to the evaluation and control device 13 ,

The injection device 19 injected during the gassing operation according to that of the evaluation and control device 13 to them transmitted control signals set catalyst volume flow KV into which the injection device 19 passing compressed air flow DL so that from the compressed air flow DL and the catalyst injected into it KS the catalyst gas KG is formed in the direction of flow S after the injection device 19 in the supply line 10 to the distribution room 9 the fumigation facility 8th flows. Heating the catalyst KS is carried out so that it is injected by the catalyst KS in the compressed air flow DL when entering the compressed air flow DL completely evaporated and there was no significant temperature change compared to the temperature of the injector 19 incoming compressed air flow DL comes, so the temperature of the in the distribution room 9 inflowing catalyst gas KG equal to the temperature of the compressed air flow DL is.

For the binder that is in the molding material FS is mixed in, it is for example phenolic resin and isocyanate. As a catalyst KS to accelerate the curing process of the molding material FS in the mold cavity 2 of the core box 3 commercial dimethylpropylamine (“DMPA”) C ₅ H ₁₃ N is used.

For the catalyst KS is the limit concentration dependent on temperature and pressure in a manner known per se in accordance with the ATEX regulations LEL (T) have been determined from which an explosive mixture of catalyst KS and there is air. The temperature-dependent limit concentration is also OEG (T) have been determined, when exceeded the air so strongly with catalyst KS is saturated that there is no longer any risk of explosion. The limit concentration OEG (T) does not matter here since it is at such high concentrations KK of catalyst KS in which from the compressed air DL and the catalyst KS formed catalyst gas KG massive condensate formation in the gassing device 8th or in the core box 3 would come. The result of the determination of the limit concentrations LEL (T) and OEG (T) is in 2 represented schematically as a diagram. The limit concentrations LEL (T) and OEG (T) thus limit the range in which the concentrations depend on the respective temperature KK of the catalyst KS in the compressed air flow DL lie where an ignitable, from the compressed air flow DL and the catalyst KS mixed catalyst gas KG would exist and as such must not be reached.

In 3 the vapor pressure diagram applicable to DMPA is reproduced, which is usually provided by the manufacturer or created in the laboratory. The temperature-dependent critical vapor pressure is derived from the vapor pressure diagram PG when it is exceeded, the previously gaseous DMPA passes into the liquid phase.

The course of the critical limit concentration LEL (T) and the course of the limit pressure PG are in data processing form in the evaluation and control device 13 stored as process parameters.

Accordingly, there is an overpressure of 1-3 bar, ie a pressure P , which is 1 - 3 bar above normal pressure NP (= 1 bar) lies in the temperature range of approx. 87 ° C (1 bar overpressure) to 115 ° C (3 bar overpressure) in the compressed air flow DL as a catalyst KS injected and evaporated in it, DMPA certainly still in the gas phase. The area in question is in 3 highlighted by hatching.

Before the start of fumigation operation, the compressed air supply 14 Compressed air initially supplied in a certain volume flow DL when flowing through the heating device 15 heated to 180 - 190 ° C, for example, and into the distribution room 9 the fumigation facility 8th directed. If necessary, the volume flow supplied is readjusted in the following process sequence, for example in order to avoid flow losses which can be caused by contaminations that occur in the area of the injection nozzles 6 attach to avoid.

The temperature measuring sensor 11 records the actual temperature T_IST the one in the distribution room 9 incoming compressed air DL and reports this to the evaluation and control device 13 , At the same time, the pressure measurement sensor detects 12 the actual pressure P_IST the one in the distribution room 9 through the compressed air DL formed atmosphere and reports this to the evaluation and control device 13 , This arranges taking into account the course of the critical limit concentration stored in it LEL (T) and taking into account the course of the critical limit pressure that is also stored in it PG the temperature T_IST and the pressure PG one into the compressed air DL catalyst volume flow to be injected KV to which, on the one hand, it is ensured that the resulting concentration K_IST of catalyst KS in the catalyst gas KG below that of the respective temperature T_IST assigned critical limit concentration LEL (T) is on the other hand and is set so that the partial pressure of the catalyst KS in the catalyst gas KG is within a range in which the critical limit pressure PG is not exceeded, thus ensuring that the catalyst KS is vaporous.

Is that in the distribution room 9 detected pressure P_IST so high that the risk of exceeding the critical limit pressure PG there is, the evaluation and control device 13 a control signal the control valve 17 , which is then the flow cross section of the supply line 10 narrowed accordingly until that of the flow measurement sensor 26 detected compressed air flow DL corresponds to the target specification and, with it, the pressure P_IST has reached a value at which a distance to the limit pressure reliably precludes the formation of condensate PG consists. At the same time, the evaluation and control device 13 Control signals to the injectors 20th to the in the compressed air flow DL injected catalyst volume flow KV reduce so far that the concentration of catalyst KS in the catalyst gas KG despite the reduced compressed air flow DL safely below the critical limit concentration LEL (T) lies.

Fumigation is carried out until one for accelerated curing of the in the mold cavity 2 of the core box 3 contained molding material FS sufficient amount of catalyst gas KG through the core box 3 is headed. Then the mold cavity 2 with pure compressed air DL rinsed to in the molding material FS residues of the catalyst still present KS from the mold cavity 2 to drive out. The temperature, pressure and optionally volume-dependent control of the compressed air flow DL continued to make sure that the core box 3 escaping gas mixture GA an uncritical mixture of compressed air DL and from the core box 3 flushed catalyst KS forms. At the same time, the temperature in the core box is maintained during the rinsing 3 blown compressed air DL the temperature of the in the core box 3 contained molding material FS kept at a level favorable for its accelerated curing. The compressed air purging continues until the concentration of catalyst KS in the exiting gas mixture GA falls below a limit, reaching which means that no volatile catalyst KS more from the core box in quantities that are harmful to health or the environment 3 and the molding material contained in it FS exit.

The one in the mold cavity 2 of the core box 3 accelerates hardened molding material FS forms a casting core which, for example when casting an engine block (not shown here) for an internal combustion engine from an iron casting material, forms a water jacket or a comparable cavity in the engine block casting. With the procedure according to the invention, it is possible to produce particularly large casting cores safely and in high quality, as are required, for example, for casting heavy truck engines and the like in series operation.

Reference list

1

Fumigation facility

2

Mold cavity

3

Core box

4

upper core box half

5

lower core box half

6

Injection nozzles

7

Ventilation nozzles

8th

Fumigation facility (fumigation panel)

9

Distribution room

10

supply line

11

Temperature measuring sensor

12th

Pressure measuring sensor

13

Evaluation and control device

14

Compressed air supply

15

Heating device

16

Control line

17

Control valve

18th

Control line

19

Injection device

20th

Injectors

21

Control line

22

supply line

23

tank

24

Heating device

25

Control line

26

Flow measurement sensor

DL

Compressed air / compressed air flow

FS

Molding material

GA

from the core box 3 escaping gas mixture

K_IST

Actual concentration of the catalyst KS in the catalyst gas KG

KG

Catalyst gas

KK

Concentration of the catalyst in the catalyst gas KG

KS

catalyst

KV

Catalyst volume flow

NP

Normal pressure (= 1 bar)

P

print

P_IST

Actual pressure in the distribution room 9

PG

critical vapor pressure

PL

Overpressure

S

Direction of flow of the compressed air flow DL and the catalyst gas KG

T_IST

Actual temperature in the distribution room 9

LEL (T)

lower limit concentration

OEG (T)

upper limit concentration

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 2413537 A1 [0003]
• WO 2016/165916 A1 [0004]
• EP 0128974 A1 [0033]

Claims (9)

Process for the gassing of molding material (FS), which has been shot into a core box (3) for the production of a casting core and which consists of a mixture of a core sand, an organic binder and optionally an additive, with a catalyst gas (KG), which as Mixture of compressed air (DL) and a catalyst (KS) is present, - the compressed air (DL) being heated to a compressed air temperature before being mixed with the catalyst (KS) and subjected to an excess pressure (PL), - the liquid form The catalyst (KS) provided is introduced into the heated and pressurized compressed air stream (DL) with the formation of steam, - the amount of catalyst introduced into the compressed air stream (DL) being adjusted so that the concentration KK of catalyst (KS) in the catalyst gas (KG) is below a limit concentration LEL (T) applicable to the respective catalyst (KS), and - the catalyst gas (KG) thus formed via a gassing device ung (8) in the core box (3), which is coupled to the core box (3), characterized in that during the gassing - the catalyst (KS) as a regulated catalyst volume flow (KV) in the heated and pressurized compressed air stream (DL) is injected continuously, - the temperature (T_IST) of the catalyst gas (KG) is recorded before it enters the core box (3) and - the catalyst volume flow (KV) injected into the respective compressed air volume flow (DL) is dependent on the temperature (T_IST) of the catalyst gas (KG) is regulated in such a way that KK <LEL (T) always applies to the concentration KK of the catalyst (KS) in the catalyst gas (KG). Procedure according to Claim 1 , characterized in that in addition the pressure (P_IST) of the catalyst gas (KG) is recorded before entering the core box (3) and the compressed air volume flow (DL) is regulated as a function of the detected pressure (P_IST) of the catalyst gas (KG) in such a way that the partial pressure of the catalyst (KS) in the catalyst gas (KG) is always below a limit pressure (PG), which, if exceeded, would result in the condensation of catalyst (KS) from the catalyst gas (KG). Procedure according to Claim 2 , characterized in that the volume flow of the catalyst gas (KG) flowing to the core box (3) is also measured. Method according to one of the preceding claims, characterized in that the compressed air temperature is> 120-350 ° C. Method according to one of the preceding claims, characterized in that the overpressure (PL) with which the compressed air stream (DL) is acted upon is 1-6 bar above the normal pressure. Method according to one of the preceding claims, characterized in that the catalyst (KS) is an amine from the group "dimethylethylamine (DMEA), dimethylpropylamine (DMPA), triethylamine (TEA), dimethylisopropylamine (DMIPA)". Method according to one of the preceding claims, characterized in that the catalyst (KS) is heated before being injected into the compressed air stream (DL). Method according to one of the preceding claims, characterized in that the temperature to which the catalyst (KS) is heated before the injection is 20-250 ° C. Method according to one of the preceding claims, characterized in that after the end of the injection of the catalyst (KS) into the compressed air volume flow (DL) the compressed air volume flow (DL) is maintained until the concentration of the catalyst (KS) in the core box (3) escaping gas flow (GA) is below a limit.

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